Brake master cylinder

[TomR]

The tandem cylinders are available in the US in 0.7" which works pretty well without the booster on 14lf calipers. If you're talking +2 it would probabaly be ok as well but I haven't tried and I'd double-check that the pedal travel isn't too long.

Personally I'm going to fit double girling 5/8 cylinders and balance bar ala 26r one way or another.

I have way too many things to do...

Tom

[freddy22112211]

Recently also had no brakes when system hot - the dual master cylinder system didn't help at all (lotus standard dual master cylinder)! Bled the brakes several times - but no joy. Turned out to be very thin watery brake fluid in the master cylinder that bleeding wasn't getting rid of. - So - always take the cylinder apart and don't rely on bleeding.
Gordon 72 Sprint

[steveww]

I use a pressure bleeder and always run plenty of fluid through. This has always worked for me. BTW I use Castrol SRF fluid.

At the moment there is a single 0.7" master cylinder fitted feeding +2 (P16) front callipers and standard rear callipers. Pedal travel and effort required are fine with no servo but this is on a +0 the heavier +2 may need more mechanical advantage.

[Tonyw]

I have repaired literally hundreds of thses master cylinders albiet in my younger days, I do not recall a total failure, usually the first sign of the master cylinder starting to fail is a "pedal creep" on light braking, this is the time to immediatly stop driving the car and overhaul the master cylinder, the creep is caused by fluid by passing the seal, harder braking forces the seal to expand further and tighter against the cylinder wall, you can also get creep if the bore is scored for obvious reasons. At the risk of stating the obvious the whole system needs to spotlessly clean and kept clean, even topping up the master cylinder you need to ensure that no dirt gets into the resorvoir, changing the fluid every year or two will extend the life of the system.

I will be fitting a standard master cylinder taking all the proper precautions.

Tony

[alan71]

Just found a photo I took of the old valve seal, it?s not the side that seals the hole to the reservoir but you can see the state of the rubber. It wasn?t caused by wear or old age, it was only a couple of years old. I can?t say if it was OK when I fitted it as I just changed the whole master cylinder.

Alan

[Frank Howard]

Alan,

It is my understanding that the seals are made of pure rubber rather than neoprene as used in most brake systems. Most brake fluid attacks pure rubber. Perhaps that includes silicone. I use Castrol LMA and experience practically zero failures. Hope this helps someone before it's too late.

[alaric]

Article 20 in Jerry Thurston's +2 restoration in classics monthly mentions a Tilton 74 series master cylinder supplied by GP Racewear. He's replaced both the clutch and brake master cylinder, and fitted the new ones into the original pedal box.

Both my original brake and clutch master cylinders are working nicely now. The clutch one must have been siezed and I'll probably replace the internals at some point.

Presumably if I modded the pedal box by cutting an access hole in the top I could easily remove the master cylinders without taking the pedal box out - with a rubber grommet or two to seal it back up. Has anyone else done this?

Sean.

[tdafforn]

I have...
I cut a square whole in the top of the pedalbox and then covered it with a new peice of steel cut to size and held in place with self tappers. I used some self adhesive draft excluder on the inderside to seal..
Words a treat.,
tim

[bcmc33]

There have been numerous threads in the past regarding unboosted brakes on the baby Elan. From memory most of the comments for not using the servo was to get a ?better feel? when braking, and maybe I can understand such a subjective view. But as already said in this thread, by simply removing the servo the pedal effort must be increased to obtain the same braking performance.
Prompted by Sean, I looked at the ?Tilton 74? master cylinders to find that they do a range of eight diameter versions between 0.62? and 1.125? all within the same footprint ? so it is possible to obtain different performing units.

To do any calculations to consider removing the servo ? what is the size of master cylinders used on Elans?

Some comments from members who have removed the servo and what they did to maintain braking performance would be useful.

[mikealdren]

Don't forget that Gerry's car will be a Zetec car and will have very different (Sierra) brakes and no servo.

Mike

[Expat+2]

The Elan Factory does a 0.7" tandem cylinder.

http://www.elanfactory.com.au/pdf/product_datasheets/Tandem%20brake%20master%20cylinder.pdf

I have it in my +2 without boosters and with Greenstuff front pads, it works well, it needs the high friction pads though. It's a good product although mine needed some grinding to the rear piston to make it work with my pushrod. They recommend it for use with twin boosters but this just seems OTT.

BTW is there an alternative to Greenstuff for high friction pads?

[gerrym]

Martin, do the ElanFactory details master cylinder bore size.
If you refer to my spreadsheet (Labelled Brake Balance under Plus 2), you can model effect of high friction front pads and no servo boost. (and all other permutations etc)
Regards
GerryM

[alaric]

That elanfactory unit looks the business - thanks for the link.

If someone that's had the opportunity to try the +2 with and without the servo could give an estimate of the gain from the servo, that would be great. The pressure is inversely proportional to the square of the diameter of the bore so a halving in the bore will give us 4 times the pressure from the same pedal force - but more pedal travel. My refurbished servo is in the loft - maybe I could work out the gain from the ratio of the diaphrams... Getting rid of the servo would remove a leak path into the manifold, and remove a significant amount of real estate from under the bonnet - an interesting idea.

All the best.

Sean.

[alaric]

Hoorah! I have a clutch - when I push the pedal down, the car rolls along, when I let it up, it stops. So tomorrow I try it with the engine running - should I get the brakes working first - guess I should really, just to be safe.

Oh by the way, I now realise it's a good idea to block up the drain holes in the pedal box before messing around with brake fluid - when I pressurised the system to bleed it the cap leaked!

Sean.

[steveww]

I run my S4 with out servo and +2 front callipers with Green Stuff pads. I can still lck the fronts on a dry road even with sticky tyres. More pedal pressure than modern over servo systems is required.

Remember that the +2 callipers have a greater piston size so there is more mechanical advantage or "boost". You could fit a smaller master cylinder which would increase the mechanical advantage more at the cost of longer pedal travel. The non servo system IMHO gives much better pedal feel. IIRC only the SE Elan models had a servo?