Brake Master Question

[Bryan Boyle]

As you all know...been working on 3291R for a couple years...and I think it may be time to address the existing master cylinder issue...it slowly weeps fluid out (I think, through the rear seal...but...and, while I can bleed it to a solid pedal that lasts for a few months, obviously it's not a case of 'just keep doing it and it will get better.")

So...I've collected a bunch of candidate MCs:

1. OEM Toyota F10 pickup
2. TRW Triumph Spit slope top .70
3. Original TCS cylinder (slope top)
4. From my parts stash of breaking up 4 S2s...a couple of S2 masters in serious need of rebuild, with a spare new, in the box, S2 reservoir.

Now, having removed the boosters,  I've a non-boosted brake system.  I'm thinking that (assuming I will re-plumb and remove the excess bundy going to the back then returning to the front...) the most satisfactory results may be found by sending the S2 MCs out to Apple and resleeving/rebuilding to S2 spec (stepped bore, etc).  However, I'm wondering if there is enough clearance to use the large reservoir (as on the S2), with its increased capacity, in place of the slope top original TC style without having to do fiberglass surgery.

The advantages to using the Lotus-spec MCs is that

1. There would be no need to do bundy splicing to account for the feed port location on the master...and if I can fit the larger reservoir without carving fiberglass...well, that would be a plus too (not that I'm against it in the goal of increasing the capacity....),

2. Removing the out-and-back tubing for the front calipers would simplify and remove multiple splices to account for the booster and PDWV removal, and

3. The bores are close enough by using the S2, (accounting for the different size of the rear brake cylinders) for the car's dynamics (as far as I can tell).

Open to thoughts.   

[berni29]

Hi Bryan

I cannot help you with your specific question (and are also interested in the answer), but may I ask why you removed the dual boosters? Was it just the additional complexity and weight that made the standard system unattractive? Its something that I will also be dealing with at some point. I would like to keep my car original, but when it comes to things like this I prefer the most elegant solution and just keep the original parts on a shelf somewhere.

Do people loose points for removing the boosters?

All the best

Berni

[Grumblebuns]

Bryan, if I understand what you are asking you are determining what master cylinder to substitute after removing your original MC and removing the boosters with the requirement of having decent reservoir volume. The S2 MC would be the first choice since this would be a simple bolt on effort provided the reservoir is in decent shape. The only problem I see in using the original fittings and flare end is possible leakage when fitted to the replacement S2 MC. Cranking down on the fitting may or may not stop the leak.

The Spitfire MC is a good option since it is a semi bolt on. The ports being on the opposite side requires jumpers and the ports are probably metric. The downside is the severely sloped reservoir. I have not looked at the requirements but installing a remote reservoir may allow you to meet your volume requirements.

The only alternate MC that I've had any experience with is the Datsun/Nissan F10 that the PO installed on my long sold JPS. The braking on that car was outstanding with great feel and stopping power. What ever brake pads were installed on that car made all the difference.

I'm in the middle of installing the Courier MC on my TCS. The project has been stalled for a while due to other more urgent projects. With the ports being metric I had to cut odd the original fittings and splice in new jumpers with metric fittings. One problem I ran into was the super tight clearance between the MC ports and the bodywork of the bottom of the nose section. There is about one inch of space to make the tight 90 degree bend without kinking the line.

 

[EuropaTC]

Hi Bryan,

I had the Spitfire 0.7 dual circuit m/cyl on my car for a while at one point and there are a several guides on how to do it on the forum.

When I did mine I removed the wedge shape reservoir and replaced it with a remote one from a Land Rover. Apart from having a greater capacity and being easier to see, it also came with a low fluid warning switch.  Anyway, the 0.7" cylinder is ok with non-servoed standard brakes so you know that one will work.  I no longer have that on my car but I do have one on the Elan, again without servo assistance but with the larger piston P16 calipers and it's fine.

If you are currently using the OEM Lotus m/cylinder, am I correct in thinking the later Specials had a larger bore to handle a larger rear brake cylinder ? If so, you might not like the additional travel with a 0.7" bore or at least it will take some getting used to. But the big plus is that it's a well trodden path, bolts straight into the chassis and so there's no real surprises in store.

