Is the sizing of the jackets (Alpinestar in particular) the same as any other normal jacket or shirt? I usually wear a medium so I was thinking of getting a medium jacket, but according to the sizing chart, a small would fit me better. No one around here sells Alpinestars so I can't go try one on.

Thanks.

Unless you really can't help it don't just buy without trying it on. A jacket - (as with the boots trousers and gloves you should be riding with!) needs to be a perfect fit otherwise it'll be no good to you in a spill.

save your cash and get yourself a 1 piece suit, far cooler.

Go to any decent gentlemen's clothier and ask to be measured. Tell them what you are trying to buy. A leather jacket that you'll be moving around in. Tell them you want a bit of room in the chest and shoulders.

Once you get your measurements, call Alpinestar's customer service number.
USA Contact:
Email: customer.us1@alpinestars.com
Phone: (310) 891-0222

Europe Contact:
Email: customer1@alpinestars.com
Phone: +39 0423 5286

Tell them what your measurements were and tell them what jacket or suit or whatever you're trying to buy and tell them what kind of riding you plan on doing. This is the area that they are experts in, they will be able to recommend proper sizes. And if they don't, then you don't want to deal with a company like that.