Tire wear experament

[awdjdmtalon]

Ok I put new tires on my G last night. And as we all know, they like to wear the centers out of the rear tires. I think this is for several reasons. 1 is the tire is too wide for thewheel making the tire buldge in the center. 2 Is the tire pressure being to high for #1.

So what I have done is this.

1. Filled the rear tires to 32 psi.

2. Filled them w/ nitrogen. This will eliminate tire pressure fluctuation due to temprature.

3. Measured the tread depth in 3 location. 1 the outer rib, 2 in the center and 3 on the inner rib.

I am going to drive 200 miles and recheck pressure to make sure it is constant, and tread depth.

If the tire is wearing in the center, lower pressure 1 psi and repeat.

If the outer edges have worn more then the center, raise pressure 1 psi and repeat.

Keep doing this until I reach a pressure where the tires are not wearing either spot unevenly.

Now for the hard part. Trying to drive the car nicely for this experament.
Modified by awdjdmtalon at 10:40 AM 9/19/2008

[G_whizz]

Done

[awdjdmtalon]

Ok after 263 miles of driving I have rechecked tread depth.

I am happy to report, that w/ 32 psi in the rear tires, the wear is none. Both rears are still 10/32 all the way across. Also the tires still have a bit of the "tits" still on them.

I am going to recheck at 500 miles and update. Leaving rear tire pressure at 32 psi.

(G-whizz) will you please update the title w/ todays date.

ThanksJerry

[C-Kwik]

1 is the tire is too wide for thewheel making the tire buldge in the center. 2 Is the tire pressure being to high for #1.

#1 has been what I've speculated for some time.

#2 is unlikely to remedy the problem. I've heard of guys going down to 28 psi and still having the issue. Dropping down a size or two in width may be the only solution with the factory 18's. You probably won't see any observable difference in treadwear with a standard depth gauge for at least a couple of thousand miles anyways.

Also, dropping the tire pressure tends to reduce the tires load capacity. Not only can it become dangerous (if you drop it too low), but it can also negatively affect the handling performance. Higher load ratings from a tire tend to reduce slip angles necessary to provide a certain amount of lateral load. Rear tires on any car are already at a disadvantage in slip angles as it is. I'd hate to add the need for more...

[awdjdmtalon]

Well I got the idea from a retiredMechanical Engenieer. He did the same thing on his Mustang GT. He was having the exact same problem, and did what I am doing. I forget what he found to be the tire press. that he got even wear out of.

And I understand load rating of the tires. The car manuf. does test to figure out the best TP for ride/comfort first and formost. Handleing comes somewhere down the line.

I'm not trying to get into a debate w/ anyone on this. This is something I am doing, and if it helps others then good. If not interested in this, then please bypass.

[C-Kwik]

And I understand load rating of the tires. The car manuf. does test to figure out the best TP for ride/comfort first and formost. Handleing comes somewhere down the line.

Note that I mentioned the aspect of danger first. An aired down tire is subject to more heat. This is especially significant in a performance car as high speeds will push the tread out, but the weight of the vehicle will flex the tread back in as it rolls over the ground. Sufficient tire pressure is necessary to reduce tire flex. While the jury is still out on it, the Firestone-Ford Explorer tire recall should be something to consider. While the tire may have been defective or at least less durable than comparable tires, Ford recommeded a 26 psi pressure for the tire. That was an expensive recall and I'd imagine every manufacturer has taken it into consideration to some extent. In the case of Nissan, I haven't heard of any that don't recommend 35 psi.

I'm not trying to get into a debate w/ anyone on this. This is something I am doing, and if it helps others then good. If not interested in this, then please bypass.

I don't mind the aspect of trying to help everyone else out. But it doesn't mean I should let it be published without alerting members to the possible downsides. And I have seen plenty of discussions about this issue including results from those who aired down to about 28 psi (just over the TPMS threshold). Their results were that the lower tire pressure had no significant benefit in terms of tire wear. I offered that in case you might find it helpful that others have already tried something similar.

[awdjdmtalon]

I understand the safety aspect of under infated tires. 3 psi is not going to make the tire unsafe. There are thousands of cars on the road daily that have tires that are underinflated by as much as 10 psi. I know this b/c I am a Master VW tech and a Master ASE tech, and I see it daily.

