I am looking at Vision Tech Trimax Integrated aero bars. They come in four lengths:

• 90/230=320
• 90/250=340
• 90/270=360
• 100/290=390

This may be incredibly obvious and I'm really stupid, but how do I determine which length I need? I assume I measure my forearm length, but I can't find a chart anywhere that tells me what measurement to take. Elbow to wrist? Elbow to someplace in the hand? There's no chart anywhere on the VT website or any of the PDFs.

The size depends somewhat on exactly how you ride on the bars. With your hands gripping the end of the bar will you ride with your elbows in the rests, just behind the rests or even farther behind than that. If you research the web on TT bike or Tri bike aero positions you will find some guidelines on the proper position of the body on the bike. Deciding on where your going to put your forearms on the arm rests (depending on frame size, stem length, saddle to bar drop and your ability to ride in the TT position as in how low can you go and still make power and control the bike) will determine which bar length is appropriate.

Hmm... that's a bit more complex than I thought. My plan was to order the bars, then have a friend with lots of TT experience help set me up and get fitted. I have a borrowed TT bike right now and could make some educated guesses, but it sounds like I'm putting the cart before the horse. Perhaps I would be better off going for a pro fit and ordering bars based on that. That'll cost more but I want to get it right. And I suppose getting it wrong could be far more costly in the long run.

Fitting a TT bike for serious riding is a bit different than sizing a frame. The professional fit is well worth the money. It's still possible that you will end up with more than one size of extensions as your ""TT fit" will change as the season goes on. In the Vision system, not only do you need the right length aero extensions, but you need the optional mounting kit for the arm rests. There are wing shaped mounts of 12.5 and 25mm to set different heights.

If you do it on your own, you will end up with a large selections of extensions, stems etc.......... I know.

You mean like the Ironman and 100 mile Time Trials (Calvin's Challenge) I am doing this year? CC is only 2 weeks away and I'll be riding my standard road bike, but by this time next year I'll be riding aero.

Thanks for the advice. I'll schedule a fitting. At those distances, comfort has to be considered, not just optimizing power and aerodynamics. No point in averaging 25mph in an Ironman if you can't run when you get off the bike. At Florida last year I saw a lot of newbies gain 20-30 minutes riding their brand spankin' new TT bikes; only to lose an hour or two by walking half of the marathon when their bodies gave in. Didn't make much sense to me.

Try slowtwitch.com and trinewbies.com for some excellent articles. You will find a full range of information on tri bikes, how and why they work in relation to your muscles (ie why a good tri bike will not kill your running). You might also try the book Zin and the art of Triathlon Bikes. Go on down to the Tri Forum and get more of your questions answered.

One quick bit of help for your standard road bike.......You can add a short set of aero bars right on to your road bars. They may help a bit on long straights. Your controls will still be on the drop bar so the extensions will no work as well as a true tri bike but they will save you a few seconds. Keep them short though, (you don't want to reach out much farther than the hoods) something like Profile Designs Jammin GT's. Unfortunately you do not have a lot of time to become use to the way the bike will handle but it may help.

If it's not too hot, you might use a helmet cover and shoe covers to gain a little aero.

Read everything you can find about TT bike design. The web has a wealth of sources for the sport. Good luck.


Edit: Your remark about comfort is very important. It is useless to set up an aero position that you cannot maintain. The trick is to find out how far you can go and still keep it all together. Some of the sites I mentioned will help to explain this.

I've actually got a lot of time.. Ironman Florida isn't until November. I'm probably going to convert one of my road bikes and go fully integrated. I can't use clipons with my current bars (oversize/carbon) so I'd have to invest in new drop bars and rebuild the whole thing anyway.

helmet/shoe covers - yep. I'll have them with me but it will depend entirely on the weather down there. Last year was unseasonably cool when my sister did hers, and would have been perfect. It'll probably be 90 this year for mine.

You may want to check that. While my base bar is a Profile Design unit (Cobra Wing) it's both carbon and oversize and takes clip-on's just fine.

I also recommend a professional fit. Aerobar fitting gets a bit more complicated and you may not necessarily use the length based strictly on your body measurements. As an example, I bought my tri-frame bare and built it up myself. I bought a pair of medium clip-ons based on my height. Once the bike was all built up the aero position was great but one problem I had was hitting my knees on the back of the arm rests when standing on a climb (I have long legs and short torso). So to alleviate that I got a stem that was 2cm longer. But this pulled me too far forward when I was in the aero position. So I got small clip-on aerobars to put me back on the center of the saddle.

Profile Design's Cobra is designed and approved for Aero Clip Ons, a lot of carbon drop bars aren't. Usually, a bar that is approved for aero bars will have a special note in the specs. The clamping action on the aero bars must be very high to be sure that they don't move, too high for most carbon bars to withstand.