EZ Shims for rear alignment?

Hey guys,

Has anyone used EZ Shims to align the rear end before? My rear wheels could definitely use some adjustment. I have one with -0.71 camber and +0.01 toe. The other sits at +0.01 camber and -0.26 toe.

I was looking at the EZ shims, and their calculator says I can dial that in quite a bit. They have installation videos and resources, so I'm pretty confident I can handle the installation myself, since I have a recent alignment printout to go off of. (RockAuto has ACDelco and Moog shims, but the information seems limited on those products)

Here's a link to the product EZ Shim recommends: http://www.spcalignment.com/componen...AFrom&to=USATo

Thoughts?

- Zach

I've been thinking about these for my car. In to see how this goes

I have those too. Haven't gotten around to using them but as far as thoughts.. For regular driving I was thinking zero toe and max camber. I don't think it is possible to get too much camber with these shims. I guess it depends on what you're using the vehicle for though. I could see not wanting any camber if you're tracking it and want to loosen up the back end. Maybe even wrong ways camber and toe out if you're desperate to loosen it up like autocrossing or something.

Most modern alignment machines will give the type, angle, and offer a template to use to cut your full contact shim for installation. If you have an alignment done, you can request they give you the specs.

I've been to three alignment shops in the past year and nobody yet has really known what they're doing at all. The first guy put my wheel against my strut and I rubbed some inner sidewall off before noticing. This last guy I went to tried to argue what negative camber was cause he read his computer wrong and didn't have any base knowledge. It's sad in my town.

That being said, I want -0.2 degrees camber and about 0.05 degree toe in on each wheel. This will give the back stability in cornering and straight line tracking without being radical. I can then set my front from -0.5 to -0.7 degrees camber. -0.7 would keep the perfect front/back difference, so that's what my front wheels are set at right now. Going to be watching for tire wear, but I'd like to get the back wheels lined up =]

Good plan of attack.

We used a company called Aligncraft to get our shims from. Go plastic, they don;t rust and cause the wheels to go all wonky.

Read the instructions for those shims once. Not as easy as it appears.

I have used the blue shims with the spin wheel in the center. They work well.

The rear of our cars don't really need a lot of negative camber because of the way the suspension works. I only run about -.5* or so back there and have NEVER rolled the tire onto the indicator in the rear. As for toe...if you plan to drive it on the street, I suggest keeping a slight amount of toe IN for the rear. ~1/16-1/8" total IN. If you primarily auto-cross, then you can probably get away with neutral, but it's going to probably be squirreley on the highway.

Fronts...sounds like you know what you can run on your car without interference for negative camber. Neutral toe or a slight amount of toe OUT (~1/16"-1/8" total) will help turn-in, but it makes the car want to wander on the highway...especially if there's a crown in the lane.

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Originally Posted by Reaper1

I have used the blue shims with the spin wheel in the center. They work well.

The rear of our cars don't really need a lot of negative camber because of the way the suspension works. I only run about -.5* or so back there and have NEVER rolled the tire onto the indicator in the rear. As for toe...if you plan to drive it on the street, I suggest keeping a slight amount of toe IN for the rear. ~1/16-1/8" total IN. If you primarily auto-cross, then you can probably get away with neutral, but it's going to probably be squirreley on the highway.

Fronts...sounds like you know what you can run on your car without interference for negative camber. Neutral toe or a slight amount of toe OUT (~1/16"-1/8" total) will help turn-in, but it makes the car want to wander on the highway...especially if there's a crown in the lane.

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Thanks for the input. Yes I had planned on setting some toe in for the back wheels, but after some calculations I should be shooting for a range between +0.1-+0.2 degrees toe each wheel, which would work out to about 1/16-1/8 total toe in. Neg camber in the back will be as stated before, -0.2 to -0.3 degrees. I don't need to go any more than that, this car is honestly my commuter and grocery getter with some weekend fun. Most it's miles are mild ones, so there's no reason to push more negative camber in the front wheels to keep the difference front-back in check.

