Your tire pressure

Did you ask them if they have any data at all regarding tests where tires were ran at various pressure including overinflation or did you just take their word for it an assume they did these tests and found that overinflation didn't reduce rolling resistance?

 

I don't know how you got that from the Michelin quote. All they said is that they have no tests that prove that higher pressures than those recommended will give better mileage. I would not expect them to.

Then they say that you should not go above the maximum pressure on the sidewall and you should go with the recommended pressures. So what else is new. Nothing to see there, move along!

 

After reading most of these posts on this thread, I've got a question: Does anyone know, ----- does/did Toyota, or excuse me the government agency that is responsible, pump up the tire pressures super high to obtain the the mileages that are posted on the window stickers? My mileage is not coming up to what it is suppose to be, however I'm not about to ride around like I have solid rubber tires on the car. Don't want to add any sqeaks and rattles to the car due to "hard" tires. If that is what has to be done to obtain super high FE then I guess I'll never be posting my mileage here on the forum. I have GoodYear Assurance tires. I run 35 psi. The cars computer has the tendency to tell me I'm getting 50+mpg, however you put your own calculator to it and it is 3-5 mpg less. Oh well, I'm still getting more than any other car, and enjoying it!

 

No and you likely have a MUCH different driving routine that the EPA testing procedures.

 

It was query submitted to their website, which got an answer but no doubt not from engineering. Most likely this was a search result from Michelin databases. Since anecdotal experiences abounds here, why not make a concerted push from Prius Chat to all manufacturers to find out what their data indicate? Make up a standard query to them all.
I was surprised as well as urban legend (check Mythbusters on tire pressures as well) for decades says higher pressure gets better mpgs.
After all, we're all taking *your* word for it, aren't we?

 

Our prius has 44 PSI max nitrogen (from Costco) in all 4 tires now for well over 6,000 miles. The tires are wearing fine and the car handles great. Note: 44 PSI is Max sidewall Pressure.

Our second vehicle is a 2003 Jetta Station Wagon TDI 5-speed manual with Michelin 195 X 65 X 15 inch S-8 tires, (Green X technology for Max MPG's).

They are inflated with Nitrogen to 51 PSI max sidewall pressure in all four tires, and have been for over 45,000 miles. The tires are wearing as normal and I should get over 50,000 miles on them which is very good for this type of tire.

If you are worried about inflating your tires to MAX SIDEWALL PRESSURE because they may blow out, you may consider buying tires that are more structurally sound.

Personally I perfer Michelin as well as millions of other car owners. Also I have since 1993 always inflated all my previous cars to max sidewall and never had any problems with wear and/or handling.

alfon

 

When Costco inflates your tires with nitrogen, how do they get all the air out first? I doubt they have a vacuum chamber in which to inflate the tires.

 

A regular poster here -- Bob Wilson? -- has posted a graph of rolling resistance vs. tire pressure, from an external source, several times.

 

The tire manufacturer, the car manufacturer, and the dealer want you on underinflated tires so you'll have to buy new tires sooner rather than later. The heavier the load, the higher the tp needs to be to safely handle it.

 

1) Set tires to placard psi
2) Warm up the car
3) Reset trip B
4) Drive a 10 mile round trip
5) Note mpg and reset trip B
6) change tire pressure to max sidewall
7) repeat same 10 mile round trip
8) Note mpg

Its that simple.

 

Hey guys...quick question. Why do you guys inflate the front tire higher than the rears?

 

Because that's what Toyota says to do. Look at the sticker on the door frame; look at the owner's manual.

 

The Prius has more weight over the front tires. More weight = higher tire psi needed.

The max sidewall PSI is the PSI that the tire manufacturer says is a usable maximum pressure - and is the PSI they say you should use when loading the tire to maximum weight. It is NOT the pressure at which the tire will explode/fail (which is much higher unless the tire is defective)...

The "sticker" psi is the pressure recommended by the car manufacturer - based on weight of the vehicle but also any other factors they choose to consider, one of which is "ride quality". (does anyone know if this only applies to the OEM tires originally installed? I'm guessing it might...)

Pretty sure the EPA uses the "factory" (i.e.: sticker) psi so that nobody gets an unfair advantage by messing with the pressures. (However, WE can get that unfair advantage if we want)

I had read that TPMS will indicate whenever any tire drops more than 8psi below the set threshold. (and I think the manual describes how to set it - the factory sets at the sticker psi, but you can change it higher by resetting)

 

Spare is NOT equipped with TPMS!

 

I keep my Yoko's at 40 psi all around. I noticed a 3-4 increase in mpg when I changed them from factory setting. I didn't notice too much of a difference in ride quality. It definitely glides better with higher inflation.

I am toying with the idea of going above max sidewall (44 psi) and seeing how that performs. I don't want the ride to harsh since it could cause rattling and vibrations.

I also wonder what the long term effects are on the suspension or other mechanical parts if the tire pressure is too high?

Are there any longtime Prius owners that run their tires above 50 psi? And for how many years? Have you had any suspension or other related problems. What is the risk?

I am more concerned with mechanical issues than safety issues since tire pressures at 45-50 are well within the safety net limits.

Thanks for any feedback. I am learning a lot about my Prius from this site!!!

 

I also wonder this question, I don't mind the tad bit harsher ride for a few MPG gain. The thing that I am worried about is the wear and tear on the suspension. I doubt it's a noticeable difference to be honest. Anyone have any further information on this?

By the way, my PSI are as follows: Front: 42 Rear:40. Been driving this way for a few months. I like it much more.

 

I cannot say whether or not I have suffered any premature wear because of high tire pressure but I have run over 50psi for over half the life of my car. I may have started over inflating around 50k or so and I have 105k on the car now. I think my shocks need replacing but that is pretty common by 100k.

 

Manufactures of tires over spec the tires, so there is a margin for error on the sidewall pressure. That way there is less of a chance of a blow out. Over inflating distorts the tire so that less of the tread is on the road. Less patch, means less rolling resistance, which will increase mileage. But the same could be done more easily by using skinnier low rolling resistance tires on smaller wheels. The draw back is less traction which means worse skid pad (turns must be taken slower to be safe, traction control will kick in earlier) and worse braking in tough conditions.

Pumping up the tires for smooth roads, and dropping the pressure for bumpy roads makes sense. Its those bumpy roads that over inflation is most dangerous. I stay inside the manufacturers recommended 51psi on my car.

On my tri bike I have skinny 23mm tires pumped up to 100psi. On my mountain bike I have 60mm tires, and I drop the pressure to 20psi for rough trails, but pump them higher for smoother paths. It takes me about the same effort to go 25mph on the tri bike as it does to go 10 on the mountain bike on a flat road. If I took my tri bike on a rough trail, I'd likely at a minimum bend my rims, and if I rode further I would definitely pop a tire or brake some spokes.

 

Thanks. Still, the engineering question that no one seems to know the answer too is why tires are still built to the same pressures for the last several decades, particularly after the mid 1970's gas crisis? Is there a physical limitation to construction? Air pressure? Lack of motivation?

 

Tire manufacturers are in the business of selling tires. People, in general, do not want high PSI tires. They want comfort, "looks" and silly things like "Z" rated tires, which are rated at 149 MPH. 99.999% of people with ZR tires will never drive 149 mph, but like the thought of having fancy high speed tires. Logic and common sense are not selling points.