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There has been quite a lot of discussion about this on the C7 forum. A lot of people believe the latest versions ride as good and have the same noise level as the non-runflat versions.
I have yet to see a back to back comparison between runflats and non-runflats of the same line.
From a street performance standpoint you're probably better off going with the OEM design (summer or A/S depending on what you are looking for) since they were designed for the C8.
Correct, many folks are relying upon a perception about zero pressure (ZP) or "runflat" tires that is more than a decade old. Tire technology has advanced dramatically since ZPs were first introduced. It also depends upon whose ZPs you're talking about as manufacturers have different designs.
Michelin ZPs have the same exact sidewalls, same exact rubber compounds, and same exact tread blocks as their non-ZP counterparts. Michelin ZPs employ an extra band next to the inner sidewall to support the tire at zero pressure. When inflated, Michelin ZPs are essentially indistinguishable from non-ZPs. The only downside is a slight increase in unsprung weight with the ZPs.
The only downside is a slight increase in unsprung weight with the ZPs.
There may be another one, although probably not a big player. Recently I was driving on I-20 south of Dallas when I hit a huge pothole on the left front. Hit was so violent I was sure I had to have bent/broken something. As it was (the story is a lot longer), it ended up that the non-RF tire took the damage:
Would the stiffer sidewall of a RF tire have transmitted enough energy into the wheel to bend/break it? Can't say definitively (and I'm NOT going to go experiment with it!), but I think it's a decent possibility.
Other than that, I won't fight either way. IMO the reason people think RFs are hard, stiff, etc. compared to the non-RFs they replace them with is that the RFs were OLD. I don't care what tire you have, when it's lived long enough to be replaced, it's not going to have the performance it had when new. Then you compare them to the new tires (RF or non) and the new ones are SO MUCH BETTER. Well, I hope so!
Again, the sidewall is NOT stiffer in a Michelin ZP. They are exactly the same sidewalls. The only difference is an inner band which supports the car at zero pressure. There's no reason to believe your encounter would have been any different with a ZP except that you would have been able to keep driving at reduced speed for up to 100 miles or more.
There's a picture that's been posted here dozens of times on this forum by a veteran member showing her PSS ZP with a softball-sized chunk of the sidewall missing after a hard impact with the mother of all potholes on a road trip in the middle of nowhere. She was able to drive 100 miles at zero pressure to get to a place where it could be fixed.
There may be another one, although probably not a big player. Recently I was driving on I-20 south of Dallas when I hit a huge pothole on the left front. Hit was so violent I was sure I had to have bent/broken something. As it was (the story is a lot longer), it ended up that the non-RF tire took the damage:
Would the stiffer sidewall of a RF tire have transmitted enough energy into the wheel to bend/break it? Can't say definitively (and I'm NOT going to go experiment with it!), but I think it's a decent possibility.
Mike
Originally Posted by Foosh
Again the sidewall is NOT stiffer in a Michelin ZP. They are exactly the same sidewalls. The only difference is an inner band which supports the car at zero pressure. There's no reason to believe your encounter would have been any different with a ZP except that you would have been able to keep driving at reduced speed for up to 100 miles or more.
There's a picture that's been posted here dozens of times on this forum by a veteran member showing her PSS ZP with a softball-sized chunk of the sidewall missing after a hard impact with the mother of all potholes. She was able to drive 100 miles at zero pressure to get to a place where it could be fixed.
This is demonstrated at the Spring Mountain Corvette Owner's school. They have cut outs of the ZP tires and discuss the construction of the tires during the class. The outer sidewall is the same as a non run flat. Only the inner sidewall has a stiffener in it. You can hold the cutaway in your hands and feel the difference between the two sides of the tire.
One of the big reasons run flat handling has increased so dramatically from the old C5 EMTs is GM dropped the 200 mile zero pressure requirement. GY had to make those tires stiff to be able to run for 200 miles and still be repairable. Once the requirement dropped to 50 miles for the C6 even the EMTs became more sporty and performed well on track. Lightning Lap results from the 2007 era showed C6 Z06 running faster laps and C6 Z51 running slower laps than 911s equipped with the track flavored Michelin Cup 2 tires of the time. That is an indication those tires weren't as bad as people the people dumping on them thought. True capability isn't determined by how much grip a tire has when you drop the hammer on the throttle at low speeds in the lower gears.
To echo everyone: I have a friend with a C6, years ago he replaced the Goodyear EMT's with C7 Pilot Super Sport RF's and he told me it literally transformed his car.
There is NO comparison between the old C6 Goodyear EMT's and current runflats.
Some people hate them. Get rid of them immediately or wear them out then go for non runflats. I hear too hard,sidewall too stiff,lack of traction,lack of feel,too giggly. The new c8 comes with them but of course they can be traded out immediately. So what do people that have tried both think? I don't care about flats . Would take better handling and ride over peace of mind and some possible inconvenience anytime. GTS Bruce
It would track a bit better and cut down on that oversteer Y'all are concerned about.
Is that specific to Michelin or is that the general standard that all RF tires are using these days?
Thanks for the info; who says an old dog can't learn?
Have a good one,
Mike
I'm not familiar with ZP tire design and construction other than Michelin. And yep, no matter how old anyone is, there are plenty of new lessons to learn.
