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MG MGA - Right rear rub

This one has me a bit stumped. When driving my 58 "A" with a passenger on board, I often hear what sounds like tire rub when the car travels over a bump. Never happens when I'm driving solo. BTW the passenger is my my wife and she only weighs a mere 110 lbs(the "mere" is in case she sees this).

I pulled the rear shock and it seems fine; no leaks and the lever has good resistance through its travel motion. I sat on the rear wing and hopped up and down, but I cannot get the tire to come close to the fender well. Any ideas besides leave the wife at home? Leaf spring perhaps?

Fran
F Valenzano

The springs may be a little soft and allow too much vertical movement of the axle but the bump stops on the top of the axle would usually prevent this. Check to make sure they are fitted.
Could it be brakes rubbing? possibly if the wheel bearings have some play allowing the hub to move around a liitle, or maybe if the drum is slightly warped it could rub on the backplate.
Are your wheels ok, old rivitted rims can work loose?
Rear axle loose or slightly out of position ( not centralised )
Most of the above would also cause the rubbing problem during fast cornering too but rather than test that theory out, have a look at the wheels, axle first!
Im sure Barney will give you a better explanation
Hope you sort it soon
Colyn
Colyn Firth

Last time I had something like this it was actually the universal joint at the back of the propellor shaft. However it was more of a metallic clunk than a tyre rub. It only happened with two up because the extra weight changed the angle of the yokes and revealed wear that was normally quiet. Noises are funny sometimes and don't always seem to be coming from their actual source. It might be a related problem because with more weight on board the angle of the prop shaft changes and may be rubbing on something in or around the tunnel. Worth a look.

Cheers

Malcolm
Malcolm Eades

When traveling over a bump? Do you have a front sway bar installed? After fitting poly frame bushings to my sway bar it creaks and groans with gentle undulations of the road (one squeak or groan per vertical cycle). That could be load sensitive. Adding the passenger tilts the chassis slightly, changing loading on the sway bar frame bushings,

The poly bushings in the A-arms never made any noise, but maybe could for other people.

Maybe the edge of a brake drum rubbing on the brake backing plate (one scrape per wheel revolution).

If you have a stress crack in a steel wheel it will possibly "tick" once per revolution, sounding much like a loose spoke in a wire wheel. Such cracks are usually found hiding behind the hub cap (small wheel cover).

Original size tires on original type wheels will be nowhere near to rubbing on anything, even with badly sagging suspension. There is lots of space for larger tires, as long as the original wheel offset is not changed.
Barney Gaylord

Fran

Lateral thinking cap on here. Sounds migrate around the car and rarely come from where you think. It's probably a creak in the seat frame or perhaps the floorboard to which the seat is bolted.

Steve
Steve Gyles

Fran, is there any possibility of the handbrake cable being snagged or pehaps tied up a bit too neatly so that when the axle moves, it pulls the brake on a bit?
Lindsay Sampford

Well guys you have certainly given me enough assignments to check out the possibilities.

FYI: No front sway bar, the rear splined hubs are new, as are the bearings. 4 new tires are Firestone Affinity radials size:165/65x15(wider yes, but they have plenty uf room within the wheel well). They are mounted on new alloy Mini-lite 15 x7 wheels.

I am quite certain its not tire rub as the rubber shows no scuffing or any other damage.
Certainly will be checking the bump stops as Colyn pointed out and also the handbrake cable mentioned by Lindsay.

Is there a way to check for play in the UJ that would indicate a problem?

Thanks chaps...I will keep you posted as I sort this out.

Fran
F Valenzano

Okay guys, here's what I have discovered after driving the car 50 miles this past Sunday.

During the trip with passenger aboard, I drove over a couple of random dips in the road and once again heard the right rear tire rub. This time I actually smelled burned rubber for an instant with the rub. Upon returning home I inspected the tire and sure enough, there was evidence of contact (glazed mark on the tire in glacier blue) between the fender well and the outboard tire surface. This mark is in on the sidewall, just below the tread surface.

