Swapping rear tires to even wear
07-12-2007, 04:26 PM
#16
Originally Posted by wdonovan
He's not a surgeon. He's a tire changer. TELL him to do it, don't ask him. Tell him you'll pay him.
07-12-2007, 04:35 PM
#17
Former Vendor
Some good points by all.
We don't recommend it.
For track use, you may get a bit more life out of the tire if the tread depth is at 2 or 3/32 or almost worn completely. Above that and the car could seem unsettled. Some track tires are designed with body plies that come together at 45 degree angles. Turning them around allows the ground to "pick" them apart because the leading edge of the splice is hitting the ground first as opposed to the trailing edge had they been rolling the intended way.
For street use it may be bad as it throws too many variables into the mix. Asymetric tires usually have larger tread block on the outside shoulder and are designed to move laterally a specific way according to how they are designed, and actually use the hinge points of the tread design to move as they corner. When you flip them and then push them into a corner and they are backwards, the tire could deform significantly more than if they were installed correctly. If they are directional, the above happens on top of a significant reduction in hydroplane resistance. Some tires (the PS2, for example) almost certainly use different rubber compound mixes on one side of the tire than the other as well. Flipping them could result in much faster wear than expected - several times faster.
Of course you could tune some of the camber out of the alignment and reduce the improper wear, but in doing so you of course reduce some of the steering ability and capability of the car.
I guess the bottom line is that nobody can make the promise by doing so you will not gain a bit more tire life at the expense of wrecking your handling. And unfortunately, it takes the expense and risk to your wheels of a tire change to see what you have done.
Cost of ownership......
We don't recommend it.
For track use, you may get a bit more life out of the tire if the tread depth is at 2 or 3/32 or almost worn completely. Above that and the car could seem unsettled. Some track tires are designed with body plies that come together at 45 degree angles. Turning them around allows the ground to "pick" them apart because the leading edge of the splice is hitting the ground first as opposed to the trailing edge had they been rolling the intended way.
For street use it may be bad as it throws too many variables into the mix. Asymetric tires usually have larger tread block on the outside shoulder and are designed to move laterally a specific way according to how they are designed, and actually use the hinge points of the tread design to move as they corner. When you flip them and then push them into a corner and they are backwards, the tire could deform significantly more than if they were installed correctly. If they are directional, the above happens on top of a significant reduction in hydroplane resistance. Some tires (the PS2, for example) almost certainly use different rubber compound mixes on one side of the tire than the other as well. Flipping them could result in much faster wear than expected - several times faster.
Of course you could tune some of the camber out of the alignment and reduce the improper wear, but in doing so you of course reduce some of the steering ability and capability of the car.
I guess the bottom line is that nobody can make the promise by doing so you will not gain a bit more tire life at the expense of wrecking your handling. And unfortunately, it takes the expense and risk to your wheels of a tire change to see what you have done.
Cost of ownership......
07-12-2007, 05:03 PM
#18
Three Wheelin'
The contis, and all asymmetric non-directional tires, can be swapped (without dismounting from the wheel) from left to right without a problem. But it sort of defeats the purpose since the inside of the tire would still be the inside of the tire. These types of tires should NOT be dismounted from the wheel and reversed since they are by design, intended to have the interior of the tread block facing inwards. Turning it outwards would undermine what the tire engineers designed.
Symmetric directional tires CAN be dismounted from the wheel and swapped to the other side of the car if you are wearing away the interior of the tire. However, they must be dismounted, for if you simply swapped the wheels without doing so, they'd be facing backwards.
You can do whatever you bloody well feel like with symmetrical non-directional tires. Make a tire swing for all one cares.
Symmetric directional tires CAN be dismounted from the wheel and swapped to the other side of the car if you are wearing away the interior of the tire. However, they must be dismounted, for if you simply swapped the wheels without doing so, they'd be facing backwards.
You can do whatever you bloody well feel like with symmetrical non-directional tires. Make a tire swing for all one cares.
07-12-2007, 05:34 PM
#20
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My buddy does it all time with Michelin Sport Cup tires he never had a problem. He drives 110miles to the track and back home. He has a 03 TT and has been doing this for a couple of years.
