Crank Length

shinsplint

Hi guys,

I'm just over 6ft with longish legs and have always used 172.5 cranks. I have seen a good deal on some slightly shorter 170 cranks which im tempted by. Is there likely to be a noticable difference?

Thanks.

Grill

No.

on-yer-bike

I heard from a bike fitter there is a trend towards shorter cranks. He advised me to go shorter but im not in a hurry to change 3 chainsets.

shinsplint

Cheers chaps that will do for me

CYCLESPORT1

Stick to 172.5

Matthewfalle

I run170, 172.5 and 175 and notice absolutely no difference at all.

Purchase away my fine fellow.

cougie

Back in Lemonds day I think it was the trend was to go longer so I did.
Now I just ride whatever the bike comes with.

I even spent a few months riding with odd sized cranks - no ill effects and you couldn't tell.

ai_1

My original bike came with 175mm cranks. They worked just fine for me.
My new bike came with 172.5mm cranks. I could claim to notice a very slight perceptible difference but it could as easily be my imagination. I then switched cranks when replacing the worn-out chainrings on my old bike and it's now fitted with 170mm cranks. Again, any difference is minimal. I think the slight reduced height of my knee at the top of the stroke is just about noticeable when I'm in an aggressive position but I doubt I'd notice if I wasn't aware I'd changed the cranks. As before it's such a small change that my perception of it could as easily be my imaginary. In a back to back blind test I'm not at all confident I could tell which was which. In summary: I've tried 170, 172.5 and 175 and there's bugger all difference - I wouldn't worry about it at all.

shinsplint

Cheers chaps

alex222

Cyclist magazine had an article a while back on crank length. Suggestion was that shorter crank lengths were more efficient.

I have 172.5 on one bike and 175 on the other and I can't tell the difference.

dj58

I can feel a difference between 175, 172.5 and 170mm cranks, buy whatever you feel comfortable with.

js14

If you have big feet, a shorter crank length gives more clearance between your toes and the front wheel, which helps if you wobble going up mountains like me. I also find it is easier to keep a high cadence on a 165 mm crank versus a 175 mm crank, but maybe I am imagining it.

bernithebiker

To those saying no difference then why not go with the shortest cranks you can?

a) better ground clearance
b) a tad lighter
c) more saddle height flexibility
d) less strain on knees, joints....

(And as for the OP, we'd need to know your inseam as your height is immaterial).

Grill

bernithebiker wrote:

To those saying no difference then why not go with the shortest cranks you can?

a) better ground clearance
b) a tad lighter
c) more saddle height flexibility
d) less strain on knees, joints....

(And as for the OP, we'd need to know your inseam as your height is immaterial).

Because we're talking 2.5mm here, not 25mm.

Plus shorter cranks aren't as good for TT's as many claim. Yes, there can be a small aero benefit and they can help those who have issues with knees in their chest, but the higher overall body position is detrimental. Good for some, not great for others. Ride what you're comfortable with.

ai_1

Grill wrote:

bernithebiker wrote:

To those saying no difference then why not go with the shortest cranks you can?

a) better ground clearance
b) a tad lighter
c) more saddle height flexibility
d) less strain on knees, joints....

(And as for the OP, we'd need to know your inseam as your height is immaterial).

Because we're talking 2.5mm here, not 25mm.

Plus shorter cranks aren't as good for TT's as many claim. Yes, there can be a small aero benefit and they can help those who have issues with knees in their chest, but the higher overall body position is detrimental. Good for some, not great for others. Ride what you're comfortable with.

Yeah, I'm not convinced that shorter is necessarily better. There's undoubtedly an optimum for each person, I doubt it's massively critical and I see no reason to assume it's always smaller than whatever you're already using. In my case I was very happy pushing hard on 175mm cranks for TT like efforts. However I also do multisport events and I went with the smaller 170mm cranks when replacing the chainset because I think the lower knee and thus more open hip angle may leave me in better shape for the run when I get off the bike. Running after a hard cycling effort is not pleasant for the first few minutes and this reportedly can make a small difference. I wouldn't have bothered except I was replacing most of the components anyway.

cycleclinic

I have 170mm to 177.5mm cranks but mostly 175mm. They all feel like cranks to me. Just adjust your seat height a bit if going shorter it wont harm you. The more you look into bike fitting the more it does not seem based on peered reviewed research like conventional science but it moves with trends a bit like fashion. It goes in circles. A bit like oval chainrings then have been going in and out of fashion since the 1890's and no one has manged to prove beyond doubt they improve pedalling efficency.

