Tire Air Pressure
03-20-2014, 12:19 PM
#1
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Thread Starter
Tire Air Pressure
This may have been covered somewhere before but I cannot find it.
I have gone around and around with Michelin with this question and am currently trying to get a real technician to answer my question not just a customer service person replying with canned answers.
So here is my dilemma, I hope you can follow along better than the Michelin Customer Support.
The OEM tire for my and many C6 Corvettes are the Goodyear Run Flat tires and the door placard states they be filled to 30psi (On my C6).
OK, now the tricky part.
The tires on my C6 now are Michelin Pilot Sport A/S Plus tires, OEM Size set at OEM door placard air pressure.
Problem is they are wearing on the inside and outside edge which is indicative of under inflation.
My question to Michelin was this (And to anyone that can help).
Since the OEM tire is a Goodyear and a Run Flat and the psi is set at 30. And since the Michelin tire is the OEM size but NOT a Run Flat tire, should the Michelin tire have a higher tire pressure.
This is based on the fact run flats are less flexible and stiffer than a tire that is not a run flat so based on that it may need more pressure for proper wear.
As stated before, my Michelin tires are all set at 30psi as it says and all 4 have equal wear on the inside and outside edges only. It would seem about 4psi more would make it have the proper contact patch with the road and wear properly.
Can anyone help or has anyone else had this problem also?
Even if this has been covered, someone please help me out, Last thing I want is cords showing on the edges and 90% tread left in the center.
I have gone around and around with Michelin with this question and am currently trying to get a real technician to answer my question not just a customer service person replying with canned answers.
So here is my dilemma, I hope you can follow along better than the Michelin Customer Support.
The OEM tire for my and many C6 Corvettes are the Goodyear Run Flat tires and the door placard states they be filled to 30psi (On my C6).
OK, now the tricky part.
The tires on my C6 now are Michelin Pilot Sport A/S Plus tires, OEM Size set at OEM door placard air pressure.
Problem is they are wearing on the inside and outside edge which is indicative of under inflation.
My question to Michelin was this (And to anyone that can help).
Since the OEM tire is a Goodyear and a Run Flat and the psi is set at 30. And since the Michelin tire is the OEM size but NOT a Run Flat tire, should the Michelin tire have a higher tire pressure.
This is based on the fact run flats are less flexible and stiffer than a tire that is not a run flat so based on that it may need more pressure for proper wear.
As stated before, my Michelin tires are all set at 30psi as it says and all 4 have equal wear on the inside and outside edges only. It would seem about 4psi more would make it have the proper contact patch with the road and wear properly.
Can anyone help or has anyone else had this problem also?
Even if this has been covered, someone please help me out, Last thing I want is cords showing on the edges and 90% tread left in the center.
03-20-2014, 12:53 PM
#2
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St. Jude Donor '15
"In honor of jpee"
Since I can't imagine alignment, balance, or suspension issues causing all 4 to wear that way, I'll ask this: how are you setting the tire pressure and what time of day? Do you use a known, good, tire pressure gauge? Is it done first thing in the morning? When did you buy the tires and put them on the car, last month, six months ago?
I doubt if any Michelin technician is going to take on the legal responsibility of contradicting the door placard of your car esp. after Firestone/Explorer issue of a decade+ ago.
I doubt if any Michelin technician is going to take on the legal responsibility of contradicting the door placard of your car esp. after Firestone/Explorer issue of a decade+ ago.
Last edited by AORoads; 03-20-2014 at 12:55 PM.
03-20-2014, 01:29 PM
#3
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Thread Starter
I actually got a call from Michelin after several emails and you are correct, they swear it is the same. So they say the tire pressure for a Run Flat tire that has a stiffer carcass and design is the same as the tire pressure for a Non Run Flat tire with a less dense carcass simply by design. I find that impossible to believe. Are they taking the cooling effect the Corvette has for the brakes and tires when they did this. My tire temps on the front during a test was this. A regular tire and cooling duct stayed at 30psi while driving around. The other tire with the cooling duct taped up raised to 33psi. So maybe the cooling effect is keeping the tires from getting up to temp resulting in low pressure, I do not know.
