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Rear Alignment with Shim

Discussion in 'Gen II Prius Care, Maintenance and Troubleshooting' started by TFT, Jul 19, 2010.

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  1. TFT

    TFT Junior Member

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    I wanted to share my experience aligning the rear of my 2004 Prius with 104,000 miles. Just bought the car and it needed tires. I decided on the Ecopia EP100's and I also paid for a lifetime alignment at the local tire store. These were the before and after of the initial alignment.

    Before
    [​IMG]

    After
    [​IMG]

    As you can see the left rear alignment was just out of spec. The car would wander at freeway speeds, it just didn't feel right. It seemed as if the car required continuous steering inputs to stay in the lane. I was suspicious of the rear alignment causing the problem and it was suggested to me by other forum members to correct it.

    The following are the steps I took to correct the camber and the toe of the left rear of my car with an adjustable shim.

    I bought the shim at the local NAPA auto for $13.99. It came with instructions but not for the Prius. I hunted the net for the correct Prius instructions and found this handy calculator. You enter the adjustment amounts for toe and camber and it calculates the settings for the adjustable shim. In my case -0.20deg toe and -0.20deg camber were just what I needed to match the right side and bring the left side into spec.

    25 was the outer ring number and 8 the inner ring number.
    [​IMG]

    After cutting out the template for the Prius hub bolts.
    [​IMG]

    Rear hub after removal from axle. Mating surfaces cleaned for proper seating of shim.
    [​IMG]

    Shim installed on hub.
    [​IMG]

    Hub reinstalled into axle with shim. Bolts torqued to Toyota spec plus 15% or 52ft-lbs per instructions.
    [​IMG]

    Put the drum back on and the wheel and off to the tire shop for alignment check.
    5 people like this.
  2. TFT

    TFT Junior Member

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    Here are the before and after of the second alignment. Same shop, same alignment machine. Probably different technician. I asked them to center the steering wheel is was off a couple of degrees to the left.

    Before
    [​IMG]

    After
    [​IMG]

    As you can see the shim did almost exactly as was expected. what I didn't expect was a different reading for the right rear toe. It seems now that I over adjusted the left rear toe by -0.07 deg based on the initial alignment measurement. The left rear camber equals the right side camber at least. I guess from the different measurements for right rear toe that the actual setting is somewhere in between the two measurements? Any thoughts?

    Also, I don't know what was up with the different front toe settings for the two alignments? Could the first alignment have been that far off? Are these differences the typical measurement error to be expected of current technology alignment machines?

    The car does ride better but I detect some wander still. I think it is the stiff cross wind we've had here the last few days. It's been about 10-15 knots east wind, and I travel a I-75 north and south on my commute. I will be replacing the rear suspension soon with the touring components. The Left rear shock is leaking and the car is about 1/2" lower on the left. Maybe that will finally improve the tracking at freeway speeds.
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Well, I can think of two reasons that the front wheel alignment measurements might be off:

    1) measurement error in the alignment equipment
    2) your front suspension parts have sufficient wear so that the front toe-in shows that much change from one measurement to the next

    Regardless, I suggest that you drive the car on the freeway at the maximum speed that you'll be likely to drive the car and see if you have any concerns about its handling and performance. If not, then don't worry.
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  4. derkraut

    derkraut Member

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    Very informational and interesting post; thanks for sharing!
  5. TFT

    TFT Junior Member

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    Thank you for the replies.

    Patrick, do you think it could be ball joints or maybe bearings causing the different readings? The car really does drive better after the realignment. I think maybe a careless effort by the first technician was at least part of the cause. I plan to put 100k on this car over the next three years so I'm not afraid to change out some parts. Next I will address the leaky rear shock and then the front struts and springs. Maybe a tie rod or ball joints?
  6. xs650

    xs650 Senior Member

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    Thank for the write-up and pictures, you make it a lot clearer than the generic online instruction.

    What are the shims made of?
  7. dogfriend

    dogfriend Human - Animal Hybrid

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    I think that 1) is the majority of the discrepancy - I had the alignment checked several times before installing the rear shim and there was a couple of tenths of a degree difference in readings even on the same alignment rack. I think that amount depends upon the equipment and upon the skill of the alignment tech.
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes, it is possible that those parts may be worn, but you might want to have a professional mechanic inspect your suspension for wear before you start to replace parts.

