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-   -   Tire pressure (http://www.diychatroom.com/f46/tire-pressure-149147/)

kimbokasteniv 07-04-2012 12:07 PM

Tire pressure
 
For years I have always filled tires to the pressure listed on the tire itself.

After looking around online, it seems that this is the wrong thing to do. So now I need some guidance.

I recently bought an old truck (98 chevy dodge ram 1500) with aftermarket tires (Uniroyal Liberator LT 245/75 r16 120/116q). The max pressure listed on the tire is 80 PSI. On the placard on the b-pillar 51 PSI is listed for the factory installed tires.
The tires were all inflated to about 30-40 PSI.

So how do I determine the ideal pressure for an unloaded truck?

Bondo 07-04-2012 12:27 PM

Quote:

Originally Posted by kimbokasteniv (Post 957712)
For years I have always filled tires to the pressure listed on the tire itself.

After looking around online, it seems that this is the wrong thing to do. So now I need some guidance.

I recently bought an old truck (98 chevy dodge ram 1500) with aftermarket tires (Uniroyal Liberator LT 245/75 r16 120/116q). The max pressure listed on the tire is 80 PSI. On the placard on the b-pillar 51 PSI is listed for the factory installed tires.
The tires were all inflated to about 30-40 PSI.

So how do I determine the ideal pressure for an unloaded truck?

Ayuh,.... Chevy/ Dodge,..??:no: :whistling2: :( :huh:

If the sticker says 51 psi,... that's yer answer...

terry603 07-04-2012 12:42 PM

i was taught,to be closer to the tire info than the car info. why? the car maker only cares about giving you the smoothest ride and not tire milage.
you get more miles on a tire blown up than at the car makers recommenation

this is a debate no body can win

kimbokasteniv 07-04-2012 01:20 PM

Shoot. I was really asking for it by putting Chevy and Dodge together... don't know what the heck I was thinking.

Otherwise, thanks for the help guys. I'll probably settle for a harder ride at 60 PSI.

rusty baker 07-04-2012 03:31 PM

If you run them too high, you could have a blowout. 60 quickly becomes 70 or 80 on a hot day.

cjm94 07-04-2012 03:32 PM

DOT specs tire psi can not be less than 50% of tire rating. So if you put 80 psi tires on the minimum is 40 no matter what the door sticker says.

rusty baker 07-04-2012 04:43 PM

Quote:

Originally Posted by cjm94 (Post 957869)
DOT specs tire psi can not be less than 50% of tire rating. So if you put 80 psi tires on the minimum is 40 no matter what the door sticker says.

I agree, but that could mean you have the wrong tires on the vehicle which may not be safe either.

ratherbefishin' 07-04-2012 05:11 PM

Quote:

Originally Posted by terry603 (Post 957741)
i was taught,to be closer to the tire info than the car info. why? the car maker only cares about giving you the smoothest ride and not tire milage.
you get more miles on a tire blown up than at the car makers recommenation

this is a debate no body can win

You were taught wrong, sorry. It's not just about smooth ride, it's about tread contact with the pavement. Overinflated tires crown, giving minimal tread contact and excessive wear in the middle of the tire. Underinflated flex dangerously in turns and wear on both edges. Properly inflated give proper handling characteristics and even wear. Most vehicles give specs for both dry and fully loaded conditions.

The debate was won long ago by the engineers who design, test, and build the tires and vehicles.

terry603 07-04-2012 05:33 PM

Quote:

Originally Posted by rusty baker (Post 957868)
If you run them too high, you could have a blowout. 60 quickly becomes 70 or 80 on a hot day.

not at all,the tire company already knows about increase pressure as the heat biulds up and takes that into account when they list their safe pressure. do you really think tire companies are going to leave themselves open for a law suit?

kimbokasteniv 07-04-2012 05:53 PM

Well I took another look at the placard and it seems the recommended pressure is actually 41 psi for p225/75 tires (not 51 like I stated earlier).
The current tires are lt245/75, which as far as I am aware seem to be similar enough--I just wonder if the fact that the custom tires are light truck designated warrants an increase in pressure.

So based on the warnings and information from you guys, I'm thinking 50 psi will be a safe bet.

bwilliams 07-04-2012 07:03 PM

Ratherbefishin has it right. The specification on the door is the one that you go by. And yes, safety is the reason. The tire size specified for that vehicle has a rated pressure which you should abide by. Going above or below it minimizes the performance and safety of the vehicle. If you are using tire sizes not listed for the vehicle, it is considered a modification, and you are on your own. Inflating tires to the maximum pressure is not a wise idea. Watch the Youtube videos from Michelin on overinflated or heated tires and ask yourself if you'd like to be there when it goes off. If it lends any credence, I am a 33 year technician and Professor in Motive Power.

polarzak 07-05-2012 06:46 AM

Quote:

Originally Posted by bwilliams (Post 957999)
Ratherbefishin has it right. The specification on the door is the one that you go by.

I agree. It has nothing to do with ride as someone suggested, but safety.

ukrkoz 07-05-2012 10:32 PM

1. you have to have right tires for truck - and for the job
2. you have right tires - you go by pillar B sticker
3. you add weight - you follow guidance in your manual how much to increase pressure according to the load added

So do not repeat my mistake, and mount 10 ply 70 psi rated tire on 1500 Silverado that hauls yard of dirt once a year. Of course, nice to take on curbs with those...


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