Topic: Rear Brake Drum Placement

[Ellz10]

1977 Honda CB750 K

So I had to fab up my own rear brake strap due to going with a bigger tire. However the issue I'm running into, or rather the question I have is whether or not the placement of the rear drum has to be in an exact spot?

Obviously with the rear axle nut loose, I can spin the whole thing around and around, but once I tighten the nut the whole thing stops moving. In regards to the brake arm (the dots match up) and whole assembly, does it matter where it's placed?

[denward17]

Good question, and I don't really know for sure.

But seems to me if the brake arm is connected it doesn't matter where it is.  Just needs to be long enough for wheel movement fore and aft for chain adjustment.

[Lucien Harpress]

Nope, doesn't really matter.  It sort of rotates around a little bit every time the rear swingarm moves, so exact placement isnt super-critical.  Just don't point it straight forward so it's got no way to move and you'll be fine.

[Ellz10]

Awesome, thanks so much y'all! Appreciate it!

[BenelliSEI]

Careful..... from a physical “pull” perspective, the brake lever (on the hub) should be in the “7 o’clock” position, and not be pulled past the “6 o’clock” position when full on. Any further than that and the force is being used to pull DOWN and not ROTATE the crank.

[Ellz10]

Careful..... from a physical “pull” perspective, the brake lever (on the hub) should be in the “7 o’clock” position, and not be pulled past the “6 o’clock” position when full on. Any further than that and the force is being used to pull DOWN and not ROTATE the crank.

I'm at work right now, but when I get home I'll drop it down and see where it sits. I think I'll be needing to rotate the brake arm off it's matching dot point. No harm there I don't believe though. I'll update this a bit later.

[Don R]

  What he ^ said and don't forget the brake pull rod also has to reach and make its travel.
  Remember, that strut holds your life in its hands, I've got a 750 with a 16" X 5" wide M&H slick and a slightly bent stock brake strut. 

[Ellz10]

  What he ^ said and don't forget the brake pull rod also has to reach and make its travel.
  Remember, that strut holds your life in its hands, I've got a 750 with a 16" X 5" wide M&H slick and a slightly bent stock brake strut.

When you say "brake pull rod", you're referring to the rod that attaches to the brake arm, correct?

[Ellz10]

  What he ^ said and don't forget the brake pull rod also has to reach and make its travel.
  Remember, that strut holds your life in its hands, I've got a 750 with a 16" X 5" wide M&H slick and a slightly bent stock brake strut.

5" wide RIM??

[ekpent]

 Make sure wherever the brake strap ends up lining up be sure to use the bolt that has the hole in it for adding a safety cotter or other pin to keep the nut from spinning off. Make sure that clears the tire also. Bad news if the strap comes unfastened. Wish I had a bike here but it seems at either one end of that strap or both the nut is never clamped super tight because the bolt has a shoulder on it to allow a little play.

[Ellz10]

Make sure wherever the brake strap ends up lining up be sure to use the bolt that has the hole in it for adding a safety cotter or other pin to keep the nut from spinning off. Make sure that clears the tire also. Bad news if the strap comes unfastened. Wish I had a bike here but it seems at either one end of that strap or both the nut is never clamped super tight because the bolt has a shoulder on it to allow a little play.

Absolutely! Both bolts on either end have cotter pins that go in! I made sure to fab up a strap that would clear the tire.

I've never heard or read anywhere that the nut shouldn't be screwed on tight? Can you elaborate on that for me so I can understand please!

[ekpent]

The swing arm has to be able to move freely. Hopefully somebody that has been down in that area lately can give more insight or I may be completely wrong  Bad part about not having my bikes handy at home.

[RAFster122s]

Screwed on tight it will want to capture the steel arm rather than allow it to pivot as designed. It needs to be able to rotate to function.

[Ellz10]

Screwed on tight it will want to capture the steel arm rather than allow it to pivot as designed. It needs to be able to rotate to function.

