Lotus Elan

Tandem brake master cylinder

PostPost by: crypto » Sat Jun 11, 2016 3:41 pm

My car was booked for an MOT yesterday (for the first time, here in Switzerland).
Everything went well except my car has only a single circuit brake system. :(
As a matter of fact, the Swiss law requires all cars from 1.1.1973 to have a two circuit brake system.
My car was built Sept.72 but first registration is Feb.73 and this is what counts !

I browsed thru the shops of the well know suppliers but could not find a suitable tandem master cylinder.
As far I know they where only equipped on the federal versions ? Do they have two servos then or none at all ?

Are there any alternatives ? I found a tandem master cylinder for the Spitfire, but the tube exit is on the left side and I'm not sure about the piston diameter ?

Thanks Peter
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PostPost by: UAB807F » Sat Jun 11, 2016 4:16 pm

Hi Peter,

The Spitfire one is the same bore (0.7") as the standard 2 seat elan and is what a lot of folks use when they wish to fit dual circuit brakes on UK spec cars. Like this....

http://www.martley.plus.com/lotusland2016/elan/16elan08.html

Note - the Spitfire one I bought had metric connections, the OEM Lotus one had Imperial so you need two custom lines making up with metric/imperial ends.

If you want servo assistance then you'll need to fit another servo alongside. Alternatively you can try without servo assistance and see if you can handle the additional pedal pressure with something like Greenstuff or Mintex pads in place of the standard Elan pads. A lot of folks are happy with that option - it's been debated several times on here !

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PostPost by: pharriso » Sat Jun 11, 2016 6:00 pm

crypto wrote:
I browsed thru the shops of the well know suppliers but could not find a suitable tandem master cylinder.
As far I know they where only equipped on the federal versions ? Do they have two servos then or none at all ?


Thanks Peter


No servos, there isn't enough room.
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PostPost by: rgh0 » Sun Jun 12, 2016 12:44 am

I use one from early 70's Datsuns on my Elan. Similar units were used on a range of Datsun and probably other Japanese cars of the era. It has outlets on the bottom and bleeders on the right hand side ( though the casting is obviously done to have bleeders on either side depending on application). They can be fitted with remote reservoirs like I have done or there is a direct fitted reservoir I have seen also.

Length and the bottom outlets may be a problem with the Plus 2 installation location


img_1300.jpg and



When running dual braking systems originally, Elans had two boosters in the Nose and Plus 2's had two boosters on the LH side of the engine bay. With modern high coefficient of friction brake pads you can do away with the boosters if you want

cheers
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PostPost by: prezoom » Sun Jun 12, 2016 4:06 am

The Datsun/Nissan 1200/Sunny has the approximate bore, 11/16 inches. Metric threads, adapters are available, and the correct mounting orientation. They are made by Centric. I purchased one about two months ago, to replace the current master in my Plus2, which had its servos removed. It looks to be the same, as in Rohan's photo.
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PostPost by: Gray » Sun Jun 12, 2016 11:15 am

Classicar Automotive still advertise tandem cylinders in the Club Lotus magazine from ?135.
I also bought adjustable pushrods for the brake and clutch cylinders as well to align the pedals more evenly.
Still not on the road so can't comment on effectiveness but they have a good reputation.
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PostPost by: vstibbard » Sun Jun 12, 2016 11:59 am

I've used the 11/16" nissan master cylinders on a number of Elans, both with Plus two callipers and stay Elan callipers. It gives great feel and confidence building firm pedal. In both instances I've used remote reservoirs.

Cheers

V
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PostPost by: crypto » Sun Jun 12, 2016 3:19 pm

Thanks for all your input. In the meantime I've done some research...

1) In my opinion the Spitfire variant would work, has the correct bore (0.7"), but looks a little odd because of the reservoir (it's like a wedge) but more important it will not fit on LHD car because the reservoir touches the fiberglass body. Also the pipe exit is on the left, but that I can handle.
2) The Datsun version looks good but they seem to be either 3/4" or 1". The reservoirs seem slim enough to fit in. The pressure difference from 0.7" to 0.75" piston size is about 15% (if my math is correct :? )

Question:
- is the flange (the part attached to bulkhead) about correct or does it require machining to make the holes fit ?
- is there a regulator screw to adjust pressure/force between front and rear or is this done by piston size in the brake itself ?

Thanks Peter
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PostPost by: Galwaylotus » Sun Jun 12, 2016 8:22 pm

crypto wrote:Thanks for all your input. In the meantime I've done some research...

1) In my opinion the Spitfire variant would work, has the correct bore (0.7"), but looks a little odd because of the reservoir (it's like a wedge) but more important it will not fit on LHD car because the reservoir touches the fiberglass body. Also the pipe exit is on the left, but that I can handle.
2) The Datsun version looks good but they seem to be either 3/4" or 1". The reservoirs seem slim enough to fit in. The pressure difference from 0.7" to 0.75" piston size is about 15% (if my math is correct :? )

Question:
- is the flange (the part attached to bulkhead) about correct or does it require machining to make the holes fit ?
- is there a regulator screw to adjust pressure/force between front and rear or is this done by piston size in the brake itself ?

