Flat bar conversion

Do you really want to do it?
I tried it once and soon converted back.
if you do it won't be cheap.You'll need specific flat-bar shifters to work with Ultegra
https://www.sjscycles.co.uk/gear-shifte ... rs-double/
MTB shifters(LX/XT/XTR etc)won't work(or rather won't work properly,different pull ratio) and you'll also need Brake levers that will work with caliper brakes
http://www.chainreactioncycles.com/shim ... -prod34695
You might find the shifters cheaper with a bit of Googling or you could just put a complete set of MTB shifters/Mechs on instead.

Why do you want to ? As has been said - it's expensive and not optimal.

Find another LBS or another assistant. This one was wrong.

Ben6899 wrote:

A flat bar won't solve your problem.

True enough.

As well as the assistant being wrong about geometry being the same for rapid as defy.

Even if you could do the flat bar conversion and put the new bars in the same place as the old ones, you will still have the back problem that was an issue with the bar position to start with.

Drop bars or Flat bars are not the issue here - the placement of the contact points in relation to the saddle etc is what you need to look at. This has nothing to do with the shape of the bars. There is no reason why the hoods on your current bars couldnt be positioned in the same place as the flat bars you are looking at - thereby putting your back in the same position. If you then dont want to use the drops because your back doesnt allow it, then fair enough.

I like flat bars personally and ride centuries on them with no issues whatsoever.

But the shape of the bars wont fix your back position.

If a bike fit cant fix it then presumably its because you have the wrong frame that cant be sensibly adjusted to fit you.

Fitting flat bars will change the geometry - they bring the contact point closer towards you, hence why flat bar frames have a longer top tube and stem to compensate. This might improve your bike fit but the fitter isnt suggesting it for that reason because they seem to have told you a bike fit cant fix it for some reason.

I think you would be better off asking what you need to change about your current bike to make it work better for you - if you need the bars closer or higher (the most likely scenario for a back issue I would guess) then you may be able to do this by changing the stem? If not, do you actually need a different size frame?

dickymicky wrote:

Thanks for replies. I'm considering the flat bar conversion because I have a back issue which hasn't been resolved by having a bike fit and is exacerbated whenever I use the drop bars. In the LBS I looked at a Giant rapid, and the assistant told me the geometry is identical to the defy, so he said why not do the conversion.

What did the bike fit consist of and who did it? Not the assistant who told you that the Rapid and Defy had identical geometries! :shock:

Did you buy the correct size frame?

I'd strengthen your back not mess with the bike. Seriously, with proper effort you should be able to ensure that your core musculature can properly support you on the bike if the fit is reasonable. If you have degenerate discs and worn facet joints this is especially so.