My favorite brake firming technique doesn't work on my Norton

Joined
Jun 14, 2007
Messages
1,723
Country flag
I'm sure most folks if not all are familiar with the technique of firming a mushy disc brake by securing the brake lever in the "on" position (e.g., bungee the brake lever back towards the handlebar) and leaving overnight or longer.

I've had great success with this technique over the years, on other bikes. But it seems to have little or no effect on my Commando (73 850, FWIW). Is the Norton brake system different from most in some way that reduces or eliminates the effectiveness of this technique?
 
Joined
Jan 31, 2010
Messages
2,407
Country flag
Are you saying that normal bleeding doesn't work and that you routinely use the method you describe? Seems an odd way to bleed a brake system - essentially waiting until the air in the system finally migrates upward into the mastercylinder.

If normal bleeding doesn't work properly, have your tried pressure bleeding? Can't really come to grips with "overnight sitting" as a way to bleed brakes but with a vertical brake line between the caliper/mastercylinder, certainly the laws of physics dictate that it will work...eventually. I guess if you don't care about waiting overnight to ride the bike after brake work, it doesn't really make any difference and you can ride the next day after the bike "bleeds" itself! ;)

Hmm..maybe that's a "feature," not a problem! :D
 
Joined
Jun 14, 2007
Messages
1,723
Country flag
No, this is not a substitute for normal bleeding, which I do via the old pump-hold-release method (haven't had much luck with other techniques on the Norton but this works fine). This is an "enhancement." At least, on other bikes. Have had really amazing results on other bikes, but not the Norton. Was just curious if there's something "unusual" about the system that makes this technique not work, or at least not work as well as I'm used to.
 

mean gene

VIP MEMBER
Joined
Dec 21, 2020
Messages
149
Country flag
Heard of this method and tried it on front disc did not improve a thing it is a New master cylinder. Have been fighting with it for months. Bled it from bottom up, from the top down, no improvement. Have decided to let it alone till weather breaks and I can ride it hopefully shake the air out of it!!
 
Joined
Jul 11, 2010
Messages
3,770
Country flag
Over the years I have had some problems with brake bleeding, if it won't bleed from the caliper then I bleed the MC end this works every time for me, have never done the over night bleed, I could be wrong but letting it sit over night with the lever tied to your handle bars wouldn't you still have spongy brake and air in the system.
Why most brake places use pressure bleeding tools, they would go broke if they had to leave things overnight.

Ashley
 
Joined
Mar 15, 2010
Messages
115
Country flag
So to get air out of the system is has to have somewhere to go. If the brake is locked in the “on” position there is nowhere for the air to go as the bleed hole in the master cylinder is blocked off. The best way that I have found to bleed brakes is to use a large syringe to slowly fill system from the bleed nipple back to the master cylinder.
 

L.A.B.

Moderator
VIP MEMBER
Joined
Nov 20, 2004
Messages
16,556
Country flag
Was just curious if there's something "unusual" about the system

The Lockheed master cylinder contains a check valve (item 11, link, below) that other master cylinders often don't have although I haven't found it to be a problem and bleed them the usual way.

https://andover-norton.co.uk/en/shop-details/15706/valve-assembly-4312-318-99-2754-
 
Joined
Jun 14, 2007
Messages
1,723
Country flag
Thanks all. Again, this is not bleeding method per se, or rather, not a substitute for traditional bleeding. But however firm (or not) your brake is, a day or two like this typically will produce a noticeable firming.
 

baz

VIP MEMBER
Joined
May 26, 2010
Messages
2,859
Country flag
I have used the over night method quite a few times and it works really well
I've never used it with a stock commando system though so I can't comment on that one
 
Joined
Dec 28, 2009
Messages
4,035
Country flag
Heard of this method and tried it on front disc did not improve a thing it is a New master cylinder. Have been fighting with it for months. Bled it from bottom up, from the top down, no improvement. Have decided to let it alone till weather breaks and I can ride it hopefully shake the air out of it!!
Bottom up.
 
Joined
May 28, 2003
Messages
2,604
Country flag
Fixture In the works
Now rebuilt calipers,,,,,,, wonderful...
Now to install and bleed them. That's when the fun starts. I occasionally get call by professional shops for tech advice.
In this case, one email asked about difficult and air bleed reluctant calipers. This difficulty is quite common.

Referencing my pix in post 1 this was my suggestion:

"The problem/solution is I guess about bubble control. The pix shows the rear piston can get vented at the rear top to the bleeder and the front/outer can vent through the MC hose.

The inter-piston drilling is the extreme difficulty to overcome. neither bleeder nor MC hose motivates bubbles to move between sides.

Laying/holding the caliper horizontal with the rear piston down and angling bleeder partially up and pumping and releasing may move the bubbles up eventually to finally exit up to the outer piston and toward the hose. Holding lever with rubber band will help under pressure grain of sand bubble to finally rise to MC"

Normal bleeding is often helped with the overnight rubber band hold under pressure on the brake lever. This turns a big bubble to the size of a grain of sand.

