Its summer and the temp never goes below 50 and highs of 80, I work at a tire store. Guys there say that no matter the tire pressure in the door, its 35 psi, and in Subaru’s the placard says 28 front 29 rear. It’s getting to be a fight with them over the manufacturers recommeneded tire pressure or their “universal” 35 psi. And yes I know most cars like 35. But on the Subaru’s and tundras and the geo metro, that will just lead to centerworn tires and reduce braking. But they swear that 35 will make any ride smooth, wear nice and even, and improve all characteristics of the vehicle. I know its wrong, but how wrong are they?
1 Like
Every real tire store I go to always checks the door placard. Who actually sets this 35 PSI policy ? I can’t believe that your place has not had some customers complaining about the higher inflation.
2 Likes
Ignore them, it’s your car. Set the tire pressure to what YOU want, ie the MFG specifications, and stop discussing it with them.
Just a note. The Chevrolet Corvair had extremely different tire pressures for front/rear to ensure safe handling.
1 Like
You’re right, of course. What does the owner say? Is this his policy?
Well using 35psi in every tire doesn’t really make sense honestly, its arbitrary. Do you think the mfg posted the tire pressures on the placard Willy Nilly? No Sir, there are good reasons for the pressures they recommend and they came about those numbers using science, weights and measures, tire mfg input, engineering degree’s etc… People with a much higher pay grade than the “35psi Guys” came up with those numbers, so I am inclined to use them… UNTIL…some environmental conditions dictate otherwise. There are times when all bets are off and you can choose the pressure that meets the immediate need based on the environmental conditions at a specific time, but for all other normal road use conditions, follow the placard. It is there for a reason.
Thats the opposite…it will make your ride less enjoyable.I put 28 psi in my tires because I don’t like to feel like I was riding a skateboard.
These guys are wrong!
It has only been 12 hours since Chris posted but I think I would like to know where this so called tire shop is and the name of it . A mass email campaign to them that this practice makes no sense at all .
@CapriRacer Do you want to weigh in here ?
1 Like
These are what is known as “lazy idiots.” Don’t listen to them.
1 Like
Those ignorant people are just doing this for their own convenience. Nothing more, nothing less
Are you sure about that?
My Outback’s placard specifies 32 front/30 rear.
In the interest of improved handling–with no detectable difference in ride quality–I inflate my Outback’s tires to 34 front/32 rear, being careful to maintain the specified 2 lb front/rear inflation pressure difference. My tires wear evenly, with no evidence whatsoever of greater wear in the center of the tread. Of course, I do rotate them every 7,500 miles.
2 Likes
Any customer of this shop who has an accident where traction or braking are factors could sue them for their active carelessness.
[quote=“VOLVO_V70, post:7, topic:142470”] ……@CapriRacer Do you want to weigh in here ?
[/quote]
Man, I must have been asleep this morning! I totally missed this.
Yes, of course I want to weigh in - and thanks Volvo for the reminder!
For as long as I have been a tire engineer - 46 years and counting - I have encountered folks who think there is a universal, one-size-fits-all, tire pressure - and some of them work in the tire industry.
They are wrong. The Corvair is a great example.
So what do the tire manufacturers say and do? They SAY follow the vehicle manufacturer’s specification - which means the vehicle tire placard. They DO on vehicle tire testing at the placard pressure for the tire size listed there.
What does the government say? They say follow the vehicle tire placard, that’s why they mandate it. Have been since - and it’s a little fuzzy on the date, but - the early 1970’s.
So what do I recommend for our OP Chris? Talk to the shop owner - or if it is a chain, the store manager. Follow HIS procedure. He may be wrong, but he is boss. And as an exercise have the boss call a tire manufacturer - just pick one, it doesn’t matter which.
2 Likes
@CapriRacer gave the best answer. I agree 100%, sort of. I just add about 2 psi over the placard because tires loose about 1 psi a month. So over time the tires go from 2 psi above to 2 or 3 psi below when I check them again. That kind of averages out to the manufacturers recommendation over the period of time between checks. I get really good tire life.
The Corvair is an excellent example; 35 could be deadly in that car.
What are your thoughts on tires losing a couple pounds per month? I have a friend who insists this is so, but I haven’t seen that problem in 30 years. I know pressure changes w/ outside temps, but I can drive for months w/o adding/removing air… just check and go. (My TPMS displays pressure in each tire, so it’s just a weekly glance at the gauge.)
I usually have them put in 2 extra pounds because the tires are warm when I arrive at the tire shop.
Ever since I switched to Michelin tires, I have not had any pressure loss, except for what can be attributed to extreme changes in the ambient temperature.
With radial tires, the difference isn’t that extreme. Under-inflating is much more dangerous than over-inflating. Going above the recommended pressure (but under the tire cold max) is likely going to prevent people from complaining about their TPMS lights coming on in a few months.
Plus, what does a tire enthusiast do the next morning after getting any service that touches the tires? They probably adjust to their preferred pressure.
For those who would enjoy some very in depth discussion on tire pressure bicyclists seem to carry it a little deeper
With the vast majority of automobile owners if the TPMS warning light stays off all is well so keeping it off would be the single most overwhelming objective of tire shops.
Car makers do it for a reason and most of it is ride characteristics . My Trailblazer says 30 front , 35 rear . I do generally run them around 34 all the way around. Had issues with the stupid TPMS going off in the winter even though they were not low at 30 psi .
Very generally speaking 35 psi is going to work for most automobiles and light trucks (LT tires notwithstanding). If you have no clue at all what the recommended tire pressure is, then setting the tire at 35 psi is probably going to be a safe bet. Chances are you won’t be grossly over or under inflated at that pressure. Is it the correct pressure for all vehicles? No it is not. The tires on my car are supposed to be set at 32 PSI, but there wouldn’t be any major drama if I inflated them to 35 PSI.
The idea that 35 PSI is a universal tire pressure is sorta-kinda half right, it’s going to be an acceptable pressure almost all the time for most road-going cars, but it’s not going the pressure that the manufacturer species most of the time. 35 PSI is the cheese of tire air pressures, it works with most everything, but not all chefs will call for it in their recipes.
I always figured 32 but I got my tires rotated today and on the invoice, they had the tire pressure for my car listed at 30 front and 30 rear. They also adjusted the pressure because from the TPMS I had 34 in them before. Yeah 30 is what the book says. The Acura is different for the front and rear and always have to look it up.
1 to 2 psi pressure loss per month (for passenger car tires) is considered by the industry to be the upper limit of acceptable. I suspect this goes back to the first days of tubeless tires as this was in place when I first arrived, hasn’t changed in 50 years , and the vast majority of tires don’t experience anything even close.
I also suspect that this value is so high because tire dealers don’t want to have to deal with fixing it - for which they don’t get any revenue.
So I think a 1 to 2 psi pressure loss per month to be worthy of finding out where the seepage is occurring. A common culprit is corrosion of alloy wheels. But I would do this myself (instead of having a tire dealer do it) using a spray bottle of soapy water. Once the problem area has been found, then take it to a tire dealer to get fixed.