Most importantly. I bought these. http://evs-sports.com/products/product_details.asp?prodID=58 They are 90% nylon and 10% spandex. My falls often mean sliding on concrete. Are they going to shred if I fall while wearing jeans over them? I've worn baseball sliding shorts underneath jeans and they tend to wear out quickly when sliding on concrete.
Can you recommend some concrete durable padded sliding shorts/pants? Preferably wearable in hot weather.
Once your exterior layer is breached you can't expect your underclothes to hold up for long. I think you would be better off looking into kevlar reinforced jeans or perforated leather pants if you can get enough ventilation. Some lightweight armor for the hip and thighs would be an added bonus.
I have slid on dirt covered asphalt for a short distance with high nylon content bicycle shorts and experienced some mild "road rash" (more like a severe indian burn) on the hip without any abrasion damage to the shorts. If jeans can't hold up to what you're doing, then any stretch fabric won't be much help.
