Tire care basic questions

[jaw444]

i never paid attention to my tires on any of my several cars before. The Prius i just got needed a new set of tires so i got some that got good reviews on these forums. I thought that would be the end of it, but when i checked the pressure in the tires, every tire was different, and my understanding is that it's good to keep the front ones the same and the back ones the same, so things are in balance. And the front ones should be a little higher.

I put air in the tires. When i checked them the next day, they were lower, two or three or more pounds lower.

I've been checking them cold, and putting air in after only a short drive of a few blocks to the gas station. Would that make a difference of many pounds?

How much air is it normal for tires to lose in a day?
In a week? In a month?

I have gotten tired of going to dark deserted gas stations to put more air in my tires every night so i want to get a tire inflator/compressor.

Today i got a sears Craftsman one that plugs into the car's power outlet. I haven't taken it out of the box yet. I really wanted one that plugs into the AC in the garage but i couldn't find one at Sears, PepBoys, OSH, or Kragen. They have a couple on Amazon, a Black and Decker and a Bion-aire, which i may order. I wanted to ask forum members about this.

Will it harm my battery in my Prius to use one of these air compressors that plugs into the car 12V outlet? Does it drain the battery?

Do forum members have any recommendations for what type of air compressor/inflator to get?

I got so burnt out on going to the gas station for air every day that i stopped doing it, and i'm just letting my tires be whatever pressure they are, until i have a way of inflating them at home. Today, the front tires were 35 psi and the back tires were 37 psi, even though when i put air in the last time, i had put 41 in the front and 39 in the back. Now, the front is lower.

[timberwolf]

What are you using to measure the tire pressure?

If you haven't already got one, I think it would be a good idea to buy a quality tire pressure gauge. I don't trust the accuracy of the pressure gauges at gas stations (the US may be different from the UK?), and apparently the built-in pressure gauges can be inaccurate on either the foot pumps or electric compressor.

How do you measure the tire pressure?

My procedure is to take a number of pressure readings per tire. If I take a reading and it wasn't what I was expecting then I'll take a second (or third) reading. If when I'm trying to take a reading, I hear more than a brief hiss of air escape as I try to apply the pressure gauge then I know I won't get a good reading. I bought myself a nice easy to handle digital gauge (Michelin Tyre Pressure Gauge | Buy Tyre Pressure Gauge Online - TheUltimateFinish.co.uk), so what I found works may not apply to an analog gauge?

Are you being consistent about the measurements?

I only use the one pressure gauge to measure my tire pressures. If my tires need more air, I'll pump the tires using the foot pump and the analog gauge on the pump isn't good anyway, so afterwards I'll always recheck the tire pressure with the digital gauge.

I also find that I can make a complete bog of it when either fitting or removing the tire pump to the tire value, I sometimes hear too much air hiss out when I am trying to remove the hose. I do wonder sometimes, if I lose more air when I'm checking and pumping the tires than I do to any natural loses?

(PS in the UK I know we spell 'tire' as 'tyre' but as most posters here are probably North American, as the saying goes - When in Rome... )

[jdchappie]

I'll try the 12 volt compressor question.

My 12 volt compressor is about 10 years old. It's slow but it still works.

The guages on 12volt compressors are worthless. Buy a quality digital type and only use it to check your tires.

I leave the Prius on when I air up a tire, but I suggest setting the emergency brake before you begin. If the engine starts while you are by the tires, the Prius will jump gently and give you a good scare.

The compressor won't run down the battery if you're just adjusting the pressure in the tires.

I carry a compressor and a tire plugger. I hate to put the spare on in summer or winter.

Jerry

[richard schumacher]

When the temperature is the same at each measurement tires should lose air very slowly. In Dallas, again when the temperature is within 10 degrees of the previous measurement, mine lose about 1 PSI per month. If yours are losing faster I'd say they have a slow leak. Having those tires re-mounted should stop that.

Driving a few blocks to a tire pump has little effect. Driving more than a mile starts to be significant.

With a $10 digital gauge I don't see a point in multiple measurements of each tire.

[timberwolf]

Originally Posted by richard schumacher

With a $10 digital gauge I don't see a point in multiple measurements of each tire.

As I live in rip off Europe my digital gauge was $30 - it does have a nice weight and feel to it though.

The point of the multiple readings was two-fold, one if you have to pump up the tires you are going to take one reading before and one after anyway as the pump gauges are often different from the digital gauge. When I've got a reading that's not the figure I was expecting, it is more likely that I didn't apply the gauge to the tire value correctly, so I try again.

[andyprius]

2-3 lb loss every day, Wow! Go back to that place and get them remounted. As for proper way to check pressures, I can't add much to other posters. It is all somewhat of a subjective process. Do get a 110VAC compressor, I think I found one in Walmart. I keep a 12VDC unit in each car for emergency only, they are somewhat anemic, I consider them toys. Brookstone has some nice guages.

[N3FOL]

I always check my tire pressure every 2 weeks and they seem to stay within my preferred psi...just adding a few psi here and there and then I'm done. 40 psi for the front and 38 psi for the rear on my Prius. This reminds me, I have to double check my spare tire psi...it has not been done for awhile.

[JimN]

I keep the 12v pump below the deck in the Prius. Always have the car on when using the pump. It may drop the traction battery a bar or 2 but a fully charged battery won't do you much good if you don't have air in the tires. The small cheap units now at Pep Boys do not have good reviews.

[sdtundra]

I have one that has a POS and NEG battery hook up. I think it may have a 12v connector as well, but my worry is hooking it up to battery and draining it.

[jaw444]

Timberwolf--At first i was using a $6 digital gauge i bought at the Toyota dealer. It was very hard to use because it did not easily make seal around the valve, so lots of air squirted out while i tried and tried to get it to measure the pressure. Being ineperienced, i thought this was my problem, that i was just unskilled at doing this, and hoping i would get better at it, but i didn't. After i lost it, i got an Accutire digital gauge that is very easy to read and see in the dark, and it forms a perfect seal around the valve every time, it's almost impossible to do it wrong. I also got a gauge that's a chuck on the end of a short hose (6 inches?) with a round dial on the other end, and it too was much easier to take a reading with than that first one i had. Now i know, not all gauges are created equal. So i'm not sure how that effected my first few days of recording the pressure, the irregularity of the readings, and the leaking of air, maybe most of it was because of the gauge making the air squirt out so much.

I took repeated readings, to make sure they were right, and sometimes they were the same and some times they weren't.

I mostly checked it when the tires were cold, in the morning or after it had been parked for hours. Sometimes i checked it after driving. The first time i put air in, i had driven probably about a mile, trying to find a gas station that didn't have a line of cars to wait for the air, or that had one that was working. So, when i put 41 in the front and 39 in the back, i now have learned that when cold, this would be a couple of pounds or so less, so if it was less later when i checked it again, this would be why it was lower, not that air was leaking.

One thing that set me off taking these measurements and fretting about it is that someone on the forums pointed out to me that the sensors are on the valves so when the installer replaced the valves, my tpms might've been damaged, resulting in tires leaking air (another thread had a couple of reports of that happening)--so this had me very worried that I should've gotten my tires at Toyota instead of Discount Tires, especially after i measured them and the air was way less than what the installer said he put in (37 lbs) and then what i put in, 41/39.

a little knowledge can be a dangerous thing.


tires, tyres, trunk, boot, windshield, windscreen, gas, petrol, tomato, tomahto, all good. :-) Thanks for the suggestions and experience.