Video: Vorsprung on Understanding Advanced Bike Geometry - Part 2

Jan 1, 2019
by Vorsprung Suspension  

In Part 2 of this episode, we look at Front Centre to Rear Centre (FC:RC) ratio and why it's a seriously important factor in bike handling that's rarely discussed. We compare numbers between a few different bikes, all of which have notable geometry for one reason or another:

1. Deviate Guide 2018, size large - the best cornering bike we at Vorsprung have ridden
2. Transition Patrol 2016/17, size L and XL - Pinkbike's Bike of the Year in 2016 (same geometry in 2017), and an all-round great bike
3. Pole Machine 2018 - in the vanguard of "long/low/slack with a steep seat tube angle" and geometrically an absolute weapon in a straight line, with some caveats
4. Nicolai/Mojo Geometron G16 - even more extreme geometry than the Pole
5. Nukeproof Mega 2018/19 - radically "conventional" geometry compared to the rest... and the overall winner of the Enduro World Series in 2018 under Sam Hill. Phenomenal skills aside, why is he winning on seemingly old-school geometry?


MENTIONS: @VorsprungSuspension



128 Comments

  • + 32
 Key lesson from this video is that RC:FC ratio is important and thus generalizations about bikes (including bike reviews) really need to take into account the size of the bike.

A medium with "short chainstays" (425-43cmm) may very well have that ideal RC:FC ratio whereas the same bike in XS or an XL may have a non-ideal ratio and will behave substantially different.

I think this is a prime example why the "superenduro" bikes like the firebird and the spartan were reviewed negatively due to their short chainstays (with 6'+ riders) whereas the length of those chainstays may be perfect for a person who rides a medium where the RC:FC ratios are better.
  • + 18
 Excellent comment. I totally agree. Props to companies like Norco who change the chainstay length for each bike size. I never understood why someone 5'0" should ride the same size chainstay as someone 6'4".
  • + 2
 Yes!! Which again, I'll go back to my controversial comment during the whole series... their insistence on choosing bikes to compare based on reach numbers vs the actual bike size meant to be ridden by riders of different heights, was always going to end of with flawed impressions of bikes. Didn't make sense to me... and now makes even less sense.
  • + 1
 Maybe - I just did the FC:RC on a large Spartan 29 and with a short offset fork it's 1.836, and with a standard offset (like what was reviewed) it was 1.851, which puts the Spartan with standard offet between the Deviate that Steve says he really likes and the XL Patrol, much lower than the Pole / Geometron.

Personally, I reckon the FC:RC might be relevant there, but the RS shock in the Spartan's is really poor, which has more to do with the harshness reported.
  • + 7
 Having owned a Geometron and ridden several more 'conservative' geometry enduro bikes, I would make the following observations:

1. The Geometron was the best climbing bike I've ever owned.
2. It was hard work to bunny hop because of the massive weight shift involved. I found this especially when riding a trail blind and having to react quickly to an obstacle. If I knew in advance that I needed to bunny hop something, it was fine because I could plan ahead.
3. On steep trails it was extremely fast and cornering was not a problem (due to weight being naturally forward)
4. On more mellow trails, the bike would understeer in corners unless I consciously weighted the front. Never had too much of a problem losing the front wheel, just ran wide a lot on turns.

