LT235/85R16s

I don't think they will fit. Some people have used 245/75/16 (30.47) and they just fit with modification to the rear fender wells.
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h2ocamper said:

Really, the rear is an issue? Typically, its the front area that's an issue for larger tires.

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Do you have a Promaster? Go out and see how much clearance there is in front and behind the rear tires.

83Grumman said:

Do you have a Promaster? Go out and see how much clearance there is in front and behind the rear tires.

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I don't yet (its on order) or I would do just that. No dealers near me have any new or used either. I guess I could detain the Amazon driver next time they're here. Or maybe you could measure?

If you search 245/75 on this forum you will find a lot of info on fit issues on the rear with the increase in diameter. Going with a 235/85 will even have greater issues with fit on the rear and maybe even the front (245/75's seem to have no front issues).

That would be a little hard to do on a new vehicle but definitely could help the situation.

From accounts on forums, Youtube, etc., it appears the path of trying to convert a Promaster into an off-road Sprinter or Transit variant is long, circuitous, expensive, problematic, and can be unsatisfying.

The bone stock Promaster, when driven with a front-wheel-drive mind set, can be suprisingly capable off road. It just has to be driven slowly and with care (and an occasional traction aid). If an obstacle proves to be too much for it, most bolt-on modifications won't help all that much anyway.

Especially if most of your miles will be highway miles, it might be a good plan to spend all the money on a top notch conversion, and then drive as much as you can for a while. Then bolt on modifications as needed. Besides, that way you'll know things like weight, weight distribution, and also exactly what improvement you want most.

The Book of MOPAR says 5% variation is acceptable from stock size - the 245 defenders calculate to 4.2% increase and I've run a set now 70k miles, there was some scrub on the OEM mudflaps up front near full turn angle with zero damage and the rear axle with its huge weight load capacity simply goes up and down so a tight fit does not interfere.

With a taller sidewall inflation pressure would be higher to keep a 'jello' side-to-side wiggle from being a nuisance - I found the narrow stock steel rims and the fatter Michelins 245's will let chassis quiver at stock pressures.

I'm interested in 235's - a favorite rural snow allowance to keep footprints narrow but help reduce plowing snow vs riding above it....