Road Cycling - Q about building a TT bike

This is going to be hard to explain but I'll try. Here goes...

O.K. I just got my new road bike about a month ago, a Tommasini Fire. I absolutely love it!!! My old bike, a Lemond Buenos Aires, was just a bit stretched out for me and I am much more comfy on my new ride which has a 1 cm shorter top tube.

I was thinking about building a TT bike out of my Buenos Aires which is a bit stretched out for me but I thought that might be o.k. because of the more aero position of the TT bars. Would you get a shorter stem to create the same actual length from saddle to handlebar or do you think the extra 1 cm top tube will be o.k. since I will be going with aero bars. I have never ridden with aero bars and don't really know how to guage the position I will be in.

Also, on my new bike I went with 170 cranks instead of the 172.5 that are on my Lemond. I am much more efficient with my 170's and I don't want going back to the 172.5's to mess up my pedal stroke. Should I get new cranks or will it be o.k. to use the 172.5's on the TT bike and the 170's on my road bike.

I hope that made some sense. Thanks for any help you can throw my way.

quote "Also, on my new bike I went with 170 cranks instead of the 172.5 that are on my Lemond. I am much more efficient with my 170's and I don't want going back to the 172.5's to mess up my pedal stroke. Should I get new cranks or will it be o.k. to use the 172.5's on the TT bike and the 170's on my road bike."

Depends on your TT/flat riding style. I went from 172.5s to 175s, and am noticing I can spin a nice 100rpm on the flat, especially in a TT position (it's real hard to spin fast (over115rpm on 175s) and smooth on aerobars). I still ride mountainbike to school, and the gym bikes, and they both have 170s (BIIG diff) and I will also be having 165s on my track bike! I think the 170's will help your pedal smoothness, and the 172.5s will help you put the neccesary power to the ground for TTing. If i bought another bike for Road racing and left the cervelo for just TTing, I would go for 172.5's again on the new bike. But hey, just give it a go and see. You can easily swap it at a later point, rather than at the start and then changing it back. etc.

Brendon

I was thinking about building a TT bike out of my Buenos Aires which is a bit stretched out for me but I thought that might be o.k. because of the more aero position of the TT bars. Would you get a shorter stem to create the same actual length from saddle to handlebar or do you think the extra 1 cm top tube will be o.k. since I will be going with aero bars. I have never ridden with aero bars and don't really know how to guage the position I will be in.

A good TT position will stretch you out even further than you are already, if you want to see how bad it will be, hop on the old bike, and rest your arms on the top of the bars pretty close to your elbows. Granted you will be a few cm higher with arm pads, but it will get you a rough idea.

All is not lost, you can get a forward seat post like this - http://www.profile-design.com/product_pages/post_fast_forward.html which will move you forward on the bike. The shorter stem may or may not work as you may make the bike even more twitchy (aero bars aren't known for super-stability), something you will need to experiment with.

The good news is that it won't really cost a lot to try it out, the seat post will be around $50-60, cowhorns and aero bars should be under $150'ish, you could still use your STI levers for now (and if you like the setup sell them for some brake levers and bar end shifters...the STI setup will probably pay for quite a bit of the upgrades).

Andrew

EDIT: Oh yea, here's a good TT link, plenty of good info - http://www.timetrial.org/ (I've got a few more if you're interested)

Do you recommend any aero bars, again, I will only be using this bike for TTing.

Also, what do you think about the length issue? It is just 1 cm but I have found that moving things around even a few mm's can make a huge difference in my comfort on my road bike. I am sure it is the same for a TT bike. Visually I could imagine that the extra top tube length might help out because of the lower, more aero position that I would be in for TTing but I currently don't have any experience in that area.

Do you recommend any aero bars, again, I will only be using this bike for TTing.

It all depends on how much you want to spend and what your goals are. You can get a set of Profile Jammer GT's for under $80, read up on the Slam position - http://www.timetrial.org/slam.htm (talks about being aero on a traditional road bike)

Or you can pick up some bling-bling HED/Zipp aero bars for $400-500.

The difference between the two will be probably in the 1-2 minute range on a flat/windless 40k if you are in the 250 watt range (figure a mid/high 20mph avg speed).

Somewhere in the middle may be some cowhorns (figure around $30) and the aero bar of your choice, C2's from Syntace are nice (around $100).


Also, what do you think about the length issue? It is just 1 cm but I have found that moving things around even a few mm's can make a huge difference in my comfort on my road bike. I am sure it is the same for a TT bike. Visually I could imagine that the extra top tube length might help out because of the lower, more aero position that I would be in for TTing but I currently don't have any experience in that area.

There's a bunch of variables here. How flexible are you? How flexible are you in the hip/lower torso region, you want to sit flat on the saddle and flex as far down your body as possible. 1cm is probably workable, but it may not be(as you already said you were stretched out). A forward post, shorter bars could very well make everything work well together.

Check out http://www.slowtwitch.com/mainheadings/techctr/techctr.html they have lots of information on setting up the bike for doing tri/TT work (and they have a good forums area, but a higher signal to noise ratio)
Also check out the forums at http://www.bicyclesports.com these guys are hard core Tri/TT and are always searching for ways to gain an extra tenth or two.

Andrew

Most TT bikes shouldn't "stretch you out". Height effects aerodynacis less than width. I would get a "fast forward" seat post to chorten up that difference in the top tube, go to chucksbikes.com for a $22 seat post of that type.
Keep in mind a true TT bike has a top tube one cm smaller on Average than its designated size. For example a size 54 P3 in 79 degree mode has a 53cm top tube.

Second, try riding the longer cranks, I prefer a 170 but rode 172.5 when I wanted a better power output. I got used to it pretty quick.

Aerobars aren't going to be all that different if they're under $150 but if this is just an expirement for you, check out ebay and save some money. I got my pair of Syntace C2s for like $40 shipped.