mancello@acf4.UUCP (Homeboy#1) (09/24/85)
I have recently started truing my own wheels, but I need some advice on making sure that the rim is centered between the axle locknuts and using the correct amount of dish for the rear wheel. I have an inexpensive dishing tool, but it is not readily apparent how to use it correctly. I have read many bicycle repair books and one book on building bicycle wheels, but I find that dishing/centering is never covered adequately. How do I use the dishing tool (I have the Minoura model) to ensure correct amount of dish? I know what some builders do is reverse the wheel in the truing jig or on the bike to see the relative offset, but utilizing a dishing tool should yield more precise results. Any help would be appreciated. -Dominic Mancello (cmcl2!acf4!mancello)
reintom@rocky2.UUCP (Tom Reingold) (09/26/85)
To test if your rim is centered between the locknuts of your axle, just place your dishing tool against one locknut and the side of the rim. Tighten the set screw on the tool and then put the tool on the other side of the wheel. If the tool presses against the rim and there is space between the tool and the locknut, then you know that the wheel is built with too *much* spoke tension on the side that you now have the tool touching. If the tool touches the locknut but cannot touch both diametrically opposed points on the rim, then there is too *little* spoke tension on that side. This holds for building front (symmetrical) wheels as well as for read (asymmetrical) wheels. You will find that five-speed rear wheels need a little less than twice the tension on the right as on the left and that six-speed rear wheels need almost three times the tension on the right as on the left. You could improvise a dishing tool with two stacks of books on the floor. It takes more patience and care that with the real thing, but it works. Place the wheel on two stacks of books at diametrically opposite points on the rim. Then measure the distance between the locknut and the floor. Flip the wheel and measure again. Before you are ready to measure how centered your wheel is, be sure that the rim is quite straight. Otherwise, the test is meaningless. Whatever you use as a tool, the amount that the wheel is off-center is half the discrepancy shown by the tool. Good luck. Tom Reingold 36 Ellwood St New York, NY 10040 (212) 304-2504