Jake Ok

Driver only - running F34 R38
When I ran them at recommended specs the middle of tire wore off real quick.

BruceP

Really? Stock tire and rim widths? If so, I'm surprised. Mine couldn't wear more evenly if I put them on a lathe. I actually considered this a side benefit of running recommended pressures.

roperin

I have Sport Classic 19's on a 996 Cab, with 295 rossos on the rear, it's like a brick with 36/44 and just me in it so i went to 33/37 and it amazed me the difference, I cannot tell if the handling is any different, I don't think so, anyway i don't drive like an idiot on the road, but the car rides perfect, we love it. I'll tell you more when i get the OE shocks rebuilt.

03996

I asked this question many moons ago and more or less got the answer of "do what Porsche says".........however, what the engineers reccomend is surely a compromise of many things over which they have little or no control, not least of which is 1) covering their butts from inexperienced drivers taking the car from zero to flat out in just about any kind of driving condition, 2) trying to optimize tire wear, 3) general tire prformance.

I always believed that the correct pressure for any given general road driving will result in a pretty equal temperature reading across the full width of the tread. If the outer is much hotter than the center, chances are it's underinflated, opposite being true if the center is hotter.

So tuning for optimal pressures requires the use of a good temperature sensing device. Once set for a level temperature playing field, the ride is simply a result of that action.

And, I agree that at 44psi, the ride is bloody harsh and am surprised Porsche would engineer the thing like that if they had a choice.......which because of my item 1, I don't think they do, after all, they certainly don't want to have a tire explode on one of their cars at 170mph, just because some hooray-henry-twit has no idea about the requirements of high speed driving and left the tires too soft for that and the thing overheated and blew!

Best regards

Les.

peterbigblock

The recommended tire pressures in the manual (and on the fuel-filler door) are for a fully loaded car (which is about 730 lbs total payload). With one 200-lb. person in the driver seat, the 36/44 will feel overinflated and harsh. I run 30/35 fr/rr cold pressures for everyday driving using Conti DWS 18" tires in stock sizes (225/40 and 285/30). I find this produces excellent tire wear, consistent tire temps, and a good handling/ride compromise. There's nothing wrong with the recommended pressures. But they're not gospel, particularly for a car with 530 fewer pounds on board than max. capacity. That's why the 997 gave two different pressure recommendations for different load scenarios. As always, of course, YMMV.

5CHN3LL

I prefer to run a couple of PSI lower than the "book" says, measured cold, to improve grip. I do run an aftermarket TPMS system - running with under filled tires can be treacherous, especially with low-profile tires like mine. A nice by-product of the TPMS is that it alternates between PSI and degrees Farenheit, so I can get a better idea of what the tires are doing, what it takes to get them up to temp, etc. Sorry to sideswipe OP's thread with this info, but it really is a good piece of safety equipment.

nymart

5CHN3LL...can you please PM me with the name/model of the aftermarket TPMS you are using? Having trashed one tire last year because I didn't realize it was a little low, it's the one mod that I'm really looking to do right away. TIA

5CHN3LL

This is I use - the Orange Electronic P409S. I didn't PM in the event that someone else might find it useful. The Amazon reviews are mixed, but I have had excellent success. Discount Tire installed the stem units for $75 total (and I think later realized they should have charged more).

5CHN3LL

If your rear tires wear evenly, you or someone previous to you must have had the negative camber reduced.

pontifex4

+1 on running them softer and checking the pressure frequently. I run around 33f/36r psi (on my gauge) cold on the street with Pilot Super Sports, and the ride with M030 is surprisingly good. Some of that is definitely the tires, though. My winter Bridgestones aren't as compliant.

6ta1

you have to realize that your "ideal" tire pressure will be dependent on the load index of your tires.

For ex my front Michelin PS2 have a load index of only 87 so I have to inflate them to ~40psi to get even with the stock set up.

It is very likely that a lot of the people complaining of harsh ride at 44psi in the rears have tires with a higher load index

a good link to read (and there are many others)

http://dealer.falkentire.com/templat...760&height=400

Spokayman

This is interesting and I am sure it is meaningful.
But, using this chart and the fully loaded weight of my C4 cab tip (weights per owners manual), I would only need 26 PSI front and less than 30PSI rear for the 92f and 97r load range of my Conti tires. Unless I am using the wrong weight figures?
So it seems like there is more to it than just the load range.
Does anyone know what the factory load range(s) were for our 996s? Maybe that's the comparison that would be more relevant than simply the total load or weight on each tire.

Melb-Mike

Very interesting to me as well being new to Porsche. My Z06 Vette weighs 3145 lbs, weight dist is nearly 50/50 and uses 30 psi all around, 285-45 19 on front 325-30 19 on the back. My 996TT weighs approx 3550 lbs, has about 34/66 weight ratio but tire press is 44 on the back tire ???? Seems high but I remember when we ran the Daytona Rolex track with the Audi Club with my Z06, they were warning all Porsche 911 owners to bump up their rear tire pressure, especially the right rear, to keep from shredding it off the rim. They recommended 50 psi. We bumped up our Vette tires (Hoosier R6 race slicks) to 38 psi for the same reason.

The year before, they said two Porsche 911's wrecked as a result of right rear tire failure. The year we ran (2010) no wrecks other than a Mustang sheared in half after 3 days & over 400 miles of tracking. So tire pressures are likely even more important to a rear engine car with good power.

ladius

My friend has a Lexus LFA that had a flat tire replaced at the dealer. When he drove it, he said the ride was terrible. We checked the tire pressure on the new dealer-installed tire and it was at 42 psi. I don't remember what the other tires were at exactly but they were all pretty high, relatively speaking, above 35.

In the LFA manual, it said something along the lines of if you are traveling under 150 mph (or some insanely high speed), keep tire pressure at 32 psi. If you are going above 150 mph, inflate to 42. Perhaps wanting to limit their liability, the dealer may have inflated the new tire to 42 psi, uncertain if the owner will drive the car regularly at 150 mph or greater.

So it seems manufacturer recommended pressures may be a combination of what Les wrote below. I'm just throwing this in there as food for thought. Ultimately, we will all do what seems best in our experience.

(ps - we lowered the psi to 32 all around)

Cuda911

How do you like my Pirelli P-Zeros after less than 1,000 miles on 'em? Put it up on the lift today for an oil change and saw this: