Mpg

[dually]

I took a trip this is what i came up with so far.

[Mopar1973Man]

Ummmm... You not a fully loaded at gross truck weight? There is no need for 80 PSI in the tires... Give you example... My Truck weights Front Axle 4,420#Rear Axle 3,040#Total -- 7,460# Tire Capacity 3,412# @ 80 PSI (Cooper STT 265/75 R16 Load Range E) 4,420# / 2 = 2,210# per tire front axle.5,200# / 2 = 2,600# per tire at GAWR (Front) 2,210# / 3,412# = 64% of tire capacity in weight2,600# / 3,412# = 76% of tire capacity at GAWR (Front) 80 PSI x 64% = 51 PSI Inflation pressure for the front.80 PSI x 76% = 60 PSI Max Inflation for GAWR (Even though tire is rated to 80 PSI) 3,040# / 2 = 1,520# per tire rear axle.6,084# / 2 = 3,042# Per tire at GAWR (rear) 1,520# / 3,412# = 44% of tire capacity in weight3,042# / 3,412# = 89% of tire capacity at GAWR (rear) 80 PSI x 44% = 35 PSI Inflation for the rear tires.80 PSI x 89% = 71 PSI Max inflation for GAWR (Even though tire is rated to 80 PSI) So over inflating tires does nothing for MPG's but it makes for a very rough ride and wears the center of the tread out rapidily. Oh yeah reduce your 2 cycle oil to 128:1 or 1 oz for every 1 gallon of fuel 1.5 quarts is a bit too much...

[ISX]

Dually that is awesome! I am on "vacation" and because I try and please everyone I had to go to branson and ride dirt bikes with that guy, I'm back home and now I gotta go to st. joe state park and ride with those guys, all pulling our trailer like a bat out of hell and the chart you made is dead nuts to what I saw. I don't know what it is without the trailer since I get around 23mpg the whole time but with the trailer I pretty well matched your graph mile for mile. I still have a little less than half a tank to burn off but it will be all trailer pulling mileage and then I can see what I got. Were you pulling anything?An interesting thing is it was 90F today and I still can't break 900F EGT at 70+mph up some 7% maybe steeper grades, trailer in tow. Boost was up to 20psi to hold 70mph, usually 15psi was enough. I wish I remembered how high it got stock. I was running it so hard I was at 207F coolant temp, it stops at 192F unloaded usually but the hills were longgg and I was in a hurry to get more ride time in Will be the same story tuesday morning when I go another 3 hours, cept the hills are even longer

[dually]

No on the pulling. Yes i know i put to much 2 stroke in. I had 1/4 tank before i started the trip and i filled up and added one quart. I had the tire pressure set at 80 in hopes to get the best mpg possible.Most of the time 70 psi is what i run. This was a mpg test. However i did have about 200 lbs in the bed.(junk) This dually has mud flaps and a windshiled visor that didnt help with the mpg.For 8300 lbs i am happy. I have a heavy flat cap that covers the bed.It is heavy. Michael funny you mentioned tire wear. This last wednesday before the alignment shop i put the inside duals on the front because they stay super flat. I looked at both front and they were both nice. After 475 miles i can see a problem. Today i rechecked the hub bearing for 180 lbs.The driver side is fine the passenger side must have positive camber problems.The outside is wearing.The front end is new but these axles do not have camber adjustment.So maybe i should replace the new ball joint with an adjustable unit? I tryed to move the tire when it was up in the air, it is solid no play at all.

[Mopar1973Man]

Hmmm. I would get ahold of the alignment shop again being they should have a warranty on there work. Let them look at it.

[dually]

I do have a warranty. From what i understand it has no adjustment. I have looked this up and some say bad ball joint,bent axle,bad bearing.The only cure i found is adjustable ball joint.

[Mopar1973Man]

Well that strange... Double check the front end again using a pry bar and check the ball joints for movement. Verical movement is fine but left/right movement is bad. 4WD axles have ball joint that do not articulate. It basically a round rod in a casing not a ball stud. Rather odd but yes offset ball joints will correct that but the tire / alignment shop would have to install them so they can set the chamber during the assembly process.

[dually]

Well i am at a loss. I did use a 3ft pry bar. There is no movement. It is a all moog front end. Say, if you were to guess would you say the upper ball joint is in need of adjustment or the lower. Myself, i think upper. The outside of the pass tire is bad.

[fire176969]

Well i am at a loss. I did use a 3ft pry bar. There is no movement. It is a all moog front end. Say, if you were to guess would you say the upper ball joint is in need of adjustment or the lower. Myself, i think upper. The outside of the pass tire is bad.

Does the truck pull to the right? Camber is not considered a tire wear angle. I agree it should be corrected but you need to look for another problem if your tires is wearing on one side, that is usually a caster or toe-in problem but it should be causing a pull to the right to wear the outside of the passenger front tire off.

