Alternator Belt size?

[robertb]

I have a 79 930 and the 10 x 710 belt seems way too tight. I have all of the shims on the inside of the pulley and still too tight, I am missing 2 shims, I only have 4 so don't know if 2 could make that much of a difference but I don't think so. I tried a 29 inch belt which works but is too loose with all of the shims on the outside.

So tomorrow I'm going to buy 2 more shims and a 10 x 725 belt which I think will fall in between a 29 inch and 710 (I think 710 is approx 28 inch and 725 is approx 28.5 inch). Why would my belt be different? Seems almost like I have a normal 911 pulley on there. Is the 930 crank pulley smaller than a regular 911? Wouldn't you want the 930 pulley to be bigger than the 911 for more cooling?

Car is also a European model, don't know if that would make any difference.

[robertb]

Well my car uses the 725 belt even though supposedly its supposed to use the 710. Guess it's either a weird grey market thing or someone put on a different pulley at some point. Guess I won't worry about it.

[quattrorunner]

Mine is too long and has all shims inside. Is it possable the pully is worn or did autozone sell me a balt that is too long? I mean sometimes squeeks when the lights are on and i blip it.

[robertb]

if it's too long you want all the shims on the outside so the pulley half will snug up against the alternator as close as possible and push the belt as high on the pulley as possible and tighten, I believe you should have 6 shims.

If you are using a belt from autozone it is most likely going to be in inches so probably not going to be quite right because when I went to the auto parts store (checker, autozone) belts were only available in .5 inch incriments. To get it perfect I would buy the 710 mm or the 725 mm, not sure which your car uses but it should be one of those.

[NathanUK]

The less shims between the pulley halfs the tighter the belt will get.