How low can I go? Tire question

[Can Can]

If a 235/85/16 tire's maximum recommended inflation is 80 PSI, how low can I safely deflate it in order to soften up the way my truck rides? Any difference front to back considering it's a dually? The truck in question is an 89 V3500, if that matters.

 

[4X4HIGH]

I run my 315/75/16 at 45-47 psi on the street with no problems and my last set of tires had 50K on them.

The ideal way to figure out what tire pressure is best is to do a wet test where you wet the tread down and then drive over a piece of paper and adjust the air pressure until you get a full tread pattern showing, this will give you the best tire wear possible and i'm sure the best quality ride as well.

 

[Can Can]

That low, eh?

I had another very minor death wobble occurance the other day in the V3500, and I started thinking that if I aired the tires down from 80 PSI, the ride wouldn't be quite so harsh and the sidewall would be able to absorb some of the bumps in the road. As it is, the truck rides like a friggin' tank with all the tires at 80 PSI.

Does that line of thinking have any merit?

 

[Drey]

I run 35-40 in my SBlazer and always ran 45-50 in my K10.

I would think you could go down to 55-60 in the rear easily, big block in the front you may wany to stay in the 70 area. 80 PSI seems high for a "light truck" course Ive never owned a dually so who knows. Like 4x4high said wet test would help out, but dont go to low then your sidewalls will be effected

 

[Drey]

That low, eh?

I had another very minor death wobble occurance the other day in the V3500, and I started thinking that if I aired the tires down from 80 PSI, the ride wouldn't be quite so harsh and the sidewall would be able to absorb some of the bumps in the road. As it is, the truck rides like a friggin' tank with all the tires at 80 PSI.

Does that line of thinking have any merit?

Sure does CanCan, in the Terragators we run at work with BIG floatation tires im talkin 66x44s. THe applicators run 5 PSI less then recommended for a bit better ride. The tire guys put 5 more then recommended so they last longer

 

[tRustyK5]

80 psi should be the max pressure run. On the sidewall it should also state the max capacity of each tire at the max pressure. If you start doing the math you'll see that you are running a ton too much air.

Grim Reaper had a great method of finding your ideal tire pressure, and it just involves a bit of trial and error. Basically he'd check the cold tire pressure, drive for at least 10 minutes on the freeway and if the 'warm' tire pressure was under 10% more than the 'cold' pressure he'd lower the tire pressure a few lbs. If the 'Warm' pressure was more than 10% more than the cold pressure after 10 minutes on the highway he'd add some air.

Running near empty I'd run about 32-35 rears, and 40-42 front as a ballpark, then fine tune from there. If you were towing a heavy 5th wheel then I'd go 80 psi rears and still leave the fronts at 40 ish. The higher pressure keep the tires from getting hot when they have a lot of weight on them. When you don't have a ton of weight on them you just don't need that much air. The dual rears obviously carry less weight per tire than the fronts do, plus the empty rear of the truck is a lot lighter than the front.

Using Grimmy's method I found 27 psi was perfect for my old 35 x 12.5's (5700 lb K5). Those tires wore nice and even too.

Rene

 

[4X4HIGH]

Just keep in mind that as the tire heats up the air pressure is also going to go up. Somewhere on the tire it should also say what tire pressure is desired for that particular tire but that will vary depending on wheel width and vehicle. Once again, the wet test is the most accurate way of figuring out what air pressure to run. With dually wheels you need to make sure that the tires aren't so low that the sidewalls of each matting pair of tires does not come into contact with each other, air would need to be really low for that to happen though.

 

[neverendingproject]

80 psi should be the max pressure run. On the sidewall it should also state the max capacity of each tire at the max pressure. If you start doing the math you'll see that you are running a ton too much air.

Running near empty I'd run about 32-35 rears, and 40-42 front as a ballpark, then fine tune from there. If you were towing a heavy 5th wheel then I'd go 80 psi rears and still leave the fronts at 40 ish.
Rene

I agree. If your not hauling, 30ish in the rear and high 30's to 40's in the front. Even if your pulling a boat, I wouldnt put much if any air in the rear tires. 80 psi is if your hauling a gooseneck with a backhoe on it.

 

[BigBen]

I never run max pressure on the tire.... for some reason truck tires never seem to have 'recommended' pressures on them like cars used to.

As the others said, DON'T run at the max tire pressure!

As a start point, look at your owners manual or the tag on the truck. My '95 has a sticker on the driver's door with recommended tire sizes and pressures. I'm pretty sure my '85 had it too, and as I remember, your red truck looked mid-80's to me.

I've gotten 70k+ miles out of all my tires on my '95 (BFG A/Ts) just by running the pressure on the door sticker. (3 sets now of 265/75R16)
Hope this helps,

-Ben

 

[sweetk30]

sent ya some super info.

 

[79Stomper]

On my 285 R16's when hauling I run 65 rear 50 front and unloaded I run 40/40. So far has done me well. You can tell a difference between the 10/20 psi in the tires. Use the wet test. Or if you drive on a dirt road, just check your tires right after you get on it. Wet and pavement is the best though.