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Quick Brake Question
#803872 04/03/20 7:11 pm
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Hi there. I've just fitted a brand new twin disc conversion to my T160, new lightweight Girling Calipers, new Girling discs, new twin s/steel braided hose kit from L.P Williams.

Question: I currently have the standard handlebar brake master cylinder unit, one of the L.P Williams stainless steel barrel ones, which worked perfectly on the original standard single disc old style Girling caliper set up and was a cinch to bleed up from scratch.

I have committed around 5 hours ( yep, really ) and about half a gallon of brake fluid trying to bleed this new system to get a decent "lever".
I've got a vacuum type bleeder which operates from a compressor and has always worked well another bike brake systems to get a good hard lever.
I've tried reverse bleeding using a large syringe.
I've tried the traditional procedure of open bleed nipple pull lever, close bleed nipple etc etc.
All of this to no avail in getting an air free system and decent lever.
I know bleeding a new system is always a pain but I've always got there in the end but not this time !
I've just spotted that L.P.Williams do a specific master cylinder for a twin disc set up.
So, is this a critical upgrade when fitting a twin disc set up and am I flogging a dead horse with the standard master cylinder ?

Many thanks

Steve

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Re: Quick Brake Question
SJS #803880 04/03/20 7:34 pm
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Originally Posted by SJS
So, is this a critical upgrade when fitting a twin disc set up

No, as the (5/8" diameter) master cylinder/piston size was too large and therefore the hydraulic ratio was wrong to begin with, in my opinion.

Last edited by L.A.B.; 04/03/20 7:35 pm.
Re: Quick Brake Question
SJS #803897 04/03/20 10:56 pm
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If the specific twin disc master is 0.7" bore the brakes will have the comical drum brake feel, very hard and no brake. I have Grimeca 1010 calipers on 11" discs with a 5/8" master and that is still too stiff for a good two finger brake.
The problem with your bleeding is you have to point the hose end of the master steeply downward. Otherwise air will be trapped at the banjo bolt.
Teflon lined hose needs help in moving air bubbles up the line. I find it helps to vigorously shake the line periodically. Any place there is a junction there is a place that air can be trapped. No point in the line from the caliper to master should be higher than a point after it.
Did you also check the reservoir bleed hole is open with the lever released? I know AP has wonky instructions about turning the cylinder to some point then backing off but if the bleed hole is not uncovered by the seal then the reservoir will not feed fluid into the cylinder and you can bleed all day and not get it to work.

Re: Quick Brake Question
SJS #803898 04/03/20 11:03 pm
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Girling calipers? I did not know they made calipers for triples. Grimeca maybe?

Re: Quick Brake Question
DMadigan #803902 04/03/20 11:25 pm
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Originally Posted by DMadigan
Girling calipers? I did not know they made calipers for triples. Grimeca maybe?

Wassell Girling

https://www.britishbikebits.com/ap-racing-alloy-caliper

Re: Quick Brake Question
SJS #803917 04/04/20 1:59 am
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I don't know the angle of your master cylinder on the handlebars but make sure the master is level and the tiny pressure relief hole is on top when you're bleeding. Those little things make an impossible problem possible!

Re: Quick Brake Question
SJS #803925 04/04/20 2:46 am
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And, everyone says it doesn't work, but leaving the lever pulled in and the reservoir cap off overnight helps...worked for me.

Re: Quick Brake Question
tridentt150v #803940 04/04/20 7:07 am
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Originally Posted by tridentt150v
And, everyone says it doesn't work, but leaving the lever pulled in and the reservoir cap off overnight helps...worked for me.
Agreed .. Bike on the side stand with bars turned to left (puts reservoir at highest point) plus lightly tap the hydraulic line starting down at the calliper & work your way up to the top can also help in dislodging air bubbles.

Re: Quick Brake Question
tridentt150v #803942 04/04/20 8:51 am
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Originally Posted by tridentt150v
And, everyone says it doesn't work, but leaving the lever pulled in and the reservoir cap off overnight helps...worked for me.
The lever in blocks the port between the reservoir and the pump, so I fail to see how it would work?
I have tried it though, but not with success.
What I do is I crack the bleed nipple open, with the usual hose in a jar set-up, and leave it. No pumping or anything needed, just let it sit and bleed, and make sure to replenish the reservoir so it doesn't run dry, until you're satisfied.
I do my car brakes the same way, if I've worked on them or just want to change the fluid. One nipple at the time.
The moving fluid seems to disturb the air pockets so I never get spongy brakes.
Too easy? Try it.

SR

Re: Quick Brake Question
SJS #803964 04/04/20 12:13 pm
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Thanks, some interesting options to try that I haven't done so far regarding bleeding the system.
I've ordered the so called twin disc master cylinder, I'm assuming this option is there for a reason, we'll see.
In the meantime, back to the bleedin, bleeding !
All advice and comments appreciated as usual.

