squirtdad

Ok...I've got the lateral, the dishing and the tension looking good. (rear wheel, ultegra 6500 hub, velocity aerohead rim, double butted stainless spokes)

What is acceptaible margin for vertical true?

I am with in 1 mm of true on the vertical....except for one section that is....Low. Al the instruction I have seen suggest taking down the high spots...that tensioning is bet for vertical truing. any ideas for best approach with a low spot....the visual of the low is exaggurated by being at the same part of the rim with the lable.

thanks..

kenhill3

That's the telling part of your post. The label on rims is most often placed where the rim is pinned or welded together in the manufacturing process. THAT area is where you will often have less than perfect round. Try unwinding the spokes in that area to see if it makes any significant difference, if it does then you would probably have to up-tension the rest of the spokes............oh, I'm having a deja vu here. Been there, done that.............when I've encountered this in the past I just stopped right there because I realized that it was probably in the rim itself and I wasn't gonna make things any better by radically changing the tension in one area. Just let the 1mm go- bet you never feel it while riding.

well biked

I agree with what you're saying, but I think he means he's got it to within 1mm of radial true everywhere EXCEPT the rim seam.

I don't know how bad this one is, but I've been frustrated by this myself with some rims.

Retro Grouch 

Yeah. I've visited a factory that made bicycle rims. They took long extrusions, rolled them into a coil and cut the coil to make several hoops. The saw kerf where they cut the coil leaves that area a tiny bit short of enough material to make a whole round rim.

If you examine rims very carefully where they are joined I've got some (Mavic) that look like a filler piece has been inserted into the joint. I've got some (Velocity) that look like each rim must must have been cut individually allowing enough extra material to account for the saw kerf. And I've seen many that just result in a slightly low spot at the rim joint.

cny-bikeman

1 mm out of round is too much, in my opinion. that's the most you should have in the very worst spot. Getting the wheel in round is harder, but can be done as long as the rim is built to good tolerances. Work on at least 4 spokes at a time, and keep in mind that you can't move the rim much in or out without adjusting elsewhere.

If bringing in a high spot you may need to loosen the spokes directly across the wheel or possibly all of the spokes outside of that area before tensioning the high spot, and the reverse for a low spot. A tension meter would be almost required if you have to do that much adjustment, otherwise you will find it very difficult to keep track of tension.

DinoShepherd

Normally for a low spot, you loosen the four spokes in the area 1/4 turn and then tighten the spokes 180 degrees a like amount.

If your spoke tension is good, I would probably leave it.

-Z

Al1943

When building a wheel I find it better to concentrate on radial true and dish during the earlier stages. Lateral true is the easiest part of the build.

cny-bikeman

I would disagree that there is any "normal" for working on round - too many variables, and 1/4 turn at a time is almost always too little at at time.

cascade168

Very good comments. It's much easier to get the radial true done early in the build.

operator

I'd rather have lateral off than radial off.

cascade168

Well, there is a "normal". It's clearly defined in Barnett's as 0.5mm maximum variance as the minimum acceptable. This obviously assumes a perfectly round rim. Almost all wheels have little imperfections (especially at the seam), and those should be disregarded when measuring how "out of true" your rim is.
Working around the imperfections, such as at the seam, is what separates the men from the boys. Great wheelbuilders know how to minimize those imperfections and when to call it a day. You can only do so much. Any time you're looking for an industry standard it's a pretty safe bet that it's spelled out in Barnett's. While they don't actually come out and state "these are the standards", it's accepted that they are, in the business. Getting 0.5mm is not that difficult.

Plus, with a wheel like a Ksyrium (i.e. profiled alloy spokes), 1/4 turn at the end of a build is WAY too much of an adjustment. The problem you face in the end game, with a wheel like that, is how to make adjustments that are small enough. Also, the lower the wheel's spoke count, the smaller adjusts can still make big changes in the wheel. A lot of time just making that spoke squeak tells you that you moved it.

Al1943

+1
A 1/4 turn is a huge change. When it gets down to a fraction of a mm any movement between the nipple and the spoke is significant. With butted or skinny spokes I hold each spoke firmly with pliers while turning a nipple. This gives me better control and eliminates spoke windup.

Al

operator

+1

Even 1/8 turn is too much.

cny-bikeman

Please check the context, which was the "normal" amount to loosen or tighten, for which Barnetts has no standards.

Again, context is key... The original problem was out of round of a full mm. This is obviously not "end game" at all and 1/4 turn would accomplish very little. The OP most likely needs to back way up and start over, focusing as suggested before on round more than true.

I will concede that a lower spoke count calls for adjustment of fewer spokes, but I stand by the rest of my comments. I built wheels before the days of common 24 spoke and ultralight rims, but after building about 500 wheels and supervising the build of many more as a trainer and shop supervisor I am well aware of both practice and standards.