Toyota Prius Forum banner
1 - 20 of 36 Posts

·
Registered
Joined
·
127 Posts
Discussion Starter · #1 ·
The car hasn't been driven in 24 hours, sitting in the garage all night. Do I check tire pressure now? If it is low and I drive in the 95-100 degree heat for 10 minutes to the station to add air, how much do I add? Won't the drive in the heat have inflated the tires somewhat? How often should tire pressure be checked? Seems like everytime I do, air leaks out of the tire. The toyota dealership is much too far away to take the car in for just this, but I think my mileage has dropped since I bought the car in late May, and I wonder if it could be tire pressure. Thanks for any advice.
 

·
Registered
Joined
·
7,161 Posts
You are supposed to check the tire pressure when cold. When checking the pressure, minimize the amount of air leaked. This can be tricky depending on the person and the guage.

If you need to drive somewhere to put air in, note the cold pressure, then calculate how many more PSI you need. Then when you get to the place you can add air, add that many PSI to the hot reading. You would need to do this individually for all 4 tires.

Ex: Cold reading is 32PSI. You want the tire to have 40PSI. That means you need an additional 8PSI.
You drive to the gas station. Now the tire reads 34 PSI. You add air until it reads 42PSI. Repeat for the other 3 tires.

If you lose pressure within a week, you probably have a slow leak you need to keep an eye on. If the drop is noticable in one day, you should have the tire looked at. Of course you need to account for changes in temp. However if only one tire drifts significantly compared to the others, then that tire is suspect.
 

·
Registered
Joined
·
991 Posts
Also depends on how high you want your tire pressure. Toyota recommends a 35/33 I believe.. some inflate 42/40 (like Dan).. some go higher, some stay in between..
 

·
Registered
Joined
·
7,161 Posts
Well I do 40/38, but I don't worry much about the tire temp. I've found it doesn't change much anyway hot or cold.

Right now though I don't care. Toyota dealer wanted to change only 2 tires for the free replacement, but I am waiting for them to change all 4, then see if goodyear will trade them for ComfortAssurance since the dealer won't trade up. They will only have 1 mile on them when I do.
 

·
Registered
Joined
·
991 Posts
Well, its the "max" pressure issue when the tire gets hot (44PSI) and also the "comfort" issue at the higher pressure levels. Its like me at 36/34 I can hit bumps and barely feel them.. at a higher PSI (say 42/40) you'll feel them more.. and be less comfortable.. but yet attain higher MPG. It makes me wonder if the people that post that at 90mph their car felt "unstable" had their PSI at higher-than-recommended setting (44/42?+). I've heard here of people doing 50+ too.. right, Dan?
 

·
Registered
Joined
·
7,161 Posts
I think the 44PSI max is when it is cold.

The ride can be firmer when pressure is raised, but that shouldn't change the stability of the car if the suspension/alignment is right.

I don't know if anyone has put 50PSI in the Integrities. I certainly wouldn't.
 

·
Registered
Joined
·
127 Posts
Discussion Starter · #7 ·
DanMan32 said:
You are supposed to check the tire pressure when cold. When checking the pressure, minimize the amount of air leaked. This can be tricky depending on the person and the guage.

If you need to drive somewhere to put air in, note the cold pressure, then calculate how many more PSI you need. Then when you get to the place you can add air, add that many PSI to the hot reading. You would need to do this individually for all 4 tires.

Ex: Cold reading is 32PSI. You want the tire to have 40PSI. That means you need an additional 8PSI.
You drive to the gas station. Now the tire reads 34 PSI. You add air until it reads 42PSI. Repeat for the other 3 tires.

