Severe wheel hop

[AKPacker]

Sorry for the delayed reply, it did get it mostly resolved (thankfully very simply!) and I've been busy putting some miles behind me for the last couple of days (in Canada now). Before swapping a front wheel for the spare, I tried changing tire pressures to see if that had any affect. I lowered them all to 65 psi and that didn't make much of a difference, so I pumped them all back up to 85 psi, and it went from feeling like a bucking bronco at certain speeds to just feeling like a slightly out of balance tire again, yay!?

I'm still not completely sure of the cause and I plan to tear my front wheels apart when I get home to investigate. My theory is that it is related to the balance beads clumping/not distributing correctly. The compressor I originally used to inflate the tires didn't have an air dryer and it was quite humid in Illinois, so a lot of moisture got into the tires. Maybe this caused the beads to clump up and throw the tire way out of balance? When I aired them back up it was in Wyoming, so maybe the dry air helped?

It was definitely wheel hop/vertical motion, there was very little if any shimmy to the steering wheel and it tracked straight down the highway, it was just bucking so much that I didn't feel safe driving it that way. There is still a small amount of hop at certain speeds, especially around 55 mph, but it just feels like a slightly unbalanced wheel and doesn't feel unsafe anymore. Once it gets up past 60, things smooth out and it is cruises along beautifully all the way up to 70.

This is my first time running balance beads, but their dynamic nature is the only reason I can think of why the tite balance would change so much depending on speed. On every other vehicle I've had, a tire was either out of balance or it wasn't, it didn't change depending on speed like these seem to.

I really appreciate all the suggestions and info from everyone, one of the reasons I decided to finally pull the trigger on this truck is because that I knew there was so much knowledge/technical support available from the people on this forum, thank you all!

 

[gringeltaube]

My theory is that it is related to the balance beads clumping/not distributing correctly.

You said "brand new tires with balancing beads". But do we know for sure that you are running with just beadlocks - and all dry and clean inside?
Because normally, tires with runflat inserts also have (should have) that special grease - which obviously would cause exactly what you stated above...(?)

 

[AKPacker]

Yes, the tires and run flat inserts were completely clean and dry when assembled. I did not add the run flat grease/soap since I would not be driving any significant distance in the case of a flat tire.

 

[GeneralDisorder]

@Lostchain has had similar "issues" with balance beads - don't seem to do anything useful. I've said it before and I really haven't changed my mind despite my tests with anti-freeze, etc as dynamic balancing - these tires don't have balancing issues for the most part. They DO absolutely suffer from flat spots and the only remedy I know of for that is to DRIVE the truck regularly. Perhaps putting the truck up on jack stands without weight on them would help - I don't know of anyone that has done this over a period of time and can offer experience.

My experience has been that the tires have flat spots that stack up in different ways as they slowly rotate at slightly different speeds while driving. When the flat spots are aligned the truck experiences a straight up and down input as the flat spots roll under the tires in unison. When they stack up 180 degrees apart the truck will experience a more gentle see-saw motion. So as you drive and perform gentle turns, the tires rotate with respect to each other and the "gallop" will fade in and out as you drive. The Michelin XML's were nasty for this behavior due to the lug design. The MV/T is better but you don't want to let them sit and they do have a break in period from new it seems like. Over about the first 5,000 miles they will limber up and if driven daily they will work themselves into being very smooth.

Basically - drive the truck and it will sort itself out. Don't drive it and nothing you do will completely resolve the symptoms. That's been my experience FWIW.

I don't see how a truly "out of balance" tire would have this fade in and out behavior - in all my experience with tire balance issues they just vibrate constantly at whatever road speed is sympathetic. Every one of these trucks I have driven or ridden in that had this "problem" has the fade in and out symptom.

 

[Keith Knight]

He disappeared off of here. Hope he got it going.

 

[GeneralDisorder]

He disappeared off of here. Hope he got it going.

He posted at 5:43 AM this morning (post #23) so it appears to my browser that he's still checking on the conversation.

 

[aw113sgte]

6x6 and 2014 date code tires, once I added some weight on the back probably about 6000lbs, put pressures to 85 it smoothed out pretty well. Still get some vibration when tires get in sync but its not a big deal. Don't plan on balac beads or liquid as the issue is so minor.

 

[AKPacker]

Yep, I'm driving through Canada with intermittent internet service right now. Drove another 615 miles yesterday, the vibration/hop has been tolerable and still varies greatly depending on speed. It is worst around 55 mph/90 kph which is rough since that is the speed limit on a lot of the roads we traveled yesterday and will travel today. If I slow down to ~50 mph or speed up to ~61 mph it smooths out quite a bit.

 

[Xengineguy]

Im assuming you have stock steel wheels. If you do, remove one or two nuts that hold the wheels together .
look to see if the studs are in the centre. If not the whole wheel is off. 1/16” is a lot when the wheel /tire
weighs 300 lbs. When I do mine I use steel alignment sleeves over the studs to make sure they are true.
I also have a special set of nuts to align the wheel to the lug studs. ( I don’t rely on the taper of the lug nuts to center the
wheel.) After the wheel is snugged I remove the special nuts and finish installing the rest of the stock nuts.
Hope this makes sense

 

[GeneralDisorder]

Isn't the point of the tapered lug nut to ensure it's centered? These aren't hub-centric wheels - those would use flat lug nuts.

I mean - it can't hurt. I just use three of the lug nuts and run them down in stages and then visually confirm the wheel was centered in this step before locking them all down and torquing.

