Lotus Europa Forums > Garage
Brake Master Question
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:
--- Quote from: surfguitar58 on Saturday,April 27, 2024, 12:42:10 AM ---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
--- End quote ---
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:
--- Quote from: Bryan Boyle on Saturday,April 27, 2024, 05:58:41 AM ---
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...
--- End quote ---
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:
--- Quote from: surfguitar58 on Saturday,April 27, 2024, 07:12:47 AM ---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
--- End quote ---
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...
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