Supercharger belt size

[Lister]

Hi all

I will be fitting a -15% size s/c pulley and +2% size crank pulley next week and am a little confused about the best size of the serpentine belt to use. I've found this website which tells me that the stock size belt will be fine, however, I was under the impression that you should fit a smaller belt if you reduced the pulley size at all, even when fitting an over sized crank pulley.

If someone could put my mind at ease it would be appreciated, I really don't want a belt slip on my first run after fitting!

Cheers
Mike

[sam_a156]

I don't know if this helps, but I am running +3% crank pulley and JCW (-12%) S/C pulley with OEM belt.

[Lister]

Thanks mate, but is the JCW belt shorter than the stock MCS belt? . I'm assuming you have a JCW and not just a JCW pulley of course.

Thanks anyway mate.

[sam_a156]

My current belt is the OEM MCS belt...and yup, my understanding is that JCW belt is shorter.

[Richard Crofts]

A 15% with stock crank would require a shorter belt to help reduce potential for slip....although an OEM belt can be used (but is quicker to stretch and more likely to slip due to the reduce pulley contact)

With a +2% crank you will almost defo find that most reduced belts are too tight and that a stock OEM will be the best fit. Althougha JCW belt might be a good option if it is a touch shorter than a stock OEM belt (but longer than some other shortened serpentine belts.

Speak to roland at GTT and see what he would advice in terms of the belt (he does numerous JCW+3 and +2 and other belt and pulley and crank combos)

[Lister]

Cheers Richard, I think I will stick with the stock belt then. Good idea about the JCW belt, it may not be as short as the smaller aftermarket ones. I may still give GTT a call but you've given me the peace of mind I was after, thanks.

Mike