Lee McCormack's Guide to Bike Set-Up

Dec 27, 2018
by Lee McCormack  

When it comes to mountain bike setup, the most important measurement is the distance between your bottom bracket and your grips. I call this the Rider Area Distance (RAD).

We want your bike RAD to fit your body’s size and proportions. When your RAD is dialed, two great things happen:

1. You have optimal arm range for bike handling: descending, braking, cornering, pumping, dropping and all the fun stuff, and

2. You can generate maximum torque for power moves: sprinting, steep climbing, pumping, manualing, hopping and wheelie drops.

While RAD seemed like my own brilliant idea, other people have been thinking this way.

bigquotesQ: Shouldn’t we be measuring bikes in a different way? For instance from pedals to grips?

A: That’s how Sam Hill measures his bike, he gets on any bike, no point telling him any numbers, he just gets a tape measure and measures feet to bars, and if it makes sense, then he’s happy, and away he goes. I do think that’s the only true measurement you can work off.

– Ali Beckett, mountain bike designer, in International Mountain Bike Magazine

Sam Hill piloting his custom Blueberry 2018 Nukeproof Mega.

In this video post on Pinkbike, the crew at Vorsprung Suspension calls RAD “spread.”

bigquotes“This is what really determines how big your bike feels. How spread out you are between your hands and your feet.”


That’s pretty rad.

What exactly is RAD?

RAD is the hypotenuse of a triangle whose other two sides are the reach and stack of your entire cockpit, from the bottom bracket to your grips.

The components of RAD are:

• Frame reach

• Frame stack

• Height of spacers under your stem

• Tallness of your stem’s steerer clamp

• Handlebar rise

• Handlebar setback. This is probably a new term for you. Setback is the horizontal distance from the stem clamp to the grip. Someday we’ll all know the setbacks of our handlebars.


Finding your ideal bike RAD

Your ideal bike RAD is determined by your body’s size and proportions, as well as your handlebar width, crank length, pedal thickness, shoe thickness, phase of the moon and, by extension, the grunion run.

My book Dialed and site www.llbmtb.com provide several ways to determine your optimal RAD and calculate your ideal bike setup.

Dialed: The secret math of the perfect mountain bike setup.

Here are two more methods:

1. If you love your current bike, measure its RAD. When you shop for a new bike, try to match that number.

2. Use a simple multiplier. The multipliers below assume average proportions, sweet spot handlebar width, height-appropriate crank length, and average pedal and shoe thickness. While these recommendations are not gospel, they are good starting points for most people.

If you’re male, multiply your height in centimeters by 4.47

If you’re female, multiply your height in centimeters by 4.60

At 174 cm tall I get a RAD of 778mm. My bikes are within a few millimeters of this number.

Warning: These multipliers will give you shorter RADs than you typically find on fashionable bikes. Bikes have gotten longer but people haven’t.

Adjusting your RAD

Q: How close to perfect does RAD have to be?

A: The closer the better.

We can of course ride a wide range of bike setups (we’ve been doing it for years). As your bike RAD gets closer to ideal for you, your bike will start to feel better. When you get to the last 10mm, then the last 5mm, then to perfect, something clicks. Your bike just feels right. You climb technical trails easier and shred technical downhills harder.

When bike RAD is too long, you reduce torque and reduce control. I've set up about 1,000 riders, and 95% of their bikes had too much RAD. Most riders don't know any better.

When bike RAD is too short, you reduce torque and increase control (to a point). Some downhill and freestyle riders, who need more range of motion than peak sprint power, have RADs that are “too short.” This is common among tall riders. When it comes to RAD, a bit too short is much better than a bit too long.

You can adjust your bike’s RAD in a few ways:

Reach. Change the stem length or use a handlebar with different setback.

When Specialized sent me a medium 2017 Enduro Öhlins Coil (thank you!), it was 20mm longer than my last medium bike. A SQLab 30X handlebar has extra backsweep and setback, which shortens the cockpit and makes the bike fit perfectly.

Stack. Move spacers above or below your stem. Change to a stem with different rise. Try a handlebar with different rise.

Frame size. This is the last resort. These days, as frame reaches get longer, many riders should consider a smaller size. By the way, it makes sense to measure before you buy.

If your frame is the correct size and your RAD is perfect, your bike will handle great.

That said, you can dial in your bike even more by adjusting the angle of your RAD relative to level. I call this your Rider Area Angle in Degrees (RAAD). We’ll talk about that next time.

I hope this is helpful.

Lee

- - - - - - - - - - - - - - - - - - - - - -

I’m Lee, and I Like Bikes. Over the years I’ve written 10 mountain bike books, built a bunch of pump tracks, taught thousands of riders, invented RipRow and devised the RideLogic bike setup system. Thanks to the knowledge I’ve discovered for the mountain bike community, I’m riding better — and having more fun — than ever.

Learn more at
www.leelikesbikes.com
www.llbmtb.com
www.riprow.com


268 Comments

  • + 99
 You need an angle. You need an angle. Can I say that again - you need an angle to define that point in space above the bottom bracket.

You could ride a unicycle on your tip toes with the correct "RAD" otherwise. Maybe that is the new trend - high - short - steep? the new DOWNCOUNTRY.....................

Sure given that you are running a fork with relatively close dimensions and wheel size that will make it close - you need an angle...............
  • + 37
 Exactly! Without angle that RAD is just a number. Like true TT length. Pointless.
  • + 5
 @pakleni: Agreed. It's another useful number but needs other numbers like HA, ESTA, CS and WB to paint the full picture.
  • + 13
 Can we throw in bar width? If I have wide bars my reach is shorter then when I have narrow bars. Or is this all assuming we know what bar size is correct for each specific ride and don’t change that variable. But then again different bar widths work on different bike setups.
  • + 7
 Precisely. When I’m comparing bikes myself I just take the Reach and Stack and calculate this RAD bollox myself. Heard it so many times that the only measurement that matters is the downtube or RAD, whatever. It just isn’t true. Every measurement matters and if you only look at the downtube you’re missing some pretty big factors of the bikes fit and characteristics.
  • + 43
 Today is april fools in spain. Just saying
  • + 2
 @iqbal-achieve: I always take reach and stack to calculate the bb to head tube length. Since everyone is using pretty much the same forks, cranks and stems; everyone knows their preferred bar and bar width, and pretty much all bikes of a genre have the same head angle and head tube length, you don't need an angle. Regardless of bike, the angle is going to be as close as makes no difference between bikes and if it's not it can be easily altered using a couple of headset spacers.
One could comment that "it could be an penny farthing or an aero road bike" but it won't be will it? Not if you're buying a mountain bike at least. Personally I try to set my bikes up so I get good back extension and can recruit my upper body when I sprint. That means I set my road bike up with a very similar bb to grips measurement to my mountain bike.
  • + 3
 @jaame: I’m doing the same thing you do but I differ in that I do think there’s enough difference in bb heights, head tube lengths etc to warrant getting an idea of the RAD angle. Of course you can use spacers etc but then you alter the reach - which leads me to what was my real point - that you can’t look at one measurement. This is just dumbing down a comprehensive list of figures. There’s nothing I can get from this RAD figure that a proper geo chart doesn’t already tell me, plus a load more info. To me saying you don’t need an angle is like saying the there’s no need to have an accurate number in the first place as if +/- 10mm is close enough. Then why bother in the first place?
  • + 1
 Agreed, not to mention this doesn’t take into account weight on the front wheel as a result of stem length
  • + 5
 Once thought I've seen it all but day after day stupidity keeps me on my toes, wtf is this shit now? That line can be anywhere from near vertical down to horizontal and won't change a thing?
Ffs!
  • + 7
 RAD IS Lee’s angle...
  • + 9
 as SAM HILL says, " all l need is that happy place for me hands and feet, the rest l don't care much about"
  • + 1
 Literally don’t know why that replied 4 times, the website glitched. @poozank:
  • + 14
 "That said, you can dial in your bike even more by adjusting the angle of your RAD relative to level. I call this your Rider Area Angle in Degrees (RAAD). We’ll talk about that next time."
  • + 1
 This feels like a janky way of measuring reach... but easy to market to people
  • + 3
 Interesting. I’ve ran the same numbers on my bike set ups for decades and according to lee’s rad i’m literally just a few millimeters off.
  • + 3
 Nothing beats trying enough bikes on your terrain to work out the sizing you need. Once you've worked out the reach and stack you prefer, you may as well tattoo them on your arm because they'll remain a constant. Formulas like the above are highly inaccurate as leg to torso ratios and ape indexes differ between people of the same height by significant amounts.
  • + 2
 @fullbug: me too. And my bike is a size bigger than recommended.

