I think you need to look on the bright side here. You have purchased an excellent pair of tights, a real treat for yourself. I'm jealous!! OK they weren't quite warm enough on your ride, but a cheap pair of thermals underneath will sort that for you
With regards to the claimed temperature range - I think you have to allow a degree of flexibility. Do the quoted figures include wind chill? Some people are just different, some can tolerate the cold better than others.
Are they comfy btw?
If they are XXL (cant remember...) then PM me.
I run soooo hot you cannot imagine. Popped out in my bibs and some tights over (Nike running tights) and was sweating like mid August.
I baulk at some gear as I just know when it says 10-24 or some such, wont be cool enough in Spring or Autumn. WOuld look at yours as proper winter wear - as above - email or contact ASSOS. That price and reputation comes at a price for them..... (as well as you)
Good luck