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What is protocal for measuring seat angle for forward seats?(5 posts)

What is protocal for measuring seat angle for forward seats?curtybirdychopper
Apr 15, 2003 11:58 AM
Couldn't find exactly what I was looking for after a search, so here is Curtis' question of the day:

What part of the seat is typically referenced to calculate the effective seat tube angle. If I move my seat forward or turn my seat post around to steepen the angle, what exact reference point should I use?

Should it be the point on the seat that is obtained from extending the seat tube line up to the saddle when the saddle is in a neutral position on the seat rails? This makes most sense to me.

Any other ideas?
thanks, happy tuesday. curtis
re: What is protocal for measuring seat angle for forward seats?Jon Billheimer
Apr 15, 2003 12:10 PM
Your idea of extending the seat tube line makes intuitive sense. Does that line then intersect the part of the saddle that supports your sit bones?

Dan Empfield at Slowtwitch.com published a great bike fit article which gives a chart to determine effective seat tube angle based on the saddle setback from the bottom bracket, relative to seat height measured from the bottom bracket. I originally accessed this article at the Cervelo website. I don't know whether it's still there, but here's the original url: www.cervelo.com/qa/fit-article1.html If it's still there it'll give you an easy method to determine effective seat tube angle.
that works for 'average' seat lengths, hmm may be good enough.curtybirdychopper
Apr 15, 2003 12:45 PM
I don't like how the method works for average seats, average seat posts, etc. but I'll try both methods and see how they compare.

Does anyone out there remember the equation that relates the length along the perimeter of a circle given the diameter and angle, a chord length type equation?

thx, c
that works for 'average' seat lengths, hmm may be good enough.Jon Billheimer
Apr 15, 2003 1:12 PM
FWIW, average saddle length is about 270 mm. So if yours is significantly different simply add or subtract the difference to or from your setback measurement.
my wife tells me mine is about 270mm, so i'll go with that.curtybirdychopper
Apr 15, 2003 1:19 PM
I should probably go with dan's method because it is sort of a standard, at least his, based on more experience than i have.

thanks jon.