Originally Posted by
Tourist in MSN
You really should focus on top tube length when looking at bike fitting well. One 58cm bike might fit quite differently from another 58cm bike. That is why I suggested that he try it.
I worked in a bike shop in the 1970s. Back then most bikes came in about 3 sizes instead of about 10. We have gotten very picky about getting our bikes sized just right, but realistically a change of stem can often make up for quite a bit of sizing difference without any problems.
My niece uses a 58cm carbon road bike but she is several inches shorter than me and her previous hybrid was a very different size from her road bike. The difference was that her hybrid had a pretty long top tube, the road bike a short top tube. You really do not know how a bike will fit until you get on it and try it.
The OP is taking about different sizes for one bike model.
The seat tube length (what the "sizes" are usually) is a useless way to compare different models (the top tube length is a much better number).
The fact that people "made do" with three sizes in the 70's doesn't mean they aren't better off with more sizes to choose from.
A new cyclist may not be able to choose the best size by just "trying it". They might really need to work directly with somebody with experience.
He was told by a shop employee, presumably, who knows what he looks like, presumably, that other sizes (two larger sizes) would be better. And you, having no idea what he looks like, think that your advice is likely to be better.
What does your niece have to do with anything?