If you lose pressure within a week, you probably have a slow leak you need to keep an eye on. If the drop is noticable in one day, you should have the tire looked at. Of course you need to account for changes in temp. However if only one tire drifts significantly compared to the others, then that tire is suspect.
Thanks, I did all this, but was still kind of confused when I got to the station because the notes I had made myself weren't clear, and that air compressor only stayed on for so long. Is it the higher number in the front or back? Also, when I did check the tire pressure cold I noticed that my Integrity tires were at 28 and 25 in the back and 29 in the front. I'll check again tomorrow and make sure I didn't overfill. It is really really hot here...triple digits. My MFD display read that I was getting a little more than 45 mpg, but when I filled up, the pump stopped at 6.93 gallons and I had driven 343 miles, so that works out even higher, to 49 plus mpg I figure. I am cool with that, as it is mostly city driving.
Here is another question: as I was pumping the gas, about half way through the nozzle started sounding as if it were pulsing like a heartbeat. I don't know if that is because it was delivering air to the tank, or...? Anyone else ever have this experience? I'm guessing it sounds so different than another car's gas tank because it is a bladder. :?:
 

·
Registered
Joined
·
991 Posts
The pulsing is the pump.. pumping gasoline into your car. Some gas stations I've run across sometimes have this "clicking" noise that is almost like a pulse.. which I'm thinking is what you're referring to.

29 PSI is low.. are you sure you didn't mean 39 PSI? The front tires are usually set 2 PSI higher than the back..
 

·
Registered
Joined
·
127 Posts
Discussion Starter · #9 ·
Phish Phood said:
The pulsing is the pump.. pumping gasoline into your car. Some gas stations I've run across sometimes have this "clicking" noise that is almost like a pulse.. which I'm thinking is what you're referring to.

29 PSI is low.. are you sure you didn't mean 39 PSI? The front tires are usually set 2 PSI higher than the back..
I used a little battery operated "accupressure" tire pressure check, and it said the numbers I quoted earlier. When I filled up at the station, the tire gauge attached to the air pump read maybe a few pounds more than that, but not much. I was surprised it was that low, because they didn't look too low, although I had noticed what I thought was a big drop in mpg in my last fillup before this one: 278 miles and the tank needed 10.34 gallons to fill up! The driving before that poor mileage had a lot of faster highway sppeds, 70 plus by my husband who doesn't know about the PNG method.
 

·
Registered
Joined
·
127 Posts
Discussion Starter · #10 ·
tire pressure, etc

This was my first time to check the tire pressure since I got the car on May 24th.
 

·
Registered
Joined
·
736 Posts
I would suggest checking the tire pressure at an absolute minimum of once each month. Every two weeks would be better. As Dan says, check them when cold, after the car has sat for at least a few hours following any trip longer than a mile or two. Sounds like you have a good guage, so just make sure it is lined up with the valve before pressing it on to avoid losing air. Dan also has the right idea in figuring how much you need to add, but you need do it with only one tire, since they will heat up at about the same rate. If you drive less than a mile to the air source, you probably won't notice much increase. Then just add to that first tire whatever you have to, and set the others based on the new reading, adding or subtracting 2 pounds depending on whether that first tire is on the front or rear of the car. BTW, in my household, I don't think my wife has put air in a tire in nearly 41 years. That is one of my responsibilities. Explain pulse and glide and tire maintenance to hubby! You will get better mileage out of the tires as well as the gas tank. Also, those guages on the service station hoses are banged around and otherwise mistreated, so you can't rely on the pressures they show. Good luck.
 

·
Registered
Joined
·
591 Posts
To do your tire pressure, -On the way home-, fill the tires about 5 PSI higher than you want (unless this exceeds the max. pressure on the sidewall - use that number if it does).
Next morning, check the pressure before the sun shines on the tires, and deflate to the pressure you want. No pump needed. You get "cold inflation pressure", so everything is good. No math needed, other than adding 5 PSI to your desired pressure.

You will find if you use a higher pressure like Dan, the tires will operate cooler and will not increase pressure as much from driving as if you use the "recommended pressure". I suspect the centre of the tread will wear faster than the edges though, if you use a higher pressure than that on the label on the door post. It may take 10,000 mi. before you notice that.

Perhaps Dan has been watching for this?
 

·
Registered
Joined
·
7,161 Posts
Slightly overinflating then adjusting down when cold is certainly another way to do it.

Pressure in the 20's is WAY too low. Keep close tabs on those tires. Front tires get more pressure because they have to support more weight.

Roger, all tires have to be read. You can't be certain that all the tires read the same, as L.L. determined, so each tire may need a different amount of air as compared to the others.
 

·
Registered
Joined
·
1,434 Posts
Little Lamb,
I would like to encourage you to shell out about $50 for a rechargable portable jump-starter/air compressor. I think you'll find it invaluable over the time you have your Prius.

