Topic: General Brake Advice Please

[Rosinante]

The Brakes on my '78 K8.  Are dangerously ineffective.  I mean it.  Very poor.  Front brake only slows the bike down a bit.  I can't imagine how much pressure on the lever would be needed to lock up the front wheel.  Probably enough to break the lever.  Rear brake works better than the front, but still pathetic.  I know these brakes are now disappointing by today's standards but I have to believe they are not working as designed.  Back in the day, it seemed to me my '75 CB750K had "Hand of God" brakes.  Quite effective, for its time. 

I swapped out the front pads a few years ago but I do not recall rebuilding the caliper or MC.  Rear brakes very well may still have the original 45 year-old shoes.  What can I do to improve braking performance?  Here are a specific couple of questions:  Do you suppose the age of those rear shoes could have made them too hard?  Are there particular brands of brake shoes or pads that are known to be more effective for these bikes than others?

[Deltarider]

The Brakes on my '78 K8.  Are dangerously ineffective.  I mean it.  Very poor.  Front brake only slows the bike down a bit.  I can't imagine how much pressure on the lever would be needed to lock up the front wheel.  Probably enough to break the lever.  Rear brake works better than the front, but still pathetic.  I know these brakes are now disappointing by today's standards but I have to believe they are not working as designed.  Back in the day, it seemed to me my '75 CB750K had "Hand of God" brakes.  Quite effective, for its time. 

I swapped out the front pads a few years ago but I do not recall rebuilding the caliper or MC.  Rear brakes very well may still have the original 45 year-old shoes.  What can I do to improve braking performance?  Here are a specific couple of questions:  Do you suppose the age of those rear shoes could have made them too hard?  Are there particular brands of brake shoes or pads that are known to be more effective for these bikes than others?

As far as the front brake, is there any chance you've been spraying aerosols like WD-40 that may have hit the rotor? This can happen unnoticed and then a thorough cleaning is needed and maybe the pads will have to be replaced. My rear drumbrake shoes are still the first bike got when assembled. They brake as they should. I have made it a habit, whenever the rear wheel is of for a new tyre, to clean the drum's inside.

[BenelliSEI]

As mentioned, give the disc a really good deglazing and wash with brakekleen. I have a small stand that I use to mount a spare hub and axle to a large vice. Using a medium (somewhat worn out) disc on my 4.5” grinder , I can get the disc spinning and give it a really nice finish (see photo). You can be fairly aggressive, they are hard to damage.

Pads are by trial and error. Try block sanding yours, on a flat. If it’s even slightly moist/soft and comes off easily, it’s done. Some of the new (green) pads I’ve tried are even worse. Look on EBay for someone selling Honda old stock. I have some old EBC pads that work really well.

[WideAWAKE]

All those things mentioned above, in addition…

Make sure your caliper is clean and functions as it should.

Rear pads can be slotted to reduce glaze.

Something many don’t think about is old hydraulic brake lines, the rubber brakes down and swells instead of applying brake pressure. Put your fingers on your line and grab a handful of front brake, if it swells, you know where your braking pressure is goin. New lines, stainless is best.

[Rookster]

The rear brake is what it is.  It's a mechanical brake so the only thing you can do to it is pull the old shoes, scuff the drum with sandpaper and either refit the old shoes or fit new shoes.  You might want to measure the drum surface for wear.  I think 180mms is the max wear for the drum.  If it's past this then you may have to get a different hub.

I suspect the brake lines in the front are flexing which is absorbing some of your front braking power.  Replace with ss braided lines.  As the others have said scuff the disk and replace the pads.  You could also do a master cylinder and caliper rebuild. It wouldn't hurt.  If you have the original lines and have not been changing the brake fluid every 2 years, you also have water mixed with your brake fluid.  Dot 3 absorbs water from the air over time and once it's in the system it doesn't really ever come out. 

Scott

[MauiK3]

Old brake lines, old brake fluid, poor master cylinder, corroded caliper piston, any of these can contribute to the issue.
The piston in the caliper needs to be very clean and move easily prior to assembly. The rubber seal should be fresh.
Be sure all the little passages are open and flowing
It will work fine when it's put right.

[calj737]

Your rear brake should NOT be able to lock the rear wheel under heavy braking. This will cause a skid and you’ll likely end up eating asphalt. The front brake has nearly 80% of the available power to stop the bike. Fresh brake lines, fresh fluid, and proper rotor/pad surfaces and combinations will provide you ample safe braking.

