We're always talking on here about making sure that the psi in our front tires are about 3 psi higher than in our rear tires to combat "understeer", since our cars are FWD.

Well, my wife drives a 2005 Jetta GLI. It's also FWD. I just noticed today that on the D/S door jamb of her car that the recommended tire psi is 36F/42R! Not only does the higher recommended rear tire pressure confuse me, but 42 psi is a very high recommended psi, and the maximum recommended pressure for the tire is 50 psi (they're Goodyear Eagle F1 GS-D3's).

Can anyone shed some light on the reason for this?

Thanks!

 

my rule of thumb is: cold tire pressure is 80% of maximum tire pressure

sometimes you can't go with door jambs because those are for factory tires. I don't think Jettas came with GS-D3s from the factory did they? If so, then don't bother going with the door jamb....

 

Actually, the GLI did come from the factory with the GS-D3's. I was surprised, too, but since it is the sportiest model, I guess they put them on there.

 

I usually run my tires 4-5 psi over recommendations for better handling and MPGs

 

You should abide by the label inside of the driver's side door frame. Those are the numbers you want to use.

For example. My '04 manual TL calls for 35 pounds in the front and 32 in the rear, while my '05 automatic says to use 32 pounds all around. Since there is only a 1% difference in weight dispersion from front to rear between a manual and an automatic, one would have to wonder why such a difference in the front tire pressure. It's due to the suspension tuning on the manual versus the automatic.

Your best bet is to go with what Acura recommends. Also, running the tire pressure too high will both shorten the life of the tires and cause uneven wear patterns.

 

I read that the recommended pressure is what the dealers give you so that you'll get the softest ride while still being safe. They were saying that you could go a few pounds up to get a sportier ride without being detrimental to the tire. On my SI it's recommnded to run 32, I'm running 36 and noticed a slight improvement in the feel of the car. The Max is 42 PSI I believe.

Should I drop back down to 32?

 

The recommended pressure is the factory's compromise of ride softness + handling.

If you can live with a slightly harder ride, pressures between recommended and 40 psi (measured with the tires cold) are fine for daily use.

I'd keep the Psi @ 36 if the feel is preferable- I use 37F/34R on my TL although recommended is 32F/R.

 

I appreciate everbody posting, but I'm still wondering why the GLI's recommended tire pressure is 36F/42R, when it is a FWD car!?

 

I'm not sure why they suggested that.

My Audi's PSI recommendations are pretty high too.

 

Speaking of which, where are the pics?

 

The GLI's tire PSI should be affected by the damping/spring rates and suspension set-up as well (which also affect handling characteristics such as oversteer and understeer). The engineers probably decided on the suspension tuning and ride they liked, then worked on getting appropriate tires and tire pressure to maintain that tuning and ride. However, I don't know enough about the VW to know why the high rear tire pressure in relation to lower front tire pressure- soft springs, low pressure shocks ??

The drive wheels are not the sole determinant of which tires get more tire pressure, and tire pressure is not the car manufacturer's main way to combat understeer.