How to Measure Fork AC - Syncros v.s. Factory Rigid
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somewhere, not sure on here, was a thread about Trek warranty, the forks had been changed, longer I think, and managed a crash where nose came up too high, anyway the consensus seemed to be that the handling had contributed and the warranty voided as considerably non standard, not sure where thread was but I think it makes sense to try to get it close to what designer intended, certainly in my case he knows more than I do on geometry and handling etc to want to keep fork length pretty as intended and only tweak stem and bar length
shutter":2czwtyes said:
A 50mm variation in fork length roughly equates to a 2.5 degree change in frame angles, so not insignificant.
As far as measuring fork lengths go, I've always just measured from axle to crown in a straight line (ie not the Sheldon Brown way) but with forks having a typical offset of 38mm it's not going to make much difference whichever way you measure - probably only 2-3mm which is neither here or there.
I'll work it out once I can find a calculator....
shutter":q7byrjw1 said:
You're getting a shorter length because a) with your method you're measuring the base of a triangle rather than the hypotenuse, b) you're measuring to the top of a skewer sitting in the dropouts rather than to the centre of the wheel spindle, this in itself accounts for a 4.5mm difference..
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Fork length is properly measured inline with the steerer, you then measure rake from there. BUT most just measure the centre of axle to crown race seat as the length is not to far off.
Power lights are classed as the 390/395 range so pure suspension setups.
Ignore sag on the sus forks, 30% is modern sag, you're only talking 10% max in the late 90's, let alone mid 90's
I cannot remember the original forks off hand in 1996 for the blizard but 420/425 would be your nearest fork.
It may well handle the 395 forks and you'll end up with race geometry of the early 90's. But I wouldn't bother.
Power lights are classed as the 390/395 range so pure suspension setups.
Ignore sag on the sus forks, 30% is modern sag, you're only talking 10% max in the late 90's, let alone mid 90's
I cannot remember the original forks off hand in 1996 for the blizard but 420/425 would be your nearest fork.
It may well handle the 395 forks and you'll end up with race geometry of the early 90's. But I wouldn't bother.
Andy R":3gbt9xga said:
Well... ok, I see my original error... If you look at where the skewer you can see that the edge of the skewer that I'm measuring is maybe 1.5mm lower than the actual center of where the axle would end up... so really I should have reported the measurement to be 380.5.....
Now, if you draw up a little triangle and bust out Pythagorean Theorem (excuse my spelling) you will see that the hypotenuse is reallllly only about 3mm longer...
380.5 plus three is only 383.5
soooo where's that other 6.5mm ??
BTW the fork legs are at their longest point in the crown... They can be made shorter but where they are set now they can Not be lengthened without sinking them into the crown below the surface... (which I assume is not meant to be done...)
