Could anybody give me their opinion as to why a SC belt would shred? I just had my second one go yesterday at Limerock, half way down the main straight! Limp Mode city.....

Last time was Labor Day last year at The Glen heading down into the boot.

Trackside service guy was telling me something about that at about 6500rpms and above belts can start to cavitate/vibrate off pulleys and then come apart. And yes, either this time or last year at the Glen (and if so, I miised it) the tensioner came down onto the pulley and it now has burrs on it. Is there a fix for this problem (belt shredding) other than not going up to near redline? Not gunna work on the track but I don't want this to become a habit.

Car has a 15% SC pulley and a 2% crank pulley by M7. The belt that shredded at the Glen was a shorter belt good for a 17% setup, not sure of the brand. That belt was replaced with a stock size belt from Napa as that was all that was available at the time. I did two more days at the Glen, two days at Limerock last year, multilpe autox's, and then this DE at Limerock before it blew again. Yesterday I replaced it with a Gates K060539 belt which fits a 17% setup. The car maybe had about 400 track miles on it and 1500 road miles on it before it went...

Is it the crank pulley it's slipping off or another?

Any suggestions would be appreciated.....

Thanks in advance..

 

is it on one side ? (pulley alignment)? or a nick in a pulley/sheave? most here change belt every year. tensioner stop from tsw is good way to go too . check your crank pulley and others for wobble .

 

I think we've found our smoking gun(s)...

 

maybe the fact that one of the pulleys has burrs on it has something to do with it

 

I run a 17% setup (17% pulley, stock crank) and I run the 19% belt... NAPA 060535

 

Sush - that is the same belt I got for my 16%. Will probably be a tight squeeze

 

that might be pushing it... I have an extra 539, and 535 at the shop... we will know which one is right by looking at your pulley tensioner under load...

 

You run them hard and they won't last. Lots of time at red line and a small pulley wears them down. I have to change mine every 2500, it usually shreds at 3000.

 

I'll bet, and would be almost sure of it, that your crank pulley is not in alignment. They do have a habbit of creeping outward.
Running a 2% and 15% is not an issue with the belt and 6500 rpm limit is not an issue either.

Hows the track looking at LRP? Getting bumpy yet? Was a hard winter with frost heaves all over the state.

 

LRP weathered the winter quite well. I didn't notice much of any bumps yesterday....

And I do think I hear the crank pulley (I'm assuming) making a little noise just off idle and then it goes away...I think I'll have Autotechnics replace it.

 

Don't think it needs replacing. Just have them pull it off, then heat it back up and make sure it's all the way on. I personally use a lock washer on the crank bolt. You should be good to go then.
By the way, you were'nt on the track "yesterday" were you? Maybe you meant Saturday.

 

Bob, check all the pulley grooves to make sure you don't have a small rock stuck in there somewhere...

...with the M7 crank pulley, if you remove the crank bolt you can see if it's flush against the crank or not...

...with belt length, grab a couple different sizes to see which one puts the tensioner in the right spot...

...the noise off idle is possibly the idler pulley if it's never been replaced.

Good luck.

 

Yes...I meant Saturday.

I believe it needs replacing, it's got burrs on it from something making contact with it - most likely the tensioner. If in fact a rock ended up in there (as Partsman suggested) sometime ago and damaged it, it still needs replacing anyway.

After watching some YouTube videos about tensioner stops I went down to make sure in fact that the black piston was still attached to the tensioner and it is. So I ordered a tensioner stop and another 17% belt as well.

The new belt is already damaged after 1 day!! Looking at it from above, the left side of the belt is frayed....crap! So I need to acquire a pulley removal tool as Autotechnic doesn't have one at the moment.

 

Gather you are a couple hours from me, but I have the tools if you feel like taking a drive. Just bring up the pulley and we can do it here.

Anyway, the tool is not too bad in price. See what Partsman can do for ya maybe.

 

Wow.....thanks for the offer. Could you be available on Sunday? I don't want to put you out or anything but right now that's my only free day coming up. Friday and Saturday I'll be at Limerock helping crew for a friend running a PCA club race and I'll need to get this done by Thursday of next week as I leave for The Glen early Friday morning.

I just talked with Peter at M7 (nice guy!) and I ordered another pulley and it should be in hand on Wednsday. I already have the tracking number. He also suggested using the JCW belt as it's more suitable for track environments as well as being a bit shorter, which I need.

If you can't do it this weekend I can just get a day off work and be available early next week.....Let me know. If it's not possible to get together I'll just need to know ASAP so I can make other arrangements.

Bob

 

PMed ya.

 

Thanks a lot for fixing me up today Greg! I can't believe that bolt was missing...

for Onasled! Man, how great is the MINI community...

 

so what was the fix?? sounds like whatever was causing your problems you and onasled got it straightened out.....curious. i've been running an alta 17%/stock crank for almost 30,000 miles so far soo good but im going to be changing the belt this summer......got any heads up tips for us?

Thanks,
Steve

 

Bob's problem is not that uncommon. Whenever you put the aluminum pulley on the steel crank, the chance of it coming loose is increased.
Bob arrived with a missing crank pulley bolt. During a track day, which is usually when this happens, his pulley backed out a touch and became misaligned, in turn destroying the belt, in turn destroying the crank pulley due to the tensioner pulley crashing down on it.
I've seen this before, almost exactly the same circumstance. It was me that it happened to. VIDEO HERE

Anyway, just something to check every so often if you have an aluminum pulley. If you've had it on for a long time and have had no issues, then chances are you are OK. As we found out this weekend, some fit tighter then others.

Kudos to Bob here for having one very beautiful and VERY well kept Mini. My son fell in love with his car, and it was a pleasure to work on.

Also, Thanks really go to Paul Mello here too. He's always a huge help in my shop.

 

Definitely, thank you as well Paul! You two guy's made quite a team with your expertise....Also, thank you Paul for the lift to the parts store and conversation when you weren't helping out Greg with the install.

I'll let you guy's know how the Glen goes this weekend...

 

Isn't the MINI lifestyle great !

 

so the whole problems was basically because the 2% crank pulley backed out and became misaligned? That's good to hear cuz I have the stock crank pulley dampner and plan on keeping it that way

 

Apparently.....I'm guessing that I'll be over checking that bolt from now on!

 

cool man, well sorry that you had to go through all this, but thanks for finding out the cause of the problem and what fixed it. Great heads up for the rest of the community. Many thanks

Steve

 

What size lock washer did you guys settle on?