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Discussion Starter · #1 ·
After disassembly, hydro sonic cleaning, and rebuilding of my front brake caliper with new gasket and brake cable I've come to realize my work was in vain. The caliper was a flawed design with a 3 part pressure disk using pin bearings in the center that always slip out of their groves and cause the brake pad to brake unevenly which causes a horrible squeal. It's now time to upgrade to hydraulic (I knew it was inevitable, I just wanted to delay it for a couple more years) I'm attaching a link to the Honda twins site that show how a guy came up with a pretty ingenious 3 part bracket design using relatively common tools and equipment anyone could have access to


My idea is to come up with a 2 part design that, instead of joining with fasteners, I'll weld the plates together. And as much as I respect how he managed to hack the steel into an attractive shape, I feel drawing the design on CAD and letting the CNC do the cutting is the right way to go. Luckily I work in a steel warehouse and plate is plentiful and free around here so I got lots of fuck-up room. Any ideas for specific caliper and brake lever/reservoir would be appreciated

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Lots of ways to do it, the calliper has to fit the disc width and since your disc is fixed on the hub and has no way to float on that hub, then you need to have it aligned perfect if not float. 4-pot calliper or 2-pot opposing piston type calliper design are nice in that they hydraulically self centre and far out perform any brake that only works on the one side.

Aluminum is a far more appropriate and easier material to work with when you are making brake mounts that are bolted to aluminum fork legs and the lighter your unsung weight the less mass your shock absorbers have to deal with. Think Aluminum.
 

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Discussion Starter · #3 ·
Thank you for the input trailsrider, I'm attaching an exploded view of the original caliper that shows that it floats on a swivel.
Font Circle Auto part Pattern Drawing


I imagine I could recreate this with a piece of stock cut to size and milled to the correct I.D. although it looks like the pin is shaped as a grease trap and probably means the stock would need to be counter sunk, seals fitted, ect. Which makes a fixed bracket much more appealing. The guy in the link made his into a fixed bracket in 3 pieces, one bolted on forks, one bolted to caliper, and one "sandwiched" between the 2 in order to compensate for the caliper placement on the disk. Chances are I'll have to mimic this technique.

I'll take your advice about using aluminum since it's just as plentiful and seems reasonable that I wouldn't want to throw the weight off on the front. I imagine ¼" thickness should suffice for this application? Also these calipers that you speak of, they operate with Pistons on both sides pushing towards each other and only require one brake line correct? Seems silly to ask but I like things laid out nice and simple.
 

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Yep, the early hinge pin with round pads was fraught with problems, and no, pistons on both sides do not require additional hoses, the plumbing is done internal to the brake. Your disc is dish shaped to distance it from the spokes and make clearance for the calliper, your new calliper will need to clear the spokes similarly.
You can flip your forks around to make the calliper mount on the trailing edge of the forks instead of a leading link calliper mount, that modification has some theoretical advantages both in brake force direction and reduces stress on the mounting points which become compressive instead of tensile.
One of the best mount points for a brake bracket is the axle itself, if your bracket can fit where a spacer currently sits on the axle you have an excellent place to secure your bracket.
axle mount example shown for clarity:
 

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Discussion Starter · #5 ·
Ok I figured that's how they worked. I've done brakes, calipers and rotors on cars and trucks, and mechanical brakes on old japanese bikes both disk and drum. But I've never had to service a hydraulic motorcycle brake so I had to ask.

I plan on setting the caliper in the same orientation as the original one was. Both the bike and myself don't weigh much and it only tops out at 75 mph, with that being said the placement should be fine and the caliper can be small. But if I'm using aluminum then I wanna make sure it's thick enough to handle the stress. ¼" should work right? For you Canadians that's about 6.35 mm
 

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I'd be taking a walk through the local bike salvage yard to see what you can find in the way of calliper options, your bracket design is going to be dependent on the parts you can source. The old honda design only hinged like that because only one puck physically moved and the other one had to move as it wore down to stay centred on the disc. Other single side designs use slides or sliding bolts, opposing pistons don't need to have slides, only the brake pads move.
 

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Discussion Starter · #8 ·
I've been searching for different conversions and found this beauty. It's a 2 plate design and located on the other side of the disk like modern bikes. Brake is a sliding caliper with 2 pistons on one side, which gives the other side adequate clearance for the spokes. By the looks of it from the back view I'd say the plates are identical in thickness and simply welded on both sides one on top of the other with the fork plate inside and caliper plate outside. Best part is I saw this caliper, hose, and lever on ebay for around $50
Wheel Tire Vehicle Bicycle hub Bicycle wheel rim
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The photo does not enlarge for me but from what I can see that bracket is very long and they went out of their way to affix it way high up on the fork leg where the mounting points already existed. It is the axle and wheel bearing that you are trying to stop from rotating so the closer your mounting bracket is to the axle the less leverage that arm will have to shear the bolts that are holding it or fracture the fork leg. I think you could design a better one then that, but it goes to show you there are a number of different ways to achieve it.

The two pistons on the same side significantly increases the hydraulic pressure and brake pad friction area, but that calliper assembly still needs to move sideways on slide bolts as the pads wear to keep the calliper centred on the disc and that type of brake does not provide the feedback at the lever an opposing piston brake excels at. It does provide slightly greater clearance from the spokes to have a static pad on the calliper inside, but there are a lot of motorcycles out there with 4-pot brakes that have made it work so the clearance problem is rarely insurmountable. You are effectively upgrading from first generation disc brakes to about third generation disc brakes when the state of current technology is more like 5th. generation disc brakes. Still a significant upgrade that will result in far better braking then what you had.

