Mike,
I hear what you're saying, but could expand references to your main triangle alignment, and especially the part about splitting the center measures difference and comparing to dish? I've heard front forks should be done by a shop with the correct Parks Tool since its just 'aligned' by bending 2 dangling fork legs; and what you say makes sense, but have never heard of an independent means of aligning the main tubes or exact references to measures comparing to wheel dish tolerance, seperate from 753 issue (it could be an 'industry' secret - ?). You are aligning wheels and not the body in between, so I'm confused as to your points of reference unless you are talking about bio mechanical interface alignments which could be very important, as in a bent crank (maybe the most important of all imo).
The rear alignment is usually highlighted from my inexperienced viewpoint to
adapt to newer wider cassettes, smaller width fixed gears, or in my case (in
the future) slightly wider hyperglide IRD freewheel. And the rear wheel
alignment process takes into account the average of the main frame through
(string) measurement means.
>From Car alignment experience, the string method is like 'eye balling' the
toe and camber angles. Caster would
be verified by trial and error on tendency to 'pull' to one direction.
Alignments use 3 angles for the vehicle to 'track' correctly, and some are
included in the string method (which does sound basic, but a measure no
less). The front should be more important for alignment since the rear wheel
'tracks' or follows, but the rear axle is where more variables are
introduced including bending rear forks out or in with 2" x 4" 's.
You bring up new and interesting view points, and would especially like to understand the part about spliting rear alignment measures to verify if dish is within tolerance. Bending a frame is pretty stressful, lol.
Thanks Greatly, Phil Bailey Sarasota, FL
********************************************************************************************************* Mike said: *********************************************************************************************************
Perhaps more importantly, is the main triangle in alignment? Many folks worry about the rear triangle when in fact the main may (or may not be out). If you were to align the main triangle (eek, 753!) then the rear alignment would then change once again! Folks like to worry about the rear because that is often what is under their control with string and relatively easy bending, but I don't worry about the rear until the front is in order.
Reality is that if the main is pretty good, and the rear is off by a few mm, then no worries. And are you splitting differences to know where true center is anyway? If going off the seatube with string, you must split in half the relative difference between two meassurements to get the amount your off center. So if one dropout is 3mm farther out relative to the seatube than the other, your really off 1.5mm. If dish and tires are within that amount your doing well.
Mike Kone in Boulder CO