Ok I posted in the for sale section that I really really need a dual belt alt pulley for cheap. I had someone PM saying they had one but it was an underdrive pully. Ok what exactly is the differance between regular dual belt and and underdrive? Thanks for the help

 

http://cgi.ebay.com/ebaymotors/MAZDA...Q5fAccessories

underdrive means the accessory turns slower, so has less output. not ideal for daily driven cars.

 

Karack,

Great signature.

 

^^ lol +2 for signature.

But yeah, what Krack said and duel alt pulley is going to be same diameter as the stock pulley. (Unless otherwise stated)

 

a larger accessory pulley underdrives that particular accessory (alt, water pump, PS, air pump)
a smaller Main driver pulley underdrives all the accessories.

the duel v belt alt pulley is purely to add a belt to reduce the slippage.

speaking from experience. underdriving your alt in any way will cause your car to eventually die if left to idle or driving in rush hour jams, especially if you have a stereo or run all your electrical components (like rear defog, heater motor and headlights on a cold morning)