Board index Flathead Power-Technical Questions, Answers, and Suggestions Pans Any hope for front brake?

Any hope for front brake?

Post Thu Oct 08, 2009 10:39 am

Posts: 5
On my 50 Pan I run a wide glide front end with the stock mechanical brake. I have NEVER had very good braking with the original equipment and my drum appeared to be warped. If I attempted to tighten up the shoes so that I MIGHT have better braking the wheel was free turning only about half of a revolution. Then it'd be bound up for the remain half of a revolution.
I tried turning the drum a few thousandth's and that seemed to help a little, but still didn't have very good braking and it still bound up about a quarter of the revolution.
SO, I bought a new drum and installed it. MUCH better and it doesn't appear to be out of round, BUT... I still don't have much braking ability even with a brand new set of shoes.
Can anyone tell me a reliable way to get the shoes arc'd to the drum? I saw in one of the other post's where someone suggested taking the shoes and drum to a local auto parts store and that they'd be able to arc them in a few minutes. Has anyone done this? Seems to me that they'd have to have the correct jig to set up your shoes in order to know where they're supposed to be riding inside the drum.
Just my ignorance showing up again...

Thanks, Jeff

Post Thu Oct 08, 2009 11:04 am

Posts: 1654
my take on the old mechanical front brake would be that

(1) it simply isn't big enough
(2) the position of the lever arm inside the backplate for styling reasons, means the lever arm angle is wrong ( greater than 90deg )
(3) the configuration of the brake cable, with its bent steel outer tube, is bad for transmitting the pull

so, it will never really be any good whatever you do
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Thu Oct 08, 2009 11:59 am

Yes, the shoes should be arced to the drum but you'll have to find a shop that does this, or one with a big lathe.
If you want to arc the linings yourself, and have access to a lathe, first mount the relined shoes on the backing plate. Place .015" shims between the pivot cam(s) and shoes, and turn on the lathe (300-350 rpm) to .010" under drum I.D. in .010" cuts.
You can also contour the shoes to the drum without a lathe. Remove the wheel then adjust the lever so both shoes are touching the drum a the same time. Do this by holding the lever hard against the drum. Remove the backing plate. Cut strips of coarse sandpaper (perhaps 100 grit-the coarser the paper the faster the sanding action) the exact width of the working surface of the drum. Using rubber cement (Gasket Cinch or similar product) glue them into the drum working surface so that there are no gaps. Reassembly the brake backing plate with the axle in place. With the wheel axle in a large bench vise apply the brake lever while moving the wheel back and forth so as to sand the brake shoes. Occasionally remove the backing plate, check the progress, and blow out the brake dust (asbestos may be in the old lining so be careful). You may have to replace the sand paper occasionally. The progress is easy to follow and when at least 90% of the shoes working surface show sanding marks, you are done. Remove the sand paper. Clean out the rubber cement with lacquer thinner.

Post Thu Oct 08, 2009 12:48 pm

Posts: 5
Exactly the method I was considering. Using Gasgacinch and fine grit sand paper on the drum.
You describe using a vise with the axle held in place and removing the backing plate from the forks. I was wondering if it wouldn't be easier, and more "True" if you were to do basically the same with the backing plate in place on the forks, and simply having the bike on a jack off of the ground so you can spin the wheel. It's easy enough to remove the axle and pull the wheel off to check the progress of the sanding.
Also this way I don't mar the chrome on the axle with the vise.
I appreciate the advice, and in my mind consensus that the idea of gluing sandpaper to the drum wasn't "out there".

