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Luckily my mechanic is an old and experienced alignment guy. He came over to help me check my car to see what it needs. Starting at the rear wheels, we know the CSM says we need 1/32 to 3/32 of total combined toe in. Before I change anything, we've determined that right now, my car has 8/32 inch of total combined toe in and most of that is coming from the passenger rear wheel/trailing arm. My mechanic also said that my car's driver side rear wheel/trailing arm looks good for now. It sounds like I need to reduce the toe in by approximately 6/32. I also get the joy of changing the stack of shims (original style, not the easier ones with the slots) all by myself and because I know it's not going to be fun or easy I thought I'd ask the forum for assistance IF POSSIBLE to reduce the number of times I have to do this task.
Is there some kind of reference or chart out there that shows how much of a change in the stack of shims I need to make? In other words, to make a 6/32 change, do I take a 1/16" shim from the outside and put it on the inside? 1/32" shim? 1/8" shim? Is there anyway to know without guessing how much of a change in the stack of shims I need to make?
Soak the installed shims and bolt for several days, then pull out ALL of the old shims, carefully observing how many of what thickness or just overall thickness of the shimstack on each side. Assess the condition of the shims and if they are all a rusted mess, replace them all and start fresh. A lot less frustrating than trying to jam in new shims in a rusted shimstack.
Measure the length of the trailing arm from mount bolt to center of axle (as best you can) and determine the radius of your tires. Divide the overall TA length by the tire radius to get the ratio - I’m guessing it will be somewhere around 1.5 to 1.75. Multiply that by the amount of toe change you need to make for an approximate change in shim pack dimension. Since you are trying to reduce toe in you would need to reduce the shim pack on the outside by that amount and adds shims on the inside by the same amount.
It’s probably not going to be a perfect adjustment but should get you pretty close and then may have to make a slight adjustment..
Or, depending on what equipment or set up you are using to measure toe in the rear, if you can set it up to measure while accomplishing this work, pull the bolt and all shims out. Put the bolt back in. Pry the forward part of the trailing arm back and forth in the pocket until you get to the desired toe in reading on the equipment.. Then gently, so as not to disturb the setting, trial fit shims in the gap until you have it full without having to force them in. Getting a set of the slotted shims will work better for this. Then substitute your other shims in the same pack thickness into position and tighten down the bolt and double check toe. Make minute adjustment as necessary.
Soak the installed shims and bolt for several days, then pull out ALL of the old shims, carefully observing how many of what thickness or just overall thickness of the shimstack on each side. Assess the condition of the shims and if they are all a rusted mess, replace them all and start fresh. A lot less frustrating than trying to jam in new shims in a rusted shimstack.
I did not mention it in my OP but all the shims are new, shiny, and slippy; they might be a little dusty but they're not crusty or rusty. I should have posted pix as pix are always helpful. I'll do that now....
After replacing the trailing arm bushings which were wider than the stock bushings, the factory shim packs would need adjustment accordingly.
A driveway rig of a long enough 2x4 wood length with uprights on the ends set at center wheel height was set up.
A taut string ran from the top of the uprights front and rear. The idea was to parallel both the front and rear wheel rim edges to read the same measurement on the tape measure. The steering wheel set the front wheel adjustment for parallel for front and rear rim edge.m measurement. The string was also adjusted accordingly in/and or out as needed.
Once the parallel measurement was set the distance to the front of the rear wheel rim edge was measured. The toe in was set sliding the rear wheel in position with the shims out. Different thickness shim packs were carefully tried to fit inside and outside of the mounting bolt pocket bracket.
It took a few tries to get the rear toe dialed in. The best I could get was 1/16 inch per side toe in. I figured with normal wear and tear it would eventually work out ok. There have been no problems in handling or abnormal tire wear.
One more question... Before disconnecting the the leaf spring from the trailing arm (to change the shims around), am I going to want to loosen the 4 bolts that hold the leaf spring to the differential to avoid cracking the tabs of the differential cover?
Dumb question here; Did you check the camber before looking at the toe? Another dumb one; Looking at your picture the car looks to be in the middle of assembly. This alignment check was done roadworthy, and sitting on all 4 tires I assume? Also, I've never had to remove/loosen the spring to change the shims. Just jack the corner under the end of the leaf to remove the load on the arm (also disconnect the sway bar link).
Dumb question here; Did you check the camber before looking at the toe? Another dumb one; Looking at your picture the car looks to be in the middle of assembly. This alignment check was done roadworthy, and sitting on all 4 tires I assume? Also, I've never had to remove/loosen the spring to change the shims.
Yes, we did the camber before looking at the toe.
Yes, sitting on all 4 tires.
That picture above (with the loose bolts) was was taken a long time ago. I was using that picture just so people knew exactly which bolts I was inquiring about.
Originally Posted by JF in MI
Just jack the corner under the end of the leaf to remove the load on the arm (also disconnect the sway bar link).
One more question... Before disconnecting the the leaf spring from the trailing arm (to change the shims around), am I going to want to loosen the 4 bolts that hold the leaf spring to the differential to avoid cracking the tabs of the differential cover?
No. Just be sure you did not torque those bolts until you had full weight on wheels.
No. Just be sure you did not torque those bolts until you had full weight on wheels.
That picture above (with the loose bolts) was was taken a long time ago. I was using that picture just so people knew exactly which bolts I was inquiring about. Those bolts were indeed torqued properly after the weight of the car had settled the suspension. Thanks.
Alignment questions
