[iamdamoj]

Hi, I have a ‘79 CX500C with the reverse com star wheel. It’s covered less than 25k miles but the internal dimensions of the drum are at about 158mm not far short of the 161mm service limit.

I’m only checking this as my brake performance is absolutely horrendous bordering on non-existent after trying I’ve read. Last I replaced the shoes and after running them in I sanded them to fit the shape of the drum and bedded them with little to no effect.

Does anyone know the specs of the drum as new so I can check I’m getting as good as possible when purchasing a replacement wheel?
Any help would be most appreciated

 

[CXPHREAK]

I would assume the lip to be the original diameter.

 

[Randall-in-Mpls]

Per page 14-1 in the Factory Service Manual, the standard dimension of the brake drum ID is 160mm. Your drum is fine.

 

[iamdamoj]

Per page 14-1 in the Factory Service Manual, the standard dimension of the brake drum ID is 160mm. Your drum is fine.

Yeah the screenshot I attached is 14-1. My thought was the closer it got to the limit of 161mm maybe the worse the performance may become? I’m trying to find out how much I’ve lost from original in an attempt to gauge how much it’s been used.

 

[Randall-in-Mpls]

You've got more material than the standard. Probably within the margin of error for new machining. Very little wear.
I'd be looking at insufficient lube on the moving parts of the brake plate or misadjustment.

 

[D-Fresh]

If not turning the drums i always take some sandpaper and try to scuff up the surface to help the shoes bed in. Drum brakes are very sensitive to proper adjustment also.

 

[The lost Dane]

Hi
Is the geometry of the brake rod and the brake cam right
That make a big difference
when you apply the brake the angle can't go past 90 deg
if it does the brake lever in the cam need to be relocated
TLD 🇨🇦 🇩🇰

 

[Sidecar Bob]

I was thinking the same as TLD. I've done a bit of experimenting with stuff like that over the decades and if the geometry isn't at least close to what the engineers intended it won't have the leverage to press the shoes against the drum firmly enough to work.

FWIW, I understand why it is normal to use the front brake more than the rear but things are a bit different on a sidecar in the winter; When the roads are dry I use the front brake normally but it is too easy to lock up the front brake when there is snow on the road and when that happens the steering snaps to the left (right side sidecar) and the outfit moves toward oncoming traffic so this time of year I rely on the rear to stop.
If both arms (brake plate and brake pedal shaft) are close to right angles to the rod I can easily stop the sidecar outfit (total weight about 900 Lb including driver) with the rear brake alone.

 

[The lost Dane]

Hi
Here is a picture of the rear brake cam and lever configuration
The angle can't be greater then 90 deg
if it is greater then 90 deg the leaver is in the wrong spot on the brake cam
move it to align with the dot's on the lever and cam

TLD 🇨🇦 🇩🇰

 

[Sidecar Bob]

What he said^^^^^^^
And the same goes for the lever at the other end of the rod except it has to be set by a similar dot on the end of the shaft where the brake pedal attaches (this information is in the FSM).