I bought the book, it's really good. I'm recommending it to my LBS, who does more roadie stuff than MTB.
  • + 16
 Please read the last paragraph of this story:

"That said, you can dial in your bike even more by adjusting the angle of your RAD relative to level. I call this your Rider Area Angle in Degrees (RAAD). We’ll talk about that next time."
  • + 2
 @radude: I get so RAD during my ride......
  • + 1
 @leelikesbikes: despite my criticism above I actually think what you’re doing here is pretty cool. I’ve taken issue in the past to people misguidedly using the downtube alone and touting it as the ‘only true measurement’ and other such generalisations. My comments weren’t aimed at you, just my frustrations at those previous interactions and a perspective from a rider who has a very clear idea of how I want the shape of my bike - possibly not your target audience.
I can’t speak for everyone but please keep it up and pls ignore me tup
  • + 12
 pick an arbitrary geometry measurement and be a dick about it... ETT ftw
  • + 4
 @adespotoskyli: Funny. I read the article on bar width a while back and forgot who it was from. Thinking that I could benefit from calculating it for my height. So, link on this article and I go to the page, run the numbers (6.5 or 1841mm') and apparently I should be using an 810 bar??? WTF nonsense is this? can you even buy an 810?
I call bullshit on the bar widthmagic, and this will go right along with it.
  • + 0
 @Poulsbojohnny: Yeah, some brands are making 810's.Go on CRC and filter the width to 810.
  • - 2
 @Poulsbojohnny: Enve makes one. I know because I own one! lol I have cut it to 795 however. I am 6'2"and that calculation told me 827mm was my sweet spot. LMFAO! that calculation is beyond useless, and by default so is anything the person that came up with it says!
  • + 0
 @Poulsbojohnny: Race Face makes 820mm bars.

The article about handlebars made it pretty clear the measurements were simply a guide based on an ideal size for average proportions. He specifically addressed taller riders and said they would likely need to go smaller and listed some benefits of using a smaller bar for everyone.
  • + 2
 @Motoracer31: Funny because I always thought reach was a janky way of measuring an imaginary line that is affected by other factors. At least with a measurement from bb to top of head tube it cannot change since it is an actual fixed measurement. For me, that is a much better starting place than "reach" and "stack". Why anyone ever thought they were a good idea is beyond me. Better than ETT I guess, but not much.
  • + 1
 @iqbal-achieve: I know what you're saying and I agree there are many factors to consider. What I was meaning was that the length measurement is the most important thing to consider to make sure your frame fits your body. That is the first thing I look at because it's the only thing in the list of variables that is not changeable. The other parts are for fine tuning. I know for example, I am going to use a fox 36 170. I am always going to use a zero stack cane creek headset and Spank cockpit, 770mm bar. I might change stem length depending on frame length. As for a 10mm difference in bb to bar height, I believe the body will quickly get used to it. There will be an optimal distance between feet and hands in biomechanical terms, and my body will be best suited to do work in this range because of the actual size of my skeleton. The angle of feet to hands does not affect that length though. They are my thoughts, what are your thoughts?
  • + 1
 @jaame: I hear ya dude. You’re making sense for sure. I think maybe we are approaching the idea with slightly different goals...I’m a little less concerned with the ‘fit’ as it were and more concerned with how my body shape will work with that of the bike. I realise they may be the same thing..! But what I mean is that I’m looking at specific ways in which the geometry will help me to get different things from the bike depending on what I plan to do with it. While I’ve ridden lengths from 360 to 460 reach I’ve never felt under powered or hindered in any way for straight up riding duties on anything within that range, I have definitely felt that certain bikes have been easier to jump or easier to keep planted in corners, etc, etc and I believe that to be more about the shape and the angle of the BB to bar relationship than necessarily the spread of the two. To try and put it bluntly I’m more interested in whether I’ll be able to manual it than whether I’ll be in optimal position to kill a couple hundred meters ascent and for me to figure that out I need the angle. But a large factor here is that I am short and therefore relatively light. And more and more I’m realising that the way I interact with bikes is not always the same as riders of more average sizes. So perhaps those nuances with stack and this RAD angle have greater potential to alter the way my bike rides?
Don’t get me wrong, the size is a major factor but is almost secondarily relatable to the shape of the bike for me.
Perhaps I just over think everything? But that’s surely not true Razz
And to be fair, bringing it back to the points you made the biggest changes in this angle have often (not always) been when moving from a trail bike, to enduro, to downhill or vice versa. Within the same categories there can be assumptions made about similarities I suppose tup
  • + 2
 @iqbal-achieve: Cool. I think what I try to do is to set my bike up at the length that I feel I am making good power in deadlift. Kind of like, when I am doing a power wheelie, I want the distance from my foot at the bottom of the stroke to be the same distance from the bar that my foot would be from the bar when I'm doing a deadlift. Strange but true!

Whereas you're setting yours up to manual. Interesting. In that case, I can understand why your angle from bb to bar would be more important. For me, that angle is less important. I still love to manual, but I am trying to get the most power I can from my body.
  • + 3
 @leelikesbikes: you are asking way too much. We have to read the entire thing?
  • + 3
 Sorry! I try so hard to make these posts simple and short. Smile
  • + 3
 I could give you the recommended angles from Lee's fitting guide if you are so desperate that you can't wait for the promised next article covering it. But I won't. What do you want a recommended angle for? Just go ride and see what feels better. I can tell you that the RAD angle I currently have on my 170/170mm enduro bike corresponds to Lee's cross country recommendation. I run a 13mm rise handlebar on a zero rise stem with no spacers. I have tried the recommended higher positions but having come from 26" wheels, I find that the lower the better. The only way I could increase this angle while maintaining the same bar height would be to decrease the reach, which I won't because it feels fine and is also within Lee's recommendation. I should also mention that my recommended RAD is 3% higher than the one resulting from the 4.47 number, because it takes other body measurements into consideration. But to sum it up: an ideal RAD will give you the best fit to the bike. There is not an ideal angle, only an ideal RAD which is valid independently of angle.
  • + 2
 @DavidGuerra: Thank you Sir. The calculations on the site are more accurate than the simple multiplier I put in this post.
  • + 1
 @poozank: With the same lenght stem you can have dramatically differently loaded front wheel, as you are not loading front end with arms only.
  • + 3
 He does mention the angle; RAAD Rider Area Angle in Degrees. This is way too in depth of a topic for this short of an article. It’s why he wrote a book about it I think.
  • + 1
 @fattyheadshok: Yeah it's about 10x as complex (and not as accurate) as working out your own reach and stack numbers from riding bikes.
  • + 4
 Seeing that bike manufacturers are all working with a relatively consistent set of criteria for the shape of a bike, the chances of the angle being absolutely unusable is minimal. So granting that we aren't trying to ride face down recumbents, the RAD is a good number to start with. It's all about prioritizing what needs to be addressed first, then fine tuning.

Nice job on this book @leelikesbikes I've recommended it to many people I teach and in the industry.
  • + 1
 @Poulsbojohnny: Loaded Precision 840's. Love em. And I'm only 6'4"
  • + 0
 Wont you have a lot of angles for all your different bikes? (My BMX and Enduro bike measure closer than you'd think, but v. different angles) I think what he calls the RAD is basically what you need to be comfortable, but depending on the type of bike you are building the angles could be very different. I get that RAD alone can't tell you whether to buy a L or XL frame, but, as long as you are willing to use a little common sense about how many headset spacers are reasonable, you will get there.
  • + 63
 Dear Pinkbike,
Is it too much to ask that you identify upfront whether content is PB created, PB advertorial, paid advertorial or just plain advertising? This way I wouldn't be wondering what the heck I was reading and why I was reading it...such as in not very clear but clearly product phishing articles like this one.

There might be something to this but this article explores the uncanny valley between content and clickbait far too much for my liking...

Kind regards
Me
  • + 17
 It says “User Generated” above the title. If it was sponsored it would say. Lee mentioned in RC’s post a week or so back that he was working on something to help people with what he feels to be a good method of sizing your bike. This is it.
  • + 29
 I did not get paid to create this post, nor did I pay for the placement.
  • + 6
 Agreed - when the 'article' is by a person selling something (books, in this case) and contains links to buy said something, it's an ad.
  • + 0
 @NateForrest: Infomercial plus Lee gives you much of what you need to know in the article without cost.
  • + 39
 @paulskibum: I'm going to sound old, but:

Back in the day, content was content and ads were ads. In the newspaper where I worked, there was no contact between the editorial people and the ad people. It wasn’t allowed.

