Mtb tires on road rim

It sounds like you're asking if you can put a mountain bike tire directly over the wheel + tire of a road bike.

(please correct me if I am wrong)

There are a few things to account for.

1. It is not very safe to put a tire over another tire, as most tires are slick and the inner tire may not gain traction on the inner tire.

2. It is not likely that the mountain bike tire will even fit over the road bike tire, as even the largest mtb tire will most likely not fit over even the smallest road bike tire size.

In the end, it seems that doing this is not possible and even if it worked, it would still be unsafe.

Edit - It seems I have missintepreted the question. with the diameter and width of mountain bike tires, it is practicaly impossible to fit even a 29er on a road wheel, not because of the diamter, but instead the thickness of it.

Assuming the new rim is about the same width as the bent one, then the tyre and tube should transfer over okay.

You need to check the valve hole in the rim - there are two common sizes, and the wrong one won't fit or risks punctures at the base of the valve.

I suggest you fit the tyre, and inflate it to a relatively high pressure, whatever's maximum on the sidewall. Then leave it overnight and check again in the morning. If it holds air and hasn't blown off the rim then deflate a little to riding pressure, and go for a test ride