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Poly V Drive Belts


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Might save others some googling in the future, below is what I found out.

I was looking for a belt for a V2 Macro but I would think you could find just about any belt . Just read off the belt and reference below, the coding is pretty universal across the brands.

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For anyone running out of belt tensioning adjustment on a PJ Macro as I am (and I know George1966 is). It is possible to fit a 533J belt in place of the OEM 559J belt

The problem was that even with the adjuster cam at full extent , ie with the cam tensioning insert hole at 12 o'clock it was not possible to get the correct belt tension with a 559mm belt.

The next available smaller belt is a 533mm belt, so by rotating the cam by 180 deg you reduce the pulley spacing by about 15mm , so in theory a 26mm shorter belt (26/2=13mm) should fit., but it is that close that getting the Vs over the belt teeth isn't possible without actually removing the big pulley.

Here is what you do

1. Loosen and remove pinch bolt completely

2. Remove old belt

3. Very slightly lever apart the propshaft housing with a screw driver in between the clamping flanges and withdraw the large pulley and propshaft

4. Fit new 533 belt to big pulley

5. Then keeping the two pulleys almost touching slide belt over engine pulley, while reinserting the propshaft into the clamping housing . You may again need to lever the flanges very slightly to help you slide it in

6. Check belt aligned into the correct grooves.

7. Insert and just tighten pinch bolt

8.Insert a lever, I used a long reach Allen key into the tightening hole which will now be right down the bottom at 6 o'clock

Rotate clockwise to tighten belt, hold tension whilst retightening pinch bolt to 35Nm.

So we have the tightness, but I will reserve judgement till I try it. Because the pulleys are now closer together by about 15mm there is an increased belt angle on the bottom pulley that leads to about a 5% reduction in belt to pulley contact area, so that will make it a bit more likely to slip, but I doubt that it is that marginal. Especially as we now have plenty of tightening travel to make sure the belt is really tight.

I have discussed this with Parajet's Dan, who said there was nothing wrong in principle with using a shorter belt, if it fits.

I have found some slight variation in belt length from manufacturers. This belt is a Contitech 12 rib 533J from Simplybearings

http://simplybearings.co.uk/shop/Belts- ... _info.html



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