Am I missing something... Old Car Brakes

Just got done reading my latest issue of Collector Car magazine. Nice article about old car brakes, all the usual nice topics, master cylinder, brake fluid, and stuff.

How come everybody misses the elephant in the room? Coefficient of Friction? The definition of brakes is coefficient of friction. I still do not understand why new car manufactures are not required to specify brake pad/shoe COF. If you are restoring or repairing any brake system if you put on the wrong brake lining it might never stop! the rest of the system could be preforming perfect. If you want to find out? spray some oil on your disks of your new car... it will take longer to stop than your Model T.

Had a friend of mine ask me this exact question, I sent him to "The Brake Place" in Minneapolis, they relined his shoes for his 1932 Nash 8, mechanical linkage, not only could it lock up all 4 wheels but he felt it stopped better then his new Ford truck.

We need to have the correct brake lining, for our correct period car, with the correct Coefficient of Friction for our brakes to work correctly.... what am I missing?

You are not missing anything. It is amazing how many people in the business or relining shoes do good riveting or bonding but don't understand COF. I have several original shop books about "Midland Steeldraulic" brakes (the kind on my car). The all mention COF and the fact that the lining on I/3 of the shoe has a different COF than the other 2/3. If I read it right the softer lining engages first and forces the secondary lining tighter, in effect a power assist. When put together with the right linings the pedal is very soft and the stopping power is great. Will lock all four wheels with less than 1/3 pedal travel. If you put the same lining on the whole shoe (either softer or harder) you get a haaaard pedal and poooor stopping. Don't ask how I know this. I found that to get it done right I had to reline my shoes myself after buying bulk lining from two different people. About twenty contacts before I found two suppliers that understood what I was asking for. Worth all the bother though.

The coefficient of friction between the tires and the road surface is equally important. The reality is that the brakes are a SYSTEM, and every single aspect of it plays a role in how well the car stops. This system includes the coefficient of friction between the road and the tire, the softness of the rubber, the lever arm on the tire, the lever arm on the caliper or shoes, the coefficient of friction between the shoes/pads and the drum/rotor, the slave cylinder diameter, the master cylinder diameter, the pedal ratio, and the force in any power booster. To make it even more complex, braking is a dynamic process, so static force calculations don't really apply. Theoretically, pad area, brake swept area, and tire contact patch don't even enter into the force equations, but they are very important when dynamics are analyzed. Pad area and swept area directly relates to heat dissipation, which affects COF of the linings. Tire contact area matters if you are travelling in anything other than a perfectly straight line. Etc, etc. Changing a single component without considering the whole system can make braking better, or make it worse.

One problem everyone forgets was the banning of asbestos in the eighties. At the time this caused a lot of problems with brake squeal and poor brake performance, even on late model cars.

I don't know if they have a new synthetic that is as good as asbestos, or if they found other workarounds. But it doesn't seem to get mentioned anymore.

Yes they have. You are absolutely correct when asbestos was outlawed there were no equivalents available, but now there are. We can thank industrial applications like punch presses, they use the same brake lining material we need, and likewise do not work without the correct COF.

Drum brakes typically had both a different lining length and different lining material on the primary and secondary shoes. When you look at older shoes you can often see the PRI or SEC on the side of the lining and the different COF was for a reason. Today's replacement shoes for collector cars generally have the same lining material on both shoes and that is a contributor to poorer performance than with the original materials, not to mention the asbestos replacement lining material. Fortunately you can still sometimes find PRI and SEC lining material in original asbestos in bulk but you'll have to cut, chamfer and install them on your shoes yourself - no brake shop will touch the job.

The other aspect is drum material. Steel drums were not brilliant. It is recorded in Hendry's book on Cadillac that when they changed to cast iron early in the production of the V16, the brakes improved a lot. I rebuilt very worn steel drums for people in the past with wire-feed metal spray equipment that used acetylene/

oxygen as heat source. Metco Spraysteel LS was the correct material. It is a work-hardening machineable carbon steel coating, with a significant molybdenum alloy content. It has similar friction character to cast iron, and you use modern linings. While I still use this for my own work and for friends, the current cost of commercial bottle acetylene is prohibitive if I needed to do jobs for outsiders. The same coating can be applied by electric arc spray equipment, with feed from two spools of smaller diameter wire of the same material. One friend had a small (genuine Antique English Perry car, made before WW1. The brake drums, which were integral with the rear hubs, had worn till you could see small patches of daylight through because of the cast iron linings. A good many years later I ran into Barry at Bendigo Swap, and he commented that they had the back axle apart, and that the drums were still perfect. He further stated that it was the only car with cast-iron brakes in the Veteran Car Club that the brakes worked properly and did not squeal. I said "Barry, I told you to use modern lining material". He laughed and said "I did: Modern cast iron!". I would have to search my old docket books, but I must have done that 35 years ago.

I have the 1929 chevrolet and am checking on the brakes as oil has leaked through the axle bearings onto the linings. Is there a way to clean these brakes or is it better to just replace. I might have to buy the linings and do it myself. Which way to go . Thanks Phil

Sounds like new bearings and seals are needed as well as new linings.

Often the seals leak because the bearing allows too much lateral movement by the axle.

One of my mid twenties shop books says to clean brake shoes with white gasoline. Let dry and reinstall.

PS:

it does work but don't smoke while doing same.

If you happen to get some oil or grease on a brake lining while working on the brakes it will clean off with Brake Kleen spray. If they are really soaked, best to replace them.

