Uneven braking surface?

[Eman Resu]

In years gone by there were rims with anodised braking surfaces, such as the Mavic Mach 2CD2, Mavic Reflex, etc. After some time the braking markings would indicate that, under braking, the braking surface was not in one plane, more so in the rear wheel. I can't find a better link than the one below to demonstrate what I mean, but it will suffice

http://www.hilarystone.com/images/sale% ... k/SST1.jpg

It would seem to indicate that, under braking, at points where there is spoke tension the braking surface is pulled outward (or that at other points pulled inwards), despite the fact that the wheel was apparently laterally true in static mode (when built up).

So I've some questions (apologies if they've been asked before):
If this is true for rims of yesteryear, then is it true for the modern ones that have machined braking surfaces? If yes, then is it possible to build a spoked wheel in such a way that there is no distortion of the braking surface in use or is 'apparently laterally true' never completely laterally true?

Keep cycling and don't stress,
Dennis

[Brucey]

it has always seemed to me that some Mavic rims (BITD) would be slightly ripply before they were built up, and that this was why the anodising wore off unevenly. It would sometimes be noticeable but it rarely made braking performance terrible.

I always assumed that the ripplyness happened because the rim was slightly deformed as the double eyelets were fitted and the spokes were tensioned; the rims which usually manifested this sort of wear also had an extrusion profile that was curved on the inside, with which a flat-bottomed double eyelet/spoke tension cannot be used without there being some deformation of the rim.

Modern rims are machined (after the eyelets are fitted I think) and the eyelets are not seated in the same way, so I think that is the reason the same thing tends not to be seen.

cheers