Regards

Steve

Re: Quick Brake Question
SJS #804075 04/04/20 11:15 pm
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You could have an problem with your new calipers: piston bores not perpindicular to the mounting flange or more likely seal stiction pulling the pistons away from the pads.

Eric


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Re: Quick Brake Question
SJS #804121 04/05/20 7:38 am
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Small bore M/cyl with braised lines should be good. More powerful brake for how hard you squeeze the lever, however the lever will be softer and pull in further. The big bore cyl will give a harder lever but less power and feel.


mark
Re: Quick Brake Question
BikeVice #804122 04/05/20 7:43 am
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Hi SJS

+1 on Eric's comments on alignment and seal stiction. I am going try set of AP seals in my replica caliper.

Best regards

Esme


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Re: Quick Brake Question
SJS #804126 04/05/20 8:35 am
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The caliper piston seals are supposed to distort and move with the piston when the brake is applied and then pull the pistons back to reduce pad drag when the brake is released. The pistons should only advance through the seals as the pads wear.

[Linked Image from mgexp.com]

https://mgaguru.com/mgtech/brakes/bt104.htm
[Linked Image from mgaguru.com]
"As the piston moves outwards from its static position (1) the fluid seal is deflected (2). When the hydraulic pressure is released the fluid seal regains its static position, moving the piston back and providing clearance at the friction pads."

Re: Quick Brake Question
L.A.B. #804172 04/05/20 7:02 pm
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LAB

I am not disputing the fact, part of the main seals function is to deflect and move with the piston when under pressure and bring the piston/pad clear when the pressure is released. However should the seal be over tight or manufactured from the wrong grade of material, it is not uncommon to to find the seal will over deflect rather than release the piston resulting in an excessive pad /piston clearance. and a soggy feel at the lever.

Best regards

Esme


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Re: Quick Brake Question
Esmerela #804176 04/05/20 7:48 pm
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Originally Posted by Esmerela
However should the seal be over tight or manufactured from the wrong grade of material, it is not uncommon to to find the seal will over deflect rather than release the piston resulting in an excessive pad /piston clearance. and a soggy feel at the lever.

I'd agree that's not impossible but reports of a spongy lever-action after fitting double discs is not uncommon and likely caused by air trapped in the system.

Re: Quick Brake Question
SJS #804204 04/06/20 1:41 am
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It could be in fact normal reading the original post. It will be much spongier. If it had braided hose before it will be twice as spongy and move twice as much. If it had rubber hose before it would be slightly less than twice as much. If it (the lever) stops before it hits something its worth trying. It may also be that the lever moves excessively before the piston starts moving. Where the lever goes rock-hard may not be where the brake is full on. Just rocking the bike can give you an idea. It definitely will not work as before, it will be softer and travel further, and be twice as powerful. Obviously it's not right if it pulls to the bar and doesn't lock the brake.

When I did this years ago I fitted rubber hoses that I scrounged, the lever came to the bar. So I needed to fit braided lines which swell less under pressure which restored some of the lever height, and it was fine, but the lever still came in further than the single disc set up, but the thing really stopped. The original was like squeezing a brick, and far far less effective.

Last edited by Mark Parker; 04/06/20 1:54 am.

mark
Re: Quick Brake Question
SJS #804435 04/07/20 7:40 pm
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I went through a similar trial with my new twin discs last year.
tried all the usual, back bleed , inversions , tapping .Best i could get was a very spongey lever feel, with barely a brake at all.

What worked in the end was, remove a brake pad on each caliper, pump out the pistons a wee bit, refit the pads, forcing the pistons back, jiggle the brake lever and watch for bubbles appearing in the reservoir, when the bubbles stop it should have firmed up. I did each pad in turn, worked a treat , I am eternally grateful to Lorne Chisolm who passed this tip on to me , I was at my wits end.


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Re: Quick Brake Question
SJS #804473 04/08/20 1:33 am
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You can also accomplish that by taking the caliper off and using two tire irons between the pads to squeeze them back in.
The master banjo bolt does not bottom in the cylinder so there always will be a diameter step between the bolt bore and the through hole of the cylinder for air to be trapped in unless the master is pointed almost straight down.

Re: Quick Brake Question
SJS #805815 04/18/20 4:12 pm
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Update: Fitted the supposed specific twin disc master cylinder cylinder and started again.

I had everything, the callipers and lines "hanging" under their own weight in order to get the brake hoses as straight as possible with no kinks.
To start, I tried one of the suggestions above where by I just let the fluid flow through the system with bleed nipples open and constantly topping up the reservoir.

