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The Service Writer was misinformed on several things. First, the tires themselves; Second, the cars do not come from the factory with a track alignment, (just take a look at your alignment settings and compare them to what the track alignment numbers are right in your Owner's Manual; Third, the PSS ZPs don't typically wear out in 8K miles.
From what I am seeing your camber at all 4 wheels and front caster look good but the toe is off starting with the toe out on the left rear and the toe in on the right rear with a green but not so good thrust angle. The thrust angle you have indicates the rear wheels are pointed to the left with the rear of the car trying to track to the left as it moves in a straight line.
In front the toe angles are set to compensate for the poorly adjusted rear toe by making sure the steering wheel is centered while the front tires are also pointing to the left. The result is when the car is traveling in a straight line the car is actually traveling slightly sideways with the rear of the car slightly to the left of the front of the car (Dogwalking). The left rear toe out also means the tire is pushing the inner side forward of the outer side. With negative camber that puts a lot of pressure on the inside edge of the tire.
Getting the rear toe set so it is at 0 degrees on each side or even better at 0.01 degrees (toe in) on each side will reduce inner tire wear. You could have the camber reduced by about 0.4 degrees all around but that won't help as much as getting some toe in at both the front and rear with the thrust and steer ahead angles closer to 0.
Remember reducing the negative camber means the car won't have that nice snap to it when you turn the steering wheel. Handling response will be numbed downwards toward Impala handling characteristics.
Did they discuss rear caster with you? C7s are the only car on the market that have rear caster settings. The dealers do have the ability to borrow the necessary tools from GM if they don't already own them. The alignment machine has no capability to measure rear caster or to print out any readings the mechanic sees on the special gauge. GM specs rear caster to be 0.0 degrees with a tolerance of + or - 0.08 degrees at each rear wheel. GM doesn't specify a rear cross caster. Reports from track experts indicate the best settings are at + 0.07 degrees on both sides for a 0 cross caster and this works well on the street as well as the track.
Bill
Wow! Love your response. Thank you Bill! I knew about the rear caster being a separate manual measurement, but I was so annoyed that I forgot to ask them to do it.
I know I'm going to get flamed for putting a cheap tire on my z06... I decided to go with the Federal 595 RPM in the following sizes:
F - 285/35/19
R - 335/30/20
I know they have a larger diameter than stock, but I'm increasing the ratio in the front and rear. I just couldn't resist trying them as a daily driven street tire, since my total cost for 4 tires shipped was $543.14. There were a couple of old threads about these tires so the info was very limited and I wanted to give them a try for myself and report the findings. Once I get them mounted, which should be by the end of the week, I will post pictures and initial experience with the tire.
I understand the MPSS is a runflat tire designed for the c7, but I was never impressed with them on my base c7 and even less with the z06.
Minus the rubbing in the rear on my base c7 (due to custom wheel offsets) with Nitto NT-05 305/30/20(r) and 275/35/19(f) they were my favorite tire, but didn't last long. The last set I put on the base c7 was the Conti Extreme Contact Sport in 295/30/20(r) and 265/35/19(f). I like the Conti ECS, but the pics I've seen of them on the z06 in oem sizes look like rubber bands.
I did contact GM customer service. He told me he was going by what the dealer said and they wouldn't do anything except a free alignment if I purchased tires through the dealer.
Get them to match the Tire rack price of the tires and throw in mounting and alignment. Dont go overboard w the rear camber, I use the DSC street alignment w tires wearing evenly
I know I'm going to get flamed for putting a cheap tire on my z06... I decided to go with the Federal 595 RPM in the following sizes:
F - 285/35/19
R - 335/30/20
I know they have a larger diameter than stock, but I'm increasing the ratio in the front and rear. I just couldn't resist trying them as a daily driven street tire, since my total cost for 4 tires shipped was $543.14. There were a couple of old threads about these tires so the info was very limited and I wanted to give them a try for myself and report the findings. Once I get them mounted, which should be by the end of the week, I will post pictures and initial experience with the tire.
I understand the MPSS is a runflat tire designed for the c7, but I was never impressed with them on my base c7 and even less with the z06.
Minus the rubbing in the rear on my base c7 (due to custom wheel offsets) with Nitto NT-05 305/30/20(r) and 275/35/19(f) they were my favorite tire, but didn't last long. The last set I put on the base c7 was the Conti Extreme Contact Sport in 295/30/20(r) and 265/35/19(f). I like the Conti ECS, but the pics I've seen of them on the z06 in oem sizes look like rubber bands.
some pics of the mounted federals. Rears rub the inner wheel well cover in the back where is sticks out a bit. I'm lowered all the way on stock bolts and the rear has 1 ring cut off. I also have 6mm spacers all around.
I had my 2016 Z06 aligned when I took delivery in April 2016. The dealer had told me GM would cover the cost; turns out they would not until it got to 500 miles to allow the suspension to "settle in". Still they split the cost with me. The specs (below) that I had them use were the Performance Street specs from Pfadt Race Engineering and they differ a bit from the specs posted by others. Also posted below are stock GM specs for a 2015; you may ignore my handwritten notes). Don't know if they have changed since. I have 16,000 miles on my Super Sports and they show even wear across the tires plus or minus 1/32". My depths measured on the outside, middle and inside are generally about 5/32 to 6/32s, with only one 4/32 reading. I will probably need new tires later this year but the wear has been pretty even, which is what I had been shooting for. --Bob
I just got 14,500 street mi on a set of mpss while running only the Dsc track/street settings. I do have the dealer align it Three or four times a year as I tend to jack it up on track.
I bought the the bracket and a gauge for the rear caster but mostly it is the toe that gets out of whack.
With a a less aggressive alignment there would have been more miles on that set of tires.
I had to raise the rear about 1/4 inch and they don’t seem to rub anymore. So far, I really like these tires. For straight line traction they grip better than the MPSS.
I had to raise the rear about 1/4 inch and they don’t seem to rub anymore. So far, I really like these tires. For straight line traction they grip better than the MPSS.
That's due to the extra tirewall height and being brand new tires. But mpss are grippier on same exact tire size and ambient temp. Guaranteed.
Last edited by BrunoTheMellow; 05-06-2019 at 02:59 PM.
04-29-2019, 05:43 PM
