Manual rear brake to hydraulic convertion

This is mostly for the guys out there converting there bikes to cafe' but it could be modified to fit the guys making bopper and forward controls. What is your guys input and has anyone else done anything like this before. Remember this is just the preliminary drawing and write up. more to come as i biuld and modify.

 

In your last two pics you have the brake activation arm in the wrong orientation. It is normally pointed downward. With what you have drawn it would be releasing the brake on activation instead of applying.

Correction: It would still be applying the brake as the brake cam would still be giving a spreading movment.

There is a critical problem with the master cylinder not following the radial movement of the break lever though.

Ghost

 

Ghost, you would think so, and I agree that this is the "wrong" way to attach it. But since it's a cam that turns to activate brake, (it just does from vertical and narrow to horizontal and wide, to spread out shoes) the fact is that it can turn clockwise or counter-clockwise and it will still activate the brake. As long as the brake is in the "not activated" position when you attach the lever.

Edit, oh wow, either my reading comprehension is sucko or you edited that right as I said my last post, anyway never mind

 

my understand of the rear brake is that it is pulled in a counter clockwise direction. that is why i rotated the arm in to the position its in to push the arm away. The Cam off the level needs refining i need to add a recoil spring to the brake lever some how and a stopping pin. im going to angle the master cylinder so that the radius will be close.

 

I think the light bulb swiched on at the same time!! :lol: :lol:

 

The way you have it will actually work. The pull motion of the arm in the downward position gets switch to a push motion with the arm pointed upward.

If using the stock brake pedal shaft. There is already a recoil spring on the shaft. Try looking at the rear brake on the '83 XJ900 Seca, or 82 XJ1100 Maxim for the way to position the master cylinder.

Ghost

 

Good write up and details.
What if the added power of hydraulic assist causes lockups to happen more easily and more often? How powerful is that actuator? What is the needed strength? These are questions that you'll need to consider.
I just can't justify doing this. The manual system works well enough. If your going to go this route, you should go all the way by converting the drum brakes to disc. Then you wouldn't have to worry about delamination and you could use existing parts that are made specific to the application. Some automotive parts would be over the needed strength.
I would just get the disc, caliper, mc and lines from an 1100 Max and do the full conversion. :wink:

 

there is going to be trial and error to a point but the slave is from a manual transmission with a 3/4" bore it maybe to big. It all comes down to the fluid transfer from the master to the slave going from a small diameter to a large the pressure required will be less. In turn the travel of the slave will be less and in turn hoping to lessen the change or lock up and pressure applied to brake lever. What would a conversion cost and what is all that is needed. The reason i am going like this is do to me having a Rear set installed and i can't apply my rear as hard as i want to.

 

i had the same idea and i intend to do it. when i get to it. definitely watching, nice pics and nice idea mate

 

The disc conversion would likely need a rear rim from the 1100 as well. Also the drive pumpkin because the splines are different and you would probably have to make some spacers. Total cost? I would look here on site and ebay for parts.
Which ever mod you do, I wish you luck and keep us informed with pics.

 

the brake backing plate isn't thick enough to thread into, you might get 2 threads if your lucky, maybe TIG on some extra stock. move the brake switch up to the pedal or use a pressure switch, just for a cleaner look. the geometry of the master needs work

 

Pretty slick! I'll be checking in.

 

im going to run a bolt from the backside though with a 24 guage piece of metal to help transfer torque from tightening the bolts. look into the dics converson would cost about 400-600 for rim, rotor, and all brake pieces.

 

You could use your rim, but that would require some serious modding so that the drum cavity doesn't interfere with the disc and some spacing mods too. Probably more work than anyone wants. :lol: Your idea looks workable, let us know how it works out.

 

I thought for sure that there were 900 and 1100 with discs no?

I'm surprised that it would cost so much.

 

what if you left the brake plate alone and attached the slave right to the swingarm

 

thats possible will look into that too thanks

 

Why not go one step further and link the front and rear?

