Honda PCX (150) Linked Brakes

[silverantec]

gn2: (quote: I know what I know. Two master cylinders are better than one.) I am sorry, but you may have to explain that one to me.

Oh and on the insurance side of things; it is no problem advising them as, the requirement here is that the brakes meet the legal requirements. CBS is not a legal requirement, it is like having a rear windscreen wiper on a vehicle; nice but not necessary for the law, & not illegal to remove it or make it inactive. And as I said in a earlier reply, CBS is not ABS so safety has not actually been compromised. You always had the choice to adjust your front/rear braking with the 2 levers. I have only given myself total control of the balance used with the brake effort available from each.

[gn2]

You have reduced the amount of force which can be applied to the front brake by removing the CBS master cylinder.

Legislation varies, what may be ok in your country may not be ok elsewhere.

[silverantec]

n2: (quote;You have reduced the amount of force which can be applied to the front brake by removing the CBS master cylinder.)

Quote from myself at the top of page 2 of this thread: (I have done as Oyabun indicated and fitted a short braided hose and banjos linking all pistons.) My right brake lever operates all 3 pistons. Do you still hold to the statement in your last reply. Perhaps you missed it where I originally posted this fact of how they are all 3 pistons connected and operating, with marvelous feel and control I might add. I have no sense of a need for a larger disc or any front brake change.

The quote from Oyabun:(A short brake hose with banjos could be an option)Bottom of page 1 this thread.

Also I have not encouraged others to repeat what I have done. Should they do that it is their choice & I would expect they would check the laws in their country, as I did in mine. Good of you to offer them that caution however.

alx123:(quote: I stopped reading at " i have 1000 years of experience as a mechanic so I am the smartest guy here.") Also included here is Alibally(+1.) & honkerman (Precisely. Even mechanics with years of experience can still have a bad day.) Maybe you guys were reading a different thread. It was 40 year not 1000; I checked. So make a suggestion to me now. Is it better a person states his qualifications so a reader can believe that person has some credibility as to what he is talking about, or would you prefer I had said "I know nothing about anything mechanical but here is my opinion which you should read because I ride a bike which makes me credible to heed my advise? I personally am happy to read the opinion of another but if it is on something important I like to know what credentials they have to back it up with. Also I am the only person on this thread to have offered my credentials unlike those who criticize me for having offered a warning for the safety of others.

[silverantec]

One last suggestion for the brave and sure of them self who might like to prove me wrong in my advice in the opening post of this thread. There is a simple way you can prove me wrong. Have a friend take a video of you on your scooter on something like a grassy or wet grassy surface. Travel with enough pace to use only your left brake until you lock up one wheel. If I am wrong and Honda has a good balanced brake system your rear wheel should lock up first, and any good rider will be fine with that. But if I am correct it will be your front wheel that locks up first. Have fun with that. Post the video on you tube and put a link to it here. If my advice was poor I will apologize for bothering to offer it. It is a fair test as the wheel grip will be equal as it would be on a good gripping surface but you will have a softer landing.

[honkerman]

One last suggestion for the brave and sure of them self who might like to prove me wrong in my advice in the opening post of this thread. There is a simple way you can prove me wrong. Have a friend take a video of you on your scooter on something like a grassy or wet grassy surface. Travel with enough pace to use only your left brake until you lock up one wheel. If I am wrong and Honda has a good balanced brake system your rear wheel should lock up first, and any good rider will be fine with that. But if I am correct it will be your front wheel that locks up first. Have fun with that. Post the video on you tube and put a link to it here. If my advice was poor I will apologize for bothering to offer it. It is a fair test as the wheel grip will be equal as it would be on a good gripping surface but you will have a softer landing.

Right...so we're supposed to prove you wrong by going at a good clip on wet grass on street tires then try to lock the brakes. You sir are one for the history books. You're so intent on proving yourself right that you will put other people at risk of injury or damage to their own bikes. Winning isn't worth putting someone else at risk.

A really good rider would likely do fine, but what if there is a less experienced rider who tries this and gets seriously hurt? That would be on you.

[gn2]

One last suggestion for the brave and sure of them self who might like to prove me wrong

There's no need, you're managing fine on your own.

