Tires, tires, tires

Mr_Shiftright

And NOW Shell Oil is putting nitrogen in my gasoline. There must be a lot of surplus nitrogen in the world. Everyone's pushing it. :P

What's next? A nitrogen bomb?

texases

"What's next? A nitrogen bomb?"

Well, TNT = tri-NITRO-toluene....

jeffyscott

NITROglycerin...the active ingredient in dynamite.

Sandman6472

So, what's the bottom line here...which is better? Have used both and found no difference, but hey, I'm no expert...so what's the answer folks?

The Sandman :sick: :shades:

ruking1

For as much as you drive and the seasons: AIR and check your tire pressure monthly if you are more fastidious about these things. I have run as long as 1 quarter (3 months) between checking.

The caveat is I run my TP @ 85% of max side wall pressures if 44 psi then 38 psi, if 51 psi then 44/43 psi. Given the monthly loss is 1 psi, three months should lose app -3 psi. I have gotten 112,300 miles on a set of tires doing this.

Sandman6472

What you wrote sounds great, but I usually keep 35psi in my Civic. So I'll assume air is the way to go over nitrogen. Thanks.

The Sandman :sick: :shades:

ruking1

On my Civic (04) the owners manual lists 35 psi as the "highway" psi. I only got 74,500 miles on the oem "Dunlops" (S rated). I have a set of Toyo's (T rated) with 40.5k miles. I swag it will exceed 100k. MPG ranges between 38-42 mpg.

capriracer

Bottomline?

Nitrogen inflation has a very small advantage. It causes no bad things, but what it does has been greatly exaggerated. I

If you can get it free, GREAT! If you have to pay for it, the cost benefit ratio just isn't there. You'd be much further ahead to check your tires regularly and fill with air when needed.

And about inflation pressure: Do NOT use the sidewall pressure for anything other than what it says - the maximum. And certainly don't use it for a referencing point to figure out what pressure you should use. I cover that in more detail here:

http://www.barrystiretech.com/loadtables.html

If you don't know what to use, use the pressure on the placard - if you are using the same size listed there..

ruking1

Well think your last paragraph really does not change the fact that whatever psi is recommended, it is still a % of that maximum. Indeed one should probably NOT exceed the maximum. So for example 35 psi recommended on the Civic "highway psi " is 79.5% on a 44 psi max side wall tire (and 68.6% on a 51 psi side wall tire) 44 psi tires come standard on this vehicle.

jeffyscott

Never heard of XL for "extra load" before. How does that relate to the normal 2 digit load index?

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35

Last time I was buying tires, tire rack listed some with an 89 load index and some with 91, I did not think it was a big deal, but did have some preference for getting the higher load rating. The OEM tires also had the higher load rating of 91.

capriracer

Extra Load (XL) tires are passenger car tires that can carry more load than Standard Load (SL) tires of the same "size", and do that by using higher inflation pressures.

Load Indices are a way of simplifying the way load carrying capacity is stated. So XL tires will have about 3 units higher LI's than SL. The other way to tell if a passenger car tire is an XL is if they use those letters. You can also tell by the maximum inflation pressure - although that is not consistent!

SL's will have a maximum inflation pressure of 35, 44, or 51 psi.

XL's will have a maximum inflation pressure of 41, 50, or 51 psi.

So if the sidewall of a passenger car tire says 35, or 44 psi, you can be sure it is an SL. If it says 41 or 50, you can be sure it is an XL. But if it says 51 psi, you can not be sure.

And here's where is gets tricky: Different tire standardizing organizations have slightly different takes on how to express the maximum load carrying capacity - not to mention there are slight differences between using the English system and the metric system. As a result, you'll find slight differences in LI's between essentially the same load carrying capacity.

And to further complicate matters: You should NEVER use an SL in place of an XL, but you can use an XL in place of an SL (at the same inflation pressure).

That's why you should never base your inflation pressure on what is written on the sidewall of a tire - too many variables.

ruking1

Another obvious thing in addition to a percentage is that you can only put ONE PSI reading. Another is some oems recommend a different reading for the front and rears. So while all these variables exist and seems to be rocket science it is ... not.