As for the Ford/Firestone thing. I worked for Firestone for a few yrs. And yes the tires failed due to heat from under inflation. But this was not due to a defect in the tire.

Ford specified that Firestone build a tire for them, to operate under certin conditions and at a set psi. And Firestone produced that tire for Ford. But when Ford put the Vechicles in question into production, they changed the psi requirement for the vech. to a much lower then what they originally specified.

Firestone warned Ford that the tire was not designed for the "new" tire pressure that was now on the vech. But Ford ignored the warnings and left the tire pressures set to the now MUCH LOWER rating then what was originally specified.

So then the vech.s were on the road w/ and under inflated tire. And careless drivers who are too lazy and most are to check the pressures. So over time the tires failed, due to gross under inflation.

Now if I was doing this at grossly under inflated pressures, I could see the concern. But I am not. And I am going to continue to check the tires as I stated. If I see any wear issues do to this, I will report it as such, and adjust tire pressures to correct it.

As for the "plenty of discussions" on this, please post the links. I would be more then happy to review them.

I there is much more of this debate on the subject, I will just have the mods lock/delete this thread. And then noone will get any benifit out of this.

[SteveTheTech]

I really like the idea of a professional review of actual observed conditions over a long period of time and I look forward to Jerry's updates.

I have seen different results with different tires, the factory Michelins wear like crap and always in the center. There are some Dunlops that wear evenly, I will check Tirerack in the morning and update this with what I have seen.

[awdjdmtalon]

Thanks Steve. i will continue to check and report. I hate that I have to throw out my credentials, to get people to stop the debates.

As for the tires. I am running the Nitto NT 555's. I drove the car over 200 miles yesterday to GT Live. I doubt there was any wear. It was all highway miles. But I will check tomorrow when I get the car back to the shop.

[SteveTheTech]

I know what you mean sometimes people here do not take what you say seriously, it's one of my main reasons for joining. The misinformation that is rampant on some of these forums is frustrating, for the most part NICO is one of the sanest sometimes. The professional non biased opinion is what we really need more of here, we have enough speculation.

I really like the 555s they seems to wear well and have good performance characteristics.

[C-Kwik]

I there is much more of this debate on the subject, I will just have the mods lock/delete this thread. And then noone will get any benifit out of this.

Look. You can do it if you want. Post the results. That's great. I'm not slamming your idea. What I am doing is providing balance for the discussion and the results (when they come in). Other members may use your results in their decisions in regards to tire pressure. But there ARE negative drawbacks with regards to lowering pressure. So the last thing I want to see is that someone makes a decision based on only one aspect.

As for the Ford/Firestone thing, I'd love to see the info you speak of. From my research it seems there were problems on both sides that contributed to the tread separation. Tire pressure was one of them. According to Time magazine, Firestone was aware that Ford was going to lower its tire pressure:

"Ford's decision to increase the stability of the Explorer by lowering the tire pressure soon had unintended consequences. The mushier tires held the road better but worsened fuel economy. When Ford asked Firestone to fix the problem, Firestone reduced the weight of the tire about 3%."

http://www.time.com/time/busin....html

I'd speculate that they went along with it for fear of losing a contract to supply the tires for a high volume SUV. I'd imagine there was a lot of corporate politics involved leading up to it and in the investigation that followed. Unless you were actually an engineer or executive at Firestone, I doubt you truly know what happened. I certainly don't claim to.

However, my point was that the lower pressures appeared to have a lot to do with it and that the tires used were not going to be universally safe to run at those pressures, especially at higher speeds. Something that should definitely be considered as I'd imagine many people who own G's aren't the ones adhering to the speed limit.

I understand the safety aspect of under infated tires. 3 psi is not going to make the tire unsafe. There are thousands of cars on the road daily that have tires that are underinflated by as much as 10 psi. I know this b/c I am a Master VW tech and a Master ASE tech, and I see it daily.

