[ANSWERED] Run-flat, EMT, ZP Tires
06-28-2017, 01:01 PM
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[ANSWERED] Run-flat, EMT, ZP Tires
The original question is here.
Nate@VanBortelChevy asked:
Could you tell us about the evolution of run-flat/ZP tires, the reason why they are standard equipment on Corvettes, and the challenges faced from an engineering stand point?
Could you tell us about the evolution of run-flat/ZP tires, the reason why they are standard equipment on Corvettes, and the challenges faced from an engineering stand point?
Tadge answered:
Good question, Nate. Your thumbnail history in the question is quite accurate. I was working on C5 in 1993 when we did not know how well the extended mobility tires would work in the field or be accepted by customers. Most people appreciate the extra luggage room afforded by not having to carry around a spare tire all the time even though it is rarely used. But for a relatively compact car with large wheels and tires, the important issue is where do you put the that big rear wheel you took off after installing the space-saver spare? It would be quite unsatisfactory to have to leave the wheel behind, especially nice Corvette wheels. One of the reasons the C5 had such a large trunk with a deep center well, was that we still had to package for a removed road wheel. To accommodate that deep well, we had to design for less muffler volume than we would prefer. Low volume means increased back-pressure and less tuning flexibility for sound quality.
Many manufacturers use a sealant/inflator kit as an alternative to a spare tire. It saves room in the trunk and you don't have to carry a replaced wheel in the car. As you mentioned, we did that for the C5 Z06. The feedback we received on these kits from our Corvette customers was mixed at best. The sealant may not always seal 100% and it is only a temporary solution as we recommend that the punctured tires be inspected and permanently repaired. I found myself stuck roadside with a flat once in a C5 Z06 because I couldn't get it to seal. The sealant is only effective with punctures in the tread area up to a 6mm diameter and it cannot repair tires with punctures in the sidewall. At that time the sealant also interfered with the tire pressure monitors (mounted on the valve stem) that customers really like. Obviously, there are lots of personal safety reasons we do everything possible to keep our customers from being stranded. The sealant did provide many customers the ability to continue their drive to where they needed to go, but we believe the zero pressure tires are a better solution for Corvette customers.
When Extended Mobility Tires were first introduced on the C5, they were very conservatively designed. Goodyear wanted to make sure that the zero pressure performance was good both in terms of vehicle handling and flat tire mileage. The compromises you cite were very obvious in those days because the tire sidewall had to be designed stiff enough to support the weight of the car. Since then, technology has advanced considerably for both run-flat and conventional tires. Corvette has essentially the highest performance street tires in the world. Together with Michelin, we have been pushing the performance envelope far beyond what many thought possible with street tires. We have worked with them extensively to minimize the mass and ride penalty to get ZP performance we need. The truth is, even without ZP capability, a conventional tire needs very stiff sidewalls to manage the lateral loads and our required steering response. So in the realm of super high performance tires, the designs for ZP and non-ZP have converged to where the mass and ride penalties are very small. The same is also true for noise and cost. Tires are the single most important component in vehicle handling performance. We and Michelin pay a lot for development and construction, making every effort to offer the best performance tires in the world. Conventional or ZP, they would cost more than lesser performing tires.
Good question, Nate. Your thumbnail history in the question is quite accurate. I was working on C5 in 1993 when we did not know how well the extended mobility tires would work in the field or be accepted by customers. Most people appreciate the extra luggage room afforded by not having to carry around a spare tire all the time even though it is rarely used. But for a relatively compact car with large wheels and tires, the important issue is where do you put the that big rear wheel you took off after installing the space-saver spare? It would be quite unsatisfactory to have to leave the wheel behind, especially nice Corvette wheels. One of the reasons the C5 had such a large trunk with a deep center well, was that we still had to package for a removed road wheel. To accommodate that deep well, we had to design for less muffler volume than we would prefer. Low volume means increased back-pressure and less tuning flexibility for sound quality.
Many manufacturers use a sealant/inflator kit as an alternative to a spare tire. It saves room in the trunk and you don't have to carry a replaced wheel in the car. As you mentioned, we did that for the C5 Z06. The feedback we received on these kits from our Corvette customers was mixed at best. The sealant may not always seal 100% and it is only a temporary solution as we recommend that the punctured tires be inspected and permanently repaired. I found myself stuck roadside with a flat once in a C5 Z06 because I couldn't get it to seal. The sealant is only effective with punctures in the tread area up to a 6mm diameter and it cannot repair tires with punctures in the sidewall. At that time the sealant also interfered with the tire pressure monitors (mounted on the valve stem) that customers really like. Obviously, there are lots of personal safety reasons we do everything possible to keep our customers from being stranded. The sealant did provide many customers the ability to continue their drive to where they needed to go, but we believe the zero pressure tires are a better solution for Corvette customers.
