Excessive rear tire wear

[Buzzinhalfdozen]

43 minutes ago, Mopar1973Man said:

I'd rather to the side of safety than being willy nilly and be over weight.

Quoting from IBMobile link...

 

 

 The only way I can see the rear tires wearing faster is the axle alignment is off. So it would be a matter of checking the axles for walking. Did you happen to break the centering pin in the springs? Possibly U bolt loose or rusted through? Kind of hard to see a rear axle moving unless there is some sort of damage.

Front axle is a different story being there is all the different axles you can apply to front tires on 2WD. As for 4WD trucks it more the typically ball joints, tie rods and/or track bar.

Good points and I'll go over everything again but I'll say it's doubtful. I put new springs hangers and U bolts in a year ago. Seems like the the more attention I give this rig the more it wants to fight back. 

[Mopar1973Man]

44 minutes ago, Buzzinhalfdozen said:

I give this rig the more it wants to fight back. 

It's a Cummins its going to fight till its totally wore out!

[IBMobile]

On ‎12‎/‎11‎/‎2015 at 5:43 PM, Buzzinhalfdozen said:

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One theory I have is maybe my rear limited slip isn't releasing and dragging the inside tire through corners? The only reason I say this is a while back something in the back made a binding/clanking noise through tight corners while I was towing. It sure sounded like an LS issue. Couldn't replicate the noise the next day and every thing looked good when I pulled the cover. 

 

To check that the LS diff isn't locked up, jack up the rear end and see if the rear wheels turn like a hypoid diff or if they are lock like a positraction.

 

On ‎12‎/‎11‎/‎2015 at 5:43 PM, Buzzinhalfdozen said:

So I put a new set of Cooper Discover at3 tires on about 3,000 miles ago. I looked at them today and the fronts are still new at 16/32nds but the rears are already worn to 13/32nds maybe a little less. 

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Is that measurement across the face of the tire, both sides and the middle, for both rear tires? 

 

Edited December 12, 2015 by IBMobile

[Buzzinhalfdozen]

15 minutes ago, IBMobile said:

To check that the LS diff isn't locked up, jack up the rear end and see if the rear wheels turn like a hypoid diff or if they are lock like a positraction.

 

Is that measurement across the face of the tire, both sides and the middle, for both rear tires? 

 

When I spin one tire they both turn together like a posi trac. The tread depth measurement was pretty much dead even across the face of the tire on both rears. 13/32nds on the LR slightly under that on the RR. 

[The_Hammer]

Ok, so you don't tow, don't drive gravel roads, don't do burnouts, and the treadwear is even across the tires, but your rear tires are wearing about 1/32 per 1k miles.

You need to verify without a doubt that your axle is square to the vehicle and that your limited slip isn't locked up. 

[AH64ID]

14 hours ago, IBMobile said:

I found this on the internet so it must be true.    http://auto.howstuffworks.com/auto-parts/towing/towing-capacity/vehicle/gvwr.htm

This isn't really the thread for the discussion so I won't go too far into it. But most of the stuff that article talks about is mute on these trucks. For most vehicles GVWR is a good number to know, on these trucks it isn't. Just look at FAWR+RAWR and it is much higher than GVWR. So is Dodge telling you that you are only safe with partial FAW/RAW?? No, what that says is each axle and the components can handle the axle weights listed but for other reasons the GVWR is lower than the combined sum. Marketing and DOT stops is a big reason. SRW trucks for years stopped at 9,900 to avoid the 10,000 GVWR rules for certain DOT stops, chain laws, etc. But once one company exceeded 10K with their SRW's all 3 did, and without any frame/brake/suspension upgrades at first.

Look around for a state law that makes GVWR a legally binding weight. I have and haven't found a state that uses that number yet.

15 hours ago, Mopar1973Man said:

I'm not foolish. That is all very dry spruce. Looks impressive but not even heavy enough to sit on the overload springs. Now this load of red fir was much heavier. You can clearly see its sitting down on the overloads. This one I crept off the hill really slow. I know I was pushing my luck.

Just a quick, and conservative, look at the math says you are a big heavier than you think.

You are stacked higher than the cab; however, for airspace reasons we will omit the wood above the cab. Cab height is 42.5", bed length is 101 but let's use 95" for room at the front/back. And the width varies from 49" to 64" so lets use 60" as an average as there is more space without wheel well than with. 242250 cubic inches, or 140 square feet of spruce. The lightest spruce is about 23lbs/cuft which puts your payload at 3,220 lbs. Unless your unladen RAW is 1,200 lbs you are heavier than you thought.

Dodge didn't do as good of job  in 2002 with publishing curb weights as they do now; however, I did find you should be around 6625 as delivered with a 4101/2524 split. That puts your rear axle weight around 5500-5700 depending on how much weight went on the front axle.

5500 lbs would need about 72 psi but luckily the math always comes out higher than the load/inflation charts at partial loading which is why 60 psi has probably worked out okay for shorter trips at those kind of weight.

People are almost always heavier than they think.

15 hours ago, TFaoro said:

I was saying that in the assumption that there is a reason behind the numbers. You could be and are likely correct about the marketing scheme. Thank you for pointing that out

In most vehicles that assumption is very accurate, but not in all.

