I got an M7000 SLX single crankset for my Krampus, and was surprised to see that it has a second set of chainring mounting holes. Did they sell me a double crank instead of the single? I was perplexed and unsure whether I should return the crankset, so I set out to find out the truth.
Shimano lists the single (FC-M7000-11-1) and the double (FC-M7000-11-2) crank sets as different products. The box from the single prominently says “1x11s” on it.But inside the box we find a crank with two sets of chainring mounting holes!
So I did some web searching and I turned up a forum discussion and a product review, saying that somebody bought single crankset to convert their 2x11s setup into an 1x11s, only to find that crank they bought is identical to the one they already had. I found evidence that this is true for both SLX (M7000) and XT (M8000) cranks. I feel for these people, as they were misled by poor documentation and marketing for these products.
If you look at the official documentation, the chainline for the single crankset is quoted at 50mm, while for the double it is 48.8mm. This further proves that the cranks are the same – the chainline on the double is centered in between the two rings, while on the single it is measured to the outer ring.