Writers/photographers/artists were paid to create content. Since they were being paid for their work, they were able to report the news or express views without needing to include commercial messages.

These days, content is disposable and generally not paid for. I get the sense Pinkbike is doing well financially, but having to pay professional rates for all of their content would be prohibitive.

Given Pinkbike’s reach, I’d expect at least $1 per word plus more for art, so this post would cost Pinkbike $1,500 to $2,000. When I write for Bicyling Magazine, for example, I get paid for the content, and there is no commercial message.

So on sites like this you have people like me (and all the bike companies) who are willing to create content, with the agreement that we can further our financial agenda. The smart content creators provide tons of value, so plenty of people enjoy the content and get exposed to the message. Example: Commencal makes some great videos! I know they’re selling bikes, but that’s OK because they’re giving me some stoke. That’s the tradeoff.

If people don’t want their content mixed with commercial messages, they can always pay subscription fees. $100 per year to read Pinkbike. All content creators get paid. Ads are ads. I don’t see that happening unless society crumbles and we rebuild anew.
  • + 13
 @leelikesbikes: If that happened, the average age of readership would increase by about 20 years
  • + 4
 @jaame: Well said.
  • + 5
 @leelikesbikes: Yeah Dude...people can't/won't get over the fact that nobody does anything for free...when they finally do realize, life gets easier browsing content. Give me a little something while offering "more"...all good. That something can simply be entertainment or useful info.
In other news..."unless society crumbles and we rebuild anew."...you say that like it isn't already happening, full speed ahead Smile Humans are in a race to see who can die last with the most money&trinkets. Morons.
  • + 3
 @leelikesbikes: outstanding response, Lee. I remember the old days of newspapers too. And recognise they are gone...much like 26" bikes sadly.

I understand roughly how PB works and indeed where most of its content comes from... especially the company edits.

However, in the case of an article such as yours...it's not quite so clear. A large chunk of user generated content here is travel logs and local event roundups - mostly nothing that's overtly commercial in aim. Yours is clearly not one of these.

And yet it's one of those technique/setup/ride skills posts that a site like this sorely needs on a routine basis in order for riders to develop knowledge and understanding of riding that they can use to improve their skills on the bike.
My issue with this particular piece of content was that, as written, the aim of the piece wasn't clear from the get go. Was it a gift of content? Was it a teaser for a commercial product? Was it shameless self promotion? Or was it a mix of all three? Ultimately, these are rhetorical questions.

My preference for PBs user generated content would be for both PB and the content creator to be up front and honest about their content and why they are sharing it with the PB community...and what they'd like in return...be it clicks, kudos or coin.
  • + 49
 Ah yeah sweet. So my old bikes with way too short of a reach just need a 80mm rise bar.

What a bunch of jibberish. While I do think the addition of spread to the geometry sheet makes sense, isolated it’s simply not enough. Just taking things like weight distribution in as well as different riding styles. Personally I like short bikes cause they manual easy. Also I like long bikes because they’re mine stable descenders. But hey, he wrote 10 books, so he probably knows better.
  • + 7
 ^ this
  • + 50
 42
  • + 1
 ...Translated into letters is DB
  • + 47
 who wants a Leo Kokkonen vs Lee McCormack podcast discussion?
  • + 1
 It will happen. In some form.
  • + 3
 @reds: essentially, I think the fundamental difference is seeking stability, at the expense of power. (Leo) isnt wrong about that. Lee is also not wrong, that a rider should ride a bike that they can be powerful on. It's about priorities really. People who are going to gravitate to Leo's camp, are people who go much, much fast than your typical reacreational mtber

Even the leverages front to rear, are actually similar.
  • + 1
 Would be very interesting!
  • + 1
 I want a Pole for my next bike. I might hate it. I want to try it for myself.
  • + 3
 @ljfran2383: i think you have a good point there, but i am not so sure that faster riders will gravitate to leos camp. Slow riders do not care about power, they do mostly not even know about the continuum of pump. I rode a long bike for some time and did not like it at all, for one reason. In situations were you really have to weight one wheel i struggled to do so. It is also interesting how people who push the longer slacker trend are built. The geometron guy and finish people in general are big and heavy, they might not struggle creating enough power or pump. Lee is smaller than me and would recommend a bike much smaller than the one i ride. Maybe both camps should look more closely were the other one is coming from.
  • + 7
 That would be cool. I agree with Leo on all matters of bike dynamics. He's the expert there. I like to think I'm an expert on body dynamics, which had been my focus. Leo and I come from different angles, and I think that creates interesting contrast. The perfect answer is surely somewhere in the middle!!
  • + 1
 @optimumnotmaximum:

Same here....I tried the new super slack and super long bikes (not a Pole though) and didn’t come to terms with them. When I was riding downhills all day long I found it more and more difficult to put enough weight on the front wheel....when I was getting tired I had just too many washouts ....these bikes may work for some but not for me...
  • + 36
 I've just measured my bike and it it's about 100mm over what it should be so do I sell the bike I've been riding for 4 years or just turn the The stem round and fit the bars behind the fork.????????
  • + 15
 Put your hands on backwards.
  • + 4
 Run longer cranks and make sure to put all your weight on your lead pedal.
  • + 7
 Switch to drop bars.
  • + 3
 HGH, but only in your forearms..
  • + 9
 The actual problem might be your hands. Have you considered cutting 10 cms. off of your fingers?
  • + 1
 Your bike is fine. Its just that you're a wallaby.
  • + 21
 It's 11:57 PM on a work night and this freaking article makes me want to get out of bed and measure every freaking bike in my garage.
  • + 8
 I did.

And my bike is 2mm out.

Well, the only thing I have to say about that is....rad?.
  • + 3
 When I went from 26 to 29er, I measured this way, not because of this system, but the front ends were so high. I measured the 26 and dropped spacers and went with a negative stems. I have 2, 29er's different stem lengths, but the cockpit is the same size as the 26er. I can swap bikes and they feel the same, set up wise.
  • + 18
 Fwiw, founds Lee's MTB book pretty darn useful when I started MTB. So much so I passed it on and recommended to a few people. The stuff made sense.

To me the dude is worth listening and trying out his recommendations.

Btw, the measurements from 4.47 are pretty close to what I have on my current bikes. And the prior handlebar ROM article was pretty close too.

"light hands heavy feet" I'll never forget this
  • + 7
 Yes! Light hands, heavy feet, floating spirit!
  • + 3
 Agreed. Lee is a really innovative thinker in the mountain bike world, and has made a big difference in my riding. I'm still a hack, but less of hack because of Lee. I wish I had dialed in RAD two bikes ago. It would have saved me time, headaches, and $$$.
  • + 13
 Interested to read more about RAAD. As an extreme example, inverse the numbers for Reach and Stack from any given bike and you'll get whack geometry but the same hypotenuse. As a more likely example, shorter Reach and higher Stack will give the same RAD but a more upright sensation.
  • + 1
 Lee has RAAD guidelines for exactly this. I have played around with changing the angle and it is surprising was a small (1°) has a change in how your bike feels.
  • + 8
 This bike fitting system works phenomenally well once you have a number that works for you. Following the mathematical formula is not as ideal as measuring from a bike that you are really siked on. Lee has a video on his website that goes through how to adjust your stem/bar while set up on a couple of picnic tables, and once this is done, it is easy to take measurements off your bike and extrapolate out to other bikes that you are considering in the future. Lee has been living and breathing bikes for a long time and he did not come up with this over night. He has been observing and studying and dreaming this up for years. Having an open mind is also pretty helpful in general.
  • + 0
 There is a thing called soooo open-minded that your brain falls out
  • + 6
 How can this have any validity with progressive geo bikes like Pole, Nicholai, Mondraker, etc? This seems to indicate that any bike with long reach numbers are inferior fitting bikes when in fact they are absolute game changers in the positive! I love my Pole Evolink 140 but the RAD is long by 300mm! I feel like this is an antiquated means of measuring bike fit...
  • + 6
 Maybe it would be good idea to properly describe the way you should measure this, most people who got completely wrong numbers are measuring distance from crank bolt to the center of handlebar end. Obviously somewhere in the comments the author himself stated you should be measuring something like 2D projected grip position which typically lies above stem and between steerer clamp and handlebar clamp. Why would you not use something that can be measured quickly and accurately (like the method Chris Porter suggests) and come up with another measurement that is projected instead, I sure as hell don´t know, we already have one measurement that is close to impossible to measure at home, it´s called reach, no need for another if you can get the very same effect by measuring to handlebar end instead with very high accuracy and repeatability.
  • + 8
 So what you are saying is CRAP - Current Reach Application Pointless... I mean come on, the 80s called and want their acronym back.
  • + 6
 I'm 195cm tall so my 'RAD' according to this would be 872mm...

