Tire pressure? How do I determine?

[phillipj]

I have 19's on my car with Dunlop SP Sport 9000 tires. I checked the tire pressure the other day and I have around 25 psi on all four corners. This seemed quite low to me. How do I determine what is a correct pressure? The car is lowered with H & R springs and the ride is quite rough.

Any input is appreciated.

Thanks !

[714dre]

There should be a table in your manual.

I thought it is 36 for front, 44 rear.

[phillipj]

But that would be for OEM tires correct? I think if I had 44 lbs in the rears it would jar my teeth loose :o

These are very low profile tires. I don't see how you would apply the factory reco's to these. Or am I wrong? :huh:

Thanks for your input

[SH-GT3]

I would download the OM for the 997 and see what pressures they recommend for the OEM 19 - obviously if the tire sizes are the same or very close

Edited June 22, 2009 by Anders0n||C4S

[714dre]

good points.. .sorry i missed that.

one thing to consider though: loose teeth, or possibly bent rims...

[phillipj]

Thanks for the replys. I will look at the 997 OM. And I had my wheels balanced and I do Have a slight bend in one of the front wheels. Will be getting that fixed asap.

Thanks again!

[phillipj]

Here is what the 997 manual says for tire pressures. Thanks Anderson :D

Tire pressures for cold tires

Summer and snow tires 911 Carrera, 911 Carrera S

18 inch wheels

front 36 psi (2.5 bar)

rear 44 psi (3.0 bar)

19 inch wheels, partially loaded

(up to 2 persons without luggage)

front 33 psi (2.3 bar)

rear 39 psi (2.7 bar)

19 inch wheels, fully loaded

(as of 2 persons with luggage)

front 36 psi (2.5 bar)

rear 44 psi (3.0 bar

Edited June 22, 2009 by phillipj

[BruceP]

A lowered car on 19" wheels is going to ride rough. It's the unavoidable price you pay, and as another poster said, better your teeth than your rims.

I wonder if it's worth looking into adjusting your shocks? There's a good chance that the damping is adjustable, and you might be able to tweak things a little bit for your driving conditions. Just a thought. Me, I'd put the tire pressures where they belong for the sake of handling and braking and try to manage the ride with the shocks.

[phillipj]

Thanks Bruce.

I was looking at the suspension and it appears that just the springs were changed (previous owner) and the shocks look stock. That is probably why the ride is so bad.

I'm thinking about changing out the shocks but I will have to do some research on what the best choice would be (based on the springs I have.)

I'll put the proper pressure in the tires and see how it feels

Thanks for everyones input on this.

:cheers:

[BruceP]

I was looking at the suspension and it appears that just the springs were changed (previous owner) and the shocks look stock. That is probably why the ride is so bad.

I think you have it sleuthed. :D

FWIW, when I was shopping for suspensions, I looked at an H&R spring/coil-over combination for the 996 (too extreme for me). Maybe you have those springs, in which case matching the dampers will be easy. Not cheap, mind you, but easy. Good luck!

[phillipj]

These appear to be the springs I have...

http://forcedfed.com/porsche/springs/h&r.html

Not really in a position to spend a grand on shocks at the moment.

If I do have thse springs I wonder what my options are as far a dampners?

[BruceP]

These appear to be the springs I have...

http://forcedfed.com/porsche/springs/h&r.html

Not really in a position to spend a grand on shocks at the moment.

If I do have thse springs I wonder what my options are as far a dampners?

I'm sure I'll get flamed beyond belief for this, but if you're sure you're still running the OE dampers, I'd consider putting OE springs on it and wait until you can get the suspension mod right. The H&R setup is fantastic as spec'd. But putting lowering springs on a car without matching them to shocks actually hurts handling (and for some slammed Hondas I've seen around here, even safety). I'm sure this is a very unattractive option, but I bet you'd enjoy the car more while you wait for the dream setup. These things don't ride that high.

Anyhow, that advice and two bucks will get you a cup of Starbucks, I guess. Good luck!

[phillipj]

Bruce,

I don't have the stock springs so that really isn't an option (although a good suggestion.) My car would look really funny at stock hieght. I'll do some research and drive carefully until I can get it sorted.

Thanks for your input and I'll let you know what I find...

[514911]

I had an a4 with 19" wheels and 35 tires. Here in montreal we have a lot of bad pot holes and after hitting one with tire pressure on the lower side my tire was busted up. What happens is that your tires if they are too thin like 30-35 with low pressure....when they hit the pothole edge it causes them to be pused against the rim and cut. If you have higher pressure, there will be more resistance and your tires will alst longer. I now run them at 44psi and no problems.....

my .02

[Benjamin Choi]

some of you guys are really old or just have really brittle back bones and teeth ;)

i've been rolling 25 series 19" for 25K no problems, great ride. i guess it's all a matter of perspective. i run the typical tire pressures you guys are listing above. in fact, prob on the high side.

[typhon]

some of you guys are really old or just have really brittle back bones and teeth ;)

i've been rolling 25 series 19" for 25K no problems, great ride. i guess it's all a matter of perspective. i run the typical tire pressures you guys are listing above. in fact, prob on the high side.

i have been running mine at 36 front 44 rear for about 2yrs now and no problems. now my f250 diesel runs at 70 psi on all four. that plus the heavy suspension and the fact that the tires are 10 ply, you need a mouthpiece to drive on some of the streets around here :o

[phillipj]

I'm running 33 in the front and 39 in the rears. Made a huge difference. The ride is rough but car handles much better.

Thanks for all the input

[wross996TT]

I agree with Ben...running 19's for several years and keep fairly high pressure in them...love the ride.