Reach and stack based sizing for mountain bikes
News Source: Transition Bikes
In a joint effort between Turner and Transition bikes, a new standard for mountain bike frame sizing has been introduced. This new standard is based around reach and stack measurements, and is intended to clarify bike fit across bike models and brands.The evolution of mountain bikes has made the old system of top tube and seat tube based sizing irrelevant. The wide range in seat tube angles and bottom bracket heights can create a situation where one bike could feel longer or taller than another frame with the same measurements. Once a rider is in a standing position, the fit and feel of their bike’s cockpit is determined exclusively by the handlebar and pedals. Finding the specific geometric relationship between those two points is the only way to accurately compare the fit and feel of different bicycle frames.
“I was really stoked to get the call from Sam at Transition Bikes regarding a new method of measuring mountain bikes, especially those used for technical riding like our DHR. For years I have not listed a top tube measurement for the DHR as I knew it was irrelevant in comparing the fit of our bike with other brands,” says David Turner. “The great thing about this sizing method is that anyone with a piece of string with a weight on it and a measuring tape can accurately measure their current bikes. The rider can then compare their current bike to any brand using Reach and Stack and know exactly how it will fit without even riding it.”
The horizontal distance from the bottom bracket center to the top of the headtube centerline is referred to as reach. The vertical distance between these two points is known as stack. By comparing the reach and stack on different frame models, the rider is able to identify exactly how their bike will fit and feel on the trail. This system eliminates any uncertainty created by the seat tube angle, and forever drops the need for “actual” and “effective” top tube measurements. The reach and stack of a frame is the most important sizing information for a freeride or downhill rider but it is extremely valuable for trail riders and XC racers as well.
![photo]()
“I was aware that Turner was using the reach number to size their DHR, but under the name cockpit; so I approached David Turner with the idea that this should be an industry standard measurement,” said Sam Burkhardt from Transition Bikes. “Dave expressed interest in adding a vertical component and going forward with an industry standard. We chose the terms reach and stack after Kris Wehage from E.13 Components pointed out the use of the same measurements in the Time Trial and Triathlon communities. Rather than create a new name, we felt it would be easier for manufacturers and riders to adopt the system using existing names.”
Turner and Transition bikes encourage all mountain bike manufacturers to include these numbers on their specification charts for consistency in the industry, and to aid rider’s looking for the best possible fit for their body type and riding style.
For more information on reach and stack, or help in understanding the new sizing standard please visit:
www.turnerbikes.com
www.transitionbikes.com
In a joint effort between Turner and Transition bikes, a new standard for mountain bike frame sizing has been introduced. This new standard is based around reach and stack measurements, and is intended to clarify bike fit across bike models and brands.The evolution of mountain bikes has made the old system of top tube and seat tube based sizing irrelevant. The wide range in seat tube angles and bottom bracket heights can create a situation where one bike could feel longer or taller than another frame with the same measurements. Once a rider is in a standing position, the fit and feel of their bike’s cockpit is determined exclusively by the handlebar and pedals. Finding the specific geometric relationship between those two points is the only way to accurately compare the fit and feel of different bicycle frames.
“I was really stoked to get the call from Sam at Transition Bikes regarding a new method of measuring mountain bikes, especially those used for technical riding like our DHR. For years I have not listed a top tube measurement for the DHR as I knew it was irrelevant in comparing the fit of our bike with other brands,” says David Turner. “The great thing about this sizing method is that anyone with a piece of string with a weight on it and a measuring tape can accurately measure their current bikes. The rider can then compare their current bike to any brand using Reach and Stack and know exactly how it will fit without even riding it.”
The horizontal distance from the bottom bracket center to the top of the headtube centerline is referred to as reach. The vertical distance between these two points is known as stack. By comparing the reach and stack on different frame models, the rider is able to identify exactly how their bike will fit and feel on the trail. This system eliminates any uncertainty created by the seat tube angle, and forever drops the need for “actual” and “effective” top tube measurements. The reach and stack of a frame is the most important sizing information for a freeride or downhill rider but it is extremely valuable for trail riders and XC racers as well.
“I was aware that Turner was using the reach number to size their DHR, but under the name cockpit; so I approached David Turner with the idea that this should be an industry standard measurement,” said Sam Burkhardt from Transition Bikes. “Dave expressed interest in adding a vertical component and going forward with an industry standard. We chose the terms reach and stack after Kris Wehage from E.13 Components pointed out the use of the same measurements in the Time Trial and Triathlon communities. Rather than create a new name, we felt it would be easier for manufacturers and riders to adopt the system using existing names.”
