merino base under anything and im fine. i fully recommend wool.
I have Smartwool midweight baselayers that I usually wear every day during the winter. For days below about 25ºF, though, I usually go with Kucharik merino wool tights. Much warmer, but no fly for easy urination. They were also a lot cheaper when I bought them a couple winters ago. 
I wear REI poly-pro long johns under my swerve knicks down to about 15 degrees.
15-0 I wear REI poly-pro long johns under the heavy wool knicks that Kemmer sold me.
Below zero I wear long johns under a pair of Carhart or Gramarchi flannel lined pants
I really want to try some merino stuff but it’s soooo goddamn expensive the REI tights are only 30 bux.
I bought some cool-weather Endura bibs off of Chainlove and tried 'em out for the first time yesterday on a ~15 degree mtb ride. Worked very well, now I just need to get my toes warm and I’ll be all set.
Unfortunately the wool recommendations won’t work (vegan). And I should have specified that I’d prefer bibs, though if a pair of tights are the best then that’s fine.
This is a frustrating search.
http://stores.channeladvisor.com/skiuni ... e%20Layer/
Just ordered two pair. Free shipping. We’ll see how they turn out. Does anyone else have these?
Not vegan, sorry Ben.
I think I’m going to get the Craft Pro WS Thermal tights on a deal through my team. Should be about $100. Not bibs, but no chamois (which I didn’t want) and I’ve been using tights until now anyway.
I have a few pairs of tights I have been wearing in the cold weather months. Formerly Gaylan’s now Dick’s own brand tights. They are okay if it isn’t that cold. For the coldest weather I have a pair of winter Nalini bibs that are very warm. I have wore them on a couple of winter snow MTB rides were I always fall at least once and they are still warm. The newest is a pair of Swobo wool tights I got for $60 off of Chainlove a few weeks ago. I have used them during bike polo the last few weeks and they are very warm. I also have a pair of padded Swobo wool knickers (Fenster I think) that I got this summer off of Chainlove. With the cheapy tights underneath them they are nice and warm too.