Ok front brakes now

[joedrum]

Havnt done a thing yet ..resting my hands today ...

 

[GTC@MSAC]

Nice Thread. I like front brakes, they help me stop. They help me stay stopped. I'm all outta ideas now. :whistling:

 

[dan filipi]

GTC@MSAC » 9 minutes ago[/url]":1xedfztw]
Nice Thread. I like front brakes, they help me stop. They help me stay stopped. I'm all outta ideas now. :whistling:

Front brakes go nicely with rear brakes. I like them too.

 

[GTC@MSAC]

The rear shoes on my '82 SilverWing screech sharply when cold. :fiddle: The rear disc pads on my GL1100 just sound a little "flat" :smilie_happy:

 

[pidjones]

I hate brakes. Put a whole can of DOT3 through the fronts on the '79 and it still looks a little muddy, but the work. Afraid the reservoir may be leaking now, though.

 

[joedrum]

Well hopefully I’ll get started soon ...my back brakes seem fine ..there double piston 1200 brakes working off a 1000 bike master set up ....the front are single piston 1000 brakes ...82 vented rotors and 1200 wheel ..so like always for me this is all about parts mixing ... :thank_you:

 

[pidjones]

If the China MC has a good sized piston and you clean it up (mine had all sorts of swarf and crud in them) you should be happy with them. I did have to bleed the MC banjo to get fluid going, but then it was fine.

 

[DaveKamp]

I like brakes on both ends, but I really, really dislike the integration scheme... my front brake doesn't exhibit enough force or response for my liking, and having the front brake activating when I'm using the rear on gravel (it's a mile-and-a-half to pavement) is certainly unwelcome.

When I replaced the front end of my '79 CX500D, I used a GL1000 front end... aside from stiffer tubes, smoother action, more travel, more support strength (Pacifico Aero fairing), it gave me dual disks, which meant the fork tubes were under equal deflection on front braking... rather than twisting the tube on one side and binding the slides. On this integrated system, I'm seeing lots of wear on one caliper's pads, and little if any on the other... essentially, I'm driving a big heavy bike with only a single disk 'front' brake. When I give this thing a brake job, it'll get plumbing changes, larger front master cylinder, and dis-integration.

GTC- the rear on my CX-500D is noisy at times, too... it seems to be at it's worst when I pressure wash dirt off the torque link... dunno why, but it's rather predictable about it.

 

[mcgovern61]

.the front are single piston 1000 brakes ...82 vented rotors and 1200 wheel

When I first got the Slug on the road, she had '81 single piston calipers with '81 rotors on an '82 wheel. Years later, I finally got the chance to rebuild her '82 dual piston calipers and found a set of '82 rotors. Swapped them out and the braking difference was significant! The smaller diameter dual piston calipers were much easier to get braking power with almost half the effort.

 

[joedrum]

Yes ..I’d sat that’s true Gerry...obviously the braking pads are bigger ..and that’s the braking key ingredient...it’s also in my thinking with single piston brakes duals on the front with going with bigger master ...

 

[joedrum]

My my ...went for a ride today and notice my clutch was not right ..ends up being window site glass failure sheesh ...so now I have to fix it ...and the front brake master has the same window..who’s idea was it for all these site glass windows anyway I hate them ..

 

[DaveKamp]

So... people frequently misunderstand the dual-piston caliper situation... and lots of other aspects of braking. I have a little bit of professional experience in it, as braking systems constituted almost 50% of my classroom and shop time. I won't go too deep into the math unless someone asks, but I'll brush on it just a wee bit:

Pad surface IS relevant to braking... but so is rotor diameter, rotor mass, airflow, caliper size, piston quantity, and a bunch of other things.

Larger piston diameter means more hydraulic surface for line pressure to act upon. Unfortunately, to accommodate a larger diameter piston, you need a larger pad, which requires a larger diameter disk.

A larger diameter disk presents more leverage on a wheel, but it also increases the inertia of a spinning wheel.... which translates to both polar moment, and gyroscopic force.

