Anyone know what would happen if you ran a 170 crank set up on my bike instead of the recommended 175 for my leg length???
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Re: Short crank arms on a TT/Tri bike??? [6cuda6]
[ In reply to ]
Well, you'd want to raise your saddle 5mm.
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Some are born to move the world to live their fantasies...
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Some are born to move the world to live their fantasies...
https://triomultisport.com/
http://www.mjolnircycles.com/
Re: Short crank arms on a TT/Tri bike??? [brider]
[ In reply to ]
Don't think that's totally true.
Your foot would be 5mm nearer at 6 oçlock on each stroke but if you raise your saddle your foot will now be 10 mm further away than it used to be at 12 oçlock. Knee angle at 6 oclock is probably more important that at 12 oçlock but the latter may impact on your leverage at the start of each downstroke and should be borne in mind.
My understanding was you left your saddle where it was and just spun bigger or smaller circles on preference??
"Are you sure we're going fast enough?" - Emil Zatopek
Your foot would be 5mm nearer at 6 oçlock on each stroke but if you raise your saddle your foot will now be 10 mm further away than it used to be at 12 oçlock. Knee angle at 6 oclock is probably more important that at 12 oçlock but the latter may impact on your leverage at the start of each downstroke and should be borne in mind.
My understanding was you left your saddle where it was and just spun bigger or smaller circles on preference??
"Are you sure we're going fast enough?" - Emil Zatopek
Re: Short crank arms on a TT/Tri bike??? [luckyleese]
[ In reply to ]
Well then just imagine increasing crank arm length to, say, 300mm...
Saddle height is determined by knee angle at BDC. Your crank arm length is determined (to some extent) by your leg length and your preference for the feel of the pedaling circle (and whether you can transmit power in that circle).
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Some are born to move the world to live their fantasies...
https://triomultisport.com/
http://www.mjolnircycles.com/
Saddle height is determined by knee angle at BDC. Your crank arm length is determined (to some extent) by your leg length and your preference for the feel of the pedaling circle (and whether you can transmit power in that circle).
---------------------------------------------------------------------
Some are born to move the world to live their fantasies...
https://triomultisport.com/
http://www.mjolnircycles.com/
Re: Short crank arms on a TT/Tri bike??? [brider]
[ In reply to ]
*Adopts voice of Tom Demerly voice*
Which just goes to prove that there's no point just discussing this in theory - the only way to get it right is to be be professionally fitted.
I think (leaving aside issues of personal preference) the basic rule is a combination of what your leg length would indicate + whatever adjustment you need to make for your lower/leg to femur ratio. The hip angle of someone with a disproportionately long femur would be less affected by larger or smaller cranks whereas someone with short femurs who went on to bigger cranks would see their knee travelling up and down far more and their hip angle likewise changing a disproportinate and possibly undesirable amount in each stroke.
To answer your post like you say the bottom of the stroke is more important that the top but there's no point saying I like big cranks so I'll go to 300s and drop my saddle because you'll just end up kneeing yourself in the face and trying to start your downstroke with your foot too near your hip to make full use of your quads
"Are you sure we're going fast enough?" - Emil Zatopek
Which just goes to prove that there's no point just discussing this in theory - the only way to get it right is to be be professionally fitted.
I think (leaving aside issues of personal preference) the basic rule is a combination of what your leg length would indicate + whatever adjustment you need to make for your lower/leg to femur ratio. The hip angle of someone with a disproportionately long femur would be less affected by larger or smaller cranks whereas someone with short femurs who went on to bigger cranks would see their knee travelling up and down far more and their hip angle likewise changing a disproportinate and possibly undesirable amount in each stroke.
To answer your post like you say the bottom of the stroke is more important that the top but there's no point saying I like big cranks so I'll go to 300s and drop my saddle because you'll just end up kneeing yourself in the face and trying to start your downstroke with your foot too near your hip to make full use of your quads
"Are you sure we're going fast enough?" - Emil Zatopek
Re: Short crank arms on a TT/Tri bike??? [6cuda6]
[ In reply to ]
I would raise the saddle by 5mm if you want to keep the same knee angle at the bottom of the pedal stroke.
You might be able to go slightly lower in front by not having your leg comming up as high.
jaretj
You might be able to go slightly lower in front by not having your leg comming up as high.
jaretj
Re: Short crank arms on a TT/Tri bike??? [6cuda6]
[ In reply to ]
I have a 167.5 on my fixed gear, and a 172.5 on my road bike, and I don't alter anything but saddle height. I don't notice a difference, but both bikes are so different I bet I couldn't tell a difference anyway. Apples to Oranges.
Back in the 80's, Eddie B said you could add a tooth to your big ring for every 2.5mm you lengthened the crankarm. He claimed you could generate more power with the longer cranks, so does this mean you have to go 2 teeth smaller? Sacrifice gear inches for more pedal speed? It does work for some, and when I raced the track, it worked that way for me too.
BTW, a local shop built a custom frame for an ex-NBA player, and they special ordered 200mm crankarms. Boy do they look freakish!
"Maybe you should just run faster..." TM
Back in the 80's, Eddie B said you could add a tooth to your big ring for every 2.5mm you lengthened the crankarm. He claimed you could generate more power with the longer cranks, so does this mean you have to go 2 teeth smaller? Sacrifice gear inches for more pedal speed? It does work for some, and when I raced the track, it worked that way for me too.
BTW, a local shop built a custom frame for an ex-NBA player, and they special ordered 200mm crankarms. Boy do they look freakish!
"Maybe you should just run faster..." TM
Unless your legs fall off. Some people are sensitive to slight changes in crank length others aren't. A couple different prospectives. Your feet are actually moving faster at the same cadence with longer cranks, you usually lose cadence speed each time you get longer cranks, it is easier to get higher rpms with shorter cranks. I have bikes with 165mm to 180mm and don't have any problems going from one to another. I have problems with slight changes in Q factors.