The extra clamp is recommended for racks that do not have the pannier support tube. In common touring racks the pannier support tube is welded on the outer side of the other two, and that compensates for the extra distance added by the fixing parts, so when the Cannier is loaded, it can sit on that support tube. If you do not have that tube, you should consider an extra clamp.
Important: When the Cannier is unloaded, it will not touch the pannier support tube of the rack, and that is on purpose – so if you use an extra clamp, that should also not touch the unloaded Cannier.
The support clamp is shown on the pictures together with other parts for an easier understanding of it’s role. Net weight 68g.
The support clamp has three plastic clamp halves as opposed to the two halves of the suspension clamp. You might not need to use all three of them, check the distance. The idea is that an empty Cannier will not touch the rack tubes other than at the suspension points, to avoid drum noises. Once the Cannier is loaded, weight will push the plastic body against the rack tube or against the support clamp. The ideal distance is the shortest that would still prevent the plastic body of the empty Cannier from hitting the other parts.
If you leave on a cycling tour, you should use all three halves of the support clamp because you ride with loaded Canniers most of the time.
6 mm, 8 mm, 10 mm, 12 mm