In the end, because of the type of trails I ride most often (in Ireland), the more conventional geometry is a better compromise. It's not as fast on the steeps (but not far off), but that's probably about 25% of my riding - and faster everywhere else.
In the end IMO, it comes down to the terrain you ride most often.
  • + 4
 I think we are on the same page there. The Pole is so hilariously comfortable (similar to the Geometron I would imagine) when pointed up a hill that I literally climbed for 5 metres and wondered why every other bike isn't like that.
  • + 6
 Good Stuff! Love seeing some free body diagram action. It highlights the suspicion I've had that going super long isn't without its consequences. It will be interesting if longer rear ends become the new thing on fast bikes or maybe better, proportionally longer rear ends with increased size. I suspect that there will be a pendulum swing back to shorter bikes or downsizing frame size to some degree in the future. Spread getting too long limits the power and functional range of movement you can put into the bike. Lee McCormack has some thoughts on this that I think bear looking into. Of course if trails just get straighter and straighter with bigger berms there isn't so much need for good cornering.
  • + 4
 For sure, a balance will need to be struck somewhere, and given the relatively slow changes in bike geometry in the past year or two compared to what we were seeing 10-12 years ago on DH bikes, I think we are approaching that point. Appropriate sizing and fit are not my particular area of expertise, McCormack among others has better insights on that than I can provide, but I think it's pretty reasonable that sizing/fitment should come first and the rest of the geometry should be built around that to whatever degree is feasible. In other words, you can't for example just increase the spread enormously to try to give yourself more leverage and reduce load on the hands, the spread needs to be approximately decided on first and then the rest of the frame's geo built around that.
  • + 1
 @VorsprungSuspension: Agreed. Spread is where it's at. Interesting times and loads of good bikes out there. Are you going to do a review of the Deviate Guide at some point in the future? I realize it's not your normal content but it's an interesting bike and I for one would love to hear more about it. Especially whey you stay it's the best cornering bike you've ridden. Keep up the good work.
  • + 4
 @querent: probably not going to ever publicly review a bike as a whole sorry.
  • + 3
 @VorsprungSuspension: shouldn't the angle of spread be a factor as well?
  • + 1
 @jaydawg69: if taken to extremes it certainly becomes relevant (and is described by reach/stack already) but not really relevant to the point we're making here. The difference between 90deg and 0 deg (vertical/horizontal) is obviously outlandish and would be the difference between hanging off the back of the bike and being in a pushup position. Within practical limits though, it's not a big concern for this particular aspect - it'd have to be forcing you into a certain body position for it to be particularly relevant to arm load. Lower stack and longer reach however may put more load on the lower back and hips though, for example.
  • + 0
 @VorsprungSuspension: so many facets of geometry of a bike that one measurement cannot be the determining factor. Best thing is ride different sizes and see what make you feel the most comfortable and for some what is the fastest.
  • + 2
 @jaydawg69: for sure, handling is a complex thing, and comparing any one measurement alone is a long way from a complete understanding of bike handling. I like cornering a lot though, so I look for bikes that do that well, and now that most bikes have sufficiently slack head angles, BBs at an appropriate height and decently steep STAs, we have the privilege of being able to dig a bit further into the numbers if we're being picky about what we like Smile
  • + 1
 @VorsprungSuspension: it would be interesting to find some corners and do some timed tests. Are short stays better for corning, etc.
  • + 6
 Norco increase chainstay length with frame size. That's half the reason I bought my Sight.
  • + 2
 @TheLocalSpokesman: Funnily enough I think the chainstays themselves are actually the same across frame sizes to reduce SKUs and manufacturing costs but the lower main pivot changes location to change the rear center value (what most people call chainstay length). The front triangle already needs to be different across sizes so it's no extra cost but would seem to be better for handling and bike fit.
  • - 1
 "Long bikes don't corner well" is just a myth propagated by people who haven't ridden one. You end being a little more aggressive but the bike corners just find. Personally I prefer how they corner because of the style which is more drift/sliding than just turning.
  • + 9
 @SintraFreeride: i had "a long bike" for a year and realy wanted to like it- but did not. Even though the clock told me i was going as fast as on my previous bike, i struggled hard. I simply was not able to make the huge weigthshifts needed to make such a bike work.
  • + 1
 @SintraFreeride: personally I think your right, my whip is a 29er with 475mm chainstays, yet it turns just as good as the mondraker vantage and PP Shan I had before it.
  • + 2
 @jaydawg69:
That is the general consensus, but why? Short chain stays mean shorter wheel base when compared to the identical axle placement for the front wheel. I like to think of it in motorcycle terms since I ride daily. A razor sharp handler like an R6 has a relatively short wheel base and steep steering head angle when compared to a cruiser. The sport bike turns in like nobody's business and the cruiser turns like a pig. One is meant for highest performance the other for long sessions in the saddle. Neither one does the other's job well at all, but are purpose built.

I expect that we'll see more of the same for general consumer bikes, ie: short stays, longer/relaxed fronts so that the average rider gets a nice middle ground. For DH specific bikes, I would expect longer wheel bases to aid in stability, but there is a point where too long becomes cumbersome. Interesting to watch for sure!
  • + 6
 @SintraFreeride: long bikes corner just fine whenever it's sufficiently easy to get enough weight on each wheel when you need it. A higher FC:RC ratio just requires you be further forward on the bike (relative to the BB) to achieve that, which means more load on the hands. If that load is tolerable to the rider, no problem. If holding that position is tiring or puts you in an awkward or uncomfortable (or just scary) position, then it's not ideal.
  • + 1
 @VorsprungSuspension: We are on the same page on that. I just find it tiresome to hear people say these new school bikes are only good in a straight line when they have clearly never tried one.
  • + 5
 @vorsprungSuspension thanks for this. At 1.93m I usually take an XL or XXL and had to find out the hard way that most bikes are a compromise in front centre / rear centre.

In picking my most recent bike I laid all the frame numbers out to help and the tried them. The bikes I disliked the most had really short rear centres. SCHTLT being the worst as it felt like I was riding on the rear axle.

In the end I picked Banshee as their frame had long chainstays and adjustable drop outs too. I'll never pick a bike with one size fits all across the range or no adjustability.

