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EBC GPFAX

Discussion in 'Norton Commando Motorcycles (Classic)' started by storm42, May 26, 2018.

  1. storm42

    storm42 VIP MEMBER

    Joined:
    Jul 20, 2011
    HI Guys,
    I have lurked and learned from this site for a few years now but now have a question.

    Has anyone tried the EBC GPFAX pads? I have built a Mkll Seeley 920 and fitted twin RGM discs with AP Lockheed callipers fitted with the GPFAX pads.

    I ride quite a few different bikes with different brakes including my ZRX1200 turbo with radial brembos, but I have never ridden a bike with brakes as powerful as the setup on the Seeley, in fact they are too powerful.

    I was at Donnington a couple of weeks ago and the power of the brakes was a problem, my first thought was to bin the pads and go back to HH but i am now thinking of removing one of the discs and saving the unsprung weight.

    The bike is used for track days and its next outing is at Spa, any thoughts on single disc with pads that would have stopped the Titanic or twin discs with more reasonable pads?

    Obviously i would be changing the master cylinder as well.

    Thanks for any help.
     
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  2. kommando

    kommando

    Joined:
    May 7, 2005
    The problem will be the pull on one side only, why not go for a bigger cylinder but keep the twin discs using the lower applied force to ease off the pad efficiency.
     
  3. storm42

    storm42 VIP MEMBER

    Joined:
    Jul 20, 2011
    Do single discs cause that much of an imbalance that it becomes a problem?

    The brake feels a bit wooden with the current master cylinder and that wasn't helping with the feel, couple that with the power and braking was an adventure.
     
  4. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    A larger mcylinder will make the brakes less powerful but will feel more wooden,
    Why not just blank off one of your callipers and give it a try?
    You will get a hell of a lot less braking and you will be able to judge whether the inbalance is affecting your forks ,
    I don't notice flexing on standard commando forks or a standard t140 bonnie or trident but I have noticed flex on a cb750 honda with a single disc
    Fork braces have been about for a long time now when the real culprit is the axle diameter and location in my opinion
     
  5. o0norton0o

    o0norton0o

    Joined:
    Apr 27, 2015
    In the past I was part of a dirt oval race car crew. We would grind material off the brake pads to be able to change the braking power on the outside wheels so the car would "set itself" slightly sideways under braking going into the turns. The driver could then mash the throttle to power in the direction in which the car had been set, powering through the turn.

    In your case, you could remove pad material surface area (I don't mean pad thickness) to reduce the contact area which weakens the power of the brakes. Of course you don't get the benefit of less unsprung weight that removing one of your discs and calipers would give you, but removing pad surface area is a cheap way to weaken your braking power. All you sacrifice is the cost of a pair of brake pads.

    Bare in mind that in some racing (probably not motorcycle racing, but I don't actually know) they don't allow a car to use a hydraulic proportioning valve to adjust braking power away from certain wheels and towards others, so cutting the pads is a way to proportion braking power and staying within the rules.
     
  6. Torontonian

    Torontonian

    Joined:
    Dec 28, 2009
    Too powerful brakes ? That's a new one on us. I use one of these front brakes and it's just fine for stopping power , the lever was my issue and had to change it as it was made for riders with huge hands. Good luck.
     
  7. oldbeezer

    oldbeezer VIP MEMBER

    Joined:
    Nov 2, 2017
    Please excuse the question as my understanding of physics is somewhat limited. But in reference to reducing the brake pad area to reduce the stopping power does not make sense to me. I would like to describe what I am trying to understand. I will use numbers of convenience rather than real world numbers, please bear with me. Lets say you have a brake pad with an area of 10 square inches and apply 10 pounds of pressure to it, that would result in 1 lb per square inch would it not. If you cut the pad in half to 5 square inches and apply 10 pounds to it the result would be 2 lbs per square inch which would give the same stopping force? Hopefully you can show me where I don't "get it"
     
  8. o0norton0o

    o0norton0o

    Joined:
    Apr 27, 2015
    the lever's pressure would be different to apply the same force to the calipers with the pads having 2 different surface areas. It might take twice the lever pressure to generate the same stopping force to the half sized pad. The feel of the brake lever might feel "less wooden" as it was discribed above because the ratio of lever pressure and caliper pressure has changed. I would bet that reducing the surface area of the pad would help the lever feel greatly, allowing more sensitivity rather than "all on" or "off" feel.

