Turf Tire Pressure

[N750A]

I have a new Kubota MX5400 that is used strictly for mowing an airstrip with a Woods RD990X finishing mower. There is no loader on the front and no fluid in the tires as I wanted to keep it as light as possible since it is only used for mowing on dry, level turf. It has turf tires, 305?R343's on the front and 610R470's on the back. The big Woods mower will mow just about as fast as I can safely go, so I usually mow in high 2nd gear. There are, however, slight bumps in the strip - it's not billiard-table smooth! The first time I mowed, I thought I had made a huge mistake getting the new tractor - the tractor rode very harsh and rough. However, I did think to check the tire pressures and they had been inflated to 20 psi on the front and 30 on the rear. This is much higher than what the manual calls for with turf tires of this size!
I bled the tires down to the correct pressures (per the manual) - 10 psi front and 20 psi rear, and the ride was markedly better. I still feel it is a little harsh, but maybe that's the nature of this tractor with the heavy 4WD axles, etc?
Would there be any ride benefit to lowering the tire pressures further? If so, how much or how low can one one safely go without damaging the tire or the turf?

 

[AWSubie]

The answer lies in gradual reduction of air pressure and a test drive to see how it feels.

Since u have no loader on front I’m thinking you could easily go down to 8 psi on the front. For the back try it at 14 psi with the mower both lowered and raised.

My concern with the back and too low pressure is rolling the tire off the rim on a fast turn when the mower is raised.

 

[loggin]

I'd be careful with the front tires. Ride quality has more to do with the rear than the front tires. 10 psi is already quite low and you don't want to roll the tire off the rim in a corner. The rear has less force to contend with in a corner but I would not go less than 16 psi on the rears. Especially since you are traveling at higher speeds.

Just my 2 cents.

 

[oosik]

I have my front tires - R-1's - at max pressure because of the grapple on the FEL. The rear tires - R-1's - I run at 16 psi. The ride is OK being it's a tractor.

 

[Midwesterner]

I'd be careful with the front tires. Ride quality has more to do with the rear than the front tires. 10 psi is already quite low and you don't want to roll the tire off the rim in a corner. The rear has less force to contend with in a corner but I would not go less than 16 psi on the rears. Especially since you are traveling at higher speeds.

Just my 2 cents.

This, but I wouldn't go below 10 in the rears. I run between 5-8psi in mine, but they are each rated for more than the tractor weighs. A radial tire has to be aired down to a level that lets it flex and bulge out on the sides, otherwise one of the radial advantages is wasted. Keep in mind that the tractor will also ride smoother with more weight on the 3-point. I also agree with what has been said about the fronts, too low and they will unseat. I, personally, would run rated pressure in the fronts, and low enough in the rears so that they squat and ride smoother

 

[N750A]

I think I'll leave the front at 10 (per the manual) for now and perhaps drop the rear to 18 and see if there is a noticeable difference from 20. If not, I'll try 16 but likely will not go lower than that based on the comments. Thanks to everyone for their input!

 

[Texasmark]

The answer lies in gradual reduction of air pressure and a test drive to see how it feels.

Since u have no loader on front I’m thinking you could easily go down to 8 psi on the front. For the back try it at 14 psi with the mower both lowered and raised.

My concern with the back and too low pressure is rolling the tire off the rim on a fast turn when the mower is raised.

I'd say that shouldn't be a problem based on the published tire specs. Owner could check the wheel for the flat section just inside the rim mounting flange. If it has one the purpose of it is to prevent what you said.....you'll find that flange on all automotive and light truck wheels if you want to know what it looks like so you can compare to your wheels.

I had the same reducing air pressure problems with 16.5 diameter wheels which are not made for tire containment in case of deflation and don't have the flat area. I have to be real careful running low pressure for that softer ride you mention. The other problem is that my turfs (aftermarket installation by me) have an extremely rigid sidewall even with only 4 plies such that you can almost let all the air out of the tire and it will support the rear of the tractor...without an implement mounted.

What I can't understand is that rears on my smallest tractor are rated for 2500#+, 6 ply no less OEM installation each at rated pressure on the rear of a machine that only weighs 1800# and it seems to be industry wide.

 

[Wyobuckaroo]

My brother in law had a tire shop before he got his custom plant, harvest business...

He said, read the manual, get all the advise you can, then dismiss all that information and go with the pressure listed on the side wall of the tire...

This has worked well for me...
My 5 cents of opinion and experience...

 

[Midniteoyl]

My brother in law had a tire shop before he got his custom plant, harvest business...

He said, read the manual, get all the advise you can, then dismiss all that information and go with the pressure listed on the side wall of the tire...

This has worked well for me...
My 5 cents of opinion and experience...

Eh. Go by what the tire manufacturer recommends. Tire pressure listed in the manual (or door sticker in cars/trucks) are usually for max loaded weight of that vehicle, or some other criteria like rolling resistance. Whats on the side of the tire is the max that tire company says it can hold while still meeting whatever specs its rated for. Tire manufacturers post Load Inflation Charts just for this reason, here's Toyotires' pdf explaining:

https://www.toyotires.com/media/3729/application_of_load_inflation_tables_20200723.pdf

As for tractors, they too have Load Inflation Tables and while I can't find one with a range for my Goodyear Titan R14Ts, they list what the load is rated at (30psi and 4080lbs) and that is different than what the manual recommends (44psi) and what is on the side of the tire itself (41psi). Since that load rating is for each tire and just one @ 30psi can hold the entire weight of the tractor as it sits, I can lower that pressure if needed/wanted down pretty safely. When you don this, however, you do have to watch for bead rolling as said, *but* you also have to watch for the tire slipping on the rim as well. In fact, with my rim and tire combo, if I deflate completely, I can spin the tire on the rim by hand.. So far, I keep my tires @ 30psi and are filled and the ride is pretty smooth. Was real rough unfilled and at the 44psi it was delivered with, I'll tell you that

 

[SARG]

I have a new Kubota MX5400 that is used strictly for mowing an airstrip with a Woods RD990X finishing mower. There is no loader on the front and no fluid in the tires as I wanted to keep it as light as possible since it is only used for mowing on dry, level turf. It has turf tires, 305?R343's on the front and 610R470's on the back. The big Woods mower will mow just about as fast as I can safely go, so I usually mow in high 2nd gear. There are, however, slight bumps in the strip - it's not billiard-table smooth! The first time I mowed, I thought I had made a huge mistake getting the new tractor - the tractor rode very harsh and rough. However, I did think to check the tire pressures and they had been inflated to 20 psi on the front and 30 on the rear. This is much higher than what the manual calls for with turf tires of this size!
I bled the tires down to the correct pressures (per the manual) - 10 psi front and 20 psi rear, and the ride was markedly better. I still feel it is a little harsh, but maybe that's the nature of this tractor with the heavy 4WD axles, etc?
Would there be any ride benefit to lowering the tire pressures further? If so, how much or how low can one one safely go without damaging the tire or the turf?

Strange .... I have six tractors and none have the rear tire pressure higher than the front.