I don't disagree that many tires are underinflated. That's not exactly a secret. And certainly tires do not simply blow out the moment it becomes underinflated. There are a great many factors that go into it. And while your tire may hold, what if everyone here follows your results and lowers their pressure? What if as a result the conditions created by this for one of our members causes a blow out and perhaps a death or injury? I have no problem with your research here. But I will interject when I feel it is appropriate and necessary. Think of what I say as a disclaimer...

As for the "plenty of discussions" on this, please post the links. I would be more then happy to review them.

Unfortunately, any info I've seen in regards to this was on a different forum more than 2 years ago when I had my G35 Coupe. So it might be difficult to source and at that I can't post them here anyways (even I have to follow the rules). Otherwise I'd be happy to share.

[C-Kwik]

I have seen different results with different tires, the factory Michelins wear like crap and always in the center. There are some Dunlops that wear evenly, I will check Tirerack in the morning and update this with what I have seen.

Bridgestone SO3's didn't hold up any better to the center tread wearing out. Both the Original Michelins and the SO3's lasted about the same mileage. I sold my G before I could notice any observable wear on some RE040's that replaced the SO3's.

[SteveTheTech]

I like the REO40s and the 50s the 50s are standard on the 37 now. They seem alright so far.

[awdjdmtalon]

C-Kwik. Thank you. You are correct about having balance for the discussion and the results.

I understand the safety issues you bring up.

I am doing this for the ones out there you are looking to get he most out of thier very expensive tire purchaces. This is all about tire wear for longevity, and not for better performance. I should have made that clear from the get go.

When I plan on hitting the BlueRidge Parkway in a few weeks for some spirited driving, I may or not adjust the tires to 35 psi. It will depend on how the car feels in the next few weeks as I get used to the new tires.

Just as a side note on pressures. The Toyo RA1's that I used for autocross on my GTI, got the best grip at 16 psi front and 14 psi rear. These are a DOT tire w/ a tread wear rating of 20. Granted the speeds rarely got over 65 mph and the tires were "in use" for no more then 1m 45 sec. tops.

I also used the S03's on my AWT Talon street/drag car. They wore even. But they were a 225/50/16 on an 8 " wheel. And I only got about 10k miles out of them.

As for the Firestone tires and Ford. I got the info from a Tire safety training class given by the Regional Manager for the area I lived in. And you are correct about Firestone taking some of the heat for it, to save a multi billion dollar account. It is ALL about politics.

Now lets get back to checking tread depths.

[ldstang50]

As someone who is about to purchase an 07 350z, I look forward to your updates Jerry.

[C-Kwik]

As someone who is about to purchase an 07 350z, I look forward to your updates Jerry.

I don't think you have as much to worry about with an 07 350Z. The standard wheels used are 18x8 front and 18x8.5 rear, but use the same tires as the 18" packages from 03-05. I have not heard of any widespread complaints about the 06+ 18's having any rear tire center treadwear issues. The issues I hear about seem to be with the 245/45's mounted on an 18x8 inch wheel.

[ldstang50]

I don't think you have as much to worry about with an 07 350Z. The standard wheels used are 18x8 front and 18x8.5 rear, but use the same tires as the 18" packages from 03-05. I have not heard of any widespread complaints about the 06+ 18's having any rear tire center treadwear issues. The issues I hear about seem to be with the 245/45's mounted on an 18x8 inch wheel.

C-KwikYou're right I shouldn't have any wear issues.... but I'll be running the 18x9 up front and 19x10 in the rear, I have the Nismo edition. The 245 should have no center wear issues being mounted on a 9" wheel nor should the 265's on a 10".

I do like how Jerry is using nitrogen instead of regular air. Thats a VERY smart move for this test as the pressures will stay more constant over temperature changes.

[C-Kwik]

I do like how Jerry is using nitrogen instead of regular air. Thats a VERY smart move for this test as the pressures will stay more constant over temperature changes.

It should be noted that as the temperature of the tire increases, the pressure will still increase. Nitrogen filled tires will do so by less though, not because of the element itself, but because the processed air will contain less water vapor. Vapor pressure from water can add a significant amount of pressure with increased temperature over that of an ideal gas by itself. In theory, any ideal gas would be fine. Nitrogen simply is the logical choice due to its abundance and because it is inert (the next most abundant gas is Oxygen, but that's reactive).

