Quick question for the tire guru's

[95TransAm]

I've wondered this for a while now and figured I'd ask.

Let's take for example the tires I am currently using.

Bridgestone Potenza RE950's (245/50-16's). The supposed recomended tire pressure is 40 psi. Due to the knowledge I've gained here, I've learned that a good pressure would be 32 front, 30 rear.

My question simply is why is it better to be running 8-10 pounds lower than what they suggest? Why would they even state 40 psi in the first place? So the tire lasts longer

Thanks guys

[wolfdogs]

actually, you are confused about the proper pressure...and it's not realy your fault, other than the fact the owners mannual for the car tells you what I am about to tell you.......

a given tire, whether it be a P metric (passenger car tire) or LT (light truck tire) or Truck bus tire.....had a maximum pressure.... this max pressure provides the max load the tire can handle and still perform without risking casing or construction damage and possible failure.

the pressure that is on the side of the tire is just that, the max. pressure for the max load. when a vehicle manuf. builds/designs/engineers a car/truck/tractor/bus..... they choose the tire size for that vehicle after careful engineering analyisis to provide the best foot print for traction, avoid understeer, oversteer, the right sidwall height for the proper flex to combine and be complatable with the suspension design.....the list is endless....

the vehicle manufacture determines the pressure the tire needs to run....not the tire manuf., who simply puts the "max. pressure for max load" on the side of the tire, which is no more than a DOT requirement.

if you look at at the placard/decal on the inside of your drivers door jam, you will see what the manuf. of the vehicle tells you to run for the O.E. tire size... the owners mannual has it too.

thats the biggest problem today with these folks upgradding tires on Pickups and suv's.....size wise... they dont take the time to consult the tire store, or the manuf. to find out what pressure they should be running.. the result is they put max. pressure in them..... so.....what happens? they went from a P metric OE tire that the vehicle manuf. said run 34psi in ...to an Light Truck tire (LT)..Load Range E....(the highest load range lt tire) that says max pressure 80 psi!!!!!! Now, they are ridding on "flintstone tires"......because the tire cant flex properly to provide the ride, the handling, the traction, you name it, that they are designed to do..... and the contact patch they have is the size of a golfball, instead of a softball...... ie: it rains....they hydroplane.... corner too fast, they flip or slide.......

did this help?

[95TransAm]

actually, you are confused about the proper pressure...and it's not realy your fault, other than the fact the owners mannual for the car tells you what I am about to tell you.......

a given tire, whether it be a P metric (passenger car tire) or LT (light truck tire) or Truck bus tire.....had a maximum pressure.... this max pressure provides the max load the tire can handle and still perform without risking casing or construction damage and possible failure.

the pressure that is on the side of the tire is just that, the max. pressure for the max load. when a vehicle manuf. builds/designs/engineers a car/truck/tractor/bus..... they choose the tire size for that vehicle after careful engineering analyisis to provide the best foot print for traction, avoid understeer, oversteer, the right sidwall height for the proper flex to combine and be complatable with the suspension design.....the list is endless....

the vehicle manufacture determines the pressure the tire needs to run....not the tire manuf., who simply puts the "max. pressure for max load" on the side of the tire, which is no more than a DOT requirement.

if you look at at the placard/decal on the inside of your drivers door jam, you will see what the manuf. of the vehicle tells you to run for the O.E. tire size... the owners mannual has it too.

thats the biggest problem today with these folks upgradding tires on Pickups and suv's.....size wise... they dont take the time to consult the tire store, or the manuf. to find out what pressure they should be running.. the result is they put max. pressure in them..... so.....what happens? they went from a P metric OE tire that the vehicle manuf. said run 34psi in ...to an Light Truck tire (LT)..Load Range E....(the highest load range lt tire) that says max pressure 80 psi!!!!!! Now, they are ridding on "flintstone tires"......because the tire cant flex properly to provide the ride, the handling, the traction, you name it, that they are designed to do..... and the contact patch they have is the size of a golfball, instead of a softball...... ie: it rains....they hydroplane.... corner too fast, they flip or slide.......

did this help?

First of all, I just want to say thanks for giving a nice full answer. I like to fully understand things, not just have an answer.

So this is what I took from what you just posted....

So basically, the car manufacturer's decide what pressure to run at for that specific vehicle. They take everything into consideration, figure out what size of a tire would work best, and give a recomended tire pressure based on that. When the tire manufacturers make a tire, they don't know what vehicle it's going to be on, and need to simply give a max pressure for a max load (that still enables the tire to function properly) to comply with federal regulations.

Am I on par???

