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I'm looking at getting a wheelset with disc hubs and rim brakes to run on my disc and non-disc cross bikes. There are stock wheels that have velocity a23 rims, which are a poupular rim brake compatible rim. However, the stock wheelset tend not to have machined brake surfaces.

Is not having a machined brake surface a problem? Does it matter whether the rim is painted or anodized?

Update:

It seems like some old heads seem to think that a machined sidewall was a marketing gimick made to stop brake squeal on new showroom bikes. Rivendell sell a lot of rim brake wheels without a machined surface.

Jobst Brandt via Sheldon Brown: http://sheldonbrown.com/brandt/machined-rims.html

Rivendell (probably via Grant Peterson) http://www.rivbike.com/kb_results.asp?ID=52

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    I'm not sure that machining tire sidewalls is a good idea.:-)
    – amcnabb
    Jul 21, 2013 at 16:28
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    The reason for machining the sides of the rim is to provide a smooth brake surface. If you have disk brakes there's no need to even have the surface -- disk-specific rims slope inward vs having the parallel sides. All aluminum parts should be anodized, to protect against corrosion, but this is almost certainly done if the parts are painted, as the anodizing "preps" the surface to hold paint better.
    – Daniel R Hicks
    Jul 21, 2013 at 21:49
  • The idea is a set of universal wheels for disc-equipped and rim brake bikes, no? Would it be an even split between disc usage and rim usage? Or would you be using them primarily on one bike with the option of swapping over?
    – WTHarper
    Jul 21, 2013 at 22:31
  • Really, I'll probably use it more on the disc bike initally, but I tend to try and repurpose parts as much as possible. In this case I'd like to keep the answers general. This is also of importance to fixed gear riders who may want to add a brake to their wheels, which may not be machined.
    – Benzo
    Jul 21, 2013 at 22:41
  • Fwiw, I played bike polo for about a year on a set of velocity chukker rims that were not machined. The bike stopped well with standard cheap road calipers(shimano sora) and I've finally worn through most of the annodizing on the front wheel after that time.
    – Benzo
    Nov 23, 2014 at 14:15

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Rim walls are machined, if not for aesthetical or marketing reasons, to give the braking surface of rims most regular shape possible, removing small irregularities which could cause "hard spots" while braking, specially around the seam (spot where both ends of the rim are connected together during manufacturing).

Also, it seems to me that the residual grooved pattern improves braking power, most probably due to increased contact surface and possibly dirt clearance issues, without noticeable increase in pad wear, but I have no objective data to support this impression except a positive personal experience with a handful of machined-wall rims with v-brakes.

Hope this helps.

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