Polar moment is best described as the reluctance of a wheel to change speeds. Hold a 16lb barbell in one hand, and a 16lb bowling ball in the other. Try to SPIN them with your wrist- which one will spin easier? The bowling ball will... because it's mass is concentrated closest to the pivot axis. The barbell will not- it's mass is 3ft on each side of your pivot point. The tightrope walker uses a long stick not to provide balance... but to provide stability... from that stick's high polar moment... the walker wobbles, but steadies him/herself because that long stick doesn't WANT to spin.

What's this do to a wheel? Obvious enough- it prevents it from changing speed (like acceleration or braking). A large brake disk, once spinning, doesn't like to stop, and sitting still, doesn't like to spin.

Second: Gyroscopic force... Is the propensity for an object spinning, to want to maintain it's position in space, relative to the spinning axis. Grab a bicycle wheel, hold it by one side axle, with other hand, spin that wheel... get it going fast... now leaving the axle SITTING on your hand, release your grip. the wheel will continue spinning, and it will stay upright, resting on your hand, with the other side of the axle hanging in the air. Now rotate your body (it will slowly rotate with you) and keep the wheel spinning, it will stay upright, on it's own. Now, get that wheel up to speed, hold it with two hands, and shake the wheel up and down... you'll find that it really DOESN"T want to move up and down. That's another aspect of gyroscopic force- the wheel wants to remain in it's position in space. (gyroscopes arereally handy for building things like navigation instruments).

If you put your bike on centerstand, put it in 5th gear, let out the clutch and rev it to 5 grand, that back wheel will be spinning at what... 110mph... try to knock the bike over... IT WILL NOT FALL OVER. Gyroscopic force of that back wheel will KEEP it upright. Likewise, if you're going 250mph, and you try to turn the handlebars, the front wheel will NOT want to turn. (next time... 'countersteering')

It's because the wheel's gyroscopic force is determined by it's POLAR MOMENT. A wheel with a high polar moment, has incredible gyroscopic force... so keeping brake discs small and light, makes a better handling bike.

 

[DaveKamp]

Now, when you make a caliper with TWO small pistons side-by-side, you can make a pad thats long and skinny, following the curve of a smaller-diameter disk, but still have lots of surface area for hydraulic pressure AND contact surface.

Brakes have two important numbers... first is contact surface... this is the area that a brake pad contacts on a disk... the other is swept area... which is the area of a disk that GETS contacted as the pad passes. The difference may not be obvious... a long skinny pad on a double-piston caliper that follows the radius of a disk may have the same contact surface area as a big square pad on a single caliper... but the 'track' that the skinny pad makes, is much narrower than the larger pad.

The skinny pad allows a smaller diameter disk, but that skinny pad on a small diameter disk has less SWEPT AREA than the larger pad/single caliper. This means the skinny pad's acting surface is getting a higher braking energy-concentration in the disk, than the larger swept area. There's a big mess of thermal dissipation math involved here, but safe to say that the skinny pad on dual piston calipers means you have a small amount of metal accepting a much larger concentration of heat, in a short period of time. That makes the disk expand funny, and overheat fast...

Is it kinda stuffy in here? Am I going too fast? I can open a window...

 

[mcgovern61]

Good explanation. Thanks Dave! :yes:

 

[GTC@MSAC]

Does anyone know of a motorcycle brand or model that ever had a hydraulic drum brake?

 

[DaveKamp]

Leverage is a pretty simple concept, and we use leverage to allow a hand... or a finger, to apply a little force at the handlebar, to generate LOTS of force at a brake pad, or clutch rod. In any leverage system, we're trading force for distance, or distance for force. Hydraulics is no different, and using it in braking is simple, but some simple concepts need to be understood:

First, is that leverage exists in more than one place. First point of leverage is where you pull the lever with your hand.... with respect to the lever pivot point. Your little finger's position can develop more leverage than your first finger's, because it's FARTHER from the lever's pivot point. This is 'HANDY' because... when you need to pull on a lever, your little finger is frequently the one with the worst reach (it's shorter) and it's generally not the 'strongest' digit of your paw... but it's strategically located well for a 'conventionally' arranged handgrip-lever, and I'll use a clutch as example:

