JD750 4WD Tire Size question

[ctandc]

Original Bridgestone R3 6-14 tires, one of them at least finally bit the dust. Holes in the sidewall, tube blew - thought someone was shooting at me. LOL.
They are really proud of those Bridgestones, when you can find them.

Diameter is right at 25". Wondering if throwing on some 25x8.5x14s would work? Would they mount on the 6" rim?

Tire ratio for 4WD appears to be okay, just adding a bit of width.

If not - any issues going to the

6-14 REGENCY AG COMPACT TRACTOR TIRE 4 PLY​

They are R1, not turf, and eventually I'll go to R1 in the rear anyway.

 

[LouNY]

If the diameter or loaded radius is similar should be fine, when I looked up the 6-14 it listed a 24 inch diameter.

 

[rScotty]

If the diameter or loaded radius is similar should be fine, when I looked up the 6-14 it listed a 24 inch diameter.

I think Lou means loaded diameter, not radius.
But I'm curious why not replace them with the same tire again? Tire price is nothing compared to the expense that can happen with a 4wd and mismatched tires.

 

[pmsmechanic]

I installed 26x12x12's on my 4410 in place of the factory 25x8.5 x14 tires. In 3000 hours the only issues I've had is wrecked tires from to low a ply rating. Going to 6 ply tires solved that. The tires are slightly larger but the only issue is that the front doesn't lead as much, which results in the front tires skidding on sharp corners. If it bothers me I just disengage the front wheels for corners. All in all the benefits outweigh the disadvantages.

 

[LouNY]

I think Lou means loaded diameter, not radius.
But I'm curious why not replace them with the same tire again? Tire price is nothing compared to the expense that can happen with a 4wd and mismatched tires.

Often the manufactures will list a loaded radius measurement, then they also list an overall diameter. The loaded radius is what would be used to calculate a loaded circumference. Which would be the critical dimension .

I installed 26x12x12's on my 4410 in place of the factory 25x8.5 x14 tires. In 3000 hours the only issues I've had is wrecked tires from to low a ply rating. Going to 6 ply tires solved that. The tires are slightly larger but the only issue is that the front doesn't lead as much, which results in the front tires skidding on sharp corners. If it bothers me I just disengage the front wheels for corners. All in all the benefits outweigh the disadvantages.

I'm a bit confused you went with a taller?? front tire.
And your front tires are leading as much as the smaller tire did. They should be leading more if they are taller.

 

[rScotty]

Often the manufactures will list a loaded radius measurement, then they also list an overall diameter. The loaded radius is what would be used to calculate a loaded circumference. Which would be the critical dimension .

You're right. Neither one us should have used loaded radius OR loaded diameter - I'm not even sure that either of those have a physical meaning when we are talking about the loaded shape of a tire.

Loaded Circumference is the correct dimension to compare tires for 4wd lead/lag calculations.

rScotty

 

[pmsmechanic]

I'm a bit confused you went with a taller?? front tire.
And your front tires are leading as much as the smaller tire did. They should be leading more if they are taller.

Many years ago I had the same confusion, but a taller tire actually goes slower. Most front wheel assists have a certain amount of lead built in. A taller tire takes out part of that lead and I noticed that when I turned corners. I still have a bit of lead but not as much as I did before I installed taller tires.

I had it explained to me once and it made sense but I've forgotten the explanation. It has something to do with the circumference of the tire and the lead built into the drive train.

What I call lead is the difference between the front and rear tires. The fronts are geared so that they always pulling the rears slightly when engaged.

 

[rScotty]

Many years ago I had the same confusion, but a taller tire actually goes slower. Most front wheel assists have a certain amount of lead built in. A taller tire takes out part of that lead and I noticed that when I turned corners. I still have a bit of lead but not as much as I did before I installed taller tires.

I had it explained to me once and it made sense but I've forgotten the explanation. It has something to do with the circumference of the tire and the lead built into the drive train.

What I call lead is the difference between the front and rear tires. The fronts are geared so that they always pulling the rears slightly when engaged.

A taller tire does go slower. But lead/lag on 4wd assist is not about the relative tire speed between the front and rear tires. Lead/lag depends on how far the outer surface of the tire travels during one rotation of the axle, not how fast it spins.

Think of it this way: If the difference in internal gearing exactly matched the difference in tire (loaded) circumference, the lead/lag ratio would be zero. We can change lead/lag by changing internal gearing or by changing tire circumference. Tires are easier.

Increasing the height of the front tires increases the circumference of those front tires. And increasing the circumference of the fronts also increases the amount of ground that they cover in one axle revolution...so the taller tire has more lead, not less.

We spend a lot of time on lead/lag here on TBN because it matters for our 4wd assist tractors with their heavy front end loads and vastly different tire sizes. It sure isn't an easy concept to "see". If we had AWD and same size tires front and rear like an SUV or a Toolcat we wouldn't even have to think about it.

rScotty

 

[LouNY]

Many years ago I had the same confusion, but a taller tire actually goes slower. Most front wheel assists have a certain amount of lead built in. A taller tire takes out part of that lead and I noticed that when I turned corners. I still have a bit of lead but not as much as I did before I installed taller tires.

I had it explained to me once and it made sense but I've forgotten the explanation. It has something to do with the circumference of the tire and the lead built into the drive train.

What I call lead is the difference between the front and rear tires. The fronts are geared so that they always pulling the rears slightly when engaged.

Yes, but a taller tire is going to cover more ground for the same number of revolutions.
Because it is covering more ground for the same number of revolutions it is going to MORE lead then a shorter tire.
The tire with the greater loaded circumference is going to travel further for each revolution creating more lead not less.
A taller tire can turn slower to cover the same length of ground but if mechanically tied to a nother tire that will create a difference in either lead or lag.

 

[LouNY]

A taller tire does go slower. But lead/lag on 4wd assist is not about the relative tire speed between the front and rear tires. Lead/lag depends on how far the outer surface of the tire travels during one rotation of the axle, not how fast it spins.

Think of it this way: If the difference in internal gearing exactly matched the difference in tire (loaded) circumference, the lead/lag ratio would be zero. We can change lead/lag by changing internal gearing or by changing tire circumference. Tires are easier.

Increasing the height of the front tires increases the circumference of those front tires. And increasing the circumference of the fronts also increases the amount of ground that they cover in one axle revolution...so the taller tire has more lead, not less.

We spend a lot of time on lead/lag here on TBN because it matters for our 4wd assist tractors with their heavy front end loads and vastly different tire sizes. It sure isn't an easy concept to "see". If we had AWD and same size tires front and rear like an SUV or a Toolcat we wouldn't even have to think about it.

rScotty

Yep,