19" and 21" Tire Wear (informal) Survey

[zwede]

Nice - so 2 mm should be a good target to aim for in the rear - 0.21* which would put it right in spec and 1 mm would be great for the front.

Well, no... 2 mm in the rear, 0.21 degrees is out of spec. The way you're measuring it, you're seeing both sides, or total toe. Spec for total toe is 0.30-0.50 so you should aim for 3-4 mm. When measuring using the string method you see only one side and then 2 mm is good.

As for the front, I recommend going 1 mm total toe-out. Yes, a little toe-out on the front. You'll notice a nice improvement in turn-in and I have not seen any negative effects. I'm getting my best efficiency results with this setting.

 

[Dave EV]

Well, no... 2 mm in the rear, 0.21 degrees is out of spec. The way you're measuring it, you're seeing both sides, or total toe. Spec for total toe is 0.30-0.50 so you should aim for 3-4 mm. When measuring using the string method you see only one side and then 2 mm is good.

The alignment sheets that redi posted earlier indicate otherwise?

 

[lolachampcar]

I'm running .2 degrees of TOTAL toe in on the rear which has great milage and slightly less straight line stability (slightly more tendency to hunt).

The front should have a little toe OUT.

As for the math, total toe in the rear per .1 degree is found using-
Tan .1 X tape distance apart = measured difference
.001745 X 21.5 = .0375"
I would think it hard to read a tape repeatably in 1/32" increments.

 

[zwede]

The alignment sheets that redi posted earlier indicate otherwise?

Yes, I've noticed this also. My numbers are from the owner's manual, p. 128:

I don't know why the service centers have a different spec loaded on their alignment machines???

Either the manual is wrong and it is supposed to be single wheel toe for the front, total toe for the rear, or they programmed the machines wrong. We do know that they had the wrong spec in the machines last year, but it was supposed to have been fixed in the fall.

 

[redi]

So summarizing everyone's input correctly a target of .1 degree total toe OUT is a good target and within spec for the front, and .3 total toe IN (or slightly out of spec .2) in is within spec for the rear, and the lower side would be best mileage/wear at the expense of minor straight-line tracking stability?

 

[zwede]

Yes on the front. On the rear I have tried both 0.20 and 0.30 degrees toe-in and I've achieved my best efficiency numbers (measured over 30 miles) with 0.30.

I have tried various rear toe settings and didn't notice any difference in handling as long as I had toe-in. For the front I prefer the handling with slight toe-out (turn-in is much improved) and it has no efficiency decrease. Even with slight front toe-out I have not noticed any problems with high speed stability.

 

[zwede]

I've sent an email to ownership asking about the rear toe spec since what's in the owner's manual does not match what the SC has.

 

[redi]

Visited the SC today for an alignment check and they indeed showed toe-out in the rear equivalent to my toe plates showed earlier in the week.

It was heartening how closely the manual toe plates and the rack agreed on the before/after.

The SC re-aligned to the current specification, which again agreed with my measurements as precisely as the fine-ruled tape and toe plates allows (which is fairly precise as far as I can see). Now have a hair over .3 total toe in. The guys really worked hard to make it spot on. I'll be in for the annual in a couple thousand miles for another data point.

According to the guys in the SC there are recent updated alignment specs from the factory but I don't have the details on that. I'd like to stick the new spec in my manual if anyone has a printed one.

They originally said the sloppy bolts were coming out and the std bolts in but the camber had not moved and was about as flat as possible so they stayed in.

We're all still not able to come up with a good theory on how the toe-in on the printout at 5k changed to toe-out at 8.5k (by about 10mm). So I guess we all have to just keep an eye on the toe for a while.

 

[zwede]

No reply from ownership yet, but looks like the SC is now using 0.30-0.50 toe in as the spec (which is what the owner's manual lists).

 

[redi]

No reply from ownership yet, but looks like the SC is now using 0.30-0.50 toe in as the spec (which is what the owner's manual lists).

