Originally Posted by
chaadster
Ah, I see.
You may be right about the frame flex, particularly in regards to the chain keeper rub. I tend to think that when it comes to the lack of responsiveness under pedal input, however, that the tiny rear triangle and short stays are probably not flexing, and that the cranks are at fault in that case.
that said, I'm not an engineer, and you may be right. Since I'm not averse to putting some money int this bike, good process suggsts that I go after the obvious, low hanging fruit, and there's no doubt in my mind that the crank and chainring are flexy, and that pedaling would feel better if they weren't.
I think one of those $50 Lasco cranks that are often indicated for fixies would be stiffer than the stock Dahon crank, so if I can find one in the appropriate 170 length, I'll probably throw down for one of those and see. I'd try a Litepro as posted earlier, but I really just want silver.
oh, and yes, no doubt changing pedals would help, too; considering some MKS quick release types
Lack of responsiveness has a lot to do with the stiffness of the bottom bracket. Just observe the latest race bikes and guess what they have -- ALL oversized bottom brackets; they look so extremely massive compared to anything you can find on a folding bike or the older style road bikes, like that on my Trek 5000. You will find more bang for the buck there.
Having said that and unless you are willing to pay a large sum of money, most cranks are already stiff enough. Unless you want to pay something like $500 for a pair Rene Herse cranks from Compass Cycles, you are just wasting your money on something you probably won't give you a significant benefit.
Lastly, frame design also has something to do with the stiffness involved. If you want something really stiff that promotes acceleration like sprints and in crits, then a really stiff bike that does not flex very much. However, without give the ride will be also very stiff as well. Ultimately, you need to choose between frame flex or stiffness for acceleration. There is a difference between my Mu Sl that is stiff and really rough and my Dahon Speed Duo which is slightly flexy and more comfortable. The Mu SL is fast, but the Speed is not as responsive with equal quality cranksets.
In summary, make absolutely sure that your crank bolts are tightened and the cups are torqued correctly with a tool up to correct specs and not by hand! Sometimes loose cups and bolts can attribute to pedal flexing. It's a common problem when you ride a lot especially when the previous mechanic only hand tightened them!
Hope this helps.