84.5 time .216 means you should be riding 182.5 crank lengths.



Dave

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Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep

Get em...I bet you cant feel any change.

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What if the Hokey Pokey is what it is all about?

I'm with record on this one. I have 175s on the road bike and 172.5. I cant tell the difference.

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- Nick
Now that I know some of you guys look through the special needs bags for kicks, I'm gonna put some really weird stuff in mine. I can see it now. "What the heck was he going to do with a family pack of KFC chicken, a football helmet full of peanut butter, a 12 inch rubber dildo, and naked pictures of Bea Arthur?"

I'll second (or third) that. I've got 175's on the road bike. I put 172.5's on the tri bike thinking it would help my "spinning". Can't tell a bit of difference.

This is my first year in the sport and started out with 172.5 totalled my bike and then purchased a bike with 175. I am about as tall as you and I have no problems at all. I was told that if you feel like you are being pulled forward during you pedal stroke they are too long. I think that if it is too long you could truely tell. As with any change, you need to allow time to adapt. Even if it does feel funny at first once you get used to it I think you will be glad you switched.

Hmmm. The crank length question.

Lennard Zinn, Technical Editor for both Velo-News and Inside Triathlon (at one time or another) did a relatively exhaustive investigation into techniques for determining optimal crank length.

What he discovered, if I am recalling this correctly, is that it is nearly impossible to use a calculation based on just one factor (such as inseam or femur length) to arrive at a crank length that the athletes usually feels is optimal.

There seems to be some subtle convergence of factors including (perhaps) pedalling frequency and speed, pedal selection, length of the related limbs (tibia and femur mostly, but maybe even torso also) and a few other enigmatic factors.

There seems to be a consensus among some that the best crank length for you is arrived at through experimentation. I would agree with that.

I've tried 170mm, 172.5mm, 175mm and 177.5mm and settled on 175's for everything. I have done some bouncing back and forth and going to 172.5's just didn't feel optimal. When I tried 177.5's I slid forward on the saddle chronically.

Perhaps a reasonable syptom of cranks that are too long is that you do find yourself pulling forward on the saddle from your normal posture (which hopefully is already optimal).

Maybe a more systematic, albeit time consuming and pricey, technique is to use a power meter such and an HRM and look at the work output per heartrate (exertion) input.

-Or you just try the and see how they work for you over time. You will likely develop a reasonable sense if they are an improvement.

Good luck!

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Tom Demerly
The Tri Shop.com

But, the question is have you tried longer ones? I know I have ridden 175's my whole life, since that is all the mfgs basically make. I have a 94 cm inseam. So, I had been using 200mm's the last few weeks. Felt no difference. But I have yet to talk to one tall person who has gone to longer cranks that would never go back. So, try up to 182.5, and see how they feel. Only you can tell what is right for you!!



Dave

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Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep

Do it... you won't find any difference unless it becomes some sort of self-fulfilling prophecy (i.e. you think you will so you do...)... I'd love to get some of those people who claim they can spin better with one or another and give them blind tests with different length cranks... I'll bet they won't be able to distinguish one from another...

Thanks everyone. I will give them a shot.

your cadence will going down ...

just gotta try it to see, I wish they made 172.5 in mountain bike cranks:( My cadence is noticeable more sluggish on my mountain bike with 175mm than my road and tri with 172.5mm. I have about a 30" inseam

You can't tell a difference between 175 and 200 mm crank arms? Are you riding in your sleep?

They do make 172.5 mountain in XTR, also Tune, Extra-lite, and FRM that I know of. I use XTR 172.5's on my bikes.

As far as optimal length, 175 is fine as long as you have room at the top of the pedal stroke. If your aero (or drops on road bike) position is tight- another 2.5 mm could bring your knees up into your chest.

I’ve used 170, 172.5, and 175 cranks on my road and TT bikes. I’ve recently been experimenting with swapping back and forth between 172.5 and 175 on my TT bike. I notice the difference, but it’s not dramatic either, nor can I definitively point to a quantifiable difference in performance, although I do subjectively have a preference. Some people notice it, some don’t. I don’t think it’s fair for others to proclaim in a dogmatic manner that it can’t be felt; some people are more attuned and sensitive to small changes in fit and position, and others aren’t. My wife is a former ultramarathon racer, who has had years where she rode 15-20k miles, and she’s sensitive to tiny changes in position.



Subjectively, I have a definite preference for 172.5s over 170s (I’m 5’9”), I’ve generally felt that it was a close call between the 172.5s and the 175s, but I’ve decided to stay with the 172.5s on my tri bike because it seems to work just a bit better with my aero position; with the longer crank, the saddle goes down 2.5 mm and the knee is 2.5 mm higher at the top, meaning I’ve got to add a spacer under the stem to compensate.

Hello, One interesting aside to the Zinn article is that when all was said and done he rode his usual bike for quite some time before finding out that he had left two different cranks lengths on the bike. Didn't notice a thing.



Styrrell

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Styrrell

I'm not too certain that you can't feel the difference in 2.5mm... I changed from 170mm to 172.5mm on my TT/Tri bike, but kept the 170 on the road... Felt much better for some reason on the tri bike so I switched the road to 172.5... Felt as if I could keep a better circle and less of an egg-shape pattern... If you can't the difference, then chances are it didn't make a different for you...

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"Suddenly the thought struck me. My floor is someone elses ceiling"-Nils Ferlin

In 1992 I was in a bike/car collision. Tore up some of the connective tissue in my lower back. I had been riding 175s. A lot of the back pain went away when I started using 170s. Couldn't tell the difference cadence or powerwise but could feel a difference in the lower back between 170, 172.5 and 175 crank arm lengths. I'm back up to 175s but it took awhile.

Some other reading:

http://www.nettally.com/palmk/crankset.html

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Jay

[reply]I'd love to get some of those people who claim they can spin better with one or another and give them blind tests with different length cranks... I'll bet they won't be able to distinguish one from another...[/reply]

I have a 35" inseam, switched to 175s from 172.5 after reading Zinn's articles (he makes custom 180 and up cranks). I can't say I can distinguish between them when riding, but I do go faster.. as a matter of measured fact. Perhaps the upgrade from Exage 172.5s to Ultegra 175s may have had an impact too. Someday I'll drop the money for 180s, but there are several other upgrades I think will be more useful.

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"It is a good feeling for old men who have begun to fear failure, any sort of failure, to set a schedule for exercise and stick to it. If an aging man can run a distance of three miles, for instance, he knows that whatever his other failures may be, he is not completely wasted away." Romain Gary, SI interview