I've posted here about how I have my gear dialed in for rather cold weather riding suitable for the Minnesota winter. That's mostly true, but the one challenge I have is my thumbs.

My standard set up in the cold is to have bar mitts, lobster claws (Pearl Izumi) and glove liners. Below about 15 °F, I add in chemical hand warmers and this has my hands and 4 fingers just fine down to -10 °F.

Except my thumbs.

The problem is partly that the thumbs are isolated from the other fingers and that the hand warmers don't help down there, but actually the real problem is that the part of the thumbs (mid-thumb, along the inside, right near the joint) that are pressed up against the handle bars and/or the brifters, are getting conductively cooled from the metal. Also, I think the pressure applied through the glove limits the insulating effect of the glove.

On longish rides, my thumbs get cold and occasionally this has led to frost nip. Just in those spots.

At times I consciously remove the pressure, steering only with the rest of my hand, and this helps, but it's not my natural "grip" and I have trouble maintaining it. Also, I can withdraw my thumbs into the "Palm" part of the mitt for periods of time. Neither are ideal solutions.

I've considered fastening some extra insulation to the right places on the bars, but I haven't quite figured out the right material/fastener/geometry.

The only other solution i can think of is electrically heated gloves.

has anybody fought and defeated this problem?