The castor blocks from FLM are very strong. Even if they do break, FLM has a great warrenty and you'll get another set for very cheap, if you even do break them. I'd suggest hinge pins from Lunsford racing. You can get a set here: http://www.lunsfordracing.com/mm5/me...Code=TRUC-TRST
I am sure you can get them from Tower Hobbies as well.
I just realized i bought the wrong caster block....it's for the nitro stampede i have the xl5 electric. I know i could get nitro hubs and run the tires that go with it but i just ordered rpm hub carriers...