[Alibally]

I think this thread is going nowhere but around in circles. It's getting a bit boring now.

[silverantec]

Alibally you are correct sir. I am very sorry that a thread started by myself with good intentions to offer warning to the unwary has become a challenge of my integrity and professional knowledge by one or two or three with nothing but a mouth to back themselves up.(or fingers on a keyboard in this case.) Perhaps if they ceased from unsupported speculation or backed themselves with actual evidence they could be taken seriously but I reserve the right to answer any challenge personally against me. But I have offered them the challenge which they can do, or cease from useless babble. They are so sure I am wrong it should not be a problem to them. But they fear I am right so will never do it. So time to close this thread to all replies moderator, it is going nowhere from here but to personal challenge. I gave the warning I wished to with good intentions. Lets all leave it at that.

Please close off this thread to all replies.

[gn2]

My right brake lever operates all 3 pistons. Do you still hold to the statement in your last reply.

Yes, absolutely 100%
If you remove the CBS master cylinder (as you have done) the amount of force which can be imparted on the front brake caliper is reduced.

[WhiteNoise]

Not so fast silverantec. This is a Good thread! Maybe in the wrong condo (General vs Technical) but overlooking that, I'm enjoying the read, the knowledge within and all comments made.
I'm also proud of everyone involved for keeping this thread under control and humane. I applaud you.

There's nothing wrong with a member introducing his/her ideas to the rest of us. We're all grown ups (correct?), sooo...do what you want with the info provided. Use it, lose it, ignore it...whatever. I truly believe that member silver (can I call you silver? means no harm to anyone. Yes, I read the statement about experimenting on your own PCX, wet grass and all...but again - Ya'll know better, listen to what makes You tick. You make decisions everyday of your life. Do's and Don'ts. Don't mess with your CBS brakes or any brakes for that matter IF YOU don't want to.
It's as Simples as that.

I understand the point made about newbies reading all this and them thinking, "hmm, I'm going to try this. Yeah, I'm going solo on my brakes. I'm use to that anyway from other bikes and this guy's making some sense." "I'll do the test." (Might be a Whoopsie, but then might not).

Well,....if they're considering "the change," then so be it. They might just know something we don't from their own past experience's. (Benefit of the doubt given there). What can I, we say?
We're all dancing to the beat of a different drummer.

(Is it) All About That Bass?

@ silver, please please enter your location to your profile. I'm pretty sure you have noticed that the bulk of us have. I feel no need to direct you. You sir are a smart man. That Is a compliment
Thank you for joining our forums and for initiating an interesting and challenging (maybe dangerous?) modification.

Be Safe First and Always ~ Everyone ~
WN

[honkerman]

I truly believe that member silver (can I call you silver? means no harm to anyone. Yes, I read the statement about experimenting on your own PCX, wet grass and all...

Nah, I didn't think he was being malicious, just that he wasn't seeing the bigger picture with the fact that we have a lot of amateur mechanics and such and we with more experience and knowledge need to be aware.

Silver: May I suggest that if you want to see if that test would work, don't pull a Harry Reid and ask others to put themselves at risk to prove you wrong. Borrow (or purchase if you want), a stock PCX and do your proposed test. It would be interesting to see if you are correct or not, but I'd rather not see someone get hurt because of another's suggestion.

[honkerman]

My right brake lever operates all 3 pistons. Do you still hold to the statement in your last reply.

Yes, absolutely 100%
If you remove the CBS master cylinder (as you have done) the amount of force which can be imparted on the front brake caliper is reduced.

I see what you are saying. The primary master cylinder (the dinky teeny weeny one) is still exerting the same amount of force, but that force is now dispersed along three pistons instead of two. It seems logical that there would be a reduction in braking force, since that tiny little master cylinder was only designed to work the two larger pistons.

A simple solution would be to introduce a larger master cylinder capable of exerting a sufficient amount of force, something from say a CBR 250 or something of that nature.

It's also good to remember that even expert technicians with years upon years of experience are capable of making mistakes and we need to retain the humility to accept that possibility.

[chicaboo]

Two brake levers operating 3 pistons will exert more force than one brake lever operating the same three pistons.
The old adage "many hands make light work" applies here.