Indeed I have one that the oem tires come with either 44 psi or 51 psi max side wall tires. To boot there are half load readings fronts, rear readings and "load" readings , fronts higher still and rears higher still.

jeffyscott

I never noticed before that tire rack does show many tires with "Load Range: XL". For my car (2007 Mazda6 with 215/50R17 tires) the list of acceptable tires that come up at tire rack includes tires with load index 90, 91, 93, and 95. Those with 93 or 95 are have the XL designation.

The OEM tires are load index 93 and max pressure 41, so they are XL. Yet tire rack is saying I can use SL by including the 90 and 91 load index tires.

Given that the manufacturer put load index 93 tires on it, I'd be inclined to get the same or higher when I replace them. But, even the 90 load index tires would allow me to load over 2000 pounds into my ~3000 pound car, which seems like far more that would be possible anyway. Is there any advantage or disadvantage to the 93 or 95 load index XL tires over the 90 or 91 SL tires?

mz6greyghost

Is there any advantage or disadvantage to the 93 or 95 load index XL tires over the 90 or 91 SL tires?

I've always believed in "the higher the better" in terms of Load Index, and never paid too much attention to the SL or XL designation.

And just to let you know: The Mazda6 had 16" OEM tires that were rated 91. So despite the 93 rating on the 17" tires, I've always been under the impression that a 91 or higher rating would work no matter what size or model the 6 has, and most industry "insiders" agree with it.

Despite that, the winter tires and replacement 3-season tires I used were rated 93 and 95, respectively.

crkyolfrt

XL tires may have greater carrying capacity, but I wonder if the extra steel and rubber weave that gives them the extra capacity also might create a greater rolling resistance and weigh more? Which would affect fuel economy. I would ask before just making assumptions that it is a win-win if you don't really need XL rubber.

ruking1

Indeed to add this in unless you are talking SUV, etc tires might be a tad confusing. So for example I have a 91 H rated tire on a VW Jetta TDI (1356 #'s) . So the 91 load rating is pretty easy to put in context. H rating means up to 130 mph. http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35&

Indeed my oem (VW)has really come up (way closer) to what I have been putting in my tires all along , aka 85% to 79% of max tire wall pressure. 35 psi. I had been putting 38 to 34 psi, when the oem recommended 26 psi. Now my tires are now 51 psi and I put in 44/43 for starters and it is good to go. Now because I have had some history, the longer term experiment is to pass 112,300 miles on the LOWEST psi. I have determined that to be 39 psi on a 51 psi tire or 34 psi on a 44 psi tire.

On SUV's we have had for up to 17 years, basically time worn setting has been 32 psi/44 psi or 73%.

capriracer

I am not sure why Mazda chose use use XL tires, but they did - and you apparently have found the exception to the rule concerning XL and SL's

(I told you this was complicated!)

capriracer

"........create a greater rolling resistance and weigh more?....."

Yes, XL tires will weigh more and have a bit greater RR, but the difference is not enough to worry about.

slorenzen

I have a retired neighbor, bought a Silverado 4x4 in '99, and still has his original tires on there(approx. 40k miles now).

i've been warning him for years about the age of his tires, but he just smiles and says he can't see any cracking on the sidewalls(I can't either, BTW).

how do you convince a guy like this?

jeffyscott

I assume you meant all else being equal the XL tires weigh more?

For my car, a tire I am considering, the continental extreme contact DWS, size 215/50ZR17 95W XL weighs 21 pounds. Looking through a few other tires I see some non XL, lower load category tires, that weigh more, eg. Fuzion HRi in size 215/50R17 91H SL weighs 25 pounds.

Also one tire for my car, Michelin Primacy MXV4, comes in both SL and XL. According to tire rack the XL weighs 1 pound less than the SL version.

