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MG Midget and Sprite Technical - Fan belt lengths and part numbers

Hi

I am looking for advice on fan belt lengths and part numbers. What fits a 948cc MkII Sprite on a dynamo? Getting a bit confused on part numbers and my belt I bought years ago does not fit.

Cheers
Mike
M Wood

Mike
Belt numbers go like--
EG.

10A850--would be 10mm wide A section and 850mm length (circumference)
11V 1000--would be 11mm wide V section and1000mm long

Sprite belts are either--
11A 900 -- or
11A 815
I 'think' the shorter 815 belt is for the generator cars but not 100% sure which
willy
William Revit

Mike,
with my last experience with getting a fan belt my advice to you is not to get a generic one like the usual suppliers might provide you with.

The generic one I got last time was very slightly longer so took the adjustment to literally the very edge of the adjustment bar and the smell was extremely strong.

I got a Gates (brand) last time as I have it the past and was much happier with it.

IF your 948 is standard set for the belt then the Gates database goes against what Willy has put giving a 900 V-belt -
https://www.gatesautocat.com/drive/MG/midget/GAN1/9C-9CG/10-61_09-63/54550

Do bear in mind all databases have errors and omissions so do (try) to cross reference at least two if not more reliable databases (yeah I know, only lots of work, time and experience can establish this and then only reliable at that point so do your best).

Nigel Atkins

Sorry I meant to also put that there's an alternative on the link (that appears to need copy and paste) but again it's for V-belt and 850.

You could set the dynamo up at both extremes and put a tape or bit of string round and take measurements to give you an idea of the belt size you'll need, allow for the grove in pulleys so not spot on.
Nigel Atkins

Mike, before worrying about the length of your fan belt you should check the diameter of your dynamo pulley. It should be 92mm rim-to-rim. Sadly, the pulleys available from all major suppliers have a smaller diameter (74mm I think) and a jaw-dropping price to boot. They are suitable for Morris Minors but not Sprites. So with one of these small pulleys the correct length belt (for a Sprite) can seem to be too long - and if a shorter belt is used with the tacho dynamos and the small pulley, the tacho readings will be too high.

There is now an acute shortage of proper 92mm pulleys: they are very easily damaged (bent) by dropping or by owners trying to remove them by prying with a screwdriver or similar.

J.E. Davies

I just replaced the belt on my 948 tach drive generator. My parts guy gave me a 34.5 belt (maybe inches) . That was the listing in the Gates catalog. It was too short. Tried 35,36, 37 and 38. 36 was the one that fit. Don't know why it was different. 36 inches = .914, 34.5 = .876 so 900mm would be correct also.
J Bubela

Thanks all for the really helpful replies.

John, I have carefully installed the beautifully rebuilt dyamo with its correct pulley that you very kindly rebuilt for me recently along with the rev drive gearbox and voltage regulator.

I am slowly rebuilding my car back to standard and solving bodges I inherited - its old drive belt was too long/slack and my replacement seems too long too - the joys of having incorrect worn out parts, so no proper baseline for replacement.

Cheers
Mike
M Wood

Mike
Seeing as you have an old belt----an idea
Set the generator almost right in then cut your old belt and wrap it round the pullies- and then cut the end off to the needed length
Then take it off and measure the length of what you have and get a belt that size
You could also measure the width of the old belt, but just check if it fits the pullies properly as it may be worn and too narrow
You can judge by looking if it's worn as it will sit too low down in the groove
My earlier suggestion for a 11A815 appears that it might be for an alternator car with the smaller pully so possibly the 11A900
But
I just now contacted the guy I get most of my bits and pieces from and nearly always sends the correct parts and he reckons

BELT, FAN BELT
Part Number: 460-875 ; GCB10875

This would be 10mm wide and 875mm long

He also mentioned these cars had a 3/8" wide belt originally which is almost impossible to find and 10mm is as close as you will get

3/8" is 9.5mm so a 10mm belt would be more likely to suit better than an 11mm one

Sorry if I have mislead you earlier
willy
William Revit

This thread was discussed between 05/07/2018 and 07/07/2018

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