Fixing Out of round Tires

[dawico]

I am not sure if this is in the right section but here goes. I also tried the search function to see if this topic had been covered but didn't get much help.

My 14.00 r20 tires are out of round. I understand this is a fairly common problem with not only large tires but tires that have spent a long time sitting still. This is not only apparent because of the slow speed bumpy ride but also from jacking them up and spinning them. It is causing a very bumpy ride at highway speeds. 47 mph is the worst speed to drive in my truck. 55 is ok but still nowhere near smooth. I know it won't ride like a Cadillac but do expect improvement with the tires rounded out.

My MV is a 923a2 and the CTIS keeps the tires at 55 psi. I have 400 or so miles on it personally and the bumpyness doesn't seem to be going away. I have a mix of Goodyears and Michelins on now.

So driving on the tires doesn't seem to be helping. And let's be honest here, I am somewhat of a cheapskate and a do it yourselfer. I don't want to replace them as used tires may have the same issues and new ones are spendy. I am also guessing that getting them cut may be just as expensive and probably not very local to me.

So, any homegrown fixes that may work? I can add Shrader valves to them and run a different pressure if that may help round them back out.

I have a few ideas to try to cut them myself but thought I would see if anybody had success fixing their own issues.

Thanks in advance.

 

[ThatXJGuy]

I am about to try the antifreeze balancing, I'm not sure if you're aware of this or not but putting a gallon or so of antifreeze mix in each tire can yield good results, or so I have heard. I haven't tried it yet though so I can't say personally. I have a good buddy that tried the beads and it worked really well for him but it was just on 37" load range D tires.

 

[gringeltaube]

Before any cutting/shaving experiments...
Have you checked (radial) run-out immediately after say a 20 mile-trip, when the tire is still warm? How much are we talking - more than 1/4"?
Have you checked tire/wheel balance? I bet there is big part of the problem - and that can be solved.



G.

 

[dawico]

I am about to try the antifreeze balancing, I'm not sure if you're aware of this or not but putting a gallon or so of antifreeze mix in each tire can yield good results, or so I have heard. I haven't tried it yet though so I can't say personally. I have a good buddy that tried the beads and it worked really well for him but it was just on 37" load range D tires.

Balancing is my second concern, far behind the out of round issue. I can feel (and see) my truck rocking and rolling at 5 mph.

I didn't like balancing beads in my last truck. They clumped up if the tire had moisture in it plus if I checked the air pressure a bead would always get stuck in the valve allowing it to leak. I always had to have air handy just to check them to blow the beads out of the valves.

 

[Jason O]

Get them shaved! I tried balancing, etc with no improvement. Shaving, buffing, grinding the tires is the only thing that corrected the shake on my truck. I ran almost 1000 miles at varying air pressures hoping to wear the tires even, but only shaving corrected the problem. Even a tire which had NEVER been mounted on a truck was almost 3/8 inch out.

Going to do this on my other truck when time permits.

 

[dawico]

Before any cutting/shaving experiments...
Have you checked (radial) run-out immediately after say a 20 mile-trip, when the tire is still warm? How much are we talking - more than 1/4"?
Have you checked tire/wheel balance? I bet there is big part of the problem - and that can be solved.



G.

Running through town at slow speed I have a lot of wobble. Then I have about 40 miles of highway with a lot of bucking at certain speeds (47ish is the worst). Then slow speeds to the final location give me the same wobble. Temps here have been in the 60° range so I would imagine they get plenty warm. Ambient temperature and distance driven really show no difference in the tire feel.

It seems that I have atleast 1/2" of wobble all around the truck.

I don't think tire balance would cause much wobble at 5mph.

 

[Suprman]

If the front tires sat flat for a period of time I would not want to drive on them. The older style Michelins are notorious for blowing out. Especially if the sidewalls are really wavy. What are the date codes on the tires?

 

[dawico]

Get them shaved! I tried balancing, etc with no improvement. Shaving, buffing, grinding the tires is the only thing that corrected the shake on my truck. I ran almost 1000 miles at varying air pressures hoping to wear the tires even, but only shaving corrected the problem. Even a tire which had NEVER been mounted on a truck was almost 3/8 inch out.

Going to do this on my other truck when time permits.

Did you do it yourself or have a shop do it?

If you did it, how?

If you had a shop do it, how much did it run you (if you don't mind me asking)?

