D.2.1. speed-drive - type "BCD110" for screwed-on chainrings with 34 - 53 t. and BCD110 mm
There are two speed-drive versions available. The "BCD110"-type allows to mount chainrings with 34 t. or bigger (up to 53 t.). 34 t. equals approximately 56 t. in high gear mode.
Chainrings up to 40 t. are light-weight, Swiss made steel chainrings with hardened surface and a thickness of 2 mm.
For any of these chainrings you can get trouser guards, even double sided guards if required, which is often used on folding bikes to prevent the chain from falling off while being folded.
Important remark: chainrings smaller than 40 t. must have an inner diameter of 96 mm instead of 94 mm as usual. If not, they can't be mounted on the left side of the spider (see photo on the right).
All original Schlumpf chainrings come with this inner diameter of 96mm