I've just bought an XXL Transition Sentinel with a reach of 515mm so that means by stack has to become 704mm.

Anyone know if you can buy a 300mm dropper yet?
  • + 3
 Aye, to go with my 100mm rise bars!

What am I not understanding here?
  • + 4
 @jenksy I'm in the same boat, only slightly shorter at 862mm. I guess RAD is meant for short people.
  • + 1
 Same here. I am 196cm, and according to this RAD formula, my Canyon Spectral, which has a respectable Stack of 644mm for an XL, would require a Reach of 595mm!! I will stick to my 480mm Reach, which feels perfectly fine.
  • + 6
 RAD is the measurement from BB to handlebar grips. You are trying to apply the RAD calculation to the frame. As Lee mentions in the article you are adding spacers, a stem, and a handle bar that has rise and sweep. Your RAD measurement will be longer than the hypotenuse of your frames reach and stack. That is unless you go to extreme measures with your handlebar.
  • + 2
 To be fair, the author does say that short RADs are common for taller people. It's just an estimate that lumps reach and stack together, and as @Primoz points out, has little relevance for seated fit. Did you measure your XXL? What was number? I'm 183cm (RAD projection of 818mm), and my large 5010.2 measures 780mm. This means that I'm a freestyle rider that can't generate torque! Given its overall dimensions, I'd go for a medium Sentinel and expect a 5mm longer RAD measurement for a bike that's 54mm longer in wheelbase alone. The problem with the acronym is that the measure (bb to handlebar center) was somewhat meaningful before it was broscientized by 4.47--mm to the hundredth decimal! If you don't understand, it's because there's not much to understand. I've a tape measure and some bikes to go off, so will not be reading further.
  • + 2
 @MTB-Colada: 196cm x 4.47=876cm. Measure from bb center to bar center. Compare.
  • + 0
 @clinder: You're getting negpropped for making a basic clarification. Thankfully, props have no units, and so no relevant meaning....
  • + 1
 @clinder: Right on with this, and using this thought is how I measured a frame to see what size I should get. (I thought it worked great) The hypotenuse of the frame's reach and stack should be close to, but not more than my RAD number. If the number is more, then the frame is too big, if it's close but less, then dialing in the RAD is obtainable with a short stem, a bit of sweep on the handlebars, and very few spacers on the steer tube...
  • + 2
 @brewweasel: I find the hypotenuse (I like the term effective downtube) should be ~50mm less than your RAD to get it dialed for me. That is using bars that are 25mm rise and a 40-50mm stem. It can be closer if a 10 or 15mm rise bar is being used.
  • + 2
 @clinder: so where do you measure to on the handlebar? significant difference if you measure from bb to the handlebar just outside the stem. Versus if you measure from BB to end of grips... especially if your bar is 760 or wider
  • + 2
 @ChrisBergin4: measure to a line that intersects the grips. Which is by the stem. Your tape measure will stay parallel to the frame. To improve your accuracy try taping a piece of string from grip to grip and measure to the center for the string.
  • + 2
 @clinder: super helpful, that makes way more sense. I did exactly what you said with the string and got a much more accurate measurement. I am 5’8” (172cm) and so my ideal rad is 773. Using your measurement tactics my current Setup has a rad of 787. I have all my spacers installed below my stem and my bar is 20mm rise w 7 degree backsweep. To try and get my closer to ideal I could swap my stem which is a 60mm Thompson but it lines up perfectly over my fork offset right now... not sure what effect shortening it would have on bike stability. Any adjustment suggestions to shave 14mm to get to my ideal rad?
  • + 1
 @ChrisBergin4: The two easiest options are

1) a shorter stem, which is almost always the easiest, cheapest and best solution. I'm not sure what you mean by " it lines up perfectly over my fork offset."

2) a lower handlebar.
  • + 1
 @leelikesbikes: thanks so much Lee! Will experiment!
  • + 2
 @ChrisBergin4: moving the spacers from under your stem would be the easiest. I usually leave changing the stem to last because it affects how the bike handles.
  • + 1
 @clinder: good point
  • + 1
 @clinder: wouldn’t loering my handlebar increase reach and make for a longer RAD?
  • + 1
 @ChrisBergin4: each 10mm spacer removes from under your stem will increase reach (3-4mm) but decrease your stack more (8-9mm). This will result in an overall reduction in RAD.
  • + 8
 “A wise man, before he unleashes vitriol, reads the entire post.”

- Me, 2018
  • + 7
 I'm just here to fail at reading comprehension and mention useless extremes where RAD doesn't apply...
  • + 5
 I don't even have to measure it and know that according to this, my current RAD is way too big. With 178 and bike's reach over 500cm. Yet it feels great and much better than smaller bikes.
  • + 1
 Well I‘m 1,56 and the reach of my bike (560mm) is far too short. And the head angle of 61 degree ist not slack enough!!
Happy now?
  • + 7
 I'm sure a reach of 5 meter is too much, even according to modern standards Wink
  • + 4
 Sorry bro your bike is too big
  • + 4
 Lee McCormack is an acknowledged elite MTB instructor, having coached world class MTB'ers and lesser mortals for years. While no single formula is going to be perfect for everyone because of different body proportions, range of motion differences, previous injuries, riding style, etc., this does get you in the ballpark. From there, do what works for you.

My measured "RAD" falls within 10mm using the formula and I'm built like a skinny twisted beef jerky with long arms and legs.

Lee also has a sense of humor in addition to MTB skills that most of us can't approach. Please read his caveat in the above article again: "Your ideal bike RAD is determined by your body’s size and proportions, as well as your handlebar width, crank length, pedal thickness, shoe thickness, phase of the moon and, by extension, the grunion run." :-)

Ride on!
  • + 4
 I use the Male measurements for females. Specialized proved we are generally the same as a trend. Just purchased and read the book, and it's dead on. You have to read the whole thing, at first, the reaches sound tiny, until you account for WHERE THE GRIPS are with short stems and high sweep bars. My Stumpy, which is a full size larger than Specialuzed recommends, is exactly setup how he recommends. And I got there by myself.
  • + 4
 So much common sense in this. New bikes have become much longer, while placing the riders further forwards when seated to keep the front end weighted. But off the saddle the riders are now reaching the limit of their movement far more easily due to that longer reach.... which is surely counter to where longer bikes excel- steep and fast terrain where riders need a huge range of powerful motion.
  • + 4
 I tried RAD on all my bikes....and funny enough the numbers work for me. This system works by far better than an isolated reach number, seems to be the new chainsaw lenghth. I like people at 1,68 complaining about their bikes ( 500 mm reach is too short for me....lol)
Reach without stack doesn’t really mean a lot....
  • + 4
 This is only some of the truth.

If I have a long bike with short chainstays it will ride somewhat awkward because Im so far back and cant apply enough pressure.
Theres a point why Specialized went longer chainstays with their new Stumpi Evo (as Pole, Propain already did).
Im Not the biggest Specialized fan but nearely all of their bikes are spot on- the Stumpjumper Evo especially.

Mandy, many will follow I bet
  • + 3
 'Warning: These multipliers will give you shorter RADs than you typically find on fashionable bikes. Bikes have gotten longer but people haven’t.'

Or bikes have been too short for years.. anyone who's ridden off-road motorcycles will know mountain bikes have always been too short.

No doubt there's some truth in what is being said here but it feels like this won't give you the right bike for your riding but a bike that at least fits you.
  • + 2
 I do not think this is right and simple answer, your app index influence a lot, person with same height couyd have varaity of proportion's long leg/short torso, long torso/ short legs, rad distance without angle make no sense, since you can achieve same rad with different reach and stack heights ( it is triangle) also seat tube angle affects bike a lot, as well as other angles. ..

Being short torso/ long legs person, seat tube angle for me quite important since seaddle rised far above the stem even with lovered dropper post, and that's move my weight over back wheel
  • + 2
 RAD is just effective reach and effective stack with some lost information (angle). Calculate the angle then you have effective reach and stack (Cartesian coordinates) in polar coordinates. It's the exact same data. You could use RAD as a quick and dirty way to calculate if bikes of a different category (compare an enduro to an XC bike) are close to fitting.

