Intermittent rear wheel skittishness

Whenever skittishness is mentioned, tyre pressure (too much of it) springs to mind. However the fact that it happens after a bump is odd.. if it was down to tyre pressure I'd have thought it would happen all the time. How much pressure are you using and how heavy are you? I think about 85psi is recommended for 28mm tyres / 75kg rider.

you're probably over inflating for your weight.. I'm 92kg and run 95psi front and 105psi on the rear (conti gatorskin hardshells).
dropping pressure is very unlikely to slow you down.
also - http://www.dorkypantsr.us/bike-tire-pre ... lator.html
may be of use to you.
the paragraph below is from the sheldon brown website..

Rolling Resistance
"Rolling resistance" is the mechanical friction generated as the tire rolls. As a segment of the tire tread rolls into contact with the road, it deforms from its normal curved shape into a flat shape against the road, then back to the curve as the tire rolls onward. The deformation of the rubber in this process is what causes the friction. A bias-ply tire has some additional friction because of the "Chinese finger puzzle" effect of the bias plies. The edges of the contact patch scrub against the road as a segment of the tread becomes shorter and wider where it flattens out, then longer and narrower as it becomes round again.
There are four ways to reduce this friction, each subject to trade-offs:

The thinner and softer the rubber/fabric of the tire are, the more flexible they become.
The trade-off with this is that the thinner the tire gets, the more fragile it is, and the sooner it will wear out.

The higher the air pressure, the less the tire will deflect.
The trade-off with this is that if you pump the tire up too hard, you lose the benefits of pneumatic tires: the ride becomes excessively harsh, and traction will be reduced. In addition, extremely high pressures require a stronger (heavier) fabric and stronger (heavier) rim flanges.

When riding on a smooth surface, rolling resistance does decrease theoretically with any increase in pressure, but with modern, high-quality tires the rolling resistance at correct inflation pressure is already so low that the infinitesimal reductions gained are more than outweighed by the trade-offs.

In practice, riding surfaces aren't perfectly smooth, and overinflation actually increases rolling resistance, due to vibration.

Did you check for loose spokes after hitting the pothole? This could give a skittish feeling.

Dyrlac wrote:

I tend aim for about 100 psi (when I remember to top up, mostly when a thumb test reveals any degree of squidge, which seems to be about 80psi), and pack, errrrr, 78 kg of engine. If we're at the margins PSI-wise (and that may be the case; as mentioned, I'm not too happy with grip overall) and my ride profile/weight distribution changes even a little after a bump, that would possibly explain the behavior. Assume dropping down to 85 would improve grippiness generally, but how big is the speed/acceleration penalty?

Some kind of road fouling would also explain it, and I've definitely had that before, but this "feels" qualitatively different -- exactly like a pinch flat.

There is zero penalty for running the correct pressure. Higher pressure does not equal faster. Higher pressure can even be slower due to reduced traction, especially when accelerating.