tire pressures/mileage

[Hobart]

According to the maker's tire pressure chart I should be running about 50lbs front and rear. Thats at 4000lbs max on the front end so 2000lbs a tire = about 50lbs; and 7000lbs max on 4 tires in the rear or 1750 lbs a tire equaling about 45 lbs a tire. This is loaded with a Bigfoot cabover. But when I bought new tires the other day the dealer insisted on inflaing to 70lbs front and rear. I'm finding that high pressures just wear out the center of the tire. But do my low pressures adversly effect mileage? Who's right here.

 

[rweis]

I put nitrogen in my van tires and all other things were equal, no changes to tp, same terrain, same daily drives, same engine (ie no tune up), same fuel grade. 10k later:



MPG +2



Interesting,



Bob Weis

 

[SnoKing]

Should be a tire pressure chart in the glove box or fine one online. They should be the same from all manufactures. I think 50 in the front is a little to low. I run 57 in my 2500 with 265's. Chart should help you with the correct air in the dually rear. SNOKING

 

[JFaughn]

The pressure to go by is marked on the tire , whats on the truck is only right if you have the same tires that came on the truck .
My tires say 80 lbs and thats what I'm running at , I've even tread wear on tires I bought from junk yard , Firestone Steeltech 265 70r 16 , one pair had a little of the nubs left on the outside cornner , must have been rear , so I guess they had less than 10,000 , now 43,000 about 1/4 - 1/3 left , but I'm cheating I put on the Centermatics after about 25,000 , had some chop wear , shocks old , rotated tires when I put the Centermatic's on , no more chop on front tires , still haven't put shocks in .

 

[EricBu12]

50 is too low with a camper on... if you have a dually, you can go 65 rear and have enough squish to keep even tread. on the tire preasure chart. always go 5 to 10 psi over that and the tire won't get too hot. Remember, that is the RATED weight for the pressure. . so go higher. . In fact, if you have E tires, go 60 front and 70 rear and you won't have any problem. Low tire will affect milege but not much. . I have 19. 5" rims on F rated 12 ply tires and I run max 95 psi when towing and my pin weight is a little less than your camper weight... . My 5th wheel has 6 tires and close to max rating when loaded..... when I air up cold, I go 68 psi. . 3 psi over max cold. this helps fight heat when towing. they still get to 74 psi when hot... . Tire pressures will go up when hot but not as much as underinflated tires will... . then they shred!

 

[SnoKing]

The pressure to go by is marked on the tire , whats on the truck is only right if you have the same tires that came on the truck .

My tires say 80 lbs and thats what I'm running at , I've even tread wear on tires I bought from junk yard , Firestone Steeltech 265 70r 16 , one pair had a little of the nubs left on the outside cornner , must have been rear , so I guess they had less than 10,000 , now 43,000 about 1/4 - 1/3 left , but I'm cheating I put on the Centermatics after about 25,000 , had some chop wear , shocks old , rotated tires when I put the Centermatic's on , no more chop on front tires , still haven't put shocks in .

That is just wrong, and for dually's it is double wrong. four tires on the rear of a dually would be for around 12K on that axle at 80lbs, and that is not going to happen. If you call Michelin customer service, they will tell you to follow the inflation chart, that includes for trailer tires. Lady told me that the max side wall air is one of those internet/urban legends that is flat wrong. SNOKING

 

[HighRanger]

I run 60 all the way aroung on my 04. 5 Dually, last set of tires ran 50k and were flat all the way across all 6. Only thing I really tow is a 4200# jeep on a 1600# trailer.

 

[EricBu12]

Every commercial truck that is running empty around the states don't air up and down for the weight. . I know it is short term on that but the weight on the trailers goes up and down from light to heavy. . all the time the tires are at max cold. 95 rear and 110 front. . I do the pressures on the above post I did and get 11 mpg towing. tires run cooler and last longer. Now, 80 psi on rear and unhooked all the time, then yeah, air down a bit. But if you are hooked to the camper 50% of the time or more, air them up... you don't need max, but highr than the chart says. . go by that 5 to 10 psi extra rule and you won't go wrong.

 

[TBartlett1]

You are right if inflated to max pressure it will wear the middle of the tire. I have found that through trial & error that 50r & 60f is good for my empty truck. I suspect that the dealer is playing it safe to avoid legal issues like Ford and Firestone had. Depending on the tire size and weight of truck this pressure will vary to achieve a good ride and even tire wear. When I intend to load it I will put max pressure in tires. What I've done in the past is to record the tread depth with a machinists rule to the nearest 1/64 of an inch and monitor the wear and adjust as necessary. I have also found that the right rear tire wears the most followed by the left rear the fronts are a toss-up, and when rotated the best tire goes on the RR. I have gotten very good mileage from my tires doing this.

I recently used a laser level and tape measure to determine what pressure is needed front and rear in my new truck (1999 W25004x4) to attain the same height (rolling dia) so that when in 4wd there is minimal driveline stress.

Hope this helps

Tim

 

[WestTN]

The sidewall pressure rating is NOT an internet thing. You cannot use your computer to print on the tire. The tire manufacturer molded that in rubber.

Next: I never run less than 60 psi in my truck tires. I got 97,000 miles on the first set and NO treadwear indicators were showing. I changed them to avoid hydroplaning. I do run 80 psi in the rears and 70 psi in the fronts when carrying my 8' sportsmen camper.

Radial tires will NOT wear in the middle with higher inflation pressure as long as they are the right size for the rim width. Bias ply tires will. This is also why I never run oversize tires.

And last but not least, air is 78% nitrogen. 100% nitrogen does not work miracles. The tires probably run cooler because they were pumped up to the proper pressure for the load.

It is common to change unconsciously driving habits when trying to check fuel mileage.

 

[SnoKing]

The sidewall pressure rating is NOT an internet thing. You cannot use your computer to print on the tire. The tire manufacturer molded that in rubber.

QUOTE]



I was referring to people that say run the pressure listed on the sidewall of the tire. It says - in my case 'max load single 3415 lbs at 80 psi'. The tires do not normally carry 3415 lbs each, therefore less air is required for proper inflation. That is what the inflation chart is for, to determine the correct PSI to inflate to. At 70 lbs of air, my 265/75/16R LR E equal the rear axle rating. Yet some people drive around with them at 80 PSI all the time. MY TRUCK HANDLES LIKE CRXX at that much air in the rear.



I run 65-70 towing the 5er and 42-44 empty. If I go for a 1. 5 to 2 yards of grave, I put 80 lbs in them.



SNOKING

 

[AKaiser]

www.klenger.net/dodge/index.html for the charts. See under references.

 

[TowPro]

This question is not something new. I can remember the Corvair called for something like 16psi front and 32psi rear. People would read the side wall and put 32 in all the tires. This caused many corvair crashes since the car under steered bad with to much pressure in the front tires. By 1965 GM fixed the problem with a suspension redesign but it was to late, Ralf nadar had already started his crusaid.

I use the load charts, then add 5psi for highway speeds.
I also wore out the center of a set of Goodyears on my 98 (in 12,000 miles you could see the center wear). I was using the pressure specs Dodge published. I called Dodge and raised heck, they replied "when we say empty, we mean not carrying a load, but full of tools". to me empty is just that, EMPTY!