Them's The Brakes
Oct. 25-Dec. 10, 2006
 Lynn poses behind Penny's steering wheel (Oct. 29, 2006). |
Jump to:
- Give Me A Brake!
- A Sixteen Tripper
- The Road Test
- There's A Whole Lot Of Shake'in Go'in On
- A Switch For Improved Safety
- Was The Seller's Description Accurate?
Give Me A Brake!
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Penny's front brakes before renewal — left-front wheel (left two photos), right-front wheel
(right two photos).
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Lynn quickly discovers upon acquiring Penny, the car is in need for immediate attention to the brakes. He finds that the car shutters and the pedal pulses strongly (one or more brake drums out of round) when the brakes are applied. Lynn notes that the emergency brake is not working. Let's see what Lynn finds on closer inspection.
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Penny's rear brakes before renewal — left-rear wheel (top row), right-rear wheel
(bottom row).
Lynn sees evidence that the rear brake parts had been recently painted.
The right rear wheel cylinder is leaking from both ends and the emergency brake
cables are missing (reason for no emergency brake).
Lynn also notes that the rear brake linings will need to be replaced soon.
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The master cylinder is leaking past it's front seal and needs to be replaced.
A subtle problem is also highlighted in the photo by the red circles.
Someone has replaced the two front 1/4" brake lines with 3/16" tubing, a reduction in
cross-sectional area of the lines leading to the front brakes by over 30%.
Essentially, the balance of braking on Penny has been shifted from the front wheels
(which should normally do the bulk of braking) to the rear wheels. YIKES!!!
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Lynn finds that Penny's brake drums have been resurfaced recently.
The front drums (left photo) are straight and round to ~0.001" — that's good.
But the nominal 12.000" front drums have been cut to their maximum safe diameter of 12.060" and
can not be resurfaced again in the future — not so good.
The rear drums (right photo) are a outside spec.
The nominal 12.000" rear drums have been cut to about 12.160"; more than three times the maximum
safe metal has been cut from their surface.
They are badly warped with a runout of about 0.060".
The bad warp is probably a direct result of the removal of too much material from the drums and the
wrong size front brake lines which makes the rear brakes work harder, compounding the problems
with the thin drums.
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A Sixteen Tripper
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Penny's brakes after renewal — left-front and right-front wheels (left photos),
left-rear and right-rear wheels (right photos).
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On Wednesday (Oct. 25), three days after getting Penny home, Lynn orders virtually a complete new braking system (shoes, springs and clips, wheel cylinders, master cylinder, hoses, emergency cables) from Kanter Auto Products. By Thursday (Nov. 2) the parts had arrived and Lynn begins the tear-down. The only brake parts that Lynn has not ordered are the brake drums, brake lines and backing plates.
During that weekend Lynn finally understands the subtle issue with the undersized front brake lines. All new 1/4" brake line is bought at a local auto store and installed on Sunday.
By Monday Lynn has diagnosed the unsafe rear brake drums. After looking in a recent issue of Hemming Motor News, Lynn locates new rear drums for Penny at Northwestern Auto Supply.
Lynn requests that the rear brake drums be 3-day express mailed so that they arrive on Friday (Nov. 10). He has registered Penny to participate in the Goodguys 17th Autumn Get-Together, to be held Saturday and Sunday (Nov. 11-12). He's calling it close, but he thinks he can do it. To maintain his plans, Lynn pulls a couple of his now famous work-until-the-wee-hours-of-the-morning then go-to-work-the-next-day-anyway nights, staying up until 3 AM Monday and 4:30 AM Tuesday. Yes, he does feels like heck the next day.
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The new master cylinder (left) is installed with new, matching 1/4" brake lines for both the
front and rear brakes.
Note the complete lack of rust or corrosion in this view of the bottom of the drivers floor pan,
the black sheet metal above the master cylinder.
Lynn finds the unique brass coupling at the rear of the master cylinder has fatigue cracks. He brazes the cracks shut and machines the mating surfaces flat (left center).
What is with that blue electrical cable that's just draped over the rear axle and the
missing brake line/hose bracket (center right)?
A new bracket is fabricated and is shown from a different view after installation along with the
new brake line, hose and emergency brake cable (right).
Lynn moves the blue cable to the side for now, another irregularity in the car that
needs to be addressed at a future date.
