underdrive pulleys? - United Bimmer Community

**jybute** · 12-18-2005, 03:21 PM

So, what do you guys think, I hear a lot of you talking about them on your cars, is there that much difference? What would you say the cost to performance benefits are? If any.

**c1apton** · 12-18-2005, 07:16 PM

Underdrive pulleys do exactly that...they underdrive the crank pulley. It is like using the smallest sprocket between the pedals of a ten speed bike. Easier to turn, therefore freeing up horsepower.
The trade off... all other things being equal... is that now you are driving the belt slower per each revolution of the pulley, so you need to use slightly bigger pulleys on the waterpump and alternator, or you will underdrive them at idle and risk not charging and overheating Unless you live in a climate that constantly stresses the alternator or cooling system, I don't think there is a down side

**Rooz** · 12-18-2005, 07:18 PM

they work and I have some, and yes you do feel/hear the difference

**devinwwu** · 12-19-2005, 01:40 PM

i'm pretty sure they don't make any for the 535i. you have to custom order them, my buddy had them on his WRX and it definitely made a difference you could feel

**jybute** · 12-20-2005, 08:21 AM

thanks boys, i guess its something to consider? devin, do you have them on your 535?

DEATH2000 · 12-20-2005, 01:02 PM

Yea man they are a great starter kinda mod. You will really feel a difference in torque, combined with an intake, there a great power increase for not to much money

**devinwwu** · 12-20-2005, 01:38 PM

no. like i said i don't think they make them unless its custom. i was just referring to the ones we put on my friend's old wrx

**c1apton** · 12-20-2005, 02:43 PM

yea they do - overdrive store.com for 92-95 E34s - $564.30 +ship. poished or unpolished.

DEATH2000 · 12-20-2005, 07:00 PM

damm those are expensive^^ Mine were $250 CDN.

**c1apton** · 12-20-2005, 07:05 PM

yea they are. It's because they have the market cornered on these. Not many E34 owners bought when car was newer

**jybute** · 12-21-2005, 09:35 AM

Quote:

Originally Posted by c1apton

yea they do - overdrive store.com for 92-95 E34s - $564.30 +ship. poished or unpolished.

why only 92-95?
my car has the m30 engine, what engine do those apply to?

**c1apton** · 12-21-2005, 10:35 AM

m50s.

**jybute** · 12-21-2005, 11:48 AM

damn...

**devinwwu** · 12-21-2005, 01:36 PM

that's what i was saying they make them for the m50 engine and others they put into the e36 but they never put the m30 in any other cars but the 5 and 7. these are not looked at as much in the tuner market so they don't make as much on the production scale in terms of performance parts.