ACELR8N

An earlier post concerning the repair of a run flat tire resulted in a link to a Hib Halverson article about run flats. Within the article he pointed out that neither Yokohama nor Firestone run flats were repairable. I have excerpted the article below, and also provided the link. The highlighted section indicates what he said about being repairable. This concerns me because I just ordered four Firestone Firehawk SZ50 EP tires, which consistently received high grades for performance, wet driving superiority, and longevity. They are also recommended by a few consumer organizations. But, if they are not repairable and have to be trashed after a run flat incident, what good are they? I researched Firestone's website and found specific warranty information that the tires will be replaced on a pro-rated basis within six years of purchase for any reason that renders them unuseable. However, I think this repair/patch issue is important enough to share and discuss. Any insights about repairablility of Z rated run flats is welcome, especially since many of us are driving with repair patches.

Corvette Action Center Article: (excerpted) After repair, the left rear EMT on the LoMonoco's 2001 drove as if nothing had happened at all. After testing the no-longer-flat, run-flat tire for a while, I turned the car back over to Mike who took the car back to his home. That repaired EMT remained service on that '01--which wife, Crescent, drives daily--for another 3450 miles which included a trip with Mike and Crescent's club, Corvette Club Santa Barbara, where there were times when they were driving as fast as 112 mph and a round-trip to Las Vegas, Nevada in 108° summer heat. The tire was finally replaced when Mike installed a new set of F1 GS EMTs.

Could we run the same test on any other run-flat tire on the market for C5s? Wondering about that, as well as if noise and ride improvements by some aftermarket run-flats come at the expense of actual run flat performance, I contacted Michelin North America. According to spokesperson, Phil Romba, the Michelin Pilot Sport A/S Zero Pressure is rated for 50 run-flat miles at 55-mph and is repairable in a manner similar to that of the Goodyear. Next, I contacted Tiffany Bryant, spokesperson for Bridgestone/Firestone USA, and Dan Guiney, spokesperson for Yokohama Tire Company. They told me that the Firestone SZ50EP RFT and the Yokohama AVS Sport Run-Flat are, also, rated for up to 50 miles of 55-mph run-flat operation, however, after any run-flat incident, neither can be repaired and both must be scrapped.

None of the aftermarket run-flats for '97-'04 Vettes are capable of going 200 miles deflated. That got my attention because it means that neither the Michelin Pilot Sport A/S Zero Pressure, the Firestone SZ50EP RFT or the Yokohama AVS Sport Run Flat meet General Motors specifications for C5 tires

I contacted Michelin North America, Bridgestone/Firestone USA and Yokohama Tire Company a second time to ask: 1) why their run-flats do not meet the vehicle manufacturer's tire specification and 2) are those purchasing run-flats for Corvettes advised of that situation.

All three companies had three weeks to respond but chose not to answer by our deadline.

We can only wonder why Michelin, Firestone and Yokohama products are unable to go the 200 miles GM specifies. Is it because the aftermarket is unable to duplicate some engineering, materials or manufacturing processes used by Goodyear? To reduce noise and improve ride, are Firestone and others using less-stiff casings which might compromise deflated handling and durability?

If those purchasing aftermarket run-flats aren't told what they're buying is incapable of the same performance as what came on the vehicle; why aren't they? Again, because Michelin, Firestone and Yokohama never responded, we can only speculate. Perhaps, if some customers were aware of the facts, they might not make the purchase and that could be an incentive to not disclose such information.

So what does all this mean for C5 owners intent upon purchase of replacement, run-flat tires? It means: if you want the same performance under run-flat conditions you had when your car was new, your choice is simple: the Goodyear Eagle F1 GS-EMT because it's the only run-flat which meets General Motors specifications for safety and longevity of extended mobility tires.
http://www.corvetteactioncenter.com/....php?qstId=515

Evil-Twin

The New Goodyear EMT will drop the 200 mile rating down to 100 miles @ 55 mph.... for this they were able to incorporate two different tire compounds, one a touring compound, the other a performance compound.. there is always give and take with engineering a tire... GM didnt pick Goodyear to build the tires for their flag ship C5, because they were the cheapest.. and they continue to lead the tire industry for the C6... Goodyear makes the best tires on the planet. Anyone considering a wheel change, I would suggest 18's front and 19's rear, and when they become available , put the your choice of compounds (New Goodyear EMT's on there...)
FYI, also after a GM national survey of loyal corvette owners.. everyone wants run flats so the New C6 Z06 will also be run flat... opinions on this forum are a small part of the corvette community.. about 1100 active C5 members here as oppose to the 250,000 C5 owners world wide.

