First ride below freezing today, -7c, what I wore.
So this is my first ride in sub 0c temps. I was trying to find out what litlle I could get away with wearing and still be warm. What I wore, Patagonia synthetic jacket with a Patagonia R1 underneath. I zipped up the balaclava style hood and had a buff and a beanie under it and my head and torso were toasty the whole way here. I had some Black Diamond glove liners on that are not doing the trick in this cold, it was bearable but some more substantial gloves are a must. I wore some jeans and 2 pairs of smart wool socks with sanuks and my feet were fine as well. All in all except for the gloves it was a very pleasant ride. The socks come up to almost my knees, 1 pair of ski under a pair of snowboard socks so my thighs were not layered at all but it seemed to be a perfect balance to keep me cool enough but not cold. Plus your legs are always moving since I am on a fixie. Anyhow, just my .02, this riding in the winter thing is fun and not nearly as hard as some make it out to be. Happy riding all, year round from now on!!
I have some black diamond (woolweight) gloves too and i don't even go out with them alone at 5C. I don't like the feeling. So -7C ...
I have sandwiched the BD gloves between 2 nitrile gloves and added some 40g thinsulate leather gloves above all. The leather gloves are thin and pretty tight on the others but don't restrict the blood flow as it is the most important thing to look at before anything else. I can go up to -10C for 2hr with this system and have kept the same dexterity than with the BD liner gloves alone. I can do all the basic things. I even took some coins in my leaflet the other day with the gloves on when i was doing my groceries. I could probably even sew something with it but it wouldn't be easy.
I think it could be possible to improve the system by replacing 1 big layer of BD liners gloves by several thinner layers of merino gloves
I already tried that with 2 really thin layers of acrylic liners that i took from some cheap auclair gloves. It was exceptionally warm for the thickness (around 1/8in) but it lasted only 1 year. At the same thickness than 1 BD liner, it would require at least 10 acrylic liners. I can't even imagine how warm this system would be. In fact yes, around 3 times warmer.
Thinking about getting the Black Diamond Soloist lobster mitt or the Mercury Mitt, I will also be using them for alpine climbing as well so I can help to justify the price, hopefully these will do the job.
If your hands are small enough to wear that above the BD gloves why not. If not, i don't know up to what temperatures you intend to use them but if it's to wear them alone I wouldn't go for the soloist lobster as it has 1finger alone. It's not different than wearing some gloves. If your index is cold then it doesn't matter if your others fingers are ok. Same thing with mitts, the thumb is usually the weakness.
On a bicycle big pogies are better than mitts as they usually are as warm if not warmer and allow better dexterity.
If you prefer mitts then high loft mitts like 700 or 800 fill down mitts would be a good option. The advantage of "high loft" mitts compared to "low loft" mitts is that when you grab the handlebar, the fill is compressed on the palm which allow better grab and dexterity