Hot Rods Not comfortable with this.

I've got to agree with Gimpy, if it stops quick enough and stops straight every time that is a big plus. I don't know what tires the car has and if they are skinny bias or wide radials but that wold also have a factor. If the car has big meats on it it may not slide the tires as the traction of the tire may over come the friction of the brakes.

 

Why don't you measure stopping distance from 60 mph and get back to us? Or at least the guys who know more than me.

 

Call Ralph at ECI..Ask him what he thinks about not being able to lock the wheels..

 

What I think the poor guy is trying to say is, with the braking system he has on his very light vehicle you would think all 4 wheels would lock right up but they don't.


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I could try that.



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Coker excelsior radials 7/60 16 on rear 5/50 16 on front


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7/50 16


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Is Ralph at ECI a Master Mechanical Engineer?

 

If these are the Lincoln backing plates from Bob Wilson, you need to slot the hole for the top anchor bolt for the shoes so that you can center the shoes. Are the shoes only touching the drum a little?

 

I believe they are Wilson brakes and they seem to be seating evenly.


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But l will take another look at it Sat.


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look at the shoes to see the wear points. You need to vertical-slot the backing plates, leave the nut on the anchor bolt just barely loose enough that it can move, adjust the shoes out to the max, then bang on the drum. That should center the shoes, the tighten the hut on the anchor bolt

 

I have a 40 Ford with disc drum and a 50 Ford with disc drum.


I can slam the brakes on them and get skid marks.Maybe the front drums are giving me a different feel.


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what linings did you use? have the shoes been fitted to the drums? can you pull the drums and look at the wear on the shoes and report back?
i have found "bad" linings that just didn't work. i did brakes on an off topic every day driver[s10 blazer] and it wouldn't stop right. i checked everything, then bought a different set of pads and it was perfect.
i would bet with a heavier car it wouldn't stop.

 

At low speeds on a dry surface in a straight line, locking the wheels provides the shortest stopping distance. At higher speeds, the melting rubber could lubricate the surface more. The driver applies the proper pedal pressure to make the brakes do what is desired. Antilock brakes help provide control for people who don't know how to drive which seems to be the normal thing these days.

 

The additional pressure is like pushing on the pedal harder. That will push the linings against the drum harder to create more friction. Asbestos linings had more friction. Just like tires, softer friction material has more traction but wears faster. Carbon fiber has to be warm to work best. Have you tried pushing the pedal with both feet to see if a little extra pressure will help? That might give you an indication of how close you are to lockup.

 

Maybe? I think yes.

 

I believe this is factually incorrect. The maximum grip of a tire on the road surface, and hence the shortest stopping distance, is just before lockup/tires skidding. A skidding tire increases stopping distance and, as stated in prior posts, also contributes to loss of steering control for the same reason. Locking up brakes and skids are not a good thing in the majority of driving conditions......boot leg turns maybe, but seldom otherwise.

As for people not knowing how to drive, there is lot of truth to that, but it has much less to do with braking than a whole host of other factors. "Panic Stops" are called that for reason and it is a rare and highly trained individual who would be capable of self governing the pedal pressure applied in an emergency stop situation to modulate tire grip.

Ray

 

As Hotroddon said, that residual valve is the answer. Many '60s cars used the same basic master cylinder for both disc/drum or 4 wheel drum applications, but either application had their own part number due to the disc/drum unit having no valve for the front brake circuit. On Holdens of that era we used to convert a drum/drum unit to a disc/drum unit by removing the appropriate valve...

 

Good idea.I'll try it.


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A residual cannot cause early braking, although your vintage style fronts should have one, to prevent air from entering the wheel cylinders, the residual's purpose.
Always best not to easily be able to slide the tires. Your best deceleration is always just before any tire slide.

 

On a 4 drum system, having a residual pressure valve on only one axle CAN cause those brakes to apply sooner than the axle that does not have the PRV, as the brakes on that axle can easily get a small amount of air which will have to be compressed before the brakes apply. This is very common on older wheel cylinders that do not have cup expanders (whose job it is is the keep air out as well).

 

Sorry, but this is Wrong. A tire that is skidding is exhibiting Kinetic Friction. A tire that is Not skidding but had maximum braking applied is exhibiting Static Friction. The laws of Physics tell us that the coefficient of Static Friction is much higher than that of Kinetic Friction - hence shorter stopping distance when the tire is NOT skidding. And the laws of physics don't change based on the speed of the vehicle.

 

This is what was drilled into us at work....and demonstrated

 

There is a residual valve to the rear brakes plumbed in line.The residual for the front brakes is built into the master cylinder.


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I will throw this tidbit in to add to the discussion, although it has little to do with the original post. Sometime back in the '80's, I read that maximum braking efficiency occurs when the wheels are turning at 85 percent of the speed they would be turning if freewheeling (or without the brakes applied). That does not take into account the loss of directional stability, but was supposed to be the point of maximum braking efficiency. Obviously before the advent of 4 wheel anti-lock brake systems. I too, would be concerned with a standard brake system that I could not lo k up the wheels withi

 

That is to say, that I could not lock the wheels up with.

 

Why not get a proper Master Cylinder that is Drum / Drum, not Disc / Drum?
Huh?

 

I agree with everybody. It's not that locking up the brakes is a good thing but if an old school brake system won't lock up at the extreme, something ain't right. Shoes aren't ground to fit the drums anymore and the materials are different now so it takes longer to get them to work right. Somebody once suggested "pink linings" that truck shops can use to reline shoes.

There is a bedding in process with new brake friction material too, they need to get up to temp i.e. pretty much smoking hot so's you can smell 'em. Has something to do with the resins and binders baking off, otherwise they will soon glaze over they will never brake for shit. Can try sanding them with maybe 80 grit or something like that and bed the linings in on the highway.

When I was first stationed in Europe I noticed all the cars and beemers and benzs had tons of brake dust on all the wheels. Never saw that in the states. I found out "over there" they use a softer steel rotor material and, metallic pads. The brakes are often noisy, with a grinding noise. And maybe they don't last as long, I dunno. But I bought a used 3 series to bomb around in, and it had the best brakes I ever had on any car I've ever driven. I didn't know a car could stop that fast. I'm glad too, cuz I needed to.

 

Your Mustang disc/drum master is plumbed wrong. The port with the internal residual should (always) go to the rears, and will be from the visually smaller fluid reservoir.
Pedal ratio has been brought up, but you never stated your actual ratio.
Are you sure you can fully stroke the pedal without any binding or interference, and that the master bottoms before the pedal? (Open both circuits to perform this check)