[dually]

It seems to go down the road straight.When i stop it is also straight no pull.If i take a tape measure should the the rear of the tire match with the front to each other?

Example, if i measure 15in. off the ground in front and rear of the tire then go middle tread to middle tread should the front be the same as the rear?

--- Update to the previous post...

If i had a toe in problem wouldnt both tires wear?

[fire176969]

It seems to go down the road straight.When i stop it is also straight no pull.If i take a tape measure should the the rear of the tire match with the front to each other?

Example, if i measure 15in. off the ground in front and rear of the tire then go middle tread to middle tread should the front be the same as the rear?

--- Update to the previous post...

If i had a toe in problem wouldnt both tires wear?

Not necessarily would both tires wear if you had a toe in problem. It doesn't make sense for one tire to wear with no pull but it is possible obviously:lol: . As for measuring the toe, if thats what you were meaning by your example, you can't really go by the tread due to manufacturing differences in tires. Jack your truck up and spray paint a stripe on both front tires while rolling them and not moving the can, the using a jackstack or something to stabilize it take a screwdriver or awl and scribe a line in the paint. Set the truck back on the round and bounce the front end a couple times and take a sledge ans hit the rear of the sidewall to simulate the force of drag while driving then measure from the line scribed in the tires in both the front and the rear. The measurement should be atleast 1/16" less in the front than the rear.

[dually]

Thanks, before i do that i am going back to the shop and have it checked out again.Maybe the guy didnt understand me when i instructed him on what i wanted done. I showed him the control arms that i wanted set to spec.Maybe he didnt check the toe on the tie rods. Just looking at it parked i can see it looks off. This place has a good rep. Maybe i spoke with a new guy .

--- Update to the previous post...

Well bad news for me. I called the guy who 3 years ago told me about the alignment shop that i went to. He said they dont take trucks there any more because the place went down hill and now do lame work. Bummer for me. I have a warranty but i will not go back. I am working to go to a different place.

You know,this blows. The reputation of this place went form the steak house to the out house. I just wish i knew before hand.

I found a nice shop I hope they will get me in soon.

I filled up and some how i did 18.65 mpg that is the best ever !! I went 486 miles on 26 gal. of fuel. Today i filled 26 gal and reset the trip. I think thats good for a dually. Now to clear that up a bit, I filled up at a station that is 100 ft from the ramp to the freeway. So that is ALL freeway miles no city and it was almost non stop.

[fire176969]

That sucks about the shop going downhill but atleast you found another place. I do know that Sears or National tire and battery will never touch any vehicle I own ever again. I took mine to both places and ended up getting into heated arguments with both guys that tried to do an alignment on my truck. One of them stated that he has been doing them for over 20 years and has never had one not right after he was done. He didn't have an answer for why he didn't test drive my truck before and after to see if anything had even changed. He also didn't know that I watched him through the garage door the second time he had the truck in there. He put the sensors on the wheels and turned the steering wheel until the numbers on the alignment machine all turned green indicating everything was good then printed the paper and parked my truck outside.

[AH64ID]

Ummmm... You not a fully loaded at gross truck weight? There is no need for 80 PSI in the tires... Give you example... My Truck weights Front Axle 4,420# Rear Axle 3,040# Total -- 7,460# Tire Capacity 3,412# @ 80 PSI (Cooper STT 265/75 R16 Load Range E) 4,420# / 2 = 2,210# per tire front axle. 5,200# / 2 = 2,600# per tire at GAWR (Front) 2,210# / 3,412# = 64% of tire capacity in weight 2,600# / 3,412# = 76% of tire capacity at GAWR (Front) 80 PSI x 64% = 51 PSI Inflation pressure for the front. 80 PSI x 76% = 60 PSI Max Inflation for GAWR (Even though tire is rated to 80 PSI) 3,040# / 2 = 1,520# per tire rear axle. 6,084# / 2 = 3,042# Per tire at GAWR (rear) 1,520# / 3,412# = 44% of tire capacity in weight 3,042# / 3,412# = 89% of tire capacity at GAWR (rear) 80 PSI x 44% = 35 PSI Inflation for the rear tires. 80 PSI x 89% = 71 PSI Max inflation for GAWR (Even though tire is rated to 80 PSI) So over inflating tires does nothing for MPG's but it makes for a very rough ride and wears the center of the tread out rapidily.

My front axle weights about the same and if I ran 51 psi it would be squishy and corner like crap. My .01 has always been to run as much psi as you can, until you either hit a sidewall limit, tread contact patch limit, or a back limit... With a proper rim/tire combo the limit should be a sidewall limit. I can run 70/65 and have flat contact patches on my tires and a decent ride (as decent as the stock tires get). The more air you have the better mileage you will get from lower rolling resistance, and as long as the tread contact patch is flat/even you will get better tire life from cooler tread. Unless I am very heavy I keep my max psi to about 70-75.