07-12-2007, 09:49 PM
#21
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Newport996 - How about this...the tread is designed to evacuate water by channeling it in a certian direction with respect to the way the wheel rotates...you reverse that, it loses its ability to evacuate water effectively, and you have created a situation where ALL 4 tires are prone to losing grip in the wet. Not safe. Thats just ONE example of why its not good to reverse a directional tire.
Good point, I don't mean reversing the direction of the tire - I mean dismounting and remounting the tire so it goes on the other side of the car in the same proper rotation. And mine are just directional not different tread pattern from inside to outside.
Good point, I don't mean reversing the direction of the tire - I mean dismounting and remounting the tire so it goes on the other side of the car in the same proper rotation. And mine are just directional not different tread pattern from inside to outside.
07-12-2007, 10:32 PM
#23
Ah, the "I/my buddy do/does it all the time and never has a problem" argument. More power to you, but I could use the same defence for jaywalking. Doesn't make it a good idea. My money is on the tire guy. 
07-13-2007, 09:00 AM
#24
Three Wheelin'
Originally Posted by BruceP
My money is on the tire guy.
07-13-2007, 09:14 AM
#25
Originally Posted by nycebo
Of course, the board-certified, Ph.D. in quantum physics, automotive engineer. He's a tire installer. Nothing more. Nothing less. It's all hearsay. But as someone mentioned above, it's really squeezing nickels. In the end, the cost of remounting and rebalancing the tires probably offsets any savings.
Setting aside my personal crusade against nickel-squeezing with your Porsche, you have to admit that these decisions are not simple, binary arguments. You're playing the odds. To me (and I'll confess the bias of being involved in a lot of gear-intensive sports), the price of riding on fresh tires is worth the confidence you get when those super-legal speed opportunities come along. My car will occasionally see 200kph. The dubious advantages of delaying - not even avoiding, just delaying, mind you - a tire purchase pale at those moments.
07-13-2007, 09:34 AM
#26
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BruceP, Do you think that tire change mechanic subscribes to this rigid code of ethics? If he does, d oyou think he has the knowledge?
As far as "squeezing the nickel too hard", our friends at Porsche have managed to give us a suspension setup that is probably the most abusive on rear tires compared to almost anything on the road. I've been driving 600 HP Corvetyes for a couple decades and get 2 or 3 times the tire life than my 320 HP Porsche. The Corvette rear geometry doesn't use such stupidly high numbers for negative camber. I think it's within the owner's rights to try to get a little more use from his tires than just the inside edge.
Damon, Agreed. Directional tires should not be rotated the wrong way. Agreed, asymmetric tires should not be run with inside edge out. But it seems to me that you're combining two not necessarily unrelated things together and assuming they both apply to these (any) particular tires. The only tires that could not be switched because of these rules would be ones that are both directional and asymmetric, right? This would mean that your rear tires would have two distinct part numbers, correct? So if the tires are the same part number left and right, and have less wear than you'd like to see, what is the reason not to switch them?
As far as "squeezing the nickel too hard", our friends at Porsche have managed to give us a suspension setup that is probably the most abusive on rear tires compared to almost anything on the road. I've been driving 600 HP Corvetyes for a couple decades and get 2 or 3 times the tire life than my 320 HP Porsche. The Corvette rear geometry doesn't use such stupidly high numbers for negative camber. I think it's within the owner's rights to try to get a little more use from his tires than just the inside edge.
Damon, Agreed. Directional tires should not be rotated the wrong way. Agreed, asymmetric tires should not be run with inside edge out. But it seems to me that you're combining two not necessarily unrelated things together and assuming they both apply to these (any) particular tires. The only tires that could not be switched because of these rules would be ones that are both directional and asymmetric, right? This would mean that your rear tires would have two distinct part numbers, correct? So if the tires are the same part number left and right, and have less wear than you'd like to see, what is the reason not to switch them?
07-13-2007, 10:56 AM
#27
Three Wheelin'
Originally Posted by BruceP
the price of riding on fresh tires is worth the confidence you get when those super-legal speed opportunities come along. My car will occasionally see 200kph. The dubious advantages of delaying - not even avoiding, just delaying, mind you - a tire purchase pale at those moments.
