I am in the process of purchasing a new bike. Local bike shop is having a great sale. I am currently ride a Softride Rocet TT. And I just don't like it. I have broken it once and the beam is alway working loose. Before that I had a Lightspeed Tachyon. So for the last 5 years I have ridden only a time trial/tri bike. My Softride is a medium and my Lightspeed is a 53 cm.

So I am training for an ironman and I decided I need a road bike to do most of my training miles on. I am actually thinking of just moving the seat forward and putting on some Syntace clip-ons and using it for racing as well. So I go to look yesterday and instead of getting measured and fitted (which I have done in the past) I decide I am just going to try a couple of sizes and see which one fits the best.

I start with a 54 cm and it is way too small. I ride a 56cm and it is too small as well. ( when I rode it I felt like I was over the front wheel, and it had a 120 stem on it). Then I ride a 58 cm and it felt good. Very comfortable, very balance and very smooth. But here is the kicker.. I am 5'10 with a 29.5 inseam. My torso is very long. I think that may be why it was so comfortable. I could still pick up the bike standing over it, and the wheels were about 1.5 inches off the ground.

I am looking at Treks.

My question is this. Is it conceivable that I would ride a 58 cm road bike and a 53cm tri bike? I just want to make sure before I purchase a bike.

Any info would be greatly appreciated.

Thanks...