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13 mm master cylinders.....how much improvement ?

Discussion in 'Norton Commando Motorcycles (Classic)' started by jsnorton, Jun 8, 2019.

  1. swooshdave

    swooshdave

    Joined:
    Apr 15, 2009
    Something else might be wrong. What pads are you using? Do you still have the chrome on the disk?
     
  2. xbacksideslider

    xbacksideslider VIP MEMBER

    Joined:
    Aug 19, 2010
    Diameter of disc, thickness, and swept area, these add up to rate of heat absorption and heat dispersion - these are why big thin rotors with narrow pads squeezed by four or six pistons are what you see on late model bikes
     
    norton73 likes this.
  3. Adam M

    Adam M

    Joined:
    Mar 16, 2019
    I believe mine are 41 mm diameter ( typical cast iron Lockheed caliper ).
    What is diameter of Norton pistons ?
     
  4. cliffa

    cliffa

    Joined:
    May 26, 2013
    They are 44.5 mm.

    I have a 13mm RGM M/C conversion and to be honest I'm not overly impressed with the brake. I'd go for an 11 or 12mm for town use, but like Jim said earlier those pads are tiny by today's standards, so for hard or mountain work upgrade the whole shebang.

    Cheers,

    cliffa.
     
  5. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    Yes that can be a lifesaver. While learning to ride I read up on braking methods in several new rider guides. One rec was to only use two or three fingers, not a fist full. Another was to gradually apply pressure to maximum over a "One Steamboat" count. I had occasion to use this other than on practise lots when in my first year riding. An oncoming left turning pickup truck didn't see me coming straight through. Had maybe fifty feet to stop from 40 mph. This was on my modern bonneville and I fully believe the one second build up to max front brake kept me from loosing the front and stopped me with three feet to spare.
     
  6. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    Do the crossdrilled slotted rotors make much difference to cooling and stopping performance on our Commandos?
     
  7. SteveA

    SteveA VIP MEMBER

    Joined:
    Dec 20, 2011
    Learn't my braking techniques over 40 years on two and four wheels, road in all weathers including snow, including 1100/1200 tourers 2 up in the Alps/Pyrenees, road race, rallying on tarmac, gravel and snow/ice! With the latter you can throw in hydraulic handbrakes and bias pedal boxes to deliberatley defeat grip! And then be surprised how this new skill translates back to the bike.

    I don't rely on counting because 'gradual application' varies with different vehicles, surfaces and speeds. You need good 'natural sensors', unfortunately these do degrade with age!

    Biggest influence for me was Jackie Stewart's Formula Finesse! Comes in handy when you want to move on a bit faster without your wife being thrown around and complaining!

    The hardest thing for me to learn was how to really use an ABS system properly, going against all previously learnt ideas, still happier without!

    One benefit of really careful brake application seems to be I use pad materials at about half the rate of most others, but without relying on the gearbox for braking!
     
    Tornado likes this.
  8. SteveA

    SteveA VIP MEMBER

    Joined:
    Dec 20, 2011

    It depends! Some of the best rotor materials are iron, delivering a higher coefficient of friction. But generally more fragile. You don't want to drill or slot these too much for integrity reasons.

    Steel rotors have improved materials now, and tolerate more drilling and slotting, have improved friction figures and cope with more abuse from high friction pads. So the real issue of materials is that a steel disc can tolerate a higher friction sintered braking material with less resultant wear to the disc than is the case with cast iron. Some pads are designed to lay a coating on the disc surface and won't give best braking until fully coated! Continually swapping pad materials for comparisons can therefore be confusing!

    Better stopping with floating discs really comes from the ability to use more aggressive pad materials, not really the 'float' itself. Floating discs are designed to allow radial expansion of the pad track and thereby reduce the risk of distortion, so they warp less with your high friction pads.

    A certain amount of drilling and slotting can clear water quicker and will tend to maintain a fresher pad friction surface with a bit less glazing. Logically they also dissipate heat quicker through more surface area, but that is difficult to fully evaluate in normal (or even abnormal) use. And at some point there is a trade with swept pad area!

    So to recap.....floating discs are designed to allow radial expansion of the pad track without distortion, so they warp less with your high friction pads. Better stopping really comes from the ability to use more aggressive pad materials, not really the 'float' itself. I did use a set of floating 'wavey' discs on my GSR750 track bike and they were great, much better than the standard disc for both stopping power and feel, but hard to say if the main benefit was derived from the pad track design or the improved materials! I think they were a good material and worked well with the Bendix race pads. It also has to be said that on this bike the Brembo radial master cylinder was an essential part of the package that brought it all together.

    But I have turned a floating disc into a pretty good impression of a clutch diaphragm spring! So it is no guarantee. You will know you have done this from the increased lever travel when you have confirmed there is no air in the system but the lever travel is still excessive. Analysis showed the cause to be sticky caliper pistons in the 6 pot calipers holding the pad on the disc surface, the cure also included rebuilt calipers with fresh seals.

    So yes, modern material floating wavey discs with loads of holes and slots used with the correct master cylinder and pad choice for your planned riding can make an excellent brake!

    But an original (plating free) cast disc with a soft organic pad can work well for most uses if you sort the master cylinder bore/caliper piston area ratio to your preference, not everybody likes the same and your own physique will affect your preference.

    But as I think Comnoz pointed out really clearly, things vary a lot depending on the use you put it to.

