Shep
Shep of the Dessert
The rear brake arm is in nearly the perfect position for when the brake is 'on' and the shoes are in full contact with the drum, from the looks of its position now it can only get worse the more the lever moves forward.
Do Airheads have brakes?
- Thread starter fatbaldbob
- Start date
Myke Rocks
Registered user
It gets worse!
The idiot who "designed" the rearsets did not allow for the effect of suspension travel.
As the rear suspension moves up and down, the rear brake pedal (which is too short, incidentally) will move up and down with it. The footbrake pivot of most rod braked systems are on the same pivot centre as the swinging arm to avoid such a disaster.
Myke
The idiot who "designed" the rearsets did not allow for the effect of suspension travel.
As the rear suspension moves up and down, the rear brake pedal (which is too short, incidentally) will move up and down with it. The footbrake pivot of most rod braked systems are on the same pivot centre as the swinging arm to avoid such a disaster.
Myke
Myke;
Don't be sorry for pricking bubbles, I knew it was not right the first time I rode it, I would not ask the question if I didn't want to hear the answer, so all advice is gratefully received. As you correctly stated whoever made the set up has taken no account for the suspension and you can feel it pushing against the pedal as the swing arm moves.
You suggestion of moving the pivot further down the arm is a simple adjustment I can make so will give it a go and see if it improves.
I think I will try and put it back to a standard set up, it was a cafe racer but it now has renthal straight bars on it which I prefere, so rear sets are not really practical.
Anyone know where I can get a standard set of pegs, gear and brake controls for a 1978 R80/7, anyone on here got a set they want to sell?
Don't be sorry for pricking bubbles, I knew it was not right the first time I rode it, I would not ask the question if I didn't want to hear the answer, so all advice is gratefully received. As you correctly stated whoever made the set up has taken no account for the suspension and you can feel it pushing against the pedal as the swing arm moves.
You suggestion of moving the pivot further down the arm is a simple adjustment I can make so will give it a go and see if it improves.
I think I will try and put it back to a standard set up, it was a cafe racer but it now has renthal straight bars on it which I prefere, so rear sets are not really practical.
Anyone know where I can get a standard set of pegs, gear and brake controls for a 1978 R80/7, anyone on here got a set they want to sell?
It works!!!
Myke,
Just done as you suggested, the lever arm was 80mm long, drilled a new hole and moved the brake rod pivot down 25mm, what a difference, still not brilliant but a huge improvement it's almost acceptable now
Thanks for the tip
Myke,
Just done as you suggested, the lever arm was 80mm long, drilled a new hole and moved the brake rod pivot down 25mm, what a difference, still not brilliant but a huge improvement it's almost acceptable now
Thanks for the tipBendy toy
Registered user
My similar vintage Suzuki GT750 has the 1/4" thick solid stainless discs with funny round organic brake pads. I'm sure sintered pads would help but they don't seem to exist for those calipers.
If the brake feels wooden (mine does) try a smaller diameter master cylinder. Better hydraulic ratio puts more pressure on the disc.
Sent from my iPhone using Tapatalk
If the brake feels wooden (mine does) try a smaller diameter master cylinder. Better hydraulic ratio puts more pressure on the disc.
Sent from my iPhone using Tapatalk
Spot on Myke.. Didn't see the pics till today, and Mykes hit it fair and square
Front brake can work, almost
BUT they do need setting up right on the eccentric shaft.
Front brake can work, almost
BUT they do need setting up right on the eccentric shaft.Beemerboff
Registered user
Agreed- there is nothing to add to Myke's posts - which is a rarity on any forum.
Except that I have the brake cam from a 3 stud mono on my bench and it is not symmetrical and only works one way , and I seem to recollect a rather pricey kit to convert the cable operated paralever brake to top operation, which included a revised cam, so there must be a change over point from the old symmetrical cam.
the trick to getting the cable operated M.C.front ATE'S working is by optimising the angles similarly to Myke's suggestions for the rear, and making certain that everything is well lubed and is moving really freely.
