so i have a pearl izumi jacket and a pearl izumi long sleeve jersey...the jacket is a sazie large and the jersey is an XL when it gets really cold, like below 30ish, is it defeating the purpose if i wear the jacket under the jersey? The jacket wont fit over my jersey..

That's a little like wearing your underwear over your pants. A windbreaker jacket isn't going to feel very good against your perspiring skin, or breath well with a jersey over it. Get a proper sized jersey.

Try underarmour cold wear when its that cold. The stuff works GREAT!

I can't imagine that would be very comfortable. It wouldn't be so much like wearing underwear over your pants, but more like wearing your splash pants (wind pants) under your shorts.

I'd recommend getting clothing that fits ... or perhaps drop 5 lbs.

I've worn jerseys over (true winter, not just wind shell) jackets but just for kit appearance (team jersey over generic jacket). It's sort of like wearing a color vest over a t-shirt in intramural sports. Yes, functionally you're defeating the purpose of a wicking, breathing, not-so-insulating jersey, but if you want to do it, do it.

I've worn, and will wear, a vest under a jersey, instead of sticking a plastic bag up my jersey. I do this regularly actually since I have vests I don't want to show but they work well for wind protection.

If you have a SS jersey, wear that under your jacket. A well insulated, nicely wicking jacket works great with just one (wicking) layer under it.

btw I have no long sleeve "wind shells". After lots of experiments I've settled on:
- winter jacket with soft cuffs and neck area, windproof in front
- clear rain jacket (for rain but also for cold windy days)
- wind vest
- regular SS jerseys
My deluxe kit (i.e. I did this only when I had way too much money to spend on kits) includes thick and thin LS jerseys which work well in a very limited range of temps.

cdr