I installed a 15% supercharger pulley today. I slipped on a new belt as well. After I had everything put back in place, I started up. Nothing happened. I panicked until I realized I didn't reconnect the ground wire. Oops I reconnected the ground wire and started it up again and everything sounded great. No weird noises no bad lights. Then I went around to look at the pulley and I noticed that the belt was about 1 mm over the edge of the pulley. The belt was perfectly set on the crank pulley, the alternator, the a/c but was off a bit on the tensioner and supercharger pulley. I expect that is not a desirable thing. I got out the belt adjuster tool and pushed the belt over. I started it up again and the same thing happened. I adjusted the belt one more time. Same thing. The belt hung off about 1mm just over the outer lip of the supercharger pulley away from the engine.

If this is truly undesirable, how do I figure out what's wrong? How do I fix it? If it doesn't matter or it will just go away then I'll shut up.

 

What combo are you using? (is it stock belt?... what brand is the pulley?)

 

My belt hangs one tooth too far away from the s/c - it's been fitted and re-fitted (by bmw both times) and still does it. I've given up stressing about it...there seems to be no damage occurring...

it's a promini pulley and a Aussie made belt...the belt sits fine on all the other pulleys...

It is a bit annoying though......

 

I'm using a stock-sized Napa belt and an Alta pulley.

 

I've got a WM Pulley (same theory as the Alta) with a gatorback belt but never had this problem, the reason I asked what you were using is, as stated on Alta's website,

"[FONT=Arial][SIZE=1]Other non-press on styles force YOU to determine the correct pulley position on the shaft. Make a mistake and expect a costly tow to a service center for a belt replacement. Our self-centering design prevents all of those hassles!". [/SIZE][/FONT]

I was going to say that if you had a pressed on pulley, it's location might have been messed up during the install on the shaft but I would think it's hard to put an Alta to far onto the shaft. As long as you followed these instructions (thanks Webb Motorsports!), I can't see how it would get misaligned.

"For the Alta or RSpeed: Take the hub center and slide it ALL THE WAY ONTO THE SHAFT. Then place the pulley over it until it stops making sure to keep the bolt holes aligned. Now use a drop of red Loctite on the bolts and torque them in a cross pattern."

Let me know if you find the issue, sorry I can't help more.

One more thing.... This might be a dumb question but I just want to make sure I'm on the same page here: when you say it is 1mm over the edge, do you mean that the ribs on the belt and the grooves on the pulley are out of sync? If they are in sync and it hangs over by 1mm, you don't have a problem.

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They are in-sync but it hangs over.

 

I also have the Alta 15% pulley on my MCS. The belt fits the pulley the same way you describe. I was a bit worried at first, but after 5,000 miles I'd say it's a non issue for me. I'm using the original OEM belt.

 

you could check all with a straight edge. this will either freak you out or make you sleep better.

 

As long as all the grooves in the belt mesh with the all grooves in the pulley, all should be fine.
If not, I would attempt to re-seat the pulley & try again.
Watch your belt fanatically in the meantime.
Peace - bodinski

 

It is the missing information that sometimes holds the key to wisdom. After putting on the SC pulley, I thought I would also change out the crank pulley. I used a (relatively cheap) harmonic puller and managed to strip the center bolt while pulling. So, I decided that I had better get a sturdier puller. Since it looked like I hadn't budged that pulley a bit, I bolted it back on and buttoned things up. Well, I finally got the new crank pulley on and - guess what - the belt's in perfect alignment. I must have budged the crank pulley a wee bit before I stripped the bolt and caused the belt misalignment.

Let that be a lesson to me.