Wheel Weights vs Liquid Ballast and the Misconception

[bird dogger]

At different times here on OTT and on other tractor forums, there’s a statement commonly made concerning the differences between the two types of added ballast. Like an urban legend, the statement made that seems to be turning into a “rural” legend is that the weight of a solid wheel weight is carried by the axle, whereas the liquid ballast weight is carried by the ground. Implying that wheel weights put unnecessary weight on the axle before it gets to the ground. New tractor owners as well as seasoned tractor owners seem to repeat this misconception.

For the sake of new tractor owners, let’s discuss this issue. And I’ll polish my metaphorical sword and be ready and willing to fall on it if those seasoned believers can change my mind or prove me wrong with my saying, “With possibly few exceptions, the load/weight of a solid wheel weight is carried by the ground…..just as liquid ballast is.” The only weight carried by the axle is the weight of the equipment between the wheel hubs. IE: the tractor’s rear end along with its additional rear mounted equipment that is raised off of the ground. The only time wheel weights are carried by the axle is if that tire becomes lifted clear of the ground. The same also applies to liquid ballast.

It would be an odd exception to have a wheel weight that is directly installed on an axle itself…..and especially between the wheel and the axle housing. The wheel design on some smaller sub compact tractors and garden tractors may require weights to use longer wheel/hub mounting bolts to attach the weights along with the wheel. But even then, the weight is still essentially with the wheel/hub and carried by the ground and not by the axle.

Points to consider:

They’re called wheel weights for a reason: they’re bolted directly to the wheel. The wheels have separate mounting holes for their installation. (Again, with some exceptions on smaller wheels.)

The added weight becomes part of the wheel itself and is then transmitted through the tire to the ground. The increased wheel weight compresses the rubber tire downward until the air pressure increases to stop that action. The wheel is just bolted to the axle/hub which will then lower along with it until the tire’s air pressure is increased to account for the added weight and properly correct the tire’s footprint again.

Unless the weight covers the wheel/hub mounting bolts (as they might on some smaller tractor wheels) you can remove the wheel/tire with the weight still mounted. The added weight doesn’t stay and hang on the axle. This in itself is proof enough that the added weight is carried by the ground.

Granted, some weights can be stacked and mounted in multiples on a wheel. Then the outer weights could extend past the outer edge of the wheel and tire’s footprint. That would put some outward pull/stress on the wheel’s flange and axle hub. But usually, only one weight per wheel is added to our smaller tractors. The weight is located pretty much inside the outer wheel cavity and within the tire’s footprint. The resulting small off-center weight imbalance is handled by the tire, wheel flange, and axle hub. The ground still carries the major portion of the wheel weight, not the axle.

The wheel weight’s “ballast” is mounted concentric to the axle…..not on it. Liquid ballast in the tire lowers the center of gravity just a little bit further than a wheel weight does because it mostly resides inside the lower portion of the tire…..not mounted around the center of the wheel like a wheel weight is. Again, only when the wheel is lifted off the ground are both types of ballast weight carried by the axle. Hopefully that doesn’t happen!

The other statements regarding costs per pound, eventual rust or no rust, ease of tire repair, being able to remove wheel weights when not needed, which type is better for traction, etc., etc. is something each person has to consider and apply to their situation. But the statement made that says a bolted-on wheel weight’s “ballast” is carried by the axle and not by the ground is inaccurate with probably 99.99% of wheel weight applications.

Growing up in a farming community and on a farm with row crop tractors that had extended rear axles for shifting the tires wheel base: I can’t recall ever seeing wheel weights bolted independently on the axles. They were always attached to the wheel itself. But there’s always an exception, and maybe in another type of industry it might be different. But for our small, sub compact, compact, and even slightly larger tractors, I think it would be the rare exception rather than the rule.