Not trying to debate. But your statement could be misunderstood as Nitrogen's pressure doesn't change with temperature. Just clarifying.

[awdjdmtalon]

Kwik. You are right. Nitrogen tires still change slightly as temps increase, but it is FAR less then what "air" tires do. Also the nitrogen molicues (sp) are larger then O2, and are less reactive. SO change is size far less then a tire w/ a highr O2 saturation.

Just some background on ldstang. He has been racing cars for longer then I have know him. (4.5+ yrs now, that I have known him). From road racing at Lime Rock to autocross. In both a Mustang and an EVO. Soon to be doing it in a Nismo 350. Plus numerous track days on sport bikes. So I know he has had his fair share of experience w/ tire reactions w/ nitorgen vs. air tires.

[C-Kwik]

Kwik. You are right. Nitrogen tires still change slightly as temps increase, but it is FAR less then what "air" tires do. Also the nitrogen molicues (sp) are larger then O2, and are less reactive. SO change is size far less then a tire w/ a highr O2 saturation.

The "larger molecules" argument for N2 only applies to the loss of pressure over time aspect of a tire. But they still do leak over time, but at a slower rate. Its a big plus, but I'm not sure its worth the money (for most street driven cars). O2 is more reactive than N2, however, it is negligible in this application for 2 reasons:

1. The tires were built and designed with air in mind so the amount of oxidation is negligible.

2. The outside of the tire will oxidate anyways as it will be subject to atmospheric air anyways.

In both instances, the tire will likely be replaced before any significant amount of oxidation occurs.

As I stated, I am merely pointing out that the molecules of Nitrogen are not responsible for the more stable pressures. The ideal gas law, PV = nRT, ignores molecule size altogether. In theory, for a given pressure, volume and temperature, the number of moles (which reflects directly on the number of molecules; 1 mole = 6.022 x 10^23 molecules) remains the same regardless of which gas you use. So the size of the molecules make no difference in the pressure of the gas inside your tire as there will be the same number of molcules of any gas at a given temperature, volume, and pressure.

The problem is when you take atmospheric air and compress it, some of the moisture in the air may condense out of it. This means that depending on the humidity at the time of the fill, you may actually have liquid water in your tires. Until the liquid is completely turned into a vapor, it will add its own vapor pressure to the tire. How much will depend on both pressure and temperature. Once you vaporize the liquid completely, it will follow the ideal gas law as well. I don't know what the actual typical water content is in a tire, nor how likely it is that a typical air fill will completely vaporize any water content in a tire. In either case, predicting the hot pressure for a tire becomes much more difficult with water in it.

For this test, I would also encourage the use of N2, but as I stated before, my intent was to keep from misleading people as to why N2 fills are good. Sorry if this got overly technical. Just felt it was needed to make sure it is better understood.

[ldstang50]

I'm too new on here to be throwing around assumptions of people. We do appreciate the indepth analysis of using Nitrogen vs plain air to fill up your tires. I didn't know the exact reason (moisture in the air) but I did now that Nitrogen is less susceptible to pressure changes than compressed air. Jerry obviously knows this and thus is using Nitrogen for this experiment.

I think for the sake of this article, this is overly technical. My guess many of the people on here won't understand what you are talking about and still walk away with Nitrogen filled tires don't lose pressure as much as air filled tires.

I consider myself lucky to understand you and the chemistry of the inert gass law. But thats way beyond what anyone one here besides a chemistry major or someone taking chemistry right now could understand.

Being that this test will probably last a while, and knowing that Nitrogen will not escape as fast as air because its a larger molecule minimizes the error in the end result because it eliminates one possibly flaw in the data taking. Also the fact that it will change pressures less drastically than air is important because this will eliminate the 'bulge' in the center of the tread of an over inflated tires that causes the center tread to wear out faster than the outter treads. And I believe finding the proper tire pressure to run is the point of this thread, correct me if I'm wrong. Running Nitrogen and eliminating the expansion do to pressure will eliminate that possibility.

I do appreciate the insight of water vapor in a tire thus causing your pressure changes. That I didn't know and explains perfectly why Nitrogen is used in race cars and not air.

[C-Kwik]

Admittedly, it probably was more technical than most people care about. But the beauty of a forum is that people can take what they want out of it.

