Neg Posted December 9, 2012 Share Sorry for the long winded explanation..... but..... When I got my 29er, I sold the drivetrain- crank, cassette, chain front and rear derialures , which were shimano 2x10 and replaced with my older Sram. I was/am Very happy with the 29er but I notice that the cranks are lower than on the 26er and bash allot more than my 26er ever did. I did not want to believe it but this morning was forced to face reality… Now I don’t know if the original cranks arms that came with the 29er were shorter than what I had on the 26er which I moved over after selling the 2x10... Today at Groenkloof, going up the section where those wood discs are laid down next to the rocky incline, I cleared the 1st rocky section and about 1/4th up the next section. When I rode an anthem 26er last week I got almost up the whole section about ¾ the way up. What happened this morning was as I was climbing, my crank arm smashed into rock and the bike came to a sudden, solid halt! Got going again and it happened two or three times after that too… eventually I pushed the 29er where I was still peddling the 26er….Truth be told though, I like the 29er, on normal rides its comfy and for me it feels quicker which helps with my “placebo effect” J and it would be great for me if I could just get that crank higher!So…. Do I sell the Giant and try find something with a higher crank or put shorter cranks on…? I am 1.83m, ride a medium bike and I currently have 175mm (or something like that) XT cranks.What would the implications be with the shorter crank arms, higher seat post and higher riding position? But what would it do to the actual pedaling? Shorter crank more or less torque… higher cadence to get the same speed from current set up…??Im just SO gatvol of smashing the cranks!!!! Link to comment Share on other sites More sharing options...
Mackie Posted December 9, 2012 Share This may be due to shorter crank arms, but most likely the result of different bike geometry, often 29ers have lower BB heights to try and reduce the stand over height of the bike. Link to comment Share on other sites More sharing options...
divernick Posted December 9, 2012 Share If your 29er is a dual sus, check the rear suspension isn't too soft, causing the BB to drop too much.... Link to comment Share on other sites More sharing options...
Neg Posted December 9, 2012 Share My rear Shock is pumped to 215psi. ?? Always has been.Who makes a 29er that has got the geometry correct? i did a search, and not that its scientific proof, but all the 26ers seem to have a BB inline with the axles. all 29er's seem to have a BB about 1"-1.5" lower.... cannot shorten the crank arm by that much Link to comment Share on other sites More sharing options...
Johan Bornman Posted December 9, 2012 Share I'm pretty sure the BB height from the floor will be the same for most MTBs, whether they have large or small wheels. You can't go and nilly-willy fiddle with the heights since it will affect the bike's usability. By that I mean your ability to put a foot out to stop at a stop street - whatever version of that action you'd like to picture. BB height is actually expressed as BB drop - the distance the BB is below the hub height. However, this changes for road bikes, 26ers and 29ers even if technically, they are all equally high. So it is more useful to look at the actual BB height. I would look for the problem elsewhere than the cranks. Crank lengths typically change in 2.5mm or 5mm incremenents and the max difference you'll find between the longest and shortest is 15mm (165mm to 180mm). Your problem is elsewhere, be it talent, luck or suspension. Link to comment Share on other sites More sharing options...
Neg Posted December 9, 2012 Share Thanks Johan, very interesting..... where else could the problem be? as mentioned the rear shock is pumped to 210spi, so there is the recommended 10% sag, push the o ring up, gently climb on as sit, gently climb off so ther is no bouncing, the ring moves down about 10% of total travel- (you taught me this measurement) i have a 175mm crank on at the moment. the 26er anthem has the same crank. when riding Groenkloof, there was not a single bash in close on 100km over 3 rides! with the 29er it bashes every ride, every time... and in the same places, i now get to those spots and approach differently, pedal up to the spot and try have enough momentum to carry me through with the cranks horizontal so it does not bash- i have tested this- With the 26er i am able to pedal over the exact same spot with ease.... not even a hint of crank wanting to bash.... whether im standing or sitting.... same scenario.... so i dont think its luck.... yes, talent it could be... maybe i just dont know how to ride a 29er.... and the suspension is very hard and there is very little bob.... still bashes.... so between talent and suspension.... one of them is lacking... or both..... Link to comment Share on other sites More sharing options...
