Rear racks have been problematic for those of us who like disk brakes. If your bike has the disk mount on the chainstay, most if not all standard racks will fit. But if the mount is on the seatstay, as on our Co-Motion and Cannondale tandem, then the only really good racks have been the Old Man Mountain Cold Springs and Sherpa. We have used a Sherpa with good results on both bikes. The drawback is that both mount via the skewer which makes wheel removal cumbersome. They also have an unconventional look if that matters to you.
I’ve posted more photos at my Flickr page.
Topeak also makes disk-specific rear racks, the Explorer and Tourist, which use built-in offsets at the eyelet to space the rack beyond the disk caliper. I have used the Explorer and it’s OK for a $35 rack, but not elegant. There are some threaded spacers out there from Jandd and others that allow you to mount a standard rack outboard of the disk caliper, but the rack ends up off-center and is dependent on the spacer.
Venerable rack maker Tubus recently came to the rescue with their Disco rack. It uses curved tabs at the lower legs to position the rack behind the caliper rather than outboard. Tubus includes a skewer to mount the rack through the hub if needed, but the rack mounted normally to our Co-Motion dropout eyelets. I mounted the fender stays to the same eyelet between the rack and frame for now.
The only downsides to me are the top shelf, which is narrow for a large racktop bag, and the $154 price tag (at least until Wiggle starts stocking it). The Disco is rated to a maximum of 20 kg. or 44 lbs., which might be a problem for some folks. We’d rather not carry 44 lbs. in the rear panniers so it’s fine by us. We’ll still use an Old Man Mountain Ultimate Lowrider front rack, by the way.
We’re going to test this rack on our upcoming honeymoon tour of Skyline Drive and the Blue Ridge Parkway, and I’ll follow up. For now, here’s a review from Bike Radar.