Turner and Transition bikes encourage all mountain bike manufacturers to include these numbers on their specification charts for consistency in the industry, and to aid rider’s looking for the best possible fit for their body type and riding style.
For more information on reach and stack, or help in understanding the new sizing standard please visit:
www.turnerbikes.com
www.transitionbikes.com
Author Info:
Must Read This Week
[UPDATED] Final Elite XC Results & Overall Standings from the Mairiporã XC World Cup 2024
42116 views
42116 views
Sign Up for the Pinkbike Newsletter - All the Biggest, Most Interesting Stories in your Inbox
PB Newsletter Signup
Its just a lot of people arguing about whether or not it works and how it will change with different components, and most are complete idiots.
1) we're not trying to re-invent the wheel here. the point of this is to have all manufacturers standardize the way they disclose bike/frame geometry. the point is to level the playing field a bit to make it ultimately easier for the consumer/bike shop employee/etc. to know the geometry of bikes and be able to compare across different sizes of between different models/manufacturers.
2) Don't worry, we're not saying we want to "replace" any other way of measuring bikes/frames. we're only stating that traditional methods don't always tell the entire story. most manufacturers report their geo numbers in different ways. this is just one step closer to having all manufacturers report in the same way for apples-to-apples comparing. our only real goal here with this is to get other manufacturers to list reach and stack along with all the other measurements currently being given. we're not replacing anything, just adding more info for those that can benefit from it.
3) of course you need other measurements in order to make reach and stack meaningful. fork height being of ultimate importance. i guess one way we could have made this "press release" better would be to have listed that fork height is really what determines the reach/stack measurements. every frame/bike was designed around an axle-to-crown measurement so obviously this plays a huge part in determining reach/stack. you simply can't have one without the other. our bad for not including the a-to-c in the drawing above.
4) the point of getting all manufacturers to report the numbers the same way is to aid in comparing "same use" bikes against each other. for example, if you're in the market for a slopestyle bike you really would want to look at all the bikes in the market for that use and compare the sizing. reach and stack help in determining what the actual size is (meaning, the relationship of BB to the handlebar position given the a-to-c and fork angle). Obviously you could misuse this information by comparing dis-similar bikes (ie: a DH bike with a DJ bike) which would make for utterly meaningless comparative info.
5) in all honesty this is not a "standard" so much as it is just a call to other manufacturers to start listing this information. we're not claiming we've come up with this new way of measureing (as noted in the press release, this measuring system is commonly used in other cycling disciplines). our point is to help drive adoption as we believe (as does Dave Turner) that it will ultimately help the consumer in understanding how a bike will fit them. The more info the better!
Hopefully this helps clarify the intent of this press release. To all the other manufacturers reading, hopefully you understand our intent here and don't feel daunted by the task of spending a few minutes and opening your drawing files, taking the measurements, and posting to your respective websites. i would think that disclaiming bike geometry to its fullest would be equally important for everybody in the business of selling bicycles.
good job
strange that it's been so hard to clarify this to these people.
too many concussions? i don't know
it all makes sense
the cockpit length of your bike is one of the most important things about the way your bike rides. that and bb height and chainstay length.
the way most companies measure the size of their bikes really tells you nothing about the actual length of your bike, because the seat angle is never the same. therefore, without doing a bunch of math, you can't tell how a bike will fit you.
read the rest of the posts about this, the only people against it are the ones who obviously don't know what their talking about. talk to pro's about how important the effective length of their cockpit is.
i've been as clear as i could possibly be. top tube length doesn't tell you how long your bike actually is. length of your bike= very important too how it rides.
oh, maybe thats it. you couldn't tell the difference how a bike rides anyways. you're too busy weighing your bike parts too ride them
you're stupid too
@ds68698 + bigtard-The current measurement standard is perfect for all types of bikes. Want proof? Check out two years from now to see how many manufacturers are using other measurements. My money is on zero. Then, check out how many manufacturers list the weights of their products. It'll be more than zero. Don't worry, you'll have lost interest by then. Most people that have been cycling seriously for more than a season or two care about weight no matter what the discipline. Maybe we'll talk in 2 years when you each have 2.5 years of experience. Until then-enjoy the ride and leave the thinking to the qualified people.