Originally Posted by wdonovan
So if the tires are the same part number left and right, and have less wear than you'd like to see, what is the reason not to switch them?
P.S. - This spring, I might have accidentally put the left rear wheel/tire on the right rear and vice versa when I was putting on the summers. I just couldn't remember which went where. No worries, though, I stored the winters in a manner such that I'll be able to recall it when it's time to swap back into them. Then again, I have Pirelli PZero Asymmetricos (which I'm not likely to be purchasing again by the way, but that's for another thread), so as long as the interior is still interior, I'm good to go. Not for nothing, the car's riding fine.
07-13-2007, 11:15 AM
#28
Originally Posted by wdonovan
BruceP, Do you think that tire change mechanic subscribes to this rigid code of ethics? If he does, d oyou think he has the knowledge?
As far as "squeezing the nickel too hard", our friends at Porsche have managed to give us a suspension setup that is probably the most abusive on rear tires compared to almost anything on the road. I've been driving 600 HP Corvetyes for a couple decades and get 2 or 3 times the tire life than my 320 HP Porsche. The Corvette rear geometry doesn't use such stupidly high numbers for negative camber. I think it's within the owner's rights to try to get a little more use from his tires than just the inside edge.
Damon, Agreed. Directional tires should not be rotated the wrong way. Agreed, asymmetric tires should not be run with inside edge out. But it seems to me that you're combining two not necessarily unrelated things together and assuming they both apply to these (any) particular tires. The only tires that could not be switched because of these rules would be ones that are both directional and asymmetric, right? This would mean that your rear tires would have two distinct part numbers, correct? So if the tires are the same part number left and right, and have less wear than you'd like to see, what is the reason not to switch them?
As far as "squeezing the nickel too hard", our friends at Porsche have managed to give us a suspension setup that is probably the most abusive on rear tires compared to almost anything on the road. I've been driving 600 HP Corvetyes for a couple decades and get 2 or 3 times the tire life than my 320 HP Porsche. The Corvette rear geometry doesn't use such stupidly high numbers for negative camber. I think it's within the owner's rights to try to get a little more use from his tires than just the inside edge.
Damon, Agreed. Directional tires should not be rotated the wrong way. Agreed, asymmetric tires should not be run with inside edge out. But it seems to me that you're combining two not necessarily unrelated things together and assuming they both apply to these (any) particular tires. The only tires that could not be switched because of these rules would be ones that are both directional and asymmetric, right? This would mean that your rear tires would have two distinct part numbers, correct? So if the tires are the same part number left and right, and have less wear than you'd like to see, what is the reason not to switch them?
On your Corvette reference, good for you. That's why the 'vette is the poor man's exotic. Rear tires are consumables on a 911. The work Porsche had to do to make a rear engined car handle as well, as safely and as predictably as the 996 and 997 do created a lot of compromises, as all engineering does. One is that it eats tires. If that's not tolerable, drive something else. If you're content to stretch them out a bit, even if it costs you some margin or some performance, you're correct. That is your right. All I'm saying is, I wouldn't do it. Not my lifestyle. If I took that attitude with every toy I have, the cumulative risk to my poor old bones would be unmanageable. So I take care of my stuff, and that includes not compromising safety and performance so I can leave a few hundred dollars in the bank for a few more months... 'cuz remember, you're buying tires eventually anyway. To really get ahead by stretching them out, you're not going to see any real benefit financially until you've gone through several purchase cycles. It's false economy.
07-13-2007, 11:18 AM
#29
nycebo, I hear you. I guess if I was going to do that, I wouldn't wait until there was wear on the tires. I'd treat it as tire rotation, and do it at regular intervals. Doing it when there's a lot of wear is still, IMHO, not worth it.
07-13-2007, 12:35 PM
#30
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Originally Posted by BruceP
nycebo, I hear you. I guess if I was going to do that, I wouldn't wait until there was wear on the tires. I'd treat it as tire rotation, and do it at regular intervals. Doing it when there's a lot of wear is still, IMHO, not worth it.