870 MFWD R4 Ag tire options?

[Skinnyfarmer]

870 MFWD. Need the high flotation of the turf tires because it’s soggy where I’m going to be working. But I need the traction of an ag tire.

Can’t seem to find anything in an ag tire that will fit my rims. Has anyone done any type of conversion to solve this problem?

Rims are 355/80D-20 rear, 25x8.50-14 front

Saw a thread that someone successfully did it with a 770.

Looking for something liked the tires pictured below.

Any tips appreciated.

Thanks

 

[John_Mc]

Have you looked in to R14 tires? Last I checked, they were only available in a limited number of sizes, but that may have changed

 

[Skinnyfarmer]

I m not familiar with R14. What are they?

 

[John_Mc]

R14 is a gross between an Ag tire (R1) and an Industrial Tire (R4). THe ones I have seen are wide, like a turf or an R4 tire, but have a more aggressive tread.

You can find out more here: Goodyear Titan R14 Tires

I don't see your size listed at present, but hopefully it's coming in the future. They list some in a 15-19.5 which fit my rear tires, and a 25x8.5-14 which are a match for my front. That's what I'll be switching to when it's time to replace my R4 tires

The other type you might look at is an R1W tire. I don't know much about them except that they are a wider version of an R1 Ag tire.

 

[RoyJackson]

Might want to look at bar-turf tires too.
They're a bit more aggressive then a regular turf and should fit on your rims.
I had them on my first Deere, a 670...

 

[Skinnyfarmer]

R14 is a gross between an Ag tire (R1) and an Industrial Tire (R4). THe ones I have seen are wide, like a turf or an R4 tire, but have a more aggressive tread.

You can find out more here: Goodyear Titan R14 Tires

I don't see your size listed at present, but hopefully it's coming in the future. They list some in a 15-19.5 which fit my rear tires, and a 25x8.5-14 which are a match for my front. That's what I'll be switching to when it's time to replace my R4 tires

The other type you might look at is an R1W tire. I don't know much about them except that they are a wider version of an R1 Ag tire.

Thanks for the input. Here is what I found.

Titan makes an exact size replacement for the front, which is great.

On the rear, there is no exact replacement. The closest tire available for the rear is a Titan pictured below. It is a 320/85R20, whereas the current turf tire is a 355/80R20.

I looked at the Rolling circumference difference between the two rear tires. The turf tire is about 124 inches and the Titan replacement is 125.11 inches. So about 1 inch difference in rolling circumference difference.

Assuming the front tire is the same, would a difference of 1” rolling circumference be enough to damage my differential?

I called my local Deere dealer and they aren’t much help.

 

[Skinnyfarmer]

Might want to look at bar-turf tires too.
They're a bit more aggressive then a regular turf and should fit on your rims.
I had them on my first Deere, a 670...

Thanks Roy. I’ve been looking and there doesn’t seem to be anything available

 

[John_Mc]

Thanks for the input. Here is what I found.

Titan makes an exact size replacement for the front, which is great.

On the rear, there is no exact replacement. The closest tire available for the rear is a Titan pictured below. It is a 320/85R20, whereas the current turf tire is a 355/80R20.

I looked at the Rolling circumference difference between the two rear tires. The turf tire is about 124 inches and the Titan replacement is 125.11 inches. So about 1 inch difference in rolling circumference difference.

Assuming the front tire is the same, would a difference of 1” rolling circumference be enough to damage my differential?

I called my local Deere dealer and they aren’t much help.

Hard to say without more information 4WD tractors are set up to have a little bit of "lead" with the front tires, so the fronts try to move over the ground a bit faster than the rear tires. The amount of lead is determined by both the tire size and the relative gearing of the front vs rear drive train.

Opinions vary, but most sources seem to agree that about 1-3% lead with the front tires is what to aim for. This Titan tire is almost exactly 1% larger than your existing rear tire, so your lead will be reduced (e.g. if your lead was 2%, it will now be 1%). If your lead was already on the high end, you may like how it handles and transmits power to the ground a bit better. If your lead was already on the low end, you may not like it at all.

Another thing to check is how the rolling circumferences of your front tires compare to the new front tires you'll be getting. Even if they are labeled as the same size, the rolling circumference could be different. If the new front tire spec is also a bit bigger that will help.

There are calculators out there that will figure the lead ratio out for you, but you need to know the gear ratio front to rear as well as the rolling circumference.

 

[gstrom99]

Consider looking for mud/off road truck tires. I bought Mickey Thompson Baja's when I needed new rears on my JD 855. Be sure to get the exact right diameter/circumference so the 4WD ratio isn't messed up.

 

[LouNY]

Depending on your axle loading you can vary the rolling circumference considerably with the pressure in your tires.
If you have a loader you might need to increase pressure when using it, kind of a pain.