"Shouldn’t we be measuring bikes in a different way? For instance from pedals to grips?"...No! That doesn't tell you if the frame fits or suits your needs. You could have custom bars made for any bike to get you hands back in the same position. I could take a tiny kids bike and build some bars that are super tall and have an initial forward sweep and get my hands in the same position as on my XL bikes.
  • + 2
 The previous handlebar article was pretty dead on for me. Based on RAD my current bike is too small but I knew that already. For 2014 geo and sizing it was right on paper but it always felt on the small side. 2014 XL’s had seat tubes that were to tall to size up. My calculations have my RAD at about 809. For most mountain bike manufacturers that puts me on an XL regardless of stack:reach ratios. Some XLs even still fall short . I’ve suspected for a while I should through a leg over an XL bike and see how it feels on my local trails. With stem, spacers, and bar factored in precisely maybe it puts be between L and XL so I should stick with a L. Either way, XL’s still have pretty long seat tubes for me.

So if I don’t like stems longer than 50mm for handling and don’t what a bunch of spacers under the stem (since that starts to shorten reach) what size bike do I look at? I don’t think RAD/Spread on its own is enough but it may be more valuable than just reach or stack when looking a numbers and trying to figure out which bike and size to try.
  • + 2
 Wake up. Smoke some grass. Write and article.... Will stick with my 760mm bars and I am 185cm but have narrow shoulders for my height. Get someone who knows what they are doing to help setup your bike, not for them but for you. Different riders like different setups. Spring rate, compression, rebound, body dimensions, flexibility, power, fitness all play a part in setup. Benchmark of someone similar to you. Your setup may change as you get stronger, injured, more flexible, ride different types of track etc.
  • + 3
 Wake up. Have a deep fried snickers. Proofread your post.
  • + 1
 @fazza24: read again. I stand by what I have said. I have had a good few injuries from racing over the years and have come back OK from them. Wink
  • + 2
 RAD ( if thats the name but I have personally been using this a few years back but dont know what to call it ) is another important tools that goes with wheelbase and reach.
Its a a fine tuning that composes of stem, headset spacers and handle bar back sweep. Since front triangle is non adjustable and this is one way to fine tune your Bb length to ideal reach of stem.
I started with 50mm reach stem, then 45mm, 40mm and finally 35mm and Baaaaammmm!! Finally an ideal set up base on my riding preference. I tried 30mm reach for the stem just to see how it feel and its short. I ended up with 35mm stem. And I still have to Fine tune my handle bar back sweep. I have the 10 degree back sweep and I can feel the different , its a little short and I ended up 9 degree back sweep and I think its hit the spot.
I have been recommending this set up with my bike buddies everytime I was asked for an Ideal bike set up.
  • + 2
 I prefer to normalize reach for a desired stack. My saddle height is consistent across bikes and I know how high I want the front end relative to it. I also know the bar I'm using. The question is, what's the reach when the bars are at the right height?

For example:

Frame 1:
Reach: 460
Stack: 590
HA: 70

Frame 2:
Reach: 441
Stack: 645
HA: 67

Frame 1 looks longer, but let's dig into that. Say I want a stack of 665. I'd plug that number into this:

Adjusted Reach = Reach - (Desired Stack - Actual Stack)/TAN(RADIANS(Head Angle))

Frame 1 has an adjusted reach of 433.
Frame 2 has an adjusted reach of 433.

Despite a 19mm difference in frame reach, these bikes will have an identical fit when I bring the bars up.
  • + 1
 Interesting! can you eloborate on the /TAN(RADIANS_Head Angle)) portion of this? For this non-scientist lol
  • + 2
 @whiteblur: Sure. When you add stack to a given frame, reach reduces because the head tube angles toward you.

(Desired Stack - Actual Stack) gives you the vertical distance you're adjusting for.

Dividing by the tangent of the Head Angle translates that vertical distance into a horizontal distance.

"Radians" converts degrees to radians; it's only there because I pulled this formula from a spreadsheet. You'll want it with Google Sheets or Excel.

The next step is to consider the stem length the frame is suited to use. The 80mm on my steep XC bike would be a rudder on a slack trail bike. If I wanted to run 40mm instead with the same bar on a new trail frame, I'd need that frame to have an adjusted reach 4cm longer.

(Quick digression: this assumes the stem body is horizontal when mounted. If your stem angles up or down when mounted, your effective stem length isn't what's printed on the stem. Stems are measured on their longest axis, not the horizontal; a +30D 60mm stem will be significantly shorter than a 60mm -17D stem. This will affect how the bike steers.)
  • + 1
 @alexdi: Thx. Using your first example, how do you calculate the tangent of a 70-degree head angle? I see that the Radians would be 1.2273 based on a calulator, how about that tangent? Smile
  • + 1
 @whiteblur: I'm just using the TAN function in Excel and Sheets.

=460-(665-590)/TAN(RADIANS(70))
  • + 1
 @alexdi: Got it! Thx again! I assume your desired stack incorporates stem rise, spacers and handlebar itself, e.g. the 665 desired stack is where you want your handlebars to 'land"
  • + 1
 @whiteblur: Yes. I assume a horizontal (around -10D) stem, no spacers, and a bar with no rise, so the 'desired stack' is apportioned entirely to the frame. Few frames will be right on the money, so I use another formula to determine the depth of the spacers under the stem for a given frame.

Spacer Depth = (Desired Stack - Actual Stack) / SIN(RADIANS(Head Angle))
  • + 2
 If I had base-lined my RAD on my bike 18 years ago, today I'd be riding a modern mountain bike with my stem on backwards and 640mm bars with a "detroit flip". Here's an idea: Demo a bike before you buy it, and see how it feels. Get close, and adjust things as necessary.
  • + 2
 well it makes a bit more sense to measure this way for me as I am 183cm but with 12cm ape index, so usually M sided bikes are too short for me, but largre sized has too long seat tube....god bless please keep the seat tubes to 420mm and just play with the reach and I am fine then. Hehe funny the handlebar guide put me on 805mm bars which at first (yeah I´ve seen the hint in handlebard sweet spot guide) my shoulders would pop off just behind a curb and second it makes me feeling like a truck driver
  • + 1
 @leelikesbikes what is the correct way to measure RAD? From the end of the grip? Back side? Front side? Middle? Then to wheee on the BB? Middle of the Crank attachment circle/hole? Middle of BB shell?

My bikes measure 903 and 915 from the outside back edge of the grip to the center of the BB/crank hole. Using your formula that means it is right for someone 6’7”. I am 6’4” (with longer legs and shorter torso).

The 903 bike feels a little short when riding and the 910 bike abiut perfect. Also. When I do the picnic table test the 903 bike is abiut 5-10 mm short and the 915 abiut perfect.

Either I’m measuring wrong, have very weird proportions, or the formula doesn’t work well for tall people.
  • + 2
 Measuring is tricky. Start at the middle of the crank bolt. Run the measuring tape parallel to the frame. Stop at the point where the middles of both grips intersect. This will likely be just above your stem. More details in the book ...
  • + 3
 @leelikesbikes: Say what? Okay, NOW this makes sense. I'm pretty sure many peeps here (including myself) were measuring from the crank out to the end of their bar. The difference between measuring that way and what you are saying here is 70mm for me! Measured this way I am indeed near my proper RAD. You should update the article to include this.
  • + 1
 @b-mack: agreed!! An article update would be huge to avoid the confusion/FUD
  • + 1
 Hey Lee, I read your book "mastering mtb skills" when I first started out. I enjoy your writing and find it helpful. Also enjoyed the philosophical tidbits you dropped in that book.

One point I wanted to make is about bikes with adjustable geometry having the ability to change their bottom bracket heights. Another method of altering the RAD. I find my bike surprisingly more stable with the stem slammed and the Geo in the high position. My frame has 430mm reach and I am 167cm riding an Orbea Rallon.
  • + 1
 I gave it a try and it worked out for me and my Proces 111 pretty well. I reduced the RAD by 15 mm just by turning the bars more in and lowered the stem. Went for a test ride and enjoyed every second of it becoause of improved handling! So, my fellow mountain bikers, forget the bullshiting discussion and take it or leave it. Lee is not forcing You into anything!
  • + 2
 I don't think RAD solves everything but it seems useful to measure RAD and consider it when determining if a new frame will fit and when dialing in stems, spacers and handlebar width, rise and setback.
  • + 1
 Why not to take measurement from bb directly to the bars end? To get your bar width involved. You know, even 20mm difference affects your back position on the bike, besides we used to ride different stem-bar combo depending on the discipline.
  • + 1
 This seems WAY more appropriate. Bar width is crucial. This would account for it without a bunch of silly extra stuff.
  • + 1
 For years, I've recorded the stack and reach of each of my bikes, along with notes on my perception of fit. I found that there was a "pocket" of space where the bike felt just right. This assumes that the seat tube angle and length allows positioning of the saddle in the correct position...the only time this was an issue was an extra slack ST angle created by over-forking a bike.

