I have a 1951 chevy 2 door, 16000 miles. I rebuilt the brake cylinders and master cylinder. The front shoes have nice pads but the rear shoes are a little thin but do not grin. I'm using DOT 5. Question is, how much pedal pressure should it take to stop car. I really have to push hard to slow car. It does stop straight but the amount of effort to stop car does not seem right to me. I can not picture a women back then being able to push as hard as I have too. I guess I'm spolied by having power brakes. What say you. I'm not sure if that is the way it is suppose to be. This is the only early chevy I have driven so I have nothing to compare to.
Going say 25 MPH with resonable pressure the brakes should almost or fully lock-up. The 1951 had the new for Chevrolet Bendix self-energizing brakes and require resonable pressure for a car with no power brakes.
If the rear linings are thin the car has much more than 16,000 miles. The brake shoes on a 1951 has linings bonded to the shoe, no rivets. and a shiney brownish lacquer on the shoe metal. The rears would go at least 35,000 miles before linings loooking thin.
DOT 5 fluid has a tendency to pickup air and if so will require more pedal pressure. First to compress the air and then a little more to move the shoes. I never had a problem with my '51 requiring excessive pedal pressure even with worn linings. With new linings it stopped with less pressure.
Here are my ideas that could improve braking.
- The shoes are glazed and need to be replaced regardless of thickness.
- The 3 hoses in the system have swollen with age and need replaced.
- The drums need turned to remove the taper. This means that the braking surface on the drum is not parallel to the face of the shoe.
To further reduce pedal braking pressure you can install a 1953-54 master cylinder. It has a smaller 7/8" bore compared to your present 1" bore. Will reduce pedal pessure but slightly increase pedal travel.
Through the years I have used both conventional and silicone brake fluid and never noticed any ifferemce in pedal pressure. To avoid bubbles in the silicone if you are using the pumping up of the pedal version of bleeding pump the pedal slowly.....
Thanks for the replies. I believe I will go with new shoes all around. They do have a glaze to them. Question about brake shoes. All the auto stores have shoes with full linings, no seconary pad shoe. Is there a problem with using full lining shoes. And what was the purpose of making the opposite shoe lining shorter in length.
The short shoe forces the long shoe back so it does less work. The longer rear shoe lining will wear faster as it does 70% of the braking force. That being said I do not think it would make that much difference......The one shoe pushing the other is the self energizing feature of that style of brake.
I normally quickly agree with Gene because he is a lot smarter than me and has a whole lot more experience with theses old Chevy’s.
In this case I have to recommend that you do some research about using equal length shoes on a self energizing brake. If the front shoe is too aggressive it will quickly overload the rear shoe and lock the brake. This will definitely happen if you install the short and long shoes backwards.
I can remember replacing shoes on self energizing brakes when the linings were the same length but different materials. The instructions were very direct about putting the less aggressive shoe on the front. Normally the linings were different colors.
It is correct the short shoe and long shoe had different lining and were of different lengths. The junk sold today does not work as well as the old asbestos linings and shoes with unequal lengths, etc, are almost impossibe to find.
If it were my car I would sand the linings and drum braking surfaces , not turn the drums as it will take many miles to get full lining contact and give it a try. Also if there is air in the system more pedal effort is requires as you are compressing the air to move the shoes
With all due respect...
I believe a clarification is required here. :-)
Air in the brake system will NOT increase the pedal pressure required for any given braking effect.
With any hydraulic/pneumatic system, pressure in equals pressure out.
It doesn't matter if the medium is a liquid or a gas.
What WILL change is pedal TRAVEL due to the change of volume of a gas (air) under pressure
And the possibility of bottoming out the master cylinder before the required pressure is reached then exists.
And of course if the master cylinder does bottom out, no amount of pedal pressure will be enough.
So, air in the lines equals spongy brakes.
But as long as you have enough pedal travel, you WILL be able to generate the same braking effect.
PS
It is true however that due to the geometry of the linkages involved, foot force at the top of the pedal travel may generate more hydraulic pressure than the same amount of foot force near the bottom of the pedal travel.
Which is why it's best to keep your brakes set up properly.
Just a note - It has been my expriance that it takes more pedal pressure to stop with air in the system - probably due to the fact tht the air needs to be compressed to apply the brakes and fluid does not.
When the 1951 and 1952 cars were new we had a lot of complains that brakes pulled one way or another. Magazines that did roadtests also mentioned the problem, especially in panic stops. The zone Chev. Rep. said is was just a problem in this area due t humidity. Chevrolet had all kinds of service tweeks. Nothing changed untill we installed some after market relined shoes with the same linings on front and rear shoes and qit using the genuine shoes.
Hi Gene
Requiring more pedal force with air in the system would be due to the geometry of the linkage as I mentioned above, and the resulting position of the pedal at full shoe contact.
Whether you are compressing air, or TRYING to compress fluid, the pressure the wheel cylinders get is entirely dependent on the force applied to the master cylinder piston no matter what is in the lines.
As an example of this...
Ever notice that if a car has no air in the system but is in need of having the brakes set up, such that the pedal goes down 2/3 of the way or so to get full braking...
and you pump the brakes once or twice so the pedal is at the top or it's travel...
you get much stronger brakes for the same amount of foot force?
Interesting info on the after market shoes by the way.
So using NOS Chevrolet shoes, even if you could find them, wouldn't be the best idea then?
Just purchase an NOS set off ebay. They are not GM parts but do have the short lining and hopefully old enough to have asbestos linings. I hope I can install the shoes without having to bleed the system.
Is your car a standard shift or a Powerglide? The reason I ask my 50 was exhausting to stop with the Powerglide, there was very little help with engine compression ( I was never a fan of downshifting) My friend had a three speed his was much more efficient to brake. That style Powerglide changed in 52 I believe and had a downshift point aiding in stopping.
It's a powerglide 1951 car. It's not bad enough that i would use tranny to help stop. Installed the new shoes and that helped but seems like it could be better, maybe.
give the new shoes a chance to wear in and make full
contact with the drum surface.
I ask for a softer lining when my shoes were rebonded. Dont know if you have that option in USA. Gene is right . It takes some time for the new linings to bed in before making a braking judgement.
It should certainly stop better than my ‘50! Unless the drums are deeply scored or out of round, I’d recommend not turning them. I’m fortunate in the fact that there is a shop near me that still does clutches and relines brake shoes. Yes, allow the shoes to wear into the drums, difference in radius and contact with drums makes a big difference in stopping power.