Road Cycling - Cycling 8 miles to gym practical?

I found a really nice gymnasium in my area. Unfortunately, its about 30 miles away and I have no motor transportation. I am thinking about taking the subway which will cut the distance to about 8-9 miles. Is it practical for me to petal 8 miles on my shimano mountain bike? I'm not sure of the terrain, hopefully it won't have too many hills. I need some advice from experienced cyclers.

Why go to the gym? Cycling is great for weight loss, cardo fitness, and leg and core strength.

I go to the gym to play squash.

This is for gymnastics. I want to learn how to do a flip without busting my head and some other stuff :)

Hell, ya, it's practical!

Not clear what you are asking. Are you asking because you think 8 miles on a mtn. bike could be too difficult, or are you asking if 8 miles would be too easy to be worth the trouble?

I would lean toward the latter. Get some slick tires and ride the full 30 miles to get a really good workout. If that's too much, then you could start by riding the 8 miles, then get off the subway one-stop-further each week. Or, ride 30 to the gym and only 8 back. I think a bike is a very practical mode of transportation :D

Not clear what you are asking. Are you asking because you think 8 miles on a mtn. bike could be too difficult, or are you asking if 8 miles would be too easy to be worth the trouble?

I would lean toward the latter. Get some slick tires and ride the full 30 miles to get a really good workout. If that's too much, then you could start by riding the 8 miles, then get off the subway one-stop-further each week. Or, ride 30 to the gym and only 8 back. I think a bike is a very practical mode of transportation :D

30 miles one way. 60 miles is a lot for a haul to the gym. The 8 miles one way is perfect though. It will give your body a chance to warm up. Once you are there your heart rate will be up and you don't have to spend some time on a trainer.

8 miles with slick tyres should take 30-40mins depending on how athletic you are, and how hard you want to ride. Even if you cruise, you will still be warmed up.
I ride that distance to work, with no special clothing.

I used to ride MTB 7 miles to gym and it was just fine. I'd say if you wanted to ride 30 take the advice that others mentioned and get city slick tires rather than the knobbies.

I ride to the gym. Only 2 miles each way. Some times I take an alternate route and Its 5 miles each way. I also ride it on a MTB with slicks. Even the two mile trip can be a good workout, just stay in a lower gear and pedal like mad. The trick is to stay in a gear where, eventhough your pedaling fast you can still feel the road's resistance. It's not great for strength but get the right heart rate going and it's great for cardio, weight loss, or just getting that massive pump in your legs so you walk funny when you get off the bike.

BTW I go to the gym to lift weights...

8 miles is a practical distance for a good warm-up. Slick tires is also agood idea. Be careful though. I did that to my bike and ended up getting an incurable case of road bike craving which was only partially satisfied by the purchase of a Giant OCR 1.