Colorado Kid

Today, it was in the 40s when I left for work. (It was 65F the other day). What type of long underwear to you recommend for commuting?

chas58

I guess I sweat too much to need long underwear.

I always wear wicking clothing. Poly pro works good, but stinks when sweaty
My best bet is to use wool - especially close to the skin. Knee high thick wool socks are my winter goto. Everything else is layer-able.

My best purchase though is going to salvation army and getting a light wool sweater for $5. They are great in the winter. Get merino wool if you can, cashmere is even better.
Sure, I have $100 custom wool bike jerseys, but the $5 stuff works just as good* and I don't have to worry about it getting trashed.

If I need more on my legs, any light weight poly pro long underwear works. Bike shorts with shamy are good to keep the butt warmer than the bike seat.

* (ok the $5 stuff doesn't have a back pocket over my butt.)

Bikewolf

For average commuting purposes, it can be fun to wear shorts (be it a stretch jeans or something else) with long sweatpants on top. Especially in the fall when it starts to get cool in the morning but warms up during the day, and is warmer on the way back. If you want to, "extend" your shorts using leg warmers (or socks up to knee height). On windy or wet days, you could add inexpensive lightweight rain pants. — Another trick is to use zip pants with leg warmers underneath.

Of course, once winter really arrives this method won't be so much fun anymore.

pdlamb

If you're wearing long pants, I doubt you'll need long underwear. Down to 40F, one (thin) layer on my legs is enough. Though I usually go with polypro tights over bike shorts.

BobbyG

I wear shorts down to 38F, then I wear semi-breathable "jogging pants". Below 18F I wear another, loose pair over that along with wool socks. But everyone is different.

Colorado Kid

What is a good place to buy long underwear? My local military surplus has nothing in stock. Any ideals of where is the best military surplus place to buy from?

noglider 

I got some great wool long underwear at REI.

takozukuri

When temperature dips below 40F, I use a base layer (similar to something that skiers use) that breathes but also provides thermal protection, my cycling jersey and a wind breaker. Depending on how I feel when I walk out the door, sometimes I'll add knee warmers.

I will say that I don't commute when it drops below 30F -- luckily not too many of those days here in HOU area.

RggBee

I use quick drying thermal underwear. I don't stick to particular model, still trying. The last one I've bought is made by Wonderful Life. The main thing it should be able to keep sweat away from your body fast.
I do sweat so this is really important. Thankfully my job requires me to change my clothes before work.

jay4usc

have you guys ever heard of Nike, Adidas, Under Armour? They all have them and they call them base layers.

PDKL45

Or if you're on a budget, have a look at Aliexpress and eBay.

alloo

Go to ArcThrift stores for all your needs.

rhm

My legs don't get cold on the bike. Hands and feet, yes, but not legs. Whatever thin long pants I'm wearing to work that day, they'll be fine on the bike.

GeneO 

Merino wool or Underarmor if you need it. My legs never get as cold as the rest of me either so sometimes just something to block the wind.

Germany_chris

This is the only time of the year I wear cycling gear. Good insulated tights are a god send in the winter

jsilvia

I use UnderArmor base layer when the temp. drops to the 40s.

takenreasy

No thermals for me until below zero.

79pmooney

I'm a big fan of Patagonia Capilene. I have all three weights and ridden with al of them. (I also buy the REI brand equivalents. They work also but are not as nice or long lasting as the Patagonia ones. I wear either old shorts or UnderArmour undies under and tights over.

wolfchistian

Thermal underwear is the best option for me, I sweat too much, but with it, is okay actually