Drove two hours to Kentucky with the tandem (and Favorite Stoker) for a club ride to Rabbit Hash (on the Ohio) but a few miles from the start, on the first of a couple of long downhills, developed a front wheel shimmy just after deciding to slow down a lot (max speed was 36.5mph). Was able to come to a stop upright - that was not a sure thing! With the help of the rest of the group - 3 singles and 4 tandems were on the ride - checked out the bike and could find no obvious problems. But, as this had never happened to us before and as we were "shaken up" by Shaking All Over, we rode the Screamer back to the start to drive back to Indy. No problems on the ride back to the start and could find nothing obviously wrong once back home. Will continue to be checking out mechanical aspects.
Found an interesting piece on Bicycle Shimmy by Jobst Brandt on the Sheldon Brown site which talks about harmonic dissonance of a bike frame which can happen under certain circumstances. Fast downhill on smooth pavement while coasting can contribute, as can a 'death grip' on the handlebars. That describes our downhill run today. Interesting read. I'll continue to check out the bike and make mechanical and riding style adjustments.
At any rate, we got out later today and did a 25 mile local loop with no screaming downhills and did just fine.
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Bacchetta Giro A20, RANS V-Rex, RANS Screamer