For the front end, I'm running all polybushings so neutral toe is what I have it locked in for. That seems the best setup with poly all around.

Keep one thing in mind if you plan to install the rear shims by the chart and the readings from your last alignment.
Your front toe readings are based partly on the readings from the rear toe. So, after you shim the rear, I would suggest getting the front redone, unless you use a tape measure.

how do they base rear off front?

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Originally Posted by going4speed

how do they base rear off front?

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They dont, the front is partly impacted by the measurement of the rear.

does this have to do with the roll axis?

Not so much roll axis, as much as thrust angle from the rear toe. Think of it like this, if the left rear wheel is perfectly straight (based on toe) and the right rear has .25* toe out, that determines the thrust angle down the centerline of the vehicle, which would make the car pull or drift right. The alignment machine would direct you to adjust front toe accordingly so you have a level steering wheel and a car that tracks straight. So, if you adjust that right rear toe to zero, then the front will now be off somewhat.
Does this make sense?

No, it doesn't deal with roll axis. Lets say for example that the rear toe looks something like this: L: +.4 R: +.2 Since they aren't equal, the middle point is going to be pointing over to the Right side .1. That's the overall direction the axle will want to travel while going down the road, to the right just a tad without any shims being used.

If the front wheels are aligned to be square to the frame, the rear end will kick out to the right a little and the driver will feel this as a drift or pull to the left as they will need to turn the wheel right to compensate

Since we know which direction the rear end wants to go, the alignment machine will take that into consideration when it's giving the info to the technician so that the car goes straight. What you end up with is the front wheels being pointed just a touch to the right when the steering wheel is dead-on straight to compensate for the rear toe being off a bit.

Quote:

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Originally Posted by DaveSkrab

Keep one thing in mind if you plan to install the rear shims by the chart and the readings from your last alignment.
Your front toe readings are based partly on the readings from the rear toe. So, after you shim the rear, I would suggest getting the front redone, unless you use a tape measure.

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Hey Dave,

Thanks for the tip. I had planned on getting one more alignment for the front after I install the rear shims. For one, I'd like to get a reading after the shim job to make sure the rear end is within spec, or close enough to please me. Then I'll have them dial in the front end based off of the readings on my rear wheels.

Since this thread has gathered a fair amount of attention, I do have one suspension-related quirk that I'd like to ask you guys about.

I've recently replaced Struts and Shocks, all bushings with Poly, strut mounts etc. The only original suspension left are the springs.

Since replacing shocks&struts, the driver side of my car hangs down noticeably more than the passenger side (Almost an inch different between top of tire and fender flair between the two sides). I figure this has to do with the transaxle weighting and that the driver side gets more wear, well...because of the driver sitting on that side. (Before doing the suspension work the whole car looked lowered, it was sagging)

Would this dip on the driver side be likely to be caused by stock, tired springs? It's not anything I'm overly worried about, and I have yet to bottom out the suspension so I think I still have enough travel and control. Would be nice to level the Ol'Lancer out though.

Regards,
Zach

It can be tired springs, but it can also be related to the angle of the control arm when the fasteners securing it to the k frame were tightened. Should be tightened with the vehicle sitting at ride height. If you have it jacked up and tighten, then you will preload that bushing, and potentially wear it more quickly.

Quote:

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Originally Posted by DaveSkrab

It can be tired springs, but it can also be related to the angle of the control arm when the fasteners securing it to the k frame were tightened. Should be tightened with the vehicle sitting at ride height. If you have it jacked up and tighten, then you will preload that bushing, and potentially wear it more quickly.

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Awesome know-how! I didn't even think that tightening the control arm while the car was raised would cause this issue. I guess I just chalked it up to "it's a moving part, it'll sort itself out".

That may very well be the reason, I'll have to loosen those bolts a bit and let the car settle, then torque them down again and see if there's improvement.