The eccentric pin which the slave cylinder pivots on is the most important - if this is pivoting correctly there is no need for the chalk and string line method of lining up the wheel cylinder, just get it close and a decent application of the brake should line it up.
And if it doesn't the brake will never work properly, no matter how close you get it by using any other method to align it.
They are not a bad brake, it is just that BMW never got the master/ slave cylinder ratio correct - they fitted a 13mm MC with one disk when a 11mm is just OK with two disks, still wooden and heavy with minimal lever movement and no feel , but at least a little more power if you squeeze it hard enough.
Except that I have the brake cam from a 3 stud mono on my bench and it is not symmetrical and only works one way , and I seem to recollect a rather pricey kit to convert the cable operated paralever brake to top operation, which included a revised cam, so there must be a change over point from the old symmetrical cam.
the trick to getting the cable operated M.C.front ATE'S working is by optimising the angles similarly to Myke's suggestions for the rear, and making certain that everything is well lubed and is moving really freely.
The eccentric pin which the slave cylinder pivots on is the most important - if this is pivoting correctly there is no need for the chalk and string line method of lining up the wheel cylinder, just get it close and a decent application of the brake should line it up.
And if it doesn't the brake will never work properly, no matter how close you get it by using any other method to align it.
They are not a bad brake, it is just that BMW never got the master/ slave cylinder ratio correct - they fitted a 13mm MC with one disk when a 11mm is just OK with two disks, still wooden and heavy with minimal lever movement and no feel , but at least a little more power if you squeeze it hard enough.
I've got something to add, that I discovered when switching from cast to wirespoke wheels on my 79 R80/7.
It's possible that the wirespoke hubs are the type that demand a narrower shoe than other hubs that can be used / interchanged on this model or other wirespoke hubs that don't fit it. I had to switch to the narrower hub/shoes when I changed to wirespokes, and they changed rear brake performance from quite good to nearly non-existent. Exactly as the man at Motorworks had predicted when I picked their brains about it.
You can probably figure out if you've got the narrow hub by looking at the Motorworks website - can't remember exact measurements etc off top of head. Point is, you'll probably never get an acceptable rear brake with that hub.
I upgraded to bar mounted m/c at front, and renewed and re-set-up everything in the front brake set up. I was surprised at how good the twin discs can be. More than acceptable power.
In days of old it was common to have suspension movement feed back into the rear brake pedal, it was something you just got used to. If you can't, fit a cable operating system.
With a handlebar master cylinder fitted and the forks set up properly I actually prefer the ate front end to the brembo setup. The big advantage with the brembo front end is there's no messing about and it is consistent.
If you look at the back of the ate disc and it has a groove worn near where it fits to the hub you will never get it to work properly. The disc needs to be very flat.
If you look at the back of the ate disc and it has a groove worn near where it fits to the hub you will never get it to work properly. The disc needs to be very flat.
Simular brake issue-help
I am in a similar position to fatbaldbob. Last weekend I bought a 1975 R90s in original but good mechanical condition and on my first ride out today the twin front discs seem to have only a minimal effect on stopping the bike and in fact it is the rear drum that is much more effective. The feel I seem to get through the lever is that of no grip, almost skating or a metal to metal feel. The pads have lots of depth but I am unsure about the thickness or surface of the discs and also the lever is not at all spongey.
Thoughts anyone?
Byron
I am in a similar position to fatbaldbob. Last weekend I bought a 1975 R90s in original but good mechanical condition and on my first ride out today the twin front discs seem to have only a minimal effect on stopping the bike and in fact it is the rear drum that is much more effective. The feel I seem to get through the lever is that of no grip, almost skating or a metal to metal feel. The pads have lots of depth but I am unsure about the thickness or surface of the discs and also the lever is not at all spongey.
Thoughts anyone?
Byron
Beemerboff
Registered user
Perhaps the PO wasnt a big user or brakes, and the pads are simply glazed. Or they could have been contaminated and never really recovered .
