996 Tire Pressures

I have a question in regards to the appropriate tire pressures for a 996 on 18" wheels. Some might find it silly, but I consider it quite important so I'll go ahead and ask. The manual says 36/44 psi (cold pressures). A guy in the PCA FAQ section says that this is too much and suggests 31/33 psi. So what pressures should I set my tires at? The car is used purely on the street (for now) and mainly for my daily commuting in traffic, so I would mind giving up some performance for a better ride. P.S. Do you have any skidpan in mind in (or near) the West LA area to get to know how my car feels at & beyond the limit of grip?

I was told 36/42 but I have a rough ride, I am thinking of going lower... for highway to work its fine, but the track guys run a lot lower, trick is to find something that rides good AND allows fro a bit of increased milage for the commuter.. what brand tires, that might help people give you ideas. GL

I use 36/44, but my service tech suggested I go 44 all around for max tire life.

Here we go again! So, Porsche needs to correct the manuals? Let's keep in mind that decreasing pressure, changes several things, like maximum load, temperature, and side wall flexing. Why continuously mess with perfection?

I think we all realize that the factory specified tire pressures are the correct and optimum ones to use. On smooth highways this is great. But here in our local area, especially in the downtown city area, the roads are atrocious with many deep potholes and much broken pavement. I have found the 36/44 pressures results in a harsh, unpleasant ride on such roads. So I tend to use lower pressures such as 32/38 on local roads and increase pressures to the factory specs on highway trips on better roads. Works for me. ....Rickker '99 C4

Widely debated topic... I would suggest Porsche recommneded, or very close, for street use. https://rennlist.com/forums/showthre...=tire+pressure https://rennlist.com/forums/showthre...=tire+pressure

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I have a feeling you might be watching the movie backwards. My father did extensive testing on tire pressure versus load for GM. I saw some of the data, and as the tire pressure went down, the load weight for the tire went down; heat also became more unstable and higher from the sidewall extra flexing. If your town has pot holes, one more reason to stay with Porsche recommended, unless you enjoy bent rims and week tire side walls from low inflation. You also get flat spots from the heat/cold cycles. It is your car, your tires, do as you wish. I just feel sorry for the poor souls that read the Internet for info, and walk away misinformed. In this case, stick to the Engineers recommendations in the manual. John PS section: Tires usually blow from under-inflation (weakening of sidewall from flexing causing heat), not from over-inflation, which simply causes a different wear pattern.

I initially ran 36/44, but the rear tires wore out in the center much more quicly than the edges. The I started tuning at 32/39. It gave a slightly better ride and increased the rear tire life by about 20% more miles.

So I have to admit an error on my part, when I first got the car, I went out and bought a good tire guage. It was my first skills day and I was reading "what to do" to be prepaired.. make sure your tires are inflated propperly I checked the sidewall and pumped them right up to 51 psi... ALL 4 well I thought the car was a bit skiddish... but I knew my tires had the right amount of air, that is what was written on the tire (max preassure) Then a friend told me I was an idiot and suggested the 36/44 and I have been much happier.. I know there is debate about heat, ride and handling. But I think its safe to go with the book, that is IF you read that thing (geesh)

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The reason we run lower on the track is because we measure pressure (hot) when we get off the track. Right after a run when the tires were hot I wanted 36/44 so I had to start much lower. Just on the street, as many have said I allways thought 36f 44r cold, as recommended. K

spirited drives... go with 36/44... in town 4 lbs less for a more comfortable ride. I dont think that it is a big deal on the street. On the track its all trial and error and how fast you are...

Porsche revised this for the 997, which I think is perfectly fine on the 996. I used these presure when I had my 996 and it felt better. Fully loaded, 1 driver, 3 passengers plus luggage front 36psi rear 44psi Just driver (or with 1 passenger) front 33psi rear 39psi

According to this ( http://www.pneus-online.co.uk/porsche-tyres-advice.html ), this discrimination is for 19" wheels only. Thanks for the answers guys!

What discrimination are you referring to? 36/44 is recommended for both 18" and 19" tires. Also let's keep in mind flat spotting when under inflating, specially after a hot run, and then parking it in your cold garage floor (ask me how I know) If the ride is harsh, adjustable shocks and springs should be considered.

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OK, it's hard to argue against the factory recommendations. I'm going back to 36/44. Maybe my ride is not that harsh. I haven't driven any other 996s except mine. Maybe they're all like that. ...Rickker

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Sounds like a Cayenne to me.

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Not. Carrera 911. They were being on the safe side when they first came up with the 44/36. Just too hard for unloaded cars. Specially on the track.. slides a lot.

