Tri Bike Fit - 54 BH GC Aero 2008 Bike

by Gerry Kenny
(Ireland, Europe)

Tri Bike Fit - 54 BH GC Aero 2008 Tri Bike

Hi, I am considering buying my cycle club mate's lovely GC AERO 2008 tri bike which he is selling as too large for him. I am 5ft 11 1/2" (181cm) height, inside leg measures 32.6" (83cm) and the bike frame is 83 x 0.65 = 54 frame.

I weigh 11 1/2" stones (73kg). I am 48 but an experienced and elite athlete, very fit and race triathlon and duathlon almost every weekend. The frame is a medium 54.

I would use it for duathlon, sprint and olympic triathlon only. The bike has the 9cm stem length Vision Tech Tri Max bars which are non adjustable. I have taken out the bike on 2 x 10miles TT to test and the fit feels very good.

However I am inexperienced using tri bikes. To date I ride my modified road bike in triathlon/duathlon. Currently there are 2 x 15mm spacers under the tri bars and 1 x 15cm spacer above, so I could drop or raise the bars. Ultimately if I buy I will get a bike fit.

My question is if you can offer some advice based on your experience - see the pictures to help with your comments:

  1. Is the size 54 the correct one for a triathlete my size?

  2. Is the 9cm stem OK or should I have a longer one and if so which one?

  3. Is this the correct bike size for me?

  4. What improvements to the bike setup would you recommend?

Thank you.

Intelligent Triathlon (Mark) replies:

Judging by the measurements you gave I would say this is the very smallest bike size you could go. Then looking at the pictures I would be inclined to say it is too small in the current set up.

Having said that, I think you have your saddle too high, if this is the position you ride. There is very little leg bend when your foot is at the lowest point, and it looks as if you are having to rock to one side to even do this.

It is also a little short (elbows and knees are too close when the cranks are parallel to the ground) so a longer stem may help there. This would improve handling and reduce the weight you place on the elbows. If the saddle comes down a bit you might want to then drop the bars a bit more so those spare spacers could be useful.

I was surprised when I saw the picture of the saddle, that it was actually so far forward. In the picture with the cranks parallel to the ground it looks like you need to move the saddle forward, which leads me to believe the pictures you have of the set up are not how you would ride. I suspect you have pushed your bum back on the saddle, and that as soon as you rode you would slide forward, which would then make it far too short on the reach.

So to summarise:

  • Try dropping the saddle (2-4cm would be my first guess)

  • Try a longer stem (11-13cm would be a start)

  • Try riding it for at least 10min hard, even if it's on the turbo, (road would be better) and see what you do. I bet you pull yourself forward on the saddle.

If you try and ride it in your current set up you are likely to hit your knees on the bars, and rock from your hips, neither of which are going to be very good!

If your hip angles and flat back are sustainable, after you have moved it around a bit you will have a very good aero position. But if you are not used to this, make sure you do some good training sessions on it before you race, and gradually increase the time spent in the tuck position.

In an ideal world I would say this 54 BH GC Aero 2008 Tri Bike is too small and you need to get the 56cm. However good deals from mates can be attractive, but only do it if it actually works!

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Oct 18, 2011
by: Mark, Intelligent Triathlon

Thanks for your comments, always good to get some feedback and hear the outcomes from our advice!

Oct 18, 2011
Choosing that TRI/TT bike
by: Anonymous

Thank You Mark. Your analysis closely matched advice I received from another experienced bike fit expert.

I hope the analysis and pictures will be helpful to others doing same as me.

This experience was very interesting. Much more involved than I expected.

In my opinion choosing the right TRI bike and setting it to get max power and to have a comfortable, maintainable aero positioning setup is difficult.

Just going to a store, taking a short, nervous first spin and then immediately buying that tri bike may be a bit risky. I suggest doing a little pre-buying investigation.

Talk to a few of your fellow cycle club high performing athletes of similar size and weight who use a tri/TT bike. Get their opinions on their bike selection and fit. Better still get a spin on their machine on a known course ie a course for which you have previous times. Then you can really compare times and confirm that you can power it up and maintain an aero position.

Also talk to bike set-up experts and coaches before buying. Then if you buy, ride for a while and then when you know the bike feel, then get a proper bike fit. Gerry

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