Brian

[BDA]

...am I correct in thinking the later Specials had a larger bore to handle a larger rear brake cylinder ?

According to the parts manual, all the TCs and TCSs used the same master cylinders.

[Bryan Boyle]

Hi Bryan,

I had the Spitfire 0.7 dual circuit m/cyl on my car for a while at one point and there are a several guides on how to do it on the forum.

I know...just refreshing the discussion since it's getting towards spring up here in the northern climes, and pretty sure, besides myself, folks are looking at recommissioning their rides for the season (though, to be honest, I've had mine out more than once considering the lack of winter weather here in MA last winter...)

When I did mine I removed the wedge shape reservoir and replaced it with a remote one from a Land Rover. Apart from having a greater capacity and being easier to see, it also came with a low fluid warning switch.  Anyway, the 0.7" cylinder is ok with non-servoed standard brakes so you know that one will work.  I no longer have that on my car but I do have one on the Elan, again without servo assistance but with the larger piston P16 calipers and it's fine.

I like the idea of remote reservoirs; only question is the fittings on the MC end to accept the hose from the reservoir in place of the attached piece.  Don't necessarily want to get into fabrication of hose fittings and such...any guidance there, sir?  That it has a low level indicator is a plus...take the place of the removed PDWV.  Always thinking, right?

If you are currently using the OEM Lotus m/cylinder, am I correct in thinking the later Specials had a larger bore to handle a larger rear brake cylinder ? If so, you might not like the additional travel with a 0.7" bore or at least it will take some getting used to. But the big plus is that it's a well trodden path, bolts straight into the chassis and so there's no real surprises in store.
Brian

The question of travel is one to consider.  In looking again at the S2 MC, it's well rusted...and thinking it may be past freeing up the piston and returning it to service.  Additionally, the top attach fitting is a captured nut...so wondering if that will be a problem...but probably not, because IIRC, both of the studs are the same size/pitch. 

[EuropaTC]

I like the idea of remote reservoirs; only question is the fittings on the MC end to accept the hose from the reservoir in place of the attached piece.  Don't necessarily want to get into fabrication of hose fittings and such...any guidance there, sir?  That it has a low level indicator is a plus...take the place of the removed PDWV.  Always thinking, right?

It's not that difficult to fit a remote with the Spitfire m/cyl. The wedge reservoir pushes into 2 rubber grommets in the body so it just pulls off. You can buy plastic or metal fittings in 45,90 & 180 deg angles and all you need is to match the OD on what you buy to the OD of the reservoir. I bought mine from Ebay when I did my conversions and I picked 90deg and although it's no longer on the Europa, it is on the Elan. 

The remote reservoir is debatable on the Europa but a real plus on the Elan because it's hidden away beneath the carbs and a PITA to monitor/fill when bleeding. The second image gives you an idea of the fittings & why it's a good idea.

What is handy is the remote level switch. I wired the Europa up to a warning light I fitted in the place of a blanking plug in the centre of the dash. It's a simple circuit and doesn't do a self test when you switch on as modern cars do, if you want to know if it's working you just press down on the switch  .   For the Elan, with no spare lamps, I wired it into the handbrake warning light. If the handbrake is on, the lamp is on. Release the brake and it goes off but if the level is low the lamp still gets a ground so stays on. A more elegant solution with no visible mods to the car other than wiring.

The question of travel is one to consider.  In looking again at the S2 MC, it's well rusted...and thinking it may be past freeing up the piston and returning it to service.  Additionally, the top attach fitting is a captured nut...so wondering if that will be a problem...but probably not, because IIRC, both of the studs are the same size/pitch.

I'm guessing if you're going to recommission an old m/cyl you'd end up getting it sleeved, which may or may not end up losing the stepped bore. Personally I don't think the stepped bore is a big deal so it wouldn't worry me, but then again there's loads of modern options if you decide a single bore diameter is ok.

Being a geek I actually calculated the pedal travel and can tell you that mine, with rear discs, came in at 3.8cm and I measured between 3.5 & 4cm, the differences all down to me and grovelling down that footwell. Now part of that calc is down to the leverage ratios on the pedal, something that you can modify on the Europa but is limited by the angle of the actuating rod and being so cramped down there. The Elan, even with bigger dia. front pistons, had less travel - down to the leverage ratios - and it feels "better".

