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MG TD TF 1500 - Uneven Tire Wear

I am in the middle of restoring my TD's wheels and putting on new tires. The old drivers side (LHD) front tire has been wearing heavily on the outside. I always thought that the only allignment adjustment was toe in. If the toe in was not correct, wouldn't both front tires wear equally? Nothing appears to be bent in the frontend. Is there any way to adjust camber? Its really strange; when looking at TC's and other old cars, they appear to have a good deal of positive camber, yet uneven wear is not an issue with them.
Steven Tobias

Steve --- On my first TF I had to change the front shocks and wound up with a bit of negative camber (bottom of the wheel pushed out). Never did get that straightened out.

Always thought the shock arm was wrong (or bent). The TF had Armstrong Shocks as I remember.
R. K. Jeffers

Yeah, My TD has Armstrongs. It appears to the naked eye that there is some positive camber on the side in question. I've noticed in some of the archived posts, mention of shims placed under the shock base. In fact I think that Dave Braun had found them when he was tearing his TD down. It seems to me that one would have to raise the shocks a great deal to have even the slightest effect on shortening of the top link and thereby subtracting camber.
Also, Jeff, how did this negative camber effect tire wear?
Also, Dave, If you read this...Did you keep the shims when you reassembled the front end? How did it work out?
Steven Tobias

Hi Steve,

The angle change required to affect camber or castor is quite small. The shims are detailed in the front suspension portion of my website. As I state there, I reassembled my suspension without the shims. I found the front LH tire picking up dirt in an offside pattern, and realized that this was the side that formally had the shims. I reinstalled the shims (simply by loosening the shock mounting bolts and sliping them back home) and viola, no more funny dirt pattern.

There were a lot of cars with lever shocks in the 30s and 40s, which used the lever arms as the upper A frame. Shimming was a common way of effecting wheel alignment. Perhaps finding a shop versed in this proceedure, or who at least can do the math, would be needed here.

Now I have some questions about a simple shower enclosure...

warmly,
dave
Dave Braun

Steve, I have the same problem with negative camber and have measured and changed back to old spindles, etc. Can't correct it and drives perfect, it's just when it is parked that visually upsetting. Haven't observed any tire wear, and by the time the tires wear out they will be too old anyway!Bob
R.AF. Robert Finucane

Bob, That's interesting. I'm wondering if there isn't something other than camber going on here! I am getting very eneven wear on this tire only.
Dave, fortunately, there are no caster, camber or toe-in adjustment issues with our showere doors! The Bellanca did make me crazy, however!
Steven Tobias

Gentlemen,
The front tires on my TF have developed a wear pattern on the outside two inches (5cm) over the last few years. Then last year I had all of the shocks rebuilt. Would this make any difference in the wear, or will shimming of both shocks be required?
Gene
Gene Burgess

Steve, I am still suspect with the shock arm length. Mine are Girlings (early 50) and sent them out 35 years ago for a rebuild, can't remember where, don't know if I got the same ones back. Tried Dave B. method with shims, no luck. Just noticed picture on my screen of the TD shows negative camber greatly, wish I could duplicate that! Bob


R.AF. Robert Finucane

Steve,
If you look at the line drawing fig K3 in the workshop manual there is quite an amount of neg
camber at full bounce and rebound. Only if you have negative with "A" arms horizontal do you have a problem.
Having the trunnions incorrectly centred on the cut out on the king pin can mess up the camber. If you are down on the lower and up on the upper it will move the shock link up giving a bit of neg.
It also messes up the king pin inclination which makes the wheel want to tramline on road markings.

Ray TF2884
Ray Lee

How about finding a shop with a good wheel alignment rack? That would tell the story at least in a passive position. There are really detailed drawings of the frame in the factory manual. If it is really way out, you may want to measure the frame where you can to see if it is torqued a bit (can't do many with the car assembled, but some you can). My 280Z was whacked in the front when nearly new, and the right front camber has always been out quite a bit (no adjustment possible), never had any wear issues. Also, how many miles/how old the tires? Were they ever rotated? George
George Butz

Ray,

Can you even install the bushing in place if the trunnions are not correctly centered on the swivel pin? It would require a full turn out in one direction or the other to get ir wrong, and I remember thinking about this AFTER I assembled the front suspension, having used the workshop manual but then having a moment where I wondered if I counted the turns right. I decided that there wasn't enough slop in the turns.

Another aside is that full bump or rebound is only a 1-1/2 degree change in inclination.

Warmly,
dave
Dave Braun

Does anyone know where one can purchase alignment shims that can be slid under the front shock mounting pad, around the hold-down bolts. These can be seen in photos that Dave Braun has graciously posted at http://www.dbraun99.com/mgtd15470/
Steven Tobias

Steve,

You could do your car and probably about 30 other cars with this kit for $7.99

http://www.jackstoolshed.com/product/HWA-ASS144/Automotive_Alignment_Shims_Assortment__144_Shims.html

no interest, etc.

warmly,
dave
Dave Braun

Hi Dave-Funny, after I posed the question, I found the same site. The only thing that bothers me is that the shims are galvanized, whereas most of the huge commercial assortments are stainless. I will probably use Jack's shims. Afterall, the rest of the car is plain steel!
Dave, It looks like your shims totalled around 5/32. Did this really make a noticable difference? My positive camber is enough to be apparent to the naked eye. Thanks
Steven Tobias

