Cycling Vest

Is a size 40 chest "for a jacket to ride a bike 44" chest for a t-shirt usually. (Is it not from what I believe is technically called "expandable stuff")?

In all likelihood not. I do not know if you're really talking about a jacket or shirt. Regarding jerseys go, you'll probably need a very large. If this is a European Cup race or you'll probably need a XXL. I found that the cycling jerseys made in the U.S. run comparable to the size of t-shirt. A great jersey to be a person wearing a t-shirt off. The European cut shirts need to go to one, sometimes two sizes (eg, XL, XXL). Since I typically covers a 42, I think you should go to XL for a standard jersey.

Hope this helps.

XL will be fine

Yes, stuff the bike is available, but if you stretch it over by buying a size too small, it causes a faster wear. Also in cycling controls things vary greatly. jerseys and shorts manufactured by European policy makers manage smaller. you may need to actually buy a larger size. So I would find a brand that I like and buy more and more because I know how I feel. usually buy down to 99% of the time. I know I need a jersey and shorts XL XXL, and I know how they will adapt.