I checked to be sure the wheel knok-off was secure on the hub, and found no problem there. Took a straight edge and discovered that the right rear tire side wall protrudes 5/8" fron the edge of the fender well, while the left tire protrudes only 1/4".

So my question is what would cause a difference of 3/8" between left and right rear tires protruding from the fender wheel? I did have both rear hubs replaced about 4-5 months ago. The new hubs were pressed onto the axle at a machine shop. The wheels are 15" minilite style alloy wheel from Moss Motors with knock-offs. Not inexpensive!

If there a chance the RR hub was not pressed onto the axle far enough?

Thanks
Fran
F Valenzano

Fran, I wouldn't be surprised at 3/8" discrepancy on the bodywork. Am I right in thinking your minilites are 7 inches wide? ("They are mounted on new alloy Mini-lite 15 x7 wheels.") That seems a bit wide for a 165 tyre that would normally be fitted to a 4 1/2 inch wheel. Also have your new wheels got the correct off-set.

Lindsay Sampford

Lindsay - the fact that only the right side rubs is what is causing my confusion. One would think if the tires were a bit wider, as mine are,(165/65x15)both tires would be subject to a rub unless the right side suspension is the weaker of the two.

There is plenty of vertical room above the tire in the well itself. As far as the offset is concerned, Moss Motors has sold hundreds of these wheels with no issue for MGA, so I suspect the offset is correct.
F Valenzano

Can you measure from the frame instead? That would show if the body was skew.
Art Pearse

Fran, as I said earlier, it wouldn't be unusual for the body to be out with regard to the frame and consequently the rear axle. With the standard size wheel/tyre you would probably get away with it but slightly larger will show up any clearance problems. What does the tyre actually hit? If it is the inside of the fender rather than the flange, it seems like your suspension is going down quite a way. Just measured from the ground to the highest point of the wheel arch flange on my car, unladen, and get 26 inches both sides, my springs are old. How does that compare with your car?
Lindsay Sampford

Check the installation of the rear axle. If it is off or out of position this could be the cause of your measurement difference. Adjusting the rear axle (if necessary) to equally compensate for the 3/8 in difference ....is not a large amount of movement.
Gordon Harrison

Gordon, isn't the rear axle located positively to the through-bolt on the leaf spring? I don't think you can slide it from side to side.
Lindsay Sampford

Fran, --- don't worry about 3/8" difference in space on either side. That translates to only 3/16" lateral offset of the rear axle, or the fenders could easily be that much different in shape. The real problem is that the wheels and tires are set way too far outboard, too close to the fenders on both sides. The wheels have incorrect offset placing the tires too far outboard. This problem gets kicked around various forums periodically, and once very recently, although it is more often in reference to bolt-on wheels.

Get the rear of the car up and measure track width, distance between center lines of the rear tires. This is originally 48-3/4 inches. If you're much wider than that, you just have the wrong wheels.
Barney Gaylord

Barney, et al:

Just spoke to tech assistance at Moss Motors regarding the knock off wheels and tire rub on my car. They say that the offset on their knock off alloy wheels should not cause tire rub because under a normal suspension setup, there should be plenty of vertical gap between the sidewall of the tire and the inner lip of the rear fender; even with wider tires.

By all accounts they feel that the rear suspension (leaf springs) have lost their camber which lowers the frame and also the rear-most section of the body. This means there is not enough lift to provide normal fender gap, causing the tire sidewall to rub with suspension load.

After examination of my leaf springs, they are in fact flattened with little or no arch. I dont think there is a way to readily test leaf springs for proper camber...is here?

Before I make the decison to but two new springs, does any of this sound like a reasonable explanation?

Fran
F Valenzano

The main leaf of the leaf spring should be absolutely flat under loaded condition. See here:
http://mgaguru.com/mgtech/suspensn/rs105.htm
Barney Gaylord

Lindsay,
If your spring bolts are loose or your rubber pads are in poor condition the springs are able to move and this may be causing the rubbing. (see Mr. Gaylord's website). Also it could be possible (althought rare) that the springs are not mounting squarely with the axle.
Gordon Harrison

This thread was discussed between 01/04/2010 and 15/04/2010

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