Standard alternator belt size too long

[Moseley]

It seems I'm not the only person to have had issues with fitting the standard offering for alternator belts... Have bought an 11.3x912, but as can be seen in the photo, this is waaaay too long. I've tried pulling the belt tight with one hand to show how much it would ride out of the top pulley - I'd guess it'd fall straight off if I tried to use it.

The one that was previously fitted was a 10x900; I was under the impression that the longer length was compensated for with the wider width, but doesn't seem to be the case with mine. So what is different with my motor to other people's with alternator conversion meaning the standard belt is too long?

 

[sparkywig]

Are you taking all the shims out between the pulley halves and fitting them under the nut and washer?
I'm running the same belt and never had problems with stock pulleys, or a Berg Equalizer and stock fan pulley.

 

[Moseley]

I haven't actually tried nipping it up on the basis that even with the belt not tightened, it is only just sitting within the groove of the pulley. I'll try putting it together properly tomorrow, but I think I'll be able to pull the belt off the top pulley by hand, even with no shims installed.

 

[Moseley]

I haven't actually tried nipping it up on the basis that even with the belt not tightened, it is only just sitting within the groove of the pulley. I'll try putting it together properly tomorrow, but I think I'll be able to pull the belt off the top pulley by hand, even with no shims installed.

 

[Moseley]

It's hard to see in the pic, but just by tensioning the belt by hand, I can pull the belt to be about half protruding from the edge of the top pulley. Under the correct tension this is going to sit even higher. It's almost as if one or both of the pulleys are a smaller diameter, but I wasn't aware that different options existed?

 

[sparkywig]

Have you tried the old 10 x 900 belt?

Just a thought having noticed your crank pulley, is it the same diameter as a stock pulley? Some of the aftermarket degree marked pulleys are available in a "power pulley" version that has a smaller diameter than stock to slow the fan pulley down and so increase engine output (debatable)...

 

[Moseley]

Yep, old belt tensions up just fine with about 4 shims in place. The only reason I'm changing is because the belt is showing signs of cracking all over. Bottom pulley is 172mm outer diameter, and the groove doesn't look substantially deeper than a standard pulley, so I assume this isn't a power pulley.

I tried fitting up the 11.3x912, but as expected I can pull the belt on and off the top pulley by hand.

Are there different height alternator stands available for different fan shrouds? Or are there different diameter alternators available? My engine was built in the States, so not sure if they've got access to different branded parts over there that would affect belt size. It's got me stumped anyhow!

 

[megaaircooledvw]

Does it have a power pulley ,

 

[Trikky2]

Assuming the old belt has no reference number still visible, why not just measure it and buy a replacement?

 

[Moseley]

Assuming the old belt has no reference number still visible, why not just measure it and buy a replacement?

I think you skim read my first post - I have the details of the old belt, so no problem ordering a replacement. I'm just trying to get an understanding of what is different on this engine to others with an alternator replacement. Curiosity and all that...

 

[Trikky2]

Ah! The VW bottom pulley came in two different sizes. To start with they were the same as the beetle, then they introduced a slightly larger one for transporter engines.

 

[Moseley]

Hmm, well it certainly appears to be a standard 'off-the-shelf' replacement and the measurements seems to suggest this also. Guess I'll just have to compare with someone else's when parked up at our next show!

 

[dustrat]

Standard crankshaft pulley are all the same except early 36 hp engine. I suggest you get back to supplier of new belt and explain to them the problem as they have given you wrong belt.
Robert

 

[67 BAY]

had the same problem ended up using a 10 x888 belt

 

[sparkywig]

I'm having a similar issue with the current batch of alternator belts, I've gone through 5 in the last 6 months, and I've bought them from different suppliers.
Fit a new one and it only needs one shim between the pulleys, after a couple of hundred miles and readjustment it's almost too loose with the shim removed.
Drive another couple of hundred miles and it wants replacing again....
This has only happened in the last year or so. Nothing different with the engine and I've checked the pulley alignment.

 

[rlepecha]

I'm having a similar issue with the current batch of alternator belts, I've gone through 5 in the last 6 months, and I've bought them from different suppliers.
Fit a new one and it only needs one shim between the pulleys, after a couple of hundred miles and readjustment it's almost too loose with the shim removed.
Drive another couple of hundred miles and it wants replacing again....
This has only happened in the last year or so. Nothing different with the engine and I've checked the pulley alignment.

I have also noticed the new optibelts are slightly undersized in width which would be part of your problem Sparky..

I'm now using a premium branded(Dunlop in my case) SPA907 belt, it's slightly wider than the VW spec belt at 13mm but shims up pretty much perfect on my engine.
They're about £6 each on eBay, make sure you get a premium quality one (blue for Dunlop). The cheap ones (yellow dunlops) can have a bit of an inconsistent profile which causes the belt to go slack-tight-slack-tight as it rotates.


Won't fix the OP's issue with the belt looking massively oversized, a SPA900 or whatevers the nearest size to that may be about right..

Sent from my Swift 2 using Tapatalk

 

[Moseley]

I ended up buying a couple of 10x900 Continental belts from eurocarparts - my aim is to compare my setup with someone else's at the next show we attend. Haven't had the chance to do any real miles since fitting, and I'm not sure that such a skinny belt is ideal, but time will tell in that department!


Sent from my iPad using Tapatalk

 

[Guest]

I've had issues with new belts as well. I was on a long run last week @ 300 miles and 3/4 of the way home she died with zero charge in the battery. We fitted a new 'toothed' belt about 500 miles ago and i was able to turn it by hand with about 2-3 inches of movement right and left. (This was after adjustment and taking all the shims out as well). I was able to turn the belt loosely by hand. Moving the belt seemed to get the generator going after starting and got enough charge going to limp home after waiting 3 hours waiting on the RAC.

I immediately switched to an old non toothed belt i had sitting which was new but about 8 years old and the tension was spot on and no issues since. I know the generator belts are slimmer than alternator and i figure the belt i fitted had no marking but was the thicker 11 mm did the trick.

The only explanation for my issue was the new belt stretched a lot and i need to find some spares but cant be sure the same wont happen with a standard belt.

 

[sparkywig]

I'm having a similar issue with the current batch of alternator belts, I've gone through 5 in the last 6 months, and I've bought them from different suppliers.
Fit a new one and it only needs one shim between the pulleys, after a couple of hundred miles and readjustment it's almost too loose with the shim removed.
Drive another couple of hundred miles and it wants replacing again....
This has only happened in the last year or so. Nothing different with the engine and I've checked the pulley alignment.

I have also noticed the new optibelts are slightly undersized in width which would be part of your problem Sparky..

I'm now using a premium branded(Dunlop in my case) SPA907 belt, it's slightly wider than the VW spec belt at 13mm but shims up pretty much perfect on my engine.
They're about £6 each on eBay, make sure you get a premium quality one (blue for Dunlop). The cheap ones (yellow dunlops) can have a bit of an inconsistent profile which causes the belt to go slack-tight-slack-tight as it rotates.


Won't fix the OP's issue with the belt looking massively oversized, a SPA900 or whatevers the nearest size to that may be about right..

Sent from my Swift 2 using Tapatalk

Thanks, I'll try an SPA907.