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MG Midget and Sprite Technical - Early dual master cylinder question

My new Frogeye currently has drum brakes and an early master cylinder.
I'm going to fit my 1330 engine with the Datsun 5 speed box, which means that I'll need to upgrade to disks. I don't really w ant to cut into the car to fit the later Midget seperate brake and clutch master cylinders and was hoping to fit the Dual 3/4" disc brake and clutch mastercylinder that was fitted to early midgets with disc brakes.

A couple questions.
Do people here think that it will be up to the job?
Are all the push rods the same?
G Lazarus

Gary

Yes, 3/4 inch diameter dual master cylinder should be ok, with correct rear brake cylinders (1098cc Morris Minor, or later Spridget cylinders and backplates). Can buy good quality (AP Caparo) 3/4 dual master cylinders from Powertrack brakes.

Pushrod info (different length from 7/8 inch dual master cylinder): http://www.gerardsgarage.com/Garage/Tech/DbrakeUg.htm

See also:
http://www.gerardsgarage.com/Garage/Tech/DBrake/TandemMC_Part1e.htm

As MASCOT editor, why not dig out Alan Antead's articles on building a Sebring Sprite pedal box.

Did you sell Gaps in the end?

Cheers
Mike
M Wood

No. I currently own two frogeyes and an MGF. I collect the 2nd frogeye on Friday.
It has a dynamo, original Mk1 Sprite dials and drum brakes but is negative earth and is fitted with a 1275 engine. It also has a fibreglass front (but no bonnet hinge) which is held on with dzuz fasteners and pins.
It also has a V8 badge on the boot, which is the first thing to come off.
Photos on Friday.
G Lazarus

Hello Garry,

Felicitations with your “new” frogeye. Nice article, despite what John Davies says, I drive for > 10 years with the original ¾ main cylinder and standard disks. (you know my frogeye brakes well). The difference in force is 27%. I did not notice that because of the difference in set up. I had to change from drum to disks because on my first track day the drum brakes were instantly fading and consumed within an hour.
There are things you have to notice:
-Are you someone who likes to maintain or is it fire and forget till it does not work anymore?
-The Frog has a single brake system.
- Are the cylinders faultless? If not, go for resleeving, rust free cylinders and pistons.
- If faultless: Remove the valve (no 7 in the Davies article) in the brake cylinder.
-Use a small slave cylinder for the back drums and control the brake balance. (see Mike and the archive)
-Go for Mintex 1144
- Control the fluid level regularly.
-Change brake fluid every 1.5 years.
-Use new cunifer brake lines.
- Change all rubbers every 7-10 years.

I personally buy all brake parts at C & C parts; https://www.ccparts.nl/. Not because they are Dutch but because they have low prices and they mass produce everything by themselves. They have more than 250.000 brake parts in store and produce for others. It is a better product than standard. For instance, rust free pistons, with “German tolerances” safe rubber compounds and almost! rust free nickel cylinders. They can repair old parts as well. (their repair is not cheap but faultless)

Flip
Flip Brühl

Gary
I agree with Mike's set up suggestions, Its the same I have used for many years. Couple of other thoughts, I would use braided rather than standard brake hoses and you may have to change the clutch slave. I don't know much about the Datsun set up but on a 1275 ribcase I found the later 1275 slave gave a much more comfortable pedal with the 3/4" bore master and did not risk overthrow of the clutch.

Bob
Bob Beaumont

If you buy a new masrer cylinder make sure its an AP Caparo one and not a TRW unit. Another supplier of AP ones was David Manners but dont know if they still have them.

Trev
T Mason

Gary,

Picking up on a point in Flip's 'to do' list, and the article by Gerards Garage, if you start with a drum brake based master cylinder and want to use it with disc brakes, you need to remove the 'residual pressure' valve at the bottom of the m/c bore.

The valve to be removed is Item 8 in the picture attached:


Richard Wale

This thread was discussed between 06/12/2016 and 07/12/2016

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