Safe minimum dual tire clearance?
As I am beginning to think about new tires for my drive axle over the winter, and the fact that I think if you ask 5 different tire shops you'll get a combination of 12 different incorrect answers and old wives' tales ... I figured I'd ask here.
My coach was originally delivered with 255/80R22.5's all the way around. There is a notation in the manuals that back in 2001 the factory swapped the tires to 275/70R22.5's on the steer and 265/75R22.5" on the drive axle. I believe this was done because the coach, as delivered, was tire-limited as far as axle weights -- certainly, as I have it loaded (which is not stuffed) it would be slightly over the ratings for the 255's on the front.
Now, as built, the coach actually has a 19,000 pound rear axle and a 12,000 pound front end, so bumping to the bigger tires didn't impact the safety of the coach itself. And I've been through the coach, underneath, etc., and see nothing negative, so to be honest, I'm not worried.
...so getting back to the point of the thread... I would like to put 275/70R22.5's on the drive axle because there seems to be a MUCH better tire selection in that size. And the diameter should be the same, so no worries there... but of course, I will be narrowing the gap between the duals by 20mm (almost an inch). There seems to be a bunch of clearance between them now (far more than my old 16" tires on my gas motorhome) but I have no idea what the standard for "safe" is.
The Green Machine -- 2000 Mountain High Coachworks Summit (Spartan chassis / Cummins ISC)
...and F-Troop: Fearghus, Fiona, and Frankie (Cairn Terriers)