Rear Alignment with Shim

Has somebody used something like aluminium or steel plate cut at an angel and then holes cut into it for bearing and bolts?

 

Thanks, guys. I've always thought the car was odd -- I called it "twitchy" -- so maybe correcting the rear end is worth it. I've heard a lot of controversy about the EZ-SHIM plastic shim device, but if their math is right, you could easily make "real" shims as Toppcat has done and install them on all 4 bolts, based on their calculator tables on their website. Looks easy to go broke getting the alignment checked while you're tweaking, but Firestone's $100 lifetime pass would solve that.

Interesting that the service manual says neither toe nor camber is adjustable. If you don't like shims, and have access to a good machine shop, you could easily mill the mounting surface of the brake assembly (I'm sure there's a better name for that) to make it right.

 

I don't know of any such device made of metal, but the plastic EZ-SHIM does just that. I don't see why you couldn't machine the face of the axle beam or brake mounting plate to accomplish the same thing, but machining a "steel plate" to the thicknesses required (0.000" minimum to ~0.048" per degree of correction) would be a nice trick. You could, of course, reset the "zero" to a larger thickness, but that would increase the rear tread; I don't know how that would affect suspension geometry.

 

I’m just with Toppcat that since there aren’t any plastic parts in there I’m not going to ad one. Adding couple of millimeters to thickness in the thinner side wouldn’t matter much. Milling it is a lot easier if peace is big and is cut down to size afterword.

 

Good enough for me! It's conceptually easy to mill a large washer-like shim to correct both camber & caster. And I think I have a friend with a vertical mill...

 

As I was thinking about how to mill the shim, I decided the math was simple enough to derive values to allow just shimming each of the 4 bolts (actually, only 3, by, referencing the least-shimmed bolt to zero). So for my car, I need to adjust the left rear camber -0.20°, and the toe -0.275°. If my math is right, I need to shim the rear upper bolt 0.0122", rear lower 0.016", and the front lower 0.0063". Standard aluminum or stainless shim stock can be had those requirements to the nearest .001" (or better, if need be), and it doesn't appear to be too difficult to punch out washer-shaped shims. I may buy one EZ-SHIM just to compare their resulting thicknesses to my theory .

More thinking: If we use shims of any kind, that reduces the load-bearing surface of the wheel-axle interface from the 16-or-so sq in of the axle plate to the smaller area of the shims. That can't be good, can it? But I'm an EE, not an ME.

 

I've had my plastic shims on now for 150K miles without any issues. I've checked them from time to time make sure the bolts never loosened up. So far so good.

 

I bought a cheap feeler gauge to use for SS shims, just trying to figure how to punch a neat hole in them to go around the bolts.

 

Have any of you guys used the napa shims as I read in the gen 3 thread these aren't that good compared to those. And if so how would i measure the shim i need. Thanks

 

I just put in EZ-shims yesterday; my rear alignment was similar to OP's original values. I haven't gotten an alignment check yet (will be doing that this week or so) but there's this squirrellyness in my rear tires that is now gone, and the car rides a ton smoother. I definitely recommend that if your rear alignment is out of spec to put in these shims. I have yet to see how it holds up in crosswinds, but I'm hoping for some improvements there as well. By the way I got the red EZ-shim and I did have to bore a couple millimeters off the center with a sandpaper dremel attachment, but this step went smoothly.

I recommend taking your time cutting out the bolt holes in the EZ-shim with a utility knife and cut out one tab out at a time, rather than two, and once you've sliced the tab radially, slowly working it off by bending it up and down, to avoid snapping the shim. I did buy 3 shims to avoid any mishaps, but it turns out one of them was warped, so I'm glad I got both without any problems. But it might be a good idea to have an extra on hand if you're not near an auto parts store

 

The car is definitely smoother and less squirrelly, so there's that. I was zoning out and missed my exit today and almost missed a stop sign, was definitely less stressful on the highway.

But, looks like I spoke way too soon. I just took it in to Firestone today and got this (top is before, about 6 months ago, bottom is after:



Whoops.

I'm going to see if my hub bolts need more tightening, but I'm wondering if I reversed toe-in and toe-out on this?

