BaylorCorvette

Well like I said I have a Z51 not a Z06, further more it doesn't have mag ride (switching to coil overs next week). So the suspension set up will be vastly different.

But to answer your question here are the specs for the tires

NT01's
Front: 275/35/18, 25.55" overall diameter, 10.91" overall width
Rear: 305/35/19, 26.42" overall diameter, 12.32" overall width

Pirelli Slicks
Front: 265/645/18, 25.39" overall diameter
Rear: 305/690/19, 27.17" overall diameter

Koan

Well, my amateur analysis says it is tire specific rather than size specific. The Nitto has a pretty stiff side wall and the Pirelli doesn't, so I have no idea! The BFG R1s is more like the Nitto in construction. I haven't heard from anyone who has used BFG R1s on a C7, but I've heard no complaints about the Pirellis (other than the normal stuff one gets from those who buy take-offs).

Thanks for posting your experience. It is food for thought.

rikhek

My 18" forged track wheels are being delivered tomorrow. I'll be running Pirelli slicks in the following sizes. These are the closest size to OEM in Pirelli's.

305/645/18
325/660/18

Years ago I ran the BFG R1s on my C5 and C6Z and loved them. I was always surprised more people didn't run them. Seems like I was the only one on any given track day. I didn't think they made the R1 in an 18" that would work on the C7Z.

I just checked R1 sizing and it looks like the best sizing option they offer which should work isbelow. I see you posted the R1S sizing. Those are not an option for me as they're an autocross tire and I typically run 40 - 42 minute sessions (i.e., a full tank of fuel/session). I think the R1S would be toast by lunchtime. Similar to Hoosier R and A. The R works well on track but the A is their autocross tire which can't be run for full sessions with any longevity.

285/30/18
335/30/18

I only wish the 335 sidewall wasn't a 30 series. Might have to order a set....

EDIT: Well hell, BFG tells me the R1 in 335/30/18 is discontinued. They still make the R1S in that size but they would melt if you ran them for any length of time. Too bad, you got me all excited as I really liked those tires.

BrunoTheMellow

I had a huge spreadsheet doing similar comparisons and 1 thing was clear: the run-flat corvette spec MPSS had 3/4" to 1" wider tire tread than same-sized non-runflat MPSS and other brands. There are several specifications of MPSS for different brands. i am willing to bet the run-of-the-mill MPSS is not nearly as good as the Star spec (BMW) or MO spec (mercedes) MPSS. For example for tire size:

MPSS ZP 285/30r20 - 11.2" tread width.
MPS4S 285/30r20 - 9.8" tread width.
MPSS 285/30r20 - ~10.0" tread width (4 different specs average ~10 and range 0.7")

I am running Hankook RS3 at 285/35r20 - 10" tread width. Tires should be stickier than the MPSS ZPs but they are definitely softer and wobblier and I am consistently 1 second behind my track time on 15k miles and 4 track days MPSS ZPs. This is on brand new RS3s and even after 5k miles (same time really, within .10 seconds of when they were new). Now is this because the softer turn in? higher ride height? or narrower tread width? I am willing to bet the tread width is the biggest culprit. That's a 10% reduction in tire width on all 4 corners.

What I've also found is that there is a huge jump in tread width from the 285 to 295 on the MPSS non-runflat. From 10" to 11.5" average. But from 295 to 305 to 315 there is virtually no change in tread width. The actual tire width continues to grow but the tread width remains fairly constant at 11.5". Then another big jump at 325 to 13" and stays constant to 345. The overall tire width rises at an expected 0.4-0.5" (10 mm is 0.4") . This is all on tire rack's measurements which uses a curved ruler thing.

On the MPS4S. 265>285 only goes from 9.6"-10", 295 is at 11" and grows properly at 0.4" intervals through 305 and on to 325.

In short, get 295 or 305 non-runflats to replace the 285 if you want to match tread size. Be careful with total tire width as the sidewalls are less vertical and bulge much more. The section width to tread width ratio is an interesting measurement to look at when checking for fitment.

daleong

Great info! You wouldn't happen to still have that spreadsheet and can share? 😀

Pacembellum

Thanks for the analysis. I am planning on doing the 295/325 sport cup combo when i get around to it.

Roadrogue

I couldn't find tread width on Michelin website nor how to determine if the tire was for a vette or BMW etc. Foosh has been convincing me that as3 plus ZP would give me wood but want to verify width and spec.

patentcad

I presume the OP is talking about a Z06? Can't find that info anywhere, the assumption seems to be we know what specific kind of C7 he owns.

JerryU

Great post, thanks for sharing the info and results.

IMHO I think you had the answer it in your first post! The sidewall construction differences.

That has more to do with slip angle and the Michelins that come with the car have very low slip angles, more like a racing tire. IMO that is what causes the much higher "Chatter" when it's cold, more than tire width, size, Ackerman settings and tread compound.

My Z51 C6 had the same tire width and my Z51 C7 and no where near the chatter when backing out of my garage on a cold morning! My 3 week old Grand Sport will probably be worse when it gets cold again. Now, with warm weather I make a full look turn to go down the driveway after backing straight out of the garage and zero chatter. In the winter, with my 2014 Z51 had to make one or two K" turns or car would literally hop! May not have done any harm but felt bad!

Doubt you could get Michelin to discuss it!

BrunoTheMellow

tread width is all on tire rack. If you google pilot super sport spec. Michelin website is one of the first. It is located on the sidewall. A * is BMW, MO is Mercedes, TPC is for GM cars, K1 is Ferrari.

Jay_Davis

I finally got to really push the 4S tires today. I didn't have any problems and they worked fine. Two things:
1. They didn't seem to be better the MPSS. Was running about the same times. Was my first day out though, so my brain was rusty.
2. They are definitely noisier than the MPSS. They really like screeching.

BrunoTheMellow

Yeah I don't understand people that are expecting them to be much better. Even according to Michelin, they are only marginally better in dry traction