The swing arm has to be able to move freely. Hopefully somebody that has been down in that area lately can give more insight or I may be completely wrong  Bad part about not having my bikes handy at home.

So it's alright to leave the nut barely snug/loose on both sides, just so long as I remember to put the cotter pin in there? Is that about right?

[Lucien Harpress]

As I remember, that bolt really should have a shoulder on it that's just barely wider than the arm and hub.  This lets you tighten the nut tight to the bolt, not to the arm.  This allows the free pivot of the arm, while also letting the nut get tight enough to it doesn't spin off.

Even with the cotter pin I'd be very wary of not getting that nut fully secure.

[Ellz10]

As I remember, that bolt really should have a shoulder on it that's just barely wider than the arm and hub.  This lets you tighten the nut tight to the bolt, not to the arm.  This allows the free pivot of the arm, while also letting the nut get tight enough to it doesn't spin off.

Even with the cotter pin I'd be very wary of not getting that nut fully secure.

Here's the lineup. On the left is for the hub and on the right is for where it bolts up to the swingarm

[Ellz10]

Well I did it folks! Got her all dialed in and we've got  braking power. My mistake was not having the rear hub steady when I was spinning the tire and applying the brake.

Going to center some holes to be drilled out of the center of the brake strap I made to reduce a little weight. I'll probably just remake the whole thing in aluminum instead. At least now I know it works as intended.

Many thanks to you all!

[grcamna2]

As I remember, that bolt really should have a shoulder on it that's just barely wider than the arm and hub.  This lets you tighten the nut tight to the bolt, not to the arm.  This allows the free pivot of the arm, while also letting the nut get tight enough to it doesn't spin off.

Even with the cotter pin I'd be very wary of not getting that nut fully secure.

+1

[bryanj]

In UK the bike should fail MOT(annual inspection) if the angle between pull rod and operating arm exceeds 90 degrees

[RAFster122s]

Which bolt are you asking about? I'm confused as some answers seem to be about the swing arm, others the axle bolt, and yet others about the brake backing plate rod/arm.

[newday777]

You've made your brake stay too short.
Too much angle of the hub stay mount.
Your picture is 1st.

[Ellz10]

In UK the bike should fail MOT(annual inspection) if the angle between pull rod and operating arm exceeds 90 degrees

Interesting.

So if you're looking at the picture I posted with my last reply last night, are you saying the brake arm should be pointing more to the right (towards the front) or left (towards the back)?

[Ellz10]

Which bolt are you asking about? I'm confused as some answers seem to be about the swing arm, others the axle bolt, and yet others about the brake backing plate rod/arm.

I'm not asking about any bolts really lol. I just was showing a pic of the 2 bolts that that Lucien guy was talking about, that's all.

[Ellz10]

You've made your brake stay too short.
Too much angle of the hub stay mount.
Your picture is 1st.

Okayy... so then what is the correct angle?

I keep getting different answers from different people and have to switch up the brake stay. With the bike sitting on the lift without the tire hanging down, the brake arm is at a 6:30 position. Very close to the 7 o'clock position BenelliSEI had warned of.

So I suppose I'm lost as to the correct place for everything there doesn't seem to be a concrete explanation.

[BenelliSEI]

Looking at your last lift picture, I think you are OK on our angles.

[Old Scrambler]

Of the 100+ rear-drum Hondas that have passed through my hands...........All of them have the brake-stay located at approximately 5-O'clock. The shouldered fastener should pass through the stay-arm somewhat loosely. The washer and castle-nut should be mildly tight against the shoulder and adjusted to allow for the cotter-pin.

[newday777]

You've made your brake stay too short.
Too much angle of the hub stay mount.
Your picture is 1st.

Okayy... so then what is the correct angle?

I keep getting different answers from different people and have to switch up the brake stay. With the bike sitting on the lift without the tire hanging down, the brake arm is at a 6:30 position. Very close to the 7 o'clock position BenelliSEI had warned of.

