BGRS 4AGE 16V Underdriving Alternator Pulley brand_toyota This will allow the emergency BRAKES This will allow the emergency brake to not engage when moved into the up position These tensioners are recommended to be replaced every other timing belt change but we like to replace them any time the belt is off for maintenance as it is cheap insurance It's worth noting that we haven't seen much of a voltage drop except for at idle in our own measurements with the Race alternator pulley We haven't verified this ourselves but it would make sense that there is less drag from friction and electromagnetic drag at speed since the alternator is kept in a more efficient operating range