    I think his best bet is to remove a caliper and a disc to lighten his front wheel's unsprung weight so he gets better controlled braking and better performance from his front suspension too... There's some nice stuff out there... Don Pender makes a nice brake kit upgrade and I think CNW has one too that is lighter and better engineered than the stock stuff...
     
    Last edited: May 26, 2018
  9. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    The cNw kit is a great brake.

    There’s less initial bite than some brakes, but loads of feel and plenty of stopping power when you squeeze it.

    For the track, I fitted track pads that improved it further still.

    It’s a well made and light set up that works exceedingly well.
     
  10. storm42

    storm42 VIP MEMBER

    Joined:
    Jul 20, 2011
    Hmm, I think the problem with just blanking a calliper off would be an even greater lack of feel, I believe that a single calliper would require a master cylinder with a bore of about 11mm.

    Without matching the master to the calliper it would be difficult to evaluate the effectiveness of the brake.

    I also have a T140 and also don't notice any flexing, nor do i remember any with the standard brake on my Commando (but it has been a long time since that was on the bike) I also didn't notice any flex on the T160 that I swapped for the engine that is in the Seeley, but and it is a big but, non of those brakes had the power of the Seeley brakes with those pads in.

    I agree about the axle though.
     
  11. storm42

    storm42 VIP MEMBER

    Joined:
    Jul 20, 2011

    AN interesting insight into the oval race car world, but I could just change the pads to less effective ones and probably sort it out that way. I think I was hoping someone had tried the GPFAX pads and give me an indication as to wether or not a correctly set up single disc with these pads would be OK, I think the weight saving would be very noticeable, I am just not sure if the single disc would be acceptable for track use.

    I know I am asking a question that would be difficult for anyone to answer, especially as I haven't mentioned that I am using Ceriani GP35 forks on the Seeley. I suppose I should try and post some pics of the beast.
     
  12. storm42

    storm42 VIP MEMBER

    Joined:
    Jul 20, 2011

    I know, its a bit of an alien question for Norton owners :) and because I had to space the master cylinder out to fit the clip-ons the lever is a bit of a stretch, I am trying to sort that now.
     
  13. storm42

    storm42 VIP MEMBER

    Joined:
    Jul 20, 2011

    Are you using a single disc on the track? Initial bite isn't a problem for me as I can learn to get round that, feel and power is important, the current setup will lock the wheel when i blip the throttle when on the brakes, it is that powerful and sensitive. This why i started to wonder if I could get away with dumping a disc and calliper and still have a brake that is good enough.

    Like i said the next outing is at the Bikers Classic in Spa and that is an expensive event to attend to be ruined by a brake that isn't up to it. I think that the answer could be, go to single disc with an 11mm master but take the other disk and calliper with some HH pads just in case.
     
  14. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    Yes I am, I’m not racing though, only track days.
    I did race with single discs in the past though. I occasionally thought about trying twin discs on the racers but was kinda obsessed with weight saving in those days!
     
  15. storm42

    storm42 VIP MEMBER

    Joined:
    Jul 20, 2011
    Nice one, I think I will drop a disc then and change the Master.

    I don't race yet either, were you at the Endurance Legends weekend at Donnington? I am entered for The Bikers Classic and the Beezumph at Anglesey which is all I am doing this year, missed the entry for the Festival at Mallory:(
     
  16. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    I wasn’t at Donington but will be at the Mallory Festival and hopefully Beezumph.

    I’m doing a track day at Cadwell the Thursday before Beezumph then going directly to Anglesey (well at least that’s the plan).

    The Cadwell track day is run by the Morini club and they had spaces last I checked.

