Front brake improvement - Kawasaki KLR 650 Forum
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post #1 of 10 Old 06-29-2014, 05:04 PM Thread Starter
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Front brake improvement

This has been done and discussed ad nauseum but as I'm playing again, thought it might be useful to open a thread.

As I see it there are several options for improving the braking power to the front. These options overlap with those which will increase brake endurance. I am more interested in increased braking power as have not encountered the need for more endurance as could be needed during mountain touring and the like.

In order to increase braking power, one might improve:
1) Increasing pad/rotor area.
2) Increasing rotor radius/diameter, which may correspond with #1.
3) Increasing pad frictional coefficient.
4) Increasing hydraulic pressure

#1 has been done and is well documented with upgrading of Gen1 to Gen2 caliper & rotor (marginal) or upgrading of both to 320 mm rotor.

Adding another model of dual piston caliper has also been accomplished but less often than for the 320mm rotor alone.

#3 is well reported.

#4 is the area which interests me the most at this time, although most efforts in this area have been going in what seems the opposite direction.

A friend emailed regarding a discussion of this subject area on another group to which I do not post so thought it worth while here.

There have been many reports of improved braking through the installation of improved brake hoses which expand less due to pressure. These will improve braking if:

1) The "give" in the hydraulic system preserves some lever stroke which can apply additional pressure to the caliper. This will generally be the case only when the lever is otherwise clamped to the grip by hand pressure.

2) The "give" in the hydraulic system moves the the lever to a more ergonomic position allowing the grip to apply more clamping force.

I am aware of some instances in which the more ridged hoses have resulted in poorer braking because the lever was working in a less advantageous arc.

There have been many reports of improved braking through the installation of ( usually from dual caliper applications) larger diameter master cylinders however there has been little speculation and even less investigation as to why this might be effective. The obvious question is: how does a larger piston diameter, which must result in lower hydraulic pressure, result in better braking. There are too many reliable reports to dismiss the claim.

Even the possibility of better lever arc would seem less likely, given the number of positive reports. I speculate that the reason may be better (greater) lever advantage?

I do note that we have improved the braking of many KLR's by simply cleaning and lubricating the lever pivot bolt and lever tip. I hope that no one overlooks this possibility.

I've just ordered a Ninja 250 master cylinder to try as the bore is 10 mm versus the KLR's 12 mm.
http://www.ebay.com/itm/370886528553...A:3160&vxp=mtr

Some reports of improvement have included 14 mm bore master cylinders.

Please check my calculations as am distracted by the extra time 1:1 Greece- Costa Rica game.

I calculate as compared to the stock 12 mm bore:
10 mm has 69% of the area, resulting in 145% of hydraulic pressure
14 mm has 136% of the area, resulting in 73.5% of hydraulic pressure

In this event, assuming sufficient apply volume, the 10 mm master cylinder should produce markedly increased (145%) clamping force at the caliper.
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post #2 of 10 Old 07-10-2014, 09:58 PM
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Normk,
With my bent and 're-straightened' three times F. brake lever, I think I might has enough lever travel to accommodate the 'stroke' of a mere 10mm piston!
But, I don't think a stock and standard KLR brake lever will work 'very well'!

Maybe with a SS brake hose, it will! But not with a stock hose. Too Much Stroke required.

pdwestman
Modify at "YOUR OWN RISK"!

Still riding my 1987 KL650-A1. 85,000+ miles & counting
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post #3 of 10 Old 07-10-2014, 10:07 PM Thread Starter
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Fortunately, this master came complete with reservoir, banjo bolt, washers, adjustable brake lever. I have it in the full out position and works a treat. I'm definitely not going back to the stock master unless the dual piston caliper (when finally get around to that one) requires more volume.

The feel is greatly improved also. Much less wooden than the original master.





Quote:
Originally Posted by pdwestman View Post
Normk,
With my bent and 're-straightened' three times F. brake lever, I think I might has enough lever travel to accommodate the 'stroke' of a mere 10mm piston!
But, I don't think a stock and standard KLR brake lever will work 'very well'!

Maybe with a SS brake hose, it will! But not with a stock hose. Too Much Stroke required.
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post #4 of 10 Old 09-01-2014, 12:35 AM
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Quote:
Originally Posted by Normk View Post
I am more interested in increased braking power as have not encountered the need for more endurance as could be needed during mountain touring and the like.

In order to increase braking power, one might improve:
1) Increasing pad/rotor area.
2) Increasing rotor radius/diameter, which may correspond with #1.
3) Increasing pad frictional coefficient.
4) Increasing hydraulic pressure
Just a few discussion points:

As to, 1) Increasing pad/rotor area, the area of the pad does not appear in the classic "force of friction" formula. Only the applied force between the mating surfaces and the coefficient of friction are involved. Increased pad area enhances longevity and heat tolerance, etc., but . . . does not increase braking force, unless the sliding friction formula is inappropriate in this consideration.