Went from MPSS ZP’s to MPS4S’s huge improvement. Without mag ride and stiffer shocks, thicker sway bars and lowered on stock bolts with the ZP’s my car rode like a empty 1 ton 4x4. The only way I’d keep the ZP’s is if I was going to use the car for road trips. I don’t, so I’d sell them and get non ZP’s one or two sizes wider front and rear and maybe one size lower too if they will fit.
Last edited by The Successful Plumber; 11-22-2019 at 05:36 PM.
IMO, the run flats have come a long way. In fact, the run-flats achieved the highest lateral Gs based on all of the tires tested here:
Maximum grip in Turn 1 from every Lightning Lap (2016)
No.1) Michelin Pilot Sport = 1.01 g No.2) Pirelli P Zero = 0.98 g No.3) Michelin Pilot Sport Cup = 1.16 g No.4) Michelin Pilot Sport PS2 ZP = 1.06 g No.5) Toyo Proxes R888 = 1.07 g No.6) Michelin Pilot Sport Cup ZP = 1.07 g No.7) Michelin Pilot Super Sport = 1.08 g No.8) Michelin Pilot Sport Cup 2 and Pirelli P Zero Trofeo R = 1.16 g No.9) Michelin Pilot Sport Cup 2 ZP = 1.20 g No.10) Michelin Pilot Sport Cup 2 ZP = 1.19 g
I quite agree. As I am getting old and lazy and hate changing tires, I have tracked my C7 GS with factory spec Michelin SS run flats (admittedly with a custom alignment and corner weighting) and have been most pleased with grip and handling. Great tires. Also, the added security of a run flat on trips and even at the track is a nice bonus. With mag ride, the "touring" setting ride is most comfortable.
Last edited by quick04Z06; 11-22-2019 at 05:41 PM.
I have driven Corvettes in 45 of the lower 48 states and in half dozen Canadian provinces - I have more than 800,000 miles in Corvettes over the past 29 years and 11 months..... there are place where one cannot get phone service, much less an appropriate tire... plus, at 78 this old man ain't going to change or plug a friggin' flat with the temp at 104 or 17....... I'll keep my RF tires....
This is demonstrated at the Spring Mountain Corvette Owner's school. They have cut outs of the ZP tires and discuss the construction of the tires during the class. The outer sidewall is the same as a non run flat. Only the inner sidewall has a stiffener in it. You can hold the cutaway in your hands and feel the difference between the two sides of the tire.
One of the big reasons run flat handling has increased so dramatically from the old C5 EMTs is GM dropped the 200 mile zero pressure requirement. GY had to make those tires stiff to be able to run for 200 miles and still be repairable. Once the requirement dropped to 50 miles for the C6 even the EMTs became more sporty and performed well on track. Lightning Lap results from the 2007 era showed C6 Z06 running faster laps and C6 Z51 running slower laps than 911s equipped with the track flavored Michelin Cup 2 tires of the time. That is an indication those tires weren't as bad as people the people dumping on them thought. True capability isn't determined by how much grip a tire has when you drop the hammer on the throttle at low speeds in the lower gears.
Bill
I saw that cut away at Spring Mountain. I don’t think the runflat tires feel Stiffer . They ride well and grip like crazy in warm weather. But I have a small pile of rims that are bent on the inner side(About 120 thousandths) and around 90 miles an hour they shake a lot and it gets worse as you go faster. I always blamed that thicker inner wall for bending the rim. I have been running continental non-run flats for about 40000 miles and I have never bent a rim with those. Just my experience. I think the more narrow rim and tire on the C8 Stingray will be less likely to bend the inner rim.
Modern Michelin runflats aren’t in the same universe as Goodyear runcraps of yesteryear. I tracked my C7 Z51 on the OEM MPSS 2X before going to a TT setup on Hoosiers. I was very surprised how good they were. Only issue is the 245 only had 3 fast laps in it before getting hot.
On the base car the std. tire will be a very close relative of the current Michelin AS3+ ZP UHP all-season. On the Z51, it appears to be the first ZP version of the Michelin PS4S max perf. summer tire.
I believe in using some good run flats for street driving so I would upgrade to PSS for the street and a set of Hoosier A6s for track and AutoX duty.
The PSS won't be your best upgrade if you are buying a C8 "base." And I've read that the C8-Z51 will come with the Michelin Pilot Sport 4S ZP. This tire is the eventual replacement to the Michelin Pilot Super Sport, and outperforms the PSS in every measure. Here are a handful of links explaining the 4S superiority over the PSS:
On the base car the std. tire will be a very close relative of the current Michelin AS3+ ZP UHP all-season. On the Z51, it appears to be the first ZP version of the Michelin PS4S max perf. summer tire.
Yes, the labeling is different, but the all season appears to be the AS3+ UHP ZP, which was an all new tire in 2016. It's newer, in fact, than the non-ZP version of the PS4S, which is appearing for the first time as a ZP on the C8.
The AS3+ is not available as a ZP in most sizes, but was specifically manufactured in OEM C7 sizes starting in 2016. When I heard that the base OEM tire on C8 was going to be a Michelin UHP all-season, that began to make more sense. I suspect Michelin made the decision to do it in consultation with GM, which may have been considering or had perhaps already decided to offer a UHP all season on the C8.
It is immensely popular on the C7, and Tire Rack has had difficulty at times keeping it in stock. I love them and swap the AS3+ and the PSS back and forth between winter and summer. The AS3+ is nearly as good for street use as the PSS in warm weather, and vastly superior in cool temps.
11-22-2019, 10:41 AM
