The Stovebolt Site Forums The Shop Area Driveline Master cylinder upgrade

I was reading a post in the Greasy Spoon and it got me thinking. That can be a dangerous activity. Is there a two reservoir master cylinder that bolts in place of our current single reservoir OEM master cylinder? A simple bolt in replacement without a lot of conversion work? I have a 54 3100. Something that would segregate the front and rear brakes in case of a brake line failure so we would continue to at least have half our brakes.

When was the last time you experienced "brake line failure" in any vehicle, let alone a coddled classic? My guess is never. I'm not saying it doesn't happen, I'm just saying it's rare enough not to worry about. (this assumes that you're like the rest of us who checks under the hood all the time and notices the slightest change in performance of any system and deals with it appropriately).

Every vehicle I own with the exception of the F-Series pickups has a single reservoir master cylinder. I have never owned a modern car. I have never experienced brake trouble on the road due to a brake line failure or any other reason - including anything associated with a single reservoir m/c.

And no, I'm pretty sure there isn't an under-the-floor bolt-in replacement. You'd have to mount one on the firewall, re-jigger your pedal, etc.

Spend your time and money on seat belts.

Yes, there are kits. Try this thread:
https://www.stovebolt.com/ubbthread...nstall-issues-questions.html#Post1261987


BTW, we have had two brake failures with our old 1980 truck where dual m/c was helpful. Both times Fran was driving and she came home with only the front brakes working. First time she was stuck in snow so she installed chains. Chain came off on the highway and ripped out rear brake line. Second time the rear brake line failed due to corrosion.

Wow! That is a freak accident. Glad she was alright


I never heard of any under floor dual mc installed on an AD. I thought everyone had to hook them up on the firewall. Do you have to cut a bigger hole in the floor to fill the reservoirs?

I bought mine from jim carter. Comes with the bracket to bolt it right to frame and linkage that bolts to the stock pedal. Was super easy install. I was running all new lines and wheel cylinders at the same time so it made sense on my build.

Here are a couple more options:

https://www.performanceonline.com/1...s-Truck-Master-Cylinder-kit-Drum-Brakes/

https://www.classicchevy.com/chevy-...-transmission-1949-1954-80-366512-1.html

I second doing the conversion because I have blown brake lines on things as new as 10 years old. Having *some* brakes is a whole lot better than *no* brakes.

Not as freak as you think. Ford, for a while, was stating in their operators manual, on certain F150's, to NOT use chains because, even in normal use they could tear apart the rear brake lines. I guess the engineer that designed that new axle forgot all about folks that drive in snow.

My main concern is I removed my emergency brake some time ago and have not got around to reinstalling it because I had some rust issues and I will have to fabricate some stuff. It has been low priority but I think about not having a back up every time I drive it. I should just bite the bullet and fix the emergency brake.

Dgrinnan, Did you complete your master cylinder swap? I'm in the middle of swapping my m/c, all 4 wheel cylinders and rubber hoses.
Do you have any tips?
What m/c did you get?
Did you buy new brake tools? Where from?

I have not not. My brakes are in such good condition I have not been able to justify swapping them out. What I need to do is get my emergency brake repaired.

I can't remember where i got the bracket, but I used a master from a 1967 full-sized GM car- the first year of dual masters. The inspection hole doesn't line up perfectly but I am able to check/add fluid. Some guys have cut a bigger hole and fabricated a cover. Had to fabricate new brake lines but that was relatively easy.

Absent a catastrophic failure from tire chains or a wreck, usually you get a little warning. I have had cars and trucks come into the shop with corrosion pin-holes in the hard tubes, cracked and leaking hoses, loose bleed screws and other fittings and of course leaking wheel cylinders. The complaint has usually been, "pedal sinks slowly to the floor" or "its leaking brake fluid somewhere cause I have to refill it every so often;" or "the brakes pull this way or that or lock up suddenly."

These were complaints from naive drivers, not enthusiasts. My comment here is to say that if well maintained, a single bore MC is adequate especially on a doted-upon classic. That is not to say that a dual MC is not worthwhile, just that there are probably other things that take priority; like putting the factory equipment back in good shape: suspension, steering, original brakes, tires and so forth. They are the sort of thing that state safety inspections look for.

I agree. All my vehicles have single res masters. I've never had one fail on me.

I have the Performance Online under the floor conversion on my truck. It was a very simple upgrade and bolted right in place of my old master cylinder.

Regarding single circuit hydraulic systems, as with any hydraulic system , you must consider all possible points of failure, not Just the master cylinder- hoses, corroded steel lines, wheel cylinder seals, master cylinder seals. Although I agree that chances of something happening are small, but the ability to isolate one system from the other and guarantee that you will have at least two wheels with brakes if you bust a hose, is worth the expense and trouble for me, at least. The world is not what it used to be- the replacement parts available today are mostly inferior when compared to much of what was available 30-40 years ago. I don’t trust parts as much as I used to. Heck, they are even finding counterfeit parts in Boeing 737’s now… crazy. Brakes are probably the highest priority safety system on a vehicle.

Also, it was fatal accidents that led to an industry requirement that we have dual system brakes….

Nader’s buddy,

Dave

So this year I discovered that there are some cars that had a dual master with a single reservoir!! They rely on the safety or shuttle valve that is part of the setup.

I just completed my 55.1 half ton brake system upgrade. It snowballed a bit from a simple m/c replacement. NEW - dual m/c, 4 wheel cylinders, star adjusters, soft lines, hard lines, front drums, front hubs w/ conical wheel bearings, and turned rear drums... whew!
The m/c bracket, like the POL one above, is common, BUT creates a clearance problem if used with a T5. Fortunately, with a little extra work, the bracket can be reversed, putting the m/c about 6in more forward.
It all works great, and the m/c can be reached from the original floor cutout.

Don, Got any pictures of the work and finished install??? Could be helpful for other Bolters looking to do the same thing in the future.

I'm wondering about how many people actually have the engineering background to choose a correct master cylinder for a conversion, rather than allowing some "kit" provider to make life or death decisions for the end user? The bore size and stroke of the replacement MC will have a profound effect on the safety and reliability of the modified brake system, and a "Phase 10 Panic" situation during a brake failure isn't the time to discover that somebody made a deadly mistake about fluid volume or pedal stroke!
Jerry