The right brake lever will still deliver the same effort, but will be now distributed over the three pistons without the potential benefit added from the left brake lever to supplement it. The braking feel may be enhanced for light to moderate braking applications, but the maximum braking effort will be diminished.

This difference may be addressed to some margin by using a braided brake line to the middle cylinder, but not entirely.
Or you can just squeeze harder... And when you do, you are asking more from the one master cylinder and putting more pressure on it every time.

[honkerman]

Oh little FYI, on my way in to work, I did lock up my rear wheel on the lawn while traversing it (accidentally, I kinda lost the sidewalk completely unplanned.) to get to my parking space under the fire escape. The grass was dry, but still, the back end locked. No video that would show this because I wasn't expecting it and didn't have any filming equipment set up. I was a bit surprised when it happened. Went back and looked at my face-cam vid and had to laugh at my reaction. I'll see if I can find a windows phone video editor to show you at least that much.

I did find a vid editor rather quickly, but it keeps freezing up, and I don't have my laptop with me here at work tonight.

[chicaboo]

Silverantec: Did you say the dealer did something with the rear wheel/drum brake before they delivered the bike?
Maybe they didn't clean/prep the drum surface in the hub correctly, and that's why your braking performance is off?
I know you shouldn't have to follow up on their work. But they really don't have as much vested interest as you do.
Is the rear brake actuator passing the wear indicator marked on the side of the transmission?

[alx123]

TS intention for starting this thread is noble but the way he defends his ideas are a lil off putting.

No need to close this thread, we just need to get it back right in track.

When my PCX came from the dealer, the rear brakes are a little loose. A little adjustment did the trick though.

Why want to lock up your rear in the first place? Isnt that what CBS supposed to do? Prevent lock up and instead put a little pressure on the front brake to avoid skidding? One can always adjust percentage distribution of the CBS, but I think the original setting is great. IMO

[silverantec]

First off for the benefit of everyone, the test it out on wet grass was more or less a tongue in cheek thing to one or two who seem to indicate I am full of it. It is not that I expect someone to do it. (but I would like to see the video if they do try it.) 2nd thing is that before I had separated my own brakes one end for each lever I had not been particularly aware that my rear brake was working very little compared to the front Brake. I only became aware because after separating them I discovered no amount of effort could lock up the rear wheel, but more significantly for me, it requires a lot of effort to get modest braking effort from the rear wheel.

Now only a fool would try to convince anyone that separating the brakes could in any way cause a reduced performance of the rear brake since leverage ratios do not change. But being well aware of how well the bike slowed with little left lever effort compared to once separated and realizing the rear brake now separated has fairly poor retardation effect with similar lever pressure applied it seemed only reasonable to encourage others to be aware of a risk that they too might actually be having the front wheel do most of the braking when they think they are "balancing" brake effort using the 2 levers. I used to have access to a decelerometer which would have been good to have now to put the braking effort into figures, but that might be a little difficult for me to now get hold of one. However I offered my opinion on the effort the rear wheel is giving based on my experience as a tester which it is a fact that my experience & professional training makes me a "professional" witness in a court. (Just like a doctor or surgeon is in medical matters.) And yes I have done that often enough too.

Now lets settle the matter of the front caliper with one master cylinder now doing the work. It has been established through this thread and is in the mechanics manual that the Left lever operated the center piston of the 3 in the front caliper, which is one of the two smaller pistons. (About 22 mm dia) (the larger piston is about 26 mm dia & that plus one 22 mm piston were operated by the right lever). Thanks to the picture offered by Oyabun near end of page 1 of this thread we can see that the larger piston is actually the "Trailing" piston when travelling forwards. (We might come back to this later)

So now I have 2 x 22 mm pistons and 1 x 26 mm piston operating from one master cylinder (MC for short huh). A MC produces hydraulic pressure equally throughout everything from the hose the fluid travels through to each piston to which it applies pressure. So if we had a Hydraulic fluid pressure gauge in the line and apply 100 lbs per square inch pressure (lbs=pounds in the old scale. we shall from here on refer to this as psi) then 100 psi (of fluid pressure)is being applied to each piston. The only thing that makes a difference is the diameter of each piston as to the force that each piston exerts on the brake pad. So lets pretend the the 2 smaller pistons are exactly 1 square inch surface area. And the Larger piston is 1/4 surface area larger.

