hilaryworton said:
I'm getting back into road bikes after suffering for several years away on mountain bikes. I've been trying to do my research on brands/models etc but have got completely baffled by information overload. Can anyone give me some simple advice on 2 basic questions? Firstly how to decide what size to buy? One shop is trying to get me on to a 46cm and another is adamant I need a 50cm. I'm 5'7" (170cm). I've tested a couple of the smaller size bikes which felt OK (but what do I know as it's been so long since I've riden a road bike). My 2nd question is whether to go with a double or a triple? Again, it seems to depend who you talk to (and what stock they are trying to shift - or am I being too cynical?) I need all the help I can get on the uphill parts of a ride and thought that a triple would be the way to go but I've also been told that a compact double would be just as effective. Any ideas to assist the bemused would be gratefully received!
Just as a starter, to give you a ball park idea of size and fit, go to one of these two websites and plug careful measurements into their fit calculators:
www.wrenchscience.com
www.competativecyclist.com
This isn't an exact formula, but will at least give you an idea of what parts of the frame you can measure for "apples to apples" comparison. A starting point and way of educating yourself. And, don't hesitate to bring in a tape measure (get one w/ inches and cm). I have asked shops to actually measure certain things just so I could make a decent comparison. They never acted like that was too odd.
Second, the way people measure frame sizes varies quite a bit, and the two general types of frame geometry - "compact" (aka sloping top tube) and "traditional" (aka horizontal top tube) - will sometimes have very different size numbers for essentially the same overall frame fit.
Finally, there's no substitute for a really good person at a good shop that will explain this stuff to you. Really, you shouldn't have to do all this background stuff yourself, a competent bike sales person should walk you through it and explain why the differences in recommended sizes.
As for double vs. triple, I'm a big triple fan, but only you can decide if you need it or want it. I feel it gives me more range (very low "low" gears and very high "high" gears). I don't agree with a common opinion that ths front shifting is not as smooth as a double- my Ultegra triple shifts very smoothly. The weight difference is virtually meaningless (in my opinion of course). There is also a difference in "q" factor (width).
That said, you can get very close to the low gearing with a compact double - not there but close. If you're strong and dont' have really steep hills, it might do fine. Since they almost always have a smaller "large" front chain ring than a triple or a normal double, there is no way you can get the same high gearing. Again, close, but not there. If/when i buy a new bike, I'll take a serious look at the gears I have vs. what will actually be possible on a compact double. It could be I go with the double, but if there's any question, I'll go with a triple again because it works so well for me.
Again, a good, unbiased bike shop should help you. But they're surprisingly difficult to find imho, thus your need to educate yourself a little.
Good luck.