Let’s not add any more confusion to a new tractor owner’s ballast choice than there already is. With possibly an exception or two, a bolted-on wheel weight’s ballast is also carried by the ground, just like liquid ballast is. And not by the axle. It just happens to be centered around the axle.

I'll now get the polish out and wait to be convinced otherwise!

 

[NCL4701]

If you live in an area where agriculture is a thing (I know some do not) and you’re really confused on tractor ballasting (types of liquid, amounts of liquid, which tires to fill, wheel weights, front weights, weight on 3 point when using loader, etc.) maybe consider contacting your local Ag Extension agent office and sign up for a tractor ballasting class. For many types of ag functions it’s a real science to ballast properly to maximize efficiency, minimize soil compaction, and minimize wear on equipment. You probably would get some information you’d never use (like do you put liquid ballast in your outside duals?) but you’d also get the basic principles and methods of ballasting.

And I agree with bird dogger. If it’s on/in the wheel it’s part of the wheel and not weight carried by the axle. Furthermore, if your machine is designed to carry weights, so long as you don’t exceed the weight limitations set by the manufacturer you should be fine. The biggest issue to me for my specific tractor is rear wheel weights are limited to 185lb/side per the manual. Liquid ballast in the R4’s is more like 550lb/side. Nothing wrong with steel weights (have them on the Farmall in addition to liquid); I just don’t happen to have them on the Kubota. To each their own and each setup customized to the tasks at hand.

 

[Russell King]

@NCL4701
What is the limit of 185 pounds per wheel?

Is that a published value in the manual? If so does it state why they limit it?

Is that a limit on the commercially available wheel weight (and they don’t stack)?

I can fathom limiting the weight because of the attachment method and limiting stress in the wheel or fasteners or perhaps the tire but 185 pounds is really not very much weight. Just curious on the limiting value.

I won’t make a comment on the original posit for fear of being flamed by other posters (but I agree with @bird dogger )

 

[Elliott in GA]

Two issues/differences between wheel weights and liquid ballast:

1) A wheel weight is carried by the tire. Having a wheel weight is the same as having that much more weight being carried by the tire; liquid ballast does not (or at least at a extremely reduced rate) count towards your weight with relationship to your tires' capacity. Is it important? Probably only if you are using tires that have lower weight capacities (like R1 and R3) in activities that approach their weight limits. Is this a common problem - seemingly, no. Most tire weight capacity issues focus on the front wheels with a FEL.

2) A wheel weight's inertial mass must be counteracted by force every time you start, increase, decrease and stop motion. This additional force is born by the axle, transmission and brakes. Liquid ballast's inertial mass does not need to be overcome with force, as the ballast mostly remains stationary with some turbulence within the tire. Obviously, there is some resistance to motion, but it is very small relatively speaking. All of this is predicated on the slow speeds of tractor movement; you do not have centripetal force issues (often referred to as centrifugal force). Is it important? Probably not - there is more wear and tear with wheel weights, but it is unlikely that it is meaningful.

 

[NCL4701]

@NCL4701
What is the limit of 185 pounds per wheel?

Is that a published value in the manual? If so does it state why they limit it?

Is that a limit on the commercially available wheel weight (and they don’t stack)?

I can fathom limiting the weight because of the attachment method and limiting stress in the wheel or fasteners or perhaps the tire but 185 pounds is really not very much weight. Just curious on the limiting value.

I won’t make a comment on the original posit for fear of being flamed by other posters (but I agree with @bird dogger )

This is the page out of the Operator Manual that addresses iron weights and liquid ballast for the L4701. I don’t know the impetus for the limitation.

Edit: And yes, I’m aware there’s a typo that instructs to add rear wheel weights to some mystery bumper somewhere immediately prior to the illustration showing wheel weights added to the wheel where they’re always added.

Apparently they do stack. 3 each per wheel = 185lb per wheel per the OM.

