Got a strange problem with my 30" snapper (23 series), 12.5HP rear engine riding mower (about 5 yrs old).

I finished mowing my yard after about an hour with no apparent problems, (and I parked the mower in front of my garage with the Brake engaged) and all of a sudden I smell burned rubber and see an enormous amount of smoke coming from under the rear area of the mower.

I checked the pulley belt and it looked OK, but appeared to be twisted over on the pulley that drives the blade. I flipped over the belt and the problem still persists. No visible wear on the pulley belt. and the belt didn't appear to get hot. No unusual noises.

Raised the mower on end and checked underneath. The drive tire that engages the drive disc looks OK.

Restarted the mower (with brake engaged) and more smoke (a lot of smoke) and odor of burning rubber coming from underneath the mower. Disengaged the brake and drove the mower around the yard with no problems. When I stop the mower and engage the brake, the smoke reappears.

Any ideas??? Any help will be much appreciated.