If your tire is wearing on the inside tread (the tread on the side that is on the side under the car versus the tread that is on the outside side of the car), you might have a control arm bushing wearing out, according to Daizen. (This is what is happening on my passenger side front tire right now. Tire shop and alignment shop did not catch this issue.)

Here is the Daizen article explaining the issue.

http://www.daizensporttuning.com/model/lexus-sc.html

Most shops immediately give a knee-jerk diagnosis of needing a camber correction kit, but this is oftentimes not necessary, especially if you have approximately negative 1.5 degrees of camber or less, and especially if your vehicle is not lowered more than 1.5-inches. (Please see our technical section for a more in-depth explanation of negative camber vs. toe settings and how they affect tire wear on Lexus vehicles). As mentioned in that article, the most likely cause of this tire wear is a bushing issue, specifically the bushing on the #2 front lower control arms. Over time, the rubber in these bushings goes soft, and causes havoc with the toe settings of the vehicle. Pretty soon the car is wandering and darting all over the road, especially at highway speeds, and you are getting only 6-8,000 miles on a pair of front tires. Simply said - whatever the actual problem may be, make sure you are addressing the correct problem in the correct way.

 

Good looking out...

 

Good info. When I added wheel spacers I immediately noticed that I had steering issues. Balance and alignments won't fix it. I ordered the Daizen busing kit but haven't installed it yet. My plan is to install only the lower control arm #2 bushing (as long as I don't see any other problems when I'm in surgery.) I expect that it will be sufficient to stabilize the toe-in issues (or lack thereof) that have been aggravated by the wheel spacers.

I don't see any cracks in the OEM rubber when I inspect them on the car. I really believe that they are simply too soft - especially with the added forces created with wheel spacers.

As I've become sensitized to the problem I can feel the wheels go from their toe-in alignment to neutral (wheel shake) to a slight toe-out relationship as I progress somewhere through 55-70 mph. The slight toe-out position creates a small amount of instability in the driving direction of the car. Excessive toe-out will cause unstable "darting" which will keep you busy staying properly in your lane.

Ideally the initial toe-in combined with the road forces will result in lessened but still a very slight toe-in at most speeds. Anything else will eat tires and worse.

 

My mechanic shows no interest in installing the Daizen control arm bushings kit for me.
He keeps telling me to get the new control arms.
I will find someone else who is willing to install those bushings for me.

 

So I assume this is also a problem with stock wheels, tires, and suspension?

The previous owner of my vehicle bought really crappy and cheap tires for the front, and they are wearing unevenly on the inside of the front tires. I am going to get the fronts de-mounted and rotated to the opposite front and re-aligned. Hopefully that will fix the problem until the tires are worn out and I can get some good tires that won't wear unevenly.

 

Whether it's wider tires, offset wheels, wheel spacers or just tired caster bushings the front end geometry won't be stable enough to handle the additional road forces because the oem caster bushings are just too soft to work with the altered equipment.
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I finally found a mechanic to change out the caster arm bushings.
The labor cost is $350, so I hope you have the tools for a DIY job.
My old bushings are still in good shape according to that mechanic.
And he also suggested I should changed out the upper control arm bushings at the same time for extra $200.

Car feels a bit more firmer and stable at higer speed, but no where near stiff.
Perhaps I should have changed the upper arm bushings as well.

 

Any idea how difficult those caster arm bushings for the lower control arm are to get to? I am assume it is in an annoying place, considering the $350 labor fee.

 

I was there the whole time while the mechanic was changing them.
It took him around 2.5 hours.
$350 is a little too expensive, but I couldn't find another shop that was willing to do it.


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