[wolfdogs]

First of all, I just want to say thanks for giving a nice full answer. I like to fully understand things, not just have an answer.

So this is what I took from what you just posted....

So basically, the car manufacturer's decide what pressure to run at for that specific vehicle. They take everything into consideration, figure out what size of a tire would work best, and give a recomended tire pressure based on that. When the tire manufacturers make a tire, they don't know what vehicle it's going to be on, and need to simply give a max pressure for a max load (that still enables the tire to function properly) to comply with federal regulations.

Am I on par???

exactly on par, you see, a tire is nothing more than a pressure chamber, its the air that carries the load, not the tire...the tire is the vector that provides the traction and handling as in part of the suspension..while good old air keeps everything off the ground..... too low of an air pressure, and too high of an air pressure, makes the tire unhappy for a given load......

ride on broh........

[Jeanius]

Ive heard dropping the psi increases traction, is that true or bs?

[wolfdogs]

Ive heard dropping the psi increases traction, is that true or bs?

its true....but you cant do it for prolonged periods. ie: drag racing: drop the rear to 24psi. for the run. before you go home, pump it back up. minis 4psi for heat build up. in a drag race, you are not worried about lateral stabiltiy as much as street use...so it wont hurt for that short period of time.

by all means, never do that to the front tires....oversteer could kill you

[Jeanius]

its true....but you cant do it for prolonged periods. ie: drag racing: drop the rear to 24psi. for the run. before you go home, pump it back up. minis 4psi for heat build up. in a drag race, you are not worried about lateral stabiltiy as much as street use...so it wont hurt for that short period of time.

by all means, never do that to the front tires....oversteer could kill you

What size tire and PSI do you run on the Hawk?

[95TransAm]

exactly on par, you see, a tire is nothing more than a pressure chamber, its the air that carries the load, not the tire...the tire is the vector that provides the traction and handling as in part of the suspension..while good old air keeps everything off the ground..... too low of an air pressure, and too high of an air pressure, makes the tire unhappy for a given load......

ride on broh........

I can honestly say that by being a member on these boards, I have definitely changed how I view the importance of tires. So many things that I never had any idea about.

Appreciate the full and informative response.

[wolfdogs]

I can honestly say that by being a member on these boards, I have definitely changed how I view the importance of tires. So many things that I never had any idea about.

Appreciate the full and informative response.

well, nobody will agree with you more...... as the former manager of the Federal Tire Qualification testing program, I can tell you horror stories about tragedy that resulted from improper tire care and missaplications.

[wolfdogs]

What size tire and PSI do you run on the Hawk?

O.E. : p275/40R17 32 psi front, 30 psi rear.

on the Comp T/A, I ran 275/40r17 front, 285/40R17 rear. 32psi front, 30 psi rear.

for extended speeds in access of 65mph (like a long road trip) i ran 35psi all the way around...that gave a little better gas mileage and handling characteristics were not the lime light.

[01SSin502]

What Brand is the best?

I am at 24k and need to replace the original Eagle F1s. I like Goodyears but wow $$$ . Anybody have advise on cost/performance of BF Goodrich g-force or Firestone Firehawks?

[95TransAm]

I am at 24k and need to replace the original Eagle F1s. I like Goodyears but wow $$$ . Anybody have advise on cost/performance of BF Goodrich g-force or Firestone Firehawks?

Both of those are good tires, and a lot of the people on these boards like the g-force line as well.

www.tirerack.com will always be the best place for discounts, reviews, etc...

http://www.tirerack.com/tires/bfg/bfg.jsp click on which g-force tire you are looking for a review.

http://www.tirerack.com/tires/firestone/fireston.jsp click on which firehawk tire you are looking for a review.

Depending on what tire and size you get, you could be looking at anywhere from $110-$170 per tire plus shipping.

[Jeff_in_Atl]

My next tires will be these. $128.00 each. I have KDWs now. $187.50 each.
http://www.discounttire.com/dtcs/fin...34&rd=17&ar=40

[wrd1972]

My next tires will be these. $128.00 each. I have KDWs now. $187.50 each.
http://www.discounttire.com/dtcs/fin...34&rd=17&ar=40

I cant say enough good things about the Cooper 2XS zeon tires. I have 275/40/17 on my C6 rims. They hook up better than any tire I have ever owned. The run smooth, no shaking or shimmy. They are also very quiet.They are wearing amazingly well. And the price, OMG the price cant be beat. I will be putting these on my ride for life.

I got mine for $125 at a local dealer. No regrets as you can tell.

[Jeanius]

Werent BF Goodrich Comp T/A tires renamed to g-Force? I think i remember reading about that, anyone know?