Maximum PSI ?

As far as I know, the imbalance is usually caused by the tires, not the wheels. Wheels are easy to precisely machine at the factory. The wheels are also much lighter than the tires, hence contributing to the moment of inertia much less.

A slightly asymmetrical tire mounting would also cause wheel/tire imbalance.

In any case OEM/non-OEM/factory-install/retail-sale tires having different manufacturing tolerances or not is a nonissue.

 

Every OEM tire I've ever had on a new car has had great balance and minimal out of roundness. They've been the smoothest tires I've had. It's only when I replaced them with aftermarket tires that I've had problems. The auto manufacturers put a lot of pressure on the tire makers to do proper QC, including on site inspections. I have no doubt that rejects from this process end up in the aftermarket. I say this because I spent most of my career in QA/QC, though not in the auto business.

 

I would think that's not because of the tire but because of the difference in quality of the workmanship in the factory vs. the tire shop. I wouldn't expect an average tire shop to be as successful in mounting and balancing a tire as the factory. Their placement of balance weights are often done in a hurry at the tire shop, almost seeming to be done at random, and I doubt that they have the same level of equipment as in the factory.

 

Curious to know the reason for all four to be set to the same pressure; Toyota specs 1 PSI less on the rear, right?

 

Yeah, that's just for convenience. It's easy to remember. I don't have to fiddle with the setting on the automatic infiltrator. 1 psi difference is negligible difference in our climate anyways.

 

Down a little south in East Central Illinois, I seemed to get a little less MPG in the Gen3 when I would have all four on the same PSI (IIRC, the rear called for 2PSI lower on the Gen3). So, I used to simply use a gauge to "down-check" the rears by 2PSI, while using the same setting on the air-compressor for all 4.

 

Yeah, you may get some improvement on mpg by playing with tire psi. I did play with higher psi on my Gen3 all the way to 45 psi. I didn't check if the front and rear adjustments made any difference. But with PRIME, I am getting well over 50mpg (gas engine only HV mode) without doing anything. Any fine adjustment is not going to improve it that much. So, I no longer over inflate my tires much. ~38 psi all around is easy to remember and maintain and gives me a few psi room for the pressure to drop when we have colder temperature.

 

Curiously, when I went to pickup my car last week, the fronts were at 35 and the rear at 37; and this was a volume Prime dealer. I had them adjust the fronts to 38, and so far 38F/37R is working fine for me. I also personally think 1PSI diff shouldn't make much of a difference, but if this "complexity" of the 1PSI diference cleared Toyota Marketing (which tends to KISS), that makes me take notice; perhaps this influences VSC (Vehicle Stability Control), etc., I don't know.

 

Sounds like they rotated without checking/adjusting pressures? Setting them all to the same pressure can avoid that hassle. Dealership is sort of obligated to stick with spec pressures. But for DIY it's handy.

 

This was on a new car (25 miles), so I doubt they rotated. It was probably a case of some sort of reverse-application of the standard Prius 36F/34R spec, I suppose. It seems to me Toyota should have engineered all their vehicles to have tires all set to the same PSI to avoid all the confusion and also to make it more DIY-friendly

 

I doubt any extra engineering is needed, just a policy change. One or two pounds difference is pretty trivial.

 

That must be the case. I always do my tire rotation twice a year at the time of tire change from summer to winter and winter to summer. I instruct the dealer not to mess with tire rotation if I have any service that falls in between the season. With two sets of tires odometer reading 5K miles is not always what the tire had been on the road.

I have marked my tires with R1, R2, L1, L2. I keep the odd number pair in front in odd number year, and even number pair in front in even number year and do straight front to back rotation as Toyota recommend for both summer and winter tires. The tire changes are twice a year spring and fall. Usually summer tires get little more than 50K, and winter tires little less than 50K, but it is the easiest way to remember the rotation pattern.

 

Reviving an old thread... Just because I saw this. LOL

Guy Over-Inflates Boss's Tires Because "He Couldn't Get All The Tires to 100%"

 

That could be so dangerous.

 

Yeah. Heard a story of one tire blowing at a tire shop, damaging the car. Owner kept pumping in air because the TPMS light wasn't going off.

 

With my new MaxLife non-eco-LRR tires, even with them pumped up to 46 psi, they do not get the fuel economy that the stock A29s got at 40 psi.

Now as for inflating to 100%... while he's at it, might check that he's using oil that goes from 0w100% too!

 

How new are they? For EPA tests, the tires can't have more than about 4000 miles of wear. As wear increases, the rolling resistance bets better.

 

Yes, and sub-4000 mi.

 

New always does worse when compared to the old, worn tires. Even if the same tire model. Then something about the manufacturing process might leave the the initial layer of rubber with a higher rolling resistance.