Matching front and rear tires on a FWA tractor

RGMartin · Nov 15, 2011

Trying to put together a set of tires on a FWA tractor. It seems there is huge variation on rolling circumference and diameters of tires of a given size.

Is there a standard percentage that the fronts need to turn faster than the rears? I know that the fronts can't turn slower as you would get wind-up like I have now....

rustyfarmall · Nov 15, 2011

(quoted from post at 06:29:16 11/15/11) Call me silly,

But, I'd just look in the owner's manual and put on the tire sizes it calls for.

Allan

GOOD answer!!

Allan in NE · Nov 15, 2011

Call me silly,

But, I'd just look in the owner's manual and put on the tire sizes it calls for.

Allan

RGMartin · Nov 15, 2011

There the problem lies. Discrepancies in the sales data, and specification sheets.

The tractor has the original 25 year old English made tires on the rear. In a size that wasn't supposed to have been used with the syncromesh transmission.

The fronts are a junkyard set installed just to have tires on the front, one maybe 2 sizes too small.

oj · Nov 15, 2011

Usually, i think, front wheels turn 5 - 10% faster than rears... if you can tell us the make and model, someone will be able to give you an idea what they run on their machines.

We had a Ford 8210 years ago that we put front tires on 3 sizes bigger for more traction pulling a spud harvester... made a big difference, but had to make sure that the front drive wasn"t in on the road...

RGMartin · Nov 15, 2011

1494 Case/DB Syncro with orig 18.4-34 rears, 16" rims. Fronts are on 10x24" rims, which DB used with 11.2 and 12.4s, the 13.6s came on 11"rims from what I gathered. If it was a Power shift it would have been a 18.4/13.6 combo...

It seems rolling diameter of a given size varies 5% or more. So if the rears are slightly worn and "small for their size" they might be better off with the next size smaller fronts if the fronts are "big for their size".

oj · Nov 15, 2011

I'd go with the same combo as the powershift model... don't think the front axle drive was any different for either model, so i don't see why the tires would be different.

I expect someone has change them at some point and had to "make do" with what they had on hand...

Given a choice, i'd fit large tires rather than smaller ones on the front axle... Kabota had a 2 speed front axle to help the tractor turn on tight steering lock... you will get wind up in the transmission of any fwd tractor anyway on a hard surface if the drive is left in, I remember our first tractor that engaged the MFD when the brakes were applied, use to make the front jump sideways a few inches when the tractor was stopped on full lock and the brakes released.

Ken Macfarlane · Nov 15, 2011

The fronts should have 1-5% more lead than the rear. If you don't
know the mechanical ratio just use the originals.

Some models of Kubota came with a 5% lag, mine included. I found
the mechanical ratio and put the correct front tires on it when they
wore out.

mkirsch · Nov 15, 2011

You are WAY overthinking this.

Ideally you should replace all four at the same time, but if you can't you should replace the fronts with the correct size for the NOMINAL rear tractor tire size... In other words, if the manual says 18.4x34 rear and 13.6x24 front, you should put on new 13.6x24 fronts.

Don't get all worked up about how wore the rears are or how much variance there is between brands. You'll just end up chasing your tail when it comes time to replace the rear tires.

If your front end is leading the rears, the partially-worn rear tires should "slide" enough to make up for any excessive lead.

Matching front and rear tires on a FWA tractor

RGMartin

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rustyfarmall

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Allan in NE

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RGMartin

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oj

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RGMartin

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oj

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Ken Macfarlane

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mkirsch

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