crank length - important?
Morning
Can someone advise me that it doesn't make much of a difference?
I'm running a 54-39 sram red bb30 exogram jobby 175mm on my moda, I want to shift to a compact cos the TDF route made a mess of me.
Ive found not a bad price on a 172.5mm crank which is compact, frame size is 56cm, I think it'll be fine and 2.5mm really wont make much difference?
Am I right?
Thanks!
Can someone advise me that it doesn't make much of a difference?
I'm running a 54-39 sram red bb30 exogram jobby 175mm on my moda, I want to shift to a compact cos the TDF route made a mess of me.
Ive found not a bad price on a 172.5mm crank which is compact, frame size is 56cm, I think it'll be fine and 2.5mm really wont make much difference?
Am I right?
Thanks!
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Comments
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It matters, but some feel that the small 2.5mm length difference isn't enough to feel. Not only the fitting is changed but longer v. shorter crank arms effect how your cadence feels to you. If you spin mostly a shorter crank arm is beneficial, longer crank arms provide a longer lever for those that mash big gears. Both true to a point then the leg length and fit will come in to play.Lets just got for a ride, the heck with all this stuff...0
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You won't feel a thing unless you are Boonen - I have 175 and 172.5 on my bikes and can't tell a jot.
There is also no need to go adjusting seat heights - your different socks probably have more play in them.
Go ahead and fit and be sure to set fir to the old ones.Postby team47b » Sun Jun 28, 2015 11:53 am
De Sisti wrote:
This is one of the silliest threads I've come across.
Recognition at last Matthew, well done!, a justified honoursmithy21 wrote:
He's right you know.0 -
excellant thank you I'll order0
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Matthewfalle wrote:You won't feel a thing unless you are Boonen - I have 175 and 172.5 on my bikes and can't tell a jot.
There is also no need to go adjusting seat heights - your different socks probably have more play in them.
Go ahead and fit and be sure to set fir to the old ones.
Well I'm not Boonen and I can tell the difference.
It's correct that the shorter cranks make it easier to maintain a high cadence. With 170mm cranks my cadence was around 80rpm. With shorter cranks (165mm) it's in the range of 100-110rpm. You will need to adjust your seat height too. If a crank arm is 2.5mm longer or shorter, overall that's a difference of 5mm in the diameter of the pedal stroke. So with fitting longer cranks not only will you be overstretching at the bottom of the stroke, but you'll be over compressing at the top. With shorter cranks fitted, you'll be under extending at the bottom of the stroke.
Once you fit the shorter cranks, if your seat height was correct before, simply raise the seat by 2.5mm to give the correct extension at the bottom of the stroke. You'll find the extra clearance at the top makes it easier to get over the top of the dead spot in the pedal action letting you spin more freely.I ride a bike. Doesn't make me green or a tree hugger. I drive a car too.0 -
It'll be fine.Postby team47b » Sun Jun 28, 2015 11:53 am
De Sisti wrote:
This is one of the silliest threads I've come across.
Recognition at last Matthew, well done!, a justified honoursmithy21 wrote:
He's right you know.0 -
You'll be OK - I run 165 and 170mm across my range of bikes - when I care to notice, my cadence will probably be a little higher on the shorter cranks and seated climbing is marginally more comfortable. Measure your pedal spindle to top of saddle height and keep it the same.Make mine an Italian, with Campagnolo on the side..0
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Yep, he'll probably be fine, I was thinking mostly about knee issues cropping up. I've been stuck on the 175mm length crank arms for so long it isn't even on my screen to change. It isn't broke for me so I ain't going to try and fix it.
any little change in seat height screws over my knees in short order so its a concern for my old, worn out body. As long as I keep things right the knees stay healthy, the alternative is rather unpleasant.
I'm sure he'll figure the solution out which ever length he chooses.Lets just got for a ride, the heck with all this stuff...0 -
It'll be fine. Fit them, ride them, burn the old ones.
No dramas.Postby team47b » Sun Jun 28, 2015 11:53 am
De Sisti wrote:
This is one of the silliest threads I've come across.
Recognition at last Matthew, well done!, a justified honoursmithy21 wrote:
He's right you know.0 -
Son's rescue bike has a square taper Veloce crankset. Well the drive side is anyway. The non-drive side has a mis-matched crank of a more industrial design, it could even be a component from a Russian tractor. Anyway, the two cranks are different lengths, but I can't tell when I ride the thing. I'm too busy relearning to use the downtube shifters.0
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From the many many times this has been discussed before the only logical conclusions is that some notice some don't - personally I noticed a very big difference (for the better as I like to spin) moving from 175 to 172.5 but ...0
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As a technical test of this I just took N1 and N2 bikes for a spin.
Same seat heights, saddles, bar heights, widths and pedals. Same gearing front and rear. Everything the same.
N1 has 172.5. N2 has 175. no real reason why I must have got one cheap in the sales or given to me or something.
Anyhow, 2 x 25 mile loop, same roads, same conditions. I'm a very ex Cat 1 racer so alright but nothing special.
Could I feel any difference? Could I buggery.
But that's just me.Postby team47b » Sun Jun 28, 2015 11:53 am
De Sisti wrote:
This is one of the silliest threads I've come across.
Recognition at last Matthew, well done!, a justified honoursmithy21 wrote:
He's right you know.0