    And more of it is cosmetic than people like to admit!
     
    Last edited: Jun 10, 2019
  9. illf8ed

    illf8ed

    Joined:
    Dec 30, 2003
    I don’t think anything is wrong. Just saying the stock brake cylinder was pretty good on my bike and I don’t see much improvement with the 13mm. Ferodo pads and the disc was skimmed removing the chrome.
    I don’t think anything is wrong. Just saying the original master cylinder was good and I don’t really find the 13mm to be better. Standard Norton OEM pads and skimmed rotor to remove the chrome.
     
  10. worntorn

    worntorn

    Joined:
    Dec 22, 2006

    Same experience here but with stock MC and large carpenter hands.
    On the third switchback coming down Duffy Lake road the brake was overheated to the point that I nearly went over a cliff.
    The first two were 70mph to 20 mph pulldowns maybe a mile apart, so that's where the heat came from.

    I went home and bought the complete Madass setup, big disc, six piston caliper and his custom fork leg.
    It was around $650 US if I recall.
    It's all the brake you could want, no need for twin discs for the road.
    I'll bet the pad area is four times that of those tiny stock Lockheed silver dollar sized pads.

    Glen
     
  11. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    What pads were you running when it heat faded Glenn? Hope not the Fedoro Platinums....these seem pretty good on my bike but have not done excessive heat ups like you...just the local ski hills and I rarely do up to 70 mph with heavy braking cycles.
     
  12. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Yes , the good Ferodos from Vintage brake.
    The proprietor at Vintage Brake said these pads would make the Lockheed brake so strong that it would be " scary".
    It was scary alright, but not due to any great strength.
    As Comnoz said, you have to ride fairly aggressively to overwhelm the stock brake, but when you do, it goes almost to zero brake right now. Not good with a corner and thousand foot drop coming up!

    Glen
     
    Tornado likes this.
  13. Onder

    Onder

    Joined:
    May 11, 2010
    Makes you wonder if the caliper should be the first thing replaced not the master.
     
  14. JimC

    JimC

    Joined:
    Oct 12, 2007

    Unless you changed to a caliper with a larger piston diameter the brake stopping force will remain unchanged. It’s all about the ratio of caliper piston area to master cylinder area. The optimum ratio being 27:1. Keeping the stock ⅝” piston diameter master and going to a 41 mm, 4 piston caliper will get you a ratio of nearly 27:1.

    It’s been reported the piston diameter of a stock Norton caliper is 44 mm. The Lockheed caliper has 41 mm pistons. Changing only the caliper to a Lockheed will get you a brake with less stopping force. No doubt the resistance to fade will be greater.

    This brake business is not some black art, it’s all about elemental physics.
     
    Last edited: Jun 11, 2019
    jsnorton likes this.
  15. jsnorton

    jsnorton

    Joined:
    Oct 10, 2018
    I used EBC FA27 pads when I replaced my front pads. They are not bedded in yet as I only made a very short run with them (1/4 mile) I did e-mail Donald Pender (madass) and his resleeve kit is 1/2". So it would seem to produce more pressure than a 13mm bore. He also said I should provide my own brake hose.

    Does anyone have a recommendation where to get SS braided hose from , with the Norton ends on it ? I will check out all links.
    Thank you
     
  16. Dellis

    Dellis VIP MEMBER

    Joined:
    Jul 22, 2018
    My bike had an RGM 32Omm disc with a Grimeca caliper when I bought it, the front brake was so bad I was moderating my riding and decided to move to a 13mm AN m/c the difference is amazing and as I've posted elsewhere the change is from squeeze and hope to squeeze and stop. I would expect similar improvements irrespective of the disc/caliper you have.

    Dave
     
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  17. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    I would never try to get a chrome-plated disc to work efficiently . It might be a waste of time and effort. I would also never use cast iron for a disc on the front of my bike, even though the coefficient of friction might be better. There are plenty of high-speed steel disc available which have alloying elements in them which make them strong, and the coefficient of friction is usually more than adequate, especially when you use two of them. I do not believe in drilling discs. When you grab a handful of brake, you need to know the discs will not break.
    You need to get your heads in the right place. The front brake on your bike is much more important than any motor improvement. If it goes wrong, you will probably become dead.
     
    jsnorton likes this.
  18. Craig

    Craig VIP MEMBER

    Joined:
    Dec 20, 2005
    Yesterday while at car dealer getting my tires road force balanced , an older gent was picking up his car after a big service ... the nice lady serving him asked for $900 plus ,Yikes , anyway she mentioned his brake pads were as new and car had almost 60000kms on it , she wanted to know if he had them replaced elsewhere , he replied no they were original and he routinely got 160000kms from a set because he used his brakes the right way ! ... I can usually get 100000 on a set , guess I’m just not as good a braker as this gentleman .... all about smooth riding, eh
     
    jsnorton likes this.
  19. phippsy

    phippsy

    Joined:
    Dec 28, 2013
    I had a racing Lockheed caliper bought from RGM that had 44mm pistons with 13mm master cylinder and RGM floating disc sure did stop
     
  20. SteveA

    SteveA VIP MEMBER

    Joined:
    Dec 20, 2011

    I don't know which caliper you had but.....the CP2195 and CP2696 AP Lockheed 'race' calipers have 41mm pistons! But that will work well with a 13mm master cylinder bore.
     

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