Had a physio session last night and it came up about saddle heights and crank lengths been commuting for the last 3 months on a road bike bouht off here as a complete bike (did not even look at the crank lengths) and have been having a dead left leg(upper thigh,foot and lower calf) feeling when putting the power down the sypmtoms seem to suggest nerve damage in the lower back!

Will the 170 roadie cranks cause me problems

Shorter cranks are better for higher cadences. Assuming you’ve got a higher cadence on the road bike then on the mtb, they should be fine. I’ve got different length cranks on all my bikes, I never notice much difference.

Will the 170 roadie cranks cause me problems

shorter than ‘ideal’ cranks don’t normally cause issue. longer ones could.

how tall are you?

5ft 10 !

then 170, 172.5 and 175s should all be fine.

i’m 5’11” and run 170s & 175s.

saddle height could still be wrong though – and it will be different for different crank lengths.

Ok will stop shopping for a new set of cranks!! even though I need a triple.

170…