But when I fitted larger bore rear calipers to the Europa,  it made the difference between the cars more noticable. The calcs said "don't worry", but we humans can be funny creatures and I didn't like it.  Anyway, the 0.75 m/cyl I have now gives only a 6mm reduction in travel but for some reason it feels more secure. I wouldn't have thought it based on the numbers but apparently my foot and self-preservation instincts can tell the difference !

Brian

[Clifton]

I'm not running stock anything to compare but I know a larger MC bore will give less travel and less desirable feel. I run a 5/8 front and re drilled the brake arm to get a better pedal ratio. A little more travel gives better feel and modulation.

[Bainford]

The remote reservoir is debatable on the Europa but a real plus on the Elan because it's hidden away beneath the carbs and a PITA to monitor/fill when bleeding.

I have toyed with the idea of fitting a remote reservoir on my Europa simply to raise the reservoir and provide improved head pressure for maintenance, bleeding, etc. As it is now, the height of the OEM reservoir can't be much higher then the bleeders on the front calipers. I will eventually tackle a complete brake service project (all new lines, other mods, etc) and considering the remote reservoir for that reason alone.

[EuropaTC]

I have toyed with the idea of fitting a remote reservoir on my Europa simply to raise the reservoir and provide improved head pressure for maintenance, bleeding, etc. As it is now, the height of the OEM reservoir can't be much higher then the bleeders on the front calipers. I will eventually tackle a complete brake service project (all new lines, other mods, etc) and considering the remote reservoir for that reason alone.

It is a strange one, the remote reservoir was standard on the UK single circuit brakes and honestly there's no great effort to fit a remote to a tandem m/cyl. I can only think that when Lotus moved to dual  circuits for the Federal cars they decided it was cheaper to leave the tandem cylinder as it came and save on the production line costs for a remote + pipework.

Having said that, the single circuit m/cyl is much easier to fit a remote to, the reservoir connection is threaded so it's easy to fit a feed pipe. 

When I was researching braking systems I found several references to the advantage of having a head of fluid above the tops of the calipers/drums. So yep, if you're refreshing the whole system I'd say it's a good idea, plus of course it's much easier to fill and monitor.

Brian

[surfguitar58]

Very timely that this discussion should come up (again) now. I wave waffled all over the map wrt the deleted booster/MC debate. I had settled on a pedal geometry change solution that I was going to get to, one of these days (detailed in another thread somewhere) but, predictably, never got around to it. I actually am pretty used to having to “brake with authority” with the stock .875” MC. (The poor guy who is required by law to drive the car into the inspection bay has a “no brakes” panic attack every year, however.)

However, for the first time in eight years I am treating the car to a “professional” spring tune-up and re-commissioning and the mechanic found corrosion in the MC bore that simple honing won’t clean-up.

So:

-Simply sleeve-the-original MC ($245 quote from Apple Hydraulics), with or wo the pedal geometry change?

-Replace the original MC with a smaller bore MC from another vehicle, with all the inherent pipe-routing, mismatched fittings and funky reservoir mounting problems?

-Or, my dream solution: Sleeve the original MC down to a smaller dia, turn the pistons and seal-ring grooves down to match, source replacement seals, and keep the original MC look and plumbing with a lighter touch on the brakes?

Stepping the original .875” MC down to .750” would give a nice 27% increase in brake pressure (and corresponding increase in panel stroke), while reducing to .705” (stock S2 bore dia, if I’m not mistaken) would be 35%. The .705” solution might also allow swapping S2 MC innards into the reduced-bore TCS MC body. I’m digging into the possibilities with the shop next week and will let everyone know where the chips land.

Tom

[Bryan Boyle]

Very timely that this discussion should come up (again) now. I wave waffled all over the map wrt the deleted booster/MC debate. I had settled on a pedal geometry change solution that I was going to get to, one of these days (detailed in another thread somewhere) but, predictably, never got around to it. I actually am pretty used to having to “brake with authority” with the stock .875” MC. (The poor guy who is required by law to drive the car into the inspection bay has a “no brakes” panic attack every year, however.)

However, for the first time in eight years I am treating the car to a “professional” spring tune-up and re-commissioning and the mechanic found corrosion in the MC bore that simple honing won’t clean-up.