Frankly, I'm amazed bike manufacturers get away with this slackness. It seems like they just can't be bothered, Norco and YT I believe notwithstanding.
  • + 4
 There is a lot to be said for riding style and personal preferences. How many people do you know that love their so-and-so bike, size XS for one and XXL for the other. Sure Hill can destroy on almost any bike with wheels, it’s no surprise a conservative bike can win with him as pilot. Minnaar on an XXL with offset headset to max out reach? Insanely fast.
There are so many dynamic factors affecting ride, and geometry is just one of the variables. A good rider adapts riding style very quickly to ride most bikes at a very similar pace. Terrain, braking, tire choice, suspension setup and even the intangibles like committment and confidence play equal or bigger roles. It’s a whole package, and the sum is more than just the parts.
I’m as guilty as the next at looking at geometry tables and specs, making assumptions. But damn if
I haven’t gotten out on trail just to find that the latest greatest rig is just a dog for me... and often the other way around, I’m surprised how great a ride goes.
Have fun with charts, numbers and theory but never give up the chance to ride someone else’s bike. You might be surprised how much it can open your mind.
  • + 3
 Spot on. I'd say mountainbikers are worse than roadies when it comes to incremental changes because the variables increase with the changing terrain and the more dynamic requirements for riding a mountainbike. There are ranges within sizing that will work, but when people starting getting into 1 degree shifts or 5/10mm changes, it gets a little pedantic.
  • + 4
 two years ago i tried a L sized Capra and lost the front tire twice because i couldn't apply enough force on the front. Now i am riding a NP Mega 275 in M and loving it, and now i know why.
  • + 3
 @VorsprungSuspension Great stuff! By far the best explanation I have seen.

Shouldn't the endo angles on the Pole/geometron be shallower and not steeper than the other bikes due to the increased FC? (the angle was defined from the horizontal in the frst video)

Cheers!
  • + 3
 interesting as always. the discussions above regarding sizing of bikes that us the same rear triangle for all sizes is a big deal here eh. Taller guys are basically penalised by slack seatpost angles that put their arse over the rear axle when the 170cm rider has theirs much further forward on the Medium vs XL sized bike.


I think the Geometrons and Machines of this world suit the taller guys more but that main issue with the front end weight is also about ride style and steepness too....if you drop your chest to the stem, bend elbows and knees into a decent attack position and are shredding steep shit then they weight shifts to the front a lot anyway. Riding a slack bike last summer on greasy green runs was hideous, front end washout and i just couldnt load it up at all. Hit the black runs and suddenly it was easy to rail shit with grip and the bike came alive.

Slack n long for fast steep ripping, more conventional for trail and pop. If you dont care about climbing or climbing is everything to you then choose accordingly.

At least we have the choice now....5-8 yrs ago there was little between full suspension bikes (excluding DH bikes) compared to today. good times
  • + 1
 Exactly my experience with the Geometron.
  • + 2
 This is interesting, thanks to Vorsprung Suspension for the great content every time !

What I like to mention and I am speaking from experience you have to respect different rider dimensions and rider weight in this model as well.

I (195cm / 95kg) love this "modern long" geometrys a lot. The extra weight shifts on long bikes are no problem, the weight the body and the room are there.
It is or was way more exhausting to keep the balance on a "shorter" bike how often did i found my self hanging over the bar under heavy braking or at steep stuff. And at jump or climing with to much weight on the rear getting into trouble.
What i like to say, there are not just different bike geometrys there are different riders and riding styles too.
I feel central and relaxed like175cm Sam Hill on his Nukeproof, when I ride those long bikes.

Maybe it is helpfull to add a variable for rider size to the model and put it into realation with the rider weight.
This new factor need to be taken into account to calculate the rider forces for example on the handle bar and CoM.

It is clear that your model 80kg rider will need less force on the bar to get the 50% an an size M Nukeproof Mega, than on a size L Geometron. But the model rider will probably also never fit on all of those bikes.

The other way around a 100kg rider who is hopefully taller, should put how much force on the handlebar of a Size M Nukeproof Mega to get 50% ? Is he even allowed to touch the bar ? ;-)
  • + 3
 The assumption there is that force is in direct proportion to weight, that's why they're all listed as the same 80kg - if you're heavier you ideally should also be stronger and able to support roughly the same fractions/multiples of your. own body weight. CoM height would be more relevant to vary once you're on a slope, but that's why this comparison is done on flat ground, so that it can be removed as a variable.

At 195cm I have no doubt that you'll benefit a lot from a bike that fits you well first and foremost, and I think the current trend of longer bikes overall is very good in that regard.
  • + 2
 Glad somebody is finally talking about weight distribution on a bike. Seems to me like the trend of longer bikes with short reach and short chain stays would just take too much load off the front without compensating for body position. I think this also explains why the trend of staggering tires wider at the front has been growing in popularity over the years.
  • + 2
 I am missing one key point here: When talking about FC it really matters if we are talkin about the component head angle or reach. For head I am all with your calcs, but not for reach.
Longer reach does not require you to shift your weight forward more, it automatically forces you to do so. Your natural riding position (and cog) will be more forward, so you don‘t need to shift. Just a longer reach makes me struggle in the steeps, too much weight on the front. To unweigh the front you do need to shift your cog a lot. Me no liky. A slacker head angle helps to compensate in the steeps, bit the front unweigh problem remains. Just my thinkin and experience. But I do like the fact, that you are not a fan of those cruise ships...
  • + 1
 If you're on a bike with a spread so large that you're forced forwards, then I'd say the sizing may be off in some way (frame or setup). If you follow the approach of setting up your spread appropriate to your body size (check out Lee McCormack's article on that from a few days back) then no, FC is the determining factor, head angle isn't directly relevant (except insofar as it affects FC) because your bar position is being set relative to your BB not relative to your upper headset cup. If bar position and front axle position was kept consistent and you slackened the head angle without changing anything else, you'd obviously need a different stem size/position to get the bars in the exact same place (ie consistent true/adjusted spread), and in that example your body position and CoM would not have shifted whatsoever even though the frame spread has changed. Likewise, if you maintain the same bars-BB relationship and just push the front wheel out, regardless of whether you're simply translating the steering axis forwards or rotating the head tube for a slacker head angle, you end up with less weight on the front wheel.

