Why does my MGB lean?
by Tom Sotomayor - February, 2003
Why does my MGB lean to one side? This is a question that many people have brought up. Using these methods you can figure out exactly where the problem is.
Lean can be caused by any of the following:
1. The springs are worn/worn out. Worn out shocks will lead to worn out springs.
2. Poor quality replacement springs .
3. Mismatched tires or tire pressure.
4. The mounting points on the body are not correct.
a) The factory put them in the wrong spot.
b) An accident upset the frame geometry.
c) Corrosion upset the frame geometry.
d) The rubber bushes and/or mounting pads are worn, missing or distorted.
e) The suspension has been rebuilt and the nuts/bolts were tightened with the suspension at “full droop” or before it was “bounced” and any “set” has been removed.
Before doing any serious measuring of the lean, you should make sure that your tires all match and they have the same air pressure! Also bounce the car to remove any suspension "set". It is very important to find out if the garage floor is in fact level. This may at first sound like we’re doing it backward, but bare with me. Measure from the same relative points on the car - most people do it from the floor to the stainless belt line directly above the wheel centers. Do this for all 4 wheels. Mark on the concrete (with chalk) the contact patches for all 4 tires, plus the exact points you measured from the floor to the belt line. Move the car. Use a carpentry level to see how much height difference there is between the contact patch and the measurement point (typically over a few inches it should be within 1/8 of an inch or so). Now you’ll need to use a "water level".
A water level can be easily made from a long piece of clear tubing filled with water. Over any reasonable distance the water will find the same level at each end. Of course the ends of the tube must be above the level of the water! For this task a piece of ½ inch ID (inside diameter) flexible clear tubing about 20 feet long will work well. You'll need two (or four) markers that are exactly the same height, about 4-12" high works well. They can be anything - blocks of wood, jack stands, bricks, etc. Place your markers on the contact patches and using the water level, see how far each one is off from the others. Adjust your previous measurements accordingly.
To be more accurate, you could "shim" the floor to bring the contact patches back into level, move the car back into position and then re-measure. This is about as close as you can get without having VERY expensive equipment.
You should also measure the length of each coil spring and the arch height of each leaf spring under static load. If you measure a front spring from the inside top of the cross member (just under the shock) to the bottom of the spring pan, it will give you a comparative length of the coil springs. Do the same for the leaf springs - measure from the top of the axle to the rear frame arch. This leaf spring test WON'T tell you if any differences from side to side are a bad spring or a "bent" frame. You will be able to tell which if you stretch a string from the front leaf spring eye to the lower rear shackle pivot and get a measurement from the axle/spring to the string. Or you can measure from the front and rear spring eyes to the floor, as well as from the axle tube to the floor. You'll need to find the level of the floor in those three spots as outlined above. This will give you the comparative arch of each spring.
With this information in hand, it will be easy to determine where the problem(s) are. From there you can affect repairs.