This is the most interesting tire pressure thread, because it mentions that 997 tire pressure recommendation is LOWER! I feel like stock 36/44, or even lower 34/42 pressure is rattling my car to death on the junky NJ roads. I've also read that stock 44 for the rear causes uneven premature wear. Other threads suggest lower pressures cause tires to flex more and wear out or even blow faster than the stock high pressures. I'm gonna try 33/39 for the street and highway. Any objections?

Are you on 18"s? My 17" call for 36 psi all around, but I dropped the front to 35psi. Try 33/39 and adust up or down based on ride and/or tire wear.

I should have mentioned I'm on 18's for the summer/fall, but switch to 17's for winter. Why the big difference in factory pressure recommendations from 18" to 17"?

More sidewall on the 17"s

I never checked the pressures when I bought the car, but quickly took to an indy shop for alignment and he bumped the pressures up to 36/44. I don't know what they were before, but she told me that if it felt too hard I could lower to 40-42 in the rears, but honestly I can't even tell the difference. I just want the best pressure for longest tread life - what do you guys suggest? (just reg street/highway driving)

Reccomended PSIs in OM.

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That's what I maintain on my PZeros for over 1.5 years of regular solo driving.

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Looks like the consensus is the factory settings are safest, but cause the rear tires to wear prematurely. 33/39 seems to allow more even wear.

In the wet more pressure reduces hydroplaning. The front would be my main concern in the rain ie Oregon or rainy run times.

This tread is pretty funny so far!!! Tire pressures are such an imprortant component of the cars handling ability with the enginneers at porsche investing countless hours getting this right. Not only for handling but for safety as well... Anyone running r-compound tires on the track will agree getting the right tire preassure is much more challenging, even from right to left as well as front to rear.The impact the tire pressure has on the handling is crazy. Good luck, and be safe...

As per 997 TSB (DEC 2009) 997's are Heavier than 996's. For 18" and 19" Wheels w/ Summer or Winter Tires Half Load 33f and 36r PSI Full Load 36f and 43r PSI This is what i Run

I run the recommended pressures. To me, lowering pressures to solve a ride problem is a pretty heavily compromised bandaid. That rear pressure is meant to carry the weight of the engine, and it's a significant component of Porsche's solution to trailing throttle oversteer. I want that. Some may recall that I replaced my shocks awhile back after I found one of the OE shocks leaking. I didn't want to lower the car (Toronto peeps will understand why), so I ended up going with Bilstein HDs and the OE springs. The Billies were far better damped than the OE shocks, both over high frequency bumps and when rebounding from sharp impacts. The crashy ride was solved, without anything being softer. I mention this only because I think it's possible that what people are experiencing as a "harsh ride" might actually be lousy rebound damping from worn OE shocks.

If it is Harsh Ride you are trying to solve - Please take a close look at tire Age. I assume most know this - but I will share my story. Purchased a 2000 C4 a few months back. Picked up the car in LA & drove home to Seattle. It has a TechArt Coil-over suspension so I assumed the Harshness of the ride home (so much it blurs my vision) was all related to this. At home, took a closer look at tires and see they are Conti 2's and 9 years old. Still had 70% tread. I suspect the prior, prior owner of 7 years used 18 inch wheels and had these tires & 17 inch-ers in the garage for all those years & put back on for sale. Bottom line - purchased the new Conti Extreme DW tires in OEM sizes - and the C4 is transformed! Yes the ride is Firm over dips - but the Harshness is gone. Even the shocks of hitting road paving cracks & Rail lines is absorbed. Those road edge warming strips - are just noise now - not a massage. Check the tire age - as Many low mileage Porsche have old rubber. And as far as I can tell the DW tires have the same or better grip as the former Conti 2's, should be way better in the rain, and compared to the 4 year old Potenza's on my 968 ride better & quieter.

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

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.

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.

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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.

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.

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.

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

This is the TPMS system the TPMS system 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).

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

+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.

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

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.

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.

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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)

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:

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Wow. What pressure are you running on those? Do you track this car? Have you seen this before on your tires? Sorry for all the questions, it's just that this is nasty looking for such low miles.

Yeah, I tracked 'em. Two track events only, though. The first time, in October (right after I bought the tires), I didn't notice any of this type of wear. Then tracked 'em again a couple weeks ago, and this happened. I watched my pressures carefully, but my understanding is that this damage is caused by them getting too hot. So, I guess I can't necessarily fault Pirelli, but still..... one would think that their "Ultra High Performance" tire should hold up better than that. I'm replacing them with a set of Bridgestone Potenza S-02's. Let's see how that works out.

[QUOTE=Cuda911;11088836] So, I guess I can't necessarily fault Pirelli, but still..... /QUOTE] Given my experience of P Zeros, I'd say it was about par for the course!

