Hydraulic brake balancing
 

Has anyone had problems balancing brakes on hydraulic conversions (46-48 backing plates) ?
Brakes have been re-bled with no air found; mechanically adjusted each brake to just before drag - but it’s repeatedly pulling left, with only the left front with decent braking effort. Any further tightening of right side brakes causes lockup while adjusting.
It appears the left front (with the shortest hydraulic line) is getting activated first, and the others are not catching up. Hard stopping on gravel, locks the left front only.
(Are there any restrictors in the hydraulics, like modern vehicles, to make up for the difference in hydraulic line length ?)
There are less than 100 mi on this restoration when the hydraulics were added.
Missing something here .....

Thx

Re: Hydraulic brake balancing
 

It could be several things.
Try looking at the right wheel cylinder. Check inside for free movement of pistons. Check that shoes move freely on the pivots. Check for pinched or kinked line somewhere from the left to right front. Check hose for obstruction.
You should need NO proportioning valves or restrictions in that system.
You should be using 1/4 inch STEEL tubing for lines.

Re: Hydraulic brake balancing
 

Did you get the primary and secondary shoes in the right location on both sides??

Re: Hydraulic brake balancing
 

The hydraulic lines are large enough that the extra line length to the R/H wheel cylinder should not make any difference at all. With everything adjusted and completely bled, there is actually very little displacement of fluid when the brakes are activated.

You have some other problem than the extra length of line to the R/F. Restriction in a line, fitting or hose. Wheel cylinder sticking, lining contaminated, shoes not properly arced to the drums or a problem with the assembly of the shoes.

Chris W.

Re: Hydraulic brake balancing
 

In addition, it may be a bad/collapsing flex line. Have you tried backing off the left side ?

Re: Hydraulic brake balancing
 

I am afraid that I agree with the others that there is something wrong with the braking system, not just the adjustments. If you are not competent to analyze the problem and fix it then take the car to a good brake shop.

There is no effect in the length of the hydraulic lines.

Re: Hydraulic brake balancing
 

One other thought: There are three adjustments for the brake shoes in hydraulic systems. There is the adjustment at the stationary ends of the shoes, but also the ones at the centers of the shoes. If you just adjusted the one at the ends of the shoes then you will get uneven braking. I ran into the uneven braking problem with my converted coupe until I figured this out.

Re: Hydraulic brake balancing
 

Are all of the shoes the same? Bought at one time from the same place and look identical?

Charlie Stephens

Re: Hydraulic brake balancing
 

I had some wheel cylinders that had the drilled passage bringing fluid into the cylinder about 3/16 inch down the bore from the base of the cylinder, maybe even farther. This cylinder didn't want to actuate the piston when the brakes were applied, I dropped a bit of plastic into the cylinder before putting the piston in. That cured the problem while I searched for cylinders that were drilled properly.

Re: Hydraulic brake balancing
 

Had a 39,and 46, when I had such problems it was from wheel cylinder leaking onto linings, after years of having to work on one car or the other for brake problems and failures I solved the problem--- sold those cars, now have a 36, and model A because they have reliable mechanical brakes , had the A almost 50 years, figure next year I should go through then and clean, lubricate and correct what I didn't know what to do exactly as a 15 year old

Re: Hydraulic brake balancing
 

I am not sure why you would need hydraulic brakes on a Model A. My mechanical brakes are adjusted properly and I can lock them up whenever I like.

Re: Hydraulic brake balancing
 

Ditto

Re: Hydraulic brake balancing
 

I had severe problems with my hydraulic brakes aa well. I have a brake booster on mine and the car would dive to the Center of the road. I am using DOT 5 brake fluid. I tried adjusting heavy to the passenger side and nothing worked. I noticed a dampness on the left front wheel cylinder. I removed the new leaking wheel cylinder and found porosity in the bore. Most of these wheel cylinders are made in China and they are junk. I measured the cylinder bores and it was not within specs I went hunting for made in U S. A ones and no luck. I found that Raybestos cylinders are made in China but they have quality control. I put the new wheel cylinder in ,no leaks the car still dived. I removed the brake shoes and steam cleaned them ,brake-cleaned them and the car was better but not perfect. I went to a old timer that owned a brake and muffler shop and he said throw the brake shoe away and put a new one in. He said you will never get the brake fluid out of the lining. I did what he said and it cured the problem. These hydraulic brakes can be a problem but once you figure it out, they are really good. My car pulls straight on a panic stop and It will lock all four tires . Also when you buy a new wheel cylinder, take it apart and inspect it and measure it.

Re: Hydraulic brake balancing
 

I have heard many stories like yours. As for made in China stuff I work in manufacturing and I have seen nothing but issues with China metal. If the part is not structural it may be fine but if you need it to perform forget about it. The Metallurgy tells the story when you look at the chemistry and micro structure of the metal. I have come to the conclusion that ASTM Standards are optional in China.

Ron

Re: Hydraulic brake balancing
 

I had severe problems with my hydraulic brakes aa well. I have a brake booster on mine and the car would dive to the Center of the road. I am using DOT 5 brake fluid. I tried adjusting heavy to the passenger side and nothing worked. I noticed a dampness on the left front wheel cylinder. I removed the new leaking wheel cylinder and found porosity in the bore. Most of these wheel cylinders are made in China and they are junk. I measured the cylinder bores and it was not within specs I went hunting for made in U S. A ones and no luck. I found that Raybestos cylinders are made in China but they have quality control. I put the new wheel cylinder in ,no leaks the car still dived. I removed the brake shoes and steam cleaned them ,brake-cleaned them and the car was better but not perfect. I went to a old timer that owned a brake and muffler shop and he said throw the brake shoe away and put a new one in. He said you will never get the brake fluid out of the lining. I did what he said and it cured the problem. These hydraulic brakes can be a problem but once you figure it out, they are really good. My car pulls straight on a panic stop and It will lock all four tires . Also when you buy a new wheel cylinder, take it apart and inspect it and measure it.

Re: Hydraulic brake balancing
 

Brake fluid on the lineings.

Re: Hydraulic brake balancing
 

Any progress yet ?

I was thinking these were center-plain, they're not.

So, check that shoes are installed correctly. These have primary and secondary shoes. Primaries are short, secondaries long. Primaries go toward the front, secondaries rear. I've always been surprised at many times they are installed incorrectly, happens a lot.

As mentioned, check shoes for contamination. It that happened replace them. Why were they contaminated in the first place ?

Make sure they are adjusted correctly.

If all this is correct, a flex hose could still be collapsing. Doesn't happen often, but, it does.

Re: Hydraulic brake balancing
 

Thanks for all the feedback.

Not sure what ‘good brake shop’ suggested adjusting the stationary and the middle adjusters, but ‘46-48’s only have middle adjusters.

Did find a little (DOT5) fluid on the right front, so after this weekends show, looks like I’ll pull all the drums and check the cylinders for leaks.

Thx

Re: Hydraulic brake balancing
 

I stand corrected. My brakes must have been a different year as they had the little star wheel at the bottom. Or, that was maybe 55 years ago, so the brain cells that held that information may be gone.

Pdgx, please post your fix when done so that we may all learn.

Re: Hydraulic brake balancing
 

The problem I had was: My master cylinder did not have a check valve.
Drum brakes should hold 10 pounds of pressure in the lines.