Johan Bornman Posted December 9, 2012 Share The only way out of this conundrum is via a few simple measurements. BB to floor.Crank end to floor (with crank vertical)Etc. Compare to previous bike. I don't foresee any significant difference but lets measure first, then speculate. Link to comment Share on other sites More sharing options...
Captain Fastbastard Mayhem Posted December 9, 2012 Share What bikes are they? 26er anthem and a? Link to comment Share on other sites More sharing options...
Paul Ruinaard Posted December 9, 2012 Share I have come to accept that on my 29ermthe bb is lower. I have learned to adapt. Riding a specialized Epic dual suspension. Link to comment Share on other sites More sharing options...
covie Posted December 9, 2012 Share I hit pedals a lot less on my rocky element than i ever did on my anthem, myabe its just because i wizened up, but take Johans advise, and if you feel you need something with an adjustable bb, then Rocky mountain, and Morewood have bikes that you can adjust the BB height by the use of a alan key. Link to comment Share on other sites More sharing options...
dalem44 Posted December 9, 2012 Share I have the same problem but with 2 different 26ers. I have ridden extensively on both but since putting on cranks with 175mm arms, I seem to catch every single rock in my path. The other bike has 170mm arms on and I seem to miss every rock. 5mm is not a lot of difference so I gather that it can't be that so I have put it down to bike geometry. One is a recreational frame and the other is a race frame. I presume this could be a problem? Link to comment Share on other sites More sharing options...
Dubber88 Posted December 9, 2012 Share Interestingly I switched from a Spark Medium 26er to a Niner EMD9. I'm hitting rocks probably around 90% less than what I did on my full suspension, with basically all my lines changing at GK to where the 26er would have hit rocks. Both cranks arms were the same length. Also the Scott was a medium and the Niner is a Large. Link to comment Share on other sites More sharing options...
davidlangebaan Posted December 10, 2012 Share I went from a 26" Trance to an Anthem 29er. After hitting the pedals a bit on the first few rides I measured the relative BB heights and the 29er's BB is lower. Which explains it. But I learned to adapt to it as the pros of the 29er outweigh the cons IMO. Link to comment Share on other sites More sharing options...
Neg Posted December 10, 2012 Share My anthem 29er center of BB to floor- 325mm. center of pedal shaft 145mm.The Anthem 26" Center of BB to floor- 345mm. Center of pedal shaft 165mm. both shocks at 200psi-both bikes have XT 175mm crank and 540 SPD spedals. he 29er is lower by 20mm. give or take a few mm for other factors like tire new vs old worn tires etc... So now we move to talent..... when riding the rough rocky up hill, and there is a clear "line" that everyone takes as anywhere else is soccer ball size rocks and there is only one line... how do you get through there with out bashing- knowing that you HAVE to pedal at that point ... do you just accept you are going to bash and break your momentum? because i tried as said with 26 and 29 and the 26 i could pedal through no prob... 29er bashed... So how do you ride it? so now im not so sure that the "pros" of the 29er are worth it if i cannot ride rocky uphills.... because i have to stop pedaling... push through the section and try again... can i buy talent anywhere? what does it cost??? Link to comment Share on other sites More sharing options...
Neg Posted December 10, 2012 Share What bikes are they? 26er anthem and a? Giant Aanthems 26er VS 29er. Link to comment Share on other sites More sharing options...
Captain Fastbastard Mayhem Posted December 10, 2012 Share My anthem 29er center of BB to floor- 325mm. center of pedal shaft 145mm.The Anthem 26" Center of BB to floor- 345mm. Center of pedal shaft 165mm. both shocks at 200psi-both bikes have XT 175mm crank and 540 SPD spedals. he 29er is lower by 20mm. give or take a few mm for other factors like tire new vs old worn tires etc... So now we move to talent..... when riding the rough rocky up hill, and there is a clear "line" that everyone takes as anywhere else is soccer ball size rocks and there is only one line... how do you get through there with out bashing- knowing that you HAVE to pedal at that point ... do you just accept you are going to bash and break your momentum? because i tried as said with 26 and 29 and the 26 i could pedal through no prob... 29er bashed... So how do you ride it? so now im not so sure that the "pros" of the 29er are worth it if i cannot ride rocky uphills.... because i have to stop pedaling... push through the section and try again... can i buy talent anywhere? what does it cost??? You can learn here... https://community.bikehub.co.za/topic/124480-how-would-you-do-it/ Link to comment Share on other sites More sharing options...
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