It makes it much much more convenient to check the tires when cold at home as you have the pump right there, can take all the time you want to get the pressure set where you want it and don't have to do any 'over-inflating' then waiting for them to cool, etc.

Also, b/c the Prius' 12v battery can die when unused for a period of time or if the hatch is inadvertently left ajar you have a very convenient way to jump start it. I bring my pump along when I'll be leaving the car at the airport for a trip or on any cross country trip so that I can reinflate a flat for long enough to get a repair.

Many of these units also have 12v outlets that you can plug other devices into, they have flashlights built in so you can see what you're doing in the dark, etc.

Money very well spent IMO, and well worth it to avoid the gymnastics you're going through just to get proper tire pressure.
 

·
Registered
Joined
·
216 Posts
Even better than shelling out $50. for a rechargeable air pump, spend less and get a good floor bicycle pump. In addition to have a nice pump for your bikes you will get some exercise while saving electric to pump up your car tires. It works for me.

PA P
 

·
Registered
Joined
·
127 Posts
Discussion Starter · #16 ·
PA Prius said:
Even better than shelling out $50. for a rechargeable air pump, spend less and get a good floor bicycle pump. In addition to have a nice pump for your bikes you will get some exercise while saving electric to pump up your car tires. It works for me.

PA P
I do have a bike pump, but I don't know how good quality it is.
Thanks everybody for their advice. Another question: my husband thinks that the maximum tire pressure on the tire (I think it is 44 on those Integritys) is when they're hot and I am being unsafe if I fill them more than 30 lbs Psi when cold. Do the tire manufacturers or Toyota have a web site that definitively says one way or another which it should be? :?:
 

·
Registered
Joined
·
1,434 Posts
LittleLamb said:
PA Prius said:
Even better than shelling out $50. for a rechargeable air pump, spend less and get a good floor bicycle pump. In addition to have a nice pump for your bikes you will get some exercise while saving electric to pump up your car tires. It works for me.

PA P
I do have a bike pump, but I don't know how good quality it is.
Thanks everybody for their advice. Another question: my husband thinks that the maximum tire pressure on the tire (I think it is 44 on those Integritys) is when they're hot and I am being unsafe if I fill them more than 30 lbs Psi when cold. Do the tire manufacturers or Toyota have a web site that definitively says one way or another which it should be? :?:
Due respect to your hubby, but he's wrong. The tire pressure is the maximum cold pressure rating of the tire. The heating of the tire due to ambient temp changes and tire use is anticipated with that number.

Your COLD pressure should be at the OEM rec. numbers at a minimum and many/most of use use at least 42f/40r to help tire life and FE.

BTW, it doesn't really matter if the quality of your tire pump is great or not. If it works then that's fine...just be prepared to sweat!
 

·
Registered
Joined
·
1,434 Posts
btw, if your tires ever show 30psi they are underinflated. You'll have definate impact on FE and will definately wear the tires faster. You will not be in any kind of unsafe condition if you're at the OEM rec. pressure up to the tire's max pressure of 44psi.
 

·
Registered
Joined
·
22 Posts
If anybody needs a compressor, I have been using a 12V model that I found at Sears for $20 about a year and a half ago. So far so good, even with frequent use and filling to pressures in the 44psi range. It's well worth the investment, and your tires will thank you!
 

·
Registered
Joined
·
127 Posts
Discussion Starter · #20 ·
Thanks. What about David Beale's suggestion:
"I suspect the centre of the tread will wear faster than the edges though, if you use a higher pressure than that on the label on the door post".

Also, PS to Phish Phood: back to that "clicking" vs "pulsing" sound I heard at the station yesterday: I know what the "clicking" sounds like, have heard that for years, but this was the first time I have heard anything like this. It sounded more like the gasoline was glopping out in between gulps of air. Really, it was like some sci-film and I was holding a beating metallic heart in my hand! I almost told the young woman behind the counter at Valero (first time I have gotten gas there...any opinions on its fuel or company practices in general?), but she was overwhelmed with customers and seemed a little unsure of herself anyway. Besides, that description might not have been well-understood... :)
 
1 - 20 of 36 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top