If the bars were Forward or Below the pocket, it felt too big.
Behind or Above, and it felt cramped.

Also noted the measured wheel weight distribution front to rear of each.

60/40 seemed the best for XC. 65/35 the best for descending....
  • + 1
 Referencing the Size Matters articles from MBR where Chris porter talks about the exact same measurement, his number comes out to about 5 instead of 4.47 or 4.6. Would be interesting to see his thoughts on this and if the benefits of his numbers strictly come down to stability and that loss or power and torque is less of a concern seeing how he talks about how definecies in progressive geometry are caused by a lack of rider strength, body position, and technique.
  • + 1
 This is really helpful. I just rode a longer reach bike and realized my current bike is too small. I have added some taller bars to increase the RAD (unknowingly) but it still doesn't feel right. I will look at this for my new bike
  • + 1
 I am ~190cm which means my RAD should be ~840. I had a bike that was almost spot on 840 and just replaced it with one that is closer to 880 and am loving the extra space. I can't imagine going back to a short bike, the long one is better at everything.
  • + 1
 I've been following this for years. All of my bikes are 33.75 inches from the side of the crank spindle to that side's end of the handlebars. Despite having a hardtail, an XC bike and a 170/160 enduro bike with the appropriate parts, they all feel familiar when I hope on.
  • + 1
 Warning: These multipliers will give you shorter RADs than you typically find on fashionable bikes. Bikes have gotten longer but people haven’t.

The above comment is an understatement. Am 6'1" and I ride a L Sentinel. Measurement was 80mm too long. So do I need to get a S frame with 25mm stem and 620 mm bars?
  • + 1
 Read this, thought, "What a bunch of malarkey," and measured my XC bike. I've never felt more at home on any bike I've ridden and my height x 4.47 was spot-on exactly what the bike measures.

There's a lot of subtlety to bike geo but there is definitely something to this.
  • + 3
 IMO, this fitting system makes a ton of sense and feels great on the trail. I made adjustments to all my bikes a couple years ago.
  • + 1
 Chris Porter (another guru of bike fit and function who should not be ignored) has said that an ideal “RAD” measurement is right about half your height. So according to Chris, Lee’s ideals are all way too short. Just sayin’.
  • + 1
 I have also found that all of these measurements are far more accurate if you measure your outstretched arm length (as you would calculating your ape index) and then AVERAGE that length and your height. For example: my height is 177cm but my arm length is a whopping 185cm...so I use 181cm as my “height”
  • + 1
 @b-mack: yep, I'm with you on this. I think it's flawed not to take into account limb proportions. I'm 182cm tall but my arm span is 194cm. I don't even have super wide shoulders, just gibbon arms
My legs are also long for my height so I end up looking scrunched up on a bike that perfectly fit mates the same height.
  • + 1
 @b-mack: Maybe if You are advertising for Pole. By this standard, at 6’3.5, I would be a RAD of 958 (968 if factoring my long arms). The RAD of an XXL Santa Cruz Hightower is only ~890...and on their charts, I’m smack between XL (RAD of ~860) and XXL.
  • + 1
 @Kickmehard: If you buy the book or use the calculators at the website, you can account for your proportions.
  • + 1
 @s5traut: Yeah I get what you mean, I was just pointing out that none of these numbers are gospel. I'm 5' 10" and my rather normal feeling large Commencal Furious with pretty standard components has a RAD of 880....By Lee's numbers I should be basically unable to ride this well but I sure wouldn't want to drop down to the 795 he recommends. In fact even a size SMALL would only get me down to about 810mm. I really don't think I should be on a small Furious with a 40mm stem....I mean, that's smaller than the medium DH bike I rode in 2008!. Now Chris Porter's numbers say I'm spot on...
  • + 2
 @b-mack: and your bike feels good right? Is it hard to say which approach is better? I don´t think so, not to mention that CP looks at the bigger picture as there is a lot more to bike geo than rider space. You can have the road bike and DH bike with the same RAD number yet something tells me they won´t ride the same, just like bike with short reach and 100mm stem won´t behave in the same manner as long bike with 30mm stem. And yes, numbers suggested by this guy are basically what we had 10 if not 15 years ago and most people would agree that modern bikes(even the very average ones) behave so much better that it´s not even funny. They could work if rider was made out of piece of wood and didn´t have to move around... Maybe.
  • + 1
 @s5traut: hey man... I'm the same height as you. Our RAD is 858 not 958. XXL Hightower sucks anyways. Too big and the STA is rediculously slack for taller dudes.
  • + 1
 Ok I'm no expert here that's fore sure but I tried this and Im not even coming close. For example my bike is a Pivot 429sl size medium with a 90mm stem.I am 5'10 1/2 which equates to 179cm tall. 179 x 4.47 gives me a rad of 800mm. My bike measures a rad of 848mm, if I tried to get it down to 800 my knees would be hitting my handlebars and yes I measured parallel to frame not out to ends of bars. My other bike a Foes mixer is even worse. Not understanding this at all
  • + 1
 Are you asking for advice?
  • + 2
 @slick1: Most of the time, when riders hit their knees while pedaling out of the saddle, it's because they've leaned too far forward and are operating in a squat rather than a hinge. You might try pushing your hips back and balancing on your feet.
  • + 1
 So I'm still confused there are a lot of people on here saying there current rad is way longer than what Lee recommends including mine. My current bike a pivot 429sl is a medium in order to get the rad that Lee recommends I would have to be on a small and at 5'10" that is way off there recommendations. Also all the major bike brands are stretching out there top tubes, I just can't understand this all the big bike brands winning races and championships can't be wrong what gives. thanks for any polite comments
  • + 1
 Interesting article!!! I find this part funny. “These days, as frame reaches get longer, many riders should consider a smaller size.” First the industry starts off with petite frame sizes, now everyone is pushing for longer, lower and slacker, and now your telling us to downsize. Wtf Facepalm
  • + 1
 I agree that body position starts at the crank, but disagree on the RAD simplification for two reasons:
1. Seat tube angle and inseam will determine your seating location.
2. Bar width will determine your back angle.
So you could fit very differently on two bikes with same RAD.
  • + 3
 Read my next post ...
  • + 1
 @leelikesbikes: When are you expecting this to be up? I've just measured my RAD and I'm an 805cm human rocking an 830 bike. Sized medium GG Smash, so it has progressive GEO, nice steep seat tube angle. I've semi-drunk the kool-aid, but before I'm dropping $ on stem/bars for a bike that "already feels good," I would like to read more about RAAD.
  • + 6
 @y0bailey: I've submitted the article. Assuming the Pinkbike editors want to post it, the timing is up to them.
  • + 1
 This book has way too many acronyms that are created to be cool, or RAD. It’s hard to get behind the information that he’s putting out there when it sounds like a MTB Bro wrote the whole thing. Basically the take home info, want a radder bike, shorten it and raise the front end.
  • + 1
 Hi Lee, Interesting read! Going to apply these rules on my next frame build. Quick question, do you measure from the bb to the middle of the bars in a straight line (like the drawings) or do you go from the bb to the end of the actual bars?
  • + 1
 RAD might be a useful way of measuring a bike.
But giving out a single riders height to RAD conversion factor (and sorry, of course a different for women) seem a little bit too simple...
What about a RAD-angle?
And to TK ...the conversion from cm to mm is part of the magic of the 4.47 factor ????
  • + 2
 Please read the last paragraph of the post. We'll talk about the angle next time.
  • + 1
 I’m calling bullshit. This isn’t a mesurment of a bike it’s a measurement of set up and components and really only makes sense once you’ve got the correct size frame.

Personally, I prefer to use reach and chainstay length added together. This give me a better idea where I am in the bike and whether I can get my arse over the back axle.
  • + 1
 To me it always feels like more reach brings the bars further away and more stack brings them closer again as I typically have my shoulders behind and above the bars. So to make a longer reach bike suit I'd rather see increased stack than reduced. RAD may be an interesting number if paired with the slope (angle) of that line. I'd (within reason) rather leave that slope the same and play with the RAD rather than the other way around. And maybe that slope would even have to be relative to the actual horizon. So that is, if a bike is primarily designed for descending it will get you less reach and more stack whereas a bike designed to be competitive on climbing sections (or at least upsloped sections) more reach and less stack would be more advantageous. DH bikes respectively trials bikes come to mind. And yes I'm putting stem length, actual reach and handlebar setback all under the same denominator of reach as I'm limiting myself to straight riding here.