Thanks Peter

The original setup had only one bore so a tandem master cylinder with the same bore will have the same balance. I used an AP Racing master cylinder with a remote reservoir. I believe it's a Caterham spare. Works very well for me with Greenstuff front pads and no servo.
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PostPost by: rgh0 » Sun Jun 12, 2016 11:24 pm

The Datsun cylinder flange matched the somewhat oversize cylinder hole and bolt holes in the body work of my Elan so it bolted straight in. i am not sure if the spacing is absolutely identical to the Girling cylinders so it may require a little fettling if the holes are more precise like on the metal Plus 2 pedal box mounting. i used the original push rod which fitted straight in.

You need to check the pedal travel with one of the circuits in operative to ensure you have enough travel for the other circuit to still work. I only just had enough travel for this before the pedal hits the floor on the Elan

I believe the Datsun ones came in a range of bores from 11/16 to 1 inch in. I choose 3/4 and that works well with my Elan and its high coefficient pads on the track when the brakes are hot. Pedal effort is a very personal preference so you will have to determine that yourself. If you have trouble sourcing the 11/16th size then I would not be to worried about trying the 3/4. The bores are the same for the front and rear pistons so the pressure is the same in both circuits. The Plus 2's brakes are well balanced with modern sticky tyres and high coefficient front pads ( better than an Elans).

cheers
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PostPost by: fatboyoz » Tue Jun 14, 2016 4:40 am

Peter,
I used this master cylinder on my RHD S4. Bought secondhand and sleeved:
http://www.ebay.co.uk/itm/Westfield-Mas ... 7675.l2557
Here is the latest item from the Westfield site:
http://parts-shop.westfield-sportscars. ... duct_id=84
Caterham does something similar.
Unfortunately, these only seem to be made with the hydraulic pipes exiting from the L/H side.
Cheers,
Colin.




crypto wrote:My car was booked for an MOT yesterday (for the first time, here in Switzerland).
Everything went well except my car has only a single circuit brake system. :(
As a matter of fact, the Swiss law requires all cars from 1.1.1973 to have a two circuit brake system.
My car was built Sept.72 but first registration is Feb.73 and this is what counts !

I browsed thru the shops of the well know suppliers but could not find a suitable tandem master cylinder.
As far I know they where only equipped on the federal versions ? Do they have two servos then or none at all ?

Are there any alternatives ? I found a tandem master cylinder for the Spitfire, but the tube exit is on the left side and I'm not sure about the piston diameter ?

Thanks Peter
'68 S4 DHC
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PostPost by: mariodschy » Tue Jun 14, 2016 7:23 am

pharriso wrote:
crypto wrote:
I browsed thru the shops of the well know suppliers but could not find a suitable tandem master cylinder.
As far I know they where only equipped on the federal versions ? Do they have two servos then or none at all ?


Thanks Peter


No servos, there isn't enough room.


Can confirm, originally there were tandem master cylinder but no servos on Fed Sprints
- 1972 Lotus Elan Sprint LHD/DHC
- 1962 Austin Healey Sprite MK II - Sold 09.05.2016

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PostPost by: Mazzini » Sun Jun 21, 2020 8:23 am

I made and fitted new brake pipes, plumbed in the new master cylinder and went for a drive. I have +2 discs and calipers on my Sprint. The brakes felt a bit wooden, but then they got better. After twenty miles the brakes started binding. I stopped then car and jacked up each corner, I could rotate the wheels but there was some resistance. I let the car cool down. I managed to tap the pads back and drove home with brakes that functioned perfectly (good pedal).

Later I took the car on a short drive. The brakes functioned well, till the last mile or two, then they started to bind again.

The front and rear calipers have new SS pistons and worked fine before the M/C swap.

I guess the M/C is to blame. I had it apart before I fitted it, but put it back together the same way. The only thing I did was remove the needle shaped bolt that stops the piston from going back past that point.

Any ideas where I am going wrong?
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PostPost by: rgh0 » Sun Jun 21, 2020 8:36 am

mariodschy wrote:
pharriso wrote:
crypto wrote:
I browsed thru the shops of the well know suppliers but could not find a suitable tandem master cylinder.
As far I know they where only equipped on the federal versions ? Do they have two servos then or none at all ?


Thanks Peter


No servos, there isn't enough room.


Can confirm, originally there were tandem master cylinder but no servos on Fed Sprints



I am sure I have seen photos of US sprints with two servos located in the nose. Maybe I am imagining it :?

cheers
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PostPost by: nmauduit » Sun Jun 21, 2020 8:56 am

Mazzini wrote:I guess the M/C is to blame. I had it apart before I fitted it, but put it back together the same way. The only thing I did was remove the needle shaped bolt that stops the piston from going back past that point.

Any ideas where I am going wrong?


I understand you don't have a brake booster (which can add behaviors of its own) : what MC do you have ?

I'm not sure I get this : are you saying that you just removed the bolt it then put it back (one usually needs to push on the rod to reinstall the stop nut back because of the internal spring), or did you remove the piston then reinstall everything? There is a small hole that interconnects the fluid tank with the MC rear area (equalization port), so that fluid gets replenished at the back of the piston when it moves (normally open at rest position which also enables fluid to get back into the braking circuit, then when one presses the pedal the seals passes over the pressure port and effectively seals the braking circuit from the spare fluid circuit). If the piston resting position is not adequate it is possible to get pressure build up in the circuit (it is also possible to get similar self locking behavior if some debris are back clogging the small hole, e.g. brake seal edge that would have been cut off when installing the piston dry against a sharp internal edge acting as a one way valve).
Last edited by nmauduit on Sun Jun 21, 2020 9:22 am, edited 1 time in total.
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