With 100 psi fluid pressure the 2 smaller pistons are applying 100 lbs of force each. The larger piston is applying 125 lbs of force. Why? because the extra 1/4 of surface area converts an extra 1/4 of the 100 psi of fluid pressure to direct pushing force on the brake pads.If you have with your CBS intact 2 master cylinders, or 5 or ten master cylinders each applying 100 psi then throughout each brake line you still only have 100 psi of fluid pressure to convert into pushing force. More fluid pressure = greater piston pushing force. But more master cylinders each applying 100 psi to the fluid for separate pistons does not equal more fluid psi to convert to pushing force. The only thing that will give greater piston pushing force when maximum fluid pressure has been achieved is larger caliper pistons to convert the available fluid pressure into physical pushing force. (Fluid force x area = applied force. Doubling the MC pistons applying the same force does not increase the applied force.) (Double the surface area to which the force is being applied doubles the applied mechanical force.)

gn2 this was all for you and anyone else who might agree with you. As this is basic mechanics of which I respectfully offered my qualifications in by, all means if you still disagree please offer to assist me in re-writing all the engineering books. Look mate I am not trying to be offensive but as I said; basic mechanics.

honkerman: (Quote: I see what you are saying. The primary master cylinder (the dinky teeny weeny one) is still exerting the same amount of force, but that force is now dispersed along three pistons instead of two. It seems logical that there would be a reduction in braking force, since that tiny little master cylinder was only designed to work the two larger pistons.
A simple solution would be to introduce a larger master cylinder capable of exerting a sufficient amount of force, something from say a CBR 250 or something of that nature.
It's also good to remember that even expert technicians with years upon years of experience are capable of making mistakes and we need to retain the humility to accept that possibility.)

You really give me a good laugh here mate. To go one step further for you beyond the above explanation, if you double the diameter of the master cylinder piston but it takes the maximum strength of the average hand to apply the said 100 psi then all other things being equal you will move double the fluid volume movement in the stroke of the MC piston however you will halve the applied fluid pressure. You will effectively now have 50 psi for fluid pressure on the same surface areas and halve the caliper pistons applied force. Fluid movement volume is not the
issue. All the pistons move only a few thousandths of an inch. Less than the thickness of a razor blade. My right brake lever has no appreciable additional travel with my setup over the standard setup. I have also fitted (certified) SS braided brake hoses. 100 psi is 100 psi is 100 psi. It matters not the source nor the number of sources. Is having a sound knowledge of hydraulics and mechanical principals, applying it on my own things, and offering a warning when I see a potential danger to the unwary and the trusting (in everything being golden as produced by a manufacturer), the act of a non humble person. Do you tell your doctor to be more humble when you go to him or your dentist because they know something and practice something that you yourself are not qualified to do.

You and gn2 should now either refute what I have herein explained or consider an apology for {gn2: Yes, absolutely 100% If you remove the CBS master cylinder (as you have done) the amount of force which can be imparted on the front brake caliper is reduced.} & for {honkerman: I see what you are saying. The primary master cylinder (the dinky teeny weeny one) is still exerting the same amount of force, but that force is now dispersed along three pistons instead of two. It seems logical that there would be a reduction in braking force, since that tiny little master cylinder was only designed to work the two larger pistons. A simple solution would be to introduce a larger master cylinder capable of exerting a sufficient amount of force, something from say a CBR 250 or something of that nature.
It's also good to remember that even expert technicians with years upon years of experience are capable of making mistakes and we need to retain the humility to accept that possibility.
You are fast enough to apply "what you feel" as fact; now that I have applied the facts are you as fast to offer the apology. I am sorry that the application of correct hydraulic and mechanical principals and the good intent behind offering warning to the unaware of a potential for risk is evidence of my lack of humility.

