CyclesMakaron

In the EMC world, the term Century was used in two different meanings:
- century frame geometry
- Century frame model
Geometry: well explained in catalogues 1990 and 1991, certainly used in Century, Corsa Extra (Max,753,SLX,TSX), Mx Leader, Arcobaleno, Corsa 01, Strada O.S. (and perhaps in Corsa built with Columbus Thron).
Model: built with Reynolds 653 (1988-1990?) or Columbus TSX (1988-1993?).

It follows from the above that frames built from Columbus SLX and TSX tubes could appear in two versions with different geometries (century and road racing - the old classic geometry used in EMC since 1980).
Perhaps it was decided to label them differently. Perhaps it looked like this:
- Corsa Extra TSX, road racing - TT designation
- Century TSX, century - TTB designation
- Corsa Extra SLX/SPX, road racing - designation X
- Corsa Extra SLX/SPX, century - XB designation
Perhaps it can be confirmed (I do not have enough data in my archive) - so far it is only a theory.

Translated with www.DeepL.com/Translator

jet sanchEz

I always just figured you could order a frame from the Merckx factory with whatever geometry or tubeset you wanted.

If you were local, that is.

I have 3 different steel Merckx frames found on the Belgian version of Craigslist and they are all labelled as Corsa Extra but one is TSX, one is Reynolds 653 and the other has no tubing decal. All three have number hangers.

CyclesMakaron

EMC used "geometry types" (road racing, criterum, chrono, century), which could be modified depending on the customer (this applies especially to profis).
Some models had "assigned" geometry (Max, Mx Leader, Corsa 01, Strada OS or older EM Professional and 3-Athlete), others could have different geometries (including those built with Columbus SLX and TSX) - hence the need to distinguish them. In the bicycle frames built with Reynolds 653 and 753 I have not found any distinctions so far - it is known that 753 was certainly built in road racing geometry (whether 753 was introduced in century geometry and whether such frames existed at all - I do not know), and 653 was built in century geometry (whether 653 was introduced in road racing - I do not know either).
Sensational information for me is the existence of Corsa Extra 653 ! (all 653 I've seen so far belonged to the Century model - apart from the earlier frames built with 753+531, but not marked as 653). I am very curious what your frames look like and what the markings are...

CyclesMakaron

Explanation: Since the topic of EMC frame geometry is interesting and popular, there are a lot of entries on the web concerning angle measurement (the most important: between top tube and seat tube - unless someone has a Chrono...). Unfortunately, there were misunderstandings resulting from the existence of... 3 systems of recording measured angles. Recording 72°51' (i.e. angle in century geo for seat tube 56) equals recording 72.85° (approximately 72.9°); recording 73°57' (i.e. angle in road racing geo for seat tube 56) equals recording 73.95° (approximately 74°). In other words, the first record uses a conversion rate of 1°=60' and the second is the decimal system. Unfortunately, there is also an incorrect 72.51° (instead of 72°51'') rounded to 72.5 - a half degree difference can cause some confusion...

nomadmax 

I haven't had all my coffee yet and I may have missed the answer above. Can you tell me the typical seat and head tube angles for a Merckx Corsa Extra (x) on BB and a 54.5cm top tube?

I have another one, also in slx but it isn't a Corsa Extra as it predates the model. I believe you told me it was a Pro SLX.

Thanks for sharing your knowledge here

repechage

Now a number of years ago, Merckx gifted 500,000 euros in an announcement regarding a study on Frame geometry, the point was to better understand scientifically improved bicycle handling and improve safety.

the results were to be open source. Never heard anything after.

the FCI in the 80’s did a study on race bike geometry and the results were shared with the Name Italian builders, from what I observed it favored steeper head angles and shorter top tubes. Gios and Pinarello were adopters for sure.

From my watching Merckx era and modern peloton behavior, the bikes are not helping the pro peloton avoid collisions. Riders cannot seem to ride a straight line. Perhaps this is behavior to protect the wheel they are following? The trend of many riders using long stems125-140mm extensions, wide bars compared to decades ago I do not think is helping.

Merckx bikes during the Time of Eddy’s highest influence seemed to design a conservative bike that one could ride all day. It would take care of you.

CyclesMakaron

Pro and early Corsa Extra have "road racing" geometry, please refer to GITA catalog from 1991 or "German" from 1994 - the data contained in this table are all we have available...