There is more to just slapping on some new cranks and going for a ride. you cannot disrupt the relationship between you knee and spindle of the pedal. Seat height is also effected if changing lengths. Also note the relationship between your foot and the spindle. further back gives you more flexion as a spinner but more foot on the spindle gives you more power. which one are you. I have gone so far as x-rayed my feet in my shoes attached to the cleats to see exactly where the spindle is in relation to the "ball" of my foot. Ever try this one Cerveloguy?

I agree with the chiropractor: You must respect the distanc from the top/center of the saddle to the location at which the metatarsil joint of the foot rests over the pedals spindle. This is very important. It is not determined so much by perfromance requirements or "comfort" but by biomechanics. Personally, I am married to 175mm cranks on everything and am pretty fussy about maintaining precise saddle height (actual linear distance regardless of relative angle) from bike to bike. Despite a number of fairly serious knee surgeries I have no problems.

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Tom Demerly
The Tri Shop.com

Just wondering but I get it. I always get paranoid when I feel the slightest twitch anywhere. I know better but always like to hear it as well. thankyou.

Tom--where you been vacation again? Did you see my email I sent you on Sat. to the shop?

For your optimum theoretical crank size http://www.xsystems.co.uk/...ngth_calculator.html

There are also some charts on the net that show slightly different results.

Do you find this crank length calculator gives a value a little shorter than what most people actually ride? It calculates me at less than 170. I have had 2 fitters that tell me I should be on 175, all the bikes my general size come with 175 standard, but, I feel best on 172.5

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Quid quid latine dictum sit altum videtur
(That which is said in Latin sounds profound)

I thought the same thing. In fact there is chart on the net somewhere that gives me a size bigger than does the calculator. I think it's more accurate. I'll have to try to find it.

I disagree somewhat. I don't believe that changing crank length necessarily means you should be changing seat height. If you put 5 mm longer cranks on a bike, for example, and you lower the seat 5 mm to to keep your extension the same, your leg is now travelling 10 mm higher at the top of the stroke. I personally think that's worse for your knees than leaving your saddle where it is and splitting the difference. I'm extremely finicky about my saddle position, and I always found it harder to get used to a crank arm change accompanied by a seat height change than just the crank arm change alone. IMHO, of course.

Ahhh, yeah, right...

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Tom Demerly
The Tri Shop.com

I was dealing with my car. It was the very definition of sucking. Amazing. Here's a tip: If you wreck a car at the airport put a kilo of C4 under it, stick a cap in it send it into orbit. It will be cheaper to replace it with a new car than get it out of impound.

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Tom Demerly
The Tri Shop.com