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OK, here is the latest,
Just got back from a visit to my local Saab dealership. Worked with their Saab "master mechanic" Gary who has 30+ years working on Saabs and owns 9 himself! I told him my dilema with the "cupping" tire wear and that I needed a precision 4 wheel alignment and the suspension checked out. I also brought my car in with my regular trunk load of stuff which I weighed at approx 200lbs. before leaving home. He was aware of the uneven wear issues with our cars.
After doing the initial readings on their Hunter system, he verified the negative camber settings of 1.9 degrees on the rears which is actually in spec. for the sport suspension. He also noted that the toe adjustments were off and the front end needed a bit of tweeking too. During the adjustments he set the wheels up on the "positive" side of each adjustment range. He said the shocks and springs were in fine shape. I asked him about the lack of adjustment for the rear camber and his answers seemed logical. He could do the shims but it involves quite a bit of work and you have to guess about the amount of shims and then do another alignment check and redo it until you get where you want it to be. Another option is to get an aftermarket "camber kit" which needs to be custom installed with some welding involved, or make slots in some bolt holes to allow for camber adjustments. All of these options involve a sizeable investment of labor and/or parts to which the ROI(return on investment) may not be realized for a long time vs. just some better tire management. I also think that he is such a purist that he doesn't really want to go outside Saabs' hadling specs for the Aero. Also, the rear toe adjustment does require a special tool, however, it can be adjusted without it using a prybar at the right place, so if you take it to an indy, don't let them tell you otherwise.
Here is our current stategy with my new tires, which by the way are the newer Kuhmo Ecsta ASX 225/45WR17's. He likes the fact that they are asymettrical and can be cross-rotated along with the inside tread blocks not being too agressive in design. The high UTOG treadwear rating of 420 is a better bet also. He is recommending that I rotate these initially after 2500k and take a close look at the wear. He also recommends that I boost the psi to 42lbs. up from the present 36lbs. which will put more of the middle portion of the tires footprint on the road surface....he said "don't be afraid"! Then the plan is to do the modified cross-rotation pattern at every 5k when I do the oil change. This should even out the inside wear and prolong the treadlife. Tire balnace should be dealt with immediately if there is any noticable vibration since this can also cause some cupping of tires. Common sense also dictaes the the psi should be checked weekly.
For those of you that have "directional" tires, the stategy is a bit more involved and more expensive. Since those type of tires cannot be cross-rotated, they should be remounted on the same rim in the opposite direction and then swithed to the opposite side of the car. This may actualy be better since it puts the previously cupped inside edge to the outside of the tire. This may only need to be done when you start to see any real wear insead of during every rotation.....a judgement call.
From now on I think I will have Saab do the alignmnets. I will be keeping track of my tire care much better on my latest set and with this strategy I will hopefully get what I need out of a set of tires-40K+. Since I log about 3K per month, I will be able to give you all feedback within the coming months.......stay tuned!!!
posted by 66.32.8...
, Tue, 6 Sep 2005 14:20:31
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