Brake servo and master cylinder assistance required

[chillidoggy]

Hello everyone, this may be bit of a long shot, but.............

 

Although I no longer have a Triumph car (the Stag was sold a long time ago, sob!), I have a Dax Cobra that uses a lot of BL parts in the braking (MGB), steering and switchgear department. I have been looking to improve the braking performance for some time and wonder if anyone could give me some information about the Sherpa servo and master cylinder that seems to crop up here from time to time, as I think it may be a suitable upgrade. The main problem is one of effort, rather too much effort required to stop the car! The problem has been exacerbated by the very high performance engine which has a large overlap camshaft. There is an electric vacuum pump available from the States for just this eventuality, but I don't want to go down that route just yet if the solution is closer to home.

 

My car has Jaguar XJ6/XJ12 calipers, four piston at the front, and currently uses the post-1978 MGB tandem master cylinder (GMC164) and servo (BAU1016) , which has about a 6" diaphragm. The master cylinder bore is approximately 19.8mm (best I can measure with my eyesight).

 

I have a bit of room for a larger diameter servo, although not too much, and would be interested in any information possible, such as the Sherpa master cylinder bore, whether it has two or three ports (the MGB cylinder has three, two for the front, one for the rear), and the Sherpa servo dimensions.

 

Any part numbers would also be a great help as I could then research to my heart's content!

 

Cheers,

 

Ian.

[Guest Wayne S]

I dont know about the Sherpa servo but I am just about to marry up a Rover SD1 master cylinder and servo to a pair of Jaguar XJS calipers on my Grinnall.

 

I'm told thios system works well and was a popular upgrade for Rover SD1's back in the day (my Grinnall uses SD1 front hubs and struts).

 

I dont know what the bore is but the servo is fairly huge also it has 3 ports 2 front one rear. Its most likely with the Dax as with the TR you will have to cut and re-weld the pedal attachement as they are too long to make room for the thick bulkheads on Rovers.

 

Wayne

[hrgserv]

Have a look at the range rover/discovery mk1 servo and master cyl its approximatly 4-1 onits multiplication and is readily available from specialists and has a matching master cyl that should do you nicely and as said veichle has very similar size brakes to what you are using it should match quite well, also loads in breakers for second hand items

 

to those of you thinking tr7, the servo is slightly to big in diameter, ive tried it!

 

hugh

[knortech]

Having done a little research a while back i have a few sizes of master cylinders from the brakes international website which may be of help to you

 

 

Rover SD1 76-87 BMC 4327 22.0mm dia

 

Sherpa 200 300 series 83-89 BMC4454 22.2mm dia

 

Sherpa V8 and 200-300 van 78-89 BMC4456 25.4mm dia (used with 46mm dia 4 pot calipers)

 

TR7 std 20.6mm dia

[chillidoggy]

Many thanks for the quick replies chaps!

 

Knortech, that's a particularly interesting post, I hadn't realised that there were such variations in the bore sizes. The Jag 4-piston calipers I have fitted will almost certainly be similar to the XJS ones Wayne is on about fitting to his TR. They're fairly big, heavy beasts, with a huge pad area.

 

I can say though, that even with the MGB master cylinder and it's 19.8mm bore, I never felt as if pedal travel was an issue. Which is strange because I would have thought that a bit more fluid would have to be moved with such large calipers. but perhaps the fact that the Jag set up has only two hydraulic hoses at the front to flex (none at the XJ rear, the dif is solidly mounted) that there's less of such problems.

 

Looks like I'd best get my thinking cap on and take some kind of plunge into the dark world of cylinders and servos!

 

Toodle pip.