[Buzzinhalfdozen]

10 hours ago, The_Hammer said:

Ok, so you don't tow, don't drive gravel roads, don't do burnouts, and the treadwear is even across the tires, but your rear tires are wearing about 1/32 per 1k miles.

You need to verify without a doubt that your axle is square to the vehicle and that your limited slip isn't locked up. 

Well when you say it like that I sure do sound boring!  Just to clarify I do tow trailers....down gravel roads...just haven't yet with the new tires. 

I should have an open stall in my garage by this afternoon (all my Junkers want my constant attention)I'll pull it in and go over it.

 

 

So riddle me this. If I jack up one rear tire with the trans in neutral how much force should it take to break the tire loose? I was told by a retired dodge tech that even with a strategically placed pry bar I'm not man enough to do this. If I'm not hearing any chattering or seeing/hearing a tire dragging on tight corners is it safe to say the LS is ok? I've been inside a lot more Chevy rear ends than dodge rear ends...

[The_Hammer]

@Buzzinhalfdozen

Wasn't trying to make you sound like a stick in the mud lol.

From your description the LS sounds like it's ok. One quick way to check your LS is to find a level grassy/dirt area, slowly begin to drive foward then make a turn. You will easily see if it's staying locked.

 

[IBMobile]

Another way to check the LS diff, block front wheels for safety, jack up one side of axle, put transmission in neutral, spin wheel by hand. It may take a little effort to spin but it should spin forward and backward. If it doesn't spin it's locked up.  

[Buzzinhalfdozen]

Well I finally got time to pull it in the garage but I don't have much for an update. What I can say is the the rear axle is perfectly centered and straight with the frame and the LS is functioning like it should. 

I don't have easy access to a scale but I did drop the rear tire pressure to 45psi in a heated shop which should put me at 40ish once the winter temps take over. 

So at this point I guess I'm giving up on it and hoping for the best. Maybe I'm just destined to spend all my money on tires.  Thanks for the help. 

[Vais01]

Just now, Buzzinhalfdozen said:

Well I finally got time to pull it in the garage but I don't have much for an update. What I can say is the the rear axle is perfectly centered and straight with the frame and the LS is functioning like it should. 

I don't have easy access to a scale but I did drop the rear tire pressure to 45psi in a heated shop which should put me at 40ish once the winter temps take over. 

So at this point I guess I'm giving up on it and hoping for the best. Maybe I'm just destined to spend all my money on tires.  Thanks for the help. 

Okay what size tire are you running? 

 

Also I use an old racing trick. Take a construction crayon and make a broad 2 inch wide stripe across the tread from shoulder block to shoulder block. Then driving down a paved road in a straight line drive roughly 1/8th of a mile to 1/4 of a mile check the mark. If the center is worn away you are over inflated. Wear the outer edges you are under inflated. Now if you are set perfect it will wear even across the mark on the tire. 

Just another tip tire scrub on the front tire will be high if the tire pressure is set perfect. In my case I added 3 PSI.

On my tires I run 67 PSI in the front and 60 PSI to 62 PSI in the rear. 

[Buzzinhalfdozen]

285/75/16 cooper discover at3. I'd like to try that chalk method but it's been sleet and snow here for the past month so a dry patch of pavement is hard to come by. Unless a 30ft run in the garage would do. 

[Vais01]

19 minutes ago, Buzzinhalfdozen said:

285/75/16 cooper discover at3. I'd like to try that chalk method but it's been sleet and snow here for the past month so a dry patch of pavement is hard to come by. Unless a 30ft run in the garage would do. 

Not so much. Might need to add a few zeros to that figure.

[dodgedieselnewbie]

I think I need to deflate some.. I bought new tires almost 3ooo miles ago and they were filled to 80 psi. I had no idea they should be down to 40-45 psi? I'll read back through this tomorrow and try to do the math.. too tired now to compute :-) 40-45... really?

[Mopar1973Man]

IIRC what I wrote in the driver side door is 57 PSI front and 43 PSI rear for standard empty driving for my truck weights. Now for towing its 53 PSI in the front and 57 PSI in the rear and I'm right at 160 pounds short of GVWR on the scale. So basically in a nutshell at full 8,800 pounds on the scale you should never be inflated over 60 PSI front and rear.

[dodgedieselnewbie]

My door says 65 front and 80 rear. I weighed my truck last week for the first time. 7200 pounds with me in it.. 

[AH64ID]

9 hours ago, dodgedieselnewbie said:

My door says 65 front and 80 rear. I weighed my truck last week for the first time. 7200 pounds with me in it.. 

That is based on the axle weight ratings, which is far more important than the GVWR. GVWR is mostly meaningless on these SRW HD pickups  

Don't exceed FAWR and tire/wheel limits on the rear and you are in good shape. Add the air for the load and it will be even better. 

Even thou my front axle weight decreases with a trailer hooked up I do not lower my pressure. The front axle gets lots of stress on winding roads and lower pressure would mean more heat and that's not good for tires or handling. 

Edited December 18, 2015 by AH64ID

[Mopar1973Man]

Just like my photo here... You can see I'm sitting on a 3 panel scale. This is my scale numbers for my RV but you'll get the drift.