I hate two things in car modelin': the clear parts ( always too thick ! ), and these pesty tyres mouldin' flashes...!
A good trick before to start sandin'...Put the tyres in the freezer durin' a couple of hours to cool and harden them: it 'll makes the sandin' easier...!
And if it doesn' t work, try a more radical approach: cast the whole tyre set in resin...!