Easiest to clean oil off brake linings is one of the dedicated pressure pack cans that parts houses sell for the purpose. They now contain solvents that are much milder that the carbon tetra chloride that used to be popular: It is now considered politically/environmentally improper to spray "carbon-tet", even on someone obnoxious. Early January last year I drove to Queensland to visit my sister, and then my friend who is the other Mercer owner. Late at night I stopped to rest and sleep beside the Highway. When I woke to travel on, I found that a rear wheel bearing had broken. My very modern 1981 Toyota üte", (which I know some of you folks would think of as "antique "because of your sliding time line) stalled the engine when I tried to start in first gear, but it would move in reverse. So I backed to a flat spot further off the road, and slept on the tarp on the back. (That gave Rhett, my son, more room for comfort in the cabin.) First light I chocked the front and jacked up both rear wheels. There was diff oil everywhere from the left back wheel, and surprisingly, it turned smoothly in either rotation without vertical load on it. I had no mobile phone coverage, probably because the highway was busy with B-doubles and tourists in 4wheel drive "fat-wagons". Anyway, there was no-one I knew within 200 miles that could help me. So, I pressed the "bush mechanic's logic button". I crawled under, and adjusted the shoes out till They dragged nicely in the drum all the way round. I dropped the wheels on the ground, packed everything away, and started very cautiously in first gear. There was no noise or roughness so I drove over 60 miles at 20mph or less, well out of the traffic on the two-lane Newell Highway on the shoulder, waving everyone past with the hazard blinkers on. We reached Repco at Goondiwindi at 11.30 on the Saturday morning, and I bought a 20v battery angle grinder with two batteries that had residual charge, a compact trolley jack, and two new seal-and-wheel bearing kits. You see, if the first original bearing died at around 450,000 miles, you could bet sixpence to a greasy boot-lace that the other would not last much longer. Well, next priority was to get breakfast/lunch for my autistic son at a well-known American fast food franchise: But when I went to pay, I no longer had my credit card. So, I slowly drove back to Repco as quickly as possible; but my card was locked away inside till Monday morning. (They trade Saturday afternoon and Sunday morning in Victoria where I live.) So, I parked under a good shady tree on the main drag back to the Newell Highway, out of everyone's way; and I started to pull the axle out. It was around 108 to 110 degrees F that afternoon. So I started to pull the axle out. A very nicely equipped mechanic's 4wd ute pulled up on the service road, and Les asked if I needed any help. I said that was very kind of him; but that I had everything I needed, and I was in no hurry because I could not get my credit card back until Monday morning. Les said "I'll get that back for you. I know those girls." And off he went. Of course he knew their first names; but he did not know their surnames of mobile phone numbers. It took him over 3 hours , using his network, to speak to the manager. He said he would have my card at the back door at 7.30 pm, after he got back to town. I then had everything apart and mostly cleaned up when Les got back, and he took that bits and the new kit except the inner seal, because he obviously had a press at home, which makes assembly much easier. I had everything clean and ready when he got back. I was pretty much into sleep deficit, and a bit slow and careful. Now there had been a girl who had stopped a couple of times earlier, and wanted to bring cool drinks for Rhett and I. I told her she was very kind, but that I had plenty of cold water and bottle drinks; and that Rhett was very comfortable and well hydrated. Then she stoped again and insisted on giving me two small burgers and two bottled drinks; and would not let me pay. An older lady who apparently lived across the road, and knew Les, stopped and asked him if there was anything she could do to help. So she brought back my card. There had been some talk that I should find a motel room, so it must have been obvious I was about past the end of my shift. When she returned she gave me my card, and a piece of paper with "Queensland Hotel" written on it. She told me it was just back towards the shopping strip; and there was a room booked for me if I wanted it. It was getting dark when the brakes were bled and adjusted, so I headed for the hotel.

(The well-oiled brake that had carried us 60-odd miles as makeshift wheel bearing had cleaned up with solvent and rags, and has worked fine for15 months since).

I went into the lounge, ( Rhett went somewhere else ), and the head waitress was Brooke, who had wanted to bring us drinks all afternoon. I gave her the note as instructed. She said "Good. Your room is number 2 at the top of the stairs. It is paid for, and so is your meal and your drinks. What would you like to drink? I'll bring them to you with the menu. Just sit wherever you like." I said that I would be much more comfortable to pay for it myself. She said "I am sorry, you can't. People have already paid for it." When she brought my cold water and ice, and Rhett's lemon squash, she tried to make me order expensive steaks. I ordered the least expensive item. I was much less hungry than very tired. The Toyota Hilux Motel is about the most uncomfortable place anyone could not want to sleep. This was an old wooden hotel of the same era as the pub in Crocodile Dundee, but this was two storey.

This is our traditional Australian country culture of consideration, helpfulness, and generosity; and it is far more valuable than the "multi-culturalism" that the political mind-benders like to rabbit-on about. Goodwill is the most valuable commodity that we can create and pass around, and it needs to be exchanged and compounded wherever possible. My Mercer friend John Hancox was down and back to Queensland before Christmas. He delivered a box each to Brooke and Les, virtually the same to each, with a really good 10 inch square fruit cake , ( home-cooked), a canister of chai tea, a good recipe book, and a note of appreciation and explanation. I'll be able to get details so he can take back similar for the lady I was not able to do it for at Christmas. Helping someone gives you greater satisfaction than anything else you can ever achieve. ( I have helped people broken down on the road. I did a major radiator rebuild late one Saturday afternoon for a lady who was stuck and stranded) .

I only wrote to assure you that cleaning oily brakes is fine. I hope the storey has not bored you.

Ivan, great story. I can and will attest to the friendly folks in Queensland. I enjoyed my stay in Brisbane in 1968/1969.

Ben

Ivan,

I agree, what a great story. Everything was great except I never acquired a taste for fruit cake. If you every get to Detroit and need help, call.

Larry