Im expecting to get quite a few varying opinions here so here goes. My old FSA compact chainset is looking a bit tired and the BB is on Its way out. The BB;s were never very cheap for the crankset so Im changing to go old shimano. Ive went from 172.5 FSA cranks to 175 105 cranks. I've read that people can develop knee pain and If so maybe alter your seat height position.
Whats yer views. ?
longer drop to the bottom of the stroke; you need to drop your saddle (assuming it was right before)
If you've put 2.5mm longer cranks on, then drop the saddle height by 2.5mm, otherwise your leg will be extending by another 2.5mm...
It really is THAT simple!
Ah cool , thats a simple and concise explanantion . Thanks 😀
It really is THAT simple!
Hmm.
I wouldn't bother.
Seat height is traditionally measured from the centre of the BB to the top of the seat. Dropping your seat because you've put longer cranks on makes the angle your knee has to bend at the top of the stroke even more acute.
Do you measure the depth of the sole on your shoes?
Do you measure the depth of your insole?
Do you measure the thickness of the socks you have on?
Do you measure the thickness of the pad, short, tights on your bum?
All the above measurements may well add up to the difference between your 175 cranks and your 172.5 cranks. There is also some evidence which I can't be bothered linking to, that crank length is of no consequence.
and I've read that most amateurs tend to set their saddle too high. If that's true, then adding "only" an extra 2.5mm extension might cause more pelvic rocking and increase the chances of damagecrank length is of no consequence.
I'm pretty sure crank length (within the "normal" range) makes minimal difference in power or efficiency