HPI pinions are crap. Buy some of RCMikes hardened pinions.
No ! The new RCM pinions (black) are crap :( worst than hpi, I shread them in 6-7 batteries on my MBX5T... And I know many other guys having this problem with RCM pinions. Other RCM parts are just great, but Mike need to change his pinion supplier !
Inferno VE MMv3 NEU-CC 1515/1Y 4S "Flying machine"