As to, 2) Increasing rotor radius.diameter (don't think it corresponds to 1)), increasing the rotor radius, and moving the caliper outboard from the wheel center, definitely and directly increases braking force. The leverage arm of the pad-and-rotor contact point is increased, linearly increasing the mechanical advantage of the caliper in retarding wheel rotation. This one offers a direct improvement in stopping power, without changing anything else in the braking system.

As to, 4) Increasing hydraulic pressure, increasing the caliper piston area increases force on the pad/rotor interface, with the SAME hydraulic pressure. The "dual piston" calipers do not enhance braking force by the increased number of pistons, but from increased total caliper piston area.

Reducing the bore area of the master cylinder will increase the force multiplication from the brake lever to the pad/rotor interface; however, this bore area must accommodate the necessary volume of hydraulic fluid. A smaller bore area will require a greater stroke to exploit the mechanical advantage offered.

PhotoBucket appears on the fritz currently, preventing uploading of supporting images (including your linked ones, Normk!).

As to the advantage of braided steel brake lines, in my view, improved caliper response time to brake lever movement is key. Expanding rubber brake lines seem "squishy," versus the crisp response from the metal-wrapped lines, said squish from the expansion of the rubber hoses from hydraulic pressure. The same hydraulic pressure will result in the same braking force, ultimately, with either wrapped or un-wrapped brake lines; the wrapped lines will transmit this pressure to the caliper faster, seems to me.

Finally, I'm skeptical of improvement from "radial" master cylinders, since the hydraulic paradox tells us in a closed hydraulic system, pressure is equal in all directions. The orientation of the master cylinder piston bore axis should be of no consequence, seems to me.

I have a Generation 2 front brake caliper and master cylinder; Eagle Mike reportedly has a bracket for installing this caliper on a Generation 1 (with 320 mm rotor); if I can get my hands on such a bracket, I may bolt his arrangement onto my '07 (Generation 1). Advantage: Increased total caliper piston area for increased braking force; increased pad area for longevity improvement and better thermal operation.
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post #5 of 10 Old 09-01-2014, 05:44 AM
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Hydraulic Multiplication of Force

Ah, PhotoBucket is back up, and, one hopes, better than ever!

Here's an image of how hydraulic multiplication of force operates; the small-diameter piston representing the master cylinder, the larger one the caliper piston:



Since the piston area is proportional to the square of its diameter, in this example, the 6" piston has 9 times the area of the 2" piston; thus, 100 pounds force downward on the smaller piston results in 900 pounds force upward from the larger piston. Stroke becomes critical; the smaller piston must descend 9 inches to raise the larger piston one inch. Thus, mind your brake lever geometry when you go about switching master cylinders!

Last edited by Damocles; 09-01-2014 at 05:51 AM.
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post #6 of 10 Old 09-01-2014, 12:22 PM Thread Starter
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FWIW, I have encountered circumstances in which someone has felt insulted where it was perceived that they were being talked down to. Never my intention as the other is likely both smarter and more knowledgeable than I, or that's the only reasonable assumption.

Just to knock this around a bit more and stating this intention so it does not appear that anyone is being lectured:

This is the action involved in reducing the stock master cylinder bore size (12 mm) to that of the Ninja 250's size (10 mm). As one will note, the pressure increases given the same thrust to the master cylinder piston so the pressure per square inch (unit area) must increase to the slave. The area of the slave creates the resulting thrust from the slave piston.

Using a smaller master cylinder piston results in higher clamping force by the same caliper, so long as the displaced fluid is sufficient to compensate for caliper piston movement and system expansion/stretch.

So, replacing the 12 mm stock master cylinder by the 10 mm Ninja master will result in higher hydraulic pressure, given the stroke being sufficient.

An issue is that determining the actual thrust applied to each master cylinder piston is not as simple as assuming the same lever effort. The length of the lever from each "end" of the pivot point will skew the results greatly. That the contact of the lever end to the master cylinder piston is an angular one/wiping across, complicates the leverage calculation beyond most lay level physics calculations.

A harder to qualify value is the shape and position of the hand end of the lever. I might be able to pull a given lever back to the bar while you may not. This may be because my hand is stronger but may be because the range of lever movement places it within a range which favors my weaker hand.

Add to that friction in the pivot and lever to master contact area and one finds additional unknowns. It's amazing how often I don't encounter a dry/unlubricated clutch or brake lever.

Does increasing hydraulic pressure result in increased braking (increased friction) effect?

Maybe. While counter intuitive, one can simply experience the result of increasing the hydraulic pressure by 50%. It clearly does not result in 50% more braking effect. One can also explore friction theory to explain this but most of us find empiricism to be more convincing.

