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building a wheel with offset/asymmetric rim?

9K views 32 replies 8 participants last post by  Lombard 
#1 ·
Can I use a carbon rim with an offset (2.6mm) on any rear hub (142x12)?
Or does a rear hub have to be compatible with offset rim? And does it matter if I choose J-bend spokes or straightpull spokes to use with an offset rim? which type of spoke is better in term of durability? planning to go with a hub with 28h.

Or should I not bother with asymmetric rim and just stick with traditional non-asymmetric rim?

This rear wheel will be for a hardtail mtb. My current wheel only has 24h and it keeps going out of true so I would like to build a new tougher wheel with 28h.
 
#8 ·
There's no requirement to "match" a hub to an asymmetric rear rim. As long as there's a cassette on the rear hub, the drive side flange will always be offset, and an asymmetric rim will have a positive effect on the resultant wheel build. Use any asymmetric rim you like.
^^^ This. The hub can't tell anything about the rim beyond spoke pattern (if it is one of those G3 or whatever). Using an asymmetric rim improves wheel durability and does indeed make for an easier time for the rim because there is less relative tension on the DS spokes, so the rim is less likely to be damaged by high spoke tension.
 
#7 ·
Since this is a disc wheel, I wouldn't even bother with an asymmetric rim. There won't be that much tension disparity. I also would go with a 32H for a rear wheel - especially for a mountain bike. Believe me, you won't notice the difference in weight of 4 extra spokes.

I'd use J-bend spokes because it's easier to find replacements.


^^^This.^^^


 
#25 ·
I can't say I have ever heard of any wheel failing or breaking spokes because of disk brakes. I'm sure it puts some force in there somewhere, but I have yet to read or hear some one say "I grabed the brakes and spokes died on my disk brake bike." Rider weight and ride conditions should dictate spoke count.

I have to wonder what forces a a spokes sees when using disk. I know I see my fork tucking under and rotors turn purple, felt some torque steer from the fork twisting, even seen some seat stays bend but all the pressure is centered in the axle and mount area. I guess on a full lock up there are friction torque coming back through spoke from the ground up. Other than that, the spoke is just weight bearing.
 
#26 ·
Not saying that disc brakes are a threat to spoke loading and wheel integrity because I have no data, but clearly there is a lot more spoke loading with a disc brake wheel due to braking. With rim brakes, the force of braking is dissipated through the rim/tire combination directly from the ground to the brake pads. With a disc brake wheel, all of the braking force has to be transferred from the hub (where the disc brake is attached) through the spokes to the rim/tire where contacts the ground. Spokes in a rim brake wheel never see that kind of force.

Again, whether this is meaningful I do not know.
 
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