Tires can I replace front tires w/1/2" smaller diameter on Kubota 4wd/hydrostatic?

[jefraser]

Can I replace the front tires on my Kubota 4wd-hydrosatic with 1/2'' smaller diameter? Original tires were 20.5's and the tire store has only 20's. I know on my truck you must have all four tires the same. Obviously tractors fronts and rears are different so I am confused and wondering, what's up?

 

[carmedic310]

The gearing is different from front to rear on tractors to compensate for tire size.I would not change tire size.different manufacturers can be different sizes even though they have the same number on the tires.You could wind up with a tire that could actually be an inch taller or smaller between them.I would stay with what you have

 

[RaydaKub]

Usually fronts are geared so they go a tad faster than the rears to help pull you around. A smaller tire would take away that ratio and you might end up pushing the front end and that will ruin your traction advantage.

Plus the gear wear. I wouldn't do it.

:welcome: to TBN!

 

[Oldtractorfixer]

Wouldn't a worn out tire be more than 1/2 inch smaller than a new one. If you were on pavement you might have an issue but any time you need fwd you have slipage that should make that small a difference not a factor. Just take it out of fwd when not needed.

 

[tomf]

I was just researching this a couple of weeks ago because I found the topic interesting. My Kubota B2400 takes 21x8.00-10 tires on the front. No one makes that size tire anymore. So I'll have to make a decision when my tires wear out: go with non-optimum tires or replace all 4 so the proper ratio is maintained. Anyway, I think the general consensus was that normally Kubota puts slightly oversize tires on the front because they tend to wear faster than the rears. As they wear they past through the optimum circumference for the proper gear ratio. So replacing with slightly smaller would be ok but not optimum. It's my understanding the gear ratio only applies when you are in 4wd. So as long as you don't use 4wd you are fine for sure. So limit your time in 4wd.

BTW it's the circumference that matters so check the circumference of the tire you at which you are looking.

 

[GManBart]

Usually fronts are geared so they go a tad faster than the rears to help pull you around. A smaller tire would take away that ratio and you might end up pushing the front end and that will ruin your traction advantage.

Plus the gear wear. I wouldn't do it.

:welcome: to TBN!

I suspect there wouldn't be any significant gear wear....the system as to be able to tolerate wear pretty well, or any time the tire size wasn't exactly at spec, it would be causing wear that would ultimately lead to failure. There would also be a pretty obvious warning about it in the manual....like never replace only one front tire, because mismatched front tires would be a bigger problem than both being slightly larger, or smaller than spec.

 

[arrow]

Usually fronts are geared so they go a tad faster than the rears to help pull you around. A smaller tire would take away that ratio and you might end up pushing the front end and that will ruin your traction advantage.

Plus the gear wear. I wouldn't do it.

:welcome: to TBN!

The ratio for the roll out comparing backs to front must be within the parameters of the tractor manufacturer and usually that is the fronts need to rotate 2% faster than the rears. This is Firestones sight explaining lead/lag…...http://firestoneag.spinutech.com/webres/File/Tire-Info/TireInfo-LeadLag.pdf

 

[Don87]

Can I replace the front tires on my Kubota 4wd-hydrosatic with 1/2'' smaller diameter? Original tires were 20.5's and the tire store has only 20's. I know on my truck you must have all four tires the same. Obviously tractors fronts and rears are different so I am confused and wondering, what's up?

The biggest question i see is........can they get the tires you need? It may take a week or so, but.............on the other hand I wouldn't be too concerned about 1/2 inch difference as long as both fronts were replaced.

 

[npalen]

A good spec to compare when considering replacement tires for FWA is rolling radius This is the distance from the centerline of the axle to the "pavement" with tires at rated pressure and installed on the tractor. The rolling radius actually determines how far the tractor moves for one tire revolution.
Using the 2% rule mentioned above involves knowing the tractors actual gear ratio between front and rear wheels and using a bit of math to see if prospective tires fall within the 2% range using the rolling radius.

 

[pat32rf]

And the rolling radius is going to change each time you load up the bucket or raise a load on the 3pth. You use 4wd because the tires are slipping, so as long as you have poor traction it really isn't going to cause much problems.