6in Drum Brake "Drag"

[Chris Taylor]

Hello all, seeking some information regarding a problem I'm having with my Drum Brake.
Rupp Grand A with a 6in Bendix Brake.  It drags terribly, to the point I have to use two hands to turn the wheel at certain spots.  I first thought my axle may be bent but it is straight.  When I take the Drum off, the axle spins freely so I know it's not bearing related.  The shoes are not new, roughly half worn.
Any thoughts, suggestions, etc. would be greatly appreciated.

[ted johnson]

How about when you leave the drum installed, but take out the pin that connects the brake rod clevis to the actuating arm? Also, make sure the shoe tips sit firmly against the actuating cam and the shoe pivot. If the drum spins freely with the clevis pin out, your clevis is adjusted too tightly. Also, remember that the actuating arm pivot rod is serrated, and the actuating arm can be moved on the serrations so that the rod is not tight. There's usually a little drag due to the drum and/or the drum hub not being concentric. A tiny bit of "noise won't hurt. If the drum still drags when the rod is disconnected, you may just have to find a new set of shoes on eBay. I have had no Bendix issues besides fade at the end of a few laps. I finally switched the Bendix for a Wilwood kart caliper with MCP master cylinder, disc and hub. Easy swap. Ted

[Chuck Lipka]

If it's a used system as most of them are, the combination of wear in all the pivot points....
activator arm to pedal rod, splined shaft thru the backing plate, eccentric (on the end of
the splined shaft), added together will require adjustments in order to have a short enough
pedal throw, that the shoes will now drag.   Every one of the karts I've been thru had the same issues.

Try your local NAPA store for some white colored brake lube.   Door latch lubricant will work too.
A touch of it on the splined shaft eccentric/shoe contact point, as well as where the shoes contact the backing plate should help.  White lithium grease is your LAST choice.  Breaks down under heat and
will contaminate the brake shoe friction surface.   The return springs might be weak and not returning
the shoes to their "at rest" position.   Replace the springs.

DON'T GET CRAZY WITH THE LUBE....YOU DON'T WANT IT TO CONTAMINATE THE SHOES!!!!!

If there's a bunch of wear in the backing plate hole and the splined shaft, you may have to either
put a bronze bushing in the backing plate for the shaft, OR replace all of it with replacement
pieces.......this forum, ebay, etc.  

The other thing I did was to take 24 or 36 grit sanding/grinding surfaces to take down the high
spots on my brake shoes.  Take just enough so the drum has just a touch of drag against the shoes.

Chuck

[David Luciani]

removing drag from bendix drums is a woman.
it takes me hours to get one drag free and often it'll gradually drift back to being a problem.
new or used theres alot of variables.
first you should have already replaced the springs if you didn't buy new that helps alot.

things to look for

warped or out of round drum this is pretty common
bent axle is #2 suspect
bent or mis aligned backing plate
check for miss aligned front cover the one that bolts onto the drum.
 actually you should check that first especially if you have a wedge style drum lock.
often the wedge will mis-align the drum or it installs at slight angle.
 best solution is replace outer cover with a newer clamp style lock.
 i prefer to use one with very little material attaching it to keep brake cool.
i use this one #(433692) or this one # (400245) 
link for hubs

check for the shoes to be rubbing the inside of the drum this is a very common drag issue.
check shoes for high spots not common but can happen. 

another issue which is pretty common is for the mounting areas to be bent slightly.
i had spent hours assembling and reassembling the drum on my gk800 before i realized it was a frame tab issue.
actually i think it took several weeks because after a few hours i'd just walk away. 
if you are good mechanically with care you can get them to turn free as if there wasn't anything on the axle. 
but it takes alot of work. good luck and keep us posted on what you try and what results you get.
hope this helps

[Chris Taylor]

Thanks for all the information guys.  I had good luck this weekend with the brake.
Basically I disassembled everything. Inspected the drum to make sure it wasn't warped, it wasn't.  Checked the shoes for high spots, I've determined I do need new shoes.  The springs seem strong but I'll probably replace if I can find them.  I did notice the backing plate was slightly bent so I straightened in the vise.  I also noticed a lot of wear on the actuating cam but the shoes still seem to sit firmly, I may try to find a new one.  I rotated the backing plate when I reinstalled on the frame, switched the shoes from one side to the other, and reinstalled the drum.  It now spins freely with no drag at all!  Not sure exactly what fixed the issue but it seems to be fixed.
Dave, I really like your idea regarding replacing the "wedge lock" cover with a clamp style.  The wedges are a pain.
If anybody has a set of shoes and springs they are willing to part with, please let me know. 
Thanks again for the information.
Chris

[ted johnson]

Comet Kart Sales has their own proprietary clamp style hub. Best I've used. I had one on a Terry Ives machined drum on the Bendix on my n1ke. It ran very true. There's a Terry Ives style machined drum on ebay right now. Tom Smith has it advertised. Item 223287455329. Here's a pic with the Ives drum and the Comet Kart Sales hub. Sorry for the bad pic quality. Ted

[Chris Taylor]

Thanks for the information Ted, I'll check it out.

[ted johnson]

Not cheap, but permanent! Nice workmanship. TJ

[Tom Smith]

      It helps to fix the cam pivot too.

[ted johnson]

Wow! neat job. I reinforced mine, but it wasn't that pretty! TJ