To answer your questions: I check the tire pressure when the car and tires are cold, and have been sitting inside my garage for a few hours, time of day varies but usually I check it before I drive the car that day. (Example, go to bed, wake up, do whatever, decide to go somewhere, check and adjust pressure if needed, then drive car, return to garage).
The tire pressure gauge I use is a digital gauge I used when I used to road race motorcycle's so it is accurate to a 10th of a pound with an accuracy of .1, so a typical reading can be 30.6 psi.
Tires were manufactured July 2012 and were installed around July 2013.
I have an appointment for 4 wheel alignment tomorrow or check, whichever it needs. If no mechanical reason I may switch to nitrogen and put 34psi in them to see if it improves tire wear. I may mark them like I use to on my race bike and friends do on their drag and race tires to get a true idea of what area is in contact with the road. The chalk test does not lie, it is what it is so maybe that will help.
I am at a loss..
To answer your questions: I check the tire pressure when the car and tires are cold, and have been sitting inside my garage for a few hours, time of day varies but usually I check it before I drive the car that day. (Example, go to bed, wake up, do whatever, decide to go somewhere, check and adjust pressure if needed, then drive car, return to garage).
The tire pressure gauge I use is a digital gauge I used when I used to road race motorcycle's so it is accurate to a 10th of a pound with an accuracy of .1, so a typical reading can be 30.6 psi.
Tires were manufactured July 2012 and were installed around July 2013.
I have an appointment for 4 wheel alignment tomorrow or check, whichever it needs. If no mechanical reason I may switch to nitrogen and put 34psi in them to see if it improves tire wear. I may mark them like I use to on my race bike and friends do on their drag and race tires to get a true idea of what area is in contact with the road. The chalk test does not lie, it is what it is so maybe that will help.
I am at a loss..
03-20-2014, 01:46 PM
#4
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St. Jude Donor '14
Nitrogen at 30PSI. Your argument over the carcass stiffness having a bearing on PSI values is null- stiffness doesn't affect their recommended air volume capacity, it just provides more material in case it pops so you don't damage your rims.
If you run higher, you risk popping those expensive non run-flats.
As for the wear on the inside and outside edges- if it's on stock alignment you may want to get it altered. The stock alignment for the Corvette tends to be aggressive (although that's a mixed bag, some people get more aggressive results when they check their alignment than others). Here's an alignment setup you may want to consider, it should be easier on your tires for every day street driving but also leaves you some flexibility for the curves:
Front (min max)
Camber (deg) -1.1 -1.3
Caster (deg) 7.5 8.5
Total Toe -1/16" (0.17°) 0 (0°)
Rear (min max)
Camber (deg) -0.7 -0.9
Total Toe -1/8" (0.33°) -1/16" (0.17°)
If you run higher, you risk popping those expensive non run-flats.
As for the wear on the inside and outside edges- if it's on stock alignment you may want to get it altered. The stock alignment for the Corvette tends to be aggressive (although that's a mixed bag, some people get more aggressive results when they check their alignment than others). Here's an alignment setup you may want to consider, it should be easier on your tires for every day street driving but also leaves you some flexibility for the curves:
Front (min max)
Camber (deg) -1.1 -1.3
Caster (deg) 7.5 8.5
Total Toe -1/16" (0.17°) 0 (0°)
Rear (min max)
Camber (deg) -0.7 -0.9
Total Toe -1/8" (0.33°) -1/16" (0.17°)
03-20-2014, 02:10 PM
#5
Banned Scam/Spammer
Thread Starter
Nitrogen at 30PSI. Your argument over the carcass stiffness having a bearing on PSI values is null- stiffness doesn't affect their recommended air volume capacity, it just provides more material in case it pops so you don't damage your rims.
If you run higher, you risk popping those expensive non run-flats.
