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How true is true?(4 posts)

How true is true?GMS
Sep 28, 2002 5:06 PM
I experienced brake squeaking today, so I looked into it and concluded that my rear wheel is slightly out of true, and my front is less than perfect. I'm not sure if this is the cause of the squeaking, but it's an issue nonetheless.

I verified the trueness of the wheels by holding my brakes in a steady position and noting that the pads hit harder in some places in the revolution than in others.

Is the above test always going to "fail" even on a reasonably true wheel (and only perfectionists notice) or is it plausible to have a wheel that has no perceivable inconsistencies?

Assuming my expectations are not too high, and my wheels do need truing, I imagine it would be better if I did it myself. I have no experience with truing wheels or adjusting spokes and I have no tools to do such. If I acquire the proper tools (cost?), is there a process I can follow that will give me a true wheel, or is it an "art" that I will inevitably fail at?

The wheels in question are Mavic CXP 21s (supposedly heavy and sturdy) with 32 spokes each, and there are about 1000 miles on them. How often do wheels go out of true? I did not hit anything out of the ordinary today.

Thank you for any information.
try this site...C-40
Sep 28, 2002 5:47 PM

Lots of good info on tools and maintenance at this site.

You might also want to read Jobst Brandt's book The Bicycle Wheel.
Sqeaks are not due to out of true wheelKerry
Sep 29, 2002 4:34 PM
They are generally tied to brake pads not being properly toed in (9 times out of 10). The next cause for brake squeal is high humidity tied to lack of toe in - the brakes are quiet except when it's really humid. Then comes contamination of the rims and/or pads - clean the rims with a Scotch Brite pad and scuff the pads with sand paper. Out of true wheels can cause uneven braking or shuddering.

Your method of checking for true is not clear - it's better to temporarily move the brake so that the pad is quite close to the rim, and then look at the gap between pad and rim. When you are applying force to the rim with the pads, things can be confused by any play in the hubs or movement in the brakes. Use the "air gap" approach - the amount of wobble should be less than +/- 0.5 mm (some like closer tolerances than that, but that is OK). To say that you have no experience and apparently no idea what a spoke wrench is does not suggest that "it would be better if (you) did it" yourself. You would be better off if you could get someone to give you a little hands on tutoring.
do it yourself !PeterRider
Sep 29, 2002 8:05 PM
people on the board will tell you to bring the wheel to a shop, but I say: get a spoke wrench, you can do the truing yourself. The book from Jobst Brandt is very good but I wouldn't recommend it just for truing. I would rather recommend a book I bought based on comments on this board, "zinn and the art of road bike maintenance" (by Lennard zinn), I just checked and it has easy to understand drawings.

Depending on how close to the rim you like your brake pads, you may want your wheel more or less perfectly true. If your brake pads are quite far from the rim, 2mm wobble doesn't really matter. If they are very close, you want a wheel with better truth.