I am using plastic guards that cover knees and shins, like the ones displayed here:
My problem is, when I am riding, they sometimes slip down, reducing protection of my knees. This mostly happens because of vibration, while I am riding down (it's when I need them the most), but sometimes also when I am pedaling up.
If I fall down when my guards have slipped, it's as if I had no protection at all.
I noticed that on some days I get lucky with my straps and they sort of "stick" to my legs and don't move, while on other days I constantly readjust them, and they slip all the time.
How can I fix this problem?
I am willing to buy a different type of guards if that would solve my problem (however, I don't want soft/flexible guards - plastic has better protection).