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Context/Information: If I understand correctly, having a fixed axle in a car makes getting things aligned significantly harder. This seems to be the case in my 2009 Toyota Corolla and the rear axle. When my wife took it to Costco to get new tires, they told her the old front tires had some cupping and the rear set had feathering (don't have more details than that). She took it to get aligned, in order to prevent further unnecessary wear, and was told that the front was already within factory specs, and the rear was not adjustable (though the minor improvements to the front specs threw the rear left toe OUT OF factory specs and the left further out of spec for both toe and camber). The factory tires replaced had about 41,000 miles on them. The specs for the rear camber and toe are apparently -2.0 to -1.0 degrees and 0.01 to 0.26 degrees, respectively.

-- BEGIN EDIT --

Front Measurements

                         Before          |             After
                     Left  |    Right    |      Left     |    Right
Camber              -0.60  |    -0.80    |     -0.60     |    -0.80 
Caster               3.10  |     2.80    |      3.10     |     2.80 
Toe                  0.09  |    -0.02    |      0.00     |     0.01
SAI                 12.60  |    12.60    |     12.60     |    12.60
Included Angle      12.00  |    11.80    |     12.00     |    11.80
-------------------------------------------------------------------
                                         |           
Cross Camber              0.20           |           0.20
Cross Caster              0.30           |           0.30
Cross SAI                 0.00           |           0.00
Total Toe                 0.07           |           0.01

___________________________________________________________________
Rear Measurements

                         Before          |             After
                     Left  |    Right    |      Left     |    Right
Camber              -1.20  |    -2.00*   |     -1.10     |    -2.10*
Toe                  0.21  |     0.01*   |      0.28*    |    -0.02*
-------------------------------------------------------------------
                                         |           
Cross Camber              0.80*          |           0.90*
Total Toe                 0.21           |           0.26
Thrust Angle              0.10           |           0.15


___________________________________________________________________
All measurements are in degrees
* indicates not within manufacturer specifications

Finally, the shop stated The manufacturer does not specify rear CAMBER and TOE adjustments, leading me to believe the rear axle is solid.

-- END EDIT --

Question(s): How bad is a right toe reading of 0.28 degrees (0.02 above the spec range), a left toe reading of -0.02 degrees (0.03 below), and a left camber reading of -2.1 degrees (0.1 below)? my instinct is that this may reduce the life of the tires only very subtly, and would be mitigated fairly well by rotating tires. Is there a general rule to go by for alignment's affect on wear? How long SHOULD my tires have lasted?

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What sort of alignment place did you take the car to? Unfortunately alignment shops aren't created equal... –  Timo Geusch Sep 19 '11 at 22:09
    
@Timo A tire shop (don't wanna give them any recognition) - not an alignment specialist. Do you really need to know the particular place? I understand there are shims that can often help to adjust the camber, but I'm not sure about toe. –  Code Jockey Sep 20 '11 at 16:13

1 Answer 1

up vote 2 down vote accepted

You basically have 3 measurements in the front, and 2 in the back that are normally adjustable unless you have a solid axle (You don't). The front caster is adjusted at the strut mount, the front/rear camber and toe normally utilize rods to adjust. The toe utilizes the tie rods in the front that are attached to your steering box, and the rear usually uses a rear tie rod that is set in place. The camber is adjusted using a mounting arm in most cases, and all 5 of these should be available in your vehicle. There are of course other measurements that are looked at to determine whether your vehicle will drive straight or not, but these are the commonly adjustable ones. The numbers you mention seem small, and if the vehicle is not pulling, you should be ok. The most important thing to extend tire life is the pressure, if you let your pressures drop, you will wear the tire out. If they tried to align the vehicle, and it failed, you might need suspension parts at this point (pot holes are rod/arm killers). Most dealerships keep a competitive rate on alignments, so do not be afraid to call and get an alignment quote.

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Thanks for your assessment of the numbers! I try to keep tires as perfect as I can (much easier to check than alignment). you say I don't have a solid axle - is it simply not adjustable, or does the manufacturer not specify adjustments, or am I completely wrong? I was told in writing that "The manufacturer does not specify rear CAMBER and TOE adjustments." What does this mean? not fixed, but no camber or toe adjustments? I'll put all the numbers in my question for further reference. –  Code Jockey Sep 26 '11 at 16:42
    
Your assessment above is correct. You are right at the limits for the most part, and the vehicle drives straight. –  FossilizedCarlos Sep 26 '11 at 23:42

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