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Swapping my Brake system from Single to Twin


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Hi all,

My current series IIa has the single line none servo brake system on, I've just been able to source a complete dual brake system complete with the brake failure switch etc.

I'm looking at replacing the current single line with this dual line brake system to hopefully gain some extra brakes ;)

My main question is will I be able to swap the old system to the new one, and will I need to do any modifications?

The front brakes are the 11" twin off a series III and the rear are the standard ones.

I've also got a chance to get the complete rear axle which has the 24 spline and has a circlip attached to the half-shaft, are these stronger then the standard 10 spline?



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Don't bother with the brake failure switch PDWA - makes bleeding even more awkward.

Did you get the servo, pedal box and pedal too?

Make sure you change the rear slaves, they are the same as the current 10 inch fronts which have a larger bore.

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It is a good modification. My 109 stops better than my Eurobox.

What I'd suggest is that you'd invest in a brake flaring tool - the one from Laser is adequate and inexpensive.

A selection of imperial and metric male and female fittings will allow you cope with the different threads you may encounter. Some copper pipe allows you to replace any steel pipes that may be dodgy.

Replace the hoses as a matter of course.

Adjusting the layout of the front brakes to that recommended by Les Hanson makes bleeding much easier.

Bring the pipe from the hub hose mounting bracket to the LOWER cylinder, another pipe from the LOWER cylinder to the TOP cylinder, and then put the bleed nipple on the TOP cylinder.

The Pressure differential Warning Switch is not a major bonus, and does add to the difficulty. But it is possible, especially if you use a power bleeder Gunsons Easibleed for example. Over to you. I'd fit it, I like the little light!

As for the axle, if it is a salisbury axle then, yes it is MUCH stronger. But a 24 spline rover axle has the same 2 pin differential design, and so is only marginally stronger. I think the differential is the same 10 spline design, only the outer end changed. By the way the salisbury needs modification to be fitted to a SWB.

Best of luck,


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  • 3 weeks later...

Thanks for the tip's.

I've now connected the brakes but have found a problem with the clutch pipe.

When I came to attach the pipe to the hose they have different fittings, the hose is new from Craddocks number RTC 3386 but the pipe from the clutch cylinder is a large type (Not the same as the brake pipes).

Is there such a thing as an adaptor available to allow me to connect my new hose to a standard 3/16" pipe and then to the clutch cylinder?

My current gearbox is a series IIa not a series III, which makes me thing there is a difference between these hose/pipes....



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The clutch system is run in 1/4" pipe.

On the master cylinder there is a 3/8" UNF bore, into which screws an adaptor which takes it up to 7/16" UNF. A standard fitting for 1/4" pipe is 7/16" UNF, much in the same way that 3/8" UNF is the standard (imperial) fitting size for 3/16".

The clutch hose is 7/16" UNF, and two standard female fittings will fit on it.

The slave cylinder has a 7/16" UNF bore for a standard male fitting.

The reason I know this is that I recently sorted the clutch arrangement on my Series III, this is the setup for later Series IIIs and all 90/110 etc. onwards. Older vehicles had a master cylinder with a separate reservoir, and this one had a 7/16" bore.

I toyed with the idea of using 3/16" pipe, but I decided to do it the proper way in the end. They must have used 1/4" pipe for a reason, plus it makes the plumbing easier.

If you need the adaptor piece to go into the master cylinder, it's part number 139082 and you'll need a sealing washer 233220.

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