Bike fitting is based on rider feedback and so is the research. How a rider feels is subjective and make objective research difficult. It is easy to show shorther cranks chnage the angle your hip opens too but what the rider feels will vary from roder to rider and trying to account for the pleado effect will be hard To impossible. You can measure power outputs to see if that makes a difference but are the studies using statisicallh significant samples, often they dont.

bernithebiker

If it really makes no difference, you have to wonder why the crank makers, Specialized, Shimano, et al. investing in multiple moulds, etc. to produce them.

Would be far simpler and cheaper for them to just make 172.5's. I would guesstimate it would knock a good 10% off crank prices.

Macktrance

I had been an experienced mtbkr in the past and know how a well set up bike should feel. Recently got back into the sport with a trance, however always felt like the wheels were full of lead. After 10 thousand adjustments, wider bars, shorter stems, saddle adjustments, it still felt like I was always 2 gears higher than I could push (uphill or down). I came to realise that on those nasty lowest gear climbs I was bobbing very hard and pedalling had a huge dead spot at the top. Pushing the pedal over the top was a conscious effort, and the lungs would blow out very easily. Crank length then became a solution. After reading all there is on the internet regarding the subject I bit the bullet and went from 175s to 165s!

My advice is this... 2 people may be 6 feet tall, but their helmet sizes will be different, as may we'll be their shoe size. They probably like different handle bar widths and saddle heights and so on and so on..... Measuring ligaments and applying mathematical calculations to find crank length makes as much sense as your nasal passage determining helmet size..... It's just silly. The right crank for you... Is the right crank for YOU! Longer will not give you more leverage, it will only give you an improper fit. Otherwise we'd all be running 250mm cranks for the most awesomeness of power! If you have more power with 175s it's because they suit you! Not because their longer.

I have now found with 165s I can climb the same steep hills one to two gears higher. My cadence hasn't increased hugely but, I can pedal smoothly the entire stroke. There is no more bobbing with each stroke and I find I will speed up on the flatter part of the climbs rather than taking the flatter part as a rest. The lungs just don't blow out anymore. It feels to me like I have much more power even though the cranks are shorter. And on the downhill, power to burn! Torque is now on my side. Out of the saddle, I can put power to the ground like never before. Two or three pedals and I'm back up to speed, almost pulling wheelies... It's awesome.

If you think your feeling that you could be having any of the same issues, don't be scared. I was told by all when shopping 165s is too short. Find the right crank for you! I'm 5' 10" with a 32 inseem and all charts and calculations say I should run about a 170. I couldn't be happier, give it a go, I'm now really amped with my bike and want to ride every day.

964cup

I've ended up spending a fair bit of money standardising all my bikes at 175; originally I had three (of 7) with 172.5, and found I kept getting knee problems on those bikes. YMMV, and I know it's odd that I went *longer* to fix knee problems. I ride a fairly high cadence, too.

bristolpete

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19648948#p19648948]Macktrance[/url] wrote:

I had been an experienced mtbkr in the past and know how a well set up bike should feel. Recently got back into the sport with a trance, however always felt like the wheels were full of lead. After 10 thousand adjustments, wider bars, shorter stems, saddle adjustments, it still felt like I was always 2 gears higher than I could push (uphill or down). I came to realise that on those nasty lowest gear climbs I was bobbing very hard and pedalling had a huge dead spot at the top. Pushing the pedal over the top was a conscious effort, and the lungs would blow out very easily. Crank length then became a solution. After reading all there is on the internet regarding the subject I bit the bullet and went from 175s to 165s!

My advice is this... 2 people may be 6 feet tall, but their helmet sizes will be different, as may we'll be their shoe size. They probably like different handle bar widths and saddle heights and so on and so on..... Measuring ligaments and applying mathematical calculations to find crank length makes as much sense as your nasal passage determining helmet size..... It's just silly. The right crank for you... Is the right crank for YOU! Longer will not give you more leverage, it will only give you an improper fit. Otherwise we'd all be running 250mm cranks for the most awesomeness of power! If you have more power with 175s it's because they suit you! Not because their longer.

I have now found with 165s I can climb the same steep hills one to two gears higher. My cadence hasn't increased hugely but, I can pedal smoothly the entire stroke. There is no more bobbing with each stroke and I find I will speed up on the flatter part of the climbs rather than taking the flatter part as a rest. The lungs just don't blow out anymore. It feels to me like I have much more power even though the cranks are shorter. And on the downhill, power to burn! Torque is now on my side. Out of the saddle, I can put power to the ground like never before. Two or three pedals and I'm back up to speed, almost pulling wheelies... It's awesome.

If you think your feeling that you could be having any of the same issues, don't be scared. I was told by all when shopping 165s is too short. Find the right crank for you! I'm 5' 10" with a 32 inseem and all charts and calculations say I should run about a 170. I couldn't be happier, give it a go, I'm now really amped with my bike and want to ride every day.

Great post - have been saying this for years !