[sevenfiveohhhh]

Maybe you need one of these for the rear. I'm not sure how it works or what exactly it does but it does stop on a dime. Anybody ever used a stop block like this?

[bryanj]

As to front brake i have NEVER known a standard single disc sohc be able to lock the wheel

[Kelly E]

Maybe you need one of these for the rear. I'm not sure how it works or what exactly it does but it does stop on a dime. Anybody ever used a stop block like this?

I've never seen one of those before, I'd like to know how it works.

[BenelliSEI]

Good point on the hoses. All my bikes have APEX hoses. They do make a difference. The K7 has a silver set, but recently Raymond has been making me black coated ones that I really like. Cheaper than NOS hoses and a noticeable improvement.

The master cylinder on my K4 was really rough and out of sheer laziness (mid riding season) I bought a cheap replacement master from Vintagecb750.com. My original cap replaced the plastic cap it came with and it works so well I’m just leaving it. If you decide to rebuild your original, order the pliers they sell for removing the first circlip. It makes an impossible removal MUCH easier!

[Kelly E]

Good point on the hoses. All my bikes have APEX hoses. They do make a difference. The K7 has a silver set, but recently Raymond has been making me black coated ones that I really like. Cheaper than NOS hoses and a noticeable improvement.

We're a little behind with 2/3rds of our bikes running Apex lines. We'll probably put the black lines on the 83' CB 1100F when we resurrect it.

[Kaze]

My take on this is that your brakes protect your life. I wouldn't trust the last owner of this bike with my life. (I knew him) I rebuilt the caliper and the master cylinder, and it's a damn good thing I did.

My master-cylinder rebuild kit as well as the rubber caliper piston seal came from VintageCB750. It was good from my point of view, but the stainless brake line made the brakes even better. Having said that OEM Honda lines are nice...just not the after-market rubber ones.

FWIW I don't recommend the stainless brake line kit from 4-into-1. It's was cheap, but it doesn't align with my fender's brake-line stay at all, despite the fact that I bought the kit for my bike's year. Also, the fittings were tough to get together, probably due to the rubbish chroming job on those bits. You get what ya pay for in this case.

[sevenfiveohhhh]

Maybe you need one of these for the rear. I'm not sure how it works or what exactly it does but it does stop on a dime. Anybody ever used a stop block like this?

I've never seen one of those before, I'd like to know how it works.

I really have no idea, its the only one I've ever seen. It is on a K3 I'm just starting to clean up, but it does stop well

[Kelly E]

Maybe you need one of these for the rear. I'm not sure how it works or what exactly it does but it does stop on a dime. Anybody ever used a stop block like this?

I've never seen one of those before, I'd like to know how it works.

I really have no idea, its the only one I've ever seen. It is on a K3 I'm just starting to clean up, but it does stop well

Well hurry up and take it apart, enquiring minds want to know.

[newday777]

Maybe you need one of these for the rear. I'm not sure how it works or what exactly it does but it does stop on a dime. Anybody ever used a stop block like this?

Nope never heard of it, until now.....

[newday777]

The Brakes on my '78 K8.  Are dangerously ineffective.  I mean it.  Very poor.  Front brake only slows the bike down a bit.  I can't imagine how much pressure on the lever would be needed to lock up the front wheel.  Probably enough to break the lever.  Rear brake works better than the front, but still pathetic.  I know these brakes are now disappointing by today's standards but I have to believe they are not working as designed.  Back in the day, it seemed to me my '75 CB750K had "Hand of God" brakes.  Quite effective, for its time. 

I swapped out the front pads a few years ago but I do not recall rebuilding the caliper or MC.  Rear brakes very well may still have the original 45 year-old shoes.  What can I do to improve braking performance?  Here are a specific couple of questions:  Do you suppose the age of those rear shoes could have made them too hard?  Are there particular brands of brake shoes or pads that are known to be more effective for these bikes than others?

Front...
My money is on an old hose being sacked and needs replacing.
The past couple years I've had the opportunity to ride a 90 year old friend's 74 Norton Commando to exercise it as he worked on it to sell, it's front brake disc was the same way until he believed me that the hose was bad. He put a new one on and the braking was so much better 😌. No more yikes!!!

Rear...
Open it up.
You might find the old shoes delaminated from the metal.(very common on the age of them)
Yes the drums wear too big so the adjuster is too far adjusted. Measure the drum.

