The MGA With An Attitude

At 09:27 AM 3/1/04 -0500, Roger Dotson wrote:
>".... regarding wheel truing. .... one needs some adjustment. I believe I slightly damaged it .... hit a bad chuckhole."


>".... this particular one is a bit out of round ...., and it cannot be balanced out on the machine."

First be sure you are not confusing tire wobble with wheel wobble. If you did not notice this before installing the new tires, then it is possible that the problem is with a faulty tire, and not with the wheel. A hard hit on a pothole or rough railroad crossing may damage the carcass of a tire as well a bending a wheel. See prior page on the subject of Wobbly Wheels or Wobbly Tires.

If the rim (not just the tire tread) wobbles out of plain or out of circle more than 1/8 inch, then the wheel needs repair or adjustment. You generally have to dismount the tire from the rim to do any wheel repairs. Remove tire and tube, put the wheel on the front hub, and spin it.

If the wheel runs true most of the way around, but the edge of the rim wobbles just for a distance of 6 inches or less, then you have a bent rim that needs to be straightened. For a painted wheel you might try that yourself, and repaint it afterward. Damage from hitting a big pothole straight on commonly results in bending the edge of the rim radially inward toward the hub, and also laterally slightly outward. You cannot correct a local kink in the edge of the rim by adjusting spokes in a wire wheel.

Lay the rim on the floor with the bent edge upward, and stand with your feet blocking the wheel from sliding across the floor. Use a wide flat punch (at least 1-1/2" wide) or use a cross peen hammer for a punch. Place the punch inside of wheel rim bead and angled inward about 45 degrees to 60 degrees with the strike end of the punch leaning toward the wheel hub. (Wear safety glasses when hammering anything). Strike the punch straight on a firm blow with a heavy hammer (2 to 5 pound hammer). Repeat as necessary to drive the bent edge of the rim back to its original position. Place wheel on front hub and spin to check for straightness. Target is to get the rim to run true with 1/8 inch in plane and within 1/16 inch radially with minimal local wobble.

In some cases you may be able to straighten a bent steel wheel (stamped steel center, not spokes or solid aluminum), one which may have taken a side impact and is bent slightly out of plane. Bolt the wheel on the car and give it a spin. If it has a general overall wobble continuing all the way around the wheel, but has no local kink in the edge, this may be a candidate for a home straightening job. For this you need a hydraulic ram, the type commonly used for body straightening.

Mount the crooked steel wheel on the rear axle of your solid axle car (not recommended with independent rear suspension). Spin the wheel and watch the wobble to determine the point on the rim which is closest to the centerline of the car. Rotate the wheel to put that point at the bottom. Position the hydraulic ram (with appropriate extensions) between the lowest point on the wheel rim and diagonally across to the leaf spring just below the axle on the opposite side of the car. Apply force with the ram to push this innermost point of the crooked wheel outward. Fear not for the integrity of the rear axle assembly, the springs or wheel bearings. The axle assembly is a very robust piece of equipment and can easily take this level of force and stress without damage.

The steel wheel will have a considerable amount of spring back potential. If you push it half an inch an release the pressure it will spring right back to the original position, still as crooked as it was to begin with. You may push it two or three times, each time successively farther. You will have to push it far enough to apply sufficient stress to exceed the yield point of the steel hub so it will actually take on a little permanent bend a little in the direction desired. Then when you release the pressure and it springs back, it will not spring back all the way to the original starting point, but will have taken a small permanent offset. After each push and release, spin the wheel again to view the remaining wobble. Position the rim point remaining closest to the centerline of the car at the bottom, and give it another push with the ram. As before, the target is to get the rim to run true with 1/8 inch laterally with minimal local wobble. Once you get rid of most of the overall wobble you may notice some small local bend in the edge of the rim, in which case you can back up a few paragraphs to attend to the local kink.

Repaint the wheel after you get it straight. If you have a chrome plated rim you have to deal with any damage to the plating. Re-plating a wire wheel might require total disassembly of the wheel, removal of all spokes to work with the bare rim. In that case it may be cheaper to buy a new wheel, as the labor to reassemble the wheel in correct alignment may be prohibitively expensive.

If a wire wheel has some stretched spokes, it may have a relatively large wobble out of plain or out of round without having any local bending. In that case you may be able to true it up by adjusting the spokes. See next page for truing of wire wheels.

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