When I felt that had served its purpose I then remounted everything in position and went back to conventional bleeding, open, pump, shut, open, pump shut.
Tried the pad removal, pump pistons out, push back in, then back to bleeding.

I get to a stage whereby the fluid pumps clear of any air at each caliper and I can "pump up" a decent firm lever which in fairness will hold once pumped up but once you release it its back to the handle bar unless you pump it up again.
So, back to more bleeding and sure enough more air in system comes out.

There are definitely no fluid leaks anywhere, after all, a pumped lever does hold firm and doesn't fade away nor is there any fizzing or air bubbles coming up in the fluid reservoir but after many hours this is the best I can get to which is obviously not fit for purpose.

There comes a stage when you are just repeating the same things without any significant improvement and thats where I am and maybe its time to look at other options.

I'm not overly confident with the brake line system I got from L.P Williams, nothing to do with the quality, it looks great but the complexity of it.
3 pipes and the alloy link bar and a lot of subsequent connections.

I've had a close look at other modern sports bikes I've got and they either have one continuous pipe per caliper running direct from the master cylinder where they are doubled up on the same banjo connector, thus being fed direct from the master cylinder with no other interruptions.

Others do have a similar junction section like the alloy link bar in the LPW kit where the single feed from the master cylinder splits into two but it is a much smaller item and therefore less scope for trapping air.
I've stripped and rebuilt these systems, some with infamous 6 pot calipers and whilst its never a cinch it's always successful.
I have never ever had the problems I'm having with this set up.

So, to my eventual question, has anyone else who has done this twin disc conversion exercise, fitted a different brake pipe arrangement to the L.P Williams kit, if so what did you do and was it successful.
Likewise what are your thoughts on going for a more simple, direct brake line route like I've detailed above.

Starting to wish I'd never gone this route, bike vanity eh !

Thanks Steve

Re: Quick Brake Question
SJS #805850 04/18/20 8:43 pm
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Right, quick update.
Removed the previous set up completely.
I had 2 full length braided brake hoses hanging around to fit one from each caliper direct to the master cylinder, doubled up and fitted to the master cylinder with the correct double banjo fitting.
30 mins later after doing the usual standard bleeding procedures I now have a good firm lever.
Whilst I will have to get specifically tailored length braided hoses to route them nicely and do the job properly, this has confirmed my concerns about the complexity of the L.P Williams twin disc pipe kit and cross rail, there's simply too many parts, angles and potential for air traps in that arrangement.
The only dilemma with my new set up is I've had to dump the hydraulic brake light switch that previously screwed into the master cylinder in lieu of doubling up the brake pipes at that outlet.
Any suggestions on an alternative brake light switch mechanism ?
Phew !

Re: Quick Brake Question
SJS #805852 04/18/20 9:06 pm
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They make double banjo brake light switch banjo bolts.

Re: Quick Brake Question
SJS #805862 04/18/20 10:04 pm
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Thanks Dave, just found them on Venhills web site. Jobs a good 'un ..... finally.
To anyone else attempting this twin disc conversion, with regard to the brake lines, this is definitely the way to go in my experience.
One line direct from master cylinder to each caliper with above mentioned double banjo brake light switch for the master cylinder.

Re: Quick Brake Question
SJS #807399 05/01/20 12:53 pm
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Hi, does anyone know a source for a double banjo brake light switch to suit the T160 front brake master cylinder which requires 3/8 unf thread.
Venhill only do it in single banjo form and I've drawn a blank on other searches.
I can get round the issue by using a male / female converter adapter but would it would be neater without it.

On another issue, in an effort to improve the gear selection on my bike, I previously stumbled across a post ( can't remember where ) about someone called Dave Drew who apparently makes a ball bearing cam plate plunger which is again, apparently a vast improvement on the OE item.
Does anyone know how to contact Dave Drew ( assuming he's still doing this stuff ) as I'm keen to give this mod a go.

As usual, thanks for any help.

Re: Quick Brake Question
SJS #807402 05/01/20 1:20 pm
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Originally Posted by SJS
On another issue, in an effort to improve the gear selection on my bike, I previously stumbled across a post ( can't remember where ) about someone called Dave Drew who apparently makes a ball bearing cam plate plunger which is again, apparently a vast improvement on the OE item.
Does anyone know how to contact Dave Drew ( assuming he's still doing this stuff ) as I'm keen to give this mod a go.


https://www.eBay.co.uk/itm/Triumph-Trident-T160-5-speed-roller-ball-gearbox-plunger-OEM-57-4226/274051039709?hash=item3fceb701dd:g:5YcAAOSw77pbX3XV

(I've used the twin full-length brake lines and personally I didn't find it to be any improvement over the one into two line)

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