You did not say how you did the weighing.
What are these numbers? Weight changed from 138/51 to 110/80
An MTD is one of the lightest and easiest machines to use. Because of what you have written you seem to have had a great deal of trouble clearing your drive arc. I though it possible you might have had unequal or low pressure over the years and since you have asked about pressure that’s probably the case.
A factor in clearing an arc is how you do it i.e. following the arc or doing tangents & etc. If your machine is slightly favoring on side or the other you could be mostly fighting a mild steady turn when doing the arc. If both are low it’s also a factor.
Tire pressure is important.
Generally, companies spec somewhere around 14-17, 15-20 or other numbers close depending on the company and model. You machine is spec’ed at 15-20.
If pressures are unequal the machine will pull and be difficult to turn, just how difficult depends on the range and the difference. There are issues for low pressure. There’s no correct pressure other than what ends up comfortable for you doing your area with your model. Some people find pressures below spec to be better for grip and needed for their area. For another person an area with the same machine high pressure would be much better. Unusual is an area where unequal pressures would be a benefit.
Makers all suggest a pressure range but the actual number is a matter of what ends up comfortable for you using your machine doing your area.
I used a set of bathroom scales. 20 years ago when I started oval racing and didn't want to invest in the very expensive electronic scale sets I purchased an inexpensive way to leverage bathroom scales; these scales where purchased to work with that but have languished on a shelf in the garage for 10 years.
When we saw the Deere/Simplicity, the nose was much heavier through the handlebars. My wife couldn't lift the nose to move it around, and I needed to put some muscle in it. Deere had a weigh in the catalog that I was told was incorrect. We wanted to know what the issue was, since the nose riding up is a problem in hard snow.
The numbers were not what was expected. They had similar wheel weights put different nose weights, different wheelbases, and different grip locations (same height though), and different handlebar geometry. The wheel weight, as asked about in another post that was also invaded by the two year olds, mentioned it and asked for an explanation. I thought about and guessed tire pressure could be an issue.
It was, at least partially. It didn't effect the feel from the handlebars which is a function of front/rear weight, but did effect side to side weight. It also brings up the question of what is the right tire pressure.
In off road vehicles, and in racing cars, tire pressure is a major factor in traction. A Hummer has the ability to bleed or pump up the tires from controls in the cab. Off road and dirt track racing cars have retention rings to clamp the tire bead because of the low pressures used. Even asphalt cars some times run left front pressures so low the tire gets popped off the bead in a bump (oval asphalt rims have no safety bead).
It appears that adjusting the tire pressure could increase traction by affecting the left/right wheel weights (even probably has more traction) and by affecting the tire's performance. On the second my guess is lower pressure probably has more traction in slippery conditions and higher pressure may have more traction in slushy conditions.
Has anyone experimented with that?