BFG AT KO + pressure

Messages
174
Location
Phila., PA
What pressure do you truck guys use with this tire? I was running 35psi, which my truck maker suggests but my mpg is really suffering. At 35psi it seems the tire is over-gripping(I'm sure I'll appreciate this in the snow [Smile] ) so to speak. Any suggestions?, 40 psi maybe? [Cheers!] thanks
 
Messages
572
Location
Ontario, Canada
Take a look at the thread and the side edges of the outer thread blocks. Does it look like the tire has scrub marks from getting "over squished"? If so, increase your pressure, and keep looking at the thread to see what its telling you. Anytime you change a tire type you may have to make adjustments to pressure. I used to run BFG radial TAs at 36psi on a vehicle, I now run Firestone Indy 500's (same size) but need to run at 44psi to get the tire response how I like it. Alex.
 
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3,939
Location
Somewhere in the US
You need to take a look at your vehicle placard and see what the original tire size and inflation was. If you are using the same size, then that would be thr proper inflation - although 3 to 5 psi more than that would be OK. I'm hoping that GM guy isn't using 44 psi in a P metric standard load tire. That's the maximum allowable and at that pressure impact breaks might be a problem.
 

phillyFX4

Thread starter
Messages
174
Location
Phila., PA
CR, I'm running the stock size tires, increased pressure to 40psi and went surf fishing at the NJ shore, truck REALLY seemed to roll alot effortlessly with the increase. Think I'll keep them at 40psi.....till it snows. [Wink]
 
Messages
572
Location
Ontario, Canada
The Firestones are rated for 44psi. Obviously I don't necessarily agree with rating placards. My work van calls for something like 55psi front, but it steers like a pig with 55psi. It gets 70psi. Rears are 80psi as per the placard. You'll also enjoy the fact I run 38psi in a 35psi rated tire on one of my vehicles...and it still tends to roll onto the sidewalls. Alex.
 
Messages
3,939
Location
Somewhere in the US
GM Guy, Let me do this in reverse order, because it makes more sense. 1) Your 35 psi rated tire - can be inflated to 44 psi, so from my perspective 38 is OK. There's a part of the tire standard that says the load curve ends at 35 psi, but there are certain circumstances where higher inflation pressures are called for - high speed operation is one of them. But the law that applies to what is written on the sidewall is not quite clear which of these 2 figures is right and different tire manufacturers do different things - even though the standard is the same! So the same size tire could have either of these values and there's no difference in the tire - just the way the law is interpreted. 2) Vans? Unfortunately steering like a pig is what vans do! Sow's ear / silk purse comes to mind! So long as you don't exceed the max on the sidewall it's OK (for LT metric tires) For some reason, even though the same standardization rules apply to LT metric tires, everyone seems to agree about what gets put on the sidewall - the pressure at the end of the load curve. I'll have to look again to see if the law reads the same (It's a different regulation!) 3) But when it comes to P metric tires, if 44 psi (or 51) is written on the sidewall, I'd be careful using the tire at that pressure. (Read #1 above.) While steering response gets quicker as you increase inflation pressure, impact resistance goes down. Just use caution!
 
Messages
572
Location
Ontario, Canada
I mistook your referecne to the placard as being the be-all end all inflation recomendation for a tire (the same size that is). I can tell you that bumping fronts on the van up from the placard value improoves steering response dramatically. It goes from fat grazing pig, to lean pig. =-) Alex.
 
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