So I suppose I'm lost as to the correct place for everything there doesn't seem to be a concrete explanation.

You are starting with the wrong reference mentioning the brake actuator angle. I'm not referring to that.

I went to my shop to look at the 78K on my lift and see some difference in my earlier post from the K2-K6 pictures above.

1st, Is the bolt holes on your remade brake stay 12 5/8" center to center? That is the stock 77/78K brake stay length.
If not, which is why I said that your brake housing plate looks like it sets forward too far comparing your picture to other bikes(my pictures were earlier K models above and have a different stay length... so will have different brake stay plate angle compared to your bike)
I've taken pictures of the K8 on my lift to compare to yours, which looks like your brake stay bolt sets forward from the stock location, which you will get if the holes on your new stay are shorter than 12 5/8" center to center. It looks like both your bike and the bike on my life axles are at #16 alignment tics so it's not the chain wear difference.

The brake actuator arm needs to be set on the splines at the punch marks lined up to let you know if you brake shoes are too thin needing replacement (reference pictures from Hondaman's book) and will determine the angle as chain wears and brake shoes wear. Do you have new shoes on your bike??

[newday777]

BTW you are correct that there isn't much mentioned on rear brake plate angle positions in most service manuals. I have the Honda, Clymer, Chilton and Mark's My CB750  book for reference, thus the multiple answers you received.
I checked them this time after I got to the shop.

[Ellz10]

Looking at your last lift picture, I think you are OK on our angles.

I did some more research and I came to the same conclusion. I looked at several of the stock photos of the 77/78s and it's barely noticeably off.

Thank you for the clock reference/example, I'll be sure to remember that!

Of the 100+ rear-drum Hondas that have passed through my hands...........All of them have the brake-stay located at approximately 5-O'clock. The shouldered fastener should pass through the stay-arm somewhat loosely. The washer and castle-nut should be mildly tight against the shoulder and adjusted to allow for the cotter-pin.

That's great news, because that's about where mine is at once I set the bike down and threw the back gate up!

I'll make sure to check the tightness of the bolts and definitely make sure not to tighten hard. Thank you (:

You've made your brake stay too short.
Too much angle of the hub stay mount.
Your picture is 1st.

Okayy... so then what is the correct angle?

I keep getting different answers from different people and have to switch up the brake stay. With the bike sitting on the lift without the tire hanging down, the brake arm is at a 6:30 position. Very close to the 7 o'clock position BenelliSEI had warned of.

So I suppose I'm lost as to the correct place for everything there doesn't seem to be a concrete explanation.

You are starting with the wrong reference mentioning the brake actuator angle. I'm not referring to that.

I went to my shop to look at the 78K on my lift and see some difference in my earlier post from the K2-K6 pictures above.

1st, Is the bolt holes on your remade brake stay 12 5/8" center to center? That is the stock 77/78K brake stay length.
If not, which is why I said that your brake housing plate looks like it sets forward too far comparing your picture to other bikes(my pictures were earlier K models above and have a different stay length... so will have different brake stay plate angle compared to your bike)
I've taken pictures of the K8 on my lift to compare to yours, which looks like your brake stay bolt sets forward from the stock location, which you will get if the holes on your new stay are shorter than 12 5/8" center to center. It looks like both your bike and the bike on my life axles are at #16 alignment tics so it's not the chain wear difference.

The brake actuator arm needs to be set on the splines at the punch marks lined up to let you know if you brake shoes are too thin needing replacement (reference pictures from Hondaman's book) and will determine the angle as chain wears and brake shoes wear. Do you have new shoes on your bike??

So I measured from center hole to center hole and I'm at 12 1/2, maybe a tad closer to 12 3/8, so a bit off from stock length.

My punch marks are dead set lined up with eachother - I tried moving it around, but in the end having them match dot to dot is the only way that I could make it work.

Brand new EBC shoes, yepper!