ericem Posted May 18, 2007 Share Posted May 18, 2007 Hey, just wondering, on the side of my door is says the front tires need 30 and the rear needs 29 on light load? and 35 front and 32 rear on heavy load, i think, do i put the pressures off like that? or do i make them even im confused Link to comment Share on other sites More sharing options...
mtsmiths Posted May 18, 2007 Share Posted May 18, 2007 Hey, just wondering, on the side of my door is says the front tires need 30 and the rear needs 29 on light load? and 35 front and 32 rear on heavy load, i think, do i put the pressures off like that? or do i make them even im confused We just run 36 all around, always have. Link to comment Share on other sites More sharing options...
ericem Posted May 18, 2007 Author Share Posted May 18, 2007 We just run 36 all around, always have. ok car seems bouncy so(maybe its my rear struts that are awaiting replacement:rolleyes:) guess that will help a bit, also seemed like AWD was kicking in randomly on take off lol. Link to comment Share on other sites More sharing options...
jamal Posted May 18, 2007 Share Posted May 18, 2007 There is more weight on the front so you need a bit more pressure. It evens out the contact patches and rolling circumference and stuff. Adding a few psi stiffens up the tire a bit and I run 37/35ish on 205/55-16s. bounciness = blown struts / underdamped suspension Link to comment Share on other sites More sharing options...
Manarius Posted May 18, 2007 Share Posted May 18, 2007 I always run whatever the max is on the sidewall of the tire. From what I've read, what's in the door sill is for a comfy ride - not one best for your tires. Link to comment Share on other sites More sharing options...
jamal Posted May 18, 2007 Share Posted May 18, 2007 running the max listed on the sidewall might get you an extra 0.5mpg, but grip will suffer because your contact patch is shrunken and the center of the tread bulges out a bit. It could result in uneven tire wear, and braking distance and cornering ability will definitely suffer. Link to comment Share on other sites More sharing options...
ericem Posted May 18, 2007 Author Share Posted May 18, 2007 On top of that the air expands when the wheel is hot, any risk to blowing a tire? Link to comment Share on other sites More sharing options...
jamal Posted May 18, 2007 Share Posted May 18, 2007 no, that is the max for a cold tire and should be fine. The ratings on the door are also for cold tires. Link to comment Share on other sites More sharing options...
ericem Posted May 18, 2007 Author Share Posted May 18, 2007 no, that is the max for a cold tire and should be fine. The ratings on the door are also for cold tires. ok, well i set the front tires to 37 exact, and 36 exact in the rear sound fine? see i thought with the AWD system the tires needed to be exactly the same pressure. Link to comment Share on other sites More sharing options...
srs_49 Posted May 19, 2007 Share Posted May 19, 2007 In general, I always thought you wanted a little more air in the tires that are carrying the greater proportion of the car's weight. Something about trying to get front and rear tires to run at the same slip angle when cornering. Most front engine cars, especially those that are FWD exclusively, may have over 60% of their weight on the front tires. Subarus, with their AWD system , may not be quite that bad. But still, the recommendation to put a couple of more psi in the front jives with my experience. Link to comment Share on other sites More sharing options...
jamal Posted May 19, 2007 Share Posted May 19, 2007 ok, well i set the front tires to 37 exact, and 36 exact in the rear sound fine? see i thought with the AWD system the tires needed to be exactly the same pressure. Yeah that sounds fine. But like I said, having more pressure in the front with a front heavy car means the front and rear tires have closer to the same rolling circumference. I run 0-3 less psi in the rear depending on load. If I've got all my crap in the car for a trip home to Montana I'll have even pressure all around. It's not really that big of a deal I'm just kind of anal about things sometimes. So it goes with my profession I guess. Link to comment Share on other sites More sharing options...
mtsmiths Posted May 19, 2007 Share Posted May 19, 2007 running the max listed on the sidewall might get you an extra 0.5mpg, but grip will suffer because your contact patch is shrunken and the center of the tread bulges out a bit. It could result in uneven tire wear, and braking distance and cornering ability will definitely suffer. AHA! This is EXACTLY why I do run my tires a little high. How many tires have you ever seen (especially on front-wheel drive cars ... and face it, in normal dry weather driving a Subaru AWD is esentially a FWD car) a tire wear out in the middle? Not many hmmm, maybe none? They wear out on the shoulders, even when perfectly aligned. So a couple/few psi helps even up the tire wear. Yes, your are absolutely correct that cornering and braking limits are marginally comprimised by high tire pressure, but only noticable at driving extremes ... I don't drive like that (any more) so it is a reasonable trade-off ... a slight performance degradation, that is of no consequence with my driving style, vs a noticable improvement in tire mileage. Link to comment Share on other sites More sharing options...
OB99W Posted May 19, 2007 Share Posted May 19, 2007 ok, well i set the front tires to 37 exact, and 36 exact in the rear sound fine? [...] Have you verified that the maximum inflation pressure rating (on the sidewall) for the tires you have is over 37 psi? The "standard load" max spec is only 35 psi (cold), although many tires do have a higher rating. Link to comment Share on other sites More sharing options...
subaruplatt Posted May 19, 2007 Share Posted May 19, 2007 Hey, just wondering, on the side of my door is says the front tires need 30 and the rear needs 29 on light load? and 35 front and 32 rear on heavy load, i think, do i put the pressures off like that? or do i make them even im confused On My 06 impreza wagon the factory tire pressure is indicated at 33 front 30 back. Thats 11/10 ratio. Tires can expand from a normal cold state as much as 4 pounds. On the side wall it says that the maximum tire pressure is 40 pounds. So In the front I put in 36 cold and in the back 32, could go 33 according to 11/10 ratio but there is hardly any compression on the back tires even at 32 and we all know that radial tires actually are properly inflated when they look just a bit soft. Anyhow 36 front vrs 33 flattens out the roll and wander nicely. Link to comment Share on other sites More sharing options...
ericem Posted May 19, 2007 Author Share Posted May 19, 2007 hmm, ok the side wall says 40PSI max. So i did 37 front 35 rear although i didn't follow the ratio of the manufactures pressure, i prefer it like this. Still i don't understand, wouldn't this damage the AWD unit faster? Link to comment Share on other sites More sharing options...
Manarius Posted May 19, 2007 Share Posted May 19, 2007 hmm, ok the side wall says 40PSI max. So i did 37 front 35 rear although i didn't follow the ratio of the manufactures pressure, i prefer it like this. Still i don't understand, wouldn't this damage the AWD unit faster?No. The AWD unit gets injured when tires roll at different speed. Link to comment Share on other sites More sharing options...
subaruplatt Posted May 20, 2007 Share Posted May 20, 2007 No. The AWD unit gets injured when tires roll at different speed. Difference in tire pressure from front to back is calculated to compensate for the decreased diameter of the front wheels as they are more compressed due to greater load bearing. I noticed that the front dampers are tuned for moderate tire pressures after that you get bounce back. With new struts and better tires who knows? On the auto the torque is regulated so that the normal slip front to back is 60/40. That is because normally 60 % of the traction will be available from the front wheels. This is once again a weight thing. I have read that You get 58/42 on the wagon and 60/40 on the sedan http://www.ultimatesubaru.org/forum/showthread.php?t=72585 Link to comment Share on other sites More sharing options...
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