Stans Grail Cb7 rim brake build.

Everything about building wheels, glueing tubs, etc.
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downhill1234
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by downhill1234

After a bunch on research I'm considering building a lightweight set of Grail CB7 wheels. The catch is- rim brake. I have a pair and there is ample room for a brake pad, the real question is if anyone has done this?

I called Stan's and asked if the holes are drilled in the rims or in-moulded and they said the holes are molded in the rims. I've never know this to be a thing but I guess it is?

Mind you, this isn't going to be a normal ride wheelset, just a climbing set and going back down slowly sort of thing. With Extralite hubs the set would build sub 1kg.

If some of the lightest tubular sets on available are in the 700-800g range the 300g weight penalty is worth it for how much faster the fastest clincher tires roll over the fastest tubulars, heck, even 450g or so makes it faster.

Cheers!

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FIJIGabe
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by FIJIGabe

I just want to confirm: you’re talking about running rim brakes on a disc-specific rim, right? If that’s the case, it’s a recipe for disaster, but hey, it’s your face!


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by Weenie


downhill1234
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by downhill1234

Yep, thanks for the useful information!

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FIJIGabe
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by FIJIGabe

Well, to be more specific, those rims aren’t designed to handle the heat generated by brake pads. Even a modest amount of braking (especially downhill) will generate heat - and likely more than enough to reach the maximum CTg required to start degrading the resin. Brake tracks are necessary to dissipate or manage the heat, appropriately.


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downhill1234
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by downhill1234

Thanks for that, wasn't really sure what makes a carbon rim ready to be braked on. This makes sense. 8)

petromyzon
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by petromyzon

Quite short sidewalls as well, and very little of that is parallel enough to give good braking bite.
5 or so years ago manufacturers were putting out aluminium disc brake rims that were simply the rim brake versions without the sidewall machining. I would, at a push, have been happy to use some of those for rim brake use. No longer.

mattr
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by mattr

downhill1234 wrote:
Sun Apr 07, 2019 4:49 am
Thanks for that, wasn't really sure what makes a carbon rim ready to be braked on. This makes sense. 8)
The other thing to bear in mind is that it'll not be designed for those loads, as in the actual geometry/thickness of the rim there. It could also just be a fairly light weight finishing layer. And as mentioned, Stans have very low sidewalls, and won't be using a high temp resin either. Even the early stans rims with brake tracks could be a bit of a bugger to line pads up on!

Have you looked at farsports and light bicycle (and others), AFAIK they offer light, wide, rim brake carbon rims. You should be able to find something in the 350 gram range that is rated/designed for disc brake use.

mattr
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by mattr

downhill1234 wrote:
Sun Apr 07, 2019 4:15 am
I called Stan's and asked if the holes are drilled in the rims or in-moulded and they said the holes are molded in the rims. I've never know this to be a thing but I guess it is?
It's been a thing on and off since the early days of CF rims. Molded in costs more but leaves the CF stronger, so you can thin the spoke bed slightly (lighter rims). Drilling costs a lot less, but you weaken the cf and have to use a slightly thicker/heavier rim bed. In practice it makes virtually no difference.

downhill1234
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by downhill1234

[/quote]
Have you looked at farsports and light bicycle (and others), AFAIK they offer light, wide, rim brake carbon rims. You should be able to find something in the 350 gram range that is rated/designed for disc brake use.
[/quote]

Thanks, Farsports makes a very light rim bt not sure of tubeless compatibility, looks like it's not but I sent a message.

moyboy
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by moyboy

did you call fairwheelbikes? they should be able to advise you what will work with weight in mind and riding style.

by Weenie


downhill1234
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by downhill1234

Kyle at farsports got back to me, 360g rim that is tubeless ready! Weighing hub options now. Extralite is tempting, going to talk with Fairwheel soon.

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