 

[85Hokie]

At different times here on OTT and on other tractor forums, there’s a statement commonly made concerning the differences between the two types of added ballast. Like an urban legend, the statement made that seems to be turning into a “rural” legend is that the weight of a solid wheel weight is carried by the axle, whereas the liquid ballast weight is carried by the ground. Implying that wheel weights put unnecessary weight on the axle before it gets to the ground. New tractor owners as well as seasoned tractor owners seem to repeat this misconception.

For the sake of new tractor owners, let’s discuss this issue. And I’ll polish my metaphorical sword and be ready and willing to fall on it if those seasoned believers can change my mind or prove me wrong with my saying, “With possibly few exceptions, the load/weight of a solid wheel weight is carried by the ground…..just as liquid ballast is.” The only weight carried by the axle is the weight of the equipment between the wheel hubs. IE: the tractor’s rear end along with its additional rear mounted equipment that is raised off of the ground. The only time wheel weights are carried by the axle is if that tire becomes lifted clear of the ground. The same also applies to liquid ballast.

It would be an odd exception to have a wheel weight that is directly installed on an axle itself…..and especially between the wheel and the axle housing. The wheel design on some smaller sub compact tractors and garden tractors may require weights to use longer wheel/hub mounting bolts to attach the weights along with the wheel. But even then, the weight is still essentially with the wheel/hub and carried by the ground and not by the axle.

Points to consider:

They’re called wheel weights for a reason: they’re bolted directly to the wheel. The wheels have separate mounting holes for their installation. (Again, with some exceptions on smaller wheels.)

The added weight becomes part of the wheel itself and is then transmitted through the tire to the ground. The increased wheel weight compresses the rubber tire downward until the air pressure increases to stop that action. The wheel is just bolted to the axle/hub which will then lower along with it until the tire’s air pressure is increased to account for the added weight and properly correct the tire’s footprint again.

Unless the weight covers the wheel/hub mounting bolts (as they might on some smaller tractor wheels) you can remove the wheel/tire with the weight still mounted. The added weight doesn’t stay and hang on the axle. This in itself is proof enough that the added weight is carried by the ground.

Granted, some weights can be stacked and mounted in multiples on a wheel. Then the outer weights could extend past the outer edge of the wheel and tire’s footprint. That would put some outward pull/stress on the wheel’s flange and axle hub. But usually, only one weight per wheel is added to our smaller tractors. The weight is located pretty much inside the outer wheel cavity and within the tire’s footprint. The resulting small off-center weight imbalance is handled by the tire, wheel flange, and axle hub. The ground still carries the major portion of the wheel weight, not the axle.

The wheel weight’s “ballast” is mounted concentric to the axle…..not on it. Liquid ballast in the tire lowers the center of gravity just a little bit further than a wheel weight does because it mostly resides inside the lower portion of the tire…..not mounted around the center of the wheel like a wheel weight is. Again, only when the wheel is lifted off the ground are both types of ballast weight carried by the axle. Hopefully that doesn’t happen!

The other statements regarding costs per pound, eventual rust or no rust, ease of tire repair, being able to remove wheel weights when not needed, which type is better for traction, etc., etc. is something each person has to consider and apply to their situation. But the statement made that says a bolted-on wheel weight’s “ballast” is carried by the axle and not by the ground is inaccurate with probably 99.99% of wheel weight applications.

Growing up in a farming community and on a farm with row crop tractors that had extended rear axles for shifting the tires wheel base: I can’t recall ever seeing wheel weights bolted independently on the axles. They were always attached to the wheel itself. But there’s always an exception, and maybe in another type of industry it might be different. But for our small, sub compact, compact, and even slightly larger tractors, I think it would be the rare exception rather than the rule.

Let’s not add any more confusion to a new tractor owner’s ballast choice than there already is. With possibly an exception or two, a bolted-on wheel weight’s ballast is also carried by the ground, just like liquid ballast is. And not by the axle. It just happens to be centered around the axle.

I'll now get the polish out and wait to be convinced otherwise!

