I spoke too soon and thought too little. I ride frames in the 58cm - 61cm range. In these cases the slots tend to be fairly nearly perpendicular to the seat stays. Smaller frames do not exhibit this geometry (they are a few degrees off), nor do my largest frames (also a few degrees off). The two different extremes in frame sizes deviate from perpendicular in opposite directions.
My point remains...I don't think the location of the brake has a geometric logic.
Cheers,
Scott
Scott Minneman San Francisco, CA USA
-----Original Message----- From: classicrendezvous-bounces@bikelist.org [mailto:classicrendezvous-bounces@bikelist.org] On Behalf Of Scott L. Minneman Sent: Tuesday, January 18, 2011 10:18 PM To: hsachs@alumni.rice.edu; 'Classic Rendezvous' Subject: Re: [CR] Rear Brakes Attached Forward of the Bridge
If you look at the actually geometry of a built frame, I don't think you'll find this assertion to be true (just checked a 79 Colnago, a 73 Bertin, an 84 Mercian, a 59 Soens, and a 76 Stout before I got sufficiently convinced). Brazed up, a road frame's dropout axle slots are not horizontal at all, but rather they are almost exactly perpendicular to the seat stays (when viewed from the side of the bike, of course).
So, that means that mounting the brake behind the bridge puts the brake pads the same number of degrees off of perpendicular as mounting ahead of the bridge, it's simply two different directions.
I, too, have left well enough alone on this particular topic...all my bikes have the brake behind the bridge. None of my bikes have racks of any sort.
Cheers,
Scott
Scott Minneman San Francisco, CA USA
-----Original Message----- From: classicrendezvous-bounces@bikelist.org [mailto:classicrendezvous-bounces@bikelist.org] On Behalf Of Harvey Sachs Sent: Tuesday, January 18, 2011 6:34 PM To: Classic Rendezvous Subject: [CR] Rear Brakes Attached Forward of the Bridge
Consider a bike with horizontal drop-outs. In such a case, the brake mounted conventionally (rearward of the seat stays) is likely to tolerate more back-and-forth adjustment of the rear wheel w/o needing brake pad adjustment than one with the brake mounted forward. Of course, with vertical drop-outs, it doesn't matter.
The only time I was tempted to mount forward of the stays was, as I recall, late one night with a caliper too long for the conventional position. Otherwise, I've left well enough alone.
your mileage may vary.
harvey sachs
mcLean va