|   Lacing Pattern for Disc Wheels? | TMike
Nov 1, 2001 11:25 PM | | Hi all,
I just bought a front Avid mechanical. Works great, but the clearance to the spokes is tiny. I bought a wheel from some place not known for their wheels - but I pre-stressed the spokes (bent them as recommended on Sheldon Brown's site) and that helped - only to the degree that I could actually mount the caliper and have it rub only sporadically. My question is: is there an alternativce lacing pattern for disc wheels, and if so, what is it? I mean, can all of the spoke heads be pointing toward the disc or something like that? Thanks,
Mike |
| Checked your dish? Does it rub just under braking? | Bianchi4Me
Nov 2, 2001 6:20 AM | | If you are getting intermittent rub just spinning the wheel with your hand, then I'd check the dish of the wheel first and make sure that the rim is actually centered in the frame. Is this thing nice and true? If it is, I'd kind of expect ALL or NONE of the "outside" spokes to rub. If you got a few touching and a few not touching, it might be slightly out of wack, or it might just coincidentally be exactly the right distance away where a tiny variation in spoke placement is to blame.
There is a slight difference in how you lace disc wheels, basically using a "mirror image" of a standard 3X pattern. Idea is to place the spokes which are pulled under braking to the OUTSIDE of the crossed junctions. The pull from the brake straightens those spokes, which causes them to push against and displace the neighboring spoke at the cross. If you use a "normal" lacing, this "push" under braking would be from the inside moving out, which makes the spokes spread out and can cause clearance problems. By swapping the position of the spokes, you make the push come from the outside and push the other spoke inward.
All that would only matter if your wheel was only experiencing this clearance problem while actually under braking forces. If it does it sitting on the repair stand just spinning the wheel, we need to look for another solution.
If your dish is perfectly centered now, a low-tech lazy solution would be to deliberately mess it up by adjusting the rim over just enough to get rid of the rub. Perhaps not the "ideal" solution, but if you are talking about 1/2 a millimeter it won't hurt anything. Most factory built wheels I've measured are off by that much to start with. |
| Checked your dish? Does it rub just under braking? | TMike
Nov 2, 2001 8:19 AM | | The first thing I did when I received the wheels was to check the dish. It was fine, but I've ended up redishing it to try to get rid of the rub (it was happening all the time). That didn't really help all that much because redishing the wheel won't move the spokes much near the hub (think trig). So, I've moved the pads so that they are in about the most un-ideal location, and there's no rub. I'll check the lacing, but the fact that it mainly happens when the thing is sitting there unstressed makes me think it's something else. Thanks for the input.
Mike |
| One other thing to try... | Bianchi4Me
Nov 2, 2001 12:41 PM | | Are the spokes sitting nice and flush with the hub flange? They naturally tend to arc upward from the flange hole. You're supposed to squish them down when you build the wheel so that they sit flush against the flange. If there is any gap between the flange and the spoke ends, you can try bending them down. Even if you can't see a gap, if the spokes weren't properly seated they may flex outward when the wheel is loaded. You can try to squish the spokes down with your thumb and see if you can seat them a little better. Hard to do with the wheel under tension though, they'll probably just flex down without actually bending. You might have to release the tension in order to accurately check for this and correct it if needed. |
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