Offset rear dropouts for fatbike tire clearance

Fat bikes are becoming increasingly popular. But there are some unique technical challenges in building these bikes. As we can see if we turn on the auxiliary view of the stays, the tires on these bikes are so wide that if we were to use a standard mountain bike hub with a 135mm over locknut dimension there would not be enough clearance for the chain to run from the chainrings back to the rear cassette without rubbing the side of the tire. One solution is to use a wider 170mm hub as could be demonstrated by changing the Rear dropout spacing field from MTB to Custom and editing the text field to 170mm.

However, an alternative is to switch back to a standard 135mm hub and simply offset the hub in the direction of the drive side. In BikeCAD 9.0 we can now do that by changing the Offset in drive side direction field. The Surly Moonlander uses an offset of 28mm.

If we go to the seat stay dialog box we'll notice that the seat stays are still listed as symmetric. Although we can see that they clearly are not symmetric, the dimensions used to define the tube diameters and curvature of the stays on either side are equal and in that sense the stays are symmetric. We will want to change the seat stays to asymmetric and apply a greater deflection to the non-drive side to eliminate the current interference between the stay and the tire. We'll do the same to the chain stays.