'71 Vixen - brake servo required.
Discussion
Is a servo'd braking system needed on a Vixen?
I've started a restoration and am considering replacing the original m/c and servo with a single or twin m/c setup.
The car has/will have new front discs/calipers and rear shoes/drums/etc.
Has anyone done this, or have any advice on the way forward?
TIA - Simon
I've started a restoration and am considering replacing the original m/c and servo with a single or twin m/c setup.
The car has/will have new front discs/calipers and rear shoes/drums/etc.
Has anyone done this, or have any advice on the way forward?
TIA - Simon
Vixen have big front discs relative to the mass of the car and with servo assistance, I found mine to be over braked at the front, especially in the wet. Sliding to a halt at traffic lights was not uncommon for me so I simply disconnected the vacuum to the servo and blanked it off. Ran it like that for years with no problem and found it easier to modulate braking without the servo assistance.
Info - if it's a any use...
All a servo does is to lessen the effort required..... as far as I know, the only changes made by manufacturers was to make a non-servo car have a slightly smaller diameter master cylinder.
This increases the line/hydraulic pressure for the same foot pressure, in exchange for a bit more pedal travel.
Original setup is all TR6, I don't know if any TR6 were servo-less, but front brake calipers were also used on Vitesse and GT6 which did not have a servo (the early ones at least), and must be about the same weight as a Vixen ?
All a servo does is to lessen the effort required..... as far as I know, the only changes made by manufacturers was to make a non-servo car have a slightly smaller diameter master cylinder.
This increases the line/hydraulic pressure for the same foot pressure, in exchange for a bit more pedal travel.
Original setup is all TR6, I don't know if any TR6 were servo-less, but front brake calipers were also used on Vitesse and GT6 which did not have a servo (the early ones at least), and must be about the same weight as a Vixen ?
Are you racing the car? If not why upgrade to a dual master cylinder?
a sensible upgrade would be to use a std servo with Cortina master cylinder. this is twin circuit and also comes with a fluid warning indicator.
this allows you to dispense with the PDWA which is a hateful piece of kit on vixen braking circuits.
Other than upgrading pad material there is no reason to upgrade, especially on a road car.
This car has 180hp and is totally standard apart from previously mentioned mods.
N.
Dollyman1850 said:
Are you racing the car? If not why upgrade to a dual master cylinder?
a sensible upgrade would be to use a std servo with Cortina master cylinder. this is twin circuit and also comes with a fluid warning indicator.
this allows you to dispense with the PDWA which is a hateful piece of kit on vixen braking circuits.
Other than upgrading pad material there is no reason to upgrade, especially on a road car.
This car has 180hp and is totally standard apart from previously mentioned mods.
N.
That looks great; what are you using, to secure the cushioned clamps to the body?
Best regards,
Bernard.
I replaced a strange hybrid jap m/c with a TR6 unit after it dumped brake fluid in the footwell and took the shine off my stilettos. Fitted perfectly in minutes and works well despite the plunger to piston dimension being nowhere near correct.
Strange though - when bleeding the brakes why doesn't the brake warning light come on as the pressure differential must surely be enough the trip the sensor?
Strange though - when bleeding the brakes why doesn't the brake warning light come on as the pressure differential must surely be enough the trip the sensor?
Missingbadly said:
I replaced a strange hybrid jap m/c with a TR6 unit after it dumped brake fluid in the footwell and took the shine off my stilettos. Fitted perfectly in minutes and works well despite the plunger to piston dimension being nowhere near correct.
Strange though - when bleeding the brakes why doesn't the brake warning light come on as the pressure differential must surely be enough the trip the sensor?
What warning light other than a handbrake light is there on a Vixen, cos I ain't got one?Strange though - when bleeding the brakes why doesn't the brake warning light come on as the pressure differential must surely be enough the trip the sensor?
I'm a bit confused by the photos....er.. it's probably me.
My S3 Vixen dual has dual circuit, which I believe was original, with the matching dual circuit TR6 Mcyl and a PDWA.
That pic looks just like the S3 pedal box/bulkhead moulding....
And brake light on those dual systems comes on when there is a fairly big pressure difference between the circuits, so if M/C is dodgy then BOTH circuits could be leaky, and light won't always come on.
My S3 Vixen dual has dual circuit, which I believe was original, with the matching dual circuit TR6 Mcyl and a PDWA.
That pic looks just like the S3 pedal box/bulkhead moulding....
And brake light on those dual systems comes on when there is a fairly big pressure difference between the circuits, so if M/C is dodgy then BOTH circuits could be leaky, and light won't always come on.