I wouldn't say I'm not a fan of the long bikes. I'd actually personally like to try something with geometry fairly similar to the Machine but with a longer RC and slightly shorter (not much, just a bit) FC. It's not that the bikes suck, it's that their obvious advantages in a straight line (basically, better endo/looping angles) can in also make some things more difficult.
  • + 2
 @VorsprungSuspension thanks for the video. I'm the same height as you and also have owned Large and XL Patrols and your findings strongly reflect my feelings on the weight distribution on these bikes. I'm often wondering how my '19 Patrol would ride with a 450mm chainstay!
  • + 1
 Interesting, thanks! Do you feel wheel size is also a factor in cornering? Almost exactly one year ago I went from a 27.5 to a 29" Trek Slash. The bikes have different geometry and not just different wheel sizes, but one of the main things I noticed was that the lean angle of the 9er was more critical, I had to lean the bike over more and weight the front end more, vs the 27.5" bike.
  • + 4
 Everything has some effect on cornering and handling - it's very difficult to isolate the effects of wheel size because you can't change it on its own without changing something else in the process.
  • + 1
 Run your tyres lower psi would help switching 275 to 29
  • + 1
 Really interesting conclusion, I understand the logic but I have found the opposite. I moved from an older style "short" Geo bike to my current ride which is an XL 2016 Patrol and found that I got much less tired as the correct riding position is far more natural. On the shorter bike I felt too upright so putting weight through my bars felt really awkward and pushed my backside too far back behind the saddle. Now I can be in a much more relaxed overall body position due to the bike fit and have more weight through my hands as I can adopt a flatter riding position, at least that's how it feels... confusing!
  • + 6
 Out of interest how tall are you? Sounds like a bike fit problem, i.e bike was too small rather than properly sized bike vs long and slack bike.
  • + 2
 @zyoungson: inclined to agree with that. Fitment is important, if it's compromised substantially and your body isn't in the position it's naturally inclined to be in, then a lower FC/RC ratio isn't going to fix it.
  • + 1
 @VorsprungSuspension: Yes I would agree that the short bike was probably too small (although not by old Geo sizing standards Smile ). I am 6'1" tall but with monkey arms which I think also explains why the XL Patrol fits me well. I've not yet ridden a bike yet that is too long for me I suspect... I'd be interested to try a longer bike like a Geometron but I do think that there is such a thing as too long and my current bike is probably about right.
  • + 1
 @ddmonkey: I too am 6’1” with the dreaded ape arm length and after moving from a large yeti SB66 (which at the time had a “progressive” reach) to my new ride a SC Bronson V3 in XL I totally agree with you that body shape can also make a huge difference in the fit/geometry debate.
This is why I love that the industry is trending towards the short seat tube model so people can choose a bike more on total fitment rather than just their leg length.
  • + 4
 So what you're saying is if I get a size XS frame then I'll be able to corner better than Sam Hill Smile
  • + 5
 Haha! Maybe if it fits you properly then yes.
  • + 2
 made some long dropouts to make my medium banshee rune 455mm 17.8" chainstays. 30 seconds faster on 10 minute run.
Ive been advocating for long chainstays for years, its all true.
  • + 1
 I recently put the longer dropouts on my banshee phantom, haven't timed it but it does feel more stable and definitely helped out climbing steep tech.
  • + 1
 @VorsprungSuspension: Excellent video, and I'm a big fan of this series. Having studied vehicle dynamics, I wish there were more resources like this so that people could better understand the physics behind the bikes.

Though I'm curious about one thing. You mentioned that Sam Hill doesn't have to move very much to keep his weight balanced. While this is true, you seem to present it in a positive light, but I wonder if it might also be a negative?