The complication with swapping the left fork leg and the right fork leg is that your speedometer drive will no longer work and your fender bracket supports would be in the wrong place, otherwise that would be a better solution to reposition the calliper trailing to the fork leg.
 

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As a side note to clearance from your wheel and spokes, when they draw diagrams of how opposing piston brake callipers compare to floating calliper designs they generally over-look one important point.


In the opposing piston brake calliper each of the pistons only need to travel half the distance which means the calliper construction is Not twice as wide. In reality fixed disc callipers are not much wider then the floating version.
 

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Discussion Starter · #11 ·
You're right the bracket in the photos is too long and give leverage for shearing the bolts, but I was gonna reduce its size drastically not only for that reason but also so it can fit between the fork and the lower fender mount (see photo of original cb200 front end)

Wheel Tire Automotive tire Bicycle tire Synthetic rubber

I know what you mean that the closer to the axle the better, I've got another photo of a gentleman who fabricated a mount that is attached at the axle, if I was more experienced with the break press at work I'd try my hand at cutting and bending a plate in a similar fashion.
Tire Wheel Automotive tire Motor vehicle Tread

I'm gonna try to build it with the 2 plate method and sliding caliper first and see how it works, even if it causes the break pad on the piston side to wear faster I'm content on spending a little more for new pads.

Just so we are clear, this is not a racing motorcycle. I've had this bike since my dad gave it to me on my 14th birthday and had less than 3k miles. I've babied this thing and did my absolute best I can at keeping it as original as possible, so you can imagine I'm somewhat sad at having to do any upgrades and ruin it's authenticity 😭
 

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No worries on brake pad wear, if your pads are not wearing evenly, you have a major problem.

Doesn't matter if it's a race bike or minibike, the brakes have got to work and be totally reliable, you can't ride good if your equipment is lacking and in this case there is no reason for it to be lacking, you are working on an antique that sold for about 600$ when they were brand new, complete with a factory warranty. The cable disc brake was one of the major reasons I passed on buying one new, I wouldn't want to ride an authentic one but a modified one with some suspension and tire improvements might be a blast.
 

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His contact patch kinda sucks on that humongous disc and it's been drilled weird, the only thing going for those 2-pot floating callipers is cheap and plentiful in the used market.

FWIW: a 4-pot calliper new would cost about 3 or 400$ plus the hose ~ 150$, plus another 400$ for the brake master cylinder and lever assembly with switch electrics for the rear brake light and the lever. Basically you are looking to bring it in at under ~1000$ worth of new parts or you might better just buy new parts.
 

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Discussion Starter · #14 ·
I can understand your reasoning for wanting to redesign things for better performance, infact it's bulletproof logic. But if I had a choice I would wish my original caliper would be refurbished rather than upgrade to hydraulic only because sentimental reasons. There's lots of bikes out there I like, but only one I love.

I'm gonna try my hand at the prototype I had in mind. I'll use 1/4 aluminum, flip the caliper on the other side, and shorten it to reduce leverage. This should well out perform the original design. And just for you I'll take measurements of the pads every 100 miles to see if the wear is drastically different. Oh and I don't like how he drilled out the disk either, but that photo doesn't do the caliper bracket any justice there were other photos that showed a better view of it, but because the zoom in is crap I see no reason to post them
 

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No reason you can't machine the original disc to make it a completely different dimension or even turn it into a floating disc carrier, there's plenty of metal there to work with.

Alignment of the disc and calliper is critical particularly if the disc can't float and that whole brake assemblies performance is dependent on your wheel bearings being perfect.
 

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Discussion Starter · #17 ·
Have you ever ridden a motorcycle that has a one finger front brake? I'll give you a heads up it takes a little practice.
Lmao no I don't believe I have, and I can assume it's not a fun experience.

I'm at work now, when I get home I'm gonna take a picture of the distance between the outer edge of the disk to the spokes, when I did it yesterday I measured 1 ³/¹⁶" which I can't imagine an opposing piston caliper can fit between. My cb750 with gsxr front end has calipers with opposing pistons now that I think about it, but it's a mag wheel with plenty of clearance

I'm starting to assume I'm gonna have to design this like a car, take a fixed caliper like #3 in your diagram and figure out how to make the whole thing float
 

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I have a brand new 4-pot in my hand right now, it measures one inch from the centre of the disc, the whole brake is just 2 inches wide. But it is made for a thin profile disc, similar to the 2-pot in your photo the heigh of the pad is not very tall.
Enduro and MX 2-pot brakes have the slide bolts built right into them, you don't need to add it, they already float.

1 finger brakes are great! I don't need more then one finger to stop my MV Agusta, it has real brakes just like a trials bike :cool: it's a little tricky braking right now because our wet roads are still covered with winter sand and salt.
 

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Discussion Starter · #20 ·
I don't think I'd want to ride a bike with one finger stop. My little ass would fly right over the handle bars.

That's crazy you have a 4 pot caliper that is that small, I bet something like that is expensive though. Looks like what a majority of people use in their conversions is just a cheap caliper for a 50-150cc mopeds. That being said, if an effective bracket can be made, then there's a potential for mass producing so-called "hydraulic conversion kits" and make some decent money as there is a demand for them.

But I digress, do you have a model number for that 4 pot caliper? Or a bike that it comes on stock? I'd at least like to see it
 
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