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Brakes Q&As

YA Front brake upgrade

QUESTION;-
I saw in the Octagon Car Club bulletin that you said TD front brakes can be fitted to YA front back plates. I intend to do this modification. I have obtained 2 spare YA front back plates, 1 RH front TD back plate (to measure from), 4 wheel cylinders, set of brake shoes, 4 adjusters, 4 return springs, twin and single banjo unions, banjo bolts and banjo unions, copper washers, bleed nipples, link pipe nuts and pipe.

You might be able to advise me on were to fit cylinders on back plates, and how and where to couple-up hydraulic pipes, as they are different size pipes on the two cars.

 

ANSWER;-
I do not remember saying TD brakes can by fitted to a YA. It can be done but the only chap who carried out this mod has left the club. He said afterwards it was not worth the huge amount of machining required. To fit TD front brakes to a YA you will require the TD/TF/YB back plate, the TD/TF/YB stub axle (the wheel bearings differ so the stub axle diameter differs) and TD/TF/YB shoes and cylinders. Basically the two sysyems are very different. Converting to twin-leading-shoe really means a complete swap of bits. I’ll see if I can find his email address. The ‘gain’ is minimal in braking efficiency.

 

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Chris Pick I converted the full braking system on my YA to the YB/TD system during my full restoration of a YA. I can say through experience it was a very complicated modification due to the different drum sizes. Although I completed the mod successfully the amount of machining and welding required to change the backplates made it not worthwhile . As the pipe size on a YB and TD is 1/4″ you really need to change the master cylinder as well and then the chassis fixing is in the wrong place so you need to weld a new plate on to the chassis to accept the different master cylinder. You cannot safely just change the front brakes without changing the rear brakes as the braking ratios front and back will be different due to the different size piston diameters in the front and rear cylinders. And the rear brake plates are very difficult to change/modify. As an engineer with 40 years experience I can honestly say it is really not worth the effort. It is much easier to fit a remote servo to the original system which will make applying the brakes to full capacity require much less pressure and effort .


QUESTION:-

Fitting twin Leading shoes to a YA

Thanks for your previous advice on the front springs – I have fitted MGB GT springs (BHH1077) which lower the ride height by 1/2″ but are a bit stiffer. It is working well so far, next stop the anti-roll bar!

I have the opportunity to buy some complete MGA front hubs (with all links and steering arm) at a good price, this will allow me to have twin leading shoes on the front which is attractive BUT…. will they fit directly or will I need to modify anything?

 

ANSWER:-

The YA uses TC (Morris) hubs and stub axles. (With five studs.)

The MGA uses a standard BMC (Austin) hub on a different sized stub axle! (With four studs.)

You can fit tls (TD,TF,YB) brake cylinders onto your current YA brake backplate, but you need to be accurate when drilling the holes….. You ‘can’ fit MGA hubs but that stub axle will require some work, and you will end up with big 5 stud (16″) rear wheels and smaller (15″) four stud front wheels.

 

 


QUESTION;-

Master cylinder pitted

Over the past couple of years I have rebuilt the brake system at the wheel ends but as the brake pedal was slow to return a few week ago I took out the Master Cylinder and it was clogged up including the return holes so it was cleaned up and rebuilt with new seals. The bore was slightly pitted but I thought I would give the new seals a chance. Since then air has been getting in and the peddle has been getting lower and lower, just about got home from Wales. I had checked the fluid level in Wales and had not lost any. I have bled them and the pedal is up again. I can only assume the air is getting in
as the MC piston returns due to the pitted area in the bore. I have a spare MC but I thought I would just run this past you before I have it re sleeved.

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ANSWER;-

The pitting may have marked the seals so they now ‘leak’ a tiny bit, both to let fluid past and a bit of air in. Is the ‘return’ tiny hole clear just in front of the seal (ahead of the main feed into the cylinder)? When you return the pedal a little jet of fluid will squirt out of it. If it is blocked the fluid behind the piston cannot get out and the pedal sinks!