New Shoes...

[mattwithcats]

No comments on the date code of the old tires?

(52/03 and 04/04)...

They still had 4/32 tread left...

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

"Beginning in 1991, the speed symbol denoting a fixed maximum speed capability of new tires must be shown only in the speed rating portion of the tire's service description, such as 225/50R16 89S. The most common tire speed rating symbols, maximum speeds and typical applications are shown below:

L 75 mph 120 km/h Off-Road & Light Truck Tires
M 81 mph 130 km/h Temporary Spare Tires
N 87 mph 140km/h
P 93 mph 150 km/h
Q 99 mph 160 km/h Studless & Studdable Winter Tires
R 106 mph 170 km/h H.D. Light Truck Tires
S 112 mph 180 km/h Family Sedans & Vans
T 118 mph 190 km/h Family Sedans & Vans
U 124 mph 200 km/h
H 130 mph 210 km/h Sport Sedans & Coupes
V 149 mph 240 km/h Sport Sedans, Coupes & Sports Cars
"

 

[OVERKILL]

Yes, that's the revision of the spec that denoted where it was shown. Barry's article covers the history of the system.

Based on your post however, am I to assume that you ran tires older than 1991 and thus assumed they didn't have a speed rating?

 

[Traction]

Originally Posted By: mattwithcats
No comments on the date code of the old tires?

(52/03 and 04/04)...

They still had 4/32 tread left...

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

"Beginning in 1991, the speed symbol denoting a fixed maximum speed capability of new tires must be shown only in the speed rating portion of the tire's service description, such as 225/50R16 89S. The most common tire speed rating symbols, maximum speeds and typical applications are shown below:

L 75 mph 120 km/h Off-Road & Light Truck Tires
M 81 mph 130 km/h Temporary Spare Tires
N 87 mph 140km/h
P 93 mph 150 km/h
Q 99 mph 160 km/h Studless & Studdable Winter Tires
R 106 mph 170 km/h H.D. Light Truck Tires
S 112 mph 180 km/h Family Sedans & Vans
T 118 mph 190 km/h Family Sedans & Vans
U 124 mph 200 km/h
H 130 mph 210 km/h Sport Sedans & Coupes
V 149 mph 240 km/h Sport Sedans, Coupes & Sports Cars
"

Okay I'll bite on the date code, plus I'm raising the [censored] flag on this thread. You stated you have a 2002 Saturn. How do you get OE tires dated 03, and 04 on 2002 vehicle???

 

[mattwithcats]

Tires were originally on my 1998 Saturn.

My Dad gave me the 2002.
I traded tires to put the 205/60's on the 2002,
and the 185/65's on the 1998.
I then sold the 1998...

 

[HTSS_TR]

Originally Posted By: OVERKILL
People running improper tire pressures is a safety issue. The OP running his rear tires on a Saturn S-series, which is an extremely light vehicle, at like 20psi higher than the placard because he's developed some bizarre formula is an example of that safety issue.

Very unusual formula !

I changed tire size of my s2000 few times already. The OEM size are 215/45-17 front 245/40-17 rear and recommended pressure are 32 PSI all around. I increased to 34 PSI front and 33 PSI rear, performance/handling, ride and steering feel/quickness are all good.

One time I had 225/45-17 front 255/40-17 rear, I tried various pressures and the best compromised was 30 PSI font and 28 PSI rear.

Right now I have 215/50-17 front 245/45-17 rear, the best pressures are 28 PSI front and 24 PSI rear.

The max pressure of all various tire sizes are 50-52 PSI.

 

[Rand]

Originally Posted By: mattwithcats
Tires were originally on my 1998 Saturn.

My Dad gave me the 2002.
I traded tires to put the 205/60's on the 2002,
and the 185/65's on the 1998.
I then sold the 1998...


Which makes even less sense than before.

This whole thread makes less sense than I would high on acid and dying from antifreeze fumes in GHT/brazio's car

 

[Traction]

Originally Posted By: mattwithcats
Tires were originally on my 1998 Saturn.

My Dad gave me the 2002.
I traded tires to put the 205/60's on the 2002,
and the 185/65's on the 1998.
I then sold the 1998...

Well thanks, at least now is all makes perfect sense on how you came up with the ideal tire pressures. You should be in the tire business.

