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 Brake Drum Ventilation Holes
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MG Maverick

United Kingdom
889 Posts

Posted - 27/06/2018 :  21:31:02  Show Profile
I am fitting 12" brakes to our J2/4 project. What are the size of the ventilation holes in the brake drums I have seen on other examples ? Thanks.

Chris

J2353
J4129

powerplus

United Kingdom
482 Posts

Posted - 27/06/2018 :  22:50:32  Show Profile

Chris,
The brake drums on my PB have six holes, each of 2 inches diameter.
I cannot be sure that this was the “standard” configuration, but it looks good and has stood the test of time.

Powerplus
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Westbury

United Kingdom
578 Posts

Posted - 28/06/2018 :  08:31:58  Show Profile

Hello, Chris.

The size and number of holes for ventilation purposes in your brake drums has to be a personal choice so long as you do not make the holes so big that it seriously weakens the drum. In other words there are no hard and fast rules to be applied here.

Alan’s drums sound to be about right. You could try marking up one of your drums with various diameters and numbers of holes and positions until you are happy with it before doing any hole cutting. When done correctly the drums can look quite impressive.

Cheers,

Chris.
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MikeR

United Kingdom
73 Posts

Posted - 28/06/2018 :  14:55:15  Show Profile
Chris,

My J2 s/c has 12" brakes with six 2.5" holes and has given no problems.









Regards
Mike

J2 - J4351
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George Eagle

United Kingdom
2384 Posts

Posted - 28/06/2018 :  17:00:10  Show Profile
Drilled drums certainly look good but if ithe objective is to reduce weight why not fit Alfins which are much lighter?

I also wonder how much debris might get into the brakes, especially in wet weather.

I should have the Alfin fitted to the L2 shortly, they are currently being machined to reduce the wall thickness, where they sit against the hub, to 1/4 inch. This is to ensure a better landing for the washer/nut.

George
L2023

Edited by - George Eagle on 28/06/2018 17:05:14
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Westbury

United Kingdom
578 Posts

Posted - 28/06/2018 :  17:49:36  Show Profile

Hello, George.

I too have these Alfin brake drums to be fitted on my NA Leonard / Davis Special.You may find, like me, that I am having to trim the outer inside edge of the back plates because the drums are coming into contact with the drums. Hope you have better luck !

Cheers,

Chris.
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Westbury

United Kingdom
578 Posts

Posted - 28/06/2018 :  17:54:24  Show Profile

The drums are not coming into contact with the drums !! The drums are coming into contact with the backplates !!

Chris.
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MG Maverick

United Kingdom
889 Posts

Posted - 29/06/2018 :  07:42:51  Show Profile
Many thanks for your replies, Alan, Chris, Mike & George. I have decided to take Alans advice and go with 6 holes at 2" diameter, I am not aware of Alfins, but in with the parts in the Cyprus lock up were two 12" brake drums, very badly scored and non usuable. As most of the dismantled parts in the lock up were from Cottinghams J4129 I will assume that this J2 was upgraded to 12" and will replicate this.

Chris

J2353
J4129
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Westbury

United Kingdom
578 Posts

Posted - 29/06/2018 :  10:55:46  Show Profile

Hello, Chris.

I think you are doing the right thing by using 12” MG drums and 2” holes. I am only using the Alfin drums on my car because the car is a Special and therefore I think more acceptable. Generally, I am a stickler for originality. I must say though, the Alfins do look damn good !

Chris.
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MG Maverick

United Kingdom
889 Posts

Posted - 29/06/2018 :  11:18:00  Show Profile
Hi Chris, When you can maybe a photo or two of your special...and the drums. Sounds very interesting.

Chris

J2353
J4129
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Westbury

United Kingdom
578 Posts

Posted - 29/06/2018 :  19:33:47  Show Profile

Hello, Chris.

Thanks for that. I will send some pictures tomorrow off line as I am still not sure how to post pictures here.

Regards,

Chris.
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George Eagle

United Kingdom
2384 Posts

Posted - 30/06/2018 :  10:46:09  Show Profile
Chris - photo of the 12 inch Alfin drums which I will be fitting to the L2. They are currently being machined to reduce the wall depth to 1/4 inch in the area where they bolt to the hub

The drums are manufactured by Typecast Ltd.

George
L2023




Edited by - George Eagle on 30/06/2018 10:49:24
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Cooperman

United Kingdom
435 Posts

Posted - 30/06/2018 :  11:04:50  Show Profile
George won't you need four or have you a Morgan?

John Cooper M 628
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Westbury

United Kingdom
578 Posts

Posted - 30/06/2018 :  12:43:50  Show Profile

Hello, everyone.

Trying (again!) to post some pictures of my Alfin drums on my NA Special.

Chris







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Westbury

United Kingdom
578 Posts

Posted - 30/06/2018 :  12:47:57  Show Profile

Hallelujah!!

Yes, the brake hoses need changing. The car is subject to renovation and fitting of an NE tail in due course, also the IZ 97 Marshall blower to be rebuilt and refitted.

Chris
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Simon Johnston

United Kingdom
3078 Posts

Posted - 30/06/2018 :  16:52:14  Show Profile
Us J2 chappies don’t have to bother with such fripperies - we get finned brake drums as standard These are the splendid ones that Oliver Richardson did a few years ago.





Simon J
J3437
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