Bill: Revealing my ignorance: this had never occurred to me before. Obvious, once someone points it out, but...well, anyway, another point of inspection. Thanks for pointing it out.
Tom (whose cluelessness knows practically no bounds) Allingham From: rbw-owners-bunch@googlegroups.com [mailto:rbw-owners-bunch@googlegroups.com] On Behalf Of Bill Lindsay Sent: Tuesday, November 05, 2013 9:47 AM To: rbw-owners-bunch@googlegroups.com Subject: [RBW] Re: Velocity Rims, Again Corwin Yes, the geometry of the brake determines the path the brake pad takes to the rim. Cantilever pads dive as they go inward. The sidewalls of the A23, tilt slightly in the wrong direction for cantilevers. The brakepads strike kind of a glancing blow. It's not a major problem, but it does need to be part of your regular inspection of your bike to make sure you readjust the pads as they wear. In many cases I've seen brakepads dive so the edge of the brakepad sneaks under the rim, and as the pad wears futher, that edge becomes a ledge, and can actually catch under the rim. In very severe cases of neglect you could dive under the rim into the spokes. Some classic touring bikes used to come with rims that tilted in an upside down V shape, optimal for diving cantilever pads. Caliper and centerpull brakes, with the pivot point above the rim, cause the brake pads to rise as they move inwards (on the arc of a circle). The A23 is tilted more or less perpendicular to that rising path. As the pad wears, it'll still strike the brake track in approximately the same spot. Boulder celebrates their offering of the A23 and A23 O/C as their perfect rim. I think it's really close, but if I could make any adjustments, tweaks to the brake track would be my suggestions. Bill On Tuesday, November 5, 2013 12:22:04 AM UTC-8, Corwin wrote: Hi Bill - I have spec'ed a set of wheels with A23 rims. I will be stopping these wheels with a pair of calipers - known to some of us as sidepulls. But I am intrigued by your comment about the slight V shape of the rim being ideal for centerpulls and caliper brakes and sub-optimal for cantilever brakes. I assume this has something to do with the pivot point of the brake being used with the rim. Is that accurate? Thanks, Corwin On Sunday, November 3, 2013 10:53:57 AM UTC-8, Bill Lindsay wrote: the a23 extrusion has been out there for a long time in 700. anthony at longleaf bicycles in new england was the first to pony up the money for a run of 650b a23 rims. they work great, and like all tubeless ready rims, tires fit great on them. the 'new' part with boulder is they are now offering the a23 off-center in 650b, in addition to the regular extrusion for fronts. they also had them polished. its a very good rim. i ran the symmetric ones from longleaf the possible negatives of the a23 extrusion in my mind are: 1. the brake track is not very tall, not as tall as the p23 or 2. the brake track sidewalls are not parallel. they have a slight v shape, ideal for centerpulls and caliper brakes, sub optimal for cantilevers, 3. a modernish look, not as classic as a boxier section -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. 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