I'll bite ........... wth........

These weights on the rim......... do they go all the way around the rim, of course they do! THIS weight is thus carried by the rim....... and the weight on top of the rim ....... thus pushing down on the axle......
now if we were to lift a rear tire off the ground with 100 lbs of beet juice or a 100 lbs of weights ........ the pressure on the axle/rim/tire would be the same.

But...... and here is the but........

the fluid INSIDE the tire is not carried by the rim, the force of gravity is pushing down on the tire and only the tire........... now........ going into specifics ........ IF we could have a weight BOLTED to rim ....... and as the rim spun, the weight stayed at the centerline (more or less of the axle) it would not be carried by the axle, it would be carried by the rim and then on the tire to the ground. But that is not the case - there is always, and I mean ALWAYS weight above the axle - thus pushing down on the axle....... now am I splitting hairs........ yes, there is enough hair to split here.

The point is this - the centripetal force that is applied with weights on the rim is completely different than fluid in the tires.... unless we are moving fast .... the fluid stay more or less put, sure is sloshes around but it does not spin with the rim nor does it spin with the tire. It stays inside the tire. (I have been going fast enough on an OLD FORD 8N when the fluid was ........ making the tractor hop!)

Another thing that was brought up - the weight in the tire is different than weight on the rim when going up an incline ..... IF you could load a bicycle tire with fluid and pedal it and then add the weight on the rim and go up an incline ........ you would feel the difference between the two.

your statement :
"Let’s not add any more confusion to a new tractor owner’s ballast choice than there already is. With possibly an exception or two, a bolted-on wheel weight’s ballast is also carried by the ground, just like liquid ballast is. And not by the axle. It just happens to be centered around the axle."

I agree with 100%

Elliott in GA said it better than I did !

 

[TheOldHokie]

I'll bite ........... wth........

These weights on the rim......... do they go all the way around the rim, of course they do! THIS weight is thus carried by the rim....... and the weight on top of the rim ....... thus pushing down on the axle......
now if we were to lift a rear tire off the ground with 100 lbs of beet juice or a 100 lbs of weights ........ the pressure on the axle/rim/tire would be the same.

But...... and here is the but........

the fluid INSIDE the tire is not carried by the rim, the force of gravity is pushing down on the tire and only the tire........... now........ going into specifics ........ IF we could have a weight BOLTED to rim ....... and as the rim spun, the weight stayed at the centerline (more or less of the axle) it would not be carried by the axle, it would be carried by the rim and then on the tire to the ground. But that is not the case - there is always, and I mean ALWAYS weight above the axle - thus pushing down on the axle....... now am I splitting hairs........ yes, there is enough hair to split here.

The point is this - the centripetal force that is applied with weights on the rim is completely different than fluid in the tires.... unless we are moving fast .... the fluid stay more or less put, sure is sloshes around but it does not spin with the rim nor does it spin with the tire. It stays inside the tire. (I have been going fast enough on an OLD FORD 8N when the fluid was ........ making the tractor hop!)

Another thing that was brought up - the weight in the tire is different than weight on the rim when going up an incline ..... IF you could load a bicycle tire with fluid and pedal it and then add the weight on the rim and go up an incline ........ you would feel the difference between the two.

your statement :
"Let’s not add any more confusion to a new tractor owner’s ballast choice than there already is. With possibly an exception or two, a bolted-on wheel weight’s ballast is also carried by the ground, just like liquid ballast is. And not by the axle. It just happens to be centered around the axle."

I agree with 100%

Elliott in GA said it better than I did !

Just because some portion of the weight is above the axle does not mean it is being carried by the axle. Wheel weights are being carried by the wheel center. Exactly as if you remove the wheel from the hub. As Elliot explained its the dynamics of that weight in motion that creates forces acting on the axle and hub.