 

[OVERKILL]

Originally Posted By: Rand
Originally Posted By: mattwithcats
Tires were originally on my 1998 Saturn.

My Dad gave me the 2002.
I traded tires to put the 205/60's on the 2002,
and the 185/65's on the 1998.
I then sold the 1998...


Which makes even less sense than before.

This whole thread makes less sense than I would high on acid and dying from antifreeze fumes in GHT/brazio's car



BAH HHAHHAHAH!!! Man, if these two were to get together it could potentially compromise the integrity of the universe. Or, in the words of Doc Brown "tear a hole in the space time continuum!"

 

[mattwithcats]

You only have three numbers to work with,
the pressure listed on the door,
the max pressure on the OEM tire,
and the max pressure on the new tire...

Anyone got a better formula?

 

[OVERKILL]

Originally Posted By: mattwithcats
You only have three numbers to work with,
the pressure listed on the door,
the max pressure on the OEM tire,
and the max pressure on the new tire...

Anyone got a better formula?


You don't use a formula and you don't use either of those two other numbers which are just the MAXIMUM INFLATION PRESSURE OF THE TIRE, they are NOT a guide as to how the tire is supposed to be inflated, THAT number is the one on the placard!!

You are taking something INSANELY simple and trying to make it complicated and in doing so you are making your vehicle less safe! Over inflated tires, which offer a reduced contact patch, are UNSAFE!

 

[mattwithcats]

Tires are not overinflated...
I am not exceeding the max pressure on the sidewall,

I am adjusting the pressure due to a stiffer sidewall...

84% of max tire pressure is the correct pressure...

This is confirmed by getting 12 years
and 50,000+ miles, with 4/32 left.

Tires were worn evenly,
the edges were not cupped,
and the center was not worn,
an indication of excessive pressure...

 

[OVERKILL]

Originally Posted By: mattwithcats
Tires are not overinflated...
I am not exceeding the max pressure on the sidewall,


if they are significantly above the placard pressure, they are overinflated. The pressure on the sidewall is the MAXIMUM PRESSURE FOR THE TIRE, this is NOT the same as being the pressure spec'd for the vehicle! If you are 20PSI above the placard pressure, you are overinflated, even if you are still below the maximum pressure on the sidewall.

Originally Posted By: mattwithcats
I am adjusting the pressure due to a stiffer sidewall...


CapriRacer already covered that. No you aren't.

Originally Posted By: mattwithcats
84% of max tire pressure is the correct pressure...


No, it isn't. It is some ridiculous calculation you've pulled out of thin air that utilizes numbers that are completely irrelevant to the proper inflation pressure for your vehicle, which is the number spec'd on the placard. Full stop. There's no fancy formula, there's no percentage, you aren't the OEM, you have no bloody clue how they came up with the number they've given you and thinking you can magically calculate the correct number by basing it on the maximum inflation pressure spec'd by the tire manufacturer, a company that has NO BLOODY IDEA what that tire is going on is absolutely nuts.

If you are running significantly higher pressure than spec on OEM wheels with an OEM width tire you are a hazard to yourself and everybody around you. You are a liability.

 

[OVERKILL]

Originally Posted By: mattwithcats


This is confirmed by getting 12 years
and 50,000+ miles, with 4/32 left.

Tires were worn evenly,
the edges were not cupped,
and the center was not worn,
an indication of excessive pressure...


It's a bloody Saturn! It isn't going to wear out tires quickly, it is low powered and doesn't weigh anything! My buddy's Saturn, which he drove like it stole it, ran tires for 60,000 miles that were also worn evenly and he had to replace them due to age and weather cracking, not because they were worn out.

Also, you ran tires for TWELVE YEARS??? That's a hazard in and of itself.

http://www.edmunds.com/car-care/how-old-and-dangerous-are-your-tires.html

This thread just keeps delivering....

 

[mattwithcats]

The tire wear patterns say otherwise...

Had this on my Smart too...
Door pressure resulted in front tire edges
cupping (wearing) badly, adding 4-5 PSI
resulted in nearly even wear.

Still under the max pressure, however...

 

[OVERKILL]

Originally Posted By: mattwithcats
The tire wear patterns say otherwise...

Had this on my Smart too...
Door pressure resulted in front tire edges
cupping (wearing) badly, adding 4-5 PSI
resulted in nearly even wear.