Pre filling and bleeding with a combination simultaneous dual hose port and bleeder port fixture may be of very significant value.
I have a prototype design concept as well as the procedure needed to fabricate and test the design.
Let you know how it works out...
 
Last edited:

marshg246

VIP MEMBER
Joined
Jul 12, 2015
Messages
1,206
Country flag
The best, and messiest way I've found is to (best when rebuilding a caliper):
Disassemble the caliper
Plug the hole where the hydraulic line will go.
Loosen the bled screw a little.
Lay the caliper on it's back (inner side down outer plug up).
Fill the inner chamber about 1/4 way
Put in the inner piston in and push it into place.
Put in the outer piston and fill.
Put in the outer plug.
Close the bled screw.
At this point the caliper has no air.
Clean up the mess and then install the caliper.
Connect the line and bled normally - takes only a few seconds.

If not rebuilding a caliper, I simply bled more or less normally, but it takes about 100 slow/gentle squeezes before all the air is out. At around 50 squeezes you'll think the air is all out, but it isn't! You're trying to get air in the inner side to come out the same small hole as the fluid is going in - are stupid design!

I keep looking for a hyperemic with a long thin needle. A needle with a diameter smaller than the small inner caliper hole would allow you to inject fluid directly into the inner and air to escape. Thin needles are easy to find, long thin I can't find.
 

Tornado

VIP MEMBER
Joined
Dec 5, 2017
Messages
2,565
Country flag
When my MC was not firming like it should after a rebuild, I tried all sorts of methods, syringe reverse filling, pull a nd hold, overnight holding on etc.
What ultimately worked was rapidlly flicking the lever 50+ times, while watching the fluid in reservoir. I suddenly saw a couple of very tiny bubbles float up the small port in the reservoir bottom. Been a solid feel ever since.
 
Joined
Nov 18, 2005
Messages
913
Country flag
This method can work well for those last few little bubbles that refuse to exit the bleed nipple.
However, the entire system needs to be uphill for the bubbles and this includes the master cylinder bore.
Usually I put the bike on its side stand and turn the bars fully left.
With a cable tie around the lever overnight any bubbles left in the system accumulate on the end of the piston and are ejected from the return port when you release the brake lever.
 

gortnipper

VIP MEMBER
Joined
Nov 11, 2013
Messages
4,072
Country flag
This method can work well for those last few little bubbles that refuse to exit the bleed nipple.
However, the entire system needs to be uphill for the bubbles and this includes the master cylinder bore.
Usually I put the bike on its side stand and turn the bars fully left.
With a cable tie around the lever overnight any bubbles left in the system accumulate on the end of the piston and are ejected from the return port when you release the brake lever.
Then with the brake cable tied, occasionally rap the caliper with your knuckles, then shake the line up to the mc, and rap the mc with your knuckles. Repeat. Repeat. Sleep.
 
Joined
Aug 5, 2017
Messages
1,152
Country flag
I fitted a Magura 13mm master and a CP caliper with standard diameter disc.. i forward bled. reversed bled, sucked the fluid through the system. no air was to be seen but the lever felt "wooly" but more worryingly the laver came almost to the bars when pulled hard.
So i cable (zip) tied the lever to the bars and lest for 24 hours
I now have a firm pull on the lever that doesn't come in close to the bars
Thinking on why this was happening i removed the new brake pads and inserted a worn out set pressurized the system so that the pads were touching the disc & left the bike.
Came back to it a few days later to find a "wooly" lever coming close to the bars,
Now i can see the caliper pistons in operation I'm seeing what looks like a lot of caliper piston reversal on lever release... so i cable tie the lever to the bars once again and left.....
Following day i have a firm lever not coming anywhere near the bars and I'm not seeing the same amount of piston reversal

I know its the piston seals that pull the pistons back slightly to provide a running clearance... but i have to assume the new caliper piston seals are just pulling the pistons back too much and leaving the system pressurized overnight is allowing everything to "settle"
 
Last edited:
Joined
May 28, 2003
Messages
2,604
Country flag
You're trying to get air in the inner side to come out the same small hole as the fluid is going in - are stupid design!
"The problem/solution is I guess about bubble control.
The caliper has 2 ports!
Both pressure and vacuum applied to both, in an intellgent sequence, using a purpose built design fixture is my mission to perform bubble control.
 

L.A.B.

Moderator
VIP MEMBER
Joined
Nov 20, 2004
Messages
16,556
Country flag
I know its the piston seals that pull the pistons back slightly to provide a running clearance... but i have to assume the new caliper piston seals are just pulling the pistons back too much and leaving the system pressurized overnight is allowing everything to "settle"
I found new caliper seals can make the brake feel spongy for a while.
 
Joined
Aug 5, 2017
Messages
1,152
Country flag
I think it may be the "newness" or stiffness of the new seals exerting a firmer pull on the pistons.... were only talking a few thousands on an inch, but enough to allow the lever to come in more
 
Top