I have been somewhat surprised to find that tire weight range for the same size tire is as much as it is. I've seen about at least a 5 pound difference from the lightest to heaviest.

ruking1

So to me what I get is go with what the oem owners manual prescibes. If you want to do a more custom application then its really up to the owner/user. The question still remains what are the statistical significances and tie ins?

crkyolfrt

Yes, you find huge weight differences when buying sport/race rubber for a bike. And because the bike weight is low, unsprung weight savings can impact handling a lot. So the lighter the rims and tires, the better able the suspension can do its job. The principle is the same for cars of course, but the weight dif being so much greater tire weight becomes more masked.

Mr_Shiftright

You don't convince him---the laws of physics and chemistry convince him--well, hopefully not.

capriracer

"....How do you convince a guy like this? "

In a word you probably can't. But I am not a defeatist, so I think you should try.

You might try convincing him that every tire manufacturer has issued bulletins stating that tires age and the age limit is always stated at less than 10 years.

You could also point out that the Ford/Firestone situation a few years ago was somewhat about rubber that was aging prematurely in hot climates. The tires were failing in as little as 3 years - and while his tires probably didn't have the exact problems the Firestone tires did, his are from the same era and have some of the same problems found in the subsequent 10 years - and corrected in newly designed tires.

Plus, when tires fail, they fail in the same manner as the Firestones did, and many people were killed as a result. The warning signs of impending failure are subtle and easily missed unless you know what to look for - a vibration that gradually gets worse over the course of several hundred miles – towards the end, there may be a bulge in the tread.

The fact the tires do not have cracking is not an indication that there is no problem – it’s the reverse that is true – that tires WITH cracks have problems.

Hope this helps.

capriracer

“……I assume you meant all else being equal the XL tires weigh more?.....”

Yes.

There are a lot of reasons why there may be large differences in the weight of tires of the same size – and a lot of those reasons have very little to do with quality, performance, and other things that we might find important. In my opinion, you should ignore weight in a passenger car tire.

jeffyscott

I've tended to be biased toward the lighter weight tires (or perhaps I should say biased toward tires that about the same weight as OEM tires) as I don't think that adding an extra 5 pounds of unsprung weight is a positive. Had not seen this before, but found this article by tire rack about effects of wheel weight:

http://www.tirerack.com/wheels/tech/techpage.jsp?techid=108

ruking1

It would also seem to me that an even more useful comparison would be the addition of oem SIZED wheels, but lighter (still), aka FORGED. For the 3 example tires (Michelin MVX4 Primacy 16,17,18,) it would seem that the forged 16 in and 16 in would be the lightest combination. Ergo I would swag the best mpg combination.

jeffyscott

Yes, their comparison between the light and heavy 17 inch wheels with the same tires is useful it terms of seeing the effect of differences due to wheel and tire weight. But not so much comparing both of those to the OEM 16 inch wheels with different tires.

I was more interested in the comparison of the ride and handling than the mpg difference, though.

ruking1

Right because the marketing move is to +1in, +2 in sizing. In almost every single comparison I have seen, the ride suffers. One part of the range of feelings/responses of others that experience this, seem to put it in terms of liking the better "feeling" ????I see it more like bone rattling and teeth chattering., and for what reason/s?????

Tire rack does do an article to where they say there are optimums. Of course the customer has to chose the compromises willing to be lived with. However ride mpg and handling are all compromised (other factors also).

jeffyscott

I agree that for me some of the large wheel sizes and very low profile tires go too far. I do like better handling but pretty sure I would not go lower than about a "50" series tire (which is what I have, with 17 inch wheels). 20 inch wheels with rubber band tires are not for me.

Though the coolness is certainly difficult to deny

imidazol97

I'm sure the owner needs nitrogen for those tires! (Just a joke, not a dig at anything.)

How do they spin balance them?

Please, let cars go back to having 60, 65, 70 series tires by the time I have to buy another one.

texases

I agree, 50 series are the lowest I'll go. I have two cars with them now, no problems. Go below that and the dented rims/damaged tire problems seem to go way up.

obyone

How do they spin balance them?

What's there to balance? I doubt anyone would drive fast enough on that thing to have any kind of vibration from balancing. Only thing that Buick is good for is conversation over a few beers or martinis.

ruking1

Handling is indeed measureable and of course EVERYBODY has a (their) seat of the pants feeling/s. Some "butts" are more veteran, if you will.

Tirerack.com has taken it to a great level and I am sure a lot of folks are thankful for the data and services.

The issue SEEMS to be that most folks really never MEASURE them.

In the so called "old days" , you had to buy and know how to set up and use EXPENSIVE and very sophisticated equipment to capture that data. However, most discussions have always gotten down to " damned the data", I like what I like, know what I know discussions.

So today one can spend less than $2,500 (still high I know) for those measuring device/s and suction cup it to the windshield and you too can be an auto critic. :shades:

kyfdx

255/40-17 and 205/50-17 have the same sidewall height.. The aspect ratio is multiplied by the tire width to get the sidewall height..

So.. you have to look at a lot more than just the "50" or "55" series.. it isn't as simple as that one number..

I have 18" tires on my car.... fronts have 40-series, and the rears have 35-series, yet both front and rears have the same sidewall height.. (not much...lol)

texases

True, but for a given car you'll be going to shorter sidewalls as you go to lower % values...the damage stories I hear are much more frequently associated with under-50s...

ruking1

Yes I would concur with your two takes. I would also add that I drive the car that has 40/35 AR 's night and day DIFFERENTLY. from 65/55 AR and even differently from 70 AR's. I do it seamlessly after 10 years now, but it was at first, ... a PITA.

jeffyscott

Yes, I was starting from the assumption of a typical car tire width...or my car's tire width, anyway. In my case, 215/50, the sidewall should be about 4.25 inches. The optional 18s would, of course, reduce the sidewall height to about 3.75 inches.

aclover

rharry1

I was just in a tire shop to have a flat fixed( approx. 20,000 miles on all 4 tires)and was told that the one tire needed to be replaced. I was also told that ALL four tires needed to be replaced at the same time. This seemed a little crazy to me and needed to find if this was true.

texases

Yes, it's true that all 4 tires on your Forester need to be close in circumference, otherwise the awd system can be damaged. 20,000 miles is enough wear to create a significant difference. So the tire with the flat could not be fixed?

One option is to have the new tire 'shaved' to match the size of the existing tires.

How much tread is remaining on the existing tires? Do you like them, or would you prefer a new set?

srs_49

Yes. The AWD drive system on Subarus is very sensitive to differences in tires, front to back. The front and back wheels need to rotate at close to the same rate or else the clutch in the transfer case will overheat (may have the exact details wrong, but you catch my drift).

Mr_Shiftright

I think they allow some difference. I've run new tires in front and somewhat used in back on my Subaru, no problems noted, but the difference in the tires was certainly not extreme---a few 32nds. I believe there is actually a spec on this tolerance.

krzyss

1/4" is written Subaru difference.
Circumference.

Krzys

Mr_Shiftright

yes, that's it...so, math whizzes, how might we translate that to a tire depth gauge, measuring it either in MM or 32nds?

ruking1

If I remember correctly 1 in =25.4 mm? So a 1/4in = 6.35 mm. Again, 1/4 in is 8/32nds.

I am not sure what you are really asking, but a 1/4 in of tire tread can be potentially HUGE, being as how most car treads start off at 10/32nds or .3125 in.

Mr_Shiftright

well they said circumference right, not radius. I was wondering how we translaste a 1/4" lesser circumference into a tread depth approximation.

The reason I ask is that it's pretty inconvenient to measure the circumference of a tire. I guess on a lift with a tailor's tape, it's do-able, if a tad imprecise.

I just thought it would be neat to be able to tell AWD owners how to make this call about mixing new and used tires.

stickguy

doing this in my head, 1/4" means 1/8" tread depth right? meaning 4/32.

kyfdx

1/4" divided by pi.. = .08 inches.. or about 2.5/32nds....

Most new tires have 11/32nds of tread depth...

kyfdx

Divide that by 2, as the tread is on top and bottom.. So... maybe 1.5/32nds, at most...

Geez...that isn't much.....