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[QUOTE=mcbit;11089016] Exactly my experience with the P Zeros too. I will never go back to them. I think Pirelli had the edge in the 80s and early 90s then I don't know what happened to them. As for the SO2's, I think you're a few generations behind. I will say the SO2's though were my favorite tire when it came out and the best tire I've driven at that time. This was one of those tires that made you a better driver not due to your skill but rather the sheer grip and forgiving nature it had. It was a tire that could make a fair driver look good.

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[QUOTE=alpine003;11089126] Hmmm... I chose those after talking to the tire shop guy. Of course, there are a million tire opinions, and I've read about 900,000 of them here. I was originally going to get Bridgestone Potenza S-04's, based on a recommendation by my mechanic. The tire shop guys says those don't have N rating, and he wasn't too keen on them. I suggested Pilot PS2's, as that seems to be a very popular tire recommendation by RLers. The tire shop guy said I would have similar track issues with PS2's. He recommended the S02's, and they were slightly cheaper than the PS2's. Here's the quoted prices for all four (including tax, mounting, etc.) F = 225 30 18 R = 285 30 18 Bridgestone Potenza S-04 Pole Position: $985 Bridgestone Potenza S02: $1,385 Pilot PS2: $1,535 The tires are due in Friday. Should I change my order?

I didn't realize they were still making SO2's. I've never driven on the S04's so can't comment or compare but the fact that the price is higher on the S02's, makes me wonder if they are indeed still better in some way than the newer models. Hmmm.... FWIW, even now I have yet to come across a lot of tires that had the same performance as the SO2's. My current Evo V12's feel inferior to the SO2's but apples to oranges as I had a different car back then so take it with a grain of salt.

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My Corvette has similar instructions about increasing pressure slightly when driving above 130mph. Seems counter-intuitive, since the tire's going to get HOT at those speeds, but I'm all for following directions and not shredding a tire at speed...

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You are running too high a pressure at the track and as a result the contact patch has been made smaller with emphasis at centre hence the wear S02-A were awesome ! Good to the last drop. PS2 were also great tires for track. I think the edge goes to the so2-a for stickiness. I ran them both at 38 psi hot at the track and that was the sweet spot.

I ran 'em at 34 psi (cold). Seemed to be a good pressure when I tracked them in October, and the air and track surface were much hotter then. But, the wear pattern doesn't lie, so it was obviously too high, and too hot. Here's the wear ratings of the various tires: Pirelli P-Zero: 220 Bridgestone Potenza S-04 Pole Position: 260 Bridgestone Potenza S02: 140 Pilot PS2: 220 So, the S-02's are much stickier than the rest. And, S-02 has N rating, S-04 does not.

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To me, that looks like blistering. Yes, caused by heat, but as I understand it, caused by excess heat from caused by at least partially by overinflation. The rubber reverts to an un-vulcanized state from extreme heat. From www.InsideRacingTechnology.com Another form of reversion is blistering. The photo shows a right-rear tire with a line of blisters around its circumference. Too high cold inflation pressure or too much pressure build-up during use caused the tread to overheat. The heat is generated at the interface between the belt plies and the tread and the rubber melts, causing a local blister.

Sooooo, 4 pages of discussion over a 5psi difference in tire pressure? Only on Rennlist... LOL

I know most that heat cycle do it on competition dot rated tires but I can't help wonder if it would've made any difference in this case considering the P Zeros use a fairly soft rubber compound compared to others. http://www.tirerack.com/tires/tirete....jsp?techid=66

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Yeah, might seem excessively obsessive but tire pressures seem to make a pretty big difference in ride and handling. I think it's something to take seriously and get correct for your car.

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The general rule is - that when you need grip you " add" air, not take it away! There are limits though and it is dependent on a lot or circumstances.

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Major factor is tire deformation. Look at a tire mounted on a car, it is flat on the bottom. Take the wheel/tire off the car, tire is round again. At high speeds that flat spot doesn't have time to regain the round shape before slamming the flat spot into the road. Higher air pressure helps the tire stay rounder, & therefore run cooler. When the C5 ZO6 debuted I was preping it to send to magazines for testing for handling spec's. GM engineers said to stay with stock psi for slalom, skidpad, & 0-60 tests.

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I find more myths about tires than any other part of a vehicle. Most of them are detrimental to safety.

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Solid center tread block retains more heat than blocks with cuts & sipes. Pirelli introduced the 1st true high-performance, radial low profile tire around 1975. They rode that reputation way to long & I have always considerd them way to finicky & expensive for what you get.

I think that will be the last set of Pirelli's I ever buy. $$ down the tubes. Flush!!! .

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Just ask Pirelli and Lewis Hamilton!

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I was going to post a delamination pic before but decided not to but I see you were thinking the same thing.