Does widening front end stress axle/bearings more?

[CobyRupert]

I copied the following over from another thread that was an equipment specific thread and wanted to have a general discussion:

"Changing the front tire rim configuration to a wider stance increases the forces on the axle and bearings."


I hear that often, but have been thinking about that lately. It would seem that if the axle width stays the same, changing the configuration of the rim changes nothing regarding the axle span (width), and it's load capabilities?

I also say that reversing the "curve of the rim" (dish) also does nothing regarding the torque put on the bearings, all it does is change the direction of that torque from clockwise to counter-clockwise (and vise-versa on the other side). (That is, any offset that cause the torque on the bearings is still the same distance, but now it's just on the other side of the vertical line.)

The ONLY thing that increases the torque on the bearings is when you increase the offset of the center rim hub on the outer rim (if you have the adjustable type that aren't welded at this connection).

I'm interested to see if people agree with this.

 

[RaydaKub]

It would depend on the curve of the rim. Every model is going to be different, but in general, yes, this is going to affect your bearings.

For the sake of argument, assume it is mounted curve in and that pretty much centers the rim on the hub. There is basically equal wear on the inner and outer bearings. There is very little torque applied because it is centered (or close to it). When you flip the rim around (curve out), the center of the force is going to move outside of the outer bearing. Now the outer bearing carries most of the load and the inner bearing becomes a cantilever to the outside. How much force this applies will be dependent on how much curve there is to the rim. The vertical loading is going to be the same because the tractor weighs the same. But the leverage will change how the load is carried.

 

[Bluegill2]

Move the front tires out further from the hub and it will put more stress on the bearings.

Why would someone want to widen front wheel stance?

 

[Gary Fowler]

It would depend on the curve of the rim. Every model is going to be different, but in general, yes, this is going to affect your bearings.

For the sake of argument, assume it is mounted curve in and that pretty much centers the rim on the hub. There is basically equal wear on the inner and outer bearings. There is very little torque applied because it is centered (or close to it). When you flip the rim around (curve out), the center of the force is going to move outside of the outer bearing. Now the outer bearing carries most of the load and the inner bearing becomes a cantilever to the outside. How much force this applies will be dependent on how much curve there is to the rim. The vertical loading is going to be the same because the tractor weighs the same. But the leverage will change how the load is carried.

This makes no sense. You state that the rim is centered with the hub but if you flip the tire around it puts more stress on the bearing. If it is centered, flipping it would do nothing. In fact the rim is not centered on the hub but is dished to one side so that when installed in one direction the bolt hub is almost flush with the edge of the rim, therefore flipping it would put opposite but equal on the bearings. This is true for welded or adjustable bolted on hubs. The center is dished to one side. I agree with the OP(CobyRupert) in that the same amount of strain is on the bearings just in opposite direction. What does change is the steering stresses since the tires are wider apart, it puts more strain on the steering arms to turn.

The only way it would put more strain on the bearings is if one side of the bearings is smaller than the other, IE inner bearing is smaller than outer or vice versa. If this is the case then it would put significantly more strain on the smaller bearing when the wheels are reversed.
When I reversed the rims on my Yanmar 4220, it significantly increased the steering load making it harder to turn when setting still but I never had any bearing or load issues by so doing. I like the have the front and rear tires the same width because it is easier to judge where the rear tires will track and also the mower which is the same width as the tractor stance. This is especially handy when mowing tightly between obstacles, if you can get the front tires between, you know the rear and the implement will also fit.

 

[Sodo]

Consider using wheels with a dish of 10 feet (the tractor is 25 feet wide). The bearings would fail almost immediately. The answer is "Yes", widening increases the stress, thus shortens the life of the bearings if the tractor is used at max capacity.

It all depends what you do with the tractor. If you are widening the axle but never putting the rated load on this widened axle, you will have no problems. For example if the bearings are sized to carry 800 lbs in the FEL but you only use the tractor for mowing, then don't worry there will be NO effect whatsoever.

I would look at it this way: If you widen the axle 5% you should reduce the max loading by 5%. If you must travel far with a load in the FEL then carry a little smaller load.

With a widened axle the bearings will have a shorter life at full load capacity.
If loading on the widened axle is less than the rated load, your tractor won't notice anything.
If your tractor doesn't do the work you need to do, you are wasting productivity.

 

[CobyRupert]

Yes, if your widening the actual axle, which I seem to remember you could do this with on 2wd farm tractors, then you would have a longer "beam" which would be weaker. But that's not what I was referring to.
The point Gary and I are arguing is that if you're just swapping (reversing) the way the rim "dishes" (curves) then you have the same stresses. In your 10' dish (offset) example: the dish (offset) is what causes torque on the bearing. It still is exerting a equal torque on the bearing whether you have it turned in or out (assuming it could fit both ways in this exagerated example), just in the opposite direction.

 

[Tx Jim]

Widening frt wheels increases stress on everything involved with frt axle especially the brgs/

 

[Sodo]

Cory you are correct with this hypothesis and there would considerations with regard to inner and outer bearings is not same, if the dish was reversed.

Tx Jim yes it increases the stress but this is just a number related to usage. It's probably tied to the max weight of the FEL bucket, WHILE traveling at the max ground speed in the top gear. Maybe travelling slower when the bucket is full, is the only change that is necessary. Or carrying a little less.

The person making this stance change should consider whether the tractor is being used at max rated capacity. If the bearing is not used at the rated capacity, then worrying about the bearings from such a small change, is not worth worrying. OP should do what he needs to do, to get productivity from the tractor.

 

[slowzuki]

Yes moving the tire so the centre line of the bearings isn't on the centre patch of the tire increases the stress on the bearings. Not sure why people don't get this. Take a chunk of pipe and hang 100 lbs right where you are holding it, pick it up. Next slide the weight out 12 inches and try to pick it up, still holding the pipe on one end. Slide it out to 24 inches and repeat, probably won't be able to.

 

[CobyRupert]

Yes moving the tire so the centre line of the bearings isn't on the centre patch of the tire increases the stress on the bearings.

Yes, but when you reverse (or swap) the tires to make a wider stance the distance between the center lines hasn't changed, it just the center line of the tire has moved from one side of the bearing's center line to the other. The offest distance is the same in both cases. Same distance = same torque on bearings.