Bounce bounce?

paulfarber said:

If you put these back on your truck you will have scuffing issues as the diameter of these tires are significantly less than the others....

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Maybe not.

My Stalwart, a 5 tonne w/1400 x 20's, is diameter critical because of the direct driveline (per side, it does had a locking diff between sides). The EMER (a.k.a TM) spec., if I remember correctly, allows for 2” front to back and 1”side to side, at 30psi, with largest tyres on the back... Interestingly, the hull data plate allows for different pressures F/R.

A math study is something like this – If you call 1400 x 20’s a 48” tire the circumference is Pi*2*radius or Pi*dia = 150.72”. Buff off 1/4” dia and they are 47.75” x Pi = 149.935. That's .785 smaller around. 1% of 150.72 = 1.5” so the difference is about 1/2 of 1%. Not much, and much less the Stalwart’s spec. But the tires shown earlier are different. Only part of the tire got buffed away as they weren’t round to begin with. If, say, half of the 1/4" got lost seems like difference would be more like 1/4 of 1%.

A quick trip out with a tape measure shows the one pic above on right* (99% then buffed) was 154”, the middle one was 153 7/8” and the one on the left, the worst, was about 153”. That’s about 3/4 of 1%. Not much.

Also, for clarity, I had left out earlier that the worst tire was my spare. It got drafted because the 99% shown here was on the left front. That got pulled because it had been a real steering wheel shaker.

Also, increasing the pressure will increase the circumference. Does anyone know the TM Spec. for diameter variation? As I stated before, adding max air made irregular tires worse. Please point out any math errors. I’m sure it will go down the road just fine and don’t plan to fiddle with pressures.

Also, I forgot to mention earlier, the 99% came to me with more and it has a 2002 date code.



p.s. In my case towing a 28K trailer, with maybe 4K(?) tongue weight, made little if any change to the bounce.

p.p.s I thought these retailed about 8-$900 ea (not what I paid). Anyone know for sure?

p.p.p.s 28719 members and Paul still has the best avatar.

jimk said:

p.p.p.s 28719 members and Paul still has the best avatar.

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I respectfully disagree.

You could try some dynamic balancing. BB's work good, or there are products designed to do it. I believe the ratio is 1oz of balancer material to every 13lbs of tire.

doghead said:

I respectfully disagree.

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Sorry, your's is better.

You could try some dynamic balancing...

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Never tried it. I'm kind of a lead guy and I seem to be taking 'em apart every few months so that might be messy. I would like to make a stand with a 5 ton hub, lightly oiled, no seals, then let gravity do it. Worked good on motorcycles....I think balance is worth checking. They may spin slower but the radius is large so substantial force can hide there, and the CIS wheel got a weight. I'll update later if they take a lot.

jimk said:

Maybe not.

My Stalwart.....

p.p.p.s 28719 members and Paul still has the best avatar.

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Your driveline does not run dual tires and connected dual axles and is specifically designed to accommodate the specs you listed. The OP mentioned a 5 ton. I was assuming a 818 or or some other tri axle dual wheel setup.

I cannot think or a more apples and oranges comparison in the universe. The 1/4 inch max diameter variance is pretty much common knowledge, and even in a few TMs.

Jennifer Anniston is a hottie at 40+. Now if she could only make a decent movie.

paulfarber said:

... The OP mentioned a 5 ton. I was assuming a 818 or or some other tri axle dual wheel setup.

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You assumed wrong.

Marines42 said:

I have a bobbed 5 ton on 14.00 R20 tires.... I would mainly like to know what causes it.

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Apples-Well, the Stalwart does not scuff it's tires, it has what is known as 'windup', a.k.a. keep your foot down when you turn hard on pavement.

I should also point out that the Stalwart's 2inch/ 1 inch spec. is for circumference, not diameter.

paulfarber said:

If you put these back on your truck you will have scuffing issues as the diameter of these tires are significantly less than the others.
For a 4 tire vehicle its not a big deal...

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The buffing procedure is a useful way to make useless bouncy tires usable for minimal cost, that is something the OP may be interested in.

If someone were to buff, say, 1/4" all the way around (I lost just the high spots) they would still be OK by your claim.

paulfarber said:

...The 1/4 inch max diameter variance is pretty much common knowledge, and even in a few TMs.

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Please provide the TM and page.

paulfarber said:

... Now if she could only make a decent movie.

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Elvis can't either, he's dead.

paulfarber said:

These tires don't need balanced as they don't rotate fast enough to need it. Plus you would have to stick on a few lbs of lead to even make a difference.

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Update- Well, buffing got rid of 80% of my problem. Balancing cleaned up the rest. Method- lightly oiled bearings (5weight), no seals, axles, shoes, 2 lug nuts... then let the wheel rotate and come to rest from each direction. Accurate to 4oz (2oz if you like to fuss). Two of the buffed tires needed 3lbs each (six 8oz weights). The third would have needed 5 lbs. It did not get it and will be used only as a spare (tread 40%?). The 'like new' tires each used about 1-1/2lbs each . The drum alone needed 15oz. NAPA online listed 10, 12, and 14oz weights (10-20ct) but were not available locally. A local truck tire shop (Valley Tire) sold me a hand full of lead for $10 each visit (times 3).

If you have a problem balancing can be useful.

ps
first photo- two 6oz and a 3oz bracket.
second photo- buffed tire, three 8oz on each side.

I was experiencing severe bounce in my deuce after putting on 395s. It seemed to really get bad when I reached 50MPH.

Experimenting with tire pressure got me to 35 PSI and that has been working well for a couple of years. It is ~not too low, these are such heavy tires and designed for a much heavier load that what I can stack on the deuce.

My first clue that the tire pressure was too high was that I was only getting tire wear in the center of the tire. Now I get fairly even wear and a good ride.

I have a 923a2 5 ton. The tires are new all around. The truck is pretty bouncy almost seesaw like. The tires say 60 psi. What pressure should I run to make the ride more balanced ?

Thanks JIMK for the great input! Makes me want to do the same.

Beaming, not unusual, but can be hard to fix. Has to do with the harmonics and natural frequency of the frame rails. To determine if this is the issue, have a rider watch the bed in relation to the cab while the bounce is going on. Bet you see an excessive movement difference. Then we have to address how to alter the natural frequency or just add 500 to 1000# at the front of the bed.

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