Senior MTF Member
Join Date: Apr 2015
Location: East Central Wisconsin
Wheel Ballast Vs. Soil Compaction
Recently there have been a few threads where ballasting was discussed. In several instances liquid ballast and wheel weights were brought up and members had dismissed this weight inferior or not acceptable. The main reasoning is that liquid ballast is basically permanent and that wheel weights are hard to remove. Apparently, ballast is only useful as counterweight for heavy front or rear attachments. Some people here are recommending suitcase weights and chains as the only things needed for plowing or blowing snow, and that summer mowing should be done with no added machine weight because of soil compaction and ruts.
While I understand that certain places may have very loose, soft soil that might even be wet most of the time, I would be willing to bet that most people have turf that is plenty firm enough to handle the weight of a ballasted tractor.
Here is my reasoning...I will use my equipment and my life as an example.
My tractor, with the home made rear hitch and the permanently mounted Johnny Bucket sub-frame weighs about 850 pounds when fully fueled (without the mower deck). With my big butt in the seat it goes to 1,120 pounds. Of this weight, 650 pounds are on the rear wheels and 470 pounds are on the front wheels. The ground under each rear wheel sees 325 pounds. The contact patch for each rear wheel is 9" wide and 5" long, or 45 square inches. This works out to just about 7.25 pounds per square inch of pressure on the ground. Filling each tire with Rimguard added 77 pounds. The cast iron wheel weight added another 56 pounds for a total of an additional 133 pounds per wheel, raising the total weight for each wheel to 458 pounds. This raises the pressure exerted to the ground to just over 10 PSI.
I did not add in the weight of the deck because on my machine, the deck is free floating...it rides on the rear rollers directly on the ground. It does exert some downward pressure on the front wheels, but really none on the rears. If you have a suspended deck, your results may be different.
Here is the kicker...
I went out and got the two pairs of shoes that I would normally be wearing when out and about on the lawn. One is a pair of "deck shoes" and the other is a pair of tennis shoes. the bottoms of the shoes are not flat. I wear 12-1/2 EEEs, so I have big feet to help distribute the load of my body, but the fact that the shoes are not flat changes the actual contact patch with the ground. So...I put on each of the shoes, stepped in some shallow water, then stepped onto paper to get an outline of the actual contact patch of my shoes. Interestingly, these are two completely different types of shoes. they are not flat like basketball shoes and their contact patches looked completely different. What was interesting is that both shoes had nearly identical overall contact areas. The shoes were about 12-1/2" long and more than 4" wide at their widest points, yet their total contact area when I stepped on the paper was only 31" for the deck shoes and 30" for the tennis shoes.
When I stand on my lawn, I am exerting roughly 4.5 PSI of pressure on the ground. When a person walks, they generally have most of their weight on one foot at a time, which means that if I evenly place my feet down in that manor, I am then transmitting about 9 PSI to the ground just by walking. If you add to this that we generally don't walk flat footed, but instead heel to toe, this pressure becomes even greater.
Trial number two...OK, so I am a big guy. What if I was a young woman, very slim and very fit? Well, my 19 year old daughter is just that. She is a very athletic and fit size 2. She weighs 115 pounds. I di the same thing with her tiny little size 7-1/2 womens shoes. Her contact patch was only 13 square inches per shoe. Guess what? It worked out to within two decimal points of my results...almost exactly 4.5 PSI when standing.
With these measurements, I would say that if my daughter runs across my lawn in her tennis shoes, she exerts a higher PSI on the soil than my Prestige with my fat butt on the seat plus 133 pounds of wheel ballast on each side.
So, after all of this...do we really need to worry about soil compaction from ballasting our rear tires? Will the added 3 PSI really make that much of a difference?
I will say that the difference when mowing my ditch or driving up my steeper areas is much more stable and produces much less wheel slippage than prior to ballasting the wheels.
I own a 2017 Simplicity Prestige 27/52 EFI, JB Jr, Johnny Plow Jr.
From 2015 to 2017 I owned a used 2013 Simplicity Conquest 27/50.
From 1996 until 2015 I owned a White LT-16 Vanguard V-twin and 2 stage blower.
In 1991 I purchased a used 1984 Gilson 16 HP opposed twin. It was a horse!