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Recreational Cyclocross and Gravelbiking This has to be the most physically intense sport ever invented. It's high speed bicycle racing on a short off road course or riding the off pavement rides on gravel like :The Dirty Kanza". We also have a dedicated Racing forum for the Cyclocross Hard Core Racers.

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Old 06-08-07, 06:34 AM   #1
Metaluna
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Good rim for 700C wheel w/disc brake

I'm thinking of going with a front disc brake on my Cross Check. I've already ordered a carbon disc fork from Nashbar, which is supposedly made by Winwood. I'll probably just use cantis on it for now while I'm evaluating the fork, but if I decide to go all the way I'll need to build a wheel. I'm thinking of starting with a Shimano XT M756 disc hub (which uses the 6-bolt mount instead of CenterLock, saving me from having to buy and adapter), but I'm not sure what rim to go with.

I was looking at the Velocity Aerohead OC because of the offset spoke bed to compensate for dish, but I'm concerned that this might be too light a rim, both to handle my weight (around 240) and also to handle the stress of disc braking. Also it only handles up to 28mm tires, though I've heard people have used 32's on them with success. I'd be using 32 spokes.

Does anyone have recommendations for a rim that is suitable for disc brakes, and ideally can handle a 32mm tire? I believe Velocity also makes the Synergy which is more of a box-section touring rim but is available with offset spoke holes.

EDIT: I forgot to mention that I currently have an unused 32h Mavic Open Sport rim which I could use, though I've heard some worrisome things about the quality of the MA3 which is the predecessor to the Open Sport.

Last edited by Metaluna; 06-08-07 at 06:56 AM.
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Old 06-08-07, 09:25 AM   #2
Adagio Corse
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I didn't realize that a front disc brake system requires the rim to be offset for dish compensation - same dish as a rear cassette dish or a specific dish for disc brake mounting?
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Old 06-08-07, 11:40 AM   #3
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I don't think it absolutely requires an offset rim, I just figured that, if it's good for a rear wheel with a freehub, the same reasoning should apply to a front wheel with disc mounts. It seems to me that the dynamics would be about the same only in reverse (i.e. the disc is pulling on the trailing "drive side" spokes in the opposite direction). I ran the numbers through Spocalc using the M756 hub and an Aerohead OC 32h rim, 3x lacing, and I got nearly equal spoke lengths for both sides, and a tension ratio of around 110% -- nearly perfect. With the Open Sport non-offset rim, the tension ratio was more like 150% with a 2mm difference in spoke lengths between the disc and non-disc sides of the hub. I think this means that the disc side of the wheel has to have 50% more spoke tension than the non-disc side, but I'm kind of new to spocalc, maybe I'm interpreting that number incorrectly.

I've heard that there are some disc-specific offset rims out there (Bontrager?), but this was just a generic Aerohead OC that most people probably use for rear wheels.
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Old 06-09-07, 03:53 PM   #4
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i'm using Sun CR18s. heavy, but durable. so probably of no help to you at all.
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Old 06-09-07, 04:39 PM   #5
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Salsa Delgado Cross rims are really nice.
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Old 06-09-07, 09:33 PM   #6
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My Jamis Coda Elite is not a cross bike, but it does have 700c disc wheels. They're Ritchey Aero Pro rims which I can't find anywhere. Probably an OEM only wheelset. Anyhoo, they are OC rims. You certainly won't go wrong building with them.
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Old 06-10-07, 03:23 PM   #7
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Quote:
Originally Posted by nitropowered
Salsa Delgado Cross rims are really nice.
I was at a local shop that carries a lot of less common bikes including crossers and 29ers, and they had a number of 700c disc wheelsets for sale based on this rim. I ended up buying a front wheel using a 32h Delgado Cross rim laced to a XT M756 hub, with DT 2.0/1.8 spokes, all black. I was a little apprehensive because I'd run across this rim online but I didn't know much about it. But, I like the shop and it seemed like serendipity to have the exact kind of wheel I need with the exact hub I planned to use right there in front of me, plus I've always liked Salsa's stuff. The only thing is I would have preferred silver to match my existing (rim brake) rear wheel but this sure is a pretty rim. I probably could have saved $80+ by building it myself but I like to reward shops that try to be a little different and carry a more interesting selection of stuff.

It was built by "Quality Wheelworks", which I think is just QBP's wheelbuilding operation. It was probably machine laced, but it seems to have been stress-relieved because when I got it home I tried stress-relieving it by twisting each crossing spoke pair against each other with a screwdriver handle (Sheldon Brown's trick), and the wheel was still perfectly round and true. I can't wait to get the rest of my disc hardware in so I can try it out.
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Old 06-10-07, 03:31 PM   #8
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Quote:
Originally Posted by jhota
i'm using Sun CR18s. heavy, but durable. so probably of no help to you at all.
Actually I was considering these for my (rim brake) wheelset when I first bought the bike. I ended up going with 36h Velocity Dyads which are also a good durable v-profile rim...same die extrusion as the Aeroheat MTB rim but in 700c diameter.

FYI, Nashbar has CR18's on sale at the moment for like 10.99. Unfortunately, they're the 26" version.
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