I'm in no way saying every bike shop sells bikes without giving guidance, I have just seen it happen. A kid and his father walk in to "Western Cycle" ( Edmonton, Alberta ) the kid looks at the most expensive, colorful and shiny free ride / DH rig(This just so happens to be a Devinci 8 Flat
I think this will catch on because the old system just can't cut it the rapidly advancing technology in cycling. Change is as good as the rest. Good job Transition and Turner on bringing this to light!!!
Oh and can I sig "Welcome to pinkbike.com, where Grammar is used by few, and opinions become facts"?
Rotating your computer monitor, as Sngltrkmnd put it, changes the H/A and the Verticle line which represents the rider position simultaneously. Therefore the reach and stack measurements don't change.
In the real world forks come in all sorts of different lengths. Changing the forks Axle-To-Crown changes the bikes head angle which (assuming we don't change the verticle stack line) changes the reach and stack measurements.
I hope that makes sense. Seems pretty obvious too me
Also we must have some sort of idea about the reach and stack of bikes we already ride before we are able to compare to this suggested standard.
How do we know what reach and stack is ideal for us? If you take all of the current frame measurements and layed out a sketch on paper, you could draw the exact frame, right?. Could you do this with stack and reach?
I think this will be more confusing and complicated to the consumer instead of clarifying and simpler. I also feel like many of you underestimate the knowledge and abilities of the consumer.
My bike measures 430/630 (reach/stack in mm) - this is easy!
For DJ/street bikes, it may be handy if it catches on. Most jump and street bikes are fairly similar in geometry and run similar length forks. And from what I can tell, there isn't a lot of dirt jumping going on with people sitting on their seats. If the system is designed just to describe how a bike fits while standing up, then yes I can see it working (if it catches on). The geometry charts will continue to describe the riding characteristics of a frame and proper fit. And as pointed out above, the only way to truely check the fit is to sit on the bike and go for a ride.
from there you decide stem length based on how long the frames cockpit length is
old school measuring is crap, it has no relativity at all. this can at least be standardized.
+1 for the guy who said it would make bike shop employees lifes' a lot easier
I am not trying to muddy the waters but just lend some of what has helped me. I started using the reach measurement a year, ago, and it has MOSTLY been helpful when working from a bike that I know fits me very well and trying to find something else that will fall in that ballpark. I can measure a bike and know, definitively, when the reach will be outside of my range. Having said that, I have found that Front Center (from front axle to center of cranks) and Rear Center (chainstay) are easier measurements to take and almost just as pertinent as reach, although comparisons can only be done when frame angles are similar. The bottom line for me is that of the bikes I have gone through I keep a database of frame measurements (with Reach, Front Center, and Rear Center, along with a couple others), and classic top-tube or seat-tube measurements are meaningless.
And I think we all know better than to put a 40 on a P1 or an XC400 on a V10. Count on a 1' HA change for a 1" change in fork length, right?
On your second point, you're right, but that's only relevant as long as reach and stack is "new".. and it is easy to measure anyways.
Yes, with conventional, detailed measurements you could basically build the frame... but I think the point here is that instead of looking at 6, 8, or 10 numbers... it all boils down to 2 numbers that define the BB relative to the handlbars.
Nevertheless, the very good news is that 2 manufacturers agreed on the same name, and hopefully many others will follow!
Nice one guys
Since suspension bikes necessitated interrupted seat tubes that no longer originate from the BB, Seat tube angles mean very little and Effective top tube measurements even less (unless you ride with your seat at headtube height all the time)
This new "standard" will work well for DH and FR bikes where you stand 90% of the time, for AM and Trail bikes however, it becomes important to know where the Seat tube angle will position your seat when you are sat down pedalling. Hard to tell from a brochure, hence the need for test riding!
I like Dave Turners idea of leaving off Eff top tube length on DH bikes (its irrelevant and confusing to customers!)
Science = good. Ignorant banter on pb = bad.
Props to PearlJamSoCal, and to Sam Burkhardt, who know WTF they are talking about. Sheesh, props to TRI BIKE manufacturers who actually know what THEY are talking about. (Even if their bikes are laaaaame.)
So in their (small) minds, each type of bike will be measured differently? If DJ bikes are to be measured this way, what about XC bikes? It is absolutely asinine to think that this measuring system can replace the existing measurements for XC/AM bikes. So if the idea behind this is to 'avoid confusion', how can that happen with different measuring systems used for different styles of bike?