Since the weight distribution on a short bike is more sensitive to CG motion, a rider on a short bike has less margin for error when moving, and might inadvertently transfer too much weight to either wheel. So a longer bike might be easier to ride, simply because the rider has more margin for error when moving around on the bike.
  • + 4
 That is also true - hard to quantify the rider's side but we can at least look at the bikes' numbers. One thing I have discussed with a few others is how longer wheelbases effectively increase the resolution of your movements, ie if you have a 1000mm WB, a CoM motion of 30mm constitutes 3% of the WB. If that WB was 1500mm, that 30mm CoM shift is only 2% of the WB - so coarser motions give you finer control. That's good for precision and stability, but means you need to move further to achieve any given CPL shift desired. However, even the difference between the medium Mega and the large Machine is only 12% in wheelbase, more like 10% in the same size, so the rider has to be 10% more precise (10mm motion becomes 9mm motion) in order to accurately weight the wheels as he wants to. That's not an insignificant percentage, but we (or I at least) don't have any data to show how precise the rider can actually be. Like if you have to be accurate to within +/-5mm of CoM position to get the load on the front tyre within the necessary range, and that becomes +/-4.5mm instead, but the rider's sense of balance allows him to be easily precise within +/-2mm then it's a bit of a moot point there. Or maybe we're already the wrong side of that and most riders can only be precise within +/-20mm to begin with and they need to be within +/-10mm? I don't know the answer to that.

The point however was more to do with highlighting the fact that some bikes require you to load up your hands/arms more heavily to get weight on the front wheel than others do. Whether you see that as positive or negative is up for interpretation for sure, but I think we can all agree that higher load on the arms leads to more arm fatigue more quickly. As Leo pointed out in the Youtube comments though, that isn't necessarily the first thing to limit the rider though, like if your back or legs are getting tired before the arms then who cares about the arms - and that is also hugely dependent on the rider's physical strength, riding style and ability.
  • + 1
 Great analysis. Obviously biased towards downhill riding performance. Part of the reason for the so called "new-school" geometry is to improve climbing performance (particularly useful in technical climbing) steeper seat angles necessitate lengthening the cockpit to maintain a similar seated body position on the bike. This in turn lengthens the front centre and changes the ratio talked about in this video. Unfortunately there is no way around that. I know people will chime in and say you could lock out your shock to stay more upright or ride a bike with more AS or even ride a hardtail, thereby keeping the slack seat angle and shorter front centre... BUT if your looking to not flip switches, want great rear wheel traction and compliance AND be able to climb steep tech in the seated position then a steep seat angle is pretty nice.
  • + 5
 Yep for sure, it's somewhat of a knock-on effect in that regard, and I 100% agree that the new school bikes are excellent climbers compared to older trailbikes. Maybe it went something like this:
1. Steepen STA for better climbing --> effective top tube now too short
2. Lengthen reach to get ETT back to realistic numbers --> FC now really long
3. FC really long --> now harder to get enough weight on front wheel
4. Longer chainstays to get more weight on front wheel --> now it's hard to hop/manual
5. Raise BB to make manualling easier? --> now it feels less planted and doesn't corner as well
6. ????
7. Profit
  • + 1
 @VorsprungSuspension: Yup. Interesting re number 5 I'm not sure anyone has done that to compensate (yet) but sounds like a decent idea to me. After all we've added a bunch of stability in lengthening the bikes FC and RC surely raising the BB a few mm is not going to break that...
  • + 6
 Great stuff Steve!
  • + 1
 @vorsprungsuspension Did you have to model the suspension to get the change in chainstay length at 50% sag?

Started riding a Turbo Levo a month ago, with short offset Lyrik 160 up front and I can’t get over how well it corners. 1230mm wheelbase, 455 chainstays static, so FC:RC = 1.7

Suspension feels incredible too, which I suspect is due to the much higher sprung:unsprung mass.
  • + 1
 Yes we did. Those numbers sound pretty good as far as cornering goes, and yes a heavier rigid sprung mass definitely helps with the small bump compliance!
  • + 1
 So I'm guessing to aliviate pressure on your hands you may be able to shift you're cleats rearward. Artificially ransfering the centre of weight forward? Would you also say we need longer chainstays relative to fc measurements to compensate? Or has reach gone too far? Ps I quite like my s150 xl with a reach of 490mm as its fits my 185cm body spot on. Could do with a shorter seat tube.
  • + 3
 Doesn't work like that unfortunately - if your COM is above the BB it's above the BB regardless of where your foot is positioned on the pedals. I would say though that longer chainstays on bikes with longer FCs make a lot of sense yes, not so much that reach has gone too far.
  • + 1
 So... I’m thinking that if my trails are mostly slow and technical flatland stuff with a lot of turns, then Pole or Geometron are the last bikes I would ever consider. Thankfully there’s another brand around with perfected aluminium frames that suits me and I would have hoped you had included them in this test, they’re quite popular in the alps and their name begin with Lite... But maybe they are too conservative in the geo?
  • + 1
 Great series, Steve! Seems like the newer geo lets you ride more centered while descending. Another way to put it would be the needed forward weight bias offsets the old school, butt over the rear axle, rear weight shift needed to keep the endo angle under control. I picture this as having a bigger sweet spot and more neutral position on the bike which I find less fatiguing riding the Pole Machine.
  • + 1
 For sure, whenever lateral grip isn't the biggest concern, a long FC is generally a good thing. With a proportionally long RC too, I think there is the potential to have the best of both worlds there - as long as people are willing to deal with it being harder to pop the front wheel up anyway.
  • + 1
 @VorsprungSuspension thank you so much for these informative tutorials. I'm doing these calculations for a bike I'm looking at buying, and am wondering how you came up with the 60 mm bar height for the adjusted stack. Spacers and handlebar rise?
  • + 1
 Just estimated it as an arbitrary figure for the sake of comparison, but yeah spacers and bar rise.
  • + 1
 You say the nukeproof has old school geometry but does it? Personally i think it's just not as long as some. Look at the geometry on the original mega that was old school. Also Sam hill uses a narrower bar to a lot of other riders which pushes his weight further back still.
  • + 3
 It seems that there is a flaw in the spreadsheet: the RC @50% travel for the Nukeproof cannot be 446mm when starting at 435mm, isn't it?
  • + 4
 Good catch (that's a result of fill-across on the spreadsheet from the column next to it!), it should be 437mm which gives a FC:RC ratio of 1.64 not 1.61.
  • + 1
 @vorsprungsuspension, appreciate all the time and energy you have put into this. I noticed that the numbers for the spreadsheet were taken on level ground. I’d be really interested to see how these numbers change with respect to a -15% grade and a -20% grade since most of the cornering we encounter will be going downhill.