 

I will answer those questions. In order to link the front and the rear there would have to be a proportioning valve added and it would have to be adjustable. With that there would be a lot of tweaking and it couldn't be a any DIY job. You would really have to know the brake system and how the bike should and will handle. Don’t get me wrong there are bikes out there that do have single brake actuation. For example Cam-am's are dual braking the down side and the danger would be if you slammed on your brakes to avoid a car or obstacle you may unintentionally lock your rear or front up and lay the bike down.

Onto the suggestion of putting the rear slave master on the rear rack arm. It really can't be done with the very tight clearance we have with the rear tire. The distance would be to far and could cause may possible braking points.

 

i was thinking of putting the slave on the swingarm. or on something that goes between the two. nowhere near the tire.

like mentioned, the size difference of the master and slave cylinder bores determine the force needed to apply (or lock!) the brake

 

and with the right sizes or propotioning valves a linked setup should be fine.

 

you would have to upgrade you brake master on your handle to a larger diameter in order to displace the correct amount of fluid. and the propotioning valve would have to be calculated to account for current displacement and the additional displacement for the rear slave cylander.

 

If it were me I'd move it all to foot control and clean up the bars.

 

Well the reason this all started was because he installed rear sets and was looking to get the rear braking power he lost with it. Having the same issue, by the way, so I'm curious about this mod.

 

to clean up the bars, now i get the linking idea still i wouldnt do it, i want my brakes separate so i can use them as i have used to.

doing the disc conversion would make more sense.

i plan to switch the brake light with the m/c or brake lever movement, or with a banjo bolt with a switch on the m/c. less wiring and less things at the back

 

Hey road rash as I progress first is getting the rear set up which I prob start this weekend. And take pictures of it. But it will take time to get all the parts together. But that is why I lost the leverage of the long brake pedal and really need it. Like always keep your guys informed

 

@Wrench. Nice drawings.

I would consider putting that actuator on a pivot shaft to push the arm radius. This may eliminate most lateral stress on it.

Edit: Thinking about it. it may eliminate some in one direction and introduce stress in an other without the use of a stop bolt some place.

Good Luck either way. Nice project.

 

to move the brake arm on the wheel the same distance and apply the same force, with a shorter foot pedal, you either have to move the foot pedal farther or push on it harder. makes no difference what you use, hydraulics or levers

 

I disagree. If the MC piston is larger than the slave piston the slave piston will travel further than the MC piston . The trade off is the amount of force the slave will output in relation to the MC. While it is likely this was considered in the design of that suzuki system, this is obviously not the same application.

Edit: Adding, Leverage on the MC does come into play regarding the torque needed to operate the brake cam.
I hope for wrenches sake that the actuator arm can handle any lateral forces introduced without getting mangled up. From a solid mounting stand point it''ll bend one way and from a pivot mount "I'm guessing" it'll go the other way without some type of physical stop to help.
Location is also huge factor in the pivot shaft that I suggested. Lateral force can be minimized in two single directions by finding the optimal pivot point.
Then again, all that can be thrown out the window if its a strong enough shaft to begin with.

 

Hey Wrench, earlier I said that you might have to get a different rear rim to do the disc conversion because of the disc being too close to the drum recess. I was wrong, because its been done with all the rear rim on the front conversions. So all you should need would be a disc, caliper, lines,mc and brackets.

 

Which entails the purchase of rear tire conversion kit, caliper, possibly caliper rebuild kit, the process of modifying the rim, possibly pads, rotor, and finding a specific MC that'll work the system. Then, replanning of the whole set-up. Bad ass idea, whole other thread.

 

Taking a step back to this for a moment.

If you fashioned a mounting bracket off from the swingarm you could locate the slave cylinder under the swing arm to operate in the same fashion as the rod system. This would give a much stronger mounting base to work from.