 

[dawico]

If the front tires sat flat for a period of time I would not want to drive on them. The older style Michelins are notorious for blowing out. Especially if the sidewalls are really wavy. What are the date codes on the tires?

I have Goodyears on the front. I blew out a Michelin on the front and swapped both out for Goodyears.

Even if I bought new tires I may still have the same problem.

 

[Jason O]

I had a shop shave the tires. The procedure was performed with the tires on the truck. It took about half a day, im thinking I paid around $40 per tire.

I'll post a pic later.

 

[Suprman]

I like the goodyears I think they ride a little nicer than the Michelin XZL's though the Michelins are probably better for offroad traction.

 

[dawico]

I like the goodyears I think they ride a little nicer than the Michelin XZL's though the Michelins are probably better for offroad traction.

I like the Goodyears because they do not have directional tread. Two of my Michelins are backwards and it drives my OCD nuts.

Most of my wobble comes from the front where the Goodyears are though.

 

[gringeltaube]

Well, if any of the front tires (after warmed up) still had a run-out of 3/8" or more I would better NOT run them on the steer axle - shaved or not!



G.

 

[Artisan]

I want to learn more about the A2 variant so I went and did some sleuthing.
I have a lot to say, not a mean spirit within...

Does the TM say 55PSI is OK for normal, on road use, at speed?
I didn't think so.

The -10 TM says;
HWY MODE
The highway tire pressure selector is the normal operating mode of CTIS. The HWY mode (Figure 1, Item
is 90 psi (621 kPa) (80 psi (552 kPa) for M936A2 wrecker). If a lower tire pressure mode had been selected the last time the vehicle was operated, CTIS will automatically begin to inflate to the highway setting.

and

Hwy Mode. CTIS highway selection is automatically programmed HWY (Figure 1, Item 4) when you start the engine.

and

Highway (HWY)
(M939A2 Series Vehicles)
Tire pressure selector is the normal operating modes of CTIS.
The highway mode is automatically set each time the engine is started.

So the truck was designed to run at 90 PSI normally, and you are at 55 so problem #1.
This needs to be addressed immediately.

55 PSI? ...and what is the "factory recommended" normal tire pressure called
out at as written right on the tire? It is ONE HUNDRED PSI COLD, right? But
the TM is clear, 90 PSI so it overrules the Mfg in my book so 90 it is.

You are WAY under pressure running at ONLY 45%? of what the TM says
they want the tire pumped up to at speed? Why??? Because the CTIS
has it there? I don't care what the CTIS is doing read the TM, and
you said you were driving at 55MPH, I assume this is not off road
and you are on-road in normal conditions, 90 PSI is where every
tire needs to be at, not a penny less.

Fix the CTIS but,

First thing I would do is disable the CTIS 100% and fill all tires manually to 90PSI.
Go back in 1 hour and recheck pressures, looking for leakers.
MAX air all of them up to NINETY PSI COLD, not a penny less
just like the TM engineers designed the truck to run at
and let it sit for a couple of days, but move the truck so the tires spin
only 90* twice a day to try to ensure your not sitting on a flat spot.
If you can see where a flat spot is after full pressure throw the tire away!

Side Note;
I have personally witnessed big deep cracks in these tires and flat
on the ground. I filled it w/ air to 100 and the crack disappeared!!! Scary!
Freaking CRAZY but I saw it w/ my own eyes. (Not on my truck,
on 7 like trucks I towed once off base.)
End Side Note:

After a couple of days don your driving gloves, make sure spare is aired
up and chain-fall and irons and jack are onboard (or carry phone
number to the local mobile tire repair guy!) BIG $$$, and
filler-up and take it for a spin for a couple of hours @ 55 MPH,
down the freeway, w/ a couple ton onboard, non stop and report back
to us.
(Check pressure in EVERY TIRE twice a day, if a small leak
is proven AIR IT UP to 90 psi. Not an RCH less.) I bet you
see a difference.

If your worried about anything blowing and you not being
able to handle it, sell it, or go buy new steer axle tires, but that is
no assurance you will not have a blow out leaving road
alligators in your wake and the truck dropping 10"-12" in a split
second, at speed, and that rim hitting the bead w/ a flopped
over tire and the steering wheel being tired to be yanked & pried
out of your control, pray not in an opposite turn as in a right,
front flat, in a left turn. No granma's mittens, no slippery material gloves,
only good worn in slightly dirty leather gloves or non slip gloves.
NO SLIPPERY GLOVES / HANDS EVER driving these beasts!