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Lynn has an off-beat metric for gauging the difficulty of a job, how many trips he needs to make to the hardware/parts store. This brake job on Penny takes over sixteen visits to Orchard Hardware Supply, Monument Auto Parts and Kragen Auto Parts. On Saturday Lynn makes six visits and eight more on Sunday. The unusually large number of trips is generated by the replacement of the brake lines and Lynn's difficulty in finding the right combination of fittings to connect the new lines to the master cylinder and the repair of the fatigue cracks in the brass coupler.
The Road Test
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Old and new rear drums compared. The new drums (center) are close to their nominal diameter of 12.000",
while the old drums (right) at about 12.160" are well outside the 12.060" maximum diameter.
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On Thursday evening, Lynn adds brake fluid and starts to bleed the brakes to remove the air in the system. It's a good thing he started before the drums arrive because he finds several leaks! One major leak involves the complicated plumbing at the back of the master cylinder. After some more time with the torch, the addition of some copper gaskets, and additional tightening Lynn finally stems all the leaks and successfully bleeds the air from the system.
The new drums arrive as promised on Friday, Nov. 10. It takes Lynn only a few minutes to replace the old drums and readjust the brakes.
A quick road test around the block confirms that the car stops but there still seems to be a problem. Oh well, everything appears to be in good enough working order for the drive to the show tomorrow morning. Yahoo! A further investigation will have to wait for later. Until then Lynn will be driving gingerly until he can isolate the problem(s).
There's A Whole Lot Of Shake'in Go'in On
The drive to the Goodguys meet the next day is a big disappointment. In spite of an investment of nearly $1,000 in parts, the car still shutters and shakes when the brakes are applied at any speed over about 10 MPH. This is not a subtle irregularity. The steering wheel wildly shakes in his hands, rattling the horn button, and the brake pedal madly pulses under his feet. The car is not a happy camper and Lynn is frustrated that he has failed to discover what rotating part of the brakes is seriously out of round. The response of the steering wheel means that the front brakes are definitely involved.
The only components that Lynn has not replaced are the front drums, the backing plates, the front spindles, rear axles and the bearings. He was assured that the front drums were true by the mechanic that reported the distorted rear drums. Lynn is now suspicious of that diagnosis.
On Friday, Dec. 1, Lynn sets out to find the root cause of the problem. He takes all four drums off the car and inspects the components again. He pays special attention to the backing plates (looking for looseness or damage), the front spindles and the rear axles. Everything seems to be in order. OK, he concludes, it's the front brake drums.
Lynn sets off to see Don Johnson, a elder machinist in Livermore that did a great job turning the slotted and cross drilled rotors on AtomAnt, a job that others wouldn't touch. Don is very particular about the setup of his machines and personally rebuilds the machines and creates the fixtures and other components to make sure that the tools cut straight and true. Don mounts all four of the drums and finds that they're all OK -- the runout is only about 0.001-0.002". What? Lynn would not have believed the result if he hadn't walked up and inspected the drums on the lathe himself.
Lynn returns home and does another thorough inspection of the brakes examining the bearings closely. Lynn can find nothing wrong until he torques the wheels on the car. He finds that brake shoes that he has just adjusted to have an optimally low drag on the drums with the wheels off suddenly bind. He doesn't know why, but the wheels appear to be distorting the brake drums! Finally Lynn has a lead on the source of the problem.
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Lynn discovers that the inside of the wheels are pressing on the outer edges of the brake drums,
distorting the drums when the wheels are bolted on the car.
About 30 minutes with an angle grinder is all Lynn needs to fix the problem.
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It still takes Lynn a while to discover the ultimate source of the problem. It's not until he spots the narrow marks in the paint along the edge of the brake drums that he notes the rub marks on the inside of the wheels. The pressed center hubs of the wheels have four bent flanges that are welded to the outer rim to form the complete wheel assembly. These thick flanges are apparently contacting and distorting the brake drums. Lynn confirms this speculation with some measurements. The inside distance between the flanges is 12-3/8" and they extend about 1" below the plane of the wheel-drum mounting surface. The brake drums have an outside diameter of 12-1/2" and they extend to within about 3/4" of the plane of the wheel-drum mounting surface. Yup — there's about 1/8" difference in these diameters and the wheel hubs press down about onto the outer edges of the brake drums when the wheels are bolted on — the drum and the wheel need to deflect about 1/4" to relieve the interference. Now that is subtle!
