Only when the oil is so thicke the engine just can't turn over even with 5 weight.
Then I guesss I can't not won't.
Actually cold doesn't bother me too much while riding.
I learned to dress in layers in the early 50's before all the new synthetic and supposedly warmer
fabrics were invented and marketed.
Still do the layering. On the coldest of days say 10 below I will wear
O.L.'s nylons, military longjohns, heavy blue jeans, Carhart bibs ( waist down)
long sleeved t-shirt, longjohn tops, zipper front sweater w/ hood, Maybe a levi jacket (waist up)
Stocking cap or ball cap with a earwarmer band, and a neck warmer.
Gloves..silk liners, loose leather gloves or wool gloves and then mittens with one finger.

When I get to cafe, bar or wherever I can remove as needed.

to much trouble you say?
Not when you live the riding lifestyle.

Severe winds last 3 days, can't get bike out of shed, 6 foot drift there and about 20 feet long and 30 feet wide. Plus drive way is drifted in 2foot deep and 75 feet long and about 15 feet wide. More snow may be on way depending on new storm out in North west and how it tracks.
Might have to buy a snow blower this year.

 

Like said, it depends on a lot of different things like road conditions, weather conditions, personal health, distance, etc.

Perfect conditions, I chose 20* and below. I'll be honest, 32 is the lowest I have experience riding in, but that did not feel much colder than the 40 that I'm riding in now. I remember thinking tomyself that it's not so bad. I know I would ride in lower temps. I just love to ride. I don't own any heated gear, but I can deffinately see where it could help to extend your riding season.

Given the need, in perfect conditions, I bet we all could go lower.

Strickly comfort zone riding?... probably between 30*-40*.

 

I don't own any heated gear, and here in Columbus I mostly have to put up with the cold. Snow and ice, though it happens, doesn't happen that ofter and is not an issue for me - especially with the sidecar and its added stability, it'd still be the coldness that kept me in.

Hack

 

I rode to work this morning after noting a departure time temp of 27.1
40 miles one-way and took about an hour.
I deal withthe cold morningsbecause A) I get to ride and B) the flip-side is thehour ride back home today when it'll be near 50.

I have an ideal commute for a bike, about 7 miles of trafficleaving the office, the remaining 33 miles 2lane country roads with light traffic to the house.

This time of year has it's own pluses, listening to classical christmas music on Sirius, the christmas lights and the occasional smellof a fire from someone's chimney. It's a unique experience on a bike.

I've ridden in as low as 26, but could probably go down to 20 or so with the gear I have. Iwore every piece of cold weather gear today except thermal long underwear;my heated jacket liner, insulated pants, winter gloves, insulated boots, full face helmet and I was fine other than dealing with my shield fogging up.

Of course it has to be dry conditions, which we have in spades down here right now.

 

Any temp under 40 is too cold for me. My old saying (that I repeated endlessly for years) was "If I'm going to die on my bike, it's going to be in a flaming crash; I'm not going to freeze to death".

 

When it's too cold to crank... BUT.. I'm not going to do an Iron Butt at 20 degrees either. Stupidity has it's limits...

 

When I got to work this morning (20 mile ride) it was 26. That was the coldest day yet for me, but with my Gerbings jacket liner and gloves, I was nice and toasty. Now the guy that rode his Night Train was cold when he got here. I don't know how he does it with a half helmet and no windshield...

 

I rode from Wilmington, Nc to Fairfax, Va the week before Thanksgiving. Started out at 36 degrees at 3:00 in the afternoon, ended at 29 degrees at 11:00 that evening. No heated gear, but multiple layers of clothing, all encased by my raingear. Just think about Ralphies brother in "A Christmas Story", you'll get the idea.

Today was 36 coming to work, tomorrow is forecasted to be 29.

My vote would be as long as the road is dry, I'm on it.

 

Usually low to mid 30s is about it for me. Don't have heated gear and don't plan on getting any.
Ice and sand on the road is an issue in the good riding areas.

 

Since I have an hour ride to work, anything below about 28 is too cold. I never bought heated gear since I knew I was moving to Florida and now I shouldn't have to worry about have a "too cold" day.