I've got a brand new 2009 Salsa La Cruz cyclocross bike I'm using as my commuter (9 miles each way in Mahnattan) and soon it'll be pulling a trailer with my twins (now 7 months old).
I need to fit a rack on the rear for panniers to carry a book or two, a few files, lightweight laptop, office clothes, occasionally a towel. I've got one set of rear eyelets at the dropouts to handle fender and rack. I've got no upper braze-ons for mounting a rack. This bike has disc brakes and 700c rims/ tires.
I've searched these forums and the web in general. It seems that my options are these (in order of my current preference):
1. Use a 28.6 mm seatpost clamp with rack mount eyelets on my 27.2 mm seatpost with some shim.
2. Use P-clamps and go to the seatstays.
3. Mount to the brake bridge.
4. Replace my seatpost clamp with a 31.4 mm seatpost clamp plus some shim on my seat tube.
I'd love to hear other suggestions. I think I want a rack beefier than will mount solely to the seatpost, so I think beam racks are out. I'm more likely to go Tubus than anything else.
Option 1: using my 27.2 mm seatpost, first apply some shim, then a 28.6 mm seatpost clamp like this one:
Mount rack to eyelets on new seatpost clamp. I would leave my current seatpost clamp in place on the seat tube, performing seatpost clamp duty, and the new clamp would serve only as a rack mount point. Advantage: puts any scratches or damage on the seatpost instead of the frame. Offers two mount points instead of one on the brake bridge. Avoids any potential clearcoat damage that would result from p-clamps on the seatstays. Disadvantages: the clamp will require shim to fit on the post. It will not look great. It might not be as sturdy or stable a mounting as the seatstay approach.
Option 2: use p-clamps on the seatstays. Advantages: easy, hardware readily available, cheap, quick. Disadvantages: I really don't want to do any harm to the paint on this frame. Won't mounting these dull the clearcoat under the p-clamps?
Option 3: mount to the brake bridge. Advantages: fairly easy, no scratches or damage to frame paint. No goofy looking extra seatpost clamp plus gnarly shim on my seatpost. Disadvantages: single mount point should allow significantly more sway in the rack than I want; should support less weight; not a lot of racks I like available that support this approach.
Option 4: replace my seatpost clamp on my 30.0 mm seat tube with a new, larger seat post clamp plus some shim. The new clamp would have rack mount holes. Advantages: not many. Disads: ugly, likely to scratch paint, not likely to clamp seatpost super effectively; probably this isn't really an option.
Please offer your advice and help me with the pros and cons. I think I've talked myself into p-clamps.
Also: thoughts on which rack I should use with disc brakes and 700c rims/ tires? I've looked at options, so I'm looking for your real-world in-use evaluations. Thanks!