Prius Tire Pressure Problem

No problems here. You say recently, how recently? with the temperature dropping, it's likely that is a factor in lowering the tire pressure (the same amount of air at a lower temperature takes up less volume at a constant pressure, or less pressure at a constant volume).

You say "had them checked"... If you're paying for someone else to check them, then don't bother! instead, head over to your friendly neighborhood auto parts store and spend 5-10 bucks on a tire pressure gauge, and check them whenever you like. Simply remove the cover on the valve and press the gauge to it and see a reading! While you're at it, you can also pick up a 12V compressor for fairly cheep, which saves you from having to find a compressor at a gas station. Also, you should always fill/check the tires when they're cold (ie haven't been driven for several hours).

 

About 2lbs per week. Check them every Sat morning and top them off. 41 front 39 rear. Hydro edge tires 195 65 15. still 49.85 mpg after 12k miles.

 

<div class='quotetop'>QUOTE(Chuck T @ Oct 5 2006, 01:57 PM) [snapback]328558[/snapback]</div>

Aluminum is a softer metal which can in some cases develope microscopic "holes" (actually a series of pores) but if all your tires are doing that it is probably environmental. (variances in temp or driving patterns etc.) You could try getting your tires filled with Nitrogen blend (larger molecule, less chance to escape through "holes".

 

<div class='quotetop'>QUOTE(Artemis Wiz @ Oct 5 2006, 02:13 PM) [snapback]328645[/snapback]</div>

Yes, I *always* fill my tires with a blend of 78% nitrogen plus a few other gases.

 

<div class='quotetop'>QUOTE(jbarnhart @ Oct 5 2006, 01:22 PM) [snapback]328649[/snapback]</div>

Personally, I like 79% Nitrogen... with 20% Oxygen for flavor and coloring! :lol:

Of course, once in a while I top off in Los Angeles... and then I only get 19% Oxygen...

<div class='quotetop'>QUOTE(John in LB @ Oct 5 2006, 01:35 PM) [snapback]328655[/snapback]</div>

Seriously, if you are losing tire pressure, the cooling weather will make a significant difference and will lower your tire pressure by several pounds.

If the pressure is lower on all 4 tires about the same amount - then its probably weather or a bad measurement (now or the last time.)

However, if it is lower in only 1 or 2 tires... start looking for a small nail that is still in the tire. Do a very careful inspection (I like to do it up on a rack where i can spin the wheel and pop every one of the little rocks that are stuck between the treads - what looks like a rock can be the head of a nail...)

 

Mine all lose some air, maybe 3 to 5 lbs a month. I add air regularly to put them all 5 lbs above door sticker. I thought maybe it was the GY tires but see that ralph b has the problem with HydroEdges so it must be the wheels. Maybe the lighter wheels are also more porous. I've never had to add air as often with previous vehicles/tires/wheels. It hasn't been a major inconvenience yet so I have been living with it. I did check all tires when I last rotated, but with all 4 losing air I didn't expect to find anything. I do know someone that had a problem similar with their Chevy w/alum wheels. A tire dealer removed the tires, coated the inside of the rims with some sort of sealer and remounted the tires. That was about two years ago and no air lose problems since. I don't think I am ready to have anyone do all that and take the chance of scratching the wheels, changing the balance or damaging the TPWS transmitter/valve stem.

 

Same here. My prius losses tire pressure more frquently than my previous car ...i lose around 3 pounds over a month .....On my previous car i dont remember many instances when i had to top up the tire presssure.

 

I have owned several cars with aluminum or alloy wheels and have not had a problem with leaks. I check them weekly and normally need to add air every couple of months or so, more often this time of year due to the weather getting colder.

 

I drive mine 100 miles per day. The digital meter says my pressure doesn't change over at least 2 months or more.

I always check my tires the same way, whch is cold + 3 minute drive down to the local gas station's air pump.

 

Your aluminum wheels are painted, and shouldn't loose air as the paint seals defects in the aluminum. If they do they are defective, even if they claim it's normal because they all do. As stated above, I've never had trouble with aluminum wheels loosing air. Tires, yes, usually due to metal objects embedded in them.

If my Prius wheels loose air as reported here, I'm sealing or replacing them! Having properly inflated tires is kind of important!

 

<_< 2+ years = no problems with loss of tire pressure.

Rather than depend on service station pumps (at 25¢ per tire - and down on my knees on their less than pristine drive), I purchased a 12v pump from WalMart and ordered an accurate analog gauge from Racer Parts Wholesale. Keep them in the back left storage compartment and keep my tires to my chosen 40/38 psi. This also serves our other Toyota (1996 Camry).

I usually check them monthly, sometimes more often if the ambient terperature changes a lot. It's rare for them bo be more than about 1 or 2 psi off in a month.

 

<div class='quotetop'>QUOTE(John in LB @ Oct 5 2006, 04:41 PM) [snapback]328655[/snapback]</div>

Also, you might check the tightness of each valve, which is in the center of each valve stem. There's a little tool which tightens them; if they're a bit loose, you'll get some air leakage that way.

Try unscrewing the valve stem cover and putting a bit of spit in the valve stem; if you see bubbles emerging, you've found the air leak.

 

Hmm, just mulling over the comment that the nitrogen gas has smaller atoms than air, which is mostly nitrogen...can this mean that my tyres are in fact nitrogen accumulators. Sorry, couldn't resist.