new - looking for input

Having a good base going into your training is always a good idea, you'll be able to start off strong with your tri specific training in May.  Look at the training plan here for an idea of what to expect.

Working on your swimming in the off-season is a good idea.  Working on drills to improve your breathing and your stroke would be something to focus on.  Then building up the yardage a bit.  Might want to see if there is a masters program in the area, they usually cater to a levels.

A stationary bike would work if you don't have a bike trainer.

Look at doing some core workouts as well, build up some strength in those muscles. 

My concern here is with your bike, you said it's a mountain bike.  How heavy is it, does it have knobby tires or flats.  I would rather see you on a hybrid bike or road bike especially for 56 miles.  Don't get me wrong, it can be done and you can do that, but you would be using more energy than normal.

56 miles?!?  Sorry, I think I confused things when I mentioned my half in April.  It's a half marathon, not a HIM.  I don't know that I'd ever be ready for something like that.  The triathlon that I'm wanting to do in August is a sprint - only an 18 mile bike ride. 

My bike does have the fat tires and I don't know about the weight.  It's a 12 speed that I bought at Target several years ago just to ride along the Katy Trail.  I figured it would be OK just to get me through this first one and then I could decide from there what I wanted to do.

Thanks for the input!

I basically like your thinking but I'll offer 2-cents worth on the following.

Swimming...see if you can't get some instruction now.  And, until the instruction don't worry so much about swimming 300 yds. straight in order to know you can "make it" for the tri.  For now, concentrate on gliding, breathing to the side without picking up your head, keeping feet up vs. letting them sink, etc.  for 50 yds. at a crack.  Swimming is like golf...the more you do it wrong the more you ingrain the bad habits, so try to get some quality lessons ASAP.

Biking...if you cant set your mountain bike on some kind of indoor trainer, maybe see if you can find a spin class to attend vs. just grinding on the generic exercise bikes at the gym.  Spin bikes can be set up to more closely mimic your position on a real bike.  Not ideal but better than the generic bikes.

Have fun!  You're basically on the right track for the winter, IMHO.

I did my first sprint in June of last year, and was planning on using a hybrid bike. Someone persuaded me to try their racing bike a few weeks before, and the difference was unbelievable. I bought a second hand entry level bike for $100 (plus another $200 to have it serviced and a few new parts at the bike shop) and I think it was well worth the investment. I think I saved at least five minutes (over a 12 mile course) by riding a racing bike. It also makes it more fun, as a racing bike requires much less effort. Trying to drag a hybrid/mountain bike up hills is not easy!!

As for the swimming, just try to increase your distance gradually. A lot of beginning triathletes despair with the swim, but in a sprint the swim is the least important part. I come from a swimming background, but am hopeless at cycling and running. The swim part of the sprint took me 13mins (for 750m), but then the bike took me 45mins and the run 30mins, so I was fairly near the back by the end. There were some hopeless swimmers, who took 20mins and more for the swim, but then they'd bike in, say, 35mins, and run in 22mins, and beat my by a mile.

You do have to be able to actually complete the swim in a reasonable time, but I think people from a cycling/running background generally make better triathletes than the swimmers. Just my opinion though.

I agree with morey1, your thinking is pretty good.

For the swim, it would really be a good idea for you to get some form instruction.  Kevin's (TriSwimCoach) DVD is really good and not too expensive.  Also, Total Immersion isn't bad and both are better than nothing at all.  The swim is what a lot of people dread and if you can make that easier on yourself so that you will enjoy the training and the race more, why not do it?

Bike - I wouldn't buy a new bike until you've done your first tri and decided that you like it.  I would, though, try to borrow a road bike from someone that is similar to you in size so that you can truly get a feel for what that would be like.  Using a mtn bike is fine and all, but it's just not the same thing.

Run - Sounds like you've got that covered.

Good luck and welcome!

Correct me if I'm wrong, but I read the part about your swim as saying that you do 300 yards of swimming per workout, is that correct?

If so, you're not going to build a base that way because you're not spending near enough time in the pool. I recommend increasing your yardage. That does not necessarily mean that you need to swim longer continuously, but your total workout should include much more yardage than just 300 yards. You can do sets of shorter distances if you can't sustain sets of 300s, but understand that the short you go distance-wise in your sets, the more your swims are focused on speed, not on endurance/base-building.

If I read that wrong and you were just saying that you swim sets of 300s in one workout, then I apologize for the misguided post .

If you're interested in increasing your base in the bike, you also should increase the time that you spend on the bike, preferrably on a real bike, but if you can't, try to get on a good stationary bike and increase the time that you're on it. It may not be perfect, but at least you're spinning!

One caveat, this is a very generalized response.

X2

this is exactly what I did and even though my MTB had slick tyres on I still knocked 10minutes off my 20k time from 52 to 42 in training ride before the race. 40mins on race day and it was hilly.

you might be lucky someone reading your post here might have one you can borrow if they live nearby.