The L4901 manual page is pretty clear - Kubota is fine with 185 lbs (3 x 62# weights) of iron weight and 580 pounds of liquid ballast per wheel.

The L3901 manual is identical except that the tires are smaller and you max out on volume well before 580# of liquid.

Dan

 

[SDT]

View attachment 79309
This is the page out of the Operator Manual that addresses iron weights and liquid ballast for the L4701. I don’t know the impetus for the limitation.

Edit: And yes, I’m aware there’s a typo that instructs to add rear wheel weights to some mystery bumper somewhere immediately prior to the illustration showing wheel weights added to the wheel where they’re always added.

Apparently they do stack. 3 each per wheel = 185lb per wheel per the OM.

Puzzled by 185 Lb./wheel weight restriction in section 2 and suspect yet another mistake in manual like the obvious one in section 2.1. I have found numerous mistakes in operator's manuals.

I have the maximum recommended number of 3, 106 Lb (IIRC) weights on each wheel of my L6060. So far as I know, the L4701 uses the same rear weights as does the 6060. No, I did not verify.

Yes, Kubota allows more liquid ballast than cast ballast but I expect that the lower cast ballast limitation has more to do with attachment limitations and overall width than total weight.

SDT

 

[jyoutz]

@NCL4701
What is the limit of 185 pounds per wheel?

Is that a published value in the manual? If so does it state why they limit it?

Is that a limit on the commercially available wheel weight (and they don’t stack)?

I can fathom limiting the weight because of the attachment method and limiting stress in the wheel or fasteners or perhaps the tire but 185 pounds is really not very much weight. Just curious on the limiting value.

I won’t make a comment on the original posit for fear of being flamed by other posters (but I agree with @bird dogger )

I think the limit was based on the weight of the available cast weights for sale. Some can be stacked, but the difference between cast weights and liquid ballast is why I went with the liquid.

 

[bird dogger]

I'll add some comments to your statements and try another (maybe a better one) explanation at the end. Click to "expand" for my comments.

You said: "These weights on the rim......... do they go all the way around the rim, of course they do! THIS weight is thus carried by the rim....... and the weight on top of the rim ....... thus pushing down on the axle......now if we were to lift a rear tire off the ground with 100 lbs of beet juice or a 100 lbs of weights ........ the pressure on the axle/rim/tire would be the same."

I say: I think you’re reasoning is flawed. The wheel center and rim are solid metal. The only place where the rim would display its weight is the point of contact with its resting spot. Its weight doesn’t flow through the center hole whether there’s anything in there or not. The weight of a solid object is carried anywhere through its material and spread out over the bottom contact surface.

You said: "But...... and here is the but........the fluid INSIDE the tire is not carried by the rim, the force of gravity is pushing down on the tire and only the tire........... now........ going into specifics ........"

I say: I’m almost sure you don’t even believe what you stated there. The force of gravity is not pushing down on the tire and only the tire. Gravity acts upon everything on earth whether its inside a tire or not. It’s the reason the fluid is put in the tire…..to add the weight gravity gives it for more traction.

You said: "IF we could have a weight BOLTED to rim ....... and as the rim spun, the weight stayed at the centerline (more or less of the axle) it would not be carried by the axle, it would be carried by the rim and then on the tire to the ground. But that is not the case - there is always, and I mean ALWAYS weight above the axle - thus pushing down on the axle....... now am I splitting hairs........ yes, there is enough hair to split here."

I say: I can’t follow your logic on this because of the physical properties of the solid wheel. In one respect, you are mostly technically correct. The weight is bolted to the solid rim and centered around the axle, and the weight would be carried by the rim and then on to the tire to the ground. But the last part of your statements seems to contradict what you said in the first part. Yes there’s always weight above the axle, but the wheels weight is transferred to the point where it contacts the ground.

