▁Racing ▁Class es . ▁Speed ▁R ally ▁- ▁world ▁r ally ▁cars , ▁production , ▁super ▁ 1 6 0 0 , ▁... ▁Ra id ▁- ▁T 1 , ▁T 2 , ▁T 3 , ▁T 4 , ▁T 5 ▁To ▁note ▁that ▁in ▁r ally ▁and ▁ra id ▁races ▁it ▁is ▁frequent ▁to ▁include ▁' dir ty ' ▁races , ▁e . g . ▁snow ▁or ▁d irt . ▁ ▁HO ▁Racing ▁Class es ▁H OP RA ▁and ▁U F H OR A ▁run ▁similar ▁classes ▁and ▁similar ▁rules ▁for ▁those ▁classes . ▁The ▁following ▁are ▁brief ▁explan ations ▁of ▁some ▁of ▁those ▁classes . ▁General ▁rules ▁specify ▁the ▁size ▁of ▁the ▁car ▁and ▁anything ▁else ▁that ▁per tain s ▁to ▁all ▁classes . ▁Super stock ▁( H OP RA ▁and ▁U F H OR A ): ▁C ars ▁may ▁have ▁at ▁most ▁four ▁magnet s ▁( two ▁to ▁drive ▁the ▁motor ▁and ▁two ▁" tra ction " ▁magnet s ▁for ▁additional ▁down force ). ▁All ▁magnet s ▁must ▁be ▁cer am ic . ▁Mot ors ▁must ▁be ▁stock , ▁and ▁may ▁be ▁bal anced ▁and / or ▁tr ued ▁( re ferred ▁to ▁as ▁" hot - stock "). ▁Mod ified ▁( H OP RA ): ▁Also ▁known ▁as ▁" cer am ic ▁modified " ▁is ▁the ▁same ▁as ▁super stock ▁above , ▁but ▁the ▁motor ▁is ▁un rest rict ed ▁and ▁the ▁ch ass is ▁may ▁be ▁sand ed . ▁Mod ified ▁( U F H OR A ): ▁C