Wondering if the rider would actually have to move his body less far forward to achieve the hand load required for 50% grip and if the rider might even have to move rearwards on the shorter reach bike to keep the 50% number.

Thanks!
  • + 1
 This clip tells me that bike makers need to start making bikes with adjustable chainstays like they used to, bugger speccing different lengths for specific sizes, let the rider choose!
  • + 1
 @VorsprungSuspension Awesome video and all but you did fail to mention that longer reach bikes tend to have shorter stems. I personally run a 20mm stem on my 520mm reach bike.
  • + 1
 Thanks for the kind words. It wasn't omitted by accident, just didn't go changing things between bikes arbitrarily as that just introduces more variables. For a given CoM position it increases the load on the hands if you run a shorter stem without changing anything else, which would be even less favourable to the Pole/Geometrons in this respect (assuming that we agree that reducing hand load is beneficial in this case, which you may not).
  • + 1
 Reduced offset fork would also result in an increase. Running a 29er up front of a G16 with same a-2-crown would again increase. The conclusion being drawn from this discussion and bikes selected is misleading (to me).
  • + 2
 @Soilsledding: reducing fork offset brings the front wheel back relative to the rest of the bike and would mean your weight can be marginally further back for the same contact patch load distribution, meaning less weight on the hands.
  • + 2
 @VorsprungSuspension: Thanks for taking the time to answer the questions!
Agree to not change arbitrarily between bikes however short stems are part of the concept of the new geometry. The stem length should be there (together with bar width and height) to adapt the spread of the bike to your height. It would be great to see a version 2 of the spreadsheet where those variables are adjusted to get a similar spread (which is what a tester would do in reality) and see the impact of the longer wheelbase/FC/RC while comparing bikes that all "fit" the same standard rider.

Cheers!
  • + 1
 @VorsprungSuspension: Fair enough. I agree that longer reach makes you ride further forward and thus more load on your hands. However, I don't see that as a drawback because you are centered over the bike. I feel I have more control then when I was on shorter bikes riding off the rear.
  • + 2
 @SintraFreeride: that's fair - I don't think that 0% load on the hands is the goal as such, but then again obviously 100% of your weight on your hands is not ok either. From personal experience though there is definitely a point at which it becomes tiring (or difficult when you're already tired) to keep enough weight on the front wheel. Maybe I just need to hit the gym though Smile
  • + 1
 The AOS system on last years GT bike had the bottom bracket move back as the rear wheel moved. This would keep you centered on the bike. was this idea ahead of it's time or to complicated?
  • + 1
 Hi Steve, after spending a fair bit of time on the older patrols, have you had a chance to ride the 2018/19 patrols where they changed the geometry a fair bit, and if so what were your thoughts on the differences?
  • + 1
 Haven't ridden the 2018 enough to really comment personally, but the FC and WB on the 2018 Large is quite close to the 2017 XL (which I had previously owned and not gotten on well with the lack of front wheel grip, hence not buying a 201Cool .
  • + 1
 @VorsprungSuspension: it's quite interesting that you had both L and XL Patrol's. can't tell exactly by video, but you don't look like a guy who would normally fit an xl bike! that must have felt huge, but it's cool that you ran that experiment for yourself. i'm assuming that's why you had one (?). it sure feels like a nimble yet stable bike to me at 194cm in the xl, but even this bike needs to be driven fairly hard given the head angle, compared to say, my Smuggler.
  • + 1
 @jamesbrant: The spread on the XL I was fine with (188cm), but yes I found I needed to be particularly aggressive for it to keep grip in the corners.
  • + 1
 @VorsprungSuspension:

Hi Steve,

Did you feel like you gained anything in steep, straight line 'plow-ablity' going from the L to XL Patrol? What about when you went from the XL Patrol to L Deviate Guide; did you loose something?

It seems to me that the FC /RC ratio would be a trade off / continuum between these two traits: steep straight 'plow-ability' and flat cornering grip or is there a combination that you feel provides the best of both worlds in one package?