Steve,

Mine was very minor, but noticible on the tread. The .160 the shims provided probably moved my shock arms out and down a tenth. It would be a simple matter to have the camber measured, and calculate the distance the upper shock arms must move out and down (or up and in) to correct the problem. One thing that is important is that your springs are somewhat equal and the A-arms on the lower pans parallel to the ground when the car is setting. Suspension design tells us that Springs don't change their spring RATES with age, but can change their spring HEIGHTS. If you have new springs, your wheels may lean in at the tops, too weak and your wheels may still lean in, as full bump and full rebound both result in a deflection of the top wheel travel to the inside.

warmly,
dave
Dave Braun

I have been following this thread as I put a 4.3 rear end in my TD and did a 2000 mile trip to Canada last summer. On return I noticed wear on the insides of both front tires more on the right than the left. I’m going to do as George B. suggests and have the front end professionally checked on an alignment machine for toe in. They have told me in the past that the camber was not adjustable, so I may need to go the shim route. Here is my dumb question; do the shims go under all four bolts, or just two? John
P.S. if you spell camber as camper the spell checker won’t pick it up.
John Hambleton

John, If the front tires are wearing semi-equally on the insides, your wheels are probably toed-out. This can be checked easily. Measure between a couple of spots on the tread of the 2 tires that are toward the back of the car and then push it forward so as to measure between the same spots that are now at the front. The toe-in/out should be 0". This is easily adjusted by screwing the tie rods in or out of the end ball joints. Be carefull to adjust equally from both sides, as this will affect the centering of your steering wheel. The shimming that we discussed earlier in the thread is for camber-which affects each wheel indivdually. I would for any toe-in or out before pursuing this. If you shim under the shock absorbers, you would go under the 2 outboard bolt holes to decrease camber (lean the top in) or under the 2 inboard holes to increase camber.
Steven Tobias

John,

The camber shims are shown on my website, www.dbraun99.com and it's not a dumb question. The shims would go wherever a wheel alignment indicates a need to adjust camber or castor. They come in varying thicknesses and the shop would install them until one, two or three of the mounting bolts were shimmed to varying degrees.

I've used the little toe-in adjuster sold by Moss and other folks to good effect in adjusting toe.

I have about 2000 miles on my TD since restoration, and see no adverse wear on my tires at this point.

warmly,
dave
Dave Braun

Caster and camber are not tire wearing angles unless they are considerable out of specification caused by, for example, an accident or a heavy duty hit against a curb. Tire wear can also be caused by worn steering components such as tie rod ends, bushings, etc. Worn steering components usually result in an irregular wear pattern (bumpy wear).

If your wear problem is located on either the inside or outside shoulder of the tread and is uniform, it is almost always the result of an improper toe adjustment. To determine if you have a toe problem, run the palm of your hand over the tread surface from outer to inner and then in the opposite direction. If you have a toe problem, the surface will seem rough in one direction and smooth in the other direction. If the tread seems smooth while moving out to IN then you have a toe-IN condition and vice versa for toe-out.

To correct toe, follow the below procedure:

Checking/Setting Front Axle Toe-in

Toe-in can be easily checked on any automobile and with a little effort corrected to the required 1-mm plus or minus 1-mm or 1/32nd plus or minus 1/32nd. To complete the task you will need masking tape, a tape measure, preferably metric, a pen and an able helper.

You start by driving the car forward and backward on near level ground for at least 5 tire revolutions in each direction while fiddling with the steering wheel to ensure that the wheels are pointed straight ahead. The last step in this part of the process is to back the car to its starting point and stop the engine. Now, take your hands off of the steering wheel and have your helper push the car forward for about two tire revolutions. If the car tends to roll use the hand brake only to stop and hold the car in place.

The measurement phase consists of placing a piece of masking tape, about 2-3 inches long, at the rear of each tire. The tape should be place vertically near the center of the tire tread. Next, using your pen, place a small horizontal tick mark at the inner edge of each piece of tape. The tick marks should be as high off the ground as possible while still being able to have a clear line of sight from tick mark to tick mark. With the aid of your assistant, CAREFULLY measure the distance between the edges of the each piece of masking tape at their respective tick mark locations. Be sure that the tape measure does not touch any part of the underside of the car. Now, push the car forward, without touching the steering wheel, while carefully observing the masking tape. Stop the car, using the hand brake only, when the tick marks are as high off the ground as possible while having a clear line of sight between the tick marks. Remeasure the distance between the tape edges at their respective tick marks. Now, subtract the two measurements to obtain the toe value. If the distance measured at the rear of the tire is greater than the front, your front axle will be toed-in. It is easier to get an accurate measurement if you use the 100-mm or the 4-inch as the starting point because we are not interested in the actual distance but rather the difference between the front and rear.

This method of checking front axle toe is very accurate because you are measuring between the same two points on each tire while the points are at both the front and rear positions. Tire and wheel run out and tread pattern irregularities are accounted for.

If you find the your toe is out of specification you can make proper adjustments. Start by changing the front distance by one half of the error. Then push the car forward (never backwards) and remeasure the rear distance. Make a small toe adjustment if necessary, and repeat the entire process until you have reached the desired toe-in value. After you think that the toe is correct take the car for a short drive and repeat the measurement process.

Although time consuming, I can assure you that this toe measurement technique is at least as accurate, and more reliable than alignment shops offer. This is a direct measurement that does not rely on equipment calibration to ensure accuracy. If you want caster and camber measured/corrected or a four-wheel alignment on a modern car you must go to an alignment shop. Use the above method to check their work. You will be surprised! Have you ever noticed tire wear after 6-months of driving after an alignment, taken the car back and told that you must of hit a curb or a chuckhole. Sure…
Frank Grimaldi

This thread was discussed between 18/02/2009 and 12/03/2009

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