Originally Posted by fudge_brownie
I checked the spare and it is a 205 width. Does 3 out of 5 being 205 width mean that was what was standard?
Neither one is the published Escape standard of ST205/75R15. There were smaller sizes earlier (on smaller models), and at one point the 5.0 had larger tires (ST215/75R15) because it had the highest axle load, but I've never heard of a 225 mm width (the ST225/75R15) or 85 aspect ratio (ST205/85R15) used on an Escape. Of course, I'm only going on published specs, sizes mentioned in forum discussions, and the ones I've seen.
ST225/75R15 is a readily available size, just not normally used by Escape.
ST205/85R15 is an unusual size. The only ST tires commonly found in 85 aspect ratio are for 16" wheels. I don't know where I would even find a 205/85R15, ST or otherwise. Carlisle (Escape's current tire supplier) doesn't even list this size in their catalog
Tire size isn't discussed very often in this forum, compared to other forums, because the stock Escape size works fine and is readily available; most people don't find a reason to consider other sizes.
Originally Posted by Iowa Dave
The only thing that would concern me and I'm not sure it even should is whether or not the roll out on the two different width tires is the same. Should be Very close. Roll out used to be critical side to side when we raced stock cars with locked rear ends but on free spinning axles I'm not sure it matters.
"Roll out" is effective tire circumference, measured by how far the tire rolls (while carrying load) per rotation of the tire. It depends significantly on load and inflation pressure. Major tire manufacturers publish loaded radius and tire revolutions per kilometre (or mile) for this purpose, but for Special Trailer tires there usually are only more basic specifications provided.
With idler (free spinning, no drive shaft) wheels this doesn't matter, but it would still be a concern if the diameter were significantly different, as the trailer wouldn't even sit level. These two sizes are very close to identical - the 205/85R15 are nominally 5 mm larger in diameter, but tread depth differences could easily be larger than that. The slight difference probably makes much more different to the fit of the chocks than to the behaviour of the trailer.
I would be more concerned about significantly different width, causing a different amount of drag and different response to lateral loads. It could easily cause a greater tendency to sway.
At least they're all radials. I rented a U-Haul trailer once and found that it had three bias-ply tires and one radial.