When you go to pull in a clutch, an average individual will reach with two middle fingers, keeping first finger wrapped on the grip. Once the lever is partway pulled in, the little finger jumps in, and once wrapped, the little finger has more than enough strength to HOLD the lever against the bars. now, many clutch linkages are 'progressive' in their leverage, but the fact that the little finger is FARTHER from the lever pivot, gives it substantially more force multiplication than the first, second, and third fingers. The advantage of the first, second,and third, however, have the ability to rapidly modulate the clutch for proper release and shifting control. You wouldn't want to sit at a light, holding the clutch in with just your first finger, but notice that your little finger can? Study the muscle structure of your left hand, and you'll see why...

But that's not important right now...

A simple hydraulic system consists of two cylinders- a master, and a slave... and in any realm of Fluid Dynamics, it's all about pressure. You put a pound of force in one end, and that is translated to fluid pressure, which is exhibited at the other end. IF the piston surface on both sides are same, then force and distance will be identical. If surfaces are NOT the same, then the smaller side will require more travel, at less force, than the larger, and the larger will require less travel, and more force.... and it's all about comparing surface area.

Now, this is all pretty obvious stuff for most of you, so apologies if it's boring...

but let's jump up to the point:

Comparing a single piston to a dual piston caliper... you'll find that the dual-piston caliper has more piston surface area, than one significantly larger single piston caliper. This means it can create more force, in a much smaller path of swept area (long skinny pad, remember?).

Let's say it's a 2" single piston... that's 1" radius... square that, multiply by pi, and you have 1x1x3.14, and you've got 3.14 square inches.
Compare that to a 2.5" piston... thats 1.25*1.25*3.14 = 4.9 square inches.

TWO 2" pistons yields 6.28 square inches... while ONE 2.5" piston is only 4.9 square inches.

Now... leverage isn't everything... but it's a start. Stay tuned for the next episode!

 

[joedrum]

I agree that's all simple ..im working with what I have ...would I have done things different...maybe so ..one thing I love about 1000 setup is the hydro brake switch ..never had one problem with it in decades of wing experience ..dp I need brakes so good to do brake wheelies no...like newer bikes can do ...not a option for me right now ..just trying to get good front brakes
.for my riding style. And what I have to work with ...i have a bike that's way more powerful than its design . I've got my work cut out to get even close

 

[DaveKamp]

Basic rules of fluid power systems:


Liquid-based systems are called Hydraulic

Gaseous-based systems are called Pneumatic.

Gases are compressible. Fluids are not.


--Pneumatic systems that experience the presence of liquids fail fast.

--Hydraulic systems that experience the presence of gases fail faster.


BOTH can exhibit some really bad character when you mix... especially if it's a hydraulic system with air bubbles, because a rapid change in pressure in an aerated oil results in 'diesel effect'... compression ignition of the hydraulic fluid due to rapid compression of a gas.



(see "Combined Gas Law"... and Pressure = Volume/Temperature)

So we don't want air in a hydraulic system... we also don't want water, or cleaning solvents, or rotted-out rubber O ring fragments, or insect guts, or oxidized pieces of Joe's plastic windows, or zinc and aluminum oxides accumulating on the sliding surfaces, or inside the hoses.


Which can be a challenge, because brake fluids are USUALLY HYGROSCOPIC... that means... they usually absorb water... right out of the air. Good for keeping stuff clean, until the fluid becomes saturated.


BTW... ethanol is hygroscopic... that's why it's used in 'fuel drying' products... it absorbs the water, and binds to it, in an effort to attach something somewhat flammable to something that clearly isn't, in an effort to gracefully remove it from the fuel system... unfortunately, ethanol is really CAUSTIC, so it's hard on aluminum, zinc, magnesium, lead, tin mixes commonly found in say... carburetors and brake cylinders...

 

[DaveKamp]

Sorry for the fragmentation here, I'm writing in stages, and posting it when I SHOULD be doing 'other things'... :-D

 

[joedrum]

Hmmmm well I sure hate those windows I’ve never seen one that didn’t go bad ...seems stupid to have sush a thing...