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Discussion Starter #1
Right now I currently have Michelin Energy MXV4 tires (10K old) on my car. It says that the tires can be inflated to 44psi max, so I have the back tires at 38psi (hot) back, and 36psi (hot) on the front tires. Any suggestions on changing?

Kevin V.
Gainesville, FL
'90 Talon TSi FWD
 

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vlaar said:
Right now I currently have Michelin Energy MXV4 tires (10K old) on my car. It says that the tires can be inflated to 44psi max, so I have the back tires at 38psi (hot) back, and 36psi (hot) on the front tires. Any suggestions on changing?

Kevin V.
Gainesville, FL
'90 Talon TSi FWD


First off, I have been in the tire business for 14 years. What size are the tires? Regardless, the 44psi on the tires is the MAXIMUM pressure for the tire. In most situations, you do not need... or want... that much air pressure. The car WILL be more steering responsive and corner better at a higher air pressure but you will sacrifice traction. The rule of thunb that I use is this. Look at the maximum weight capacity of the tire at the max psi. If you are using the stock 205/55R16 tire size, the max weight capacity per tire at 44psi is 1279lbs. Multiply that times 4 to get the overall weight capacity. That would equal 5116lbs. Now, obviously, your car does not weigh that much. It probably weighs about 3200lbs or so. I am not sure what the normal front to back weight ratio is on our cars but we will use 60/40 for an example. So take 3200lbs x 0.6 (60%) to get the weight on the pair of front tires. In this example that would be 1920lbs which is 960lbs per tire. Now take the 960 divided by the 1279 max capacity of the tire... you get 0.75 or 75%. Take that 0.75 x 44psi max pressure and you get 33psi. This is the minimum pressure you want to run at highway speeds (other than the drag strip). If you use the same formula for the rear with the remaining 40% you will get a pressure of 22psi to carry the weight. Now you don't really want to go that low on the rear of the car because it is a front wheel drive. You will get more rear end squat. I would match the rear air pressure to the front unless you have adjustable struts. Then I would run a minimum of 28psi in the rear (for street use) because the struts will help a lot and the tires will wear better on the rear without as much pressure in them. Too much pressure causes the tires to wear in the center... too little causes them to wear on the edges (assuming there is no other suspension related problems.

Hope this is helpful.
 

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One more thing. I noticed that you were referring to "HOT" air pressure. All tires (and the air pressures I was referring to) are a "cold" air pressure meaning not to set them right after driving. Do it after the car has been sitting a few hours.
 

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Just wanted to add a couple thoughts here....

I always put a lot of air in my tires, even though it means sacrificing some ride, it helps out gas mileage, and makes it handle better. In my experience a pressure over 38psi cold will cause the tire to wear unevenly as if it were overinflated. ;)

Another thing being you have a FWD, on a minute level by putting more air in the front than in the rear you help your car understeer less. However as for ride quality it's very common that people do the opposite.

~jm
 

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Sorry to bring up an old post, but:

If I do 35 psi front and 30 back, is that ok? I'm all confused now. They're 16 inch tires.
 

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Discussion Starter #6
Right now, I am running 33psi cold in the front and 34psi cold in the back on my car. I have to warm up my Michelin's before I can boost in 1st or 2nd gear. Otherwise, I get tire spin. I don't feel like lowering the tire pressure to say around 30psi cold (32/33hot) unless I know I'm going to be racing:) Oh, I have 16inch wheels also! Later.

Mods: small 16G, MAS mods with K&N
2.5inch testpipe, Arospeed dual tip muffler
 

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if you have a fwd you should go 35 psi in the back and 25-30 psi in the front (traction). i go 20 psi in the front, but i have major traction problems. i also am obviously sacrificing handling and high speed stability/saftey, but you be the judge. i also have stock rims and don't give a damn if they bend....
 

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Hm, okay, well I'll chime in. I've always used the measurements Mitsubishi gave us on the door jam.

Now I have 18's with a 225/40 profile. I run about 35/30psi (front/rear). I never really thought about it a whole lot. Does that sound about right?

khendriksma1: Thanks for the math lesson on tires, that was interesting :)
 
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