Tire pressure question

[Oldbinder]

On my rear tires (14.9- 24 R4) only has about 50% of the thread in contact with the ground. The instructions on the tires only say to not exceed 38 psi and the pressure is presently at 20 psi. The tires have rimgaurd in them and only 120 hrs on them. Even with a 6 ft Woods box scraper on the 3 point hitch the tire contact stays the same. Just having 50% of the tire in contact with the ground doesn’t seem right. Can I or do I need to decrease the pressure in order to get full contact?

 

[JethroB]

I’m running about 12 in the rears now mostly for ride comfort. It did increase the contact patch some but those R4’s have some pretty stiff sidewalls. Kubota manual recommends 20, Kubota dealer said go for it until you have slippage. Note running low pressure in the fronts you risk running the tire off the rim. BTDT. (No FEL)

 

[Chewwy]

You should follow the instructions in you operators manual regarding tire pressure. The manual for my Kubota specifies 20 psi for those size tires.

 

[deserteagle71]

I don't pay much attention to what an owner's manual says about tire air pressure. Whoever wrote the manual has no idea what you will be mounting on the tractor, nor how you will be using it. Pressure is set so there is a slight bulge in the sidewall of the tire - front or rear - for whatever work I'll be doing. The tread surface should have contact with the ground across its entire width, not just the center of the tire. If the tractor will be handling a lot of weight - like unloading 2000 lb pallets using the front forks- then I will air up the front tires accordingly. Then reducing the air pressure once the job is done.

 

[Oldbinder]

You should follow the instructions in you operators manual regarding tire pressure. The manual for my Kubota specifies 20 psi for those size tires.

My manual says the same thing.

 

[Oldbinder]

I don't pay much attention to what an owner's manual says about tire air pressure. Whoever wrote the manual has no idea what you will be mounting on the tractor, nor how you will be using it. Pressure is set so there is a slight bulge in the sidewall of the tire - front or rear - for whatever work I'll be doing. The tread surface should have contact with the ground across its entire width, not just the center of the tire. If the tractor will be handling a lot of weight - like unloading 2000 lb pallets using the front forks- then I will air up the front tires accordingly. Then reducing the air pressure once the job is done.

The front tires are ok, no need for me to adjust the pressure. I typically don’t have much weight on the 3 point hitch because most of the work is with the FEL. I need the full traction of the rears in the winter because I have to plow. I will try a lower pressure on the rear tires and see how things work out.

 

[LouNY]

I don't have R4's but my R1's are usually around 15 PSI .

 

[masseyrider]

I don't pay much attention to what an owner's manual says about tire air pressure. Whoever wrote the manual has no idea what you will be mounting on the tractor, nor how you will be using it. Pressure is set so there is a slight bulge in the sidewall of the tire - front or rear - for whatever work I'll be doing. The tread surface should have contact with the ground across its entire width, not just the center of the tire. If the tractor will be handling a lot of weight - like unloading 2000 lb pallets using the front forks- then I will air up the front tires accordingly. Then reducing the air pressure once the job is done.

I also do the eyeball test.
I'll add air when the sidewall starts to bulge depending on load.
I've never put a gage to the rears.
Close to 50 years and counting, no problems.
Drive your tractor over soft ground where it will leave a good clean impression.
I know my owner manuals show what it should look like.

 

[oosik]

I have R-1 tires on my M6040. 775 pounds of RimGuard in each rear tire. 1000+ pound blade on the 3-point. 820 pound grapple on the FEL.

I run 40 psi in the front tires. 16 pounds in the rear tires.

Drive across a sandy patch in my driveway. Jump off the tractor and check. It's OK - I have a full chevron mark - all the way across - for the rear tires.

 

[Too many Kubotas]

View attachment 962355On my rear tires (14.9- 24 R4) only has about 50% of the thread in contact with the ground. The instructions on the tires only say to not exceed 38 psi and the pressure is presently at 20 psi.

Wow. After 1,400 hours my M6040's rear tires look like new compared to yours.

Of course, 85% of the time there's something on the 3-point, but looking at the picture I can't help but wonder if you're spinning the rears somewhat frequently.

I don't use 4WD unless it's needed, which is when getting full scoops of dirt or rock with the loader, or when plowing if the snow is deep. I also don't drive it on pavement, which I'm sure helps.

 

[deserteagle71]

looking at the picture I can't help but wonder if you're spinning the rears somewhat frequently.

If they are overinflated for the weight they are carrying then no doubt there is a lot more slippage than if the tires were aired down. The tracks the tires leave should show the entire width of the tire in good contact with the ground.

 

[dieselscout80]

Bias ply R4 tires are really stiff.

Mine with zero tire pressure after I drained the fluid out of the rear tires stiff supported the tractor. You see the tube I used siphon the fluid out.

The sidewalls of my rear radial tires are so much softer than the bias tires were.

When I let the air out to add fluid it was just like a flat tire on an automobile.

