[Bill]

Originally Posted by RockyMtnRay

I've already discussed this with the owner of a local tire shop ... he hasn't yet retrofitted his trailer's tires either. One thing he did mention during our initial discussion is that you may not want to run the larger tires at their maxiumum 65 psi pressure, but rather at one that provides a sufficient margin of load capacity. If running at max pressure, there's a good chance you'll get excessive wear in the center of the tire so he suggested getting some tire chalk and using that to determine if there was too much air in the tires.

Reduced inflation would also give the TM a softer ride - or at least not a harder one. I haven't tried it, but I would be afraid that at 65 psi, those rock-hard tires would pound the TM to death, despite the "give" in the axle.

There are two likely points where an oversize tire would rub...at the very top and the sides.

I think that the first part - contact at the top - should be easy to deal with. When I thought about doing this, I climbed into the kitchen cabinets, and noted that there is nothing special going on. The wheel well liners are a simple piece of molded plastic screwed to the floor around the tire opening. I would simply unscrew each one from the floor, build up a lip or rim around the opening out of 1x2 pine, and screw the liner back down on top of the lip.

I was much more concerned about fore-and-aft clearance, and so I never carried through on this project. However, if TM would send you a pair of larger wheel well liners (I never thought to ask), I have to believe it wouldn't be too hard to slightly enlarge the opening in the floor.

In-and-out clearance (in the direction of the axle) would also be of concern, but I don't think that 15" tires are necessarily much fatter than 14" tires.

From everything I've read, the stopping power of trailers with hydraulic disc brakes is enormously better than with the traditional electromagnetic drum brakes (like a factor of 4 in the deceleration rate).

Hmm, in this case, my skepticism is nearly boundless. If the electric brakes will grab tight enough to lock up the wheel, then hydraulic brakes aren't going to do any better. In practice, both of them should be adjusted to the point where they won't quite lock up in a panic stop - but still, I don't see that hydraulics have any inherent advantage. Of course, a larger tire might possibly enhance deceleration, simply because it puts a larger rubber patch on the road. But for equal tire pressures, even this is pretty iffy (which is why your tire guy suggested the chalk test). But in the end, any claim of deceleration improvement of 4 to 1 is pure bogus hokum unless someone can a) explain how the difference makes it better, and b) provide reasonably scientific measured data. If you actually find some of this, I hope you'll pass it on.

Just my thoughts - I am interested in this topic because like you, I think I often run pretty close to the tire limits. There are also a couple of associated technical issues that I will discuss offline with you - I don't think they're of general interest to the group, and this post, like many of mine, is already too long.

Bill