Upgrading 4WD tractor tires, could use info on front to rear size ratios

[Dunno]

Hello,
Upsizing farm tractor tire size, and desired tires don’t conform with factory front/rear ratio. Going from 11.2-24 fronts (43.5” tall) and 15.5-38 rears (62”) with size ratio of .70, to 13.6-24 (47.6”) and 18.4-34 (65.1”) which is a front/rear ratio of .73. I remember Tony Jacobs saying that for the 4WD Elenco’s he deals with, 0-5% overdriven in front is okay. To get correct .7 ratio front to back I’d need to run 68” tall rears which won’t fit. I need the extra width due to increasingly wetter field, and need the traction and flotation of wider tires. Tractor is a Ford 4610 with 60hp. Thanks.

 

[oldnslo]

If running in wet fields where tires can slip it probably won’t matter very much. On ground with good traction it might be a concern.

 

[rScotty]

I swapped tires on several tractors and didn't break anything. Came close a couple of times when there was so much windup in the shafts that I couldn't get it out of 4wd even by backing up. You could hear things start to pop, it became difficult to turn, could not get it to shift out of 4wd. Dumb luck saved me.

What I found is that wet sticky mud and snow were the high traction surfaces - the ones to worry about. Dry dusty or hard ground hardly mattered. Heavy plowing or tedding or any work with a heavy rear 3pt implement seemed OK because the front was light enough to slip as needed. Hot asphalt was the very worst. If you leave it in 4wd on a hot summer day and drive a mile on asphalt....well, I just wouldn't do it. Chances are good something will break. Especially with suitcase weights on the front.

Things I've found:
1. When comparing tire Lead/Lag always use the tire spec: Loaded Circumference.
Loaded Circumference is in every tire book by every tire maker & you cannot figure it out from diameter.
But you can measure what you have now for yourself & match it to book specs.
Measure Loaded Circumference with wet paint dots on the tire on a straight dry road. Measure in 2wd between the dots. For calculating lead/lag, front to rear paint dot distance should match the front to rear internal transmission ratio.
3. You want lead to be slightly greater than lag, but otherwise as close to zero as possible.

Keep in mind that the 5% ratio is cumulative until something slips or breaks. If one tire revolution puts 5% windup on the shaft that shaft starts the next revolution already wound up. Pretty quickly things had better slip. The closer to 0% lead/lag you get, the more revolutions that takes.
I made up one tractor with as near zero lead/lag as I could get. It worked great.

rScotty

 

[Dunno]

rScotty,
Thank you for the detailed explanation. I will research the loaded circumference. Also, the white dot trick is great to know. I’ll use both for my new tire selection. I too was under the assumption that wet ground would give, so glad to know different. I will play with the tire size combos to get to .7 so I don’t have to worry about it.
Best regards.
John

 

[LouNY]

Or add duals to the front and if needed to the rear, or maybe some of the new LSW tires.

Or just go wider in front, it may take a custom rim but;

 

[rScotty]

rScotty,
Thank you for the detailed explanation. I will research the loaded circumference. Also, the white dot trick is great to know. I’ll use both for my new tire selection. I too was under the assumption that wet ground would give, so glad to know different. I will play with the tire size combos to get to .7 so I don’t have to worry about it.
Best regards.
John

Yeah, that white dot trick works real well. If I had been thinking ahead, I'd have done that on every new tractor just as a piece of into to have and keep.

When we look up "loaded circumference" from the manufacturer, it is just their guess as to how your tractor is loaded and distorting their tires.
But when you measure using the paint dot trick you get a "loaded circumference" that is exact for that particular tire on your particular tractor.

There's a trick to get the internal F/R gear ratio too, although that spec is usually book accurate. The trouble with that internal gearing book spec is that if a manufacturer switches brands of tires, he may or may not update that ratio with a different gearset. Some do, some don't, always good to check it. Especially on larger used equipment.

 

[Dunno]

Thank you guys! Great info. Lou, I didn’t know how to find that info on the tires, thanks. How would I get a custom rim made? Do you know a vendor? I’ll be playing with the posted manufacturer’s diameter numbers to find a good ratio. Then I’ll check the loaded circumference. At present I can only traverse much of my field with a tracked skid steer. We had drought conditions a few years ago, and nothing wanted to grow. Now, just the opposite. Interesting happenings.

 

[MTGreen]

Thank you guys! Great info. Lou, I didn’t know how to find that info on the tires, thanks. How would I get a custom rim made? Do you know a vendor? I’ll be playing with the posted manufacturer’s diameter numbers to find a good ratio. Then I’ll check the loaded circumference. At present I can only traverse much of my field with a tracked skid steer. We had drought conditions a few years ago, and nothing wanted to grow. Now, just the opposite. Interesting happenings.

Try Hey Wheel in Kansas for customs (no affiliation just happy repeat customer)

 

[redman135]

Hello Dunno, JD offer a factory wide tyre option, ask your ford dealer if there is a factory wide tyre option for your model.
For your situation, as LouNY said, dual wheels, either duals all round, or duals at rear and custom wide tyre on the front. NOTE this option will mean you need a smaller diameter RIM to fit the wider tyre. Pay attention to CLEARANCE of kingpins and steering knuckles. If you are offered the option of 1 piece or 2 piece rims go for 2 piece as they are adjustable.

Duals all round means you don't need to calculate gearing. Note on some dual setups I have seeen the (front) outside tyre is slightly smaller and only contacts the ground when driving through soft ground. On hard ground the outside front dual runs under little or no load, this reduces outer bearing and steering wear and tear.

Next look carefully at the different designs for quick release. Some are more user friendly than others.

Lastly, space between the duals needs to be about 4" for mud to get between the tyres(traction reasons) then SELF-CLEAR. If the gap is to small the mud will stick and you end up with a giant "slick" tyre and no traction. Been there,didn't like that.
Warning : you may encounter sticker shock.
Good luck

 

[Dunno]

Red man,
Thank you for the advice. The tires that will keep the ratio and be wider are 12.4-24, and 18.4-30. I’m actually looking at the metric size 320/24 and 420/30, which are just a smidge different (wider) than the factory nominal tire size ratio. I’ll try those, and if they don’t float it I will consider the duals or customs. Heard today that we’ve just had the wettest March in history, and likely to be a wet summer in the northeast.
I looked at the custom wheels, looked good. Not sure where price is, but cross that bridge and heart attack when needed.
Last thing is I’m looking at are the tire manufacturers. Talk about a hot potato! Like cell phones, every one has good and bad to say about all the brands. The decision may come down to who has the tire size I need. Looking heavily at the Euro manufacturer’s especially for the metric sizing.
Best regards.