As for the wear on the inside and outside edges- if it's on stock alignment you may want to get it altered. The stock alignment for the Corvette tends to be aggressive (although that's a mixed bag, some people get more aggressive results when they check their alignment than others). Here's an alignment setup you may want to consider, it should be easier on your tires for every day street driving but also leaves you some flexibility for the curves:
Front (min max)
Camber (deg) -1.1 -1.3
Caster (deg) 7.5 8.5
Total Toe -1/16" (0.17°) 0 (0°)
Rear (min max)
Camber (deg) -0.7 -0.9
Total Toe -1/8" (0.33°) -1/16" (0.17°)
If you run higher, you risk popping those expensive non run-flats.
As for the wear on the inside and outside edges- if it's on stock alignment you may want to get it altered. The stock alignment for the Corvette tends to be aggressive (although that's a mixed bag, some people get more aggressive results when they check their alignment than others). Here's an alignment setup you may want to consider, it should be easier on your tires for every day street driving but also leaves you some flexibility for the curves:
Front (min max)
Camber (deg) -1.1 -1.3
Caster (deg) 7.5 8.5
Total Toe -1/16" (0.17°) 0 (0°)
Rear (min max)
Camber (deg) -0.7 -0.9
Total Toe -1/8" (0.33°) -1/16" (0.17°)
Unless I am blind you can see all 4 have inner and outer wear not flat as one would expect. Any thoughts on what I may be missing or what I did not notice, besides the gravel in the treads..lol
I am not an expert so I may not see the forest for the trees, any help appreciated.
Rick
03-20-2014, 02:32 PM
#6
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St. Jude Donor '15
"In honor of jpee"
I don't think an alignment change is going to do much to your wear pattern for the inner and outer edges of all four tires. I also don't know what the test was that you did w. the duct taped up, but my tire temps in warm weather (such as when you first put the tires on) go up as much as 5 lbs. I've not taped up anything.
I'd still suggest a tread depth gauge which, from your prior experience, you probably have in the toolbox. I'd check out what a new tire of same size has across the face, and compare it to what you have now. And I still would not increase it four pounds to start out with, but that's just me being a bit cautious.
I'd still suggest a tread depth gauge which, from your prior experience, you probably have in the toolbox. I'd check out what a new tire of same size has across the face, and compare it to what you have now. And I still would not increase it four pounds to start out with, but that's just me being a bit cautious.
03-20-2014, 02:52 PM
#7
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OP
Apology in advance if I have misread or misunderstood
You state the Michelin tires are Non RF, yet the pic you posted is a AS Plus which is a RF tire?
Also: how many miles are on these tires?
I just pulled a set of the AS Plus RF's off my car yesterday. They were worn similar. 35,000 miles on those tires, about all I could expect...
Apology in advance if I have misread or misunderstood
You state the Michelin tires are Non RF, yet the pic you posted is a AS Plus which is a RF tire?
Also: how many miles are on these tires?
I just pulled a set of the AS Plus RF's off my car yesterday. They were worn similar. 35,000 miles on those tires, about all I could expect...
03-20-2014, 03:22 PM
#8
Banned Scam/Spammer
Thread Starter
The Michelin Pilot Sport A/S Plus is not a Run Flat tire. The Michelin Pilot Sport A/S Plus ZP is a Run Flat tire but mine are NOT ZP, so no Run Flat, I double checked to make sure, I could have been wrong..lol
03-20-2014, 03:28 PM
#9
Banned Scam/Spammer
Thread Starter
I don't think an alignment change is going to do much to your wear pattern for the inner and outer edges of all four tires. I also don't know what the test was that you did w. the duct taped up, but my tire temps in warm weather (such as when you first put the tires on) go up as much as 5 lbs. I've not taped up anything.
I'd still suggest a tread depth gauge which, from your prior experience, you probably have in the toolbox. I'd check out what a new tire of same size has across the face, and compare it to what you have now. And I still would not increase it four pounds to start out with, but that's just me being a bit cautious.
I'd still suggest a tread depth gauge which, from your prior experience, you probably have in the toolbox. I'd check out what a new tire of same size has across the face, and compare it to what you have now. And I still would not increase it four pounds to start out with, but that's just me being a bit cautious.
