Honda PCX (150) Linked Brakes

[Jge64]

Hey , you can write a Bible as far as I'm concerned, all I'm saying is you lose people if it's this long. A few pictures interspersed would probably keep people more attentive, than straight text. But hey have at it, i'm sure another engineering type person probably loves it. it's a public forum, you can write as long as you wish.

What's interesting is a DIY or "how to" is almost the opposite, the longer and more complete it is , the more hits it gets.

[Alibally]

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.

. It's a scooter.

[silverantec]

I have a genuine request to ask of any PCX owner who is also a Actual Mechanic, or is actually very mechanically capable and who also has a correct tool for what I am asking. I would be interested in genuine feedback from one or more aforesaid competent people to fit a actual proper brake hose clamp (NOT VICEGRIPS) to the front brake hose that operates the middle caliper piston and then to walk or run beside their scooter and operate the left brake lever. (If you do not know nor have the proper tool please ignore this post)

You may also at your discretion actually ride your scooter on your driveway or any other place with a good concrete or road type surface (Not on a public road or with any traffic) and increase your effort on the Left brake lever until you have achieved maximum rear wheel braking effort. I then wish to know your opinion on whether you consider the rear brake effort to be strong; capable (or not) of locking up the rear wheel; Of knowing the circumstances you did this test; (dry surface obviously) but walking, running beside or riding.

This is non harmful to your scooter, Not something I would ask of nor expect any non competent person in this field to attempt. But prior to my personally disassembling my rear brakes I would appreciate the opinion of others regarding this test to determine whether or not I might get my dealership involved with my own circumstances because I am more than a little surprised at the sheer lack of braking my rear wheel offers me. I have no problem of course just pulling my wheel off, but to this point since I have not touched inside I cannot be accused of interfering in there & I am genuinely wondering do they have something over here that maybe they should be looking into, not just for myself but maybe on others too.

Should I enter into the brakes and find nothing faulty or improperly cleaned prior to assembly I already have plans in place to improve my own brake, but to help others best I would need to involve the dealership before I further go my own way to resolve my issue. So what say you all out there. Anyone interested in doing this and passing me their evaluation of their own test here.

[gn2]

Or you could just unbolt the front caliper and ziptie it up out the way.

[chicaboo]

I found out today that I can lockup my rear drum brake on bitumen/tarmac/asphalt or whatever you call it in your part of the world.
It didn't take a ridiculous amount of effort, but a fair effort, and it didn't matter if I was going uphill, downhill or on a flat road.
I tried 3 or 4 times just to learn the limits of my braking for if I ever need it for an emergency situation.

[homie]

I found out today that I can lockup my rear drum brake on bitumen/tarmac/asphalt or whatever you call it in your part of the world.

bitumen... now I learned a new word wait... was Dudley Moore being a racist in Arthur?

language warning

https://www.youtube.com/watch?v=lOCW9Sh ... ftAQRl85Gs

[chicaboo]

I found out today that I can lockup my rear drum brake on bitumen/tarmac/asphalt or whatever you call it in your part of the world.

bitumen... now I learned a new word

I amuse myself now imagining how you would pronounce that.

[iceman]

bit 'chu' men is how most UK peeps pronounce it. Not tar (which is natural) bitumen is man made but similar

[silverantec]

gn2: quote: Or you could just unbolt the front caliper and ziptie it up out the way.

There are At least 3 good reasons why no person should do this.

1/ It mechanically & dangerously interferes with your scooter.
2/ It is Dangerous if you attempt to ride with absolutely no front brake.
3/ It is a radical interference to your scooter and with no disc between your brake pads should you do this and remove the caliper you may well blow your pistons out and run brake fluid everywhere no matter which brake lever you touch. And with pressure to attempt to use the rear brakes you will pump the center piston out and the left lever will pull all the way to the handlebars because you caused an imbalance to the Joint operating T junction of master cylinder and rear cable.

Please note; the use of a hose clamp as I suggested is non harmful; no physical interference to a scooter; takes about 3 seconds once the tool is in your hand, and you still have full front brake function with use of the right lever, and full rear brake function with use of your left lever.

chicaboo I appreciate your feed back. My own rear brake barely slows me down as if I have lots of brake fluid (or something else) on the linings. Worse after the first one or 2 brake applications. Obviously I find it hard to suspect the dealership or manufacturer left any coating that could do this, and since it is no better or worse since the rear wheel was replaced I do not know what I will find but I will have to pull mine apart now to see why mine are so poor.

I will let you all know what I find if anything but as something with much higher priority has suddenly arisen I am sorry be it will be a month or so before I can deal with mine any further.

