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Wales
by Joske Vermeule, September 1
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Forums39
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Jun 14th, 2026
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Joined: Jul 2016
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OP
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In talking to the dealership, apparently the actual specification for drive belt tension is 50 Hz. You tap it with a hammer and use a device to measure how much it vibrates after that. Uh--not a device I've seen in the U.S.
Another way is to set it just tight enough you can just barely turn it 90 degrees.
Yet most belts are set using an offset measurement at the center of the belt. For example, when set properly, you might be able to deflect a belt 13mm when pressing on it between the two pulleys.
I'm reasonably comfortable with estimating "tight enough" but would welcome if anyone has a more precise, repeatable measure of appropriate tension.
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Joined: Mar 2015
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I have owwed several cars in the past that have had timing belts.
The test has always been a 90deg twist along the longest length.
That should be fine.
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Joined: Aug 2011
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There is quite s bit of chat on this matter at the link below. Mark Evans from the factory involved with his take on how to.
Re: Bevel Box Noise Survey. Page 14
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Joined: May 2011
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Talk Morgan Enthusiast
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This is similar to what they use at the factory to set the belt tension: http://www.gates.com/products/industrial...and-accessoriesIt does seem to result in quite a tight belt at 50Hz and I run mine slacker than this, about 20mm deflection in the belt.
2021 M3W
2013 M3W - Sold
1971 4/4 2 Seater
1934 Sports
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20mm seems like a good idea. I've encountered many smaller belts that use 15mm. 20mm seems tight enough, yet conservative to protect the bearings.
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Joined: Feb 2016
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Needs to Get Out More!
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Needs to Get Out More!
Joined: Feb 2016
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I have owwed several cars in the past that have had timing belts.
The test has always been a 90deg twist along the longest length.
That should be fine. Mine was factory set and checked by dealer to 30° twist. Still the same after 2000+ miles.
Richard
2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone
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Thanks. I've got the feeling that there is a reasonably broad range of acceptable tensions between too tight and too loose.
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Joined: Nov 2013
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The Morgan PDI form says "Drive belt tension (1/4 of a turn) & clear of the tyre". That was 2013 & recommendation may have changed since.
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Joined: May 2012
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Supermax recommend not to over tighten, if it doesn't slip a tooth it's ok. Mine has about 20mmm deflection.
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