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Shim for rear wheel alignment- advice please

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by wigwag, Feb 16, 2011.

  1. wigwag

    wigwag Junior Member

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    I found funny wear on one rear tire at 5K which led stealership to install a "EZ Shim" made by Specialty Products. The service manual simply says to replace parts as necessary if rear alignment is not to spec but I am told that this shim deal is sanctioned by Toyota. These shims have been around for years and work well on drum brake cars because the shim goes behind the brake backing plate so the brake assembly remains aligned with the hub/brake drum. The problem with disc brakes is that the caliper mounting bracket bolts to the axle so moving the hub/rotor leads to misalignment between caliper and rotor. The "fix" for this is to use shim washers between the caliper mounting bracket and the axle to (allegedly) correct the misalignment. Here is what worries me; the alignment shim is tapered so the rotor is being misaligned to the caliper in 3 dimensions (planes) and the caliper bracket shimming procedure is only capable of correcting misalignment in one dimension- there is simply no way to fully or properly align the rotor to the caliper. Should I accept this fix or go to war and demand that the axle be replaced?
     
  2. xs650

    xs650 Senior Member

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    Some things to consider.

    The more the dealers mechanics work on your car, the bigger the chance they will screw something up, maybe something that isn't obvious.

    If they shimmed it correctly, the wheel alignment results should be more accurate than swapping factory parts.

    Unless the adjustment was gross, the pads will soon wear in and compensate for any caliper misalignment.

    Lacking some actual alignment numbers, including how accurately the stock caliper mount is aligned to the axle, the best you can get here is speculation.

    If it were my car I wouldn't hesitate to use a minor amount of shim.
     
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  3. alaskanbushpilot

    alaskanbushpilot New Member

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    Wow. This post is really nasty and uncalled for. Keep your opinions of Toyota dealers to yourself and just state your opinion, please. You don't mention your qualifications or training on Prius vehicles...is it more than you working on your Prius in your backyard?

    Perhaps the best advice I can offer here is ALWAYS qualify your source of information. It might be somebody who really doesn't know what he's talking about. Bad mouthing mechanics who DO have PRODUCT knowledge is a very solid clue about the author. I logged onto this site to see what the deal with the shims is because my company is developing them for this vehicle. What I saw was deeply troubling and nasty. You win Mr. Senior Advisor. You are the mavin on these cars-or so YOU think. No thanks to you.


     
  4. tumbleweed

    tumbleweed Senior Member

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    My recent experience with the service departments at two Toyota dealers plus what I see on this site indicates that xs650 is correct. Anytime you take your car in you are at risk. It is unfortunate but true that many dealerships have mechanics and technicians that are simply untrained and unqualified. I do most of my own work, not because I enjoy it but because I am reluctant to take a chance on having it screwed up again.

    There are a few good mechanics and technicians and some of them post on this site. But you can't be sure of getting someone who knows the Prius and will do a good job when you take your car in. Check some of the other threads in this forum, there are some true horror stories of cars screwed up by mechanics at dealerships.

    The problem of poor to non-existent training and sloppy workmanship isn't exclusive to Toyota. I have owned enough other marques and spent enough time on other forums to convince me that the problem is fairly widespread among auto dealers. I think most dealerships do not provide sufficient training and a lot of mechanics are to rushed to take the time to do a good job.
     
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  5. tumbleweed

    tumbleweed Senior Member

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    I had the rear axle replaced under warranty on my gen2 Prius, drums on the rear so no brake problems. The original axle had been damaged in shipment. Unfortunately the new axle did not have enough toe in and the car wandered all over the road at highway speeds. The dealer would not replace the new axle and said that Toyota would not approve the use of shims.

    Fortunately I was rescued by one of the Prius Technicians who posted on this site at the time. He sent me a pattern for the shims. I cut some out of copper sheets and after a couple of tries using different thicknesses and a couple of trips to the tire store to have the alignment checked I had it fixed. I was able to put the toe in right in the middle of it's range on each side without screwing up the camber.

    My gen2 drove great after that and I am confident that it's new owner got a good drivable car.

    So I guess if I had a similar problem with my gen3 I would use shims and keep an eye on the brake pads and rotors. I agree with xs650 that they will probably be fine and if not you can have the axle replaced later.
     
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  6. ursle

    ursle Gas miser

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  7. wigwag

    wigwag Junior Member

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    Thank you all for the advice and opinions on my "shimming" question. Update; sometime after the alignment shim was installed I jacked the car up to check for roadkill remains (don't ask) and found that the shimmed wheel was way harder to turn than it's mate across the car so I pulled the wheel and found that the brake was dragging. It was obvious just by eyeball that the caliper and rotor were heading in different directions and I found that the caliper had been shimmed with a common flat washer under each of it's mounting pads. Crap. I pulled the other wheel and measured the distance between the caliper and rotor and duplicated that measurement on the shimmed side (using "real" shims) which reduced the drag to "just slightly more" than the unmolested side. I'm still stuck with the concern from my original post- there is no way to properly realign the caliper to the rotor after installing one of these alignment shims. Anecdotal evidence suggests that there are a fair number of gen3 cars with rear alignment problems and based on the way my problem was handled I'm afraid that this "solution" has never been properly vetted by Toyota's engineers.
     
  8. jdenenberg

    jdenenberg EE Professor

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    You might want to go back under your Prius and lubricate the slide pins so that it is easier for the caliper to center itself.

    The pads should wear to align themselves with the rotors as long as the misalignment is not too bad.

    JeffD
     
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  9. xs650

    xs650 Senior Member

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    Now you have done it! Bushpilot is going to be all over your case for daring to suggest that a Toyota mechanic was less than perfect.:D

    EX Shim makes special shim washers to space the caliper out. P/N 75970. They cost more than the wheel shim for some reason, so a good substitute makes sense.

    JeffD is right, as long as the misalignment is small, the pad will wear in to match the disk.

    If you have a stack of shims in there, you should lay a torque wrench on the bolts after a few hundred miles and see it the bolt moves any further. If it turns a bit, recheck every few hundred until it stops moving.
     
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  10. Toppcat

    Toppcat Member

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    A insider old school mechanic secret! But should be perform be someonen known what he doing is by grinding method taking down the metal on the axle once again I can't stress you have to be well season to perform this method.
     
  11. creature0077

    creature0077 Junior Member

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    How did this work out for you? Did you have to sand down part of the shims to give it a wedge look or did you just make it a different way? Can you sent me the pattern too? Need to adjust my camber.
     
  12. Dion Kraft

    Dion Kraft Member

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    Those shims were really meant to be used on rear drum brake styles. Drums don't care as they are not affected by shims. Calipers are another story as any shim changes the relationship spacing from the caliper spider which the caliper rides on to the rotor which the hub rides on.
    Slight amounts is one thing but generally speaking its a kinda a lame setup. Better to bend the spindle into alignment.