[OXO cube]

hi guys 
advice needed 

i am having real trouble truing the softer rubber tyres
they are just ' chewing up ' when i try 
i have a 'TYRE TRUE' truer
the same as a  razor 
i run at low volts , slow speed and minimal amp usage as directed on many youtube vids 
but the tyres start to chew up and rip ?

any help appreciated ... i have ruined 3x sets of tyres so far , 1x thunderslot TYROO5RX and 2x NSR ULTRA 
my wallet will be truely grateful 

kev