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Update

I have successfully mounted a Zipp Firecrest 303 wheel set onto my Cannondale R800 CAAD 4 frame with Shimano BR-R8000 rim brakes. Thanks for the advice!


I would like to buy a carbon wheel set for my Cannondal CAAD4 R800. I'm using Ultegra R8000 rim brakes.

According to specs, the brakes can accommodate a rim with max. 28 mm width. Am I right to assume that 28 mm refers to the outer width of the rim?

I would like to buy Zipp 303 Firecrest wheels. The specs do not tell, which outer width this rim has.

Will I be able to use the Zipp 303 Firecrest wheels with Shimano Ultegra R8000 rim brakes?

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  • Are you interested by the tubular or the tubeless version of the Zipp 303 Firecrest wheels? The link to the specs points to the tubular version but I just wanted to make sure.
    – olliebulle
    Commented Mar 12, 2023 at 21:45
  • Tubular @olliebulle.
    – sebastian
    Commented Mar 13, 2023 at 6:33

2 Answers 2

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For a wheel to be compatible, it needs to respect three criteria:

  • Rim width (maximum width allowed is affected by brake shoes)
  • Tire thickness
  • Tire outer diameter

For the BR-R8000 with carbon wheels, Shimano (see dealer's manual on page 18) recommends:

  • Rim width from 20.8 mm to 24 mm with the R55C4 for carbon rim brake shoes or from 24 mm to 28 mm with the R55C4-A for carbon rim brake shoes
  • A tire thickness of 28 mm or less
  • A tire outer diameter of 684 mm or less

The Zipp 303 Firecrest wheels have an external rim width of 27 mm (see specs on page 17) and should therefore be compatible if the tire (or tubular in your case) respects the above requirements and the correct model of brake shoes is used.

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  • 2
    One caution is that carbon rim manufacturers will often specify a certain model of pad that their rims (specifically the resin) works well with. That dealer's manual is referring to the fact that those pads should be used with certain Shimano rims. Zipp would probably supply their own pads and/or tell you which pads work. I can verify that a standard pad with a rim that's 25mm external width (Hed Jets) works fine with R8000, and not many rims for rim brakes are >25mm ext. width.\
    – Weiwen Ng
    Commented Mar 13, 2023 at 0:21
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This is an elaboration of a comment I made on olliebulle's answer. Shimano's carbon pads may not work optimally with other rims. That does not mean they won't work on other rims. Rather, rim manufacturers will specify the pads they think work best with their own rim (and I think it's mainly about the resin they use in the brake track). For example, Zipp has its own dry conditions cork pad, its own general purpose pad, and it also allows Swisstop and Bontrager pads. I have no direct experience with carbon rim brake rims myself, but this blog post by November Wheels asserts that "there is also a broad range of what works".

I have a set of Hed Jets (25mm width at the brake track) that works fine with R8000 rim brakes and normal width pads. This width may not work well with older rim brakes, as they weren't designed with this width in mind, and might not provide enough leverage - keep in mind that 15-20 years ago, 25mm external width might have been seen as an MTB size.

I italicized brake track in the paragraph above. For clinchers, if it's not stated but the internal width is, you can guesstimate by adding 4-5mm to the internal width. For example, my Jets are 21mm internal and 25mm external; I have a pair of Boyd Altamont rims that I think are 19mm internal and 24mm external. I note that you have tubulars, so this might be a bit different but it should still be in the ballpark.

There are very few rim brake wheels whose external width is at or wider than the R8000 calipers' specified maximum width. I recall that Light Bicycle, a China-based direct to consumer brand, had one rim that's 30mm external width - and I'm not sure who even would but that, and they don't list it now, so I assume it was essentially nobody.

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  • Thanks for your insights Weiwen, most helpful and interesting!
    – sebastian
    Commented Mar 14, 2023 at 19:26

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