Hands at 9- O:Clock and 3- O:Clock holding VERY firm, like
you could have a blow out at any minute, because you could,
even w/ new tires. Certainly the chances are slim to none
w/ new tires but the possibility is there.

These are tactical military vehicles, comfort was never an option.
Wearing helmets was mandatory too!

If you still have a problem shave away, but I don't think I would
shave an old steer axle set of tires, just get anew. I myself
am saving for a brand new set of steer axles tires. PUNT!

 

[Suprman]

The tires are designed to be retreaded. There should be plenty of meat if you want to take a bit off the tread area. A crack isn't going away no matter how much pressure you put in it. I think 100 psi in an older tire might be pushing it a little. You would have a hard ride. I try to stick with 65psi or so.

 

[dawico]

I want to learn more about the A2 variant so I went and did some sleuthing.
I have a lot to say, not a mean spirit within...

Does the TM say 55PSI is OK for normal, on road use, at speed?
I didn't think so.

The -10 TM says;
HWY MODE
The highway tire pressure selector is the normal operating mode of CTIS. The HWY mode (Figure 1, Item
is 90 psi (621 kPa) (80 psi (552 kPa) for M936A2 wrecker). If a lower tire pressure mode had been selected the last time the vehicle was operated, CTIS will automatically begin to inflate to the highway setting.

and

Hwy Mode. CTIS highway selection is automatically programmed HWY (Figure 1, Item 4) when you start the engine.

and

Highway (HWY)
(M939A2 Series Vehicles)
Tire pressure selector is the normal operating modes of CTIS.
The highway mode is automatically set each time the engine is started.

So the truck was designed to run at 90 PSI normally, and you are at 55 so problem #1.
This needs to be addressed immediately.

55 PSI? ...and what is the "factory recommended" normal tire pressure called
out at as written right on the tire? It is ONE HUNDRED PSI COLD, right? But
the TM is clear, 90 PSI so it overrules the Mfg in my book so 90 it is.

You are WAY under pressure running at ONLY 45%? of what the TM says
they want the tire pumped up to at speed? Why??? Because the CTIS
has it there? I don't care what the CTIS is doing read the TM, and
you said you were driving at 55MPH, I assume this is not off road
and you are on-road in normal conditions, 90 PSI is where every
tire needs to be at, not a penny less.

Fix the CTIS but,

First thing I would do is disable the CTIS 100% and fill all tires manually to 90PSI.
Go back in 1 hour and recheck pressures, looking for leakers.
MAX air all of them up to NINETY PSI COLD, not a penny less
just like the TM engineers designed the truck to run at
and let it sit for a couple of days, but move the truck so the tires spin
only 90* twice a day to try to ensure your not sitting on a flat spot.
If you can see where a flat spot is after full pressure throw the tire away!

Side Note;
I have personally witnessed big deep cracks in these tires and flat
on the ground. I filled it w/ air to 100 and the crack disappeared!!! Scary!
Freaking CRAZY but I saw it w/ my own eyes. (Not on my truck,
on 7 like trucks I towed once off base.)
End Side Note:

After a couple of days don your driving gloves, make sure spare is aired
up and chain-fall and irons and jack are onboard (or carry phone
number to the local mobile tire repair guy!) BIG $$$, and
filler-up and take it for a spin for a couple of hours @ 55 MPH,
down the freeway, w/ a couple ton onboard, non stop and report back
to us.
(Check pressure in EVERY TIRE twice a day, if a small leak
is proven AIR IT UP to 90 psi. Not an RCH less.) I bet you
see a difference.

If your worried about anything blowing and you not being
able to handle it, sell it, or go buy new steer axle tires, but that is
no assurance you will not have a blow out leaving road
alligators in your wake and the truck dropping 10"-12" in a split
second, at speed, and that rim hitting the bead w/ a flopped
over tire and the steering wheel being tired to be yanked & pried
out of your control, pray not in an opposite turn as in a right,
front flat, in a left turn. No granma's mittens, no slippery material gloves,
only good worn in slightly dirty leather gloves or non slip gloves.
NO SLIPPERY GLOVES / HANDS EVER driving these beasts!

Hands at 9- O:Clock and 3- O:Clock holding VERY firm, like
you could have a blow out at any minute, because you could,
even w/ new tires. Certainly the chances are slim to none
w/ new tires but the possibility is there.

