If you want there are pressure switches built into a banjo bolt that will work, but I'm not anxious to introduce another failure point if I have an alternative -- I have seen them fail.
If you are working out a single acting caliper remember there are actually two faces the pressure bears against: the piston and the back of the bore it is housed in. This side pushes the mobile part of the caliper in the opposite direction as the piston(s), applying force to the inside pad(s). NP will be the same as if you were working out a double acting caliper.
Rob
Rob, as small point re single acting calipers that pivot instead of using a cross link to activate the other side, like ancient Honda CB750s etc where the caliper arm pivots. In that case, the slave piston area is just that of the single piston, correct ? Even thought the rotor sees pad area and load on both sides. I guess in that case, a splitting hairs approach would to look at pad areas too. Figure out the pad area face loading that is, and compare it all the way back to the hand lever.
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Quote:
Originally Posted by mcromo44
Rob, as small point re single acting calipers that pivot instead of using a cross link to activate the other side, like ancient Honda CB750s etc where the caliper arm pivots. In that case, the slave piston area is just that of the single piston, correct ? Even thought the rotor sees pad area and load on both sides. I guess in that case, a splitting hairs approach would to look at pad areas too. Figure out the pad area face loading that is, and compare it all the way back to the hand lever.
All single acting calipers operate in the same way regardless of the method of motion, otherwise there would be force applied to only one pad and little if any stopping power -- there must be a matching pressure on the inside pad or either the piston would drive itself right out of the bore or the rotor would flex / cone away from the one pad. Either way there would be little if any braking power.
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All single acting calipers operate in the same way regardless of the method of motion, otherwise there would be force applied to only one pad and little if any stopping power -- there must be a matching pressure on the inside pad or either the piston would drive itself right out of the bore or the rotor would flex / cone away from the one pad. Either way there would be little if any braking power.
Rob
I realize all that, all I'm doing is tossing in the fact that both pads see energy from only one piston in a pivot bracket style, as compared to a single bore dual piston cylinder with cross link.
So what is the bottom line on these master cylinders?
They look a whole lot like Brembo units. Knock offs of the same design or a redesign that just looks like a Brembo?
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Finally installed
At long last I have installed the master cylinder.
First, the quality of the new unit. The aluminum it's made of feels very similar to 7071 - T5 (according to the feel of the the cutting of a standard file I use to determine the relative properties of an unknown alloy) with little zinc -- no, it's not pot metal. It does look like they took a mold off of a Brembo unit, showing the lot number of a 16 -18 unit (4759), and a casting year of 2006 without a month punch mark. The casting parting lines are sharp and consistent, implying a relatively fresh permament steel mold. Fit and clearances of the lever to the body are a touch on the loose side, but nothing excessive. If it loosens up I'll bore the lever pivot for oillite bushings, but for the moment it's just fine with a generous dollop of urea grease.
I could not tear it down without a complete rebuild kit, and this supplier doesn't offer any such thing. In light of this I did a thorough evaluation of it's operation by installing the maniflod, capping the fittings, bench bleeding it, and applying a constant spring pressure to the lever. After 6 hours the lever had moved toward the bar only 0.6mm, well within my standards. Action is smooth (once I applied urea grease to all pivots) and with the minimal volume on the bench it gave a good positive stop within 0.2mm of covering the compensating port -- excellent. One thing I would do if I could tear it down is to shim the piston closer to the port, but as it is it is quite acceptable.
The biggest delay was rigging the brake light switch. There is no provision for it, and it took some creativity to install one. Fortunately I had a subminiature microswitch (Sounds like a redundancy, doesn't it?) in my bench stock with barely sufficient current capacity for the job. It is not, however, waterproof, so I am sourcing a washdown type from McMaster Carr, P/N 8085T13, $5.81, that is very water resistant, has roughly 2 1/2 times the current capacity of the one in use at the moment, and the same footprint. Cool. The only drawback is if you adjust the lever distance the switch will have to be adjusted as well. Mounting it was a bit of a pain, consisting of drilling and tapping the inside of the lever pivot to 5mm x 0.5, loctiting a screw into it, then drilling and tapping that to 2.5mm x 0.45 for the hardware securing the switch. I can tell you that this made me nervous -- watching the tap twisting slightly and reversing the tap every 1/8th turn or so to clear any burrs. It took almost an hour to thread 6mm deep. Regardless, it did work, and after that all that was necessary was to make an adjuster quadrant from a scrap of 0.85mm thick 6061 sheet and mount the switch to it. Notice that the switch arm is bent back on itself to engage the lever adjustment detent screw, and the wires are attached to the common and normally closed lugs in order to activate the brake lights when the brakes are applied. I have done this many times to replace the crap Honda switches without a problem.