GR8-LIFE

I got nail on my tire within the first month of taking delievery. Had it plugged. Never had a problem for the 3 yrs that I had them before I went to a conventional HP tire.

gordonb50

I just replaced my tires (a week ago) after going through a very similar reasearch effort. As a result, I elected to stay with the GY runflats. I like the safety factor of the runflat design AND I'm 130 miles from the nearest city that will work on / replace EMT's.

HalfMoon

I got 2 nails in my brand new Kuhmo Runflats. Called Tire Rack and two different reps told me that if they didn't go totally flat, just plug them. They both said the only time you need to replace them is if the sidewall was stressed by running without any pressure.

Keep an eye on the pressure sensors in the DIC and if you notice any drops, look at the tires for damage, don't wait for a full on blow-out.

jsdanehy

Evil you are on the mark (as usual)

ACELR8N

Any one have any opinions why some run flats aren't repairable? I don't understand why you could patch a Goodyear but not a Firestone. Seems to me something the corporate attorneys mandated. I can understand Goodyear being driveable for further distances in the runflat mode because of stiffer sidewall and different rubber compositions, but the patch/repair issue makes no sense.

C5inWV

I got a flat in one GY eagle EMT on the way to MidOhio early this year. Patched it, and still ran all out at the track, then drove it home. Will replace the tire soon due to treadwear rather than the plug.

Y2Kvert4me

That's exactly it. The tire mfr can't guarantee what shape the tire is in after a flat or repair. You can patch any tire, and after such epair it will probably hold air and work just fine. Will the mfr make a broad guarantee, or even advise you that it's still good and can perform as new? As you've seen, probably not.

Best judgement and common sense still work in a case like this. Not all flats or punctures are the same. You, and your tire guy will need to assess your exact problem and determine from there what the best and most reliable way to resolve it. Maybe you can patch it and it'll be good for another 20k miles, maybe it'll fail 5 miles down the road....this is a case-by-case thing no matter what, Making a blanket statement that the tires cannot be repaired at all is only a safe means of avoiding any liability for the tire mfr.

Dave68

A Goodyear representative told me that their EMTs will retain their speed rating after one non-sidewall repair. After a second repair/plug, all bets are off.

Everyone raves about the better ride qualities of non-OEM runflats, not to mention the even better ride qualities of non-runflats such as the GS D3s, but that better ride comes with, as Evil mentioned, compromises, the biggie being less distance after zero pressure.

GM has partially compensated for the punishing ride of its OEM runflats by coming up with the magnetic-fluid shocks. Unfortunately for those whose cars are not equipped with this technology, the best solution for a decent ride is to buy non-runflats. People will rave about the new C6 with magnetic shocks and "milder" runflats, but I can almost guarantee that a C5 with non-runflats has a ride that is very close, if not equal to the C6 ride.

Now maybe the C6 OEM tires are head and shoulders above the EMTs of C5 fame (or lack of in this case), but until I find them to be eual to my GS D3s, I'm sicking to non-runflats.

Evil-Twin

I got two flats in the same tire within 1000 miles of each other, at around 5000 miles.. I plugged both holes and contuinued to put another 38,000 miles on that tire. I replaced all four tires at 43000 miles and still had 4/32 on the fronts and 3/32 on the rears... and one of the rears had two plugs in it and never once leaked or gave me any trouble.

Dave68

I'll take a wild guess and say that you probably never pushed your C5 anywhere near the top-speed rating of the tires either.........!

markcz

That's almost exactly what I was going to say.

ANY tire is repairable. The problem is the damage done to the tire while you're driving around on it with zero pressure. GY is confident that you won't hurt the tire for the first 200 miles as long as you stay under 50 MPH. The other companies that say the tires aren't repairable (one of which I work for) are just doing the CYA thing because they have no way of preventing you from driving too far or too fast on the 'flat' tire. As quoted above, if your tire guy feels comfortable repairing a non-GY EMT, then go for it, but if's hesitant then get a new tire.