On an extra large road bike that is?

Thanks. 🙂

Crank length does make a difference regardless of bike size. May need a bit more info for a better answer.

Thanks. Just curious really, my son had a bike fit done and his Planet X carbon has 172.5mm cranks. Person seemed surprised at the length.

Is that not normal for the frame size? It’s not something I’ve ever paid attention to!

172.5 is pretty much standard on road cranks

OK thanks. 🙂

Most XL bikes come with 175mm cranks I’d have thought. 172.5mm is on the sorter side, but it doest make much difference. I’m nearly 6’3″ and have used both 172.5mm and 175mm cranks with no ill effect.

It does differ from manufacturer. I would expect getting towards the upper sizes, the cranks would go up to 175mm.

For example this is how Genesis size the cranks, on everyone’s favourite bike, the Croix De Fer:

Thanks chaps. Jamie – I did have a peek at the Genesis website to find out what size I’m using. Unable, however, to find the size on my roadie.

The bike fit person presumably thought they should have been 175mm. You learn something every day!

Pretty much all down to personal preference. Thinking is that longer cranks give you more leverage, and shorter cranks are easier to spin a lower gear. Got 175, 172.5 and 170 crank sets fitted on various bikes for different purposes and find it does make a difference for me. YMMV.

From the many “what crank length?” threads that I’ve read on here:

Some posted that they ride cranks of differing length, and can’t tell the difference at all. A few of them even had right and left cranks that were different on the same bike but didn’t realize it. 😳

Other folks said that they rode different crank lengths and could tell the difference, but it didn’t create a problem for them.

A few people say that they have had knee or other problems when running longer cranks, and that the problems were solved by going to shorter cranks. Shorter cranks mean that your legs go through a smaller range of motion, so it does make sense.

I can’t recall anyone that said that they had pain or other problems caused by cranks being too short, though.

Sheldon Brown has a bit of wisdom…

http://sheldonbrown.com/cranks.html

Im one of the folk that got knee pain from the top of the rotation overbending my knee, moved from 175 to 180 then most happy on 165,

Sheldon suggests the supposed leverage gain is negated by being able to change gear,,,

All shimano cranks are the same length, the hole for the pedals however is either nearer or further from the end

Assuming road bike rather than TT bike. TT/Tri is all about the short cranks at the moment.

Is that true rocketdog? Amusing if it is as some people claim better ground clearance as one of the advantages of shorter cranks.

Is that true rocketdog? Amusing if it is as some people claim better ground clearance as one of the advantages of shorter cranks.

And the word “gullible” isn’t in the dictionary.

Is that true rocketdog? Amusing if it is as some people claim better ground clearance as one of the advantages of shorter cranks.

Longer cranks will still make your pedals closer to the ground. Did you think people were worried about stubbing the end of their crank into the road?

Sorry, it’s early, only just woken up. Having fitted 180 and 165 xt cranks for people, I’m pretty sure I’d have noticed the extra half inch or so hanging off the end.

Perhaps first thing in the morning, I should focus on getting ready for work rather than messing about on here. 😳

As rickmeister suggests, Sheldon Brown is the source for your question.

As for differing length cranks on the same bike, I guess if you had one leg shorter than the other…

TT/Tri is all about the short cranks at the moment.

So it makes a difference for one bike/type of riding but not the rest?

Tells me all I need to know.

Sheldon suggests the supposed leverage gain is negated by being able to change gear,,,

As ever, he’s right.
Power output is work done over time. If you spin more than mash, you’ll turn a shorter crank a little faster/easier than a long one, at a lower gear. It’s all minor stuff but it helps.

The chart Jamie posted is fairly normal, averaging crank lengths to bike sizes to match leg length. But I’m 6’1″ and ride 170s on road or a cx type of mix-use road bike. On my SS I prefer a 175 but can still spin that if needed. So it’s only a guide.

I’m clearly a luddite, as I’ve got 2 different bikes with different length cranks & I can’t tell the difference.

Doesn’t seem to make any difference to me.

Obviously going between extremes make a big difference – 145 to 170 on the tandem. But in general, one cm isn’t going to be noticed. 170 to 180 is a 5% increase. Average UK height is 178cm, so if one scales, he’d need to be 188cm for them to be scaled. I’m 179 and ride 165 on track and 175 on mtb. It helps with spinning above 130rpm, but not otherwise.

Saddle position relative to BB rather than crank length are more important determinants of knee pain, in my opinion.

Tells me all I need to know.

😆 Are they still on 19mm tyres?

My all purpose bike, built from bits blagged off mates, had 175mm cranks, currently on 170mm and they /seem/ slightly easier on the legs.

Mind you, as above, my SS had for a while 175 and 172.5mm cranks (L & R different) and I didn’t really notice..

Assuming road bike rather than TT bike. TT/Tri is all about the short cranks at the moment.

So it makes a difference for one bike/type of riding but not the rest?
Tells me all I need to know.

Made this change recently. Going from 175 to 170 actually made a big difference for me on the TT bike, but that was as much being a more comfortable range of movement in a better TT position than spinning and leverage. Considering 165 cranks.

Prefer long cranks on mtb though on a 1×10 setup. And somewhere in the middle for the road bikes.

Saddle position relative to BB rather than crank length are more important determinants of knee pain, in my opinion.

That can only be true in terms of fore and aft position. But it will affect saddle height. the difference in saddle height between a 170 and 175mm crank will need the saddle 5mm lower, but at the top of pedal rotation your knee is going to 10mm above where it would be on the 170crank.
When you consider any bike set-up advice, saddle height adjustment should be done in very small increments.

In saying that, i think alot comes done to fashion/trends, certainly in mtbing its less common to see anything other than 175mm, and i think traditionally 170mm was the norm on most road bikes.

Saddle position relative to BB rather than crank length are more important determinants of knee pain, in my opinion.

That can only be true in terms of fore and aft position. But it will affect saddle height. the difference in saddle height between a 170 and 175mm crank will need the saddle 5mm lower, but at the top of pedal rotation your knee is going to 10mm above where it would be on the 170crank.
When you consider any bike set-up advice, saddle height adjustment should be done in very small increments.

In saying that, i think alot comes done to fashion/trends, certainly in mtbing its less common to see anything other than 175mm, and i think traditionally 170mm was the norm on most road bikes.

Is that true rocketdog? Amusing if it is as some people claim better ground clearance as one of the advantages of shorter cranks.

It is true, but don’t forget the pedals stick out so the nearer the end of the crank arm they sit the less clearance you’ll get when leaning over, but your feet shouldn’t be in a position to catch the ground on a corner anyway