Theoretically, it should be perfectly straight. But the realities of the manufacturing world say that there will be some variation. Are your brake pads closer when they rub this wobble than they would be for your training wheels when doing any other ride? If so, then I'd say adjust them to how you normally ride them, and go from there. I think there's usually a 2mm total trueness tolerance for wheels like this. Not a performance problem in the area of aerodynamics.

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agrred, almost impossible to get a disk wheel abosultely perfect. THe thing that caught my eye about the post was that you were adjusting the brake pads in as close as possible to the wheel. I know that in a race situation, I open mine up a bit more than I would have them set up for training. In a race, there is a lot more adrenilin running through the body and that little tap of the brakes in a race is usually enough to put me over the bars if I don't allow a little slack on the brakes. Stand around T2 at a race and see how many people over brake.

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Mike Plumb, TriPower MultiSports
Professional Running, Cycling and Multisport Coaching, F.I.S.T. Certified
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Thanks!

The thing is that on my 404's, there is no rim rubbing even when the brakes are all the way pulled in close. I was just doing a comparison and noticed the rubbing. My guess is that it is about 1 mm (maybe less)or so off. I called ZIPP on it and they said that it is OK.

They explained that trueness parameters are extremely strict, for both disc and wheels but, due to the manufacturing process of a disc, it is very hard to get a "perfecly" true disc.

Thanks again for the comments!

One thing I really like is the Hub on this disc. It is like a fine work of art.

All 5 of the pairs of Zipp 909s received by my Team had the same margin of error (slightly out of true/out of round at the brake surface).

I contacted Zipp (who I've always found responsive). They indicated that they measure tolerances at the center of the rim (not the braking surface) and that the inconsistencies should not be noticeable when riding. They have no aerodynamic impact. Zipp also guarantees the quality of their rims so if you have problems...Simply return them for another pair. I've found them to be reputable.

My 404s were clinchers and had no issues so I think this is a Disc specific issue.

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