What I did was tape up the opening in the front underneath the car so the air would not be pulled in and blow on the tire/brakes. The result was the one that was not covered the tire pressure stayed the same, the one taped up and not getting air from the duct raised about 3psi. Hope that helps explain it better.
Rick
By the way, thanks for all your help in your PM, very insightful.
03-20-2014, 03:28 PM
#10
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The pic you posted of the tires looks identical to the Run Flats I removed yesterday AS Plus ZP
Those tires also wore more on the inside/outside or so it appears. I just figured it was because the grooves/tread pattern is not as deep on the outside/inside as it is in the center.
Installed Non Run Flat Hankook Ventus V-12 Evos for around half what it would have cost to replace the Michelin.
03-20-2014, 06:30 PM
#11
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St. Jude Donor '13
I was told by a Michelin dealer that their A/S in C6 sizes, was never made in a non-runflat version. He said that both the A/S and A/S+ in C6 sizes, were all runflats.
AFAIK, Tire Rack has never shown a Michelin A/S in non-runflat C6 sizes.
But either way, that does not explain OP's unusual tire wear.
FWIW, the Michelin PS2 ZP runflats on our 2009 Z51 are also wearing the inner/outer edges a little more, not alarming but puzzling. And I keep my pressures up: 30 psi cold in the morning, before driving and before the day warms up. If anything, I'm running a pound or two higher than the official number.
Causes of inner (only) wear:
Too much negative camber
Toe-out in alignment
Causes of outer (only) wear:
Not enough negative camber for cornering forces.
Toe-in in alignment
I do run a fair amount of negative camber (-.8 and -.5, front/rear) and also a bit of toe-in. And i often corner hard. Perhaps my personal combination is the cause.
AFAIK, Tire Rack has never shown a Michelin A/S in non-runflat C6 sizes.
But either way, that does not explain OP's unusual tire wear.
FWIW, the Michelin PS2 ZP runflats on our 2009 Z51 are also wearing the inner/outer edges a little more, not alarming but puzzling. And I keep my pressures up: 30 psi cold in the morning, before driving and before the day warms up. If anything, I'm running a pound or two higher than the official number.
Causes of inner (only) wear:
Too much negative camber
Toe-out in alignment
Causes of outer (only) wear:
Not enough negative camber for cornering forces.
Toe-in in alignment
I do run a fair amount of negative camber (-.8 and -.5, front/rear) and also a bit of toe-in. And i often corner hard. Perhaps my personal combination is the cause.
03-20-2014, 10:37 PM
#12
Team Owner
I was also under the impression that the A/S Plus was not made in our sizes in a non runflat...but anyway...my A/S Plus runflats are wearing just the opposite. I have been running the cold pressures at about 34 and have just measured that the middle of all four is about 2/32nds more worn than the edges. So I have just lowered them to 31. I'm not complaining as I have 25,000 on them and they are still at about 50% tread, but I did find it interesting. By far the majority of miles on my tires are at 84mph on the highway
Michelin certainly does not make the tire in a non ZP in the C6 sizes currently.
Michelin certainly does not make the tire in a non ZP in the C6 sizes currently.
Last edited by cclive; 03-20-2014 at 10:42 PM.
03-21-2014, 09:48 AM
#13
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C6 of Year Finalist (performance mods) 2019
St. Jude Donor '11, '14
If you have a heat probe of any kind all u have to do is measure the center temp of the tire after driving. a perfect aligned tire will have the same same temp at the outside,middle and inside. The middle of course is adjusted my air pressure.
Robin
Robin
03-21-2014, 10:32 AM
#14
Race Director
http://forums.corvetteforum.com/c6-t...-readings.html
Some added reading.
Note that my tire wear initially recorded was with 30-31 HOT psi. Or 27 cold.
Pretty even tire wear and the same as experienced by Gearhead Jim. Jim's driving style seems to be like mine, and out alignements specs are similar. Same camber and I have -.05 toe both sides front and a little less in the rear -.02 and -.01. Jim doesn't give his toe numbers but I am assuming they are close. I tried zero toe and did not like the response at highway speeds.