The second hurdle to clear is making a manifold to adapt the single outlet to the two -3 AN fittings I have on my system. In this case I envy the simplicity of a banjo bolt, but we must pay for our proclivities, musn't we? At any rate, I got an 1/8th pipe male to two 1/8th pipe female brass tee and machined off everything that didn't look like it needed to be there, resulting in an internal volume of only 0.2cc's (with the fittings installed), and threaded two 90 degree 1/8th pipe to -3 AN stainless fittings into it. As it turns out running an 1/8 pipe tap into a 10mm x 1.0 hole is a cinch: the pitch of the pipe thread is 0.94mm, very close to the 1.0mm pitch of the outlet. No problemo if you know what you're doing. All that was left is to teflon tape the male thread and run it into the master cylinder. BTW, I have used pipe threaded fittings on literally hundreds of brake conversions without one instance of leakage or any other problems. The advantage of this is the adjustability -- given the proper fittings it can be made to fit practically anything, and if angle adjustments are necessary it's simple to just turn the fittings to the angle you want without opening the system at all, something that can't be said of any other method.
On the the important part: the feel of the system with the new master. In a word -- very similar. Maybe a small percentage less lever pressure than with the original master, but not noticable to anyone who doesn't have lots and lots of experience with lots of different systems, as I do. One thing I noticed is a slightly more positive feel at the lever, but again not very much.
Obviously I won't have any information on the longevilty of the master for a while, but suffice it to say I have capped the the fittings on the original master and put it away just in case.
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Location: Santa Maria, CA Otherwise known as heaven on earth.
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A month later
Well, it's been a month or so since the master was put into service. No negatives have surfaced yet, and I really don't expect any.
After ironing out a bleeding issue involving an air bubble trapped in the secondary chamber (behind the primary seal) that would occasionally burp past the seal and add a little sponginess to the feel, the master is performing quite well. Under normal braking the feel is only a small percentage lighter, but once I trusted everything enough to do some max effort stops I found that small percentage got somewhat bigger. It really takes a noticable amount less pressure to drag it down from triple digit speeds as it did with the OEM master with no grabbiness or other evidence of a misproportioned master cylinder. I like it!
I'm starting talks with the supplier regarding becoming an importer, that is as long as they can be supplied without the Brembo symbols on them, can be supplied with a larger reservoir, and with an outlet threaded 10mm x 1.25. Don't know if they'll go for it, but IMO it's worth persuing. Of course nothing will happen until I have completed my qualification tests, so look for it in about 3 months or so.
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Long term test results
It's been 11 months since I fitted the master, and on a walkaround last Tuesday I found it was leaking brake fluid from around the pushrod -- an obvious secondary seal failure. Of course I immediately removed it and reinstalled the original, which was flushed and capped after removal. One big advantage to that was the swap took a grand total of 4 minutes, a side effect of using AN fittings instead of banjos, including bleeding which consisted of retracting the caliper pistons plus a few "pump up the brakes, slowly pull in, let the lever snap back, then pull the lever a small amount several times to push out any remaining air bubbles". Voilà: a perfect bleed, and a good firm lever.
A final evaluation of the radial master: it was undersized. That's right -- I made a basic mistake when calculating the overall ratio by forgetting to factor in the greater lever pivot to finger location distance, corrected in my subsequent calculations, but there it is. The lever feel was always a bit spongy regardless of how often I bled the system due to an overall ratio of 173:1, as compared to the stock system ratio of 120:1. This mush feeling did not affect braking performance, but just didn't feel right.
