EZ SHIM and my mistakes

Every now and then I rediscover something that 'defeats me' and sad to say, it has been EZ SHIM by Specialty Products . . . and I did it to myself.

The EZ SHIM consists of two plastic disks that have a slight offset. By changing the angle between the disks, their slight offset thickness allows them to compensate for both toe and camber:

This one removed after five years of service, more about this later. It really is a clever solution and there are two ways to adjust the index numbers:

• online tool
• lookup table with the part instruction

I had no problem adjusting the chamber but toe was a big problem.

Five years ago, I used an EZ SHIM and apparently adjusted the toe to 2x the expected correction. So I only got 45,000 miles out of our Sumitomo T4s. It wore the edges as if I'd under inflated the tires. What I failed to do is get an alignment readout early enough to tell I'd screwed it up. So replacing the no longer made, 51 psi Sumitomo T4s, I went with oversized, Yokohamas.

First Firestone Alignment With Yokohamas

This is what told me the camber was right but the toe was off by a factor of 2. Huh? So I took the wheel off and reversed the shim to get a second reading. Maybe I'd mounted it wrong.

When I took the old shim out, I found the outer disk was split because the wheel axle is slightly larger than the EZ SHIM inner diameter. This is the only product 'defect' that is easily fixed by making one cut so the EZ SHIM can fit around the hub.

Second Alignment Reading

OWCH, the toe was over compensated the other way. The 19/1 index number got the camber perfect but the toe compensation was twice as much as expected on now sign reversed!

Third Alignment Reading

I took the passenger shim out and got a baseline. Then I prepared two EZ SHIM, one for the left and right wheels. I put the passenger shim in but when I went to do the driver side, the two metal shims I'd experimented with before fell out! OWCH! The driver side EZ SHIM would not work. So I put the driver side wheel back on to get a baseline measurement.

Fourth Alignment Reading

The passenger side is perfect but now I have the offsets to set the next EZ SHIM. So the driver side comes off and another EZ SHIM prepared and installed.

Fifth Alignment Reading

HOLLY CARP! The toe has over compensated! So I thinking I put it on backwards, I took the driver side wheel off and reversed the shim.

Sixth Alignment Reading

WHAT THE F**K! The toe went too far the other way. GERRRRR!!!

Upon reflection, it occurred to me that both errors could be explained if the toe setting were 2x the expected value. A spreadsheet quickly confirmed that was the error . . . hummmm just like the first one.

I went back to the printed table and noticed that there are multiple columns: inches, degree fractions, and degree minutes. Firestone gives degree fractions BUT if you use the inches column, you get 2x the toe correction . . . my symptom!

So I prepared another EZ SHIM with the right numbers and mounted. I haven't taken the car back but will later this week. But I am sure both left and right wheels have exactly the camber and toe I want because I finally followed the instructions.

It now takes me about 20 minutes to swap out the EZ SHIM:

1. Crack the lug nuts.
2. Raise the car and put a jack stand to hold up safely.
3. Remove the tire, leave the drum.
4. Slip a small flat just under the wheel rotation sensor connector and wiggle off.
5. Remove the top 17 mm and bottom 12 mm bolts.
6. Carefully pull off without rotating.
7. Cut the EZ SHIM, lower opening so it will fit.
8. Make sure numbers towards car on left, driver side and outward for the right, passenger side.
9. Use a large, Phillips head screw driver through a hole and the wheel assembly to align the threads.
10. Put the wheel back on with the Phillips head driver keeping things aligned.
11. Remove the phillips once one is started and take care to avoid cross threading.
12. Tighten to 44 ft-lbs using cross-bolt pattern. Come back a week later to confirm.
13. Put tire back on, lug nuts tight.
14. Lower car and finish torque the lug nuts.

So why did I post my tale of self-imposed woe. So you might avoid my mistake. A four-wheel alignment using EZ SHIM is not that hard but misreading the table . . . teaches humility.

Bob Wilson

 

So this morning, I had a chance to compare the GPS vs. trip meter:

• 6.52% further over the trip meter indicated distance
• indicated 42 mph = 44.7 mph true, the hybrid threshold

I'll go out at lunch time and run some laps. This will let us know what sort of MPG we can see on an NHW11 with an overdrive gear set.

Bob Wilson

 

So I ran a quick sanity check:

• 84.57 MPG_true = 106.52% * 79.4 MPG_indicated
• ~989 miles expected maximum range for 11.7 gallons usable

Bob Wilson