I may be the odd one here to define a geometry parameter relative to the (mean) horizon instead of to something fixed with respect to the bike. Then again the geometry of an unsprung bike doesn't tell me much either (right down to the chainstay length of a typical full suspension bike) and I found setting sag on a slope works better for me too. So at least I'm somewhat consistent Wink .
  • + 1
 "So to make a longer reach bike suit I'd rather see increased stack than reduced."

Yeah this isn't making much sense to me either. Apparently my "RAD" is about 15mm too big. That means I should take my two stem spacers under the stem and put them on top, reducing my RAD but increasing my reach? Would that not DECREASE the amount of torque I could apply, plus make my arms have to reach even further?
  • + 2
 @rezrov: If your RAD is too long, you'd either raise your bars (more spacers, higher rise bar, etc.) or bring your bars back (shorter stem, more setback on bar, etc.). Taking out spacers would lower the bars and result in a longer RAD.
  • + 1
 Crazy, I totally dreamt this line in my head and thought it was a million dollar idea. Being around 6'1" i've always been between L and XL, riding nice wide bars but i thing there is some credibility to it. If you have a bike w/ low bb and high stack even if it has a long reach it feels smaller. Any way I thing there probably is a perfect angle and measured length from center of bb to top of head tube to make a good judgment of what bike will fit good.
  • + 1
 Using the 4.47 multiplier, my current bike setup is 50mm too long. I am running a 30mm stem with 8mm of headset spacers, making it impossible to achieve my RAD. My issue is that using the manufacturers sizing chart, I am bang in the middle of their recommended size. So do I go with Lee's sizing recommendation or the manufacturer ?
  • + 1
 Whatever feels best ...
  • + 1
 Was anyone else annoyed by the inconsistent units. Why not just multiply your height by .447 and get a suggested rad in the same units you used for your height measurement. That way it doesn't matter if you're measuring in cm, mm, inches, hands, furlongs, or parsecs.
  • + 1
 So at 6'1" (185.5cm) my RAD is 829cm according to @leelikesbikes formula. I just measured my new Stumpjumper Evo 29 Size S2 which feels a bit small although I haven't ridden it off-road yet (because the seatpost doesn't go high enough and that seemed like a pretty good indication that this bike isn't large enough although it does have the same reach as my Stumpjumper ST Expert 29 Size Large -which I love). Anyway the RAD on both bikes is way off, the Short Travel stumpy is 910cm and the Evo is at 885cm. I felt that the Large Stumpy ST was a bit short on fast steep knarly descents but feels great otherwise but I've been told my bike is too small and that Specialized bikes run small so I should be on the XL. So basically I went from thinking my bikes were to small/short to now finding out according to my RAD calculation I'm on bikes too big for me! Now I'm more confused than ever especially because these PinkBike guys review bikes longer than what I ride and I believe they are shorter than l am so what the heck?! My BMX background has maybe lead me to smaller more playfull bikes so I'll just stop overthinking it and listening to others and just ride what feels good. I wonder how tall @leelikesbikes is?
  • + 1
 Go up to Clinder's comment above about how to measure the RAD and Lee's followup so as to make sure you're doing it right. I'm the same height as you and HOW you measure the RAD is very important to getting valid info so you don't go charging off on a data-rich, but commonsense poor, wild goose chase.

BETTER YET, BUY LEE'S "DIALED" AND GET IT RIGHT FROM THE START!
  • + 1
 PS to my above response: According to Lee's website he's about 5'8.5".

Hope that helps.....ride on!
  • + 1
 I agree with jddallager. How you measure is critical. I gave some detail in one of these comments. You can learn a lot more in the Dialed book.

--> We can of course ride a wide variety of setups. This system has proven to work well for me, the people I work with in person, and the members of my online MTB school.
  • + 2
 My bike is actually too small for me ito top tube length, yet according to this the RAD is too long. I don't think you can use RAD on it's own.
  • + 1
 What a waste of digital space. This does not factor important things like HEAD ANGLE, seat tube angle, wheelbase BB height. Crap like this is what a poor bike sales person would spew, along with colour scheme.
  • + 1
 nailed it!
  • + 1
 Head angle, seat tube angle, wheelbase, and BB height, while important when selecting a frame, don't really factor into RAD at all.
  • + 1
 I'm not near my bikes to measure atm...but there's going to be 20cm+ spread in RAD between the DJ - 26" DH - 27.5 Enduro - XL 27.5 DH...and they all "fit for purpose".

I like the idea of a RAD figure on frame specs.
  • + 1
 I measured my old Giant Reign 2015 in L. The RAD is roughly 84 cm. My new XL Bird AM9 has a RAD of roughly 87 cm. I'm 190 cm, so i need a RAD of 84,9 cm. The Giant has a MUCH worse fit than the Bird. Theory debunked.
  • + 0
 Motocross bikes have had dialed geometry, well even some mid 1980s bikes still handle very well to this day, so for a long time.

As an MXer, when I first began riding mountain bikes about 5 years back, the awkwardness of MTBs took me by surprise, but I adapted in time.

UNTIL I went to AF Bike Park on a couple of pretty modern Enduro style bikes and when I went to stand up for long periods of time, I truly realized how much geo on modern MTBs was just, terrible. Really bad. The Reach was so short that if you stood in a balanced position, your knees were literally mere inches from your knees. If you leaned way back to try and correct, your weight wasn't centered, the bike handled poorly, and my legs were shot within half a day from holding myself in an awkward position.

I don't doubt that those above RAD dimensions result in efficient pedaling. I also don't doubt that some much more talented rider can go right down this roughest of steeps with his weight well forward of his front contact patch. I can't.

I am MUCH FASTER and SAFER on a much longer bike. I also climb and turn better.

Add 4"+ to that RAD dimension imo.
  • + 2
 Sam Hill uses a tape measure. Same here. Angles and reach are a bitch to measure. If your buying a built up bike who cares! If you build up bikes your self different story.
  • + 1
 i have read every one of these posts, i even measured... me and my bike get a long RADly , but what i dont understand is why arent we discussing the lunar phase? i like bikes, lee likes bikes, i like lee
  • + 1
 I ride a 820 Spank bar and calculated that with the length om my intestines - the length of my right pinkyfinger x 0,29, spot on
  • - 1
 How does RAD work out for you when you're sitting down? Only out of the saddle components of riding have been mentioned in the 'pros'. Yet the majority of the time on any bike other than a DH/park bike is spent riding seated.

Proper in-saddle fit is the most important, regardless of downhill performance, simply due to the time and energy spent in it. Period.
  • - 1
 "Butt to bar" is your friend for seated reach. As you say you are on your butt 90% of the time on a trail bike so its important.
  • + 1
 So, my wife XS bike is spot on. My Large Stumpjumper 2019 that i find spot on if not on the shorter/fun side is 120mm too RAD...
  • + 2
 Can a bike actually be Too Rad?
  • + 2
 @ReformedRoadie: that s apparently the point of the article. Don t buy bikes that are too Rad.
  • + 3
 @FlorentVN: oh...I thought the point was as a bit of self promotion.
  • + 1
 Can we get some clarity on the discrepancy on bar width recommendations? This is different than his last article posted recently.
  • - 1
 To divide riders between male and female is balleggs... My friend has longer legs than me and is 8cm shorter than me... I have much longer torso and arms... So this proportions between legs vs torso I find is key and then how Vorsprung said,... how your hip and wheight is levered between wheels oterways you ride with your wheight too on the back and you loose torque, pumping and speed... But freeriders and bmxrs need to ride on the back
  • + 2
 “Maximum torque for power moves” is something Mac from It’s Always Sunny in Philadelphia would say.
  • + 0
 Are you still using this basic multipliers for different riding styles? (Enduro, XC, XCM...)

If you’re male, multiply your height in centimeters by 4.47

If you’re female, multiply your height in centimeters by 4.60
  • + 1
 The RAD would stay the same, but the RAAD (Rider Area Angle in Degrees) would change. So the bars on an Enduro bike would tend to be higher and further back than on an XC bike, even though the RAD would be the same on both.
  • + 1
 oh.. at 180cm height, I think I should have bought small size frame to get the spread of 800mm
  • + 2
 "You're only a few millimeters off."