Still under the max pressure, however...


That's not the same thing at all Matt.

There's a huge difference between 4-5 psi, which is acceptable for "fine tuning" and I generally don't have issue with (hence the range I mentioned earlier that BMW specified depending on how the car was loaded) and running a tire close to 20psi higher than specified on the placard.

Tire pressure is going to shift a few PSI either direction depending on how hot or cold it is anyways, so there's a bit of leeway built in. And different tires even of the same size and load rating will wear a bit differently and that's why people often "tweak" the tire pressure by a couple of PSI.

Also worth mentioning here is that wear is a function of design. That is, while you may observe what you would describe as "unusual" wear patterns running the OEM pressure, there is more than tire wear in play here. The tires are an integral component to the handling and suspension of your vehicle. How it steers, how it reacts....etc these are affected by tire pressure. The OEM tire pressure may not result in even wear. Ford specifies 30psi on the front of the Expedition for example, which, unless you rotate regularly, will cause shoulder wear due to scrubbing. Yes, you can inflate the tire above what Ford recommends to alleviate this but then you also change how the vehicle handles. You remove some of the built-in understeer that Ford put there and used tire pressure as a component of that characteristic, which is a safety device on a big, top-heavy vehicle.

BMW's with staggered tires will eat the centres out of the rear tires and the shoulders out of the front ones. This is by design.

Focusing exclusively on how your tire wears and ignoring the OEM recommendation is like being presented with a symphony and ignoring the entire orchestra while trying to find B# on a piano. Music is not one note and a tire is not simply how it wears. It is the only source of contact your vehicle has with the road and is, as I mentioned, an integral component to your vehicle's suspension. This was all tested and worked out when the vehicle was developed and the pressure on the placard is based on that extensive testing.

 

[EdwardC]

Like overkill mentions, its not so much the fact that you tweaked the tire pressure to get better wear/feel/ride.

The issue is how you ended up with your percentage calculation for proper pressure based on the placard and the random max pressure on the tire sidewall.

Wait, is he just trolling?

 

[Ifixyawata]

The guy who runs the place I used to go to get used tires always inflated every tire to max pressure per sidewall. He said that lower pressure is just for ride quality and that inflating to max would get you the longest wear.

I always aired my tires down to OE spec after I got home.

 

[OVERKILL]

Originally Posted By: Ifixyawata
The guy who runs the place I used to go to get used tires always inflated every tire to max pressure per sidewall. He said that lower pressure is just for ride quality and that inflating to max would get you the longest wear.

I always aired my tires down to OE spec after I got home.


Good on you for ignoring his foolish advice

The tire manufacturers have no idea what vehicle the tire is going on, subsequently, they also have no idea what the appropriate pressure is for that tire on a specific vehicle of a given weight, weight balance.....etc. They provide you with what the maximum inflation pressure is for that tire, which should be well above the pressure range specified by the manufacturers using that tire in their applications. This number is put there so that people who might be improperly using that tire in an application that doesn't call for it don't inflate it past that number and end up wearing it in their face, getting seriously injured or killed. If you've got an application that calls for 80psi on the placard and the tire you've got fitted has a max of 50 listed on the sidewall, you know the tire is not right for the application

 

[mattwithcats]

OK, original rubber was a "P" speed tire,
with 35 PSI max...

Rear tires are an "H" with 51 PSI max,
and front are "H" with 44 PSI max...

Putting 30 PSI in is not enough,
that's 60% of max pressure for the rear...
In other words, it would be like putting
20 PSI in the OEM rubber...

Do you want to drive around with 20 PSI in your tires?

 

[OVERKILL]

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=8

Why are you still using the maximum inflation number? It means NOTHING! Who cares what percentage of the maximum it is? It doesn't matter! The placard calls for 29psi, so you run 29psi. My Expedition, which is literally more than TWICE the weight of your car spec's 30psi front, 35 rear. What do you think the big old Michelin LTX's say on the sidewall? You can bet your kitties that it is a freakin' heck of a lot more than 30psi.

30psi in the 51psi rated tire is no different than 30psi in the 35psi rated tire. It isn't "like 18psi" it is 30psi. That's what the vehicle calls for, that delivers the ride engineered by the OEM. You keep trying to factor the maximum inflation pressure in here as significant when it isn't.