X25

On Z06, MagnaRide only comes with cup wheels in 19"/20" sizes, even if you don't get the carbon ceramic brakes. This makes me think GM has tuned PTM for the tire setup found on Z07 / ZR1, so MagnaRide always comes with these wheel sizes.

Now, this makes me wonder: what happens if you drive the car with PTM enabled on tires with different diameters than stock? Would it impair the functionality of PTM? I have a set of 18"/19" Z06 wheels shod with MPSC tires besides my car's stock 19"/20" wheels, and would like to use them for track days, but I need to know if this would mess with the PTM's functionality.

Diameters:
(1) 18/19 stock setup:
--> 275/35/18 --> 25.6"
--> 325/30/19 --> 26.7"

(2) 19/20 stock setup:
--> 285/30/19 --> 25.8"
--> 335/25/20 --> 26.6"

(3) 18/19 stock wheels, aftermarket MPSC tires:
--> 295/30/18 --> 25.2"
--> 345/30/19 --> 27.2"


Thoughts?

Werks

PTM will work with other than stock tires, you just have to keep the split correct. Off the top of my head I believe it is 1 1/2 inches max or something along those lines or it throws off the traction control. The bigger issue for you though is going to be what I and another Z06 Carbon Edition owner recently figured out which is that the stock mag suspension is simply too soft for serious tracking if you are a fast driver. So ultimately if your intention is to really push the car and you are going to be running R compound's or possibly slicks down the road just know that you are going to be fighting a loosing battle trying to get the stock mag suspension to work for you.

X25

Himm, so do you have Carbon edition? If I understand it correctly, Carbon edition does not have PTM, right? This softness issue is interesting. Considering 2012+ Z07 option already comes with Michelin Pilot sport Cup tires, you would think they would tune for it? Now I wonder if they made any changes from 2012 to 2012, since 2011s only came with PS2s. Bummer.

jvp

PTM is more tuned for tire grip than it is tire size. The rest of the Stabilitrak system will potentially have problems if you don't have a proper ratio of rear to front tire overall diameter. But the PTM won't care.

When GM released the Sport Cup tires on the ZR1, PTM was retuned a little to deal more aggressively with the stickier tires. It doesn't mean that a non-Sport-Cup tune won't work with R compound tires though. It'll work just fine. What it does mean is that if you take a newer car and slap PS2s on them, and then start pushing it with PTM, you might get questionable results.

Basically: you can go stickier than your PTM is tuned for, but you generally don't want to go less sticky.

FWIW: I use PTM on my ZR1 at the race track all the time, with smaller-than-stock Rs, and have no issue. And I disagree with Werks' statement regarding the suspension being too soft. It is, in fact, perfect!

jas

X25

I have not taken delivery of my new '13 Z06 yet, so I don't have any personal experience on the Magna Ride suspension. I sure hope you're right that it is perfect, though

In my previous car ('12 GS), even though I was told the diameter difference with the set-up above can normally cause "Engine drag" warning, the tolerances are higher when used in Competition mode, which is the mode I've used these tires with, and at that mode, it never was an issue. In fact, I used this set-up even forgetting to switch to competitive mode, it still did not cause any issue whatsoever.

This new car won't have Competitive mode (replaced by PTM) as far as I understand, so we'll see how it behaves.