Master cylinder for better brake - Kawasaki KLR 650 Forum
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post #1 of 19 Old 07-07-2014, 11:47 PM Thread Starter
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Master cylinder for better brake

I just installed a 250 Ninja master cylinder off Ebay to test the effect on front braking.

Yep, $25.00 delivered..... It includes reservoir, banjo bolt & washers, brake light switch. It took about 15 minutes to remove the stock master, install this one & bleed. I will pump it up and bungee the brake lever over night to see if there's any more tiny air.

The lever is longer, has stroke adjustment and just fits with my bark busters. After lubing the pivot points, the braking effort is very significantly reduced. The front brake is improved as indicated by shorter stopping distance and increased front end dive being apparent. I think I'll keep it on the bike.

This master has a 10 mm bore as opposed to the stock 12 mm which about 50% increase in application pressure, all things being equal. There seems also to be a bit of application slack (clearance) like with the original KLR master so will play with inserting some shim stock while checking to make certain that the compensating port remains clear.

One caution is that I don't think that this will work with the stock front hose because the expansion of the hose under pressure is estimated to reduce application volume too much for the smaller master cylinder delivered volume.

I still plan to do the dual piston caliper upgrade at some point and then assume that this master will not produce enough volume. It will be interesting to see the effects. For $25.00 which I can recoop when someone needs a master on a smaller bike...way-the-hay?
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post #2 of 19 Old 07-08-2014, 09:47 AM
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Wow chrome. Bling on a KLR.

Thanks for experimenting with this. I've seen some of that stuff on eBay and wondered if it would work. Looking forward to your experience with the dual caliper upgrade.

My Kaw Barn - 2004 KLR, 2006 Concours (sold), 1997 Bayou 400.

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Last edited by klr4evr; 07-08-2014 at 09:51 AM.
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post #3 of 19 Old 07-08-2014, 12:12 PM Thread Starter
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I think the dual piston caliper and a smaller bore master cylinder will not be able to be used together but will see. :-)
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post #4 of 19 Old 07-08-2014, 04:03 PM Thread Starter
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Just returned from 50 miles of mixed freeway, country and city riding. I bungee corded the brake lever over night which seems to have dissolved some trapped air and improved the brake residual travel even more. I'm very pleased. It remains to have others compare with their bikes but it's staying on mine for the time being.

I'm looking for a stock Gen2 front rotor as it looks like I can make an adapter plate to mount the two piston caliper I have to use with the larger Gen2 rotor. Interesting to play with these things.

I was able to pull the stock lever to the grip but this one has a longer lever, apparently some compounding and smaller bore so the increase in braking is noticeable. The front tire chirps on harder pulls. I don't know what pads are on this bike as haven't paid attention when they were off. It might be that there is some opportunity there also...
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post #5 of 19 Old 07-08-2014, 06:06 PM Thread Starter
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A friend emailed this link regarding master cylinder ratios. Interesting as there are some base lines from which to consider...
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post #6 of 19 Old 01-24-2015, 11:21 PM Thread Starter
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A quick guesstimate shows that the pad area of the SV650 caliper is about 150% of the Gen1 KLR. The swept area of the 280 mm rotor is 110% per revolution, of the 260. Ninja 10 mm master versus stock KLR 12 mm. SV650 piston area is 125% of KLR piston area.

So what is possible from a master cylinder which applies 150% of the pressure + 150% pad area + 125% piston area + 110% swept area per revolution?
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post #7 of 19 Old 01-25-2015, 01:05 PM
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The master cylinder piston area is proportional to the square of the diameter, thus the ratio looks like 144/100, or 1.44 increase, comparing the application pressures to me.

The pad area does not figure in the static friction equation; the force of friction is equal to the coefficient of friction times the force pressing the surfaces together only; similarly, the "swept area" isn't involved in static friction consideration.

[Caliper] piston area? With 125 % piston area, under the same pressure, I'd expect 125 % of the force pressing the surfaces together, given the same hydraulic pressure.

Braking effect? Should increase linearly with the increase in rotor diameter.

Clearly, you'll obtain greater braking effect the way you're going; modulation and control may become critical factors.

Last edited by Damocles; 01-25-2015 at 01:11 PM.
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post #8 of 19 Old 01-25-2015, 05:07 PM Thread Starter
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A test ride showed that the pads which came with the caliper needed some attention. The braking was very poor initially but heated them up and they seem quite good for now. I don't know that they are as have been focused on the fitting. The Ninja master cylinder's stroke is on the edge with this caliper volume. I will surface the pads when I remove the caliper to paint and detail the fitting.

