I am close to buying a 48cm Vitus 979. Not sure of the exact year but it has the rear collar bolt on the seat tube not the Grub screw.

Here's the concern; the seat tube measures 48cm. All other 48cm bikes I've seen and all geometry numbers I've seen for this frame size indicate a 53cm top tube. However, this owner swears it is 50.5cm. He is an honest guy, who has been in the bike industry for quite a while and has been a bike designer....so I think he knows how to measure a TT. He thinks it could have been some sort of limited run. Kinda hard to believe but possible? Also, there is no frame size stamped anywhere on the bike even though I have seen it on most other Vitus frames. I've seen photos and the bike looks clean and untouched.

Anyone have any opinions?

Thanks.

PS: Sorry if this is a re-post, having some computer problems.

My 979, which is probably of a similar era based on the "regular" (non-grub) seatpost bolt, has the size stamped into, as I recall, the headtube lug on the non-drive side.

From what I've seen, small frames like that (in general, not necessarily Vitus-specific) seem to hit a top tube limit of about 51 cm, so I guess 50.5 could theoretically be possible.

This catalogue page (PDF) shows the smallest frames having a 53 cm top tube, but a 48 cm model is not listed. Perhaps a 48 was added later with a shorter top tube?

Thanks for the input.