They indicated yesterday they had "new alignment specs" and it is unclear to me, upon reflection, whether that is a paper spec or corrected/adjusted data for the alignment rack.

 

[lolachampcar]

I really hope this all comes down to needing to properly torque the eccentric clamp bolts for the toe adjusters.

Mine have never moved.

 

[redi]

I really hope this all comes down to needing to properly torque the eccentric clamp bolts for the toe adjusters.

Mine have never moved.

The old SB (4/13/13 SB-13-34-003) showed the torque spec on the rear toe link bolt at 75 Nm, 55 ft*lbs.

Is this still correct or has this spec changed?

 

[lolachampcar]

no idea, but 55 ft-lbs on that nut should be more than enough to keep the eccentric from rotating.

 

[zwede]

Ownership forwarded my email asking for the current rear toe spec to my service center and here is their reply:

"The new spec was recently released and shows the rear total toe spec to be 0.35 degrees +/- 0.10. This would make individual toe about 0.17 degrees."

So the new spec is a slight reduction in rear toe:

Total rear toe (degrees)	Min	Max
Old	0.30	0.50
New	0.25	0.45

They didn't address my question regarding the SC printout showing a different spec back in Feb '14 (They used 0.10-0.30).

 

[Owner]

The print outs that they have given me in the past never showed total toe, only individual toe. My local mechanic questioned this...

Ownership forwarded my email asking for the current rear toe spec to my service center and here is their reply:

"The new spec was recently released and shows the rear total toe spec to be 0.35 degrees +/- 0.10. This would make individual toe about I degrees."

So the new spec is a slight reduction in rear toe:

Total rear toe (degrees)	Min	Max
Old	0.30	0.50
New	0.25	0.45

They didn't address my question regarding the SC printout showing a different spec back in Feb '14 (They used 0.10-0.30).

 

[rdrcrmatt]

Finally going to add to this thread.

I'm at 33,000 miles. Tirewear has been acceptable, but more so on the insides of the tires. The insides are at the wear bars and the outsides look good. I'll be throwing a set on before winter for the snow then new wheels and tires next spring.

 

[redi]

I really hope this all comes down to needing to properly torque the eccentric clamp bolts for the toe adjusters.

Mine have never moved.

My alignment was reset set at the SC almost 3 weeks ago. They found rear toe out of spec (i.e. toe out).

I'm mostly focused on rear toe-in at this stage, so I checked in my garage after the SC visit indeed the rear total toe-in looked to spec to me as close as I can eyeball with toe plates.

A week and 300+ miles later was driving across town and by the very meticulous local track/performance shop and had time for them to check it again: .26 toe-out in the rear again and somewhat out-of-spec toe-out (L 2x spec, R borderline). Reset to in spec. I've since checked rear total toe-in after 200+ miles more over the weekend and it is still equivalent and correct within the precision of my plates.

I should have checked it prior to driving my local track shop as another data point, but the rear toe-out finding was completely unexpected. Will be more diligent the next time.

I have more questions than answers but something is still not right somewhere.

With the staggered 21" PS2's at this stage, I will have to keep better eye on the rear toe-in until they wear out, which should be easy enough to do even in the best of scenarios with a normal wear pattern.

 

[lolachampcar]

I would absolutely have to know why toe moved on the car. Not meaning to state the obvious but toe should simply not move.

 

[jerry33]

I would absolutely have to know why toe moved on the car. Not meaning to state the obvious but toe should simply not move.

^^^^ This. The SC didn't always get the alignment correct for a variety of reasons, but it never moved between adjustments.

 

[redi]

^^^^ This. The SC didn't always get the alignment correct for a variety of reasons, but it never moved between adjustments.

I think they got it right the last time. But I have no idea what would cause it to drift in 300 miles other than bolt torque. The roads are just fine around here and I can think of no unusual stresses in 300 miles.