That's what she said.
  • + 2
 If this is true, I should be riding a small size !!!! Idk
  • + 1
 Anyone remember when you just used to choose a S M L or XL and go from there.
  • + 1
 After telling me I should be on 830mm handlebars, I think I’ll pass on this guy’s advice. Also feels like an ad.
  • + 1
 Where do you have that info from? I read one of lees books and he recommends a bar that is as wide as your optimal pushupposition. For me that works very well ( circa 760mm at 180cm). He is not a fan of megawide bats.
  • + 2
 Ok, i found the source and i think his old non mathematical method was way better. There is no way a mathematical formula with just taking heigth in consideration will be correct for most people.
  • + 2
 @optimumnotmaximum: The bar width calculation includes average shoulders and arms. If you want to learn more about accounting for unusual proportions, check out the book or website.
  • + 1
 @leelikesbikes: i will check it out. Despite not really being a bear of a man i would not think of myself as having unusual proportions. Considering my own calculation the feedback here and the geek facts i know about probikes i assume, that the calculated widths are a bit on the wide side. Anyways your pushup method really helped me finding my favorite barwidth. Also there was a time i took "mastering mountainbike skills" about everywere i went, in my opinion a must read for everyone who is serious about mtb, great book, pretty cool i can tell it to you in person. Keep it up
  • + 4
 @optimumnotmaximum: I used to suggest the pushup method, but I don't any more.

1) Pushups only use pushing strength.

2) Great riding uses a lot of pulling. The more advanced you are, the more pulling you do.

3) Maximum pulling strength happens at a narrower hand width than pushing.

4) We need a compromise of pushing and pulling strength. Hence my new approach and the new method of determining bar width.

I hope that’s helpful.
  • + 0
 @leelikesbikes: First, I appreciate you taking the time to try to help. I understand how word of mouth is vital in what you do. However, a couple of things.

Second, you really need an effective maximum on your bar width suggestions. At 6'3" the bar width suggested is already way too wide for anything but flow trails. Add in the fact that I have broader than average shoulders and long arms and the width has to get ridiculous. That's where you are losing some people because of the huge numbers they are seeing just don't make sense in real world riding, even if they are biomechancialy optimal.

Finally, the modern world has gotten sensitive to lure and pay wall marketing. Perhaps instead of overtly shilling your paid content you should make the basic calculators, for the information you provided here, free. That way you get people to your site and the desire to pay happens organically. Just some unsolicited advice.
  • + 1
 @cofo11: Thank you for your advice. The post about handlebar width contains notes for talller/bigger riders. The online calculators were a ton of work (and required a lot of experience and skill). They will not be free. A lot of people will be served by the multiplier in this post. If you want more detail, please pay for it. Heck, it's only $25 for the ebook.
  • - 1
 @leelikesbikes: I would hope you meant creating the formulas required a ton of work and skill? Otherwise that is purely hyperbole and more lure and paywall tactics. Putting the basic multiplier in this post onto a page is script kiddie level easy, as is implementing even more complex formulas once they have been created. Creating the formulas is always the hard part.

As for paying for it, why would I do that? I think more inline with the likes of Chris Porter. Physics agrees with that design philosophy more. True, your numbers may be optimal biomechancialy. However, I believe they ignore several other factors that contribute to the overall riding experience.
  • + 3
 @cofo11: The basic multiplier comes from years of research and a whole lot of formulas. It's a distillation of my full method. Have fun on your rides!
  • - 3
 @leelikesbikes: That's not what I asked or what you asserted. Why the evasiveness? I tried to engage you civilly until you attempted to up-sell me on something using hyperbole. Of course I am going to challenge back on that. As a software engineer I find your claim that "the online calculators were a ton of work (and required a lot of experience and skill)" to be ludicrous if you are talking about their implementation.
  • + 2
 My 26” bikes has been RAD all along!
  • + 3
 Quackery
  • + 2
 Book hasn't sold as well as expected, I know get an article in Pinkbike.
  • - 2
 do yo even RIPROW RAD Bro? Same dude that wrote books on how to race BMX.. but never raced at any level, same guy behind the riprow junk ?!? We're all so tired of people profiting off our sports by filling them with misinformation and gimmicks. Of all the amazingly intelligent industry folks out there why is my feed always stuffed by crap from this tool?
  • + 1
 I personally think that trying to belittle someone that is offering knowledge is a much larger travesty than trying to make a living. The riding books Lee has written were all along with a very well respected professional rider. While Lee himself is an accomplished rider, raced pro DH for several years, he still enlisted the help of Brian Lopes in his MTB skills book. In the BMX book you reference there are several top pros that helped, including Jason Richardson (Dr. Jason Richardson actually). Many of the skills from BMX and MTB crossover as far as technique are concerned.
As for the RipRow, maybe you should try one before you call it junk. As far as anyone being a tool, the only tool here is knowledge, either learn or move on to another article, its simple...
  • - 6
flag fuckofff (Dec 28, 2018 at 20:29) (Below Threshold)
 ????????@DTShane:
  • + 1
 @DTShane: "the only tool here is knowledge" ... wow that is a good one.
  • + 1
 Just multiply your RAD by .44 for guys and by .426 for girls. That way you'll have another useless number to think about.
  • + 0
 Step number one to achieve perfect bike fit and happiness: don't buy a Specialized unless you want to be laughed at by your buddies all ripping YTs.
  • + 1
 Being today 28th dec, I think it is a joke. The article couldn't be more stupid...
  • + 2
 Huh? Those bars make want to puke
  • + 1
 I suck at math. Should you do this on or off your ADD meds?
  • - 3
 Some of these points are so generalised it's pointless. For example, just saying keep the distance between your cranks and grips the same. So I can have my grips vertically above my cranks at the same distance and my bike will be RAD?!?
And at 186cm (6' 1") it gives me 826mm bars!! I want to actually fit down the trail when I ride my bike.

I know the idea is to sell a book. Must be a slow news day.
  • + 2
 That's not the handlebar width. That's the RAD dimension. The multiplier assumes you already have the optimum width for you.
  • + 3
 Lol it’s not your bar width you spaz!! For what it’s worth I’m really fussy about bike set up and am sensitive to small adjustments. I’ve just done the RAD measurement and my bike is spot on! What this means I don’t know but my bike is set up exactly where he says it should be.
  • + 2
 @mikelee: shoes on or shoes off?
  • + 0
 @fartymarty: shoes are irrelevant imo. its just the measurement of how much room is needed for any given size person,this is of course his opinion on how much room a rider needs to perform at their best. from my interpretation he's saying if a rider of x height would need x amount of room to control the bike in any given situation. the bikes dimensions are irrelevant regarding this measurement. hence why sam hill uses it as a base because he knows no matter what,at least he has the room to manipulate the bike in however he needs.
  • + 3
 @mikelee: as a guide I get it, or comparing your bikes but on it's own it's not that useful IMO
  • + 4
 @fartymarty: I don’t think it’s meant to be used on it’s own but it seems very accurate to find out how much room is needed to congtrol a bike. I checked my brothers bike using the same system and again it was pretty much spot on. We’ve both been riding over 20 years and both come from elite dh racing background. Maybe this system suits a more aggressive rider. I ride a medium and my brother a large and both bikes are different travel and geometry. However we seem to correlate to the RAD measurement. Maybe it’s just luck!!
  • + 1
 @fartymarty: glove thickness?
  • + 1
 @ermoldaker: Q Factor, crank lengths, pedal thickness, pedal width - there are so many variables. Its probably best just to test ride a bike before you buy it.
  • + 1
 @fartymarty: good point
  • + 2
 I bet my bikes are RAD!
  • + 1
 Height measured in stocking feet, mtb shoes off?
Thanks!
  • + 1
 With or without gloves or a chamois?
  • + 2
 RAD bikes are RAD
  • + 2
 I have a bike, rad.
  • + 1
 I agree that a little short is better than too long. But you have to take into account the head angle, chainstay length, and even wheel size in correlation to find the perfect setup for turning. Its complicated and nobody has figured it out yet.
  • + 1
 product phishing
  • + 1
 delete
  • + 0
 Wouldn't the angle of the RAD play a big roll?
  • + 1
 Yes it does. Lee explains it on his site and book. Hopefully he does an article about it and his other theories for fit. It makes much more sense when you combine everything.
  • + 1
 I call that Rider Area Ange in Degrees (RAAD), and that's in my next Pinkbike post.
  • + 0
 How does this help seated positioning?
  • + 4
 It doesn't, at least not directly. That's another discussion.
  • + 1
 This is related to being able to actively move around and use power moves, two things that don't happen during normal trail rides with the seat up.
  • + 0
 Controversy! It gets the clicks no?
  • + 1
 My bike feels so rad bro
  • + 1
 POWER MOVES!
  • + 1
 my rad is 95mm too long
  • + 0
 Stack + reach...
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