    When you replace the front struts the camber (at minimum) will be affected so you should have the front wheel alignment checked (for a third time) after that job is done.
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  9. xs650

    xs650 Senior Member

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    Definitely replace a leaky shock, the other side also to keep that end of the car equally damped.

    Springs often last forever. Unless your car is sagging more than you find acceptable or you just want different spring rates or height, don't waste money on springs.

    Patrick's suggestion of having a mechanic check suspension components for wear is a good one, the trick is finding one you can trust.

    Your front toe changing (if it isn't a measurement issue) suggests tie rod ends because the other front end measurements didn't change much.

    I had a 1983 Camry and a 1991 Accord that didn't need any suspension work in 200k miles and I'm pretty fussy about suspension, I've replaced shocks on a new vehicles.

    Thanks again for the shim info.
  10. TFT

    TFT Junior Member

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    Some type of plastic. It felt gritty when I cut it with a utility knife.



    I have good independent mechanic that will inspect the car for me this week. I believe I have a CV joint going out as well. I think the previous owner had a run-in with some road debris. Whatever was hit may have accelerated the ware to some of the suspension parts. The front bumper cover has some scars.

    [​IMG]
  11. xs650

    xs650 Senior Member

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    FWIW, your shim manufacturer SPC Alignment - Specialty Products Co. calls out the same p/n for 2010 so you have helped those of us with Gen IIIs too.:thumb:
  12. gsesupport1

    gsesupport1 FLLRUP

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    I had to do this exact same thing to my 2005. The company that makes the shims is Specialty Products Company( Specialty Products Corporate Home Page ) the part number is 75800. They have a really nice video and a calculator to figure out exactly what sections to cut out and what numbers need to be aligned.
  13. xs650

    xs650 Senior Member

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    They also list a front camber adjustment bolt for the Gen II Prius. Looks like it gives the full range of adjustment (+/- 1.75 deg) that it takes several Toyota alignment bolts to achieve.
  14. sorka

    sorka Active Member

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    http://www.spcalignment.net/instructions/75800-INS_WEB.pdf

    Dumb question, the OP says 52 ft lbs of torque, but using the ez shim document above, 52 is for a configuration not for the Prius. For the prius, configuration 3B is to be used which specifies 44 ft lbs.

    Does anyone know what the actual toyota spec is? It should be that + 15%.
  15. dogfriend

    dogfriend Human - Animal Hybrid

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    Service Manual says 45 ft lbs (61 Nm) for the bolts holding the hub and backing plate to the axle beam.

    [​IMG]

    Attached Files:

  16. sorka

    sorka Active Member

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    Thanks. So that really is 52 ft lbs. The PDF I posted above must be wrong.
  17. sorka

    sorka Active Member

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    Well this sucks. The shim doesn't fit. I'm using the 75800 red ez shim but it's too small for the diameter of the hub. The hub has a 75 mm diameter but the shim's inner diameter is 72mm so it won't fit over the hub. Did they change the shim specs or is my 2009 prius somehow different? I could trim the inside of the shim a little to make it the correct diameter, but I'm not really sure the shim was intended to be used that way. Is the touring hub different than the the non touring hub? Perhaps that's the difference? Obviously I'll need to call the company that makes tomorrow :(
  18. sorka

    sorka Active Member

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    The template shows the inner diameter at two different sizes. The one it comes with matches the smaller size. It's clear from the template that it's meant to be trimmed even though the instructions don't say so. The OP's photo clearly shows his has been trimmed, so I used a dremel and it took about 5 minutes and now it fits fine.
  19. dogfriend

    dogfriend Human - Animal Hybrid

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    You should shim between the backing plate and the axle beam according to Galaxee (and her DH). I didn't think the diameter was that critical when shimming between the backing plate and beam. I didn't use the SPC shim because it wasn't available yet; I used a custom made aluminum shim.
  20. sorka

    sorka Active Member

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    That's correct. Here's what it looks like:

    [​IMG]

    So even though it's not in the instructions, it is on the template and says to trim the inside for the larger diameter axle.

    [​IMG]


    BTW, it's critical to re torque the bolts as the compressibility of the shim will mean the first bolt torqued will no longer be at the correct torque. i.e after torquing all 4 bolts in a cross pattern, the first bolt that was torqued to 52 ft-lbs was only at 43 ft-lbs after the 4th bolt was torqued to 52. It was necessary to re torque several times to get them all even.

    [​IMG]
    2 people like this.