Your tire pressure

I've read through most of this thread relating to tire pressure. I was a bit nervous about bringing up the pressure because I was worried about tire failure. I just brought them up to 40/39 and I've seen an increase of 6 mpg. (I also do the lower grill block). My questions are ... When I did this the outside temp was ranging from the low teens to upper twenties. Now, at least for a few days, we're going up to the low forties.. Are the higher pressures going to be a problem? And at what outside temp would you drop them down to normal??

 

I have GoodYear Triple treds on right now - decent combination of winter tread and long treadlife. I've run these and the stock integrities at 55-58 for well over a year and after 53,000 miles on the car - the only issues to report is good FE and a harsher ride.

 

F8L... How do you like your Ecsta's? Do you have any comments or opinions on how they ride or perform?

I had installed 215/45-17 Kumho KH16's but recently hit a nasty NJ Turnpike pothole which blew out one tire and bubbled the one behind it. (I was running 42/40 for tire pressure.) Because I couldn't get replacement KH16's in the same size anywhere locally, I settled on the ASX's. (Yes, I'm running ASX's up in front and the KH16's out back.)

TIA,

C

 

The ambient temperature increase you describe is well within the safety margins of modern tires. If unsure, you can always check it (cold) on the warmer days and release a little. I'm basically a max sidewall guy, although I lower it somewhat for others to drive 'normally' for fear the cabin will add rattles. There is a tradeoff with higher pressures but it is not safety. Anything within max sidewall or a bit more will give better FE, better handling, and a harsher ride.

 

Right you are! I'd like to change my answer:
If you're worried about tires exploding and killing you, there are WAY more likely disasters awaiting you every time you go for a drive. And most of them are even easier for the driver to control/eliminate than even checking the tire pressure. There's no question that a driver is more likely to have a serious "situation" due to gadgets/distractions, high speed and generally not paying attention to his surroundings - then he is to have a tire blow out that's 5 psi over the sidewall rating. Where's the outrage and concern over these other more likely tragedies-waiting-to-happen?

 

The ASX's (215/45/17) KILLED my mpg to the tune of about 4-6mpg but I feel some of that loss is due to the fact they are 17"s and wide ones at that. They perform excellent in the handling department and they are an excellent looking tire. I press the Prius pretty hard on most corners and I feel like the car will roll over before these tires actually lose traction. lol

Right now I am not seeing any LRR tires in our 17" size but Nokian does have their V series and they list them as LRR. Depending on price they may be worth a try. I'm really liked my i3s in the 15" size and people rave about the WR series.

Nokian V

 

Hey guys I have a quick question. Last night after inflating my Avids to 40psi all around, this morning after I drove about 6 miles, the psi was around 41psi which is above the max sidewall rating for the tires. I doubt that it's a big deal, but as my trips get longer should I be worried about the psi raising about the max sidewall limit while driving or no? Thanks for your input. Appreciate it!

 

At my dealers "New Toyota Owner Appreciation Event" last night they talked a bit about tire inflation strategies. And I learned a few new things I didn't know before.

1. The TPMS alerts when ONE tire (inlcuding the spare) drops signficantly from the others. If you were to deflate the tires evenly, the TPMS would not alert.
2. When checking your tire pressure, make sure you check the spare which is also in the TPMS alert system.
3. The spare tire has a higher pressure than the other tires. Likely because it doesn't get checked as often as it should- so by over-inflating it most users are more likely to have a useable, non-flat spare when they need it.
4. Even though the Owner's Manual says to check your tire pressure weekly (or is it every other week?) owners NEVER do that. That means they typically only get the tire pressure checked when it comes in for an oil change or tire rotation. So, with this in mind and because it's very bad for a lot of reasons to have under-inflated tires (wear, FE and safety issues mostly) the service department typically over-inflates the tires by a bit (I think he said by 5psi). So, instead of coming in with tires running at 26 psi every six months, they're up around 31 or so instead. If a dealer's over-inflating a tire slightly, I doubt there's a real safety issue in doing so.

Hope that helps!

 

Max psi (or any psi) is a cold measurement. Warm tires will increase nominal psi, but that is known when the cold psi is established.

 

Ahh ok I see now. So 40psi cold should be alright then, and it's normal for the psi to increase slightly with driving. Even when it's slightly above the max sidewall pressure. Should I be worried? Keep the pressure where it at or lower it? Thoughts?

 

Are you sure you aren't looking at the maximum pressure permitted to seat the tires on the rim? I don't have Avids, but the industry standard for maximum pressure to seat the tires on the rims is 40 lbs. Most of the tires I have seen have a maximum pressure of around 50 psi.

Either way, you are supposed to check the pressures when cold. They obviously know that pressure will go up as the tire warms up.

 

Yea, I'm pretty sure because it says "maximum sidewall pressure 40psi" on the side of the tire. Thanks for the additional information, I think ill just keep it at 40. I doubt my tire will explode. Let's hope it won't anyway. I just hope I don't hit a pothole and it blows on me. I doubt that will happen either unless the tire has excess wear on them alreay. Input?

 

If you want to run max sidewall, it is done by inflating to that when cold, knowing pressure will increase during operation. Tires at max sidewall are less apt to suffer damage from potholes than those at lower pressures. Higher pressures put more of that energy into the suspension components and the bones of the driver.

 

Thanks ksstathead and Joe166 for your input regarding my tire pressure question. Looks like I had it right all along, I just wanted some additional assurance. Lets just hope my suspension doesn't get beaten up too bad with 40 PSI. My body can handle it, haha.

 

I have to ask, since there are so many experts: if higher pressure is so wonderful, why are tires not manufactured to the higher pressure?

 

Basically because high pressure makes the ride rougher. For auto enthusiasts who like the "feel of the road" this is a good thing--at least to a point. For folks who like luxury, this is not. Many people can feel the difference even between 32 psi (factory rec) and 44 psi (max cold sidewall pressure) in the Prius.

You can see something like this among bike riders too--fat, low pressure tires for little kids and slow riders (e.g., me)--skinny, very high pressure tires for the serious tourers and racers (mountain biking is different).

 

thanks, but that's not exactly what I was asking. If there is a market for high pressure tires, and particularly with the tires marketed as fuel efficient, why aren't they designed to run normally at 40psi? Or higher? Sounds more like a limitation of the rubber compounds and tire physics.

 

More likely it is a problem of cost and weight. There are plenty of tires out there that have max inflation pressures of 50psi and more. Look at truck tires which are designed to run at 60psi+ under load. My 17" tires are rated at 50psi as well.

 

I asked Michelin, and their response was:

Which kind of surprised me, but hey, they've been in the tire business for 100 years. So overinflating is a bad and unsubstantiated practice that is unsafe and essentially worthless. Rather like extending synthetic oil to 20k.