Knee pain from painful saddle?

[TronnyJenkins]

Originally Posted by rustychisel

can't tell, not enough information, plus it's the internet, but it seems unlikely.

More likely the fit on the bike is not identical to the other.... ITB? measure setback and check seat tube angle, and consider even pedals used and q-factor.

Oh, BTW, measuring seat height is effin useless unless it's from centre of pedal spindle, parallel to seat tube, to 'flat' top of saddle. [measuring from centre of BB is a fool's errand]

I measured a couple of my bikes tonight (main ride that I had a Retul fit on vs the one that I rode Thursday that gave me knee pain) and using this method the latter was 1cm lower! Interesting, though I am still pondering the geometry of it. They are the same crank arm length and I am pretty picky when measuring from center BB to saddle top. Maths!!

[rustychisel]

Originally Posted by TronnyJenkins

Maths!!

Yeh! That and reality.

Differences may involve crank length, seat tube angle, height of BB, and saddle setback.

[dem]

Originally Posted by rustychisel

Oh, BTW, measuring seat height is effin useless unless it's from centre of pedal spindle, parallel to seat tube, to 'flat' top of saddle. [measuring from centre of BB is a fool's errand]

I just noticed this comment and I don't understand it, can you clarify? Cranks/pedals rotate around the BB axis. The saddle height/setback is a fixed point, so it makes sense to me to offset it from the center of the BB assuming crank lengths are the same?

Seat tube angles tend to vary, so if you're aligning the cranks parallel to the seat tube from bike to bike, that'll be off in some amount?

My method:
1) Quick and dirty tape measure to get height/setback (usually within 1 cm) and apply to target bike
2) Use a self-leveling laser to level the bike axles front to back (IMHO, most critical step for consistency)
3) Use laser to make cranks plumb up and down so I can use the gap in the crank clamp to measure setback off.
4) Use laser to light up the nose of my saddle and the chainstay, measure from center of cranks with a caliper to get setback.
5) Saddle height I measure from center of BB to the flat-middle of my saddle.

This will get me within a mm or so between bikes.

[TronnyJenkins]

Originally Posted by dem

I just noticed this comment and I don't understand it, can you clarify? Cranks/pedals rotate around the BB axis. The saddle height/setback is a fixed point, so it makes sense to me to offset it from the center of the BB assuming crank lengths are the same?

Seat tube angles tend to vary, so if you're aligning the cranks parallel to the seat tube from bike to bike, that'll be off in some amount?

My method:
1) Quick and dirty tape measure to get height/setback (usually within 1 cm) and apply to target bike
2) Use a self-leveling laser to level the bike axles front to back (IMHO, most critical step for consistency)
3) Use laser to make cranks plumb up and down so I can use the gap in the crank clamp to measure setback off.
4) Use laser to light up the nose of my saddle and the chainstay, measure from center of cranks with a caliper to get setback.
5) Saddle height I measure from center of BB to the flat-middle of my saddle.

This will get me within a mm or so between bikes.

That's more or less what I have done previously, just on a less OCD setting. I've not had any issues until this. Now I want to go measure my other bikes and see if there are any discrepancies.