(I personally think for me part of the 'unicorn' factor also has to do mixed wheel size - 29" front and 27.5" rear but that's a whole other topic!)

Another great series!
  • + 1
 @Xorrox: yes, the XL Patrol was better at smashing through steep stuff, most noticeable at the limit cases where braking as hard as you can still isn't slowing you down. How much of that is the difference in FC and how much is the difference in stem length (35mm vs 50mm to get sizing more similar) I'm not sure of, I rode the XL once with a 50mm stem and didn't like it before going to the 35. I didn't feel like the Guide was a step backwards though, it was at least better than the size L Patrol (longer FC than the L but shorter than the XL). Order of bikes was XL Patrol then L then Guide (some overlap between all of them) so never compared the XL with the Guide back to back. I did even ride a size medium Guide for a while whilst waiting for the L to arrive, it was ridiculously amazing in corners but just too small for me.
  • + 1
 @VorsprungSuspension: the spread on the XL was fine?


Is there any method to find whether the spread is proper size?
  • + 1
 @jungjoonc: Yep, the spread on the XL with 35mm stem was only ~15mm or so more than the L with a 50mm stem, and I preferred it as far as sizing.
  • + 1
 it would only be more tiring when cornering but less when going in a straight line (more stable, less weight shifting). Interesting convo for sure.
  • + 1
 Basically, yes. This particular means of comparison is only intended to provide insight into cornering though.
  • + 1
 Plus climbing is easier because the front end stays down for longer.
  • + 3
 @SintraFreeride: sorry thats again too much generalisation for my liking . (What is long?) Long bikes with short stays have a lot of weigth on the rear, so you have to weigth the frontend in order to climb well. Long bikes with long stays(more than 445mm) climb well seating, if the terrain is slippery and not very steep i found them to loose traction too easiely. The same goes for climbing out of the saddle. A lot also comes down to ridersize and ridingstyle. I am 1.8 m and found out that the combination of 460 mm reach / 610mm stack and 440 cs combined with an 65 headangle is perfect for me
  • + 2
 @optimumnotmaximum: When I say long I mean geometron/pole long, everything else is short. So long reach with long chainstays. My Pole Evolink size L with 460mm chainstays and 885mm front center and 520mm reach is the best climbing bike I have ever had. I now run a front 26T chainring with a 50T max cog just so I can climb the steepest stuff I can find! I am also 1.8m. I find this bike works better in every condition over my previous "short" bikes. Yes I ride way more forward when standing up than previously but I don't find that to be a negative, if anything I have less backpain.
  • + 1
 @SintraFreeride: I can confirm your findings.
  • + 1
 Would longer chainstays actually lessen the caveats of the Pole and the Geometron? So interesting and a quality video!! @VorsprungSuspension
  • + 3
 Yep. I'd really love to try a Machine with a 490mm or so chainstay just to see how it goes.
  • + 1
 @VorsprungSuspension: Finally someone tried to get the whole picture, thank you so much. What i experience with chainstaxs above 445 mm is, that is really hard to get the front of the ground. I am not talking about a casual manual on the street-every decent rider should be able to do that on any bike. Manualing through rollers or lifting the front over roots is a vital part of my riding and it became really hard with a long rear center, especially if your coming in less than perfect. What i am trying to say, is that there is also a limit how long chainstays can be without making it hard to get enough weigth on the reartire.
  • + 1
 @optimumnotmaximum: definitely - I'd like to try it and see where that limit is for me personally. I did not find the 455mm stays on the Pole to be a particular hindrance there, though if I rode more flow trails with rollers and stuff to pump/manual maybe I would.
  • + 1
 I’ve heard from friends who have ridden the Machine that it bucks on square edge hits. They sighted a forward axle path. Would this be a caviat you made allusion to?
  • + 2
 My experience agreed with that somewhat - it found it did hang up a little bit more on big square edges than some (not all) other bikes due to the fairly low effective pivot point, though to be fair my standard of comparison at the time was a bike with a very high pivot and idler which is exceptionally good at running over things. Other low pivot bikes are usually fairly similar in that regard, the Pole's suspension is not really remarkable in that respect. I was more talking about body positions required to maintain grip on the front wheel in corners.
  • + 1
 Cheers. Thanks for that. @VorsprungSuspension:
  • + 1
 Is that spreadsheet available to download? I may just be totally missing it.
  • + 1
 I think how steep the ground you ride will need too be added into this,as changes the angles and weight centres
  • + 1
 Looks like Norco's Gravity Tune has them ahead of the curve
  • + 2
 Great stuff. Nice work!
  • + 1
 Cheers, and likewise!
  • + 1
 Leo has a longg message for you on your youtube channel l
  • + 3
 Of course he does, it's an ongoing discussion Smile
  • - 3
 @VorsprungSuspension Loving this Tuesday tune subject, Steve! Can you show how badly the weight distro ratio varies for different sizes of bikes, say a small short travel 29er (e.g. SB45c) and a XL? Hinting at the different reasons why one size feels better than another, clearing up how it's more than just preference? Might actually question your stance regarding a short rider cutting a seat tube to fit on an XL, for the purpose of weight bias, at cost of "spread".