You said: "The point is this - the centripetal force that is applied with weights on the rim is completely different than fluid in the tires.... unless we are moving fast .... the fluid stay more or less put, sure is sloshes around but it does not spin with the rim nor does it spin with the tire. It stays inside the tire. (I have been going fast enough on an OLD FORD 8N when the fluid was ........ making the tractor hop!)

Another thing that was brought up - the weight in the tire is different than weight on the rim when going up an incline ..... IF you could load a bicycle tire with fluid and pedal it and then add the weight on the rim and go up an incline ........ you would feel the difference between the two.

your statement : "Let’s not add any more confusion to a new tractor owner’s ballast choice than there already is. With possibly an exception or two, a bolted-on wheel weight’s ballast is also carried by the ground, just like liquid ballast is. And not by the axle. It just happens to be centered around the axle."

I agree with 100% Elliott in GA said it better than I did !"

I say: I completely agree(100%, too) with you and never implied otherwise in the original post. I only stated that an axle does not carry the weight of a wheel weight as normally used when bolted to the wheel. It is carried by the ground through the tire. That is the misconception we are talking about. I even stated that all the other factors of the two styles had to be considered by the user. I listed only a few and added etc., etc., to take care of the others. Elliot explained one of the others very nicely.

Maybe this will better explain my points:

A bare wheel is sitting on the concrete pad. All weight of the wheel rests on the two edges of the rim touching the concrete. The center hole is still there, solid as can be, and the weight above it is transferred through the metal around it downward.

Bolt a wheel weight onto it. All the additional weight is transferred in the same way to the same two points on the concrete.

Add the rubber tire. Now all the weight of the wheel, wheel weight and tire are transmitted to the ground being spread out over the tires foot print. The empty hole in the wheel and wheel weight has no effect on the weight transfer.

Let’s add another wheel weight to the inside of that assembly. We get the exact same results, but with more weight passing through the tire causing it to squat more. Even if that inside wheel weight had a solid center, the result would be the same.

Let’s put two of those wheels in parallel, spread them apart, but call the inside wheel weights a tractor. As far as the two wheels are concerned, the tractor is just additional weight causing the tires to squat even more. But until you start the tractor and move it, its just another expensive wheel weight added on. The tractor’s hub is now pushing down on the wheel with an amount equal to the tractor’s shared weight between the two wheels. But, the weight of the tire, wheel, and the outside wheel weight is still only transferred as before. IE: From the wheel weight to the wheel center, to the rim, to the tire, and onto and carried by the ground. Stacking on more wheel weights would also have the same results. The axles are carrying the tractor’s weight, not the wheels weight……..until a tire is clear of the ground.

When you look at the basics, it’s easier to see what’s happening. The same applies to power lost going up a slope. (Which was not part of the original post). But here's an easy example to illustrate:

From high school, I always remember the value of 550 lbs when related to HP. Basically, one HP is the energy required to lift 550 lbs. up one foot in elevation per second.

Using some easy round figures just for an example: A mower weighs 550 lbs. A tractor/loader weighs 2750 lbs. Ballast used weighs 550 lbs. for a combined weight of 3850 lbs. Traveling uphill at a rate of 1ft. of elevation per second would use up 7 HP before you even start to begin mowing. Substitute a box blade pulling material uphill for the mower and the results can be worse.

But again, my original post was only to address that single issue of wheel weights and where the weight is transferred. Nothing else.

But since you mentioned old Ford 8Ns: I know exactly what you mean. I'd have to sit down with paper and pencil to remember all the different tractors I both grew up with and operated while working as a kid for the different farmers in the area. Betting a lot of the OTTers would have to google the names to see what they were. Especially the Cockshutts, Co-ops, Massy's, etc.

I also hoed sugar beets (two sessions: thinning and weeding) from sunup to sundown for 11 yrs., starting from the age of 9. (9 half mile rows to the acre). Hard work but good money. We boys were very religious! We prayed for rain every night so we might have a day off during the week! I still walk fast as a result of all those years with a hoe in the fields.