[sevenfiveohhhh]

Yes, The lower front rubber hose was totally blocked on the k5 I just fixed up, evidently the liner was disintegrating inside or it just gummed up and stopped up from neglect. New hoses, cleaned caliper piston, new seal-  And the caliper arm was very stiff and almost impossible  to move on the mounting hinge pin. It took some work to get it apart, cleaned up an relubed and 2 new o-rings. It really needs to float freely.

[scottly]

Front brake only slows the bike down a bit.  I can't imagine how much pressure on the lever would be needed to lock up the front wheel.

Are you using the stock 14mm master cylinder?

[BenelliSEI]

Maybe you need one of these for the rear. I'm not sure how it works or what exactly it does but it does stop on a dime. Anybody ever used a stop block like this?

I've never seen one of those before, I'd like to know how it works.

I really have no idea, its the only one I've ever seen. It is on a K3 I'm just starting to clean up, but it does stop well

Well hurry up and take it apart, enquiring minds want to know.

+1 to that! Never seen one before. Does the bike have the original “steady arm” or does that replace it?

[jonda500]

Looks like the backing plate rotates under braking force which then adds more force to the brake actuation arm - but how does the plate return when the brake is released? And how is the plate made able to turn??
John

[sevenfiveohhhh]

Yes it has the brace up to the frame that keeps it from rotating. If you look closely- just below the axle nut, behind the brake rod you can barely see the stock brace mount. Looks like a different actuator arm though, with a tab that goes into the block, not sure what exactly it is supposed to do.  I will take it off and get it apart... more pictures when I get time to work-play with it!

[Deltarider]

Your rear brake should NOT be able to lock the rear wheel under heavy braking.[...]

But... all drum rear brakes are able to do that and it can be quite effective when riding straight on. It has saved me a couple of times. But NEVER try this if you're not straight up.
Here's an observation I will - no doubt - be ridiculed for. At the start of every season I perform a few tests. One of them is checking the front brake fluid lines. In spite they still have the Japanese factory workers fingerprints on it, they still do not swell under load. I dunno what I've done wrong. Bike has always been parked in the garage; maybe that's it.
Are there lines out there that will need less force? No doubt. But I now know what I have got and I am used to it. I am not aiming for a too light operation which could be dangerous in panick. To avoid these situations, a defensive way of riding is the best strategy.
As it is now, I can brake like a fool. Front disk sucks in the wet though, but, hey, gentlemen don't ride in rain.

[rotortiller]

The Brakes on my '78 K8.  Are dangerously ineffective.

That's the way they were built back then as they were the great experiment. They simply did not know much about motorcycle disc brakes back then. The K7 and 8 have a bigger piston in the caliper, it's possible someone may have fitted an earlier configuration. Rear brake shoes are still available and I can lock the back brake with substantial pedal effort at times, we all understand situationally there can be little weight and traction on the rear tire thus magnifying lock up. You can improve the front brake performance some using a master with a smaller piston, however make no mistake it is still a POS braking system by today's standards. If the brake works normally and releases normally there is nothing major to be gained with a rebuild for adding stopping power. The best the average guy can do with the single disc is buy good pads, add a better master and ride cautiously. The smaller master piston increases the maximum brake line pressure available to the rider. Changing out a good stock (serviceable) OEM brake line to a modern and stronger type offers a very tiny change in braking distance, but may firm up an already wooden hand lever .

[Rosinante]

Front brake only slows the bike down a bit.  I can't imagine how much pressure on the lever would be needed to lock up the front wheel.

Are you using the stock 14mm master cylinder?

The Brakes on my '78 K8.  Are dangerously ineffective.

....  The smaller master piston increases the maximum brake line pressure available to the rider. ...

Yes I think the MC is stock.  Yes, a smaller MC piston increases braking force, and it is good to hear they are available.  But for now, my plan is to rebuild the MC and caliper, replace the brake hose and see what happens.  If I need more braking force, then I will consider other options. 

As an aside, swelled hoses more often have the effect of holding pressure in calipers after the MC is released, causing brakes to drag.  In my experience.  But yeah, this brake hose should not still be on this bike. 

I am a little surprised no one has said "Yes, fresh shoes will have softer material compared to petrified 45 year-old shoes, and will likely brake better."

Many Sincere thanks to all.  You guys RAWK! 

One more thing:  I accept that these brakes, in perfect condition, do not perform like modern systems.  Of course.  This is true of the entire bike.  But they were designed and built WAY better than their competion at that time and are impressive today.  IMHO.  And I recall being impressed with their braking capability.  My bike's current braking would not impress anyone.  Not even in 1978.