172.5 cranks vs 170

smoggysteve

mrushton wrote:

There was a bike fitting conference recently where (I think) it was scientifically proven that crank length doesn't make a difference. Prob. more info via Cyclefit and their twitter feed from that conference. Poss. the route to go down is shims/wedges/footbeds which cyclefit do also Adrian Timmis(?) in Derby is spoken of well. Trek are tutored by Cyclefit so a Trek store may be able to help.

If everyones foot is at an equal height at the bottom of a pedal stroke, when at the top, the length of the cranks effect how high you knee comes. If you are tall it has little effect, but if you are a shorter person is has a bigger effect on the top of your power stroke. bringing you knees too high is less efficient as you pedal.

Think of it as trying to climb stairs. smaller ones are easy. try climbing stairs where you have to bring your knees higher for each step. Its essentially the same movement. raising the leg to put a downwards force. If you crank or step is too long you lose momentum each time you raise you knee for the next stroke or step. The shorter your legs the bigger effect it has on you.

bernithebiker

Agree with Smoggy.

If crank length doesn't make any difference, then think about extrapolating to the extremes; 5'6 guy on 185mm cranks, or 6'3 guy on 160mm cranks.

There would be a massive difference in those two riders' hip angles.

Or if it makes no difference, then why don't we all use 200mm cranks? More leverage after all?

I think it's an easy trap to fall into - "longer cranks must be better due to better leverage". But if your legs are unable to put the power down as efficiently with long cranks, then you've gained nothing.

I find that easy improvements in power and speed can be had by upping your cadence. And shorter cranks are conducive to this.

marshall_a

what peddals are you using and are they setup as out of the box?

I've one leg slightly shorter and find it rotates abit more than the other while pedaling. If I have the tention on the pedal too high then I also get a pain in the outer part of the knee after an hour or more, as my leg is fighting the resistance of the self centering, too loose and I'm forever unclipping. I've not tried wedges so can't comment on that, just what works for me. I'm also sentive on saddle height, which can cause calf or quad faigue depending if it goes up or down.

KateS

To answer the above I have Look Keo Classic Pedals with grey cleats and I've set them on the lowest resistance setting. I've now got my new chain set on the bike with the 170 cranks, all working nicely. unfortunately I can't try it out too much due to doing something else to my knee after pushing a bit too much a few weeks ago. My knee seemed to need to "click" anytime I crouched down after my ride. Eventually it worryingly went twang and really hurt but the "needing to click" feeling went now it has been sore since...think I need to maybe go back to the Docs to enquire about some proper physio...and think of another bike fit. Any experience of Specialized Body Fit vs Retul? I have both options nearby. I've seen the not so favourable post about Reutul on here!

Wirral_paul

I had similar problems for ages which were solved through cleat wedges (i think i'm deformed as i needed a full 3deg each side!). Do you wear out the soles of your shoes on either the inside or outside as a matter of interest? That may give a clue as to whats going on

KateS

Yes I do, I wear out the inside, someone else said that so definitely going to look into wedges...seen some that specialized do that go in the shoe, might start with that...

Wirral_paul

Suggests to me that you are "Valgus" and so need to look at angling the foot inwards a little. I am opposite "varus" and wear out the outside edge of my shoes. Its something that really should be looked at professionally though.

http://www.thebikebutler.com/bike_fitting/knee.html

mamba80

Having seen my GF go through all this with her knees, I would suggest you need to look at cleat position first and maybe a dif pedal system, such as Speedplay the higher end model allows for a fully adjustable cleat position but it does need careful set up, esp realise angles and the Q factor, basically how far apart the cleats are in relation to BB, too far in or out can put extra strain on knees, LOOK pedals don't have a lot of adjustment here, SpeedPlay come in dif spindle lengths, be aware that SP will need a lower seat height as they have a shallower cleat & pedal height.

If it is cleat related, the injury you have will have to heal first, before you ll get the full benefit.

the only person I know of who can set these things up properly is RIDE in Plymouth but I guess that is too far away, he is also part of 3sixty performance, which has a sports injury specialist in with them.

Crank length to 165 helped slightly as has extensive physio but everyones condition is different, so what works for one might not work for you.

Slo Mo Jones

brettjmcc wrote:

DiscoBoy wrote:

KateS wrote:

Great advice everyone! Taking note of all of this, will certainly check out shims and wedges, especially the in shoe ones, sounds an easy why to try. Yes been thinking of trying another fit...the fitter did video from the front buy I messed with my cleats since anyway! A second opinion can't harm. I have a Specialized concept store by me and was wondering about their Body Geometry fitting services...anyone had any experience of this?

If you're anywhere near a Retul centre, go for that

I would say go to a good Retul fitter that you can ask people about. I had one done and have since undone 75% of what he did. I ended up in more pain. I personally think Retul with all it science needs to be balanced with experience as well. My fitter was newly trained and did a group of us at work. e have all undone what he did 2 years ago.

KateS, just for reference I am 5'7" and run 172.5 cranks on my road and TT bike. I got back into cycling 4 years ago after not doing it for over 10 years. The bike came with 172.5, so I haven't known any different. As mentioned above the only time I have had knee trouble was over trraining for Paris to London and it turned out to be my right calf muscle being tighter than a very tight thing that had been tightened by Sir Tightens-a-lot

That's because bike fits are hokum, no?

HenryTheHoover

R.e. Cranks I would think 170 cranks would be better for you than 172.5 based mostly from the fact I prefer my 170mm crankset to my 175mm one with an inseam of 33". I feel like I am winding a crank at 175 rather than spinning at 170.

Picking up on other stuff posted it sounds like your knee / s might be collapsing in a bit. Cleat wedges will help here on the bike. It is worth considering getting an assessment off the bike from a physio though. You may need to strengthen specific muscles to correct some issues which wedging your cleats alone might mask.

Stretching can be nice to help flexibility and help you feel loose but it will not correct any issues. Only specific strengthening will do that.

ai_1

Do your current pedals allow much float?
I particularly like Speedplay Zero pedals as they have loads of float available if you want it with virtually no resistance. I'm pretty sure this helped resolve my knee problems but they're really comfortable regardless. Prior to that I used Shimano SPD-SLs which I think are somewhat similar to Loo Keo Classics.

rayjay

Try the Red Cleats ,they allow more float. I use them with my Keo's

They could help with any Knee issues you have.

I ride with 170 cranks. I'm nearly 6 foot tall. I don't think that is the problem.

Give yourself time to adjust to a new position.

Personally I think being stretched out a bit is better. Lower at the front, higher at the back otherwise you may as well put wheels on your fav comfy chair.

Grill

170 cranks are more aero