Thanks everybody for your help, and especially to Patrick, I appreciate.
Finally, I've had the information by another way, and like confirm Patrick the maximum outer diameter of the Tork is bigger than the Castle motor: it's (approximatively) 48mm vs 42mm.
So the information provided on the HPI website (
http://www.hpiracing.com/products/en/100685/), the Towerhobbies website (
http://www3.towerhobbies.com/cgi-bin...?&I=LXWVC1&P=7) and probably other ones are wrong.
I hope this will help some other users to not make the same mistake than me. I'm actually trying to discuss with Towerhobbies and I've to say I'm very disappointed by their behaviour so that I regurlarly order to their company; in two words, I've realised (and informed them) the spec tech (OD) was probably wrong 2 hours only after placing my order and during 24h I've asked them to not send the motor (they answered me how to send back an item and thank me to do business with them ...).
Finally they have sent the motor and answered me they could not do anything (!). After many mails they have proposed me to offer me the shipping fees to send me another item (when I'll have send them back the Tork - it will cost me approximatively 30USD to send the Tork to US... + I've to pay the difference between the 2 items). Once again, I'm disappointed by their behaviour because I consider it's not completely my fault and because I've informed them very soon of the "problem". Anyway that's the first time I have to tell something "wrong" about them.
Thanks again for your help.
PS: yes english is not my native language (I've been discovered !), but as I posted to ask for something I've tried to use my best english !! (Moreover I don't post often, that's the less we can say (!) even if I read you since few years now and appreciate a lot your forum. I'm french.