Front to Rear tire raito

[npalen]

It would be interesting to compare actual measurements of rolling circumference and loaded radius to see how close they are to the 6.28 ratio.

 

[Blake13]

It would be interesting to compare actual measurements of rolling circumference and loaded radius to see how close they are to the 6.28 ratio.

Agree, interesting. I predict that a ratio determined from loaded radius would be very close one determined by rolling circumference. However, closeness compared to the gear ratio depends on the tires chosen by the tractor manufacturer.

 

[npalen]

What I was referring to would be to compare the two actual measurements on just one wheel. In other words, measure the loaded radius with the tractor sitting still. Then drive the tractor to turn the wheel precisely one revolution and measure the distance traveled. Then compare the ratio of the two measurements to 6.28. (2pi)
I get what you're saying about "tires chosen by the manufacturer".

 

[PILOON]

The accepted nom is to have the front lead by 5%.

The reason is tire wear!
The front being smaller will wear faster than the rears and actually later in life will be lagging the rears.

Only a tractor with same tires up front as the rears don't need that lead.

 

[npalen]

The accepted nom is to have the front lead by 5%.

The reason is tire wear!
The front being smaller will wear faster than the rears and actually later in life will be lagging the rears.

Only a tractor with same tires up front as the rears don't need that lead.

That makes sense and is the first time I recall hearing it presented that way. I suppose the type of tread is a factor in the wear differential between front and rear.
I've always heard that turning ease is the reason for the front lead but suppose it could be a combination of both reasons.

 

[winston1]

The 220d/226D service manual states 1 to 4% with a wear limit of 0 and 6%. Wouldn't doubt most of the old YM models came with pretty close specs.

 

[ovrszd]

36 posts in and nothing confirmed. Heheheheh.

 

[iseki]

Just look at a tractor catalog with similar tire sizes, then see the options they offer.You can by - 7-16 _ 12.4-24 or 8-16 _ 13.6-24 or 280/70r16 _380/70r24(340/85r24)

 

[rScotty]

36 posts in and nothing confirmed. Heheheheh.

That's OK. I wouldn't expect any solid answer. Getting the lead % is a compromise between steering and driveline torsional stresses that compact & utility size 4wd tractors have to put up with because they don't have a center driveshaft differential like larger more specialized 4wd machines have.

As I see it, what we are doing in this thread is talking about what factors go into calculating that compromise.....making sure we cover the important ones and getting the arithmetic right.

But at the end it's still going to end up as a personal choice. I doubt that there is any one answer fits all soils or all tire types.
rScotty

 

[ovrszd]

That's OK. I wouldn't expect any solid answer. Getting the lead % is a compromise between steering and driveline torsional stresses that compact & utility size 4wd tractors have to put up with because they don't have a center driveshaft differential like larger more specialized 4wd machines have.

As I see it, what we are doing in this thread is talking about what factors go into calculating that compromise.....making sure we cover the important ones and getting the arithmetic right.

But at the end it's still going to end up as a personal choice. I doubt that there is any one answer fits all soils or all tire types.
rScotty

And the elements of the equation change dozens or hundreds of times each time the tractor is used.

P.S. In the tractor world the only truly 4wd tractors are center pivot. All others are FWA.