Celica Forums General Discussion General question on tire pressure? better preformance?

hey guys...i have a GT with the stock 15s and it says in the manual to have it at 29 PSI. however after talking to a co-worker who has an integra with 15s he says he has his at 35 for better feel,acceleration, and grip. well i'm not about to go up to 35 but i did notice that one of my tires was waay under 29 (it read at 20)...so i decided to have it at 30-31 to try it out. surprisingly i felt a diference in acceleration and grip...anyone experience this or is there some validity in this? thanks.

he probably have aftermarket wheels and tires.

29 psi is pretty low dude. What is the max pressure printed on the sidewall of the tire prolly 35 or 44 psi? Use that in the front and drop 3 to 5 psi in the rear that's what i do when I auto-x.

i thnk the max is 35 on mine...so drop 5 on the rear? so around 30? thanks man...and i do feel imporvemnt at 31...it's just that the ride is a bit stiff with my springs and shocks

just do it around the recommended...otherwise you're going to have bad tire wear.

yeah 29 is what it says in the manual ... I usually run 28 in the front and 32 in the rear.

Yeah, I hate when my rear tires feel sloshy during turns

i thought that you have more grip when you lower the tire pressure? well al i know is that with a higher psi you will get better mpg.

yes, less pressure = more grip

ok,ok,ok...i'm getting conflicting info here...people like CID498 is telling me to raise the pressure and ricepowered is telling me to lower it...i'm so confused..

Most street cars are not set up for neutral handling. A front drive car will typically have significant understeer. While this is not conducive to fast cornering, if someone is driving too fast around a corner, the front wheels will slide and not turn the car as much as expected. The natural reaction of the driver to this is to lift off the gas which is the right thing to do to regain some traction.

Back to the theory that all four tires should contribute equally to the cornering grip. There are also two other dynamics that work the tires and generate heat: accelerating and braking.In a front drive car, the front tires have the workload of doing both braking and accelerating. Furthermore, a factory stock front drive car probably has a tendency towards understeering in the corners, and that adds even more heat to the front tires from the excessive cornering friction. This combination conspires to heat up the front tires a great deal more than the rear tires.


During a driving session on the track, the front tires may increase as much as 9 to 10 psig from the cold setting. The rear tires on that same car may only come up 4 to 5 psig. This clearly points out that the car is far from having the front and rear tires contribute equally to handling grip. This is not optimum at all, and requires cold pressure settings at a seemingly odd starting point.

If we look at the example situation above, we may find from testing that when the tires are hot, a reasonably neutral handling balance occurs when the front tires are at 34 psig and the rear tires are at 35 psig. If we know that the front tires are going to increase in pressure by 9 psig from a cold setting, then the appropriate cold setting is 34 minus 9, or 25 psig. The rear tire cold setting would be 35 minus 4, or 31 psig. This may sound completely counter intuitive considering that on the street, and when you first go out on the track for the first few laps, these settings will feel absolutely horrible (this setting will likely result in a lot of oversteer and will feel very loose). However, on the track, on about the third lap, the handling will settle down and should reach a neutral balance.

Remember that what matters is how the car handles in long runs, and it is the hot pressures that are to be focused on. If this means starting out with some seemingly strange cold settings, so be it.

As an aside, the best thing to cure significant understeer, and the first money that should be spent on any factory car with excessive understeer is a rear anti-roll bar. As a first modification, this will probably result in more lap time improvement per dollar spent than anything you can have done to the car.

Low Tire Pressure (Under Inflated)

A tire that is under-inflated will have a tire profile that will sag in the middle. This sagging profile results in increased rolling friction and causes the tires to run hotter. This will reduce tire life but it will also increase tire traction or grip. Depending upon racing conditions and the overall setup of the car the increased grip may be necessary to be competitive even at the cost of tire life.

High Tire Pressure (Over Inflated)

A tire that is over-inflated will have a stiffer, more upright tire profile. The contact surface of the tire will have a crown to it, bowing out slightly in the middle. This tire profile results in decreased rolling friction and the tire will run cooler. The tires will run faster but with less tire traction or grip.

the reason that your tires felt better when increasing the cold tire pressure, is because you didn't allow enough time for your tires to come up to operating temperature. why do you think they have a warm up lap in racing or the burnout pit in drag. if you keep your pressure up and then go and bring you tires up to temp I bet they will start feeling sloppy.

thats my 2 cents

hmmmmm...interesting...time for me to experiment this weekend..

that's why i do this

Ok check it out F*ck what the manual say's, The psi rating that's on the side wall of the tire is the cold rating and that is what matter's you will not get funky tire wear by using the pressure specified on the tire. The reasoning for a lower pressure in the rear tire's is to allow more sidewall flex in aggresive driving and it allow's the rear to maintain more bite. ct run the max pressure that is marked on your tire's (all four of them) and if you wanna go out and drive it like you stole it decrease the rear pressure a couple pound's.

will do CID498

hmmmmmmmmmmm ... ...

makes sense. the celicas weight distribution is somewhere around 60/40 (front-to-rear). obviously this means more pressure is pushing down on the front wheels than the rear wheels (more traction for the front). also, like street prototype had said..the psi will almost definatley be higher on the front wheels.

lowering the pressure in your rear wheels will help your rear wheels gain traction, which will help even out traction with the front wheels (since most of the weight in the celica is centered towards the front, it already has 'improved' traction).

OK let's clear up some confusion, in daily point a to point b driving run the tire manufactuter's psi rating's that is where the tire's optimum performance is (this is why I stated f*ck the manual because it don't know what tire's the car has on it), My suggestion of lower tire pressure in the rear is for extreme handling agility and ability as in auto-X and the like. It work's for me and everybody else at the track.

ditto. but tire makers' defination of 'optimum performance' also means the least amount of tire wear. the more you are to the suggested psi rating of the tire, the longer your tire will run.

if you're running on the stock wheel + tire size follow what the manual says. just keep in mind that the manual gives the optimum cold tire pressure and that you need to check the tire pressure before you drive it over a mile otherwise the tires will heat up and give you a false pressure value.

put the pressure that feels right to you. the one way all of us can tell if our car is not handling right is with the way our ass feels in the drivers seat. change the pressure until you feel right.

personally i have 32psi in all four.

i tested it out and put 32-33 on the fronts and 29 on the rear..handles a little better ...thanks CID

this is old thread...but i dont want to open another thread.

does the psi marked on the tire = lb?

cos my meter is in lb...so im not sure
the tire i have is Falken ZE512 the max psi is 50 (cold)
http://www.falkentire.com/tires/512_sizes.htm
(the 205/50R16 one)

so does it mean that i can put the air until my meter shows 50lb??

it should be in lbs, this is the US, we don't use the Metric system

so, psi = lb eh?

yeah

oh alright~ thx

hmm..just want to make sure b4 i go and add the air into my tire.

if my tire marks 50psi, i should add the air till the meter says 50lb rite?

that's where im confused, 1psi = 1lb/in^2
they are not even in the same metric system...

the question is, are the numbers marked on the tire pressure meter in lb/in^2?

PSI= lbs per square inch. so yeah, just fill it up to 50 lbs.

My Yoko's say that the max psi is 50, but that if i'm gonna have a heavy load, like 1100+ lbs, which will never happen. So I just inflate mine at 35psi 'cuz that's what the local tire place, where I ordered them from, recommends.