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Larger Bore Brake Master Cylinder?

Posted: Tue Feb 04, 2020 9:09 am
by xvivalve
I know the subject of the merits and demerits of having a larger bore brake master cylinder has been discussed at length, but opportunity has arisen if someone would like to test theory in practice!

In all the years I've been liaising with the reconditioners, they have been telling me they have a box of items they did for Ted on behalf of the Club somewhere, that came to light when they moved premises, but has since been misplaced again; I've always said that when found, we'd happily take ownership and pay them for the work done.

Well, last time I went in, they presented me with a single line brake master cylinder that they proudly stated was one they'd done for Ted; an experiment he'd asked them to do, boring and sleeving (in stainless) to a bore size of 13/16", an incremental increase over the standard 3/4" with new oversized piston to suit. They had replaced all the seals in recognition of how long it had been since the original work had been done, and given my earlier undertaking with them, I felt obliged to take it.

So, if anyone is feeling inquisitive, (maybe this will facilitate a smaller servo to be used on a Sprint?) we have a (currently) one off opportunity to experiment in practice....a write up of your experience and conclusion would make excellent copy for the magazine! So where are all you MoT testers with access to brake efficiency testing equipment?

Outwardly identical to the standard single line master cylinder, even the originality purists could consider this... ;-)

Available at cost, £70 inc postage to UK addresses (slightly more for overseas), it also represents a saving on the standard item.

First come, first served; a one off opportunity!

Re: Larger Bore Brake Master Cylinder?

Posted: Fri Feb 07, 2020 7:22 pm
by soe8m
I use Jag xj brake masters for over 15 years and these go fine. Slightly bigger bore than std so I guess the one you have is a Jag one. Physically exact the same.

Jeroen

Re: Larger Bore Brake Master Cylinder?

Posted: Fri Feb 07, 2020 10:39 pm
by GlenM
soe8m wrote: Fri Feb 07, 2020 7:22 pm I use Jag xj brake masters for over 15 years and these go fine. Slightly bigger bore than std so I guess the one you have is a Jag one. Physically exact the same.

Jeroen
Jeroen,

Are these a tandem cylinder? Have you got a link, or a part number?

Glen.

Re: Larger Bore Brake Master Cylinder?

Posted: Sat Feb 08, 2020 5:59 am
by gmsclassics
I used a Nissan BM-44 tandem master cyl (Nissan Skyline/ Sylvia) on my race Sprint for many years without any issues. 15/16" diameter. Did require mounting holes to be filed out a very small amount to match the std Sprint booster. Also new brake pipe ends as these are metric. Cheap from a wreckers.

Re: Larger Bore Brake Master Cylinder?

Posted: Sat Feb 08, 2020 10:19 pm
by GlenM
Thanks. Will take a look at the BM44 cylinder.

In a word...

Posted: Sun Feb 09, 2020 2:49 pm
by sprint95m
GlenM wrote: Fri Feb 07, 2020 10:39 pm
soe8m wrote: Fri Feb 07, 2020 7:22 pm I use Jag xj brake masters for over 15 years and these go fine. Slightly bigger bore than std so I guess the one you have is a Jag one. Physically exact the same.

Jeroen
Jeroen,

Are these a tandem cylinder? Have you got a link, or a part number?

Glen.
Yes.
They are XJ6 series 1 and have a 22.2mm bore (7/8”)

Another 22.2mm bore option is from a Saab 99/900.
The pipes need redoing because metric unions are required.
These are dual circuit, fit a Dolomite servo
and their fluid reservoir also serves the clutch hydraulics.


Ian

Re: In a word...

Posted: Sun Feb 09, 2020 10:19 pm
by GlenM
sprint95m wrote: Sun Feb 09, 2020 2:49 pm
GlenM wrote: Fri Feb 07, 2020 10:39 pm
soe8m wrote: Fri Feb 07, 2020 7:22 pm I use Jag xj brake masters for over 15 years and these go fine. Slightly bigger bore than std so I guess the one you have is a Jag one. Physically exact the same.

Jeroen
Jeroen,

Are these a tandem cylinder? Have you got a link, or a part number?

Glen.
Yes.
They are XJ6 series 1 and have a 22.2mm bore (7/8”)

Another 22.2mm bore option is from a Saab 99/900.
The pipes need redoing because metric unions are required.
These are dual circuit, fit a Dolomite servo
and their fluid reservoir also serves the clutch hydraulics.


Ian
Thanks Ian.

I have had a couple of Classic 900s and I remember the spigot for the clutch fluid outlet very well. I fitted a new master cylinder to one of them and a couple of years later had some issues with the clutch hydraulics. I hadn't realised that the end of the spigot was moulded shut for automatic cars and needed to be cut off for a manual. I might have to fit a Sprint clutch master cylinder when I change the engine, so the spigot could be useful.

No problem with the fittings being metric, I have a flaring tool and pipe bender.

With both the Saab and Jaguar master cylinders, you can get them new for a reasonable price but they don't come with the reservoir, so might have to get a used one.

Glen.