And BTW, welcome. I don't really pay attention to post counts so I didn't realize you weren't here for very long.

Lastly, I hope I don't come across as overbearing in this thread. The topic actually interests me quite a bit as I've been speculating about the tire/wheel width match up for sometime (hence my heavy involvement in this thread). Any quantitative data that suggests tire pressure isn't the cause would further support my own theory. Of course, in the end, I could also be proven wrong.

[awdjdmtalon]

Well I did an update at 250ish miles w/o any tread depth change. By next weekend, I should have 1000 miles on the tires and will check again and report.

This is going to be a very ongoing thread. I'm glad there is intreset in it. I can tell by the ones actively involved have some knowldege on the subject. This will make the final result worth the wait.

And I have been behaving w. the new tires. I'm trying hard not to alter the results due to agressive driving. It does however make for a boring ride to work everyday.

[ldstang50]

I think for most people who have very little knowledge probably thought it was too technical. But IMO, people that are actively involved with their cars and think of them more than just image in transportation really appreciate what you brought up. I know I did, although I did have to dig through some old chemistry notes to make sure I understood what was being said.

Thanks for the welcome. I find the Infinity guys to be more knowledgeable and more more mature than the 350z guys.

As is understood, I'm new here, I still don't even have my 350z yet. But the tire wear is fascinating to me. When I think of center tire wear, I think of over inflation, as do probably many more people. I would never think a manufacturer would mount an inappropriate sized tire.

Jerry I think what you should do is drive the car a little more aggresively. If you are just putting around back and forth to work, I don't think you are going to see the wear. I think you should do your putting around, but also every so often (once a week) take her out for a good aggresive drive in the mountains. Unless of course you forgot how to turn the wheel after all those years of drag racing the Talon

[C-Kwik]

I would never think a manufacturer would mount an inappropriate sized tire.

I'm not sure I classify it as inappropriate. It is still a safe size for the wheel and the actual tire life is still on par with tires that are generally considered a better match for the wheel. I got 12-15,000 miles depending on which set. The previous car before the G was a turbo 240sx which ran summer tires as well and I usually got 12-15,000 miles on those as well. My driving style didn't change between the two cars. So to be honest, I was perfectly content with the tire match.

[Sentientbydesign]

You guys can't just leave someone to do some testing can you?

Just chiming in to report that I bought my G with rear center balding on the RE050As.

[awdjdmtalon]

Well I have gone a little over 1100 miles now. And I was actually planning on not updating. There seemed to be no intrest in what I was doing, other then telling me I was wrong and creating an unsafe situation, and could harm others if they followed what I was doing.

But now that SBD has chimed in and has the same Issue w/ the 19" wheels, I will update as soon as i measure the tires.

[Sentientbydesign]

Thanks Jerry. Chano seemed to miss the point of this thread or just thought a thesis-sized disclaimer/debate was necessary. He must have just come from the Politics forum when he decided to reply to this

[awdjdmtalon]

UPDATE

After just over 1100 miles I remeasured the tread depths. I had originally set them at 32psi but kept getting a TPM light on very cold mornings. So I bumped them to 33psi. I think that was at about 200 miles.

I checked then today. Both tires has the same wear.(this is the rear tiers only)

outer middle inner9/32 10/32 9/32

Buy this wear I can tell that the tires are underinflated. So I bupmed the pressure 1psi to a total of 34psi. When I added the 1 psi I used nitorgen, to keep eveything the same. I also cheked the nitogen % of the tires. They are 98.2% nitorgen. This is about as much as you can get it to be.

The tires origanally started life at 10/32.I will recheck again after another 1000 miles.

[C-Kwik]

Thanks Jerry. Chano seemed to miss the point of this thread or just thought a thesis-sized disclaimer/debate was necessary. He must have just come from the Politics forum when he decided to reply to this

Don't be mad because you lost the debate.

My last research paper was some 18 pages long (the paper minimum was 5 pages). And I'd contend my longest posts are technical in nature. Try poking around in my old KA-T posts. Interestingly enough, I hate writing. Unfortunately, my compulsion to try and write my points clearly outweigh my hatred for writing.