Do manufacturers change their same brand sizing?

[Nomadski]

I find the best way to compare sizes is to look at the notional horizontal top tube measurement. Or you could be a bit more precise and look at stack and reach measurements.

My top tube measurement of my current Cannondale (54cm) is the same as the current geometry spec of the Cannondale Synapse 2021 54cm. This is nearly 4cms longer than both my Dolan and Cube which are supposed to be 54cm.

It could well be though that the 56cm is the better size for me as now I think about it I did get a longer stem for the Cannondale post purchase.

 

[Venod]

I bought a Synapse last year it is a 2019 model 56cm, when I first saw it on sale I dismissed it as been too big until I checked the geometry it was nearly the same as my 54cm OnOne which is a good fit, the 54cm Synapse has a very short seat tube IMO, it would have been OK but I would have always thought it was too small.