rikhek

There are a good number of posts from people asking if the tread compound on the MPSS run flat is different than the MPSS non-run flat. I've not been able to find a definitive answer to this question.

As I'm switching to non-run flats I wanted a definitive answer. I'm switching for a several reasons. The main one being I've bent all 4 of my wheels running the ZP tires. I drive my car pretty hard and all in the twisties. I'm hoping the softer sidewall will absorb some energy and stop bending my wheels. GM just replaced 3 of my 4 wheels under warranty. The 4th was bent but not beyond acceptable runout. A good number of other owners who utilize the car as I have bent a bunch of wheels as well. If you drive hard on them with the ZP tires they will bend. They are pretty much cheap ***, junk wheels and not suitable for cars driven hard. I'm hoping this will solve my bent wheel problem as I don't want to have to buy "real" forged wheels for the street. I have a set of 18" forged on the way for track usage.

Another lesser reason is I only get about 4,500 miles out of a set and the non-run flats are less expensive. I'm buying 3 to 4 sets of tires a year with just street usage and it's just a weekend car! They also weigh less than the run flats.

I contacted Michelin directly and asked the question. I was informed by Michelin the tread compound is exactly the same on the two tires.

I also contacted Tire Rack and asked the same question. They also informed me the compound was exactly the same. I put more faith in the answer from Michelin but it was nice to get the same answer from Tire Rack.

I do realize the sidewall construction is different as is the weight. Sizing in non-run flat is also a little different than OEM but not enough to make a difference.

- Fronts are 285/30/19 run flat and 295/30/19 non-run flat.
- Rears are 335/25/20 run flat and 325/25/20 non-run flat.

I also asked Michelin if they could provide the tire spring rate for all four tires listed above. I'm thinking I might have to have Mike Levitas write me a custom DSC Sport Magnetic Shock Controller file for the non-run flat tires due to the different tire spring rates. Michelin informed me they do not provide/publish the spring rates for their tires.

I'll drive the car and get a feel before I determine if a custom DSC Sport shock controller file is needed. I won't know for sure for a month or so as I only mounted the front non-run flats today. I have maybe another month of rubber left on my rear run flats which I'll run until they are shot....

Rick

dvandentop

i figured they werent any different. i have been running the non run flats since last august

BrunoTheMellow

did you mean to write that the sizing difference is backwards for each set?

- Fronts are 285/30/19 run flat and 295/30/19 non-run flat.
- Rears are 335/25/20 run flat and 325/25/20 non-run flat.

vs

- Fronts are 285/30/19 run flat and 295/30/19 non-run flat.
- Rears are 335/25/20 run flat and 345/25/20 non-run flat.

Does this mean the non-runflats should be purchased at a size bigger to match width? Note that there are sometimes 3-4 different types of the "same" tire. For example, a MPSS 245/35/19 has 3 different "styles" with different tread widths.

rikhek

No, what I wrote is correct. The 345 you highlighted is a 345/30/20 which would be a very tall side wall. The 325/25 is the closest they make to OEM sizing.

However, the tread width on the non-run flat 325 is 13.1" versus 13.0" on the OEM 335 run flat. The section width on the 325 is 13.2" versus 13.5" on the 335. I'm more interested in tread width than section width.

The 325 also comes with 9/32" tread versus 7.8/32" on the 335. I'll take the extra tread depth as I'm lucky to get 4,500 miles out of a set of tires on the street.

Michelin makes two different 295/30/19 non-run flat tires. One is a GM spec tire for a Camaro and is the more expensive one of the two. I opted for the less expensive non Camaro tire...

Rick

phantasms

Rick. I see the measurements above but do they appear to be any skinnier? Not inches wise just general look when on the car.

Thanks!

Best,
Gene

rikhek

Gene,

I don't know. As stated above I only had the 295 front non-run flats mounted today. I still have a few runs through the twisties left on my rear 335 run flats. I'll run these on the back with the non-run flats on the front until they are shot in less than a month by my best guesstimate.

I really don't think anybody will be able to tell with the naked eye. You're only talking 0.3" narrower section width on a pretty big tire and, the tread width is actually wider on the 325.