As AORoads commented it could just be the nature of the car and how it is driven, being aggressive in the turns.
I went up three lbs cold and need to get out and check the tread depth. I am at the recommended 30 lbs cold now.
My point is even at 3-4 psi cooler than recommended psi my tread wear wasn't bad. Granted still early in the tire mileage wear. And things could of gotten worse but the tire were not showing tread scuffing on the edges.
Some added reading.
Note that my tire wear initially recorded was with 30-31 HOT psi. Or 27 cold.
Pretty even tire wear and the same as experienced by Gearhead Jim. Jim's driving style seems to be like mine, and out alignements specs are similar. Same camber and I have -.05 toe both sides front and a little less in the rear -.02 and -.01. Jim doesn't give his toe numbers but I am assuming they are close. I tried zero toe and did not like the response at highway speeds.
As AORoads commented it could just be the nature of the car and how it is driven, being aggressive in the turns.
I went up three lbs cold and need to get out and check the tread depth. I am at the recommended 30 lbs cold now.
My point is even at 3-4 psi cooler than recommended psi my tread wear wasn't bad. Granted still early in the tire mileage wear. And things could of gotten worse but the tire were not showing tread scuffing on the edges.
Last edited by Boomer111; 03-21-2014 at 11:13 AM.
03-21-2014, 11:23 AM
#15
Race Director
best thing to do is either paint a line or tape all the way across each tire take for a short ride and then adjust accordingly, then you have a starting point and then need to adjust for every 10 degrees in air temp change, the placard was designed for the tire and the weight of the car, I dont think the tire manufacturer can make a call on that since that tire will fit many cars with different weights
03-21-2014, 12:43 PM
#16
Banned Scam/Spammer
Thread Starter
*** TO THOSE ABOUT THE MICHELIN A/S PLUS BEING A RUN FLAT ***
After getting my C6 out side in the sun where I can see and with my reading glasses on I did see the ZP on the tire, so with that in mind, and I could not see well in my garage, and the Michelin Representative did not correct me that it is a Run Flat tire, I have this to say.
I sincerely apologize and you are all right I was wrong, I am sorry for not seeing that and for thinking some of you were wrong, again, I am sorry, you guys were right (Should not have doubted you in the first place) so I hope that if anyone took offense you will accept my apology.
Rick
GhostC6
After getting my C6 out side in the sun where I can see and with my reading glasses on I did see the ZP on the tire, so with that in mind, and I could not see well in my garage, and the Michelin Representative did not correct me that it is a Run Flat tire, I have this to say.
I sincerely apologize and you are all right I was wrong, I am sorry for not seeing that and for thinking some of you were wrong, again, I am sorry, you guys were right (Should not have doubted you in the first place) so I hope that if anyone took offense you will accept my apology.
Rick
GhostC6
03-21-2014, 12:46 PM
#17
Banned Scam/Spammer
Thread Starter
Now, looking at the photo, am I seeing correctly that the tires are indeed wearing on the outside edges. Or am I missing something, what do you guys see from the pictures.
Thanks in advance.
Rick
[/QUOTE]
Thanks in advance.
Rick
[/QUOTE]
03-21-2014, 12:50 PM
#18
Banned Scam/Spammer
Thread Starter
To all of you guys, please see my apology, I was wrong, I am sorry about that, I could not see the ZP in my garage due to the poor lighting.
I did not realize the tire was made in a Non RF version.
The pic you posted of the tires looks identical to the Run Flats I removed yesterday AS Plus ZP
Those tires also wore more on the inside/outside or so it appears. I just figured it was because the grooves/tread pattern is not as deep on the outside/inside as it is in the center.
Installed Non Run Flat Hankook Ventus V-12 Evos for around half what it would have cost to replace the Michelin.
The pic you posted of the tires looks identical to the Run Flats I removed yesterday AS Plus ZP
Those tires also wore more on the inside/outside or so it appears. I just figured it was because the grooves/tread pattern is not as deep on the outside/inside as it is in the center.
