Got in to a debate yesterday about single master cylinders being dangerous, and that I should change the single master cylinder in my '65 Coronet to a dual system.

My thinking is if a single system is in good repair such is the case with my Coronet, and I use my Coronet only for street driving, why should I fix what ain't broke? It was good enough when the car was new.

I'd like to hear pros and cons on the issue, please. Depending on the comments I may switch over. But it's going to take some convincing.

BTW, I have drum brakes.

If a front or rear line or wheel cylinder blows you will have no brakes. I had this happen many years ago in my driveway backing out and I ended up backing into a tree. You would be surprized how much damage was caused going so slow. I only run dual res masters now. I always think this could of been much worse if it was driving down the street when it happened.

I would not change it either! Beautiful car by the way! Even on a duel system if one side fails your probably not going to get the car stopped in an emergency anyway!

they do have a point, however, I am not sure how valid it is.

it is a safety feature that if one end blows out you will still have some partial brakes.

I have owned 3 cars with single pot masters.

1st car, single pot manual, I drove into a wall. But I was young and didn't know I had to check the level due to wear. So I ran the master cylinder empty.
would probably have been saved having a dual pot, just because both would not have worn as much that both would be empty.

2nd car I was a better driver. single pot but power drums.
Got on the emergency brake after the failure.
the rear drum lost a spring and blew out the wheel cylinder.
I was able to limp it home using the emergency brake through traffic.

Same car, somewhere on the way across country, the rear drum blew out again. ground down the star wheel and everything. honestly don't remember how, but I made it several hundred miles on that with only one side of the emergency brake working.

didn't need it, but could have been helpful in both cases having a dual pot master.


3rd car I switched shortly after getting it home, but only because I wanted power brakes.

All Max Wedge and early race Hemi's were single cylinder,they didn't seem to have a problem stopping at speeds most of us never see.No problem here!

The single will work fine until you have a failure as mentioned. There's a reason why they changed. Why risk it? Upgrade to a dual and you won't have to worry about it.

If you decide to stay with the single (or even if you upgrade), make sure your e-brake is in good working order and will stop the car if needed.

I can tell people that havent driven with the old single.Back then that is what they had.Ive lost brakes a few times with them.Not a very good feeling.Now Im one of the guys that hates change.I was still running point in the race car till a few years ago.One of the first things I did was go dual master.That and discs on the front.Yeah the brakes wont be great on a dual if you lose 1/2 the system.But you will still stop.Look at the old model A s.They still had mechanical brakes.Even the Ford club let people convert to hydraulic for safety.Rocky

I have old cars with both single and dual MS. Singles you have no brakes during a failure, duals you can always stop, especially by pumping up what's left. I have pinched off a bad line with visegrips to make it home on dual systems.

single pot master cylinder = widow maker.

these types of threads always crack me up.


guys spend thousands upgrading the engine, trans, rear end, adding a/c, running radial tires but when it comes down to something so simple and cheap as switching to a dual pot master cyl for a little extra safety they want to argue that their ancient tech. single pot is just fine.

Unless the goal is to have an all original reference show car,for me there is little reason to keep the single well.

Okay guys, after my "debate" Saturday and reading the comments here I'm going to switch over to the dual master. Plenty of good points made for it. Doesn't look like it's going to be much of a job to do it. Thanks for everyones comments.

Swap to discs on the front and you will never regret it either.I did my 65 about 10 years ago.ill never run drums again.I used all Mopar stuff so parts are plentiful.My kid still runs the 12 inch drums on the frt of his 300.They stop good but shoes are pricey.My 65 I can let go of the wheel at 120 and still stop straight.Rocky

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