I have to agree with you too. You can spit shine a turd, but when you get done all ya got is a shiny piece of shit. Nothing I do is ever going to make this thing work like disc brakes.
The brake drums on the old pan both appear to be about the same diameter and I never have any problems locking up the rear brake. The rear shoes and drum are wider than the front shoes and drum so there's more friction to do the stopping with plus my right leg is DEFINITELY stronger than what I can grip with my hand.
I do understand that the physics of the front brake and rear brake are different and that the LAST thing I want to do is ever lock up the front brake, but...
I recently had an experience I'm trying to never have again. NOT being able to stop at a stop light because my back brake failed due some material malfunction. Basically when I hit the rear brake the "cam" that moves the shoes against the drum BROKE right inside the backing plate. It not only broke off of the shaft, it broke into two pieces.
One of the pieces lodged between the backing plate and the shoe causing my brake to be LOCKED even though I immediately let off of the brake lever when I heard the loud POP when it broke and I started going sideways.
As I was sliding through the intersection, applying what front brake I have in order to hopefully manage to miss the car on my right that was insisting that HE had the right of way because I WAS running a RED light.
I popped the clutch and forced the rear wheel to turn, stopping my skidding about half sideways for the moment. The guy insisting on the right of way evidently figured out that I wasn't just "running the light" but that I was experiencing a life changing moment and stopped so I could manage to point the bike in the direction of a drive way that led onto a hard dirt field.
I motored across the short field and onto some blacktop behind a local pub. When I got off the bike and inspected things the brake lever that normally hangs almost straight down had been spun towards the rear of the bike when the backing plate had spun in the frame.
It appears that when I popped the clutch to get myself out of a locked brake situation it almost ripped off the tab on the backing plate that keeps it from spinning in the frame when you hit the brakes.
I have AAA towing for all my vehicles, including 100 miles for the Harley. They came out and picked me and the pan up and took us home.
I immediately took things apart and that's when I found out what had happened.
This backing plate was only 3 months old. I had replaced my old OEM part with a new CHROME one. The vendor replaced the defective backing plate with another unit at no cost to me. I have yet to install it though. My original unit isn't chrome, but it HAS held together for at least the 31 years I've owned the bike.
So... THAT'S why I'm trying to get a front brake that is something more than a piece of equipment that will hold me from rolling backwards on a hill while stopped at a stop light. I run a foot clutch with a jockey shift and it can get REAL dicey trying to keep your right foot on the one good brake while you put your left foot on the clutch...
Gravity's a law, not an option.

Thanks again guys for putting up with me and my questions and for your input.


Post Thu Oct 08, 2009 3:02 pm

1st: those aren't my comments - "borrowed" from a helpful person on BritBike, and from Vintage Brake.
If your lever does not pass through 90° to the cable during action (and nothing is wrong) I suggest cutting the arm free of the cam and "clocking" it so that (example only) if the range of rotation is 60°, it begins at 60° (acute angle), passes through 90° and ends at 120° (obtuse angle) for the highest average mechanical advantage.
The absolute highest (strongest force against the drum) ends with the shoes locked and the lever at 90°, but this means higher hand effort during mild stops.
More on how this works:

Post Thu Oct 08, 2009 5:03 pm

Posts: 1654
I did see a conversion in a book called 'Chopper Cookbook' which involved fitting a springer-type back-plate to a Hydra-Glide front fork, for cosmetic reasons. However it does occur to me, that if you did this ( and it didn't look difficult ), you could fit one of Kurt's 2LS front brake plates, at which point you would have as much braking effort as you are going to get from one of those old drums.

good luck with the suicide clutch. I had a bike fitted with one of those once, but it had a single front disc ( banana caliper type ) which helped a lot. I the end I put the rocker pedal back on.
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Fri Oct 09, 2009 6:36 am

Posts: 309
Location: Ohio
You didn’t say whether you are using after market shoes or had just relined an OEM set. If you are using aftermarket shoes then arcing them on a lathe is your only choose to have them working concentric with the C/L of the drum in my opinion. I have not seen a single set of aftermarket shoes within 1/8” of running true to the drum. That equates to a lot of lost surface contact between the drum and shoes.

The machine that auto parts stores use will not arc the after market brake shoes true to the drum. They will only arc them true to what ever they are to begin with. Its only a fifteen minute job in a lathe and does make a big difference in stopping power. Yet keep in mind that nothing you do with this designed system will allow you to lock up the front tire.


Post Fri Oct 23, 2009 8:23 pm

Posts: 767
Location: Pa. , USA
Try Vintage Brake @ http://WWW.VINTAGEBRAKE.COM , they did a good job on my 45" brakes "I know much lighter" but was pretty impressed with the improvement over stock, I'm currently building a '65 and will have them do the brakes. Tim
Vintage roadracing, Class C, AHRMA # 335

Post Sat Oct 24, 2009 2:16 am

Posts: 1654
front brakes on 45s are like the squish clearances and quite a few other things, set up to very large tolerances so they always fit together, regardless of the manufacturing accuracy of the original parts.

there is a fair amount of scope for improvement by proper assembly, and on the lighter, slower bike you notice it more. But, the speed-and-weight arithmetic on a panhead is different, plus the 'glide front brake has additional weaknesses - the internal lever arm with its inherently-weak geometry in particular, the bent cable guide tube - so the springer type brake is inherently better than the 'glide one, if not by much at times
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Sat Oct 24, 2009 8:00 am

Sorry, interesting idea but not practical.

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