Road bike size + aero bars + seat height

benjai

So I've had a Giant TCR Composite 2 for 3 years now. I'm 5"10 (nearly) and the bike is M size. This is correct according to the Giant size guide. I mainly use it for commuting and its a pretty good size, although I could perhaps lower the seat perhaps by 1 cm.

I'm currently training for my first triathlon, and decided to get some clip on aero bars. On my first ride out in Regent's park, I gained around 2.5kmph with about the same as my regular effort. Great!

I then asked to missus to take some side view photos of me whilst I adjusted the bars so that I could get as close to a "proper" aero position as I could. After some tinkering, I realised that I couldn't actually get my body that far down, because my seat is only about an inch higher than the handle bars, if even that. I noticed that with most TT bikes and even some regular road bikes, that the seat is quite a lot higher than the bars.

Given that I can't put the seat any higher, do I need a smaller bike?

0ced0

stem can be adjusted too. any spacers between stem and headset?
can you post the side view photos that your missus took

simon_masterson

Not all TT bikes have a big drop - it entirely depends on the rider, the position, and the frame dimensions and the bike setup. Eyeballing your position has very limited value (proper testing is the only way to know what is fast and what isn't), but this is the reason why TT bikes exist and are rather different to road bikes - it varies between cases, but you won't get an ideal TT position on a road bike with clip ons.

Moreover, it's entirely down to you - the most aero position will usually reduce power output, and the most powerful position usually won't be the most aero. Most people have to adapt to their ideal position. The fastest time triallists tend (funnily enough) to be the ones that can produce a lot of power in a really slippery position, like Boardman or Wiggins, but not everyone (by any means) can do that.

rick_chasey

Pictures would help, if you don't mind that....

jrich

The seat will usually remain a constant distance from the bottom bracket so you can move it up so long as you move it forwards as well. This is what I did before I got a TT bike. You probably have a seatpost with setback at the moment i.e. the clamp is not centred above the middle of the post but is set back behind it by some 20mm or so. What I did was bought an inline seatpost where the clamp is directly above the post (0mm setback). Once you have an inline post you can then move the saddle up a bit and still maintain the same distance from the BB. Of course this will change you position for normal riding so I kept the old post with a spare saddle attached and just swapped them over when necessary.

Like others have said you can also go lower with the stem at the same time by removing any spacers from below it. In addition you can buy a 17 degree stem which will lower the bars a little bit more.

Once you've done both of those things you should be able to a achieve a reasonable TT position, unless of course you're riding a bike with a massive headtube in which case you'll just have to make do. Or buy another bike (always the best answer!)

pilot_pete

jrich wrote:

The seat will usually remain a constant distance from the bottom bracket so you can move it up so long as you move it forwards as well. This is what I did before I got a TT bike. You probably have a seatpost with setback at the moment i.e. the clamp is not centred above the middle of the post but is set back behind it by some 20mm or so. What I did was bought an inline seatpost where the clamp is directly above the post (0mm setback). Once you have an inline post you can then move the saddle up a bit and still maintain the same distance from the BB. Of course this will change you position for normal riding so I kept the old post with a spare saddle attached and just swapped them over when necessary.

Like others have said you can also go lower with the stem at the same time by removing any spacers from below it. In addition you can buy a 17 degree stem which will lower the bars a little bit more.

Once you've done both of those things you should be able to a achieve a reasonable TT position, unless of course you're riding a bike with a massive headtube in which case you'll just have to make do. Or buy another bike (always the best answer!)

But that is completely compromising your position. If it is a road bike and you are set up correctly, changing you seatpost to an inline seatpost, thus setting yourself further fowards (even keeping the BB to saddle distance the same) means that your weight distribution is going to change significantly. You will probably find that you will now have the feeling of falling forwards constantly onto the handlebars.

This won't be as significant a problem when on the tri bars (although you may feel you have too much weight on your elbows) but will completely compromise your 'normal' position when not riding on the tri bars.

The problem is that a road bike with tri bars is not a TT bike and you are unlikely to get an ideal TT position on it. It will always be a compromise position, but whichever bike you are setting up you need to get the pedal to seat position correct and adjust everything else subsequently.

You are better off keeping the ideal road bar setup whilst riding on the road. Then you need to set it up for best TT position for a TT and not ride on your compromised road bars position. If you note the differences it wouldn't take long to adjust before each TT and then re-set for road riding in between. Either that, or accept a compromise with one or both positions.

The N+1 rule obviously dictates that the best solution is to buy a dictated TT bike to complement your road bike. Then both can be set up properly.

PP