Tire PSI Question...

[Podunkadunk]

I have this posted over in the Kubota Owner Operator section, but not a lot of action over there. 110 people read the post, 3 replied...still no answer. I figured with all the operators with hundreds of hours and thousands of posts, maybe I can get an answer from someone.

I have a L3130, HST, 4x4. I was reading my operator's manual and now I'm confused. Please chime in with your interpretation/advice.

The manual has a warning which reads "Always maintain the correct tire pressure. Do not inflate tires above the recommended pressure shown in the operator's manual."

So, the manual states the inflation pressure for my unit is:

R-4's;
Front tires: 10-16.5 NHS, 6PlyRating...20psi
Rear tires: 420/70-24, 6PlyRating...20psi

You would think it would be pretty simple, but then there's this note:
"Maintain the maximum pressure in front tires, if using a front loader or when equipped with a full load of front weights." For my particular unit, that weight happens to be 386 lbs.

That statement is what is confusing me. Which "maximum" are they talking about? The manual says 20psi, but doesn't list a max or min, just 20psi.

The tire itself has a warning on the side of it stating not to exceed 45psi max cold.

I understand the meanings of these notes and warnings, but can't figure out which pressure they are talking about.

I just added approx. 320lbs of weight to the front end (total of the grill/brush guard weight and 2 (55lbers) and 2 (80lbers)).

I know this seems like a lot of info for a "simple" tire psi question, but I wanted everyone who reads it to have the same info I have and be well informed before giving me your thoughts.

What pressure should I maintain in the front tires?



-Podunk

 

[Dougd]

Probably can't go wrong with 20 PSI. The max PSI rating on the sidewall is there on the advice of the legal dept. of the tire maker and has little to do with proper inflation. The weight rating on the sidewall is another thing altogether...

 

[HomeBrew2]

I have this posted over in the Kubota Owner Operator section, ... Podunk

Uh, oh, beware the double-posting police

 

[dqdave1]

I would go with 20 PSI. I wonder if you put 20 PSI in tire then add your weights; does the pressure change?

 

[tractortad]

Podunkadunk -

I'd go with the 20 lbs in your fronts and then evaluate how the tires ride/work. If they don't bulge out significantly, then they're probably good.

I run about 18-20 lbs on my JD 5510 front (loaded) tires - with a loader attached. When they get any lower than about 12 lbs, it gets obvious because they bulge easily when the tractor goes downhill. Granted these are bigger tires than yours (12.4 -24), but they probably work about the same. If you put too much air in the front, it will give you a "bouncy" front end -even with the weights.

 

[Podunkadunk]

Uh, oh, beware the double-posting police

I couldn't get any love over in the Kubota owner/operator section. Hardly anyone would answer or even speculate. Not much action over there I guess.

Release the hounds!

I'll tell ya, I never figured an operator manual to print text in riddles like that. I reckon I'll call Kubota and ask them wtf...over.

In the meantime, I have them at 20psi. I figure I can't go wrong with what they DO have published.

 

[john_bud]

Podunkadunk,

I have a 3410 with loader and the same titan R4's front 'stones in the rear. Going into the 7th year with no issues (knock wood). Have kept both at 20 psi the whole time.

 

[JoeL4330]

As long as the tire is still "pneumatic"--that is, sidewalls flex and rim isn't on the ground, then the number of sq. in. of tire patch on the ground times the psi is the weight on that tire.

Or, conversely, (don't do this) air down the tire until the rims touch, then add some air and check the psi. That's the minimum needed to support the load. If it's less than 20psi, air up to 20 psi in order to make sure the tire won't come off the rim (i.e., break the bead) when turning. If, on the other hand, in order to get the rim off the ground you would need more psi than the max inflation pressure listed on the sidewall, then get bigger tires, or a tire load rating that can support a higher max inflation pressure, or a smaller load. This is all for static load and if you were zipping along uneven ground, you would have to account for dynamic loads (jounce and rebound) which, in fact, flex the sidewalls and the friction of the cords raises the temp and/or the pressure (sometimes dramatically which is one reason a tire "blows out").

So, I suspect what Kubota is tellin' you is that they size the tires and spec the load rating of those tires so that with 20 psi they can carry the max rated load for their loader fully laden, account for dynamic forces, keep the bead intact, and provide some cushion (in the sense of shock absorption) for that boulevard ride.

This is the same logic that your auto manufacturer uses to tell you to put, say, 28 psi in the rear ...unless you are fully loaded (with passengers and golf clubs) and/or drive at sustained high speed, in which case increase it, say, to 32 psi, but stay below the max inflation of, say, 36 psi...

 

[MikePA]

Closed. Dupe of this thread.