You could try scrubbing the disks with a SS scouring pad followed by heavy brake use, do it a couple a couple of times - if you notice any improvement then new pads will probably make it even better.
Like Rob said, scored disks wont work, and all the pivot points on the cable and MC must be well lubed and free.
ATE calipers pivot on a pin, and the pin also rotates to keep the pads aligned with the disks, so if that pin is not good and loose nothing much happens.
Your bike will almost certainly be on its second master cylinder by now, and the PO might have fitted the wrong size replacement.
11mm work best but are had to find , but 12 mm are easy to get and will make a big difference if your existing is a 14 or 15mm - the size is on the cylinder.
Forget about tales of long travel and spongy lever - it just doesnt happen unless you are doing something else wrong.
You could try scrubbing the disks with a SS scouring pad followed by heavy brake use, do it a couple a couple of times - if you notice any improvement then new pads will probably make it even better.
Like Rob said, scored disks wont work, and all the pivot points on the cable and MC must be well lubed and free.
ATE calipers pivot on a pin, and the pin also rotates to keep the pads aligned with the disks, so if that pin is not good and loose nothing much happens.
Your bike will almost certainly be on its second master cylinder by now, and the PO might have fitted the wrong size replacement.
11mm work best but are had to find , but 12 mm are easy to get and will make a big difference if your existing is a 14 or 15mm - the size is on the cylinder.
Forget about tales of long travel and spongy lever - it just doesnt happen unless you are doing something else wrong.
steve in nz
Registered user
the do if you hold your arms out horizontal and your hands vertical and cup them
...
Most ATE probs can be sorted with a smaller MC
Seeing as the builder of the cafe racer made such a cock up on the rear brakes i expect he didn't have a clue how to set up the bmw front ATE brakes.
There is a cam that holds the caliper to the slider. This cam needs to be rotated on each caliper so the inside pad is just skimming the disc.
Undo the cam cover underneth the caliper (17mm or 19mm hex head) put your finger up inside (or bend down and look) and you can feel the slot in the cam where a thick screwdriver needs to be inserted and the cam turned.
Another good idea is to pull the cam out of the caliper and grease it - undo one of the wheel spindle clamp bolts and screw it into the cam from underneth, then grip it with a set of mole grips and pull it out.
These BMW cafe racer builders that seem to be springing up everywhere are a good source of work for me at the moment, correcting all their cock-ups.
There is a cam that holds the caliper to the slider. This cam needs to be rotated on each caliper so the inside pad is just skimming the disc.
Undo the cam cover underneth the caliper (17mm or 19mm hex head) put your finger up inside (or bend down and look) and you can feel the slot in the cam where a thick screwdriver needs to be inserted and the cam turned.
Another good idea is to pull the cam out of the caliper and grease it - undo one of the wheel spindle clamp bolts and screw it into the cam from underneth, then grip it with a set of mole grips and pull it out.
These BMW cafe racer builders that seem to be springing up everywhere are a good source of work for me at the moment, correcting all their cock-ups.
Seeing as the builder of the cafe racer made such a cock up on the rear brakes i expect he didn't have a clue how to set up the bmw front ATE brakes.
There is a cam that holds the caliper to the slider. This cam needs to be rotated on each caliper so the inside pad is just skimming the disc.
Undo the cam cover underneth the caliper (17mm or 19mm hex head) put your finger up inside (or bend down and look) and you can feel the slot in the cam where a thick screwdriver needs to be inserted and the cam turned.
Another good idea is to pull the cam out of the caliper and grease it - undo one of the wheel spindle clamp bolts and screw it into the cam from underneth, then grip it with a set of mole grips and pull it out.
These BMW cafe racer builders that seem to be springing up everywhere are a good source of work for me at the moment, correcting all their cock-ups.
Just had a look at this, this afternoon and to be honest it all looks good, in fact all the parts look new and set up as described by steptoe, good point to remember for the future as there's limited info on this in the Haynes manual. Next concern is the rattle from the right hand cylinder head, possibly end float or valves out of adjustment but not a good sound at all!