All you need is seat tube angle, length, and effective top tube length. Those are the important cockpit measurements. Sorry Transition and Turner, but you're stupid. Not stupider than the people you're trying to sell too ('cause they buy into it) I guess, but that's not saying much now is it? Did you guys know that some people are taller than 6 feet, and actually peddle their bikes? Crazy thought, eh?
They are trying to build an image, which is essentially the only way a company like that can survive. Stick to that and you may do fine. Overstep their bounds, pretend to be innovators or influential members of the industry, and we'll see what happens.
My main issue with this topic is that I think this is a prime example of change for changes sake, and not only is it not needed, but we would actually be better off without it. If it were to catch on (which I can guarantee it won't), it would simply add confusion/clutter to the process. Image based companies often have to create change for changes sake (and confusion/hype), so I understand the choice to pretend like they are really on the ball and plugged into the industry, but come on...how about actually doing something meaningful and/or worthwhile?
Theyre not making it so the manufacturers have to make them to set sizing regs.
Its just going to be a change in the way the size is measured.
Companies will still have the freedom to make the bike whatever size they want, but they will use this system to measure the sizes
Quote:
“The great thing about this sizing method is that anyone with a piece of string with a weight on it and a measuring tape can accurately measure their current bikes. The rider can then compare their current bike to any brand using Reach and Stack and know exactly how it will fit without even riding it.â€
Welcome to pinkbike.com, where Grammar is used by few, and opinions become facts.
I looked at your profile half wit, I know you own a shop. I was generalizing the "go to a bike shop and ask questions" comment, not telling you to go to a shop, It's obvious you know allot about bikes. I wouldn't tell a squirrel to collect nuts. A job, haha, I make probably 3 times what you could pay... I'm flattered, I really am, you know how to use sarcasm, how sweet. Buh-bye sweet heart.
Lets think of it this way, you have a DJ set up sitting in your garage. You want a new "frame", for your "bike". So measure the "frame" of your current "bike" as described above. Then go to your local bike porn shop, measure the "frame" for your "bike" you wish to purchase. Then, here is the best part, compare the measurements. Yaaay.
Where can you buy these "frame bikes" your talking about, do you have a contact, I want one? I didn't know you can have a bike without a frame, they must be made in China or somewhere.
The components will change the geometry of the bike, yes, I never said it wouldn't. Reading comprehension, that's two words, and yes, one is 13 characters long.
Yeah, who would put a DH fork on a DJ bike? Me? Totally, why not, or, we have something called SARCASM we use in the English Language.
Quote: (from the above provided reading material)
"The great thing about this sizing method is that anyone with a piece of string with a weight on it and a measuring tape can accurately measure their current bikes (Bikes have frames). The rider can then compare their current bike(with a frame) to any brand using Reach and Stack and know exactly how it will fit without even riding it."
"Bikes have frames champ". In case you didn't know.
You need to learn two things, reading comprehension, and what sarcasm is. Many doors will open for you, hang in there sport.
i have felt what this differce in forks does since at one time i had a P.2 on a DJ then a triple drop off, this made my reach rly short but my stack taller then before. these measurements rock! they makes researching sizing a bike so much nicer!
BTW Some posters need to learn to read a schematic. Hilarious posts!
Let's call this "Pinkipedia".
maybe both?
MTB's don't already have enough of those!
But the reason between then should be the same (Reach/Stack). That is the real size of the frame.
I think...
I don't entirely understand the new system myself, but I'm definitely not going to say it won't work just because I haven't figured out how to use it. From my understanding so far, it sounds like a bike with long reach and short stack will be very steep, whereas with short reach and long stack it will be very slack. Although reach and stack will change with what fork you use, the combined number of the two will remain the same, and if this number is higher, the frame will be bigger.
Although this sounds to me like a great way to measure frame sizing, you could have a bike with the perfect reach/stack for you but end up getting an 18 inch chainstay. So yes, this system sounds great, but obviously if i understand this the companies will still have to list chainstay, BB height, etc. so you will know exactly what you are getting.
I don't know how much sense that made but those are my thoughts.
Just because two forks are the same travel, does not mean they are the same length. The important measurement (for forks) is the axle to crown height.
I know, I said that 5th comment on this reply
www.pinkbike.com/photo/2799689