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Pearl Izumi Elite Thermafleece Cycling Tight

When winter arrives, tights become mandatory. My knees do not like the cold, especially under torque, and pushing cold knees hard is a sure way to damage the cartilage over time.
The Pearl Izumi Elite Thermal Cycling tight @AMAZONkeeps my knees warm down to about 48° F. Colder than that and I move to the Pearl Izumi AmFib tight along with a shoe cover.
Built in short?
I prefer the tights that go over regular cycling shorts (as opposed to those that have a built-in short) so that I can layer or unlayer as the temperature changes.
How warm?
Serious riders should have one lightweight tight, one medium weight tight, and one wind/water resistant warm fleece tight.
Tights are also very useful for other activities, but get the cycling tights, because they work for everything.