FRONT BRAKE Update

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3potjohn
Posts: 1243
Joined: 02 Jun 2007 13:58
Location: Devon

Re: FRONT BRAKE Update

Post by 3potjohn »

The dodge with ATE swinging callipers is to put your foot in the spokes. One meets folk who claim they are really good.But then again you can also find people who claim T160s don’t leak oil.
Have no issues with my front disc but the rear picked up in short order when I put new pads in backalong.
John
Seagreen
Posts: 86
Joined: 18 Jan 2018 21:18
Location: Cheltenham UK
Location: Cheltenham, Glos

Re: FRONT BRAKE Update

Post by Seagreen »

Hi, I have just fitted a 2012 Honda CBF 125 master cylinder to my 500 and am wondering whether I have a problem with the seals in the master cylnder (bought second hand) because no matter how much I bleed the system, the brake lever can always be pulled back to the bars - surely this cannot be correct? If I push the bike along and apply the front brake it does stop the bike pretty well but I am very concerned about the "excessive" lever movement. It is possible that I have still got some air in the system otherwise I guess that it must be leaking in the master cylinder. Has anyone else experienced this?
Thanks,
Charles
Vitesse
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Joined: 05 Jan 2019 13:42
Location: Barnacle
Location: Crowcombe

Re: FRONT BRAKE Update

Post by Vitesse »

Is the excessive travel matched by a delay before the brake has an effect? If so the problem might be the seals gripping the brake piston excessively thus pulling it too far back when you release. Thus it has to travel much further than it should every time. If the piston is clean it should self adjust (obviously) after every application to be close to the pad.
Seagreen
Posts: 86
Joined: 18 Jan 2018 21:18
Location: Cheltenham UK
Location: Cheltenham, Glos

Re: FRONT BRAKE Update

Post by Seagreen »

Hi Vitesse,
Thanks for your reply and to answer your question, there is no obvious delay before the brake takes effect, seems pretty responsive but the lever will continue to travel back to the bars, if pulled relatively firmly (by no means is excessive force required to pull it back to the bars). This is a bit of concern to me as I have never had a bike that has a front brake that comes right back to the bars.
Will give it more bleeding today to see if I can improve it.
Thanks again,
Charles
3potjohn
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Joined: 02 Jun 2007 13:58
Location: Devon

Re: FRONT BRAKE Update

Post by 3potjohn »

Useful tricks in the absence of any seal leal include tying the lever back overnight or trying to fill the system using a syringe and tube on the bleed nipple. I have had bubbles coming out of the bleed nipple on my rear calliper due to air leak passing the threads, cured using a fine wrap of PTFE tape.
dunk 1
Posts: 208
Joined: 25 Oct 2007 18:16
Location: cumbria

Re: FRONT BRAKE Update

Post by dunk 1 »

Hello - I spent a long time getting the front brake to bleed properly and in the end went for the same solution as John for the same reasons -PTFE tape to stop leakage around the bleed nipple. This coupled with with a modern suction brake bleeder and the improvement is considerable.
Duncan
dunk
pedro
Posts: 311
Joined: 04 Nov 2010 21:14

Re: FRONT BRAKE Update

Post by pedro »

I understand that a smaller master cylinder is the way to go, but what about on a double disc setup, what size works best in that instance?
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Daddy Dom
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Joined: 16 Nov 2006 19:48
Location: Auckland, New Zealand

Re: FRONT BRAKE Update

Post by Daddy Dom »

pedro wrote:I understand that a smaller master cylinder is the way to go, but what about on a double disc setup, what size works best in that instance?
I have gone from a 19mm bore master cylinder to a 16mm using a double-disc setup, using both standard hard-chromed Morini discs and cast-iron, drilled discs from a Ducati Pantah. Swapping discs improved wet-weather performance but annoyingly, threw rust up my bike every journey.

When properly set up - new pads, new fluid, hoses and discs in good condition - there is nothing at all wrong with the 19mm cylinder, it's a great front brake UNLESS you are (unfairly) comparing it to the two-finger effect found on modern bikes.

Eventually, my 19mm bore became scored so I found a NOS Grimeca m/c. This has a 16mm bore. I also refitted my newly-chromed Morini discs and once again, the whole system is in optimum condition and it works a treat.