Installed Non Run Flat Hankook Ventus V-12 Evos for around half what it would have cost to replace the Michelin.
I did not realize the tire was made in a Non RF version.(dont see the Non Run Flat AS Plus on Tire Rack either, at least in 285/35 19...)
The pic you posted of the tires looks identical to the Run Flats I removed yesterday AS Plus ZP
Those tires also wore more on the inside/outside or so it appears. I just figured it was because the grooves/tread pattern is not as deep on the outside/inside as it is in the center.
Installed Non Run Flat Hankook Ventus V-12 Evos for around half what it would have cost to replace the Michelin.
The pic you posted of the tires looks identical to the Run Flats I removed yesterday AS Plus ZP
Those tires also wore more on the inside/outside or so it appears. I just figured it was because the grooves/tread pattern is not as deep on the outside/inside as it is in the center.
Installed Non Run Flat Hankook Ventus V-12 Evos for around half what it would have cost to replace the Michelin.
I was told by a Michelin dealer that their A/S in C6 sizes, was never made in a non-runflat version. He said that both the A/S and A/S+ in C6 sizes, were all runflats.
AFAIK, Tire Rack has never shown a Michelin A/S in non-runflat C6 sizes.
But either way, that does not explain OP's unusual tire wear.
FWIW, the Michelin PS2 ZP runflats on our 2009 Z51 are also wearing the inner/outer edges a little more, not alarming but puzzling. And I keep my pressures up: 30 psi cold in the morning, before driving and before the day warms up. If anything, I'm running a pound or two higher than the official number.
Causes of inner (only) wear:
Too much negative camber
Toe-out in alignment
Causes of outer (only) wear:
Not enough negative camber for cornering forces.
Toe-in in alignment
I do run a fair amount of negative camber (-.8 and -.5, front/rear) and also a bit of toe-in. And i often corner hard. Perhaps my personal combination is the cause.
AFAIK, Tire Rack has never shown a Michelin A/S in non-runflat C6 sizes.
But either way, that does not explain OP's unusual tire wear.
FWIW, the Michelin PS2 ZP runflats on our 2009 Z51 are also wearing the inner/outer edges a little more, not alarming but puzzling. And I keep my pressures up: 30 psi cold in the morning, before driving and before the day warms up. If anything, I'm running a pound or two higher than the official number.
Causes of inner (only) wear:
Too much negative camber
Toe-out in alignment
Causes of outer (only) wear:
Not enough negative camber for cornering forces.
Toe-in in alignment
I do run a fair amount of negative camber (-.8 and -.5, front/rear) and also a bit of toe-in. And i often corner hard. Perhaps my personal combination is the cause.
I was also under the impression that the A/S Plus was not made in our sizes in a non runflat...but anyway...my A/S Plus runflats are wearing just the opposite. I have been running the cold pressures at about 34 and have just measured that the middle of all four is about 2/32nds more worn than the edges. So I have just lowered them to 31. I'm not complaining as I have 25,000 on them and they are still at about 50% tread, but I did find it interesting. By far the majority of miles on my tires are at 84mph on the highway
Michelin certainly does not make the tire in a non ZP in the C6 sizes currently.
Michelin certainly does not make the tire in a non ZP in the C6 sizes currently.
OP
Apology in advance if I have misread or misunderstood
You state the Michelin tires are Non RF, yet the pic you posted is a AS Plus which is a RF tire?
Also: how many miles are on these tires?
I just pulled a set of the AS Plus RF's off my car yesterday. They were worn similar. 35,000 miles on those tires, about all I could expect...
Apology in advance if I have misread or misunderstood
You state the Michelin tires are Non RF, yet the pic you posted is a AS Plus which is a RF tire?
Also: how many miles are on these tires?
I just pulled a set of the AS Plus RF's off my car yesterday. They were worn similar. 35,000 miles on those tires, about all I could expect...
03-21-2014, 02:21 PM
#20
Team Owner
Are you actually measuring the tread depth with a gauge, or are you doing it visually? My A/S Plus tires look deeper in the middle but with a gauge, they are actually deeper at the outside of the tread.