[gn2]

The caliper would only be zip-tied up to conduct your walking beside the scooter with the rear brake on test

[homie]

The caliper would only be zip-tied up to conduct your walking beside the scooter with the rear brake on test

thank you, at a glance I was thinking this thread needed to be moved to 'crack pipe'

[you you]

The caliper would only be zip-tied up to conduct your walking beside the scooter with the rear brake on test

thank you, at a glance I was thinking this thread needed to be moved to 'crack pipe'

Someone's on crack or whatever it's called in Australia

[JohnL]

We have a lot of Tradie's crack in Oz.

[alx123]

I'm actually lost. What are we discussing here?

[you you]

We have a lot of Tradie's crack in Oz.

In the U.K too. Some where to park your bicycle.

[you you]

I'm actually lost. What are we discussing here?

GPS if you'd like?

[foggyhelmet]

1stly my search showed nothing on this so forgive me if I missed it.
I have a 150 pcx and have done a few changes to it which necessitated removal of all the body panels. (This may be subject of another later post).
I have separated the Linked Brake System. My right brake lever now operates only the front brake using all pistons in it and my left brake lever now operates only the rear brake.

I would like to advise all pcx riders that I have discovered something I did not know from my test ride in which I thought the brakes were quite ok. The rear brakes are beyond pathetic. I was amazed at how useless it is. You can squeeze the lever until it is against the handlebar and all you do is slow down gently.

Walking beside the bike engine off pushing it and squeeze hard you cannot lock up the rear wheel. My scooter is less than 12 months old with 3000 klm on it. I had to have the rear wheel replaced as a warranty item as it was warped in the drum causing uneven (jerky) braking. I did not test ride it, just picked it up. When I got home I rang them and it took a lot of pressure from me to make them rectify the fault but they did. So I have not myself interfered with the rear wheel or brake.

I separated the linked brakes because I do not like someone else determining how much braking I am using on corners or wet roads. I assumed they would have tried to work it out to be a reasonable ratio but I was so wrong. You think with the linked brakes when you use the left lever the rear wheel should be doing most of the work and you add a little more pressure when you use the right lever. WRONG.

The rear brake was doing almost nothing. With the right lever I was just letting the front brake work harder thinking I was balancing the use for stability. My warning to other is Your Front Brake is basically doing all the work so be careful of how you use brakes on corners and wet roads or loose road surfaces.

I love the scooter & do not mean to bag it but if you cannot lock up the rear wheel when you have separated them as I have then there is no way you can get maximum braking effort when you need it. Normal motorbikes never seem to have this problem (with rear drum). I have ridden a few. They lock up ok when asked to. You cannot alter the adjustment as you must squeeze the lever a certain amount to start the engine but you can tell that as you squeeze the lever harder it gives no added braking. It just has nothing more to give in standard setup.

At 1000 klm I assumed maybe I still need to bed the linings in more as I am a gentle rider and think ahead to minimize brake use. The front brakes by the way are fine. I feel no need for a bigger disc or any other change. I use the scooter for both local and long distance and refuse to exceed 90 kph preferring 80 to 85 as my cruising speeds. It would be a costly exercise to fit a rear disc & caliper but is looking like my only option if I want to have maximum braking for that emergency one day. I post this only as a warning to others. Please take care on wet/slippery cornering.

I slip on gravel regularly. Wiped out on a highway once pulling over for a safety check.

It RIDES on dirt and gravel well for it's build, but stopping, you better have a huge pile of gravel to drive into or you will go skimming.

[Rick54]

As a person new to scooters and looking into the purchase of a 2017 PCX150, and one who knows nothing regarding the braking system to which you are all referring to, I'd like to ask the consensus of the group. Being a person new to scooters, is there a genuine concern with the braking system on the 2017 PCX that I should be concerned with?

[iceman]

No - just ride properly and don't take risks. Most of the so called accidents are when there is nothing you could do and someone goes into you or people not riding properly - going to fast for road conditions, too fast into bends or taking corners, going too hard and relying too much on the front brake and not using it in conjunction with the rear (cbs), or tilting over too much when not needed (even sharp bends do not need you to scrape any metal part of the bike on the road as some people discribe!)

Slow down gradually and use engine braking when you can - then start pressing harder on rear and front brakes.

[gn2]

is there a genuine concern with the braking system on the 2017 PCX that I should be concerned with?

Absolutely not.
The CBS braking system on the PCX is specifically deigned with new riders and safety in mind.
The criticism of the linked brakes comes from people who are used to separate brakes on conventional motorcycles.
For the intended usage of a PCX the CBS system is bloody brilliant and anyone who says otherwise is simply wrong.