I'll post the values I used later as they're on a sheet of paper I left at home (I think i changed the ones I had scrawled on the alignment chart), but I was wondering if anyone knows if I got the wrong sign on the toe here (that is, does EZ-shim calculation use the reverse sign of the Firestone aligment page), because that's kind of what it looks like I did

YEAP

9. When installing the shim on the rear left side the numbers on the shim must face away from the installer. When installing the shim on the rear right side the numbers must face towards the installer

So much for double checking and reading the instructions! I suspect I might have gotten the sign wrong on the right side shim as well, despite double checking. At least they're only $13 and the install was straightforward so not bad for a brain fart.

Will post the updated values when I get this worked out, my car stability must be really good when I do it right (it's messing with my head though that my car feels more stable, but there is certain slipping behavior that just isn't there; I guess I'm just in a different mode of bad alignment)

 

I got the corrected shims installed a couple weeks ago. I tightened them a couple times, including right before I took the car in for an alignment. I was pretty happy with the results this time!



As far as driving goes, I did notice that the car drove quite a bit better when I tightened the hub bolts when I went to get the alignment; I think it was still gradually "breaking in", gradual enough that I didn't notice it until I tightened the bolts. I'm going to tighten them again in a couple weeks, and I guess keep doing that until they stay properly torqued, then check them each oil change.

After getting the alignment, well, I guess there's really nothing to say; the car drives straight. It still wanders slightly on grooved pavement, but not nearly as much as before. Same with crosswinds, a heavy crosswind might tug the car over a few degrees, but it's a little more predictable and easier to respond to. And the rear wheel skidding/squirrelling that was happening initially is definitely gone; it's pretty satisfying when I'm expecting it and then I remember I don't have to deal with that anymore.

I can really tell the difference going ~80 on the freeway; the car is much easier to control intuitively and much less stressful to drive at that speed than it was originally.

 

Hi DivideByZer0, i'm trying to take on the challenge for my alignment issue with the EZ Shims or even with metal shims. With the EZ Shims, i'm not certain if they will work per the chart but what do you think?

Front Right Tire
- Camber is (-1.6) and must be within (-1.3 to 0.2)

Rear Right Tire
- Camber is (+0.6) and must be within (-2 to -1) so I would need to adjust to (-1.6 to -2.6)
- Toe is (-1.23) and must be within (0.05 to 0.55) so I would need to adjust to (+1.18 to +1.78)

Alignment results:

Chart:

I'm thinking the EZ Shims would not adjust enough the camber but seems it could address the Toe.

Any advice is greatly appreciated from you or anyone! Thanks!

 

Regarding the RF tire, did the alignment shop try to reduce the amount of negative camber? The front wheels are adjustable to a limited extent by loosening the two bolts at the bottom of the strut and pushing the strut in to reduce negative camber. If that doesn't provide sufficient range, it is possible to get eccentric bolts which can adjust camber as you rotate them in the hole.

Regarding the RR tire, did that tire hit a curb or something?

That negative toe on the RR tire is the worst measurement to be corrected using shims. Hopefully you can get some improvement on the positive camber as well, but adjusting the toe should be the priority.

 

Hi Patrick, thanks for the reply. The alignment shop did not adjust the Camber on the Front Right tire as of yet and was more focused on the issue with the Rear Right Tire as you can see. Instead of paying to do the Front Right and still having to fix the Rear Right, they just gave me the free check and said to come back when i've dealt with the Rear Right to actually do an alignment since its about $70 a pop though i'm leaning towards a Firestone lifetime alignment if i have to make a number of adjustments to the Rear Right.

As for the Rear Right, i planned to use the SPC 75600 Yellow Shims per the Tech Support guy I called. Per their shim chart, I can certainly correct the Toe to be in spec but the Camber will still be off in the range close to Zero (Range should be between -2 to -1) but like you and others are saying, TOE needs to be addressed Soon.

Have you had any experience with Shims and or these Nylon Shims? I've been hearing mixed reviews but more positive than negative but there's just not enough examples to confirm the exact best procedure but from the bits and pieces i've gathered so far, I should be able to do this. I wish i was able to locate metal shims along with a chart or guide. For now, i'll have to try the SPC 75600

Again, thanks for the help and time!

 

I don’t have personal experience using shims but the concept is reasonable. Good luck with their installation.

I have purchased the Firestone lifetime alignment on two vehicles so far and I think that is a good deal. I believe the cost is around $200 per vehicle.