It must be 8 or 9 years since I fitted my first pair af Shimano M515 pedals. These were the forerunners of M520's and apparantly were no good. Well that rubbish pair of pedals are still on that bike and have never caused any problems. Everypair of pedals I have are Shimano SPD's and none of them have caused me a problem. The same cannot be said for my mates that buy cheaper pedals that have to be changed every couple of years. Shimano M520's are not expensive- but they do last.