Tire pressure

[Uncle Vinnie]

I just got new rubber on my car, got the badboys installed today:
Falken ZE-512 255-45-17
What psi do you guys think I should run on these tires.

thanks

 

[beaups]

whatevers on the label inside your door jamb. 30 or 32 IIRC

 

[JES_LS]

what ever the manufacturer of the tire recommends.

 

[DLS8K]

what ever the manufacturer of the tire recommends.

Hmmmmm........haven't heard that one yet. Each car has a label that states the PSI the tire should have. Tire makers do not..........merely, they offer a max PSI number which shouldn't be used. I am hoping you made a typo.

 

[beaups]

right you need to just go by what the label says on the car. mfr won't make recommendation because it has a lot to do with the weight of the car.

 

[Smokey]

But you also have to realize the manufacturer's recommendations are based on the tires that were on the car when it left the factory. This does not always apply if you change tire sizes or speed ratings. Your installer should also provide you some insight on this. To say that a 235/50-17 tire requires the same tire pressure as a 255-45-17 does not always hold true. Each tire has it's own characteristics. The manufacturer's recommendation is a good place start if you are NOT using the same size or speed rating. But you may have to adjust this to obtain proper results for your particular application.

 

[macboy]

a 255/45R17 will have a slightly larger contact patch than a 235/50R17 (change wheels size though, and you can't so easily make that assumption). For that reason, you can get away with slightly less pressure than recommended for the stock tires, since less pressure over more area balances out to the same force. That force is the portion of weight of the car being carried by the tire.

Despite that though, you should experiment a little. I am running 33 psi in my tires (Michelin Pilot Sport AS) which are stock size. The increased pressure substantially improved handling and cornering. I'd recomment starting at 30 PSI and experimenting. Test the handling at highway speed, cornering, acceleration, braking. Get a feel for the tires. Then adjust the pressure up or down and do it all again. keep in mind that running a too-high or too-low pressure can be dangerous and/or result in uneven tire wear (high: wears in center, low: wears on edges). You may have to trade off comfort/noise for performance (Lincoln's 30 PSI recommendation leans toward comfort IMO).

 

[Uncle Vinnie]

Thanks for all the info.
Right now I have it set for 32psi, so far feels good, the car feels much smother than the stock tires, and is absorving more the bumps vs the stock.
I'm very pleased with the tires so far.

 

[00ls-sport]

when i used that size...bfg sent me an email to run at 28psi to be pretty much the same rate as the stock 235/50/17. i personally thought was too low, and generally ran between 30-35 psi.

 

[2001LS8Sport]

right you need to just go by what the label says on the car. mfr won't make recommendation because it has a lot to do with the weight of the car.

You need to be careful...that is not always true. I have a set of tires on my Cobra that require an entirely different air pressure than the factory tires...and their recommended air pressures.

 

[pbslmo]

It all ties in together, the weight of the car, the suspension, shocks, tires size and air pressure.

If you have a sport suspension, shocks and tires, go with the manufacturer of the tire. If you have stock shock spuspension go with the car 30 psi listed in the door jam. It gives a smoother ride.

 

[pbslmo]

um, NO!
The manufacturer of the tire knows nothing about the car, all they know is the characteristics of the tire, like the maximum safe inflation pressure and the maximum load. The maximum inflation pressure listed on the sidewall is absolutely not in any way a recommended inflation pressure.

In addition, the inflation recommended in the door jam is not universal, that is, if you change tire size (and the OP has done that), then you cannot blindly apply that tire pressure as being correct. You will note if you take a look at the label, that it lists not only a pressure, but a specific tire size as well. The listed pressure is for that size tire.

I stand corrected! Thanks!

 

[macboy]

If you have a sport suspension, shocks and tires, go with the manufacturer of the tire

um, NO!
The manufacturer of the tire knows nothing about the car, all they know is the characteristics of the tire, like the maximum safe inflation pressure and the maximum load. The maximum inflation pressure listed on the sidewall is absolutely not in any way a recommended inflation pressure.

In addition, the inflation recommended in the door jam is not universal, that is, if you change tire size (and the OP has done that), then you cannot blindly apply that tire pressure as being correct. You will note if you take a look at the label, that it lists not only a pressure, but a specific tire size as well. The listed pressure is for that size tire.