L3800 - 6" wheel spacers

   / L3800 - 6" wheel spacers #11  
I had loaded rear tires as well. I think that properly inflated, tires will absorb shock loads for the axles.
 
   / L3800 - 6" wheel spacers
  • Thread Starter
#12  
How many hours and what kind of use?

~200 hours over the last year.

I keep sheep on 45 hilly acres, and that tractor is my do all machine.

I never take the loader off (alternate between bucket and grapple) and most of the time the bush hog is on - and I use it as a carry all, often with 2 or three square bales and several water buckets strapped to it, plus a similar load in the bucket.

Not much ground engagement, other than driveway maintenance with a box blade... but that is a 1/4 mile stretch of uphill gravel that needs constant attention. Beyond that, I occasionally pull a single bottom or chisel plow to break up some fields for fodder beets and such.

Last year had a fair amount of extra challenging hours, as we put in a new farm road with the help of a cat dozer and dozens of hours were spent moving rock with the grapple at max lift capacity as well as spreading 100+ tons of #2 stone. I was more worried about the front axle than the rear.

Knock on wood, zero issues. She might blow tomorrow, but I got more work done in the past year much more safely than in the previous 9.
 
   / L3800 - 6" wheel spacers #13  
At the risk of stoking the controversy further, I think the "danger" of wheel spacing is overestimated on this forum.

The rear axle (or any independent wheel axle) has an outer and an inner bearing. In the figure below, the axle is 070, the outer bearing is 100 and the inner bearing is 140.

Let's call the distance between wheel centerline to the outer bearing r1, and the distance between the outer bearing and the inner bearing r2. Let's also say that each rear wheel supports a load of W lbs.

The radial force experienced by the outer bearing is W*(1 + r1/r2) and the radial force experienced by the inner bearing is W*(r1/r2) in the opposite direction. The outer takes the brunt of the static and dynamic load, and is physically larger in most of our tractors.

I have the same tractor as you (I love mine!) except for engine HP. I don't know for sure, but I'd guess approximately that r1 = 10" and r2 = 8" or so. The rear wheels probably support about 40% of the weight of the tractor+loader, plus basically 100% of the operator and rear implement weight. For sake of example let's say that comes to 1000lbs per wheel.

So without the spacer, the outer bearing supports 1000*(1+10/8) = 2250 lbs, and the inner supports 1000*(10/8) = 1250 lbs. No problem, that's the design.

With the 6" spacer, r1 increases to 16". The outer bearing now supports 1000*(1 + 16/8) = 3000 lbs (33% increase), and the inner supports 1000*(16/8) = 2000 lbs (60% increase).

That might seem like a lot of additional stress on the bearings in percentage terms. However, the engineering designs had to consider worst-case scenarios, including dynamic loading (bumping around with no suspension) while supporting the largest possible rear implement the tractor can carry. AND the design would have been spec'ed with at least a safety factor of 2x, probably much more.

So unless you're driving at top speed over the bumpiest ground you can find with 1600 lbs on the 3pt hitch 100% of the time, I doubt you are even coming close to the design limits for your bearings. That said, there will always be someone who has a horror story; I'm only suggesting that as long as you operate within reasonable limits, I suspect the bearings will last longer than you. Have fun!

1616103641346.png


PS In my observation, most of the "wheel spacers are bad" stories come from the car/truck world, where r1 and r2 are smaller than on tractors, especially on the front wheels, and therefore adding a spacer makes a much bigger difference in % terms.
 
   / L3800 - 6" wheel spacers #14  
At the risk of stoking the controversy further, I think the "danger" of wheel spacing is overestimated on this forum.

The rear axle (or any independent wheel axle) has an outer and an inner bearing. In the figure below, the axle is 070, the outer bearing is 100 and the inner bearing is 140.

Let's call the distance between wheel centerline to the outer bearing r1, and the distance between the outer bearing and the inner bearing r2. Let's also say that each rear wheel supports a load of W lbs.

The radial force experienced by the outer bearing is W*(1 + r1/r2) and the radial force experienced by the inner bearing is W*(r1/r2) in the opposite direction. The outer takes the brunt of the static and dynamic load, and is physically larger in most of our tractors.

I have the same tractor as you (I love mine!) except for engine HP. I don't know for sure, but I'd guess approximately that r1 = 10" and r2 = 8" or so. The rear wheels probably support about 40% of the weight of the tractor+loader, plus basically 100% of the operator and rear implement weight. For sake of example let's say that comes to 1000lbs per wheel.

So without the spacer, the outer bearing supports 1000*(1+10/8) = 2250 lbs, and the inner supports 1000*(10/8) = 1250 lbs. No problem, that's the design.

With the 6" spacer, r1 increases to 16". The outer bearing now supports 1000*(1 + 16/8) = 3000 lbs (33% increase), and the inner supports 1000*(16/8) = 2000 lbs (60% increase).

That might seem like a lot of additional stress on the bearings in percentage terms. However, the engineering designs had to consider worst-case scenarios, including dynamic loading (bumping around with no suspension) while supporting the largest possible rear implement the tractor can carry. AND the design would have been spec'ed with at least a safety factor of 2x, probably much more.

So unless you're driving at top speed over the bumpiest ground you can find with 1600 lbs on the 3pt hitch 100% of the time, I doubt you are even coming close to the design limits for your bearings. That said, there will always be someone who has a horror story; I'm only suggesting that as long as you operate within reasonable limits, I suspect the bearings will last longer than you. Have fun!

View attachment 690721

PS In my observation, most of the "wheel spacers are bad" stories come from the car/truck world, where r1 and r2 are smaller than on tractors, especially on the front wheels, and therefore adding a spacer makes a much bigger difference in % terms.

I agree with most of your analysis. The dangers of not using spacers to prevent rollover are more significant.

Static forces are small compared to dynamic forces particularly on uneven ground. FEL are particularly hard to balance.

Have never had problem with rear wheel bearings from spacing. Heard of bearing problems with 4wd loader front axle bearings being spaced wider. There are bearing problems without spacing too.
 
   / L3800 - 6" wheel spacers #15  
The dangers of not using spacers to prevent rollover are more significant.
This is a really important point, Smokey. In the car/truck world, people often add spacers cuz they look good or to facilitate snazzier wheels.

But in the tractor world, spacers are only added for a good reason. Trading the small probability of shortened bearing life for a wider stance on hills is really a no-brainer. Bearing life is irrelevant if you roll and injure yourself or damage the tractor!
 
   / L3800 - 6" wheel spacers #16  
IMG_1017.JPG
is the bearing life equation where C is the dynamic load capacity, p is the actual load, and N is rotating speed in rpm. For a ball bearing, e is 3 so life is rudeced by the cube of the load. However, keeping the loader on all the time significantly reduces bearing load. Filling the tires has little or no effect as the weight of fluid is supported by the ground until the tires come off the ground (okay, some from the bucket load but it’s a negative load). Front axle bearings are marginal at best on Kubotas - my average life has been in the 600 hour range but they’re easy to replace. Rear wheel spacers - I don’t think it will be a problem for people using loaders and enough here say they’ve done it. It’s easy to find videos on how to replace the rear bearings on YouTube because there are many ag tractor replacements shown usually due to rear duals.
 
   / L3800 - 6" wheel spacers #18  
Thanks for the update :)

I have 3" spacers on my L3800 and have often thought I should have gone for 4".
 
 
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