The pad make & model was part of my problem in considering friction as no way to determine even the base line. I could only agree when reading Damocles' points as cannot tie it together as yet...maybe ever? ;-)

Anyone know of a pad clamping pressure to friction chart for any bike disk pads? I'm interested as to how the "curve" trends.

OK, the impressions:

Next to new (couple of hundred miles?) Shinko Trail Master 3.00 x 21 with Tubliss on front, FWIW.

Wet road/damp road pulling the lever nearly to the grip locks the front tire and deflects the forks such that had one near miss from dumping the bike. OK, not bad!

Dry road (about 14- 15 C or 60 F) the tire cries and slides intermittently. I could manage to lock it up with a very quick and hard application. If had a tiny bit more stroke, it would lock completely. I might stick another dime to the master piston.

I think that I'm at the point where don't need any more braking effect unless ABS were available.

The set up is: 250 Ninja master cylinder with slack shimmed, braided brake hoses, Gen2 front rotor with bolt holes counter bored by 0.035", Suzuki SV650 master cylinder with unknown pads, Deville adapter plate to mount caliper to fork leg.

Cost was very low for the set-up, excepting for the unknown of the adapter plate. If there is interest, I will consult Terry to obtain a quote for a batch.

Last edited by Normk; 01-25-2015 at 08:55 PM.
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post #9 of 19 Old 02-05-2015, 07:51 PM Thread Starter
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Some follow up on the front brake modification in the form of hypothesis:

The master cylinder used on Gen1 & Gen2 are the same therefore the lever effort to pressure is the same.

The caliper piston area is virtually identical between Gen1 & Gen2 front calipers, therefore the clamping effort is the same for both calipers.

The rotor diameter is 260 mm versus 280 mm which means the average swept distance per revolution of Gen2 is 110% of Gen1.

The pad area for Gen2 is 120% of Gen1 pad area.

Gen2 braking is better than 110% of Gen1 so the improvement (given the same pads EBC HH) therefore some other effect must be providing the extra braking.

A frequent claim is made that brake pad area/size has no effect on brake friction but this is clearly not correct. Another factor is that braking effect/friction is not linear with apply pressure/clamping force. One can recognize this by simply experiencing the braking effect of any vehicle under increasing lever or pedal effort.Applying a given pressure to the pedal or lever provides a degree of braking. Doubling the application effort may double the braking or result in greater or lesser braking which shows that the relationship is not linear.

When one reaches a certain degree of braking, applying additional effort to the lever or pedal results in very little braking increase because the pad to rotor friction has reached maximum. At this point, adding increased pad area to the same caliper will result in increased braking.
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post #10 of 19 Old 04-21-2015, 11:07 PM Thread Starter
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We did another SV650 caliper & Gen2 front rotor modification to a Gen1. The 250 Ninja master cylinder was broken so we used the stock KLR master for the time being.

Mike found braking to be much improved over stock. He could not duplicate my (with the 250 Ninja master) howling front tire and rear off the pavement but that will come when the master arrives.

We did have an interesting learning experience, having encountered a bent caliper carrier. I don't recall having encountered this issue before but after struggling with bleeding and concluding that all air was cleared, we began looking for another cause for the inability to obtain a firm lever.

The symptoms of inability to pump up to achieve any significant pressure seemed like either significant air or damaged master cylinder primary cup. I had another master cylinder so a swap was tried but with no better results.

Some careful inspection while applying the brake showed some angular movement of the caliper to the mount. Measurements, eye balling, we tried swapping the adapter plate and pads with known good ones. There was no improvement so we swapped the caliper support bracket which cured the symptoms. We spent some time in comparison and measurements, then succeeded in correcting the distortion. One clue was the "bruise" to the bottom of the lower piston housing.

As soon as the new 250 Ninja master arrives, Mike will also be capable of stoppies.

Measuring braking distance was quite a challenge, and still one in which we lack confidence. Stopping from a marked point seemed most workable so we used 40 mph and repeated tries. The stock KLR seemed to require about 54 feet while mine consistently made stops in 18 feet. Please note that this should not be equated to published stopping distances since there was no reaction time involved. I think that the best which can be concluded is that the braking distance is very significantly improved.
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