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I recently decided to replace the rear wheel on my road bike since I couldn't disassemble the old Helicomatic freewheel

I now have a new rim, which oddly has slightly serrated sides (I'll add a picture tomorrow), while the original wheel was smooth. As a consequence, the rear brake doesn't create a lot of friction which I think is dangerous.

However, the seller insisted that the wheel was meant for rim brakes. Am I being lied to or what do I need to do to get proper brake grip on the rim?

  • Need pic (which I understand is coming), in the meantime can you add the brand/model of the wheel? – Argenti Apparatus May 11 '18 at 20:42
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    Do the 'serrations' run around the rim, such as seen here i.stack.imgur.com/XDo8R.jpg? – Argenti Apparatus May 11 '18 at 20:48
  • Likely just a machined sidewall, some are smoother than others. – Nate W May 11 '18 at 21:04
  • @NateW that's what I'm thinking – Argenti Apparatus May 11 '18 at 21:28
  • @ArgentiApparatus Exactly like that. – oarfish May 12 '18 at 9:04
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These are just machining marks from the tool that cut the braking surface. Rim manufacturers don't bother to get the braking surface completely smooth.

The tiny grooves don't negatively affect brake performance and will eventually wear away. You'll need to look for other causes of brake performance problems. Do you have new pads. New pads on a new rim make need 'breaking in', i.e. get a little wear before they achieve proper friction.

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    They intentionally leave the grooves in the rim, to serve as wear indicators. They have no significant effect on brake performance. – Daniel R Hicks May 12 '18 at 11:33
  • @DanielRHicks These very shallow marks are not for wear indication I think. Some rims have a deeper groove, maybe about 1mm deep and 2mm wide for wear indication. – Argenti Apparatus May 12 '18 at 11:51
  • I do have new brake pads, maybe that's it. I'll take some fine sand paper to them. – oarfish May 12 '18 at 14:34
  • @ArgentiApparatus - The wear indicators I've seen are only a half mm wide and about that deep. – Daniel R Hicks May 12 '18 at 17:53
  • @DanielRHicks I was guessing so you probably correct – Argenti Apparatus May 12 '18 at 18:11
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At different points in time it's been done to increase brake friction for rim materials that can otherwise be subpar in that regard. Steel and carbon fiber rims have both been made with deliberately rough brake tracks. The downside is how it degrades brake feel, in some cases to the point of causing a juttery feel. It's also harder on brake pads.

  • But it strongly feels as if the pads don't grip as well as they do in the front, is that an illusion? – oarfish May 12 '18 at 9:05
  • Have you toed-in the pads? If the pads stand parallel to the braking surface or even touch it first at the rear end, the braking force will be weak. Ideally they should touch the rim at their front end first and still be 1 - 1.5mm away at the rear end. If this is the case then cleaning both the pads and the braking surfaces with alcohol to remove any grease will also help. – Carel May 12 '18 at 17:24
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This is very common. I've had numerous intermediate level wheels from various manufacturers (Shimano, Fulcrum, Mavic) and they've all had slight groves in the braking surface

  • Yes, this began appearing 10-15 years ago, and the grooves are intended to be wear indicators. Probably added to avoid legal liability because people wear rims until the flanges pop off. – Daniel R Hicks May 13 '18 at 13:13

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