Lynn now suspects that a recent owner of Penny has put a non-original set of rims on the car that almost, but not quite fit. Lynn also thinks that this is why the car was advertised as having its brake drums recently turned. The former owner was trying to solve the same brake drum distortion that Lynn's been chasing, but apparently failed to come to the correct conclusion.
Lynn takes out his handy 4" angle grinder and relieves the edges of the flanges, creating the small extra space needed to prevent contact with the drums. This small edge of the flange is after the weld with the outer rim of the wheel and serves no mechanical function; it will never be missed. (In fact it will lighten the heavy wheels slightly. It may also disturb the balance of the wheels.) He uses a little bit of silver spray paint to seal the bare metal.
What a difference that missing 1/8" of flange makes. With the ground-flange wheels the car stops straight, sure and smooth. The next day Lynn takes the car out and makes a number to trial stops with a couple of stops from 60 MPH, with no difficulty or effort. Lynn now has growing confidence that Penny has a solid set of brakes.
It is only some months later that Lynn discovers that the factory wheels for the 1938 Oldsmobile are 16" in diameter. The wheels currently on the car are 15" wheels. They're the wrong wheels!
A Switch For Improved Safety
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Lynn bypass the pressure brake light switch installed on the master cylinder (left)
with this mechanical brake switch (left center).
The switch is mounted on the firewall and under the brake pedal arm (center right, right).
With this modification the brake lights illuminate as soon as the brake pedal is depressed
allowing the driver to warn trailing (tailing) cars without actually braking.
With the pressure switch, considerable pressure must be applied to the brakes before the brake lights
are illuminated, dangerously delaying the signal to the cars behind.
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Lynn makes one additional improvement to the brakes. He purchases a mechanical brake light switch that he attaches to the firewall, bypassing the pressure switch that's on the master cylinder. With the pressure switch, one needs to give a pretty hard push on the brakes before the stop lights will be energized. Using a mechanical switch, an operator can gently press the pedal and illuminate the stop lights without actually applying hydraulic pressure to the brakes. Lynn feels this is a safety feature, allowing him to warn motorists behind him by easily displaying brake lights without actually slowing the car.
Lynn had successfully used a Standard SLS43 mechanical switch (from a mid-1950's Chevrolet truck) on Bugsby, replacing a switch that was connected by a spring to the hard lines of the mechanical brakes. There is also a Standard SLS40 switch (from an early 1950's Chevrolet truck) that is the mirror image of the SLS43. Where the left center photo above shows the arm of the SLS43 extending to the right, the arm on the SLS40 extends to the left — this difference might be useful for some installations. The SLS43 is also a little cheaper than the SLS40.
Was The Seller's Description Accurate?
Lynn feels that the seller clearly overstated the condition of the car's brakes. He claimed that the brakes on Penny "operate well and the car stops surely and straight," and that "the wheel cylinders were replaced in 2006, and the brake drums turned at that time." What did Lynn find?
- The car violently shutters and shakes when the brakes are applied. It does not stop surely and straight. The root cause of this poor brake performance is an incorrect set of wheel rims that press on and distort the brake drums.
- There is no emergency brake — the cables are completely missing.
- The rear brake drums are cut more than 0.160", almost three times the maximum 0.060" allowed. The rear brake drums are badly warped with a runout of about 0.060" (due to the thin metal from being cut too much, no doubt).
- There is one leaking wheel cylinder and the other wheel cylinders are heavily caked with dirt under the dust caps indicating that they had not been replace recently (certainly not in 2006).
- The original 1/4" front brake lines and hoses have been replaced with 3/16" lines and hoses. This reduction in cross sectional area of over 30% results in substantial reduction of pressure to the front brakes, shifting the balance between the front and rear brakes (further contributing to the warped rear drums, no doubt).
- The master cylinder is leaking.
- The rear brake linings are worn and in need of replacement.
- The bracket stablizing the rear brake hose connection to the brake line to the master cylinder is missing, increasing the chance for a brake line failure.
Lynn is certainly glad that he invested the time and expense to restore Penny's brakes. He is also disappointed that the seller was less than totally honest about this critical safety aspect of the vehicle.
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with your comments or questionsCopyright © 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Lynn Kissel
Last updated: May 24, 2009