Alternator belt jumps?

K9ng

New Member
Hi, I have an annoying problem where the alternator belt jumps at anything over 6.5k rpm have bought a second hand crank pulley problem still there :doh: I was thinking maybe to get a lightweight crank pulley, any ideas if this would be a good idea?
Whats peoples views on the cdf racing ones? Do they munch through the crank seal??

I have also changed the alternator pulley problem still there!

It may seem trivial but annoying when your tearing round a track and have to think about the poxy belt coming off :roll: It tends to jump on both pulleys crank and alternator one.
And can sometimes completely come off!

Any advice is much appreciated.


TIA
 
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Paul20

Member
do you still have air con or not? i had that problem when i removed the air con pump and used a replacement 4rib belt. it just kept jumping off at higher revs and shredding itself so i sourced a 6rib belt instead which gives no problems. maybe worth trying
 

Fast Guy

Moderators
Staff member
Either the belt is too slack, or one of the pulleys is out of true, wether a badly fitted alternator or whatever.
 

K9ng

New Member
I originally had a 6 rib and it used to do the same, but I haven't tried
a six rib since fitting a different crank/alternator pulley. Might give that a go again.
I have had a straight rule against both pulleys and they are in alignment :roll:
 

Paul20

Member
like fastguy mentioned, its probably just a tensioning issue. i thought i put quite a generous tension on my 4rib belt and it still got tangled up. atleast with a 6rib belt, it can be tensioned a bit more conservatively without it slipping
 

nitrosgti-r

New Member
i have had the same problem and been through about 8 belts, 4 guage and 6. iv tried lightweight pullies but had to change back to standard cos of the outer lip the standards have to keep the belt from slipping right off. I ran a rule accross the crank and alternater pully and the alternater pully was about half a mill back towards the engine so i took off the alternater and got a brass sump plug washer and filed it a bit and refitted the alternater pully and, touch wood, its done the trick!

do a search :)
 

fubar andy

Moderator & N/W Rep
Staff member
I’ve had my belts frayed over a few years. After having a Forge (brand) lightweight pulley on, the actual metal deformed and over a period of time it notably wobbled when on tick over.
This caused the alternator belt to fray and in the process take the power steering pump belt with it!

After some help I was pointed in the direction of CDF-Racing Performance Parts, they make lightweight crank pulleys for the GTiR.
So far so good on mine and I’m happy with the manufacture than the softer Forge ones. No fraying of belts in anyway or do I expect it to.
From what you said in your post doesn’t sound that similar to my previous issues, but it’s always worth covering just in case!

I think Mr “FastGuy” also has a point(s) about the belt tightness and perhaps the alternator.

Check the belts are specific for your car, make sure they are tight and whether it has aircon or not.
 

K9ng

New Member
Thanks for the help guys will try tensioning the belt some more and a six rib belt.
will also double check pulley alignement. Will let you know how I get on.
 

red reading

Active Member
speak to carl at motorworx he has had some taller side pulleys made for himself and i and i'm sure he would point you in the right direction
 
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K9ng

New Member
I have the taller side alternator pulley, it was my friend Geof who got them made for us. I will try a different belt and see how that goes.
 

Fast Guy

Moderators
Staff member
I have the forge pulleys on as well. Can't say had a problem with them or the belts coming off. I have a 4 rib fitted I think.
 

red reading

Active Member
yes the pulley, also check the mounting bolt's and brackets as they could be loose or bent if thing's have been over-tightened
 
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