Could explain why people thought 29ers couldn't jump, or manual (front-heavy - long CS and steep HA). I personally dislike how the front wants to dive back to the ground if I don't "compensate" by shifting my weight way back on a drop, while others insist that all it takes is speed and the bike naturally flies straight...

I suspect that it's much more important to get everything centered around a rider's CoG when standing comfortably. The spread from this point determines freedom of movement as the bike pitches up and down (rider forward for climbs, rearward for descents). Move the seat forward to match the standing position, and optimize kinematics for that CoG... wouldn't this be the end game, becoming more about choosing wheelbase length and travel to adjust for the trail, your skill, and overall challenge levels?

Critical flaw in most designs could just be how designers plot the rider CoG to be forward of the hips while seated, rather than standing, also ignoring the bike's CoG. The M Spider 275c I rode had a nice bike CoG, forward of the BB just behind the forward shock mount, helping to feel balanced. Friend said similar of the Intense Primer. Despite how great I thought the Spider felt out of the saddle, I thought the saddle got in the way and didn't like how it rode in the saddle. Same with the med Jekyll 27.5, except the Jekyll sorely needed a steeper STA. Got my eye on a large La Sal Peak, after all I learned.
  • - 1
 Just seems to me that, through trial and error, I find that I like the center point between the front and rear axles, to be approximately 175mm forward of the BB (accounting for sag). This setup saves me energy out of the saddle, as I don't need to move much to compensate for the bike's weight bias.

It's convenient that a lot of side photos of bikes have the cranks level, so I can measure the pixels from the forward pedal threads to each wheel axle, preferring the front to be a bit longer to account for the front shortening under compression, and the rear lengthening from the point 175mm forward of the BB.

I only have theories regarding where to place the handlebars and saddle, to also make it so I can save energy in the seated position too, able to switch to a more ideal position to adapt to the trail, minimizing the movement necessary to get into that new position. Practically means that the saddle is moved forward to under the standing position, so your butt is hovering over it. With droppers, you can just get that out of the way if you want to unlock your leg suspension travel. Also means more clearance for rear wheel travel. The reach # is what it is... don't need to have it at conservative numbers, like 440mm, since the need to position your weight back won't be necessary with a bike that is no longer nose-heavy. What matters is that you're relaxed in your neutral upright position, until you do need to shift back for an explosive technique--hard to do that when you're already stretched behind the saddle. Basically how I understand how this forward-geo trend is going.

Basically, need more bikes to gravitate towards this sweet spot. Some bikes, in certain sizes, are close. Tall people on medium travel 29ers might be comfy on their bikes that are already in the sweet spot. A lot of enduro bikes in Large hit the sweet spot. Would like more options to hit it...

CS length has gotten a lot of flak. People demand short, but I think if you can't get it any shorter, you can make the front center longer to balance it out. It's a waste to give these bikes traditional reach and head angles, just because those #s are what people are familiar with. 450mm chainstays would work great on a 1300mm WB bike. 460 maybe on a 1350mm WB bike. 420mm worked well on 1150mm WB bikes, just as 435mm CS 160mm FS bikes seem to be getting positive reviews with 1230mm wheelbase.
  • + 1
 Thank you Vorsprung for some science documentary
  • + 1
 This spreadsheet seems to be telling me I need a Nukeproof
  • + 8
 Hahah, depending on how you read it, it could also be telling you that you need to be shorter!
  • + 1
 Nice work Steve!
  • - 1
 Val di Sole 2008, I'm betting Sam Hill wanted less weight on his front wheel, not more......
  • + 2
 No, he didn't have enough weight on the front wheel, that's why it pushed.
  • + 0
 @panaphonic: On off camber or flat, loose, slippery ground, like that turn noted, too much weight on the front MAKES you loose the front end....
  • + 2
 @thuren: watch the video again.
  • + 2
 @thuren: no it doesn't..
  • + 1
 @thuren: would have to disagree with you there - look at the bit he drifted right before he crashed, and how far forward his weight was to keep the front wheel tracking while the rear went bananas.
  • + 1
 @panaphonic @SintraFreeride @VorsprungSuspension check this vid out it's a good visual. 2:43 is a perfect example. I don't think you can get more centered on the BB or maybe even behind at moments! youtu.be/SLTbnAV6lps?t=163
  • + 1
 @thuren: not sure what you’re looking at but looks like plenty of weight on the front to me. Try this: go rip a cuttie with plenty of weight on the bars, then try it again hanging off the back. Which one works?
  • + 1
 @VorsprungSuspension: Steve, I think we're just going to have to agree to disagree. We just need Sam to comment haha!!
  • + 1
 @VorsprungSuspension: Front tire is not even on the ground hehe!
  • + 0
 Just ride your bike
  • + 8
 I did, it was fun. Then I thought about how much fun it was, and which bits could be funner, put them into a spreadsheet, and here's the results Smile
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