Tire Ballast Chart Accuracy?

[avc8130]

I set out to ballast the rear tires on my Kubota L45. The rear tires are 15-19.5. According to most ballasting charts I found, they should hold 29 gallons. I started pumping and put 30 gallons in each figuring I'd drain out the extra gallon once I pulled the hose to know I was at the valve stem at 12 o'clock.

Well guess what? I removed the hose and got nothing. I rotated the tire slowly until I saw ballast coming out, the tires are filled to ~10 o'clock.

Should I keep adding ballast until they are filled to 12 or is there a reason the charts list 29 gallons?

Thanks!

ac

PS: I used -20F WWF for ballast.

 

[ovrszd]

I filled my M9540 tires with WWF. They aren't filled to 12 oclock. I just quit because that's how much fluid I had. If you want maximum weight, fill to 12 oclock.

The variation from the charts could easily be explained by differences in tire brands. Some brands run "large". Some run "small". No worries either way.

 

[George2615]

75-80% full is what most people put in. That fills I to the recommended amount which the charts are based on and puts the fill mark at about the 10 O'clock position. That's where mine are filled to but as Richard mentioned you can try to fill it all the way for maximum fill weight.

 

[murphy1244]

You need some air as liquid is not compressible.

 

[Sprinklerman]

how much would the air weigh?

 

[murphy1244]

how much would the air weigh?

What kind of air? California air? East coast air? Ocean air? all have different weights.

 

[Sprinklerman]

Told a friends girlfriend when she got new tires to tell the shop to put " winter " air in the tires since it was getting cold . She did , when I saw her the next time she read me the riot act . The guys thought it was funny , the girls , not so funny .

 

[MMagis]

Most charts are for 75% filled. Given the variation between mfgs, that sounds about right. Think about that one extra gallon inside the tire, it doesn’t take up much space.

 

[Texasmark]

how much would the air weigh?

14.7 psi at sea level

 

[MHarryE]

The Tire and Rim Association sets the tolerances for tires including all dimensions and ballast charts. The standard hasn't changed for ages but tire manufacturing has improved. Tire makers can hold much closer size tolerances and tend toward the middle of the range. The fluid capacity at 75% fill was set by Tire and Rim Association with a tire at the smallest size. That's so people filling by volume are not at risk of overfilling. It's safe to fill to 12 o'clock vs. specified volume although the extra air volume you have provides a little more safety margin against impact damage. The Tire & Rim Association says that the risk is small until you start getting above the 75% level, and 75% fill is the 12 o'clock position. Our plants filled by volume. I've made hundreds of fill checks of machines on the finished goods lot over the years and 10 o'clock is typical of where we are actually filling. It's easy to audit the fill on days when air moisture is just right that it will condense on the tire in the area the tire is filled. Can check over every machine on the lot in a few minutes vs having someone drive while you hold the valve core in, and you don't get sprayed.

 

[oosik]

My owners manual recommends 75% fill to allow for the air to compress. Fluid does not compress in a tire.

 

[Gary Fowler]

My owners manual recommends 75% fill to allow for the air to compress. Fluid does not compress in a tire.

75% fill is generally explained (look at fill diagrams) to be just as the liquid covers the valve stem when the stem is a top dead center. You still have lots of air above that point. I like to have the liquid covering the top of the rim so no free oxygen is exposed to the rim itself which lessens any possibility of corrosion.

Fill your tire with liquid till you get liquid coming from the stem along with some air gurgles. Don't rely completely on the fill quantities from charts other than for estimates in weight added.