the difference between a tri bike and cross bike during a tri will be pretty damn significant. Even the difference from a road bike to a tri bike would be very significant. The only problem is, you cant always train on a tri bike because it can get uncomfortable (especially for long rides). I might recommend keeping the cross bike for training and getting a beginners tri bike for the races. If you are a noob to this sport and dont know if your gonna like it i might stick with the cross bike for at least your first season of racing. In your first season, you shouldnt be too worried about doing really well (unless your already in great shape). Finishing the race should be your main priority, but if you find some cash lying around (roughly $2000), you could probably pick up a beginners tri bike for your races.

Also, i think the angle of the seat post releases a little bit of tension off of the quadriceps to help your running-specific muscles feel more fresh for the run.

Keep the CX bike, especially if you enjoy 'cross. Get some nice tires and a set of shorty clipon aerobars. The biggest thing is reducing your frontal area, which the shorty bars will do for you.

stupid question.
what is a cross bike?

[quote=SerialKiller]stupid question.
what is a cross bike?[/quote]

Cyclocross. It's essentially a road bike with mountain v brakes and fatter, knobby tires.

To OP: Don't bother trading in/selling the CX bike. Just get some road slicks and tubes for the wheels you currently have, flip your stem or move it below some spacers (if you have them) to give you a lower front end, move your saddle forward, and get some clip-on aerobars. It'll cost you no more than a couple hundred for the new gear. Won't be the lightest bike in the race, but if you ride cross, you're probably sick enough in the head to get away with it.

[quote=xc800runner]. . . but if you ride cross, you're probably sick enough in the head to get away with it.[/quote]'Cross looks pretty sweet. I think a 'cross tri would be awesome: river swim, 'cross-type ride, trail run.

[quote=Gsal]The only problem is, you cant always train on a tri bike because it can get uncomfortable (especially for long rides).[/quote]

I would suggest you get refitted. I used to have that attitude, now after adjusting my position I am more aero, but mnore comfortable. Managed 2 hours on the bars last Friday, without the usual numbness and uncomfortable feeling.

[quote=NotAsFast] I used to have that attitude, now after adjusting my position I am more aero, but mnore comfortable. Managed 2 hours on the bars last Friday, without the usual numbness and uncomfortable feeling.
[/quote]

My tri bike can be ridden for 5 hours without a problem, but when it gets very hilly, when i ride with my slow friends, or I am in a higher traffic area, its not the best bike to be on. My roadie is great for those situations.

Many CX bikes have seat angles of 74 degrees or more, compared to traditional road bike geometry, which is around 72 degrees. This is great for triathlon. While the headtube maybe a little taller, just take a spacer or two out if there are any left to get your bars a little lower. combine that with some shortie aerobars, and youve got a decent newbie tri bike. I'd definitely keep the Cx bike.

I was thinking about throwing some bars on my CX bike too. Its the only non-mountain bike I have and has been my ride for the past few summers for all of my tris. Planning on doing the Jerseyman Half in May and really think that aero bars of some kind are a must. Maybe really short ones that are draft legal? Any more thoughts out there? Thanks in advance.

Unless you intend to be in the top 10 percent in your first year... A modified CX bike can do it.

I was within 5min of the top bike split in the paris Ti last year. With a aluminium road bike, with shimano 550 wheels and Sora crank and no clip ons.
Frankly I could have pushed more and I lost time finding the entry to the transition.

So I could have had the top bike split with a very normal bike. So much for 5000 euros bikes!

I am personally going the other way, [url=http://brokeniron.blogspot.com/2009/01/choosing-new-alloy-horsey.html/]and getting a CX bike for going to work and training purposes[/url] .

I think you will be better served spending less on the bike and more on training (swim club, run club etc) and going to competitions (travel and entering can get expensive). And quite frankly, it's better to wait until you know what you need, rather than being told what others want.

[quote=gildasd]I am personally going the other way, [url=http://brokeniron.blogspot.com/2009/01/choosing-new-alloy-horsey.html]and getting a CX bike for going to work and training purposes[/url] .[/quote]

Fixed link...

Thanks!

[quote=TriSooner][quote=xc800runner]. . . but if you ride cross, you're probably sick enough in the head to get away with it.[/quote]'Cross looks pretty sweet. I think a 'cross tri would be awesome: river swim, 'cross-type ride, trail run.
[/quote]
XTERRA maybe? ;-)