Tire ratio front to rear

[Blue Mule]

On a lot of compact tractors you get an option of R1, R3, or R4 tires. What I've noticed on many brands and models is that the size of the front tires is always the same between the tire style options, but the size of the rear varies. For example, my tractor has 43" R4 tires, but if I had gone with R3 tires they would have been 41" tires. Despite this, BOTH options would have resulted in 25" fronts.

How are they able to do this and maintain functionality of the 4-wheel-drive system without binding?

 

[90cummins]

My Ford 1720 CUT had turf tires from the factory and the driveline would bind up severely within several feet.
The fronts were trying to walk away from the rears.
I adjusted tire pressures to minimize the issue but more importantly I was very conscious of the issue and engaged the fwd only when absolutely needed.
I eventually resolved the issue by lowering the front tire pressures until it would roll engaged without binding.
I then measured the distance traveled in 1 revolution and then went on tire rack and looked for an automotive snow tire with that rolling distance.
Bought 2 new radial snow tires and adjusted the front & rear until there was zero binding.

90cummins

 

[oosik]

After 38+ years out here I know my property well and when to engage 4WD. I've run the M6040 down my bare gravel driveway - it's a mile long - in 4WD and it didn't bind up.

 

[Blue Mule]

I don't experience binding or hopping when in 4WD. No issues at all. I guess my main question was just how are they able to offer rear tires that are 5% different from the factory without changing the fronts to match?

I guess the answer is, they don't. They anticipate that the tractor will always be on soft soil and it won't cause an issue.

 

[Texasmark]

A few thoughts:
4wd is for times that you need extra traction....driving down an asphalt road isn't one of them.
Percent difference in straight ahead rolling circumferences are measured in low single digits.
The front has to have the most grip to maintain steerability, rather than being pushed by the rears in who knows what direction.
Front axle traction is supplementary, meaning the rears do the work; the fronts only pull themselves to prevent drag like in 2wd applications.
Differences in "rolling circumference" can be measured and used if the tractor's gear ratio is known.
Apparent ratios change with changes in steering angle since fronts and rears are in different sized (circumference) circles when turning 360*.

That's about the limit of what I have picked up from who knows where about the subject.

 

[PILOON]

Yep, on gravel, grass, snow there should be little or no binding.
But on grass you'll sure cause unwanted skid marks especially when turning.

BUT, on asphalt and concrete you sure will feel that lead bind and greatly shorten the front tire tread life!
One friend often lent his B21 to folks that drove home on asphalt and it cost him fronts in a very short time (like 200 hrs)
Another guy has over 1000 hrs on a similar machine with same fronts and showing minimal wear BUT he never drive on paved surfaces.

 

[ptsg]

Wondering what the tire ratio front to rear is on this one.

 

[arrow]

Wondering what the tire ratio front to rear is on this one.

View attachment 686040

I'd say just about a perfect 1 to 1.

 

[Texasmark]

I'd say just about a perfect 1 to 1.

I'd add a few percent making the front do the pulling to aid in steering ability....perventing the rear from pushing the front around interfering with steering ability. On the subject, I was out in the snow yesterday with my new LS and tested the ratio. I kept the R4s on the front but changed the rears to R!s and wanted to see how my match went. As close to perfect as one could imagine, even in mild turns. In tight turns I could see a slight blur of the snow but that could have just been the angle at which the lugs were meeting the snow and providing traction.

 

[90cummins]

Next time you have a stretch of bare road engage 4wd straight that will tell you very quickly how close you are.
You can tweak the ratio to perfection by adjusting tire pressures.

90cummins