Here’s my experience. I am running the Weistec s/c and for a while was also running a 170 mm Weistec crank pulley. At some point, belt shedding became an issue. The problem became progressively worse until eventually, the belt would shred within the first 100 km of driving. Tried a lot of things without success. At some point we switched to a 150mm outer ring. The result was the same.

I decided to replace the Weistec crank pulley with a brand new OEM unit. The result was exactly the same. The belt would shred within the first 100km of driving and usually when coming off the gas after a WOT run.

I then noticed that the inner belt was fraying and concluded that the two belts were colliding. As a test, I installed a 6 rib s/c belt and positioned it as far away from the inner belt as possible. That was probably about two years ago and I’ve had no issues since. While I have not diagnosed and/or addressed the cause of the problem, I’m no longer shredding belts and if using a 6 rib belt is resulting in a loss of boost, surprisingly this is not obvious from my data logs.

It it seems clear that in my case, the problem lay not with the Weistec pulley but elsewhere.

I have been shredding SC belts as well. Serpentine has been fine so far and have had no issues there. Less than 2000 miles ago, the full suite of UPD pulleys were installed including their BWK, all available idlers and a 77mm SC pulley. Accompanied with the pulleys install was wrapped Kleeman headers, K&N filters, new plugs/wires, PLM Heat exchanger, and a eurocharged tune. Everything was bone stock before and never had any belt issues whatsoever in stock form. Since UPD pulleys were installed, I can only get a couple hundred miles before SC belt shreds into spaghetti. Tons of belt dust gathers on the pulleys and engine bay before it shreds. The last belt was a stock length belt and we installed it and bypassed the BWK to eliminate that fro the equation. It hasn’t shredded yet but will soon as there is tons of belt dust gathering again and is only a matter of time. I believe the pulleys are all installed correctly and, other than the crank pulley, all pulleys have been checked and double checked and triple checked for burrs or imperfections. Nothing. As soon as a belt shreds, and before this last one shreds, I’ve cleaned up all the dust off of pulleys and elsewhere with brake cleaner ensuring the grooves of each pulley is clean and clear. I’m about to pull the belly pan and take a wire brush, brake cleaner, and scotchbrite to the crank pulley while it’s running to ensure that is not an issue. I’m lost as to why this is happening and the only thing that’s changed that could cause the belt issues is the “upgraded” UPD pulleys. I’ve emailed UPD and they have no advice or counsel. Shardul said maybe bad crank pulley but how could it be perfectly fine with the stock pulleys, then the UPD ones are installed and it all of a sudden the untouched stock crank pulley is suspect? I don’t think that’s the issue here. I’ve started my own thread on this issue, probably wrongly named the thread as New Faulty UPD S/C pulley destroyed. I’m not sure after research and troubleshooting that the S/C pulley or any of the other UPD pulleys are faulty, but I still have no explanation or solid working theory.
I hope that everyone that’s posted on this thread that has had experience with belts shredding will chime in here and state what the problem ended up being and how you corrected the issue. I’m lost and grasping for a solution as this pursuit of a diagnosis is maddening. Thanks all for your time.

it’s truly amazing to me that between, Mercedes, ourselves, weistec, renntech, multiple mechanics and UPD, that nobody can seem to resolve this. I get that there are many variables in the equation and one can’t be responsible for the other parts and then thirdly who installs them and fourthly other issues that are indirectly causing the issue. I get it. Anyways, I am replying to say a couple things: my issue of shredding belts began before my upd belt wrap and 5 pc pulleys were install and lastly, my issue was resolved. I wish I could answer how it stopped but I can’t. I did start going to a new mechanic and as stuff would break/ need service, he would fix it and then I noticed... no more belt speghetti for dinner. It was happening to many belts shredding and being thrown / walking off and now, nothing. I thought maybe it was the way I was driving but it was not. Hard... easy, didn’t matter. In reality and logically if a belt is being shredded, it’s either too small or coming into contact with something else. If walking off and or shredding like mine was, I think I had both problems of something not being aligned perfectly vertically to keep the belts in place and too small of a belt. My guy actually did math in front of me to figure out the correct belt size I needed for my setup. No issues since. (Well no issues with the topic lol)

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