If you need a smaller diameter slave cylinder look at a bobcat skid steer for a steering assist slave cylinder. IIRC they shoud be about 1/2" diameter piston.

Ghost

 

Nice. Good call. It's nice and flat under there too.

 

Thank guys wyourself all your suggestion and work with them.

 

buff i hope you are not talking about stock parts because it is beyond my comprehension why would one do a disc conversion and use an xj brake caliper

i have few if someone wants.


i would turn the drum down a bit if not else just to have more space to put things to

 

Well i have found the pull slave that will work attaching it to the lower part of the arm. in thery that is. I now have to find a master with a 3/4 tp 5/8 bore

 

thats a nice find mate how much is it ??

 

41.80 with free shipping. Im still looking at finding a master cylinder with a 3/4-9/16 bore size

 

may have found master waiting on reply form seller about the bore diameter

 

Just a thought: Do we know that there is enough throw in these masters and slaves to fully move the stock lever? Just looking at all variables.

 

yes with a 3/4 bore master it will move the slave 1 1/4 front fluid displacement calculator i found online

 

Cool idea! I'll be checking back!

 

Wrench26, greetings! I have not read all these posts, so if you have covered this before, my apologies, BUT, have you given any thought to the sensitivity your new brake pedal will gain as a result of using hydraulic power to actuate the rear brake? You could find yourself constantly locking up the rear wheel even though you just lightly apply the brake. Just something I think you should consider, huh?

 

Already been covered.

 

how long is the brake pedal lever on the rearsets?
the original setup on my seca looks like 10lbs of force on the pedal puts about 10 ft/lbs of torque on the spline shaft on the back plate.
the original pedal is 9 inches pad to pivot, with 1 1/4 inches of free play.
i think you would have to stand on the pedal to make the hydraulic system work.
can a drum brake work with almost no freeplay like a disk?

 

ok to answer alot your questions... here we go
1. the amount of force required to active a hydraulic system is far less than a manual system due to fluid displacement. the fluid displacement will be from a 3/4 to 7/8 bore. The master cylinder has 3/4 bore and a travel distance of 1.75. that will allow me to displace 67.5cc of fluid into a slave with a max travel of 1.25 in with a 7/8 bore who total displacement is 56.3 cc of fluid. i will have the advantage of a smaller cylinder diameter on my master than my slave giving me a higher force input.
2. free play the free play you have in the petal is far less at the activating arm than in your petal. there is only about 1/8-1/4" play in the rear. That will easily be compensated by the travel of the slave cylinder.
3. you will not have to stand on the petal due to hydraulic displacement from a small cylinder to a large cylinder increases your physical pressure you apply
4. there will still be a little play in the system.. you need very little clearance as it is with drum brakes. about 1/32" of and inch between the pads and the drum.


i hope i help cleat up any questions and they were all great one too thank for the constructive thought keep them coming

 

the only thing we don't have yet is the measurements of the new brake pedal.
your going to get 136% more pressure at the wheel with 73% less travel at the wheel.
so when 10lbs is pushing on the master piston, 13.6 will be on the slave piston. so far so good.
1/8 inch freeplay at the wheel is .17 freeplay at the master cyl piston, this is good.
now the actual brake pedal length and the length of the short arm that attaches to the master.
sat the foot pad is 5 inches from the pivot and the short arm is 1 inch long.
10 lbs of force on the foot pad makes 50 lbs on the short arm and that puts 68 lbs of force on the slave piston, that might not be good.
originally i was thinking large master to small slave but that's not what we have.
maybe extend the short arm of the brake pedal to reduce the 5 to 1

 

Ok what is needed to apply the manual peddle now... and that will be what we need to get to.. i will go take measurement of the peddle i have now. and the old one.

 

way too much thinking for my taste. do it, if its not good do it better. the next time youre a pro

 

if you shorten the back splined brake arm about a inch, that gets you real close. that's with a 5 inch pedal with a 1 inch arm