Maximum PSI ?

The tire brand doesn't matter as far as fit and load-carrying capacity are concerned. The tire standards, such as load ratings, are uniform across tire brands. All you need to do is to buy a tire of the correct size and standard (P-metric and ISO-metric are not interchangeable) and inflate it to the correct pressure. All this information is specified on your tire placard. I have never seen a tire brand specified on the tire placard.

Car manufacturers choose the tire brand like they choose any other part. If the car is manufactured in Japan, it naturally tends to be Toyo. However, it could also be Bridgestone, Firestone, Michelin—you get the idea, and it could change every year, while the tire size and pressure remain the same for a given model.

 

I don't think it anywhere near as simple as that. At any given time for a new vehicle design there usually already exist off-the-shelf tires that fit the requirements... ...unless, perhaps, you are trying to build a redesigned Humvee or M1A1 Tank, that is. However, tire manufacturers are also trying to make improvements to gain a greater market share. They know broadly what requirements need to be met for both general and specialized purposes, but at the same time they want to improve their product to reach as many customers as possible. They do so by making improvements to their product that will not cause it to fail QA test and evaluation standards that have already been established... ...They then promote their product to the auto manufacturers and get their endorsement.

 

you can still buy 35psi rated tires, I own several cars that call for more than 35 on the placard.

If the tire meets the weight rating and speed rating ???

I think that is his point.

I can buy tires that are rated for less pressure than the door placard calls for.[/QUOTE]

 

Hmm, those cheap tpms units are lot less expensive than I thought they'd be.

 

No, no, no, no.

35 psi tires are P-metric tires (with P prefix) and 44 psi tires are ISO-metric tires (no letter prefix). P-metric tires and ISO-metric tires are not interchangeable. If you switch from a P-metric tire to an ISO-metric tire, your speedometer calibration will change and your load-carrying ability will change. The pressures specified on your tire placard are for the tires that came with your car, which are either ISO-metric or P-metric. If you change from ISO-metric to P-metric and vice versa, these pressures will no longer be correct, as the tires have different load vs. pressure tables depending on the industry standard (ISO-metric, P-metric, etc.).

https://www.toyotires.com/tires-101/tire-load-and-inflation-tables

 

On some websites, the P prefix is explained as Passenger tire.(1st attach)
Cooper Tire issued a Service Bulletin to specify differences between P-metric vs European (2nd attach)

But my question is: If I have an axle of P-metric tire and one with European, knowing that the ONLY difference is pressure, why not can I inflate as needed? I don't think P-metric tires are made from another rubber ( I mean containing components, as latex, anti aging agents, carbon black and other chemicals) , only they have different formula calculation...

 

P-metric vs. ISO-metric tires are very similar, but their dimensions will be somewhat different, including the rolling radius. The construction, like the roundness of the tread, is also slightly different.

If you installed a different type of tire than it is specified on your tire placard, then you can try looking at the load vs. pressure tables and figure out the pressure on the other standard that would give you the same load as in the original standard for the pressure specified in the original standard. For example if 33 psi results in an 1,100 lb load for the P-metric standard, look at the ISO-metric table and find out what the corresponding pressure is for an 1,100 lb load. This would probably be the correct pressure for an ISO-metric tire, even though your camber adjustment etc. in your wheel alignment might still be off.

https://www.toyotires.com/tires-101/tire-load-and-inflation-tables

 

Thank you for your answer.
Regarding car placard, they reccomand only the pressure, not the tire type, in this case, how would I respect car placard as advised in previous posts?

Please, understand I am writing this only to clarify this subject. I had a ton of discussion with people, technics, and did many searches on the internet and other documentations, and I must admit they differ substantially.

 

They are interchangeable. The guide you link to even discusses how to determine tire pressure between ISO and P metric tires of different sizes. When going from ISO-metric to P-metric, care needs to be taken in making sure that the OE load index is being met. ISO-metric are a couple points higher. That could be accounted for with higher pressures,, but most people should stay with ISO if that was the OEM tire.

The width and sidewall size of ISO and P tires are the same. Switching between the two won't miscalibrate your speedometer. Tirerack has the revolutions per mile included in the tire specs, and it varies between tire models of the exact same size. The speedometer will only be off if the tire diameter changes. I had slightly larger than OEM tires on a car that put the speedometer off by 1%; I was actually doing 50.5mph when it read 50mph. Which is probably still lower than what I was truly going, as most manufacturers calibrate the speedometer lower.

 

All major tire makers should have load versus pressure tables available on their web site.
But you might have to dig a bit to find it.
They are easier to find for truck, trailer and utility tires.

IF.....you have a passenger car or light truck, you don't NEED those tables because the vehicle maker has done the research for you.

 

Obsessive, compulsive "disorder" exists in Romania too, it seems.

Seriously, it sounds like you worry WAY too much.
ANY tire of the proper size....or close.....that is available on the open market should work JUST FINE at the pressure originally recommended by the car maker. A couple of PSI one way or the other will make little or NO difference.
Honestly it won't.

 

There is no letter prefix in the ISO-metric standard. There is a P prefix in the P-metric standard. According to your tire placard, you have 215/50R17 ISO-metric tires with a load index of 91, as there is no P prefix, and the 230 kPa = 33 psi pressure shown is for ISO-metric tires of that size.

The load and inflation manual explains in detail the procedure to find the correct tire pressure if you change the tire standard (such as from ISO-metric to P-metric) or tire size. In your case, if you change from ISO-metric to P-metric, your pressure would be reduced about 2 psi from 33 psi or 230 kPa to 31 psi or 215 kPa.

You basically look up the pressure (33.4 psi in your case) and load index (91 in your case) for your original tire to find the corresponding load. You then go to the table for the new tire and find the pressure corresponding to the load you calculated for the original tire for the new tire standard, new tire size, and new load index. You need to look up the correct table and be careful because there are standard vs. reinforced tires and load indexes also vary. You will also need to do some interpolation. Refer to the load and inflation manual for full details.

https://www.toyotires.com/tires-101/tire-load-and-inflation-tables

 

It's most likely to prevent flat-spots from inventory that doesn't get sold, or even moved, for long periods of time. Flat-spots from cars (and even big trucks) parked for lengths of time cause undue headaches for service departments and warranty claims.

 

... and all the U.S.-market cars built in Japan start with a long Pacific cruise to even get here, before they have any opportunity to sit on dealer lots.

 

I would not worry about this. The cars are very well protected, you can watch here only one example (min 2:30)

 

Sorry, but I just don't see what they might be doing in this video to prevent flat-spotting of the tires while on those ships. Beyond the already-known extra tire pressure, that is.

 

Yes, you are right. I wrongly believed you worry about exposure at salt conditions, wind, etc. My mistake.

 

About original equipment tires, written by a retired tire engineer: Barry's Tire Tech

About high inflation pressure for ocean shipping...the cars are lashed down on the car carrier. Harder tires, i.e., higher inflation pressure, allows a more secure lashing and less bounce when the ship is in rough weather.

 

Yap, I have changed baterries a half dozen times on two vehicles in last 2 years. Buying them in bulk makes more economical. Also, if anyone use them during winter on salted roads, make sure to lubricate the thread of the valve stem where the sensor screws in. At the contact of two dissimilar metals, they tend to corrode and fuse. I had to destroy the sensors to remove them after the first winter without lubricant. I use silicon lubricant now, but other type of lubricant may also work.