When Extended Mobility Tires were first introduced on the C5, they were very conservatively designed. Goodyear wanted to make sure that the zero pressure performance was good both in terms of vehicle handling and flat tire mileage. The compromises you cite were very obvious in those days because the tire sidewall had to be designed stiff enough to support the weight of the car. Since then, technology has advanced considerably for both run-flat and conventional tires. Corvette has essentially the highest performance street tires in the world. Together with Michelin, we have been pushing the performance envelope far beyond what many thought possible with street tires. We have worked with them extensively to minimize the mass and ride penalty to get ZP performance we need. The truth is, even without ZP capability, a conventional tire needs very stiff sidewalls to manage the lateral loads and our required steering response. So in the realm of super high performance tires, the designs for ZP and non-ZP have converged to where the mass and ride penalties are very small. The same is also true for noise and cost. Tires are the single most important component in vehicle handling performance. We and Michelin pay a lot for development and construction, making every effort to offer the best performance tires in the world. Conventional or ZP, they would cost more than lesser performing tires.
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06-28-2017, 03:01 PM
#2
Platinum Supporting Dealership
Very cool! I didn't realize that the sidewall needed to be relatively stiff to achieve the required amount of grip and performance. Makes sense to go run-flat and have both performance and the safety of a run-flat.
06-30-2017, 06:18 PM
#3
Team Owner
There's no freaking way in hell, I'd be on the side of an expressway, trying to "fix" a deflated tire!!!
If I incur a "flat", I'll drive to the next exit, and change the tire. If I ruin the tire, so what, my personal safety is paramount, BUT in order to be able to do that, I have to have a spare tire. Since a C-5, such as I own, doesn't have a spare tire onboard, I'll stick with the run-flats....
07-03-2017, 07:06 PM
#4
There's no freaking way in hell, I'd be on the side of an expressway, trying to "fix" a deflated tire!!!
If I incur a "flat", I'll drive to the next exit, and change the tire. If I ruin the tire, so what, my personal safety is paramount, BUT in order to be able to do that, I have to have a spare tire. Since a C-5, such as I own, doesn't have a spare tire onboard, I'll stick with the run-flats....
07-04-2017, 08:03 AM
#5
Team Owner
Does that 12V, portable air pump, fix the puncture for you? No, it doesn't, so you're still potentially sitting by the side of a busy highway, trying to find, then plug the puncture, BEFORE you can plug in your 12V air pump.
NO, thanks, not for me.............
NO, thanks, not for me.............
07-04-2017, 10:27 AM
#6
@Leadfoot4: You don't have to plug the run flat tires before filling it with more air. The run flat tires allow you to drive up to 50 miles so the portable air pump is a good temporary fix so that you can drive to the nearest Discount Tire store.
07-04-2017, 10:59 AM
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St. Jude Donor '12-'13-'14-'15-'16-'17-'18-'19-'20-'21
It's a viable countermeasure if you need to go further than 50 miles to get the tire replaced or to get home.
I might add that many places don't have the equipment or sometimes even the desire if they have the equipment to fix/replace runflat tires. I had to replace my worn OEM Michelins recently and had to take the tires I purchased from one tire dealer and have the dealership where I bought my Stingray mount them because even though the tire dealer had the equipment to mount runflat tires, they didn't have competent or willing personnel to do the job.
Apparently, runflat tires are a bear to remove from wheels and a bigger bear to mount back on to a wheel.
I still wouldn't drive my Stingray without runflat tires installed
07-04-2017, 06:31 PM
#8
Team Owner
I might add that many places don't have the equipment or sometimes even the desire if they have the equipment to fix/replace runflat tires. I had to replace my worn OEM Michelins recently and had to take the tires I purchased from one tire dealer and have the dealership where I bought my Stingray mount them because even though the tire dealer had the equipment to mount runflat tires, they didn't have competent or willing personnel to do the job.
Apparently, runflat tires are a bear to remove from wheels and a bigger bear to mount back on to a wheel.
I still wouldn't drive my Stingray without runflat tires installed
Apparently, runflat tires are a bear to remove from wheels and a bigger bear to mount back on to a wheel.
I still wouldn't drive my Stingray without runflat tires installed
07-04-2017, 07:17 PM
#9
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ptran00 (07-04-2017)
07-05-2017, 07:53 AM
#10
Team Owner
I respectfully disagree with that line of reasoning. And from this day forward, vow to NEVER AGAIN, get involved in a tire discussion on this forum.
07-05-2017, 09:11 AM
#11
Le Mans Master
I am very happy with these factory tires, and they already saved my butt once after hitting a wicked pothole! I think a conventional tire would have put me into the concrete center divider, but instead I was able to easily and safely drive the car in to the dealership for repair.
