Since the front axle is on a pivot, widening the front has no effect until the axle pivots all the way to the stop. If that happens on a hillside, you are probably going over no matter. And rear axles are built much bigger than the front axles, so I think it is wise to not widen the front. I've seen guys reverse rims and on some models that widens the front, but you still have the pivot issue so I don't see how that helps much.
Hey Dave,
Thanks for chiming in. You have made two strong points. And I will post before and after pictures as requested. I'll also comment on what I've learned about corrosion control when installing spacers in a future post.
My dealer mentioned the pivoting front axle as well, in the context of diminishing returns for the amount of stability gained, the loss of warranty coverage, and the cost of quality spacers. I agree it is not worth the stability gained while the front axle is under warranty - and probably will never be worth it since the tractor manufacturers (my dealer said Kubota came out with a bulletin about not widening front wheel track several years ago and Kioti has it in the manual) see it as a likely axle failure modification. It all depends on usage too since some front axles that people widened have failed and others haven't. My dealer pointed out that with a four wheel drive tractor a widened track will cause more flexing of the axle, which he thought during strenuous use (lifting, but also digging hard against something with the FEL) might allow the front axle drive gear teeth to slightly pull apart so the teeth tips are meshing rather than the entire "tooth". That might cause one to break and, depending where it fell, could wreak havoc inside the gear box. That made sense to me, but whatever the mechanism of failure that is exacerbated by widening the wheels on a four wheel drive tractor, it seems to be a fact that this happens more often with widened wheels than not.
But for purposes of discussion, while I agree widening the front would not help stability until that axle pivot point is reached, I suspect it actually would help prevent a rollover. All our tractors have somewhat different CG's in the vertical (distance of the CG from the ground) because some have loaded tires (lowers the CG), some have FEL's (raises the CG when an empty bucket is more than a foot or two off the ground since the arms are always above the non-FEL equipped tractor CG), the PTO implements can affect it, the ROP up or down affects it, our body weight high in the seat affects it, probably even a sunshade and for sure a cab raises it. My gas tank looks to be higher than the CG so a full tank probably raises the CG.
The sideways rollover happens when the CG's vertical plumb line gets outside the width of the tractor's wheels. This static tip over angle, even with a cab, has got to be greater than 30 degrees. It gets higher the wider the tire track - and the lower the CG. If we jacked our tractors up on a flat surface and kept jacking until they tipped over it might even be closer to 40 or 45 degrees. That front axle pivots how far? Does anyone know? I'm guessing 20-25 degrees? If it is less than the tipping angle then from that front axle pivot stop angle widening the front wheels would begin to assist in preventing the sideways rollover.
But a moving, especially while turning tractor, encountering bumps on the high side and depressions on the low side, can see their tractor's CG angle abruptly move outside the wheel width. This dynamic movement of CG as it hovers around inside the safe tread width is what surprises folks. I'm a pilot and safe loading of aircraft is critical so the CG is always within the ability of the ailerons and horizontal stabilizer to control the attitude of the plane at all flying speeds. With certain passenger and fuel loads we put sandbags in the forward cargo compartment to move the CG forward. I guess my piloting experience has made me as interested in this rollover subject as I've found myself *grin*. That and the HILLS on my property, which no matter how wide I space my wheels will never be safe to drive completely sideways across. I think they are right up there at 35-40 degrees in some spots, but that might be my imagination at work seeing me roll over and over and over...into the pond at the bottom.
It is helpful to me to imagine "safety" as a constantly forming and decaying, swirling like a tornado, vertical column of water inside a clear plastic tube. The water never can reach the top of the tube, which is absolute safety (heck, an asteroid could come streaking down and hit us on the head). If the water lowers until it gets to the bottom of the tube disaster strikes (however you define it - any rollover being a pretty big disaster even with a ROP and safety belt). So at any given moment the water level is somewhere in the tube as we work our tractors, drive our cars, fly planes (or cut vegetables in the kitchen) - dynamically going up and down with every little thing that happens and every little decision we make as operators. Every little distraction, every bump in the road moves the water down a bit, and then it moves back up as we get back on smooth ground or refocus on the operation.
Widening the wheels moves the baseline water level up, but with regard to the front wheels as you point out, not so much!
Best,
Rhino