Recommended Tire Pressure

Atm-- at the moment, oops, my texting abbreviations snuck into my pc post :/

 

I've been running 65 psi in my Insight-I tires for years (44 psi sidewall rating). No problems.

 

How are your roads ?

 

Typical Southern New England highways and suburban roads, some potholes and frost heaves. But Insight also goes to Boston, where roads are worse on average. No problems either place. With a car in say Guatemala (some smooth highways but cobblestone streets in Antigua and dirt roads in other areas) I would not go that high. Not so much because worrying about bursting tires, more about loads transmitted to the suspension causing wear there.

The improvements in mpg diminish the higher you go, and of course ride suffers. I figure 65psi gives a good mpg improvement and I don't speed, so I hit bumps more gently (and have more time to avoid them) than many people on the road. Others use higher psi.

Prius is at 44psi and that seems fine for the way I drive. I may experiment with it sometime.

 

I installed Energy Savers yesterday and tried to set the air pressure but it was 80F so it was difficult to get it where I wanted it. Today I noticed the tires felt out of balance like they were skipping down the road. I checked the pressure and they were at 58psi or so! It was 98F out but I lowered the pressure anyway and the ride home was smooth. Maybe these tires don't like high pressure?

 

I agree.

On dry good flat roads the tire's sidewall max pressure delivers better MPGs

On uneven - grooved (e.g. rumble strips) - poor road - to get better fuel efficiency the tires need to deform a bit more to the uneven road surfaces and the lower tire pressure setting that Toyota recommends gives better handling performance and fuel efficiency.

 

LOL. In a moment of euphoria and zeal.. we all get carried away at times...

65 ATM would crush a nuclear submarine which are normally rated at 30 ATM...

 

A Prius is much heavier than the Insight and has a higher center of gravity - so the Prius ride will be harsher and handling worst than the Insight at those pressures. I agree - it is not the tires which are at risk but the suspension and the shocks. I found that the mpg boost (atleast on a 3rd gen Prius) from going over max sidewall pressures (50/48psi) is optimized when the road is dry and smooth and when the vehicle is going at speeds where wind resistance/drag is not a signficant factor.

 

I haven't noticed any problems whatsoever with the ride or handling of either one, at least the way I drive. Certainly braking wet or dry is fine. But I have not gone up to 65psi with the Prius.

Wouldn't it be great if we had a way to adjust tire pressures from inside the car while driving, to cope with different road surface conditions?? Unfortunately, we don't. I'm not sure why MPG would be lower at higher pressures on rough or wet pavement. I'll just go with what works on dry smooth pavement and take what I get in other conditions.

 

I normally keep mine around 42 front and 40 rear. Of course, the PSI will go up as I drive but I think it's a good range.

 

^^ The sidewall max pressure is a cold tyre rating, so no worries.

 

That's what I thought. After I started driving for a while I checked and they were upwards of 46 which kinda scared me a little bit.. Does that mean I should be safe going 44/42 even if they get to 48/46 due to driving? That seems pretty high.

 

^^ Sure. The sidewall max pressure has a hefty* safety margin built in. Just do not pump over max pressure and then go off-roading

I can understand pumping up tyres over sidewall max pressures for a fuel economy challenge, but for day to day driving the marginal improvement is going to be quite low, perhaps too low to recognize.

* IIRC 20%, but do not quote me

 

I ran Goodyear Assurance FuelMax on my 2008 at pressure you are suggesting and wore them out in the center of the tread in less than half their guaranteed life. My current policy is 2 lbs above door post recommendations. I hope I'll get better wear on the Yokohama YK580's.

 

The Fuel Max tires are unique in this case. They wear out the centers very quickly and even quicker when overinflated!

 

My 2011 came with Goodyear Assurance tires. They don't say "Fuel Max" on them but to the right of "Assurance" there is a little fuel gauge symbol with the needle on F, and Tire Rack says the OEM Goodyears are Fuel Maxes.

I have been running them at sidewall 44psi since I got the car about 15,000 miles ago, and have just gone up to 50psi. I just checked the tread with a digital gauge and found even depth across the tread of all four tires.

Maybe there is something different about the Gen-II (rim width? suspension geometry?) or about the Goodyear Fuel Maxes used on them??? Or maybe I'm just blessed??

 

I have the same tires and at 16,000 miles they are wearing evenly. I always run at least 40 psi, currently at 46/44psi. Maybe they have changed.

 

There is also a difference between aftermarket and OE Fuel Max tires. They even sell both models at TireRack and they offer different max pressure and warranties. That could be the difference right there.

 

Interesting, I didn't realize the OEM Fuel Max's were only S rated. I should get down on the ground and read my tires more often

I don't care about the low speed rating but an S rating usually implies an inferior construction compared to an H. These don't feel bad for OEM tires on a low/moderate priced car. I will go for something better when I replace them though.