Posted by: earleb
Wool tights or 3/4's under the lightest weight summer shorts you can find. If it's actually waterproof enough to keep you dry you'll sweat them out and end up wet inside anyway. The wool will keep you warm when wet, I'll take warm and wet any day over wet and cold because nothing short of a rubber suit is actually waterproof. The light summer weight shorts shouldn't hold much water when they are soaked.
Unless you're just banging shuttle laps, then just take some cheap over pants and cut them off at the knees and pull them on overtop your regular riding gear.
I'm on this page too, cheap set of lightweight shell shorts over woolies over top of shammies. When the ride is done just pull off the dirty shell and woolies, toss them in a bag and pull on a dry set of shorts for for the ride home or apres. Get home and hose off the dirty ones and just hang to dry. Even in the wet my legs never really get cold though, so I'm more concerned about keeping my feet warm. I find a double or even triple layer of thin poly-pro socks under some wool socks are magic - and they're cheap as chips. If you want a bit more protection and ride clips get a cheap set of neoprene booties off of ebay/amazon.
For tops it's the same deal, a single or double layer of merino depending on temps and a lightweight water resistant jersey/jacket to deal with the mud. Toss the jersey in the same bag as the shorts and then hose em off at home before hanging dry.
The worst part about winter riding is the extra maintenance on the bike and having your wiener shriveled up like a baby carrot due to the cold and wet.