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Maintaining Tire Pressure

Have Michellin tires - 4yrd old with 34k mileage - today Firestone gave me thread reading of
3 6 2 (front) and
2 7 1 (rear)
Outer, Center and Inner, in that order. And tire pressure of 32 and 31 (rear)

They tell me that it has been driven with low tire pressure. I went to America Tires on 10/30 for rotation (ie 25 days ago) - they inflated to 35 front and 33 rear (though, I do not see them doing). Don’t know why front lost more psi than the rear.

I am seeking tips in maintaining my tires. Thanks.

While those numbers can be caused by under-inflation the can also be caused by excessively hard cornering.

Buy a tire tread depth gauge, a cheap mechanical $2 gauge will work just as good as the fancy digital ones. Also get a good tire gauge, this time spend some money and get a good one. You might also want to get a good battery powered pump.

The numbers you have posted indicate the tires need to be replaced now, if they are accurate. I’d check them myself first though.

BTW, don’t get too hung up on the numbers provided either by America Tires or Firestone, there will be differences in their gauges. I doubt seriously that they use calibrated gauges as they are very expensive. Most of those tire gauges read in increments of either .5 psi or 1 psi so the tire pressure differences may not be that much.

Good advice @kieth. Nothing to add.

If I had those tread depths, I’d put 38 psi in the front and 35 psi in the rear and start saving for new tires.

I just went to America Tires and they measured it in front of me
There is no 1 or 2 measurement - maybe 5 - the center might be 5, 6 or 7.

Do they really put Kendall Syn blend engine oil especially with a coupon? Anyone can comment?

Keith has offered excellent advice.
It sounds to me like a good tire pressure gage and a pump are the perfect solution… but you need to use them. You need to check your tire pressure no a regular basis and add some when necessary. Do this regularly and you’ll have to buy far fewer tires, and at today’s prices that ain’t chicken feed. The tread depth gage is cheap enough to be worth it, but if you maintain the proper pressure you should be able to use the wear bars. When they start becoming obvious, start saving for new rubber.

I’m not a fan of Firestone. The one here faded out about 30 years ago due to fraud and incompetence. Their reputation was horrible. Unfortunately, they’re resurfaced after all of this time by buying out a very small chain of regional tire franchises and have set up shop just a few blocks from where they used to be.

Scroll down this page of threads and peruse the one about a 2002 Jeep needing a head gasket or engine; all according to Firestone.

^Seconded. Bought a car; brought it to F-stone (State College PA); was told I needed ball joints. Had them do the ball joints and went about my business. Came back 3-4 months later for tires; was told I “needed new ball joints!”

(Yeah it stunk knowing I likely paid for work I didn’t need…but honestly it felt worth it when I got to watch 'em hem and haw when I whipped out the invoice from the glove compartment!)

That was the problem with the Firestone here. Every car that entered a service bay no matter the age or mileage “needed ball joints” or “they might break next time you cross a railroad track…”.

A couple of thoughts:

  1. Those tires need to be replaced NOW!!

  2. Inflation pressure is only one of several things that can cause tires to wear unevenly, so don’t necessarily boost the inflation pressure thinking you will be curing the uneven wear issue.

  3. Tires aren’t all designed to wear the same way. Different manufacturers will have different methods and the result isn’t always perfect. In other words, if one brand of tires is wearing unevenly, that doesn’t mean another brand will.

I’ll just add that tire pressure is directly linked to the ambient outdoor temperature. If you put 32 psi in your tires in August…the pressure will be lower in November. If the tires are cold and you add air pressure…you are over-inflating your tires. There is a lot more involved than reading a tire pressure gauge.

@missleman, I undrstand that you are supposed to air the tires to proper pressure when cold. I’ve read that advise many times on this forum as well. But, I do agree that ambient temps affect tire pressure. It is said that you could lose 1 psi for every 10-deg drop in ambient temps. I check my tire pressures once a month, although I admit I neglected my wife’s car in the last couple of months. Her TPMS light went on when the cold snap hit last week. All tires were 4-5 psi low.

The 1 psi for every 10 degree drop in pressure is fairly accurate. I inflated my tires to 32 psi at around 70 degrees and when I checked them at 18 degrees (round off to 20)…there was a 5 psi loss. When I drove on the interstate for a couple of hours…I stopped at a rest area and all my tires were back to 32 psi. I believe if the temperature shot back up to 70 degrees…my tires would all read 32 psi after they cooled down.

@CapriRacer
May be you did not read my 2nd post - the measurements from
Firestone below are False
3 6 2 (front) and
2 7 1 (rear)
Outer, Center and Inner, in that order.

Are you still saying tires need to be replaced NOW?

Take a look at the tires and compare tread depth to the wear indicators. These are raised sections within the sipes that are a decent no-gauge indicator of thread wear, and they extend the width of the tire, so you can use them as an easy indicator of uneven wear as well. How do they look? Any excessive edge wear noticable? I trust F-Stone as far as I can throw the shop.

“the pressure will be lower in November. If the tires are cold and you add air pressure…you are over-inflating your tires.”

I gotta disagree with this. If its -10 and you inflate your tires to the prescribed 32# and drive on the freeway for an hour and they hit 35#, they are not “over-inflated”, they are properly inflated. When they cool back down to -10, they’ll be at 32 again. You don’t deflate your tires to 30# in anticipation of driving on the highway. Really though, the most I’ve ever noticed a tire pressure increasing on the road due to road heat is a couple three pounds. Inflate in the garage when cold to the proper pressure which can change from month to month with temp changes, and don’t worry about it.

"May be you did not read my 2nd post - the measurements from
Firestone below are False
3 6 2 (front) and
2 7 1 (rear)
Outer, Center and Inner, in that order."


Well, if Firestone made up a bunch of bogus measurements, why bother repeating them here? How did you determine those measurements were false, and what are the true measurements? (Incidentally, who provided the measurements you trust?)

sciconf said: "@CapriRacer
May be you did not read my 2nd post - the measurements from
Firestone below are False
3 6 2 (front) and
2 7 1 (rear)
Outer, Center and Inner, in that order.

Are you still saying tires need to be replaced NOW? "

2 thoughts:

Anything less than 3/32nds of an inch would indicate the tires need to be replaced - and if I assume those measurements are accurate, there are 4 readings that qualify.

Your second post says the 1 or 2 readings are really 5’s - so what is going on?

If those readings are false, then my recommendation would not apply, but it is unclear what the real readings are.

So like Mean Joe said, what ARE the real readings? and how could we possibly make a recommendation based on bad data?

@CapriRacer Yeah, I’m a little confused at this point too.