So:

-Simply sleeve-the-original MC ($245 quote from Apple Hydraulics), with or wo the pedal geometry change?

-Replace the original MC with a smaller bore MC from another vehicle, with all the inherent pipe-routing, mismatched fittings and funky reservoir mounting problems?

-Or, my dream solution: Sleeve the original MC down to a smaller dia, turn the pistons and seal-ring grooves down to match, source replacement seals, and keep the original MC look and plumbing with a lighter touch on the brakes?

Stepping the original .875” MC down to .750” would give a nice 27% increase in brake pressure (and corresponding increase in panel stroke), while reducing to .705” (stock S2 bore dia, if I’m not mistaken) would be 35%. The .705” solution might also allow swapping S2 MC innards into the reduced-bore TCS MC body. I’m digging into the possibilities with the shop next week and will let everyone know where the chips land.

Tom

I'd like to know what you find out; I have a standard TC MC here, as well as an S2 (albeit rusty, but with the proper innards) that's been sitting for a while.  If they COULD sleeve down properly, use the TC as the base with the S2 innards...that would be the hot ticket, I think.

Going to have to make a decision soon; filled the reservoir a couple weeks ago, but when I checked last night, it was down again, above the 'MIN' line, but still down...

[jbcollier]

I have fitted a lot of master cylinders and worked on a lot of older cars.  Single circuit masters last much longer than duals and give far less grief.  Single circuits are also simple to install and bleed.  Fit a cap with a level sensor and you have all the warning you need if there is an issue.

I have seen both leak due to corrosion at the exposed end but only dual circuit masters have internal issues and bypass.  One famous example was when VW upgraded from single to dual.  Again no notable problems with the single but the dual was famous for going from good to ON-THE-FLOOR in an instant.  Yup, would bypass BOTH circuits!!  If you have a dual system, by all means keep it that way.  Just remember to change the master every 40K or so as preventative maintenance.  If you have a single circuit, just fit a sensor cap and thank your lucky stars.

[surfguitar58]

I'd like to know what you find out; I have a standard TC MC here, as well as an S2 (albeit rusty, but with the proper innards) that's been sitting for a while.  If they COULD sleeve down properly, use the TC as the base with the S2 innards...that would be the hot ticket, I think.

Going to have to make a decision soon; filled the reservoir a couple weeks ago, but when I checked last night, it was down again, above the 'MIN' line, but still down...

Bryan, would you be willing to lend me your S2 MC so I could do some reverse engineering on it? I have the TC MC drawn up in CAD and it would be great to do the same for the S2 MC to see if merging the two is feasible. I would gladly pay shipping both ways, obviously.
Tom

[Bryan Boyle]

Bryan, would you be willing to lend me your S2 MC so I could do some reverse engineering on it? I have the TC MC drawn up in CAD and it would be great to do the same for the S2 MC to see if merging the two is feasible. I would gladly pay shipping both ways, obviously.
Tom

Wish I saw this yesterday; boxed up both and sent to Apple Saturday afternoon with instructions to call me about what I was thinking.

I don't know if they can sleeve down the TC from .875 to .70/.75 or if the S2 is even rebuildable (the piston is well and truly frozen in the barrel...).  I had a spare S2 reservoir, but they are being reproduced again now, so didn't sent that along.  Hoping they can resurrect the S2 since that seems to be the preferred for a booster-less TC.  If not, and the TC MC is rebuildable, I've kind of gotten used to the hard pedal. 

I do know the one in the car is on its way out...the bottom of the cross box is damp with brake fluid.  Keeping an eye on it if (when?) I drive it.  I am NOT looking forward to getting at that top nut; thinking if worst comes to worst, considering the MC is leaking anyway, removing the two screws holding the back of the reservoir on, draining the fluid, swinging the reservoir out of the was as much as I can, to give me some additional space to get at the top nut.  I really think they put the master on THEN installed the steering rack.  Don't want to try and or displace the rack; those bolts going through the aluminium steering rack mounts are probably corroded in place...and I'm not going to risk snapping the bolts.  I have a spare set of rack mounts...but that job with the lack of clearance I can see turning into a real goat rodeo, if not incentive to pop the body off.  Either that...or judicious application of a sawzall...