These are tactical military vehicles, comfort was never an option.
Wearing helmets was mandatory too!

If you still have a problem shave away, but I don't think I would
shave an old steer axle set of tires, just get anew. I myself
am saving for a brand new set of steer axles tires. PUNT!

I just skimmed the TM and it does say 70psi for the front and rear tires (the 939 series with 11x20 tires says 90psi). I guess I got mixed up with the 55mph speed limit or something. Last time I worked on one of the tires I manually aired it up to 60 psi and let the CTIS system have it from there.

But in all honestly I have not checked the tire pressure manually. Add that to my list.

As far as changing a tire or having a blowout, been there and done that on both counts. Not a problem at all.

 

[Artisan]

I just skimmed the TM and it does say 70psi for the front and rear tires (the 939 series with 11x20 tires says 90psi). I guess I got mixed up with the 55mph speed limit or something. Last time I worked on one of the tires I manually aired it up to 60 psi and let the CTIS system have it from there.

But in all honestly I have not checked the tire pressure manually. Add that to my list.

As far as changing a tire or having a blowout, been there and done that on both counts. Not a problem at all.

That's all fine and dandy but let's try to fix the flat spot issue first,
then after a few months if you want to let a lil air out that is
your prerogative. (Not recommended)

Pump those puppies up to MAX and let them sit.

 

[dawico]

That's all fine and dandy but let's try to fix the flat spot issue first,
then after a few months if you want to let a lil air out that is
your prerogative. (Not recommended)

Pump those puppies up to MAX and let them sit.

Will do. I am about to go out of town for a week for Christmas so I will air them up and see if it helps. I would have to disable the CTIS to keep them up though. If a week at full pressure makes any difference then I will persue that option. I honestly don't hold out much hope but I will try it.

Thanks.

 

[tennmogger]

There's one important factor you'all are leaving out: load on the truck. The military pressure recommendations are for maximum payload (the safe way to set spec) and the pressure stamped on the tire is at rated max payload. That does not mean you have to run those pressures.

Running max pressure at reduced truck payload results in the middle of the tread wearing out much faster. The tires will be bald in the center and tread left on the outer edges. The tire footprint will be much smaller resulting in poorer braking on the highway, and much reduced float offroad. You will sink is the soft stuff. There should be road contact all across the tire face. Of course CTIS takes care of that but it does not know what load you have. That's where human decision is important. Lastly, the ride will be rough at max tire inflation. Reduced pressure will make the ride much more comfortable and reduce shock load on the tires. Most tire manufacturers will publish a chart for load (usually percent actual load compared to maximum) vs desired tire pressure. Keep in mind that the front tires and rear tires may have considerably different loads on them and should be inflated to compensate. Rolling radius should be matched front to rear, too, or your drivetrain will bind up in 4wd. That is, the front tires and rear tires should roll the same revolutions per distance. Rolling radius is wheel center to ground dimension. Obviously that changes with load and pressure.

I routinely regroove tires (Michelin XL's, 14.5 x 20). They are regroovable. Each state has specifications on how much rubber has to remain above the cords to be legal. If you think about the tire strength, it's the cords and what is inside them that holds the pressure. The rubber outside the cords is in tension and holds very little pressure because rubber stretches by it's nature. The concern is protection of the cord from the elements and road hazards. Regroove to your hearts content and get more mileage out of those tires.

Truing tires can be done if you find some place that still has the machine. I personally use a rubber cutting disk as used by hotrodders to create road slicks. They cut away most of the rubber from a tire to lighten it and put more rubber on the pavement. The disk looks like a very aggressive sanding disk. By jacking up one wheel at a time and rotating the tire just above the flat surface, high spots will drag and mark themselves. This is a time consuming process.

Once the high spots are cut off the tire will be 'true' but probably not balanced better.

Yes, some tires were meant to be retreaded, some not. I think the important issue is regroovability. Do the tires say 'regroovable"?

Bob

 

[Artisan]

THANK U Bob, I am listening. I wonder if the TM's address this and I did not read enough?

Bob penned;
"Most tire manufacturers will publish a chart for load (usually percent actual load compared to maximum) vs desired tire pressure."



Great!

Now I get to go on a 14:00R20 tire pressure "chart" hunt.
Maybe someone will (hopefully) beat me to it and find it before me! HA!