I am curious what kind of air pressure has been tried in our cars.I have an 06 wrx and usually run 40 psi front and rear .mostly around town driving (commute) but like to go up to the mountains on weekends.Any input would be appreciated.
40 is pretty high for daily driving. You could easily bump it down to 35psi. I normally run 45psi autox'ing on street tires and 42-45psi autox'ing on R compounds. 40 will definitely give you faster tire wear.
hmm did not know this Im running 50 all around the max is 51 on the coopers the fuzions I kept them maxed out at 52. so these are too high to run street?
It also depends on your tires. You should definitely run at least 10psi less than the max pressure. Of course, psi can be increased for hauling or racing.
My friend let me drive her car the other day, and after driving 2 blocks, I had to pull into a gas station, as the car felt really strange, and was pulling to the left pretty bad... it turned out her tires were in the 12-16psi range.... she didn't even consider that tires need air once and a while. After putting them in the 35psi range, it ran fine, but she corded one of them later in the day, due to one of the rears running at 14psi for a long time. The center of the tire still looked good though, while the edges were bald on both of her rears. I would definately recommend not running 12-16psi... -- Brian
I would always recommend running at least the stock p.s.i. Usually 5-10 psi more is ok.the manufacturers are very concerned about ride quality.not as worried about handling or mileage.I would say to never exceed max. sidewall pressure.can vary by tire brand.usu. more psi helps your gas m.p.g.. I should have also asked if varying pressure front to rear helps our cars handling chacteristics..
The RE92's on the 06 get squirmy sidewalls at around 35psi. When I had mine in the mid 40's they felt pretty good. I droped them down to mod 30's for ride comfort but I am going back up to about 42 front and 40 rear. Also remember to check and adjust air pressure when the tires are cold.
Back when I had the stockers on I kept them around 35 psi. Except when I autocrossed I'd take it to 45+ psi. One time I forgot to let the air out afterwards and ended up driving on the interstate in the rain. I definitely noticed it was a little squirmy feeling. Kind of scary at 80 mph.
Thats not a bad setup, but I would suggest switching the numbers. Having a higher psi in the rear can often allow a break in traction, i.e. oversteer. It won't be drastic, but it would definitely help. I always carry a 12V air pressure pump and a pressure gauge in my glove box. Never know when you will need it.
I bought my STi a little over a month ago and already managed to cord one of my tires. The house we just moved into is in a new subdivision and I drive through a fuc$#ng consruction site every day long story short I just replaced all of my tires with new re070's and now my butt hurts....
If you want oversteer you want less pressure in the rear than the front ie. more slip angle on the rear tires. On the street I have been running 36-38 front and 34-36 rear for 3 years. I have noticed very even tire wear from this and haven't had any issues with traction wet or dry. Also for daily driving you want a few psi less in the rear so the tire height (from ground to center of the wheel) front and rear will be close to the same. You need slightly more in the front due to the cars being nose heavy. This will help your center diff live a long and happy life.
^^^ Mr Cone Dodger has it. Those are good street pressures to run ( I run about the same, 36 front 34 rear street cold pressure ). I've played with tire pressures some @ Little Talladega & RA, plus input from SS. As the tires get hot early in the day I keep letting pressure out to maintain 44 front 42 rear hot. FYI, those cold street pressures will exceed the hot pressures I shoot for on the track.
Will give this a try cause mine had 36f/39r before I put air in and felt squishy around corners. so 10 less than max with a variance of 2-3 psi from front to back.
The comment about running higher in the rear is debateable. I run lower in the front for soloII because it helps to use the entire tire. Meaning that hard cornering you can use more of the tire. This isn't completely true within a limit of the sidewall being able to hold the cornering load. So you can't just keep going lower expecting more grip. If your tire is higher in the rear, the rears will be less likely to roll over, or use more tire area and will give you less grip. I normally run 35 all the way around, because the heavier front compensates for the same tire pressure up front. You can get a tire pressure pump at your local autoparts store. I think I paid less than $20 for mine at Advance. I know Walmart has it also.
Its really up to you. I am sure you will hear some differing opinions here. Play with the settings and if you can notice a difference and like it, then keep it. Otherwise, 1-4 psi, you won't really notice the difference unless your racing.
I also autocross. The proper thing to do to set up the tires (without adjustable suspension and if you don't have a tire pyrometer) is to mark the front tires and find the optimum pressure watching the marks for the amount of roll. Then you can do the same for the rear but that would give you a car that understeers badly (with a WRX at least). Raising the rear pressure the rear of the car will come around but the only thing you are doing is sliding. You aren't allowing the tire to do the work. By lowering the rear pressure you are increasing the slip angle and this will make the rear a bit more loose. I used to think on the same line you do until I read "How to Make Your Car Handle" by Fred Puhn, "Chassis Engineering" the author aludes me at this time, and "Tune to Win" by Carroll Smith. All very good reading by the way. There are some other drivers that were thinking along the same lines using higher rear pressures. When I suggested a switch they said their cars felt better and they were turning faster and faster times. I'm not trying to bust on you just trying to educate. Edit: On my Azenis in STX I run 42 frt and 33-37 rear depending on the course and how loose I want the rear.
On the subject of autocrossing on the STi and tire pressures, we found that 42F/55R works best when using 245/40-17 v710s on stock shocks and springs. When we switched to aftermarket shocks, we lowered the rear down to 50psi, which worked better with the stiffer rear shocks. The higher rear pressures really help with rotation, and are perfectly reasonable in an autoX environment. I wouldn't recommend running them on the street though. As for the shocks, we are running the Ohlins, which are really kickass for the car. They have 32 settings, and we found that 5/32 front, and 22/32 in the rear works good (32 = stiffest). For course dependent setup, if it is a faster course with no slow speed 180 turns or such, stiffening up the front a bit helps in the slalom. But when you have a pivot, we found that you need a softer front, as to assist rotation. For the rear, any stiffer, and the car would tend to bounce too much, instead of sliding during rotation. I would highly recommend a set of adjustable shocks if you get serious with AutoX. We had a nationally competitive driver help us setup the car with the help of a tire pyrometer. We are moving to 275/40-17 v710s next, and I suspect that we will be able to run lower tire pressures on the car. -- Brian
I ran 40 psi all around on the re92s but on my s03 pole positions I ran about 38f 36r. I have pilot sports on for the time being and I keep about 36 all around in them. The side walls on the pilot sports feel pretty stiff and so is the rubber so to get the best grip I had to back down from 40 and 36 is where they felt best.
Matt, what are you running on the street? Are you on RE070's? I'm playing around with pressures now and, after a month, still running the "recommended" stock pressures of 36-30.