 

[Third From Texas]

I was wondering if it could be related to the run flats. But I've never dealt with them so it's just a wild guess.

 

[Xengineguy]

Isn't the point of the tapered lug nut to ensure it's centered? These aren't hub-centric wheels - those would use flat lug nuts.

I mean - it can't hurt. I just use three of the lug nuts and run them down in stages and then visually confirm the wheel was centered in this step before locking them all down and torquing.

Yes they are tapered lug nuts. In a perfect world they should center and be fine. I had one wheel that was damaged at the lug nut tapers from not tightening correctly. it’s now my spare. I use the nuts shown to make sure the wheel studs are true, then tighten the tapered nuts. These wheel tire assemblies are very heavy as you know. I don’t trust the taper to lift/center the wheel. Just a different way to do the same thing.

 

[Ronmar]

And lifting one wheel and chocking the ones left on the ground will allow you to spin to look for out of round/out of true conditions.

 

[coachgeo]

guess anything is possible

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[Lostchain]

This is my first time running balance beads, but their dynamic nature is the only reason I can think of why the tite balance would change so much depending on speed. On every other vehicle I've had, a tire was either out of balance or it wasn't, it didn't change depending on speed like these seem to.

I have come to the same conclusion. The out of balance conduction is far too variable. In my case, I will even have a speed that will be terrible, but later in the drive will be smooth. But let’s say I’m cruising in the smooth zone for a bit and then I speed up a bit and the hop comes back, slowing down to the smooth zone doesn’t fix it, it’s like I’ve upset the distribution of the balance beads in the tires. I’m fairly sure these things are complete bullcrap, I’ve just not been motivated enough to tear all my tires back down…

 

[Skyhawk13205]

I have come to the same conclusion. The out of balance conduction is far too variable. In my case, I will even have a speed that will be terrible, but later in the drive will be smooth. But let’s say I’m cruising in the smooth zone for a bit and then I speed up a bit and the hop comes back, slowing down to the smooth zone doesn’t fix it, it’s like I’ve upset the distribution of the balance beads in the tires. I’m fairly sure these things are complete bullcrap, I’ve just not been motivated enough to tear all my tires back down…

On my truck the wheel vibe is at 55 mph, it will dampen out at 60, then at 65-70 the vibes will get significantly worse. When doing turns the vibes will get better or worse depending if the vibes amplify or cancel each other. I have done a datum test where I hang a reference and spin the tire on the axle to see if the tire is true and the deviation is not more than 1/8-1/4, I don’t know if that is within a spec, but I am not sure. I have not measured how true the tires on the axial plane of rotation. If the tires are not true on the rotation plane, they would also add up to increased vibes. I wonder it the inboard and outboard wear pattern cause imbalance on the axial plane on the steer axle. Broke Overland on YouTube did a tire balance test and used a GoPro to view the tire rotation and saw the tires were not tire on the axial plane. Helicoil Helepad also the saw the same thing and I think it was on a steer tire as well.

 

[GeneralDisorder]

On my truck the wheel vibe is at 55 mph, it will dampen out at 60, then at 65-70 the vibes will get significantly worse. When doing turns the vibes will get better or worse depending if the vibes amplify or cancel each other. I have done a datum test where I hang a reference and spin the tire on the axle to see if the tire is true and the deviation is not more than 1/8-1/4, I don’t know if that is within a spec, but I am not sure. I have not measured how true the tires on the axial plane of rotation. If the tires are not true on the rotation plane, they would also add up to increased vibes. I wonder it the inboard and outboard wear pattern cause imbalance on the axial plane on the steer axle. Broke Overland on YouTube did a tire balance test and used a GoPro to view the tire rotation and saw the tires were not tire on the axial plane. Helicoil Helepad also the saw the same thing and I think it was on a steer tire as well.

Many surplus tires have been on a tire carrier and that WILL warp them in the axial plane. I had a temporary tire and wheel from a spare tire carrier and you could see it wobble axially in the rearview mirror.

 

[Reworked LMTV]

Yep, I'm driving through Canada with intermittent internet service right now. Drove another 615 miles yesterday, the vibration/hop has been tolerable and still varies greatly depending on speed. It is worst around 55 mph/90 kph which is rough since that is the speed limit on a lot of the roads we traveled yesterday and will travel today. If I slow down to ~50 mph or speed up to ~61 mph it smooths out quite a bit.

Any issues with your former military truck crossing through Canada ?

 

[gringeltaube]

................. Broke Overland on YouTube did a tire balance test and used a GoPro to view the tire rotation and saw the tires were not tire on the axial plane. Helicoil Helepad also the saw the same thing and I think it was on a steer tire as well.

I'd say most often the cause of "wobble" is the wheel, not the tire....

I have worked on- and modified dozens of FMTV (steel) wheels . Problem is, from factory their (poor) design allows both halves to shift against each other while bolting them together. Mounting that assembly on a hub and holding a dial indicator to the inner bead, one can find as much as 3mm (radial) runout - not counting the usual, inherent imperfections of the inner rim half (like being oval or egg-shaped) In that case even a new and perfectly straight tire will show an axial runout of 5-6mm, measured at the outer circumference. Way too much to call it good.... (!)

Remedy: take the time to align- and center everything on a lathe, then tighten and add a pair of dowel pins, 180deg across. This ensures exact alignment every time the wheel gets assembled.
My goal is to keep the axial and radial runout of the tire thread below 2mm. Same goes for tires on MRAP/MTVR steel wheels. Normally not a problem....