X308 XJR Supercharger Belt – Single or Double Sided

[Al Murphy]

Hello.

I am replacing the supercharger belt on my XJR after the auxiliary (FEAD) belt decided that it wanted to shed some weight. My car is a 1998 and I’m struggling to confirm what belt I should have on the supercharger. The various parts sites, and Jaguar themselves are suggesting a part number of NCC 7740 BA based on it having all metal pulleys. The service history for the car has a bill a few years ago for an ‘uprated pulley and belt using latest generation parts’ which I assume is the change to metal pulleys. However the belt that has been removed is ribbed on both sides and as far as I can tell the belt ordered is single sided. I’m due to collect the parts this afternoon but would like a sanity check!

All the supercharger related pulleys are grooved except the tensioner which is metal, but smooth. It has stripes worn onto it, I assume from running a double sided ribbed belt.

Has someone put an old spec, double sided, belt on a later spec pulley set up?

Thanks,

Al

[P700DEE]

The original belt is single sided

[Piersman2]

It's a bit confusing becuase the original pulley/belt set cannot be purchased anymore, it was superceded with an upgraded set of components a few years into production.

I had similar when I upgraded the Superchrger pulley on my XKR, I couldn't find anyway to make sure I was buying the correct sized belt. As it turned out, the belt which was fitted to my car was too long when I had the new S/C snout fitted, and I speculatively ordered a standard belt onine from SNG's which seemed to do the job, it was single sided. The old belt had been double sided.

But I ended up with 1 pulley where it had 'teeth' running on the smooth side of the belt, so the other way round from yours!

Best of luck.

[Al Murphy]

Piersman2 how long did you run a single sided belt on a grooved pulley for and were there any consequences? It doesn't seem right to me but that's the situation I am in.

This is the belt removed, no part number or marking on it;



and the replacement bought from Jaguar after checking;



Having checked the belt run last night it's going to have the smooth side of the belt running over grooved wheel on the idler, and the ribbed side on the smooth wheel of the tensioner!

That can't be right?!

These are the stripes left on the smooth tensioner from the 2 sided belt;



Can anyone confirm whether theirs is the same, or if they have managed to order a 2 sided belt?

Thanks,

Al

[Piersman2]

Al Murphy said:

Piersman2 how long did you run a single sided belt on a grooved pulley for and were there any consequences? It doesn't seem right to me but that's the situation I am in.

This is the belt removed, no part number or marking on it;

and the replacement bought from Jaguar after checking;

Having checked the belt run last night it's going to have the smooth side of the belt running over grooved wheel on the idler, and the ribbed side on the smooth wheel of the tensioner!

That can't be right?!

These are the stripes left on the smooth tensioner from the 2 sided belt;

Can anyone confirm whether theirs is the same, or if they have managed to order a 2 sided belt?

Thanks,

Al

I did find a website in the states where you could pick the length and width of the belt you were looking for (gator belts , or something like that) , and they did have a UK supplier so you could measure your belt and get it from the UK, my main issue was finding a slightly shorter belt than the one that was on the car to make up for the slightly smaller pulley on the upgrade snout I fitted.

However, I was happy enough that the tension in the standard belt was ok and decided to risk the smooth side of the belt running over a ribbed pulley. It left some marks in the smooth side of the belt as you'd expect, but they didn't get passed purely surface rubbing in the few thousand miles I put on the car after that before I sold it.

I wouldn't worry about it too much, if the belt you have has a decent tension, just stick it back on, or use the new one. The S/C belt is not doing much else except driving the S/C snout. So so long as you have the grooves on the belt in the grooves of the S/C for max grip I don't think the rest are going to matter much.

Just keep an eye on it for a few thousand miles until you're comfortable it's not going to disintegrate. I stopped worrying about mine after about 2 weeks!

Worst case scenario is the belt breaks and you lose drive to the S/C and a bit of power until you get a new belt fitted.

[Zippyworld]

Give David Manners a call, I remember vaguely having several conversations regarding belts on these. They were very knowledgeable on this subject, forgotten the guys first name but his surname was Holmes? Pretty sure my Supercharger belt is double sided, not here to look at right now.