The MGA With An Attitude


At 11:48 PM 11/4/02 +0000, Anna Pavao wrote:
".... Original non-spoked wheels seem very scarce and your point about cracked original wheels is quite valid. I wonder if you know of a suitable replacement wheel that is readily available that takes the stock hub or a source for a clean set of original wheels?"

Original type steel wheels are not available as new replacement parts. Some vintage Volvo wheels look very similar but lack the three conical nubs to attach the hub cap. Ditto for some Triumph wheels (no hub caps), TR3 I think, but the Triumph wheels might be a bit stronger and still about the same width and offset. Used original type wheels are commonly available, however, straight ones are hard to find. I have just about come to the conclusion that there never was such a thing as a straight steel wheel for the MGA, as they may have all been a little wobbly from the factory, some just not as bad as others.

A spinning wobble of more than 1/4" total (+/- 1/8" out of plane) may be noticeable as a shake at road speed. Wheel mounting shops may hang as much as pound of lead weights on the wheel attempting to spin balance it. They might attach 8 ounces of weight in one location on the rim, and another 8 ounces on the opposite side of the rim 180 degrees around the wheel. This is intended to offset or counterbalance the mass of the wheel that is out of plane because of the wobble. This works, and it can be made to spin smoothly in good balance. But the wheel with the tire on it will still be running with that out of plane wobble, which can still cause some wobble in the steering wheel. If you can identify the worst offenders, put those on the rear axle and the straighter ones on the front.

If you find wheels that run true in plane within 1/8" total you're doing well, and probably won't notice any wobble in spite of what it looks like when it spins. The key is to be running concentric, so the rolling radius is equal all the way around. The worse problem is that many of these 40+ year old wheels have taken a beating over the years and may be warped much worse, or may have bends or dents in the edge of the rim that might cause a worse wobble. Or the dings might even be bad enough to prevent the tire from seating and sealing properly on the bead. When buying used wheels it good to inspect and test before you hand over the cash. You need to mount the wheel on a front hub and spin it to see how straight it runs. For wheels on cars currently on the road, perhaps half will run true within 1/4". For dismounted used wheels being sold without inspection and without guarantee, the record might be only 25% running true within 1/4", and only 10% running true within 1/8". I recently found a set of 4 which had been bead blasted and powder coated and really looked sharp. Two of those went into the nearest dumpster. Fresh paint has little to do with the straightness of the wheel.

For what it's worth, I don't have a pound of lead weight on any of my wheels, because I don't pay to have them spin balanced. I gave that up as a lost cause years ago after repeated balancing failures. I use a static balancer, one of the $49 units from J.C.Whitney with the bubble level in the center. Two small weights of 1/2 ounce each is usually enough to balance a wheel (occasionally 3/4 ounce each). I put them on the outside of the rim and mark around them with a felt tip marker. If one should happen to fall off it can be replaced without removing the wheel from the car. In the end I settle for this being "good enough", and just learn to live with any tiny wobble that may still remain at road speed. On a few occasions I have paid good money to have them professionally spin balanced and ended up with worse wobbles. After a rudimentary bubble balancing, most of the remaining wobble comes from the wheel being crooked, not from being out of balance, and another pound of weights doesn't help much.

Before shopping for replacement wheels it is important to know the correct required offset. Original MGA steel disc wheels are 15" diameter and 4" wide (between the rim flanges) with 1-3/8 inches offset (35mm). Wire wheels have entirely different configuration but run in the same track width. There was a factory optional 60-spoke wire wheel that was 4-1/2 inches wide with same offset and track width.

Most new wheel offset spec's (bolt on wheels) will be stated in millimeters, so look for 35mm +/-3mm (or 32mm-38mm). Many alloy wheels advertised as "suitable for the MGA" do not have enough offset regardless of what the supplier may say, some being in the 19-mm to 28-mm range, which is grossly insufficient. Those may work with 165 tires but will likely make 185 or 195 tires rub on the fenders. So always insist on knowing the offset before you lay down the money.

For bolt-on wheels, the center hole and bolt pattern is a stock Ford pattern (4 bolts on 4-1/2" basic circle), and any 4-bolt Ford Falcon or early Mustang wheel will bolt onto the MG. The problem is the offset in the MG wheel. Most Ford wheels have about zero offset, meaning that the flat inside surface that mates up with the hub on the car is about on the center line of the rim. The MGA wheels have 1-3/8" offset with the running center line of the wheel being closer to the center line of the car, making for a narrower wheelbase for the small sports car. Except for being narrow, these dished out wheels look like they might belong on a front wheel drive car. And therein lies another source for some nice bolt on wheels.

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