Help w/ tire pressure - too high?

Spilchy · 04-16-05, 06:59

My brother bought a new VW Jetta wagon. I checked the tire pressure straight from the dealer and (according to the specs. on the driver door jamb) the fronts were fine and the rears were low.

Interestingly, all 4 were at the same pressure because the spec. on the door jamb says 44 psi for the rear! It is currently at 35 psi - 9 points off.

I was a bit shocked at the high number because the max. pressure on the Michelen tire is 51 psi.

With the summer here and with tire expansion, is filling it to 44 psi dangerous?

My brother is a painting contractor and loads the back of the wagon with materials sometimes if he isn't using the truck.

What do you guys think? Should I fill it up to 44? If not, what do you recommend?

Thanks, any help is appreciated. I want him to be safe, maintain good gas mileage and proper tire wear.

Setec Astronomy · 04-16-05, 07:02

That's really high--but if the placard says that, and the tire is rated that high (51), you should do it. Especially if you are putting a load in the vehicle, you want the tires to be at the proper inflation pressure.

MidlifeCrisis · 04-16-05, 07:16

44 psi sounds really high. I know on my V70 it gives two pressures one for using with big loads and one for normal driving (39 for loaded and 35 for normal). I ran my car at 39 for the first 6 mos and found the ride was bit harsher, and the when I had the winter (AS) tires put on my tire guy said they were wearing a bit too much in the middle (a sign of overinflation). Now I keep the tires at 36 and the ride is nicer and the tires are wearing more evenly.

If I were you I would ask this question at:

http://forums.vwvortex.com

and see what the other Jetta owners are running their tires at.

HTH,

Pat

uconn1150 · 04-16-05, 08:00

If the doorjamb sticker says 44, then inflate to 44--Especially if the tire says the max is 51.

I always fill my tires to the max pressure -10%...51-5=46...then there's always %error, so you should be fine.

The problem that arises is when replacing tires people don't pay attention to little details like load. So they purchase a tire where the max press would now be 44...not too safe/reliable.

kompressornsc · 04-17-05, 01:34

I tend to run mine high, I get too much body roll resulting in push if I run the front at recommended (28). I go to 32.

Along these same lines...

If you filled your tires last when it was cold out, check them now! I put mine at 32 when it was about 15 degrees out. Checked them last weekend when it was 75 & they were @ 38 (cold).

Accumulator · 04-17-05, 05:26

Spilchy- Dangerous? No. Correct?

Be sure you're not reading the "fully loaded" inflation pressure. Our Audis have two pressures, one for normal use and one for when the cars are full of people and luggage. The "fully loaded" psi is in the forties, BTW.

You can see how the car handles and how the tires wear and adjust accordingly. And remember that even wear doesn't always mean the best handling either.

But there's nothing dangerous about running a pressure that far under the tires' maximum. IMO it's usually even safe to run a pressure far in excess of the stated max.

Spilchy · 04-17-05, 05:37

Thanks guys

I know about the two types of readings - loaded and normal. I'm a little smart

However, there aren't two readings, just one - that's the thing.

I'm used to keeping my tires at 33psi. I've never had a wagon before.

Accumulator · 04-17-05, 05:42

Spilchy- Heh heh, sorry to have pointed out the obvious

Remember that wagons are often quite heavy in the back end- all that glass can weigh a lot more than the sheetmetal of sedans.

SHICKS · 04-17-05, 05:51

Always check and adjust when the tires are cold. I run my bmw tires fairly hight I think 42 for the rear, promotes understeer, but is safer in emergency handling.

Steve

Quote:

Originally posted by Spilchy
My brother bought a new VW Jetta wagon. I checked the tire pressure straight from the dealer and (according to the specs. on the driver door jamb) the fronts were fine and the rears were low.

Interestingly, all 4 were at the same pressure because the spec. on the door jamb says 44 psi for the rear! It is currently at 35 psi - 9 points off.

I was a bit shocked at the high number because the max. pressure on the Michelen tire is 51 psi.

With the summer here and with tire expansion, is filling it to 44 psi dangerous?

My brother is a painting contractor and loads the back of the wagon with materials sometimes if he isn't using the truck.

What do you guys think? Should I fill it up to 44? If not, what do you recommend?

Thanks, any help is appreciated. I want him to be safe, maintain good gas mileage and proper tire wear.

Prometheus · 04-17-05, 05:56

That is really odd. But I would try it and see. If it you dont feel comfortable with it, you can always change it. BTW, when i was looking at my door jamb today, it actually said to ADD 4 more PSI in warmer temps, so i wouldnt worry about it expanding that much in summer.

HRP · 04-17-05, 05:58

I'd also check the owner's manual; but generally the recommended pressure on the door jam is on the "low" side to keep the ride softer. Whatever you settle on, watch the treadwear pattern. Too high and the tread wears at the crown or center of the tread; too low and it wears on the sides (inside and out) of the tread. It should wear evenly. The Michelins (Pilot Sport) on our Lexus are rated to 44 lbs; Lexus recommends 30, and I run them at 36 with better handling, a stiffer ride, and even treadware for 45k now.

Setec Astronomy · 04-17-05, 07:32

Quote:

Originally posted by kompressornsc

If you filled your tires last when it was cold out, check them now! I put mine at 32 when it was about 15 degrees out. Checked them last weekend when it was 75 & they were @ 38 (cold).

Not to open up a can of worms...but I have the SmarTire system in one of my cars...this system is referenced to 68 degrees F. That means that if you program in the proper tire pressure at room temperature, it will calculate how much lower it should be at say, 15 degrees, or how much higher at 100 degrees, and considers that to be the correct pressure. When I realized that this was telling me I didn't have to seasonally adjust tire pressures (which is what I have been taught all my life) I said "hold the phone!" and emailed them.

The reply from the SmarTire engineer explained their philosophy...which is a whole long thing...but amounts to if the 68 degree pressure is right...your tires will appear (by the conventional wisdom) to be underinflated when it's colder than that, and overinflated when it's warmer--and that's OK, according to them.

Just telling you what they told me.