Here's the dilemma. I am 6' 3", inseam around 34-35. I ride a 58 cm road bike. I'm looking to buy my first tt bike. Without mentioning the bike brand or shop by name, I went to a bike shop a couple of towns away. I had communicated by email before arriving. I was told through email that because I rode a 58 road bike, I would probably ride a 58 tt bike. But it's possible a 56 would fit.

Upon arrival at the store, the owner/fitter took one look at me and said it would for sure have to be a 58. But there was no 58 in stock, so I was put on a 56. After seeing the "perfect" fit, with a real good aero position on the 56, with lots of room to adjust even bigger if necessary. So, after being on the 56, I was told to definitely get the 56.

My understanding of the benefits of buying smaller are as follows:
1) the bike being smaller, it's significantly more aero;
2) the bike being smaller, it weighs less.

Mentally I am struggling with the idea of buying a bike that small (for me). I would really appreciate some thoughts on this issue. It is a major purchase decision, and when I spend the cash on the bike, it will take a long time to save up to correct a mistake of buyin the wrong size!

Any opinions will be greatly appreciated.

Zoren

Zorenzee,
I have a similar challenge to you. I am just over 6' 3" and have three 58cm frames, two 59s, and two 60s. It's easy to play around with your position on bikes these days because swapping stems and getting hold of really long seat posts (like a Thomson for example) don't present the same problems as they used to. That said, I am starting to move away from the smaller frames towards the larger ones because of the slightly longer top tube. I don't feel the difference that much in training ( I ride a lot on the tops when training), but when racing and spending a lot of time on the hoods and drops I feel more comfortable with the extra length.
I guess what you need to decide is whether the 56cm has a long enough top tube to really allow you to stretch out and get aero. Also, a slightly larger frame will allow you to get rid of unwanted headset spacers, which may be a problem with a shorter head tube. Finally, I presume you'd want to hold onto the TT frame for a couple of years. Don't assume that you will be able to maintain your flexibility indefinitely. If you're in your mid-twenties then perhaps that won't be a problem, but if you're the wrong side of thirty then flexibility may become an issue. Personally I would go for the slightly larger frame.
Finally, the aero and weight differences between a 56 and a 58 cm frame are negligible.

My experience: I ride a 57cm top tube Road Bike with a 110mm stem, my Time Trial bike has a 55.5cm TT and I use a 90mm stem. Both my bikes were fitted by Fl Bicycle Sports in St. Pete and I'm very comfortable on both. I think most people find a slightly smaller top tube on a dedicated Time Trial bike to work just fine.

Thank you to the 2 users that posted. Your thoughts are both very useful and will be used in the decision.

I will still monitor this thread, so if anyone else has any experience, please share.

One last note: the 56 cm tt bike that I was on had two circles for mounting the seat. The seat was in the foremost circle, thus giving room to move it back considerably. But even on the front, it seemed like it fit just right. I was also told that the 56 would have more drop (the diff in the seat level from the handle bar level) than the 58, which would result in a more aero position. I am on the wrong side of 30, but I have been spending huge amounts of time during my training rides in my aero bars, and am really feeling comfortable in that position.

Zoren

It is common to ride a TT bike that is a size or two smaller than your road bike. My road bike has a 55.6 top tube. I like a 54 top tube TT bike. I could even do a 53 with a 110 stem. Go to www.bikesportmichigan.com to see some good pictures of TT bike fits. For a more detailed discussion check out www.slowtwitch.com. Dan Empfield, John Cobb and others post there from time to time. If you are bold, you could post a side picture of yourself on the TT bike and get some fit recommendations (on slowtwitch). Some will be very helpful from some of the most knowledgeable fitters in the US and some will be smartass comments.

Which TT bike are you looking at? Are you buying this for triathlons or TTs?

Mike

Sounds like you may be looking at a Kestrel Talon, but I think there are other makes with a similar seatpost design My TT bike is a Talon SL and has a two position seat post as well. I ride it in the forward position and like the position it gives relative to the BB. BTW, I'm 54 so you have a long time before lack of flexibility should become a major issue.

Thanks for the reply, mprevost. OK, I'll spill the beans. I'm 40 years old and looking at a P3 carbon. I just read the Dan Empfield article. I guess it all comes down to how steep you want to be, and how long you can hold the position. It doesn't make sense to go 81 degrees and then only be able to stay there half of the time.

I participate in a weekly tt series, and I did one olympic sized triathlon this past summer, with plans to do about 4 of them next year. So the bike is for both tt and triathlons. I do as much of my commute as safely possible in my aero bars, and I would say that by now, I feel as comfortable there as any other position.

I have another few weeks to make the final decision, but I am now leaning towards the 56.