This might sound a bit crazy, but I'm trying to create additional wheel drag on a road bike to make my commute bike rides more of a workout. I live in a flat area with lots of great bike trails but can't go too fast because of joggers and other cyclists. I know this is what indoor bike trainers are for but frankly I commute to work on a bike and it's really the only time I have in the day to exercise. Unfortunately, the fact that I can't ride fast on the trails really limits how much exercise I can get. I've thought about different ways to make my rides more difficult and the best seems to be to create additional drag on my wheel(s) similar to how spinning bikes work. I guess the problem is that adjusting the brake pads so that they rub against the rim will heat up the rim possibly causing a tire puncture. I thought about going with heavier wider tires and decreasing in tire pressure but wanted to see if there are other ideas before I invest in new tires. I also thought about switching to a mountain bike but would rather not spend the money on buying one (I also don't the have the room for 2 bikes at my place).
Does anyone know of anyway to create adjustable wheel drag on a road bike without possibly doing damage to the rims? Maybe installing a disk brake in the rear and somehow using felt pads to create resistance?