I’m in the process of looking for a used road bike. According to measurements I took at a bike shop, I should look for a 53 cm frame. Since I am looking at used bikes, my frame size choices are limited. How important is it that I look for a 53 cm frame? Will a 54 or 55 cm frame likely work just as well? I noticed some manufacturers only sell in rough sizes (e.g. S, M, L) so I assume I have some flexibility.
Also, I realize that the frame size is just the one aspect of the fit and that I have to ensure the bike is comfortable regardless of the frame size.
I rode a bike that was ostensibly (according to standard bike-fit methodology) “too large” for me for a long time, and it worked out just fine. (The bike was a 61cm, supposedly I should ride a 59 cm; I presently ride a 58 cm.)
Getting fit to a bike is not rocket science, though there will be many who will try to tell you that it is. It’s not.
Really, not.
There is typically enough adjustment built into the seat post and stem that you can comfortably fit a bike +/- 2 cm within your standardized “fit.” You may even find that the standardized fit is less comfortable to you than something larger or smaller. Also, note that different frame geometries affect how sizing will feel to you, and that different frame makers size bikes differently.
Mainly, you’re just going to have to try out a few examples and see what you think. In the end, that’s your only sure way of finding what you like: ride on the bikes you’re interested in.
P.S. Congrats on getting into road bicycling! I love it, and have ridden many thousands of miles. I hope you enjoy it half as much as I do.
With the newer threadless standard for stems, getting an up and down adjustment isn’t that simple on a bike you’re buying used.
The steerer is generally cut to fit the rider, although the shop might stick some spacers under the stem. So you might get some down adjustment by removing some spacers, but you’ll end up with part of the steerer sticking up out of the stem. A shop could cut that for you. You also might get some up or down adjustment by swapping out the stem for one with a different angle. And if it’s a problem with reach, you can buy a new shorter or longer stem.
If it’s an older bike with a whatever existed before threadless (quill stem on mountain bikes, don’t know what they were like on road bikes) then the up and down adjustment should be easy to make.
FWIW I have found that different bike companies measure road bikes differently. I know it shouldn’t be, but if you park a 54cm Cannondale next to a 54 cm Trek the tops tubes are at different heights.
::: shrug:::
Get on and ride it.
My mountain bike it a touch too small for me. One of my road bikes is a touch too big and if not for the angle of the top tube, it would probably have been a bad purchase. As it is I only have to swap the stem because I’m only just finding the reach a bit long to be comfortable. (I bought the bike after a discussion here on the SDMB about lighter frames.)
As 11811 and Knorf said, there are a lot of components you can swap out to adjust the fit, although with an older bike you may have to hunt for older parts. A decent bike shop usually has a pile of old stems and seat posts in the basement though.
If you can stand with your feet on the ground and you still have room to lift the bike off the ground before you squish your boys, you can probably adjust it, but if the top tube is really long you’ll find reach and control a bit un-fun. So really, look for a bike that is in your size range and then take it for a test spin. It’s the only way to be sure because frames and human bodies aren’t all uniform. One 55" bike may be way too big for you, but another 55" bike just right.
Three of my bikes came from Craig’s List and I have no complaints.
There is the “compact road frame” phenomenon that you have to pay attention to. There is the trend toward an arched top tube on some road bikes. There is the sloping top tube thing, which may be only on the “compact road frame.”
No, neither were compact frames. The deal was I walked into my local bike shop, he had a brand new 54cm high end Trek road bike leaning against the counter. I looked at it and said it was a 50. No he said it’s a 54 and showed me the tag. I went and pulled a brand new high end C-dale off the rack that was also a 54. The top tube was higher.
At this point we both scratched our heads and WTF?
FTR I ride a 50cm Cannondale, and a 54cm Trek. Even though by conventional fitting the Cannondale is the correct size. The Trek fits me better and is more comfortable to ride.
At first I thought you were noticing the differences in the way bike frames are measured (C-C vs. C-T), but that wouldn’t explain a 4 cm difference.
For anyone that is interested, this is an interesting discussion of frame sizing. He also mentions that some frames with slanting top tubes will be measures as if the tube was straight.