Edited by RCK974X on Friday 30th January 19:20
RCK974X said:
I'm a bit confused by the photos....er.. it's probably me.
My S3 Vixen dual has dual circuit, which I believe was original, with the matching dual circuit TR6 Mcyl and a PDWA.
That pic looks just like the S3 pedal box/bulkhead moulding....
And brake light on those dual systems comes on when there is a fairly big pressure difference between the circuits, so if M/C is dodgy then BOTH circuits could be leaky, and light won't always come on.
The S2 late and S3 are the same (though clutch operation may differ) The TR6 set up is a twin circuit but has a brake failure warning (PDWA) actuator in the circuit… The cortina master cylinder is a Tandem twin circuit, IE 2 ports for front brakes rather than needing an external T piece or the PDWA set up which consists of a shuttle device which works to illuminate a light when the brakes fail due to front or rear loss of pressure.. On the cortina set up you have a simple float switch which senses loss of fluid, hence brakes..Generally brakes fail because the fluid disappears somewhere where it isn't meant to go. It is merely a simple way of doing away with a massively complicated PDWA bit of Cack which has many additional opportunities to fail..Also saves on double the amount of brake pipe connections mess on the front bulkhead etc etc....Doubless there are many other master cylinders which can be used…The cortina fits the original servo…A number of Landrover ones do also.. The reservoirs are the bits which are getting harder to source these days….My S3 Vixen dual has dual circuit, which I believe was original, with the matching dual circuit TR6 Mcyl and a PDWA.
That pic looks just like the S3 pedal box/bulkhead moulding....
And brake light on those dual systems comes on when there is a fairly big pressure difference between the circuits, so if M/C is dodgy then BOTH circuits could be leaky, and light won't always come on.
Edited by RCK974X on Friday 30th January 19:20
Interesting article…
Fill ya boots..
http://clivescortina.co.uk/home/brake-saga-part-3/
N.
Edited by Dollyman1850 on Friday 30th January 20:09
Yeah, sorry wasn't clear there - I have a Wedge too, so I know about the Cortina 4 MCyl, which I recognised, but I didn't get why the original TR6 mcyl isn't the obvious choice....the whole assembly and PDWA can still be purchased. My S3 ('72) has a cable clutch, but is otherwise the same pedal box moulding.
I see why though, if you don't want to bugger about with a PDWA switch !!
NB. whilst that is a Cortina MCyl, I'm pretty sure it's not the Cortina vacuum part, which is a lot larger then the one in the photo, and the plastic reservoir looks different too... did Ford change it, or was MC used in other models ?
Yeah, I guess there will be a range of things that will fit instead.
I see why though, if you don't want to bugger about with a PDWA switch !!
NB. whilst that is a Cortina MCyl, I'm pretty sure it's not the Cortina vacuum part, which is a lot larger then the one in the photo, and the plastic reservoir looks different too... did Ford change it, or was MC used in other models ?
Yeah, I guess there will be a range of things that will fit instead.
RCK974X said:
Yeah, sorry wasn't clear there - I have a Wedge too, so I know about the Cortina 4 MCyl, which I recognised, but I didn't get why the original TR6 mcyl isn't the obvious choice....the whole assembly and PDWA can still be purchased. My S3 ('72) has a cable clutch, but is otherwise the same pedal box moulding.
I see why though, if you don't want to bugger about with a PDWA switch !!
NB. whilst that is a Cortina MCyl, I'm pretty sure it's not the Cortina vacuum part, which is a lot larger then the one in the photo, and the plastic reservoir looks different too... did Ford change it, or was MC used in other models ?
Yeah, I guess there will be a range of things that will fit instead.
Its a TR6 servo as Std. The benefits of using the Cortina master cylinder is also that it is available in different sizes so you can tune the amount of braking force and pedal feel. The cortina set up is just a lot better all round or at least was when it was commonly available when this mod was first carried out some 30 years ago. Now cortina master cylinders are getting rare so doubtless its less of a benefit…Anything to get rid of the PDWA is a good idea however. This method does it simply and allows for a bigger travel by using various m/c sizes for example if you want to use much bigger discs and callipers which have also been done.I see why though, if you don't want to bugger about with a PDWA switch !!
NB. whilst that is a Cortina MCyl, I'm pretty sure it's not the Cortina vacuum part, which is a lot larger then the one in the photo, and the plastic reservoir looks different too... did Ford change it, or was MC used in other models ?
Yeah, I guess there will be a range of things that will fit instead.
N.
Gassing Station | TVR Classics | Top of Page | What's New | My Stuff