Originally Posted by
thumpism
The instances I mentioned all occurred on steel framed bikes and all with either 27" or 700C wheels. I have not toured on an aluminum framed bike, nor on a 26" wheeled bike of either frame material. Before I go spending bucks on an aluminum touring bike (was that close to an older Cannondale but got scooped) I should give my steel Cimarron or aluminum Marin 26ers a try.
It may be true that modern racks are stiff, but I have a hard time believing that they are significantly stiffer than an old seatstay-mount Blackburn or Eclipse, or one of their front racks.
The two bikes I showed photos above are 26 inch, but I see no reason that a 26 inch bike would be any different than a 700c bike when it comes to shimmy. I had a LHT in 700c that had a terrible shimmy. Surly refused to warranty it, the bottom bracket shell was warped. I put the frame in a metal recycling bin it was so bad. I talked to a frame builder and she said that it was very possible that the bad welding job on the bottom bracket shell caused the shimmy as that whole part of the frame was weaker from the welder not having his heat control settings right.
A friend of mine used to tour on Aluminum, he was happy with it. As far as i know, it had no shimmy although he had all the weight on the back rack. Then he bought a Titanium frame, had a minor shimmy when all the weight was on the rear rack, but he minimized the shimmy as much as he could by moving the rear panniers as far forward as his heels would allow. When he added a front rack and panniers, I think that greatly reduced or got rid of the Shimmy.
I usually tour with a Tubus Logo rear rack. It is stiffer than the Surly rear rack although the Surly is twice as heavy. I can't say if the Tubus is stiffer than an old Blackburn or not, but the Tubus is much stronger than the Blackburn. The Tubus Logo is rated at 40 kg.
I should have mentioned this in the posting above with the photos, the Sherpa chainstays are 450mm, the Nomad chainstays are 466mm. Thus, when I switch the panniers from one bike to the other I have to change the upper pannier hook positions, I always set the panniers as far forward as I can without heel strike.