17.5LR24 Tires w/ R1 Tread

I had Titan 17.5L24 R4 tires on my New Holland TC45DA and they provided terrible traction, so I set out to find a R1 type tire. I only found one 17.5LR24 / 460/70LR24 tire with a R1 tread pattern the BKT RT 747. https://www.bkt-tires.com/ww/us/rt-747-agro-industrial The RT 747 is a radial and...

www.tractorbynet.com

 

[Oldbinder]

If they are overinflated for the weight they are carrying then no doubt there is a lot more slippage than if the tires were aired down. The tracks the tires leave should show the entire width of the tire in good contact with the ground.

I just did a lot of dirt road work due to recent very heavy rains. I moved 20 yards of 3/4” road mix which required 40 bucket loads of laying down the material and grading the road, total time running of 19 hrs. So I ran the tractor a lot on loose gravel which might account for the slippage. Definitely going to lower the pressure in the tires.
Doing the road work with a 4 in 1 bucket and a box scraper worked very good. Going forward with bucket opened 3-4” and spreading with the box scraper was the way I was doing it.

 

[Too many Kubotas]

I moved 20 yards of 3/4” road mix which required 40 bucket loads of laying down the material and grading the road, total time running of 19 hrs. So I ran the tractor a lot on loose gravel which might account for the slippage. Definitely going to lower the pressure in the tires.

I'm close to finishing up some driveway fixes, having used dirt, 4-, and 1" road base. 13 yards of the 4- and 16 of the base.

I "cheated" and used the 10' dump trailer to move it all to where it was needed (love being able to dump to the sides), then used the L3800 with a rear blade and the M6040 with a box blade to spread it all, in layers.

Never had any issues with slipping tires with the 6040, but a couple of times I felt the rears on the much lighter (and R4 equipped) L3800 slip. Backed up a couple of inches and engaged 4WD. I really don't like spinning the tires.

Anyway, I'd think there must have been a lot of tire spinning going on to make tires look like that in 19 hours, regardless of how overinflated they were. Unless they were bad before starting that project.

 

[Oldbinder]

Too many,

I'm close to finishing up some driveway fixes, having used dirt, 4-, and 1" road base. 13 yards of the 4- and 16 of the base.

I "cheated" and used the 10' dump trailer to move it all to where it was needed (love being able to dump to the sides), then used the L3800 with a rear blade and the M6040 with a box blade to spread it all, in layers.

Never had any issues with slipping tires with the 6040, but a couple of times I felt the rears on the much lighter (and R4 equipped) L3800 slip. Backed up a couple of inches and engaged 4WD. I really don't like spinning the tires.

Anyway, I'd think there must have been a lot of tire spinning going on to make tires look like that in 19 hours, regardless of how overinflated they were. Unless they were bad before starting that project.View attachment 975265View attachment 975266View attachment 975267View attachment 975268View attachment 975269View attachment 975270

The wear on your rears look right. What is the tire pressures?

 

[Too many Kubotas]

Too many,


The wear on your rears look right. What is the tire pressures?

I hate to admit it, but I don't recall ever checking it. I'll be happy to find out for you later today or tomorrow.

That one is a '13 with only some 560 some hours on it so I'd expect the tires to still look good.

Can't say the same about the fronts, though. They're about half gone already, which is much like how the older (about the same size) little Kubota we had. It consumed fronts but not rears.

My friend who bought it has had the same experience and recently bought new fronts (R1) for it.

Fixed the last part of the driveway today, by the way. That low spot over a culvert always got the better of me when plowing. That the driveway's slope increases as it gets closer to the road is bad enough for my operator talents.

 

[oosik]

Too Many Kubotas - looks to me, you did a fine job on the driveway upgrade.

 

[Oldbinder]

I changed the rear tires pressures this morning. One was 22.3 psi the other was 24.2 psi and changed them both 12.0 psi at first. 12 psi only changed the tire contact from 50% to 75%. So I dropped the pressure to 10.0 psi and this gave me full contact. Going from the original pressure to 10% didn’t noticeably change the sidewall profile. I ran the tractor about a mile at each adjustment the get a dirt profile on the tires. Also noticed that the tires were spinning because tire inflation stems were always in different locations relative to each other.

 

[Too many Kubotas]

Also noticed that the tires were spinning because tire inflation stems were always in different locations relative to each other.

That doesn't necessarily indicate that they're spinning.

It doesn't take much of a turn to make the left and right sides to travel different distances.

Another reason, although unlikely, could be that even at the same pressure both tires don't have the same static loaded radius (the distance from the center of the axle to the ground), making them turn at slightly different speeds.

 

[zzvyb6]

Rim guard changes all notions and specs on tire pressure because impacts don't compress incompressable fluids. The Rimguard website has recommendations for the new pressure recommendations.

Couple of other things to contemplate:
The tires may be too large for your tractor weight(s) to make full use of tread contact for traction.
Your tires may be over filled for their usage weight.
The missing serial & date stamp on the mold block strongly suggests that your tires are cheap knock-offs made from a copy of an existing real-deal tire. Mine (same size Titans) have a size and date code clearly visible on them in their mold plate block, even after 500+ hours. The brand shown on yours may be familiar, but there's probably more to the story. That may be why yours have the wear and weather checking appearance that they show.