Rick

BrunoTheMellow

Interesting, there seems to be no rhyme or reason. Be careful with choosing which tire to buy for each size. My brother bought some MPSS 275/35R20 front tires and they have MASSIVE ridges in between and he complains a lot about understeer on his mustang (which he didn't have before)

mtaylor

What are most people using to fix flats since there is no spare when swtiching to non runflats?

rikhek

Bruno,

Not sure what he bought but not an issue in my/our situation.

And it does make sense from an engineering standpoint. The ZP construction mandates variances in section width to get the ability to run flat. This changes the geometry of the rest of the tire. The only questionthat has never been definitively answered is regarding the tread compound composition.

The tread pattern on the non-run flat is identical to the ZP. No ridges or other cosmetic differences as you observed on your brothers.

Myself and many others before me have made similar changes on C6 and C5 Corvettes as the Goodyears run flats they used to provide as OEM tires were garbage.

In post number 2 it's stated he's already running the same setup as I. A good number of others on the forum are as well. I was just trying to put the tread compound question to bed....

Thanks for the info.

Rick

rikhek

Most of us carry a small 12 volt compressor, a pair of needle nose pliers and a plug kit. I also carry a AAA card and GM offers free roadside assistance as does Michelin and many insurance companies.

Also, most can't remember the last time they had a flat, if ever, that left them stranded.....

BrunoTheMellow

I researched some more. Like I said, different versions of the same "michellin pilot super sport" as you know.

From michellin website:

OE [Vehicle Manufacturer] Sidewall Marking: K# = Ferrari, MO= Mercedes-Benz, N# = Porsche, TPC = GM, * = BMW

These will give different thread patterns, section widths, weights, tread widths, etc. For example, tire rack sells two MPSS 295/35r19 versions as you said. Here are the details. That is a large difference in weight and thread width.

295/30ZR19
(100Y) XL
TPC Spec
thread depth 9/32" weight 31 lbs. sect width 11.8" thread width 10.7"

295/30ZR19
(100Y) XL
thread depth 10/32" weight 28 lbs. sect. width 11.9" thread width 11.5"

Like you said, you picked the "other" which has a much wider thread width. That is good to know for others before they purchase.

spearfish25

The really interesting part is the non-TPC tire has a deeper tread, a wider tread, and still weighs 3lbs less.

Firemedic301

I realize you run your car hard on the "twisty's", but you must be HAMMERING some fairly nasty **** to bend a rim. Tons of people track their cars HARD without bending rims. Do you hit some significant potholes?

rikhek

No, I really don't. I can't even remember hitting a cringe worthy hole. Also, it got progressively worse over time. My son actually noticed last time he drove it. He asked me about the "vibration". I hadn't noticed as it wasn't all at once.

Do a Search on the word "bent" in titles and thread body and you'll see a bunch of guys are bending wheels. I was surprised until I saw it was a fairly common occurrence.

spearfish25

Well I thought I only bent my right front. Turns out my rear wheel is bent too. These wheels are turds. No question they are not engineered to deal with the stresses of the ZP tires. Both wheels have bends on the inner bead where the ZP tire is reinforced.

gve

My Z has got a slight vibration, how do I check for a bent rim? Is it visible as I rotate a tire or do I need a dial indicator?

spearfish25

My front wheel's bend was painfully obvious and the flattened portion could be seen just by looking at it. The rear I didn't notice until this morning when the dealer put it on their balancer and checked the runout.

davepl

Last time I called OnStar for a flat they couldn't make it. No trucks available in the area. Too bad, No Soup For You!

Runflats may use the same rubber compound, but I presume the sidewall construction is beefed up or that there are other construction differences with the tire that would cause it to ride different (presumably more stiffly in the runflat)?

rikhek

I was having new tires installed and the tech called me and informed me all 4 were bent. He saw it as they rotated when he was balancing. As stated above this explained my son's observation that the car had a vibration.

AORoads

I realize you know very well how to handle your car from your posts/threads. But, I urge you to be cautious since you now have two non-runflats on the front (plus they are new), and two runflats on the rear, and they are not new tires. You have at least three things going on that are not standard.