At some point, increasing pad clamping pressure loses out to a larger pad to rotor area so using a "larger" caliper can provide more braking (friction) than by the higher clamping force onto a smaller pad. Some Indy car lessons were learned when a team tried what seemed to be a retrograde modification. They were able to delay braking into corners which resulted in an advantage for some time until others caught onto what they were doing.

So pad to rotor contact area, the two materials, clamping force, hydraulic pressure, stroke available, etc. are all important factors which can be very difficult to explain. Confirmation bias is huge in human thinking so we tend to accept almost any reason/justification for what has occurred despite that we could not use the same justification to predict the outcome.

My friend Mike has a Ninja master on order so we will install that one to his bike soon. I'm hoping that he will tolerate installing it to the stock hose to confirm my expectation that the hose stretch will exceed the volume required to achieve higher apply pressure. He has braided hoses to install also but hoping to try the stock hose first for interest.

My machinist friend is making several adapters so will likely do a conversion to Mike's bike also. If this works out to be a significant improvement, we can talk about a group buy for a batch of adapters. I don't know about liability factors affecting something of this sort.

Perhaps that's what has the Eagle Mike bracket for the 320 mm rotor and Suzuki caliper delayed?
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post #7 of 10 Old 09-02-2014, 05:29 AM
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Image from Normk's Post # 1 on this thread:



Image from Post # 4:



Regarding image immediately above, only a question: Why not a 320 mm rotor? Cost; unavailability of a used one?

CAUTION: Jocular jibe follows!

Normk, I see the caliper hanging, suspended only by the brake line. Shouldn't you CAVEAT this image, "Closed course, professional mechanic. Do not try this at home!"



Truth be told, my calipers hang unsuspended by anything other than the brake line sometimes also, despite the better practice of using a bungee cord or whatever as a load-bearing component.

Last edited by Damocles; 09-02-2014 at 05:58 AM.
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post #8 of 10 Old 09-02-2014, 05:48 AM
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Quote:
Originally Posted by Normk View Post
FWIW, I have encountered circumstances in which someone has felt insulted where it was perceived that they were being talked down to.
No way did I ever come away from any of your posts with that impression, Normk!

On the contrary, your posts appear ISSUE-driven; never EGO-driven!

Hope mine are the same; I may sometimes repeat your points; in effect, corroborating them. Further, I hope I always express any alternate perspective respectfully.
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post #9 of 10 Old 09-02-2014, 11:26 AM Thread Starter
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Several reasons/justifications for not wanting the 320 mm:

1) Cost.

2) I have been on at least two rides where someone has bent a 320 mm rotor, but having not seen this with a stock one, which I conclude is because of the exposed nature of the big rotor.

3) Bolting something into place which is commonly done is less interesting and provides fewer learning opportunities.

4) An off-shoot of #3: I can buy and bolt on a 320 mm but would still have to make an adapter because I want to try a "better" caliper. Perhaps this experiment will prove to be valuable to someone else due to either the success or failure. If someone can have a significantly improved front brake for $100.00 it may put the modification within someone's window of cost.








Quote:
Originally Posted by Damocles View Post
Image from Normk's Post # 1 on this thread:



Image from Post # 4:



Regarding image immediately above, only a question: Why not a 320 mm rotor? Cost; unavailability of a used one?

CAUTION: Jocular jibe follows!

Normk, I see the caliper hanging, suspended only by the brake line. Shouldn't you CAVEAT this image, "Closed course, professional mechanic. Do not try this at home!"



Truth be told, my calipers hang unsuspended by anything other than the brake line sometimes also, despite the better practice of using a bungee cord or whatever as a load-bearing component.
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post #10 of 10 Old 09-02-2014, 11:36 AM Thread Starter
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I've been married for more than 35 years so how much ego can be left?

I try to be open, honest and critical in my approach however sometimes that comes across as adversarial. I'm not afraid of a confrontation (actually, one of my defects is that I enjoy confrontation far too much) but have learned that it is seldom the path to discovering why someone holds a view when considering technical matters.

Hearing what someone believes is of some value but not much value without the context of why they hold that view. In the case of those whom have a high level of "authority" based on a track record, it is a short cut to accept what they say as strongly supported. This does not mean 100% endorsement because one holds everything open to question but when someone I do not know throws out an assertion, it's impossible to know how to weight the statement.

Asking, "Why to you believe that?", "What is your evidence?", is often provocative rather than simply answered. This is why I always try to provide some justification for my statements. There is nothing quite as valuable as the discovery that one is wrong and others cannot make useful judgments regarding my views without the context/rationale. One can also be right, but for the wrong reasons and this often leads one far down the path of error.


Quote:
Originally Posted by Damocles View Post
No way did I ever come away from any of your posts with that impression, Normk!

On the contrary, your posts appear ISSUE-driven; never EGO-driven!

Hope mine are the same; I may sometimes repeat your points; in effect, corroborating them. Further, I hope I always express any alternate perspective respectfully.
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