Coming back to the Trailing Larger piston: As shown in my examples: The larger piston with the same psi behind it produces greater pushing effort. This also translates to being the first piston to move when pressure is applied. As in my example the additional 25lbs force with 100 psi fluid pressure is more than enough to ensure the trailing edge of the pad makes first contact with the disc. Not important but just helps ensure the leading edge is not so inclined to want to bite into any holes, grooves or disc wave edges. I can think of no other particular reason for it as most calipers I have come into contact with have tended to have equal diameter pistons, but feel free to correct me if there is another reason offered by the manufacturer.

chicaboo: When I rode my scooter out of the dealership the first lights I stopped at 100 mts up the road I experienced rear brake warp, jerky uneven braking. I thought new bike and all I am being overly sensitive. But sadly it was warped giving jerky uneven braking each time I applied the left brake lever. I made a special point of testing it on very smooth roads with no traffic then contacted the dealership after I got home. Over the next month they tried to say it would sort itself out if I keep riding it and half a dozen other things.(like it will wear in. Have you ever had a car with disc warp vibrations "wear in" again. That would be nice and save people lots of money machining or replacing discs). The service manager when I contacted him said straight away that he would order another wheel but I suspect someone higher up over rode him and hoped I would just go away. I actually had to contact a solicitor, the office of fair trading and Honda Australia where I informed them that in the event of my ever having an accident where anything to do with braking could be considered the cause of the accident I would lay it all at their feet and sue them. They had a new wheel within a week or two from then. It would be nice to be able to think that cleaning something would improve it but with both wheels the only difference after wheel replacement was I no longer had jerky uneven braking.

And chicaboo: (quote: Two brake levers operating 3 pistons will exert more force than one brake lever operating the same three pistons. The old adage "many hands make light work" applies here.) The right brake lever will still deliver the same effort, but will be now distributed over the three pistons without the potential benefit added from the left brake lever to supplement it. The braking feel may be enhanced for light to moderate braking applications, but the maximum braking effort will be diminished.
This difference may be addressed to some margin by using a braided brake line to the middle cylinder, but not entirely.
Or you can just squeeze harder... And when you do, you are asking more from the one master cylinder and putting more pressure on it every time.)
Let me ask you this simple question; When you stand on scales are you lighter or heavier when you stand on both feet instead of with one foot.
Now I have already stated my use of SS braided hoses. Do you too in light of the explanations or plain and correct hydraulic & mechanical principals wish to stick with these statements you have made. Or do you as the others before you should, feel that some sort of correction or acknowledgement of your error should now be proffered.

Look I am actually glad everyone is very happy with their PCX's. Really. But does that make me a bad person for having concern and offering the warning. The fact that I unlinked my brakes has only affected my ability to control the bias of braking (for the better for me) exactly as I see fit with the exact knowledge of the effort each wheel is delivering. Neither is giving greater or lesser performance in my setup than they did with the CBS operational. But with the CBS no individual is definitively aware of the effort their own brakes is giving but has the blind assumption that all is good. For a concerned individual knowledge is power to control their own safety. And as I have more than once pointed out the PCX is a great scooter. So great that I like to do trips of many hours and a few hundred kilometers at a time. (I just have to make the seat better but am working on that. Despite being softer now I realize I need more seat area) But for city stuff 1/2 hour or so at a time it is awesome.

And WhiteNoise, you sir may call me anything but Late for Dinner. Thank you for your understanding of what I was trying to offer. Also since all changes done to the scooter have been performed by professionals, myself and various others who had input with their trades, and all parts are either certified (hoses) or of quality, the end product is no less safe than any other motor bike or scooter with independent front/rear brakes. As I have said more than once this is not an ABS that has been altered. And even with CBS a rider has front and rear separate control at their fingertips just as I have. The only difference is, "I know how much braking effort is performed by each wheel when I use my two brake levers". With CBS each person is exerting individual control to 2 levers with no true knowledge of the exact retardation effort each wheel (brake) is giving them, and a "she'll be right mate" hope that it is as balanced as they like to think it is. Good luck with that. Let no one say I have made my brakes better as I do not say that; I have just taken back the individual control which I am qualified to do and is not against our laws.

[honkerman]

For someone who accuses other people of being keyboard warriors, you type an awful lot. I got bored after the first paragraph and am moving on to other things.

[JohnL]

I'm thinking of taking up reading "War & Peace" for some light entertainment.

[gn2]

silverantec, I have read your explanation carefully and have made enquiries among family members who really understand physics and it turns out I was completely mistaken and you sir are correct.
I apologise unreservedly, I was just plain wrong.