TMS Pulley issue

The alternator pulley is the heaviest of the 3. It's made from brass and extremely heavy. The TMS pulley is much lighter, I'd keep that one. I rarely know what I'm talking about. Take this with a grain of salt.

Originally Posted by Rob43

Ice, & whoever else;

I'm just not a fan of changing out the alternator pulley, If there's any gain at all, I doubt it could be measured. The down side though is bigger, your Bimmer might not like you messing with its voltage requirements, that's why half of the manufactures don't even make an alt. pulley in the first place.

Edit: I need to be more specific, if you buy an under drive pulley kit that comes with an alt. pulley, my thoughts are to buy one with the stock size. As in an alt. pulley that is not under driven, you'll get the reduced weight, but it won't mess with your electrical system.


Good luck.

It's BARELY smaller than stock and a little lighter. My alternator has already started to "whine" but it was making noises before.

My new alternator pulley is larger diameter than stock. (It was also taller than stock but that's been fixed.) I thought that was the point of an underdrive accessory pulley, no?

Ya a smaller pulley would over-drive it. Which I doubt they are doing. More likely its the same size or the pulley Iceman got is definitely intended for another alternator which may have a slightly smaller pulley.