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I have bought a Masi fixie riser that comes with painted unmachined rims and rim brakes.This does not seem safe.Is it?

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    Are you sure they are painted and not anodized or ceramic? – mikes Feb 11 '15 at 23:50
  • Did the bike in question come with brakes? – Michael Lemberger Feb 13 '15 at 16:50
  • Related question: bicycles.stackexchange.com/questions/16757/… – Benzo Feb 16 '15 at 20:22
  • @Benzo - its an exact duplicate (even by the same asker) of the question I linked above). [But, for some reason, it was not closed as a duplicate] – Batman Feb 16 '15 at 20:30
  • Note that there's a difference between "painted" and "stained". Few rims are painted anymore -- if they have coloring that's generally a stain applied as a part of the anodizing process. It may wear off over time, and may not provide the ideal friction coefficient, but it won't peel like paint would. – Daniel R Hicks Feb 17 '15 at 2:00
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For your specific bike, the Masi Riser, there is nothing to worry about.

Those rims are from BrevM. From the review of some brevm wheels on urban velo, it says that the rims were machined before annodizing. So, the annodizing masks the brake surface, but it should work fine. Even if they were not machined ahead of time, assuming good quality control, there really shouldn't be an issue unless they were made for disc specific mountain bike or cyclocross applictions.

So long as your rims are not disc specific, but not machined, then you should be good, and it looks like that's not the case here. Many times fixed gear bikes are sold without a machined brake surface for the seamless look, especially for those who prefer to ride brakeless.

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The answer ranges between "not really at first" to "not at all."

If the rim has a braking surface that was simply painted over, then your braking power is going to suck, even to the point of being dangerous, until the paint wears off. I had a pair of Stan's ZTR 355's that were like this. One race in the mud and the paint was gone and braking power was fine.

On the other hand, many rims that are painted have a profile that was never meant for rim brakes to start with. It doesn't matter how much paint you rub off of these rims as you're using them in a manner that they were never meant to be used.

To illustrate, here's a couple of rim profiles with rules of thumb:

Possibly Ok (check with manufacturer)

enter image description here

NEVER OK

enter image description here

If the rim states that it's "disc specific" or "disc only", go with that, and don't use rim brakes on it.

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