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goughy

Shorter cranks, anybody gone to them or using them?

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So at the end of my bike fit last year the guy suggested I could look at shorter cranks for my bike for my knees (must move the seat height up).  I currently use 172.5mm cranks on both my bikes, and am wondering if anyone has gone from longer to shorter cranks, and what was the difference like?  Or will I not really notice anything (I'm not all that self aware).  He suggested 165mm cranks.

Can anyone explain how the change in crank length will help my knees.  It's not something we really discussed, he just mentioned it.

Both my bikes are 10 speed, but does it matter if I get 11 speed cranks?  It seems most of the 105 or maybe ultegra stuff is 11 speed...

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I went from 175mm to 172.5 & noticed the difference in the hills. 

I would like to try 170mm cranks but sure they would make enough difference to justify the cost. 

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My power meter died last year and When I replaced it I got some new cranks.  Went to 165.  This allowed me to get a little lower on the aero bars without closing my hip angle at all.   I was coming back from a period of very low training and bad fitness so I have no idea how it felt cause I was so unfit when they got put on.

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36 minutes ago, Bored@work said:

I went from 175mm to 172.5 & noticed the difference in the hills. 

Don't say that..... I'm finally getting back to riding a bit more, in particular with the tougher group, and they're all about the hills.  And I'm already a long way last!

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Didn't know they made them that short!

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My bride has just gone from 165 to 155 on her TT and reports a massive difference. Seems to engage all leg muscle groups now, stops her 'toeing' and keeps her knees straight up and over. Someone also mentioned, but it has opened up her hip angle nicely & gets her into a much more aero position.

I am about to go from 172.5 to 170 myself, purely to help the longevity of my knees. 

Have a look around, but there are articles on lab tests done that show there was no reduction in power output through different crank lengths. For me the longer you can be comfortable on the bike, the better. Just remember to raise the seat by the same reduction in crank length. 

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I went from 172.5 to 165mm on the TT bike for a few reasons, namely:

I ride a 56cm P3 but I'm only 178cm. Main reason for this was I needed the stack at the front end. My back needs to be stretched out but I don't need to be 'low'. This means compromises with seat posts height ( I have very little showing for a TT bike).

The FSA Gossamer Pro crankset that came with the bike seemed to be made of processed cheese. The rest of the group was Ultegra and Shimano made a 165mm.

Going shorter allowed me to raise the saddle a little and move it backwards without over extending my legs. 

I got used to it in no time. Not sure what it helps with cycling wise or running but I'm riding and running ok at the moment and that syncs with what I've read about short cranks but my decision was more mechanical/fit based than performance.

Ive had 172.5 and 175s on road bikes and not noticed any difference between the two to be honest.

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I rate my 165s on the TT @ 183cm. My wife just got 155. 

 

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It would be interesting to get Alex to comment on this - he'd have the research on it - over the years I have tried everything from 170mm up to 180mm and found no difference in times - I have settled on 175mm at 175cm height - knees OK after 30yrs of all sorts of lengths B)

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I think weve previously talked crank length, I cant find it. Maybe it disappeared in Roxii-Improvement-Incident or Im crap at searching 🤔

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Shorter cranks are a pretty obvious choice for TT, it's basic maths.

When you go shorter i.e. from 172.5 to 165mm, you can move your saddle up + forward a bit, making your back flatter in relation to the front == usually more aero.

You can then decide if you want to keep the front the same so hip angle is bigger == arguably(?) leads to better running off the bike.

Or you can lower your front end to keep hip angle as it was previously == usually more aero.

I've been riding 165mm cranks for a few years now (moved from standard 172.5mm).

Did I notice the difference? Nope. But I can't argue with basic maths.

 

Edited by Rog
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2 hours ago, AP said:

It would be interesting to get Alex to comment on this - he'd have the research on it

He was who I was thinking of when I wrote the post.

I can see the benefits some of you are talking about with regards to TT'ing.  I hadn't really thought of that, and the change would be on both bikes, not just TT.  Purely because it was a suggestion to help with my knees.  So I'm wondering exactly how shorter cranks would give my knees some relief?

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Years ago I put 167.5s on my TT bike, from 172.5s, which were always too long. Prefer the shorter, and should have gone with 165s.  On the road bike  on the long rides 200km  if hills reckon get less knee soreness.

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Got an email back from the guy I had my bike fit with.  He said on the roadie it obviously won't help with hip angle etc as much because my body position doesn't change as dramatically, but he believes reducing the range of motion through the pedal stroke can be of benefit.

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On 3/31/2018 at 2:30 PM, longshot said:

Years ago I put 167.5s on my TT bike, from 172.5s, which were always too long. Prefer the shorter, and should have gone with 165s.  On the road bike  on the long rides 200km  if hills reckon get less knee soreness.

Any reason why you think 165s would have been better? Thinking of going from 172.5s to 165s for TT

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25 minutes ago, imyoungmatt said:

Any reason why you think 165s would have been better? Thinking of going from 172.5s to 165s for TT

because 167.5 is a PITA to get a hold of... 

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For the TT bike I think the extra 5mm pedal to pedal would have given even slightly better body geometry/angles. And I'm 167cm, and probably more the 'right' size - even though the studies which have been quoted in previous threads on crank length show a wide range of crank lengths is ok (IIRC), and I (now) use mostly 170s on road/commuter/MTB bikes. Apparently track riders often use shorter cranks.

There is more 165s around, for sure.

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So.......... I think it's about time I actually did this.  Just trying to work out if I need to replace the BB as well?  I couldn't see anything written on the BB that's on there atm.  The current cranks are SRAM Rival GXP in 50/34.  I want to put on a 105 5800 11sp 52/36 (which should work with my 10sp).  It says the BB needed is a Hollowtech II.  Don't suppose anyone's got a clue for me?  The bike is a Fuji D6 3.0

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Bugger....

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Just watched a vid on bb types - what a cluster **** of systems!!

But 3 or 4 pages along I found one that said I should have an english thread bb.  Just didn't wanna buy something else as well.  Cheap ass wanker I am.

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