It's back to the stock feel, and that's fine for now. Having said that, I am not giving up on the radial just yet. All it needs is to be bored out to 18mm from the present 16mm, bringing the ratio to 137:1, which will decrease overall effort and feel much firmer. The only problem is finding a supplier for the EPDM / EPR seals -- no U.S. supplier sells anything but new master cylinders, and when I asked why they say there is no demand for them -- in other words, in the U.S. we don't repair or rebuild, just replace. Sheeeeesh! It's obvious the "do it yourself" urge that this country was famous for while I was growing up has died almost completely! I have feelers out, including one business that sleeves old master cylinders and calipers that are no longer available new or rebuilt, and hopefully something will turn up.
A side effect of all this is, at least according to my number crunching, a Brembo 19mm RCS will almost exactly duplicate the stock ratio of 120:1. Worth considering if you have a fair amount of disposable income for some quite functional bling.
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On the contrary -- if you look at the '05 R1 front brake assembly the dimensions are as follows: caliper pistons of 30mm and 27mm, nearly exactly the same as the 919, and a properly dimensioned master cylinder to supply the proper pressure: a 16 x 18 radial unit. Ergo, the master cylinder will work with the 919 calipers. Why? While the area of the master cylinder is ~ 30% larger than the 919 master, the mechanical ratio is ~ 35% higher. The end result? The overall ratio is ~ 5% greater. Not nearly enough to worry about.
As usual, Rob nailed it, overall ratio is what counts.
But a bit more can be added.
Even if one ends up with a bit less ratio, it just means that a bit more applied lever force from the rider's hand is needed to balance out the overall equation for equal slave piston actuation pressure. The opposite also holds true.
Also.
Over ratioed master pistons, in other words small master piston diameters, need more master piston displacement to get the braking force engaged because at the end of the day, a volume of brake fluid has to be introduced into the slave circuit to displace the slave pistons so the pads load up on the rotor. So, when talking master / slave piston diameter relationships, there are actually two critical elements. One being the hydraulic forcing relationship, the other being the piston displacement relationship. Both are governed by the relationship of master to slave piston area.
Location: Santa Maria, CA Otherwise known as heaven on earth.
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Quote:
Originally Posted by mcromo44
As usual, Rob nailed it, overall ratio is what counts.
But a bit more can be added.
Even if one ends up with a bit less ratio, it just means that a bit more applied lever force from the rider's hand is needed to balance out the overall equation for equal slave piston actuation pressure. The opposite also holds true.
Also.
Over ratioed master pistons, in other words small master piston diameters, need more master piston displacement to get the braking force engaged because at the end of the day, a volume of brake fluid has to be introduced into the slave circuit to displace the slave pistons so the pads load up on the rotor. So, when talking master / slave piston diameter relationships, there are actually two critical elements. One being the hydraulic forcing relationship, the other being the piston displacement relationship. Both are governed by the relationship of master to slave piston area.
Precisely. When I read your post I did some measuring and calculating to determine just how far the pistons retract when at rest on the principle that there is no such thing as useless knowledge, and verifying the results is the only way to know if calculations are right. Starting with the lever, I measured the travel from at rest to the pads contacting the rotors -- in ten cycles it averaged 19.2mm measured 90mm from the pivot, then dividing by the interaxis ratio of 3.6:1 means 5.333...mm piston travel. To get an accurate retraction figure I had to subtract the piston travel necessary to close the 0.5mm compensating port by retracting one caliper's pistons while pulling the lever, and it averaged 3.75mm at the same point, translating to 1.04mm piston travel (I really need to shim that piston!), resulting in 4.2933mm closed travel, displacing 0.661cc's of fluid. That .661cc's will move the caliper pistons ~0.127mm, which closely matches actual measurements I've taken.
"So what?" you may say. It goes past academic interest. For optimal action the angle between the lever arm and piston, either conventional or radial, should be as close to a right angle at the normal point of action as possible. Anything else generates thrust loads, and therefore is less smooth than possible. Doing the calculations when setting up on the bench shortens tweak time in the field.
