Tandem Cycling - Handling problems at higher speed?

I'm wondering if it's my imagination or if I had a bit of handling problems yesterday at around 37 mph.

The bike: '98 Burley Rumba Softride, Conti UltraGatorskin 28s, inflated to 120 lbs.
The team: 190 lb captain, 145 lb stoker
The road: Chipseal, hilly, 88 degrees and sunny, no wind

What happened was that we were heading down a hill and when we got close to our top speed of 37 mph, I felt that the front wheel was floating just a little bit. I kept the front wheel straight and when we slowed down as the hill leveled off, the floating feel went away.

I've had the bike up to this speed before, even a bit higher (I keep promising myself that I'll watch the speed, though!), and haven't noticed this happening. Was it the pavement? The tire? The heat? My active imagination?

The most common speed related issue is a shimmy, which I don't think anyone would describe as a 'floating' feeling. More like the handlebars are trying to jump out of your hands.

I'm thinking it's not your imagination per se, but just a change in handling feel with speed which you're not accustomed to. Depending on the rake and trail, a bike will be more or less stable at higher or lower speeds. This, combined with your paying closer attention than normal to the steering forces (natural when going faster than you're used to) could result in feeling that there's something 'strange' going on. Maybe you had a tighter grip than usual on the handlebars?

I think you need a front spoiler to reduce some of that lift.

I'm wondering if it's my imagination or if I had a bit of handling problems yesterday at around 37 mph.

The bike: '98 Burley Rumba Softride, Conti UltraGatorskin 28s, inflated to 120 lbs.
The team: 190 lb captain, 145 lb stoker
The road: Chipseal, hilly, 88 degrees and sunny, no wind

Have you and your stoker ridden this road before with the same tires at that pressure before... or one like it, e.g., chipseal descent at brisk speed?

Did you ask your stoker what they were doing or what they felt while this was happening?

Has your stoker reported any change in the movement / stability of their Softride boom?

Road conditions (chipseal, etc) can give you some abnormal feedback through the bars.
Never have had a 'float feeling', but have experienced vibrations due to various road conditions/speed combinations.
Suggestion: check and see that headset isn't loose; also check if front tire/wheel are up to snuff.
Could be a one-time thing due to just the right (or wrong) combination: road condtion/speed/wind/temps.
Pedal on TWOgether!
Rudy and Kay/zonatandem

Check that the cassette is "properly tied"... On my single, a loose cassette gave me an instable feeling when sprinting in the tallest gear (smallest cog) once.

Good questions. I'd actually ridden the same road at about the same time of day just the day before, but with my usual stoker who weighs probably 20 lbs more.

Didn't experience the same thing, but we might have been going a tiny bit slower.

Maybe I was a little nervous, because this was the stoker's first tandem ride and she'd never been on a bike at that speed before. But she wasn't nervous at all. In fact, it was amazing that we rode the same hilly 15 mile route averaging a couple of mph faster than the day before :D

....but with my usual stoker who weighs probably 20 lbs more.

My guess is, the change in stoker -- both with respect to the reduced weight and perhaps a bit of a death grip on the bars by you given your stated "nervousness" and reaction to the change in bike feel.