    How do you know the Mallory Festival is full? Attendance has been low these past years, I’d be surprised if they’re booked up.
     
  17. oldmikew

    oldmikew

    Joined:
    Jul 25, 2015
    Certainly last year at Mallory attendence was very low.
     
  18. Danno

    Danno

    Joined:
    Feb 7, 2010
    Swapping pads sounds like the easiest way to check.
     
  19. o0norton0o

    o0norton0o

    Joined:
    Apr 27, 2015
    I have a modified brake system on my commando too. I got rid of the leaky lockheed 5/8" diameter master cylinder. I bought a master cylinder from Don Pender (madass is his name here) which doesn't leak, has a 13mm diameter (I think) and has a perch shape which enables you to mount the stock lucas switch cluster. It was a welcome change in both better brake lever feel and power, with no more leaking of brake fluid, which over the years had ruined numerous paint jobs on my fuel tank.

    I also modified my bike to accept cast wheels and a 1" diameter larger yamaha disc. I still use the stock lockheed caliper mounted on an offset bracket to give clearance for the larger disc. It all works way better than the stock commando parts I had previously. I can brake powerfully with 2 fingers on the lever and the sensitivity is very good. I got lucky in some respects because I didn't design the system specifications. I threw it together from what was available and it happened to work well.

    Don's master cylinder came with a braided steel fluid line too. It was a bargin and an improvement. I know Don makes an entire kit which include a lightened rotor and high tech caliper along with the master that I bought.

    *** The reason we grind the pads for a certain race car was because that "Class" of cars didn't allow a proportioning valve to be used, so grinding the pad was a legal way to bias the brake force amongst the 4 wheels. It worked, but it was a pain in the ass. The car we ran in the next class up had a proportioning valve because it was legal in that class.

    You should find out if it's legal to run a single disc in your class, that sounds like the best option because of the lightening effect of losing a disc and caliper on one side. Then experimenting with different pads may help you dial in your braking preference. A lot has been said on the site here for resizing the master cylinder to improve braking. After switching to Don's master, I also would suggest either sleeving down the lockheed master (which there is a kit available) or switching to a different master altogether.

    Regardless of what choices you make, you can always experiment with grinding the pads you have to adjust your braking feel at a last resort, only potentially ruining a pair of brake pads if it doesn't have a positive effect...

    Post some pictures. I'd love to see your race bike.
     
  20. SteveA

    SteveA VIP MEMBER

    Joined:
    Dec 20, 2011
    I am racing a Rickman with a single Lockheed caliper on a 11 inch cast disc and GPFAX pads......they replaced Ferodo race pads and were a noticeable improvement. There is some more noticeable disc wear, but not horrendous.

    I have a 14mm master cylinder (early '70s Honda CB500 copy) and think 13mm would be an improvement. I don't think I would try 11mm, maybe 12 as a minimum. Though 14mm and the single disc works for me, I would note I have momentarily locked the front due to a minor lack of feel on deep standing water at the end of a straight. I have outbraked bikes fitted with more disc and less weight! (I am 100kg plus riding gear).

    I am not really sure why you would want twin discs on your Seeley, the majority of competitive riders including Gary Thwaites on Watson's 1007, use a single disc. I planned an option of twin discs when I built the bike, but it is really unlikely I will fit a second disc. You would most likely want a bigger tyre (110/80) to cope as well, and I prefer the 90/90 for turning. If you were running a triple with twin 10" I could understand it.

    I have a pair of Bendix pads in the tool box that I haven't used but I know would stop faster than the GPFAX pads because I have used them on a GSXR750SRAD...they are single finger braking from flat out, as long as they don't get wet! (Advice is if they get wet, bin them!) Upshot is I will stick with the GPFAX, I also have them on a lighter 500 single with a steel disc and a 13mm Master cylinder. I like them on that too, very much, regularly able to brake very late with that, could be the 13mm Master is better suited but I would not be allowed to use that particular one on a classic.
     
    Last edited: May 27, 2018
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