So 19 or 16, take your pick. They can both be great.
DD½
MRC 3082½
pedro
Posts: 311
Joined: 04 Nov 2010 21:14

Re: FRONT BRAKE Update

Post by pedro »

Thanks Daddy Dom,
The brake as it is works fine, just has a bit of a lack of feel, wondering if the 16mm cylinder would improve that?
3potjohn
Posts: 1243
Joined: 02 Jun 2007 13:58
Location: Devon

Re: FRONT BRAKE Update

Post by 3potjohn »

My standard cylinder was 19 with a twin disc. This basically failed when I had to complete a journey of approx 400 miles.
I luckily picked up another which is a smaller bore, perhaps 16mm, ( must measure one day) fitted it without rebuilding it and it is nearly too good.
I think I can say the best brakes I have had on a motorcycle, but given I have spent a good deal of time riding bikes with ATE callipers it is not saying a lot.
I did find on stripping the old master cylinder there was an old seal rammed in the end in addition to the new one I fitted 8 years earlier. I blame poor garage lighting.
John
Seagreen
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Joined: 18 Jan 2018 21:18
Location: Cheltenham UK
Location: Cheltenham, Glos

Re: FRONT BRAKE Update

Post by Seagreen »

Thanks for all your responses and it is interesting to note that I think that the Honda CBF 125 Nissin master cylinder piston is only 12.7mm dia. Perhaps I am expecting too much from it with my double disc set up on the 500? I replaced the original because the front brake always felt a bit "wooden" with a lack of feel. Perhaps I will check whether the original piston diameter is 16mm or 19mm referred tp by Daddy Dom. If the latter then perhaps I should try and find a suitable 16mm master cylinder - does anyone have a recommendation for this?
Adios,
Charles
Al Limite
Posts: 24
Joined: 27 Jan 2020 12:33
Location: Exeter, England

Re: FRONT BRAKE Update

Post by Al Limite »

Hi Seagreen,
I was in a similar situation in 2020 and fed up with a wooden front disc brake ( standard system with single front disc ) I took the advice of other forum members and searched the bay. Purchased a pattern Suzuki GS/GN 125 and GN250 DK from a Chinese supplier circa £10 delivered, and it transformed the front brake. Bonus was having a cranked lever and a switch for a brake light, which the original never had.
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Daddy Dom
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Joined: 16 Nov 2006 19:48
Location: Auckland, New Zealand

Re: FRONT BRAKE Update

Post by Daddy Dom »

Al Limite wrote:Hi Seagreen,
I was in a similar situation in 2020 and fed up with a wooden front disc brake ( standard system with single front disc ) I took the advice of other forum members and searched the bay. Purchased a pattern Suzuki GS/GN 125 and GN250 DK from a Chinese supplier circa £10 delivered, and it transformed the front brake. Bonus was having a cranked lever and a switch for a brake light, which the original never had.
Hi Charles,
as above, many owners are fitting after-market items (of unknown quality and lifespan) that are easily available online. I'm sure they work but, really? A Chinese copy of a Japanese part designed for a bike with 12bhp?

But then, do you want an Italian bike or ...

For my part, I cherish my hand-built, small-run Italian motorcycle and whenever sensible and possible I do not want to dilute my thoroughbred by using a mixture of "parts from elsewhere" shall we say. I had to change headlights and don't go as far as using Pirelli tyres but each to their own, I suppose. And I use the recommended Castrol GTX, not extra-virgin olive. :lol:

I got my beautiful NOS 16mm master cylinder from Mdina Italia, complete with a cranked lever and have since fitted a brake-light switch. (If I hadn't I could easily have used a hydraulically-operated one.) Of course, it cost far more than the alternatives but that was entirely my choice.
Best, DD
MRC 3082½
Seagreen
Posts: 86
Joined: 18 Jan 2018 21:18
Location: Cheltenham UK
Location: Cheltenham, Glos

Re: FRONT BRAKE Update

Post by Seagreen »

Thanks, Daddy Dom and Al Limite for your comments and advice. I am trying to keep my Morini as standard as practically possible but I would prefer the brake to have a bit more feel to it. Which models were the 16mm piston sized master cylinder fitted to in the Morini range as standard - I am assuming they were Grimeca?
Thanks,
Charles
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Daddy Dom
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Location: Auckland, New Zealand

Re: FRONT BRAKE Update

Post by Daddy Dom »

Yes, both 16mm and 19mm are Grimeca. I imagine Moto Morini took whatever Grimeca were supplying and Ariete seals are usually easily available for both.
I couldn't imagine how one would source good-quality seals for a GN copy-caliper.
Best,
DD
MRC 3082½
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