I'm looking at a vintage frame for sale. My ideal frame size is 52-53cm + 10cm seatpost.
This one is 50cm.
I like the idea of a smaller frame with some longer seatpost/handlebar.
Is there any problems related to the topic ?

I've often thought that using seat tube length as the basis for bicycle sizing was dumb. That's the easiest dimension to adjust.

Wherever you got the idea that 52-53 is the ideal frame size for you - what do they say about top tube length?

The image illustrates the 50 cm on the frame, that I'm looking at.



The top tube length is 51cm

So whoever told you that you need a 52-53 cm seat tube, what top tube length do they say that you need? Is that 51 cm top tube actual or virtual (horizontal)?

Figure out what effective top tube you need and go from there.

if 52-53cm C-T is your ideal frame size.. that would most likely have a 51cm top tube length as well


so there shouldn't be any difference in top tube length

I wouldn't bet the rent money on that.

i wouldnt either

what im saying is; in that frame size 50-53cm c - t.. most common road bikes the top tube is the same length

A super long stem can lead to twitchie handling because you have more steering leverage. Suggest you go to your LBS and ride a few, record the measurements and look for a used bike or frame that is close to the one that "feels" the best.

Good Luck

I would say different, but not twitchy. In my experience, the most noticeable difference is felt when out of the saddle, but you adapt extremely quickly to it. I would actually suggest that it's less twitchy, due to the fact that the steering is effected less per handlebar distance traveled.

-Jeremy

Tunnelrat81,

Maybe I wasn't clear in making my point regarding fit and test riding. Too many people try to "dry lab" fitting. The stem comment was just a personal observation. When I've tried to make a too small frame fit with a long stem, I never gotten them too feel right. I've been a commuter, light tourist and century rider, who rarely gets out of the saddle. Thanks for clarifying for the OP.

Regards,

Van

You can usually go +/- 2 cm from optimal and still get a reasonably good fit. I find it's usually easier to make a slightly undersized frame fit than slightly oversized. Amount of seatpost showing is a "don't care" (unless you're trying to achieve a certain aesthetic). Stem length is where you don't want things to get too crazy. As long as you can keep the stem in the 80 - 120 mm range, you shouldn't have any issues. Longer/shorter than that does start to make the steering feel a little off.

dont do it,,,dont buy a frame too small

Lots of variation in vintage bikes. I have one right now with a seat tube center to top of 50cm, and a top tube of 57cm center to center. I have another one with a seat tube center to top of 50cm, and a top tube of 50cm center to center.

Focus on top tube length.

As a reasonably tall (6'6" w/36" inseam) person for much of my adult life, finding a frame that fit using the traditional
2" to crotch standover clearance was next to impossible.
I did ride a 27" frame Fuji Royale in the early 80's and the fit was good.
However, the frame was a bit noodly when out of the saddle.
I transitioned to 63cm Cannondale SR frames in '86. This required a 300mm seat post and 130mm stem.
For the most part, that is what I have ridden ever since.
I do have a 66cm 'Dale CAD3, and do like it. But it is awaiting powder coating at the moment.
As for stem length, I find that a 10mm shorter stem is a help in the early season, til my upper body
becomes accustomed to the riding position. Then I go back to the 130mm to stretch out.
However.....................I seldom ride the drops; as I am fairly aero on the hoods.
Now, if I can get rid of some tummy, maybe the drops would be doable...........

I do have several 27" frame Cannondale touring bikes. Perfect for that activity.
I even have one with skinny tires and 2X10 drivetrain for real early in the season.

I'll agree with this. My measured ideal frame size is 56 cm. Amongst my bikes I have 58, 56 and 54 cm. frames and fit on all of them. I don't think I'd fit on anything smaller than a 54.

As above, I generally find that one size (2cm) up or down from ideal is not a problem. But much more than that and it may never be possible to satisfactorily fit the bike to your body.

Do you have a bike now and have you measured it?

700c bikes should ideally be 52cm + IMO .

I ride 56s and i'm 6'2. Long stems and posts are fine for the most part, but there are a few issues sizing down on bikes.

Cranks might be shorter.

Cranks might not be shorter, and toe strike might be an issue (I don't care about this one)

You might need a longer post

The saddle- bar drop will be more extreme, so you probably run a raised stem. This stem is also coming closer to you as it rises. The bar position is what matters for steering, but to get it right, you'll end up with the top of your stem much closer to your legs than on a larger bike.

I had a nasty injury the other day because of this. I dropped the chain downshifting, while standing/ sprinting, and my crank instantly fell sending my knee into the top of my stem. This struck my kneecap and put me off the bike for a week.

A raised stem, especially a quill, will flex a bit too, if you throw around the front end.