It's actually a lot of fun, and the old saying "If you can't express it in numbers it's not engineering, it's opinion." always holds true.
Oh, yeah -- the engagement numbers closely match the stock and radial masters I have used on my '02: 19.2mm con., 26.1mm (not good) for the radial, and therefore the numbers for a 19mm RCS Brembo: 19.6mm, come close to the stock numbers, and will probably functionally match the stock assembly. Unfortunately I can't afford a Brembo, so confirmation is up to someone else.
Infinitely adjustable, made of the finest materials available, and completely sourced from local suppliers -- gotta support the local economy! Order today and know handlebar Nirvana.
Precisely. When I read your post I did some measuring and calculating to determine just how far the pistons retract when at rest on the principle that there is no such thing as useless knowledge, and verifying the results is the only way to know if calculations are right. Starting with the lever, I measured the travel from at rest to the pads contacting the rotors -- in ten cycles it averaged 19.2mm measured 90mm from the pivot, then dividing by the interaxis ratio of 3.6:1 means 5.333...mm piston travel. To get an accurate retraction figure I had to subtract the piston travel necessary to close the 0.5mm compensating port by retracting one caliper's pistons while pulling the lever, and it averaged 3.75mm at the same point, translating to 1.04mm piston travel (I really need to shim that piston!), resulting in 4.2933mm closed travel, displacing 0.661cc's of fluid. That .661cc's will move the caliper pistons ~0.127mm, which closely matches actual measurements I've taken.
"So what?" you may say. It goes past academic interest. For optimal action the angle between the lever arm and piston, either conventional or radial, should be as close to a right angle at the normal point of action as possible. Anything else generates thrust loads, and therefore is less smooth than possible. Doing the calculations when setting up on the bench shortens tweak time in the field.
It's actually a lot of fun, and the old saying "If you can't express it in numbers it's not engineering, it's opinion." always holds true.
Oh, yeah -- the engagement numbers closely match the stock and radial masters I have used on my '02: 19.2mm con., 26.1mm (not good) for the radial, and therefore the numbers for a 19mm RCS Brembo: 19.6mm, come close to the stock numbers, and will probably functionally match the stock assembly. Unfortunately I can't afford a Brembo, so confirmation is up to someone else.
Rob
So, if one does not get it right, one can end up with a master that seems correctly ratioed from an overall point of view, but has the lever in a less than ideal geometric relationship with the master piston bore centreline, when braking force is being applied by the lever.
Dang this is a good thread.......havent been around wristtwisters for about a year now......currently finishing up a DR650 street-tracker project where I can use the DRZ400sm calipers. Just purchased a Magura 13mm radial m/c.
Anyway......this thread should be stickied......incredible information!!
Btw.......the '01 Honda RC-51 SP1 calipers, in combination with the '07 gsxr 19mm radial m/c........was simply awesome on the honda 919. Stock pads, stock rotors.....
Btw.......the '01 Honda RC-51 SP1 calipers, in combination with the '07 gsxr 19mm radial m/c........was simply awesome on the honda 919. Stock pads, stock rotors.....
hey artic how's the drz treatin ya? miss the 919 yet?
Having a blast with the DR650 ---- see the 'Adventure' section.
Thanks to all the fun knowledge I learned from this thread last year..... I've decided to re-apply some of the knowledge learned to the DR....
I just installed this...... its a Magura 13mm Radial master cylinder w/ a Brembo remote reservoir...the M/C is designed to have a small footprint for supermoto use so it will fit inside a hand guard. If you notice, the piston is angled to make it more compact.
This time around --- (at least for the time being) I'll be using the stock Nissin caliper to go with it...... the OEM m/c is a 1/2" or 12.7.
Thankfully --- The DR comes already with a larger than normal 290 mm front brake disk...... --- all of Suzuki's dirtbikes use the exact same caliper, just with different brackets/rotor sizes (even the DRZ400SM supermoto uses the same one).
If I do any more upgrades.... I'll probably just pick up an EBC 320mm oversized front rotor......
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