Author Topic: De Linked brakes  (Read 2313 times)

Offline Nigel

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De Linked brakes
« on: March 23, 2020, 02:01:40 PM »
Probably not the first person to ask this - but...
I want to de link the brakes, on my 750S3.
Sorry but I'm not really interested in answering questions about why I should want to do this.....
My question is what size front master cylinder is best.
I intend leaving the standard twin Brembo front calipers and just link to the front brake lever. I know that if the wrong size/bore master cylinder is used the brakes will be crap.
I remember doing this many years ago and not changing the master cylinder and the bakes were awful.

Offline Perazzimx14

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Re: De Linked brakes
« Reply #1 on: March 23, 2020, 02:19:14 PM »
The stock MC should be fine becasue of the dual disc's. It was the 850T that had an oversized MC and needed either a smaller MC (10/10.5mm) if using the stock single disc or add another disc and caliper of using the stock MC.


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Offline rutgery

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Re: De Linked brakes
« Reply #2 on: March 23, 2020, 02:43:26 PM »
I'd go for the stock sizes of MC's but reversed. So the size of the master for the integral braking system should become your new front dual disk master, and the old single master should become your new rear master size.

PS: I'm running double brembo 30/34 calipers in front and a 16mm master works incredibly well with them.
« Last Edit: March 23, 2020, 02:45:08 PM by rutgery »
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Offline Stevex

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Re: De Linked brakes
« Reply #3 on: March 23, 2020, 02:52:46 PM »
Nigel, I de linked my LM2 brakes.
What are the MC sizes on the 750?
The LM2 original MCs are PS15 on the two linked calipers and a PS12 on the right handlebar for the single front operated caliper.
I fitted a PS15 onto the right handlebar to feed the 2 front calipers and a PS12 for the rear caliper.
The PS15 is available off the shelf from Gutzibits or HMB-Guzzi.
I sourced a PS12 for the rear from a Ducati 860GT. It is the same as the Guzzi item but needs some machining to the mounting points, as on the Ducati it is mounted the opposite way round to the Guzzi.

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Re: De Linked brakes
« Reply #3 on: March 23, 2020, 02:52:46 PM »

Offline moto

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Re: De Linked brakes
« Reply #4 on: March 23, 2020, 04:00:44 PM »
I would consult Guzziology, which has a convincing discussion and recommendations.

Alternatively, I would use calculations to figure it out for myself.

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Offline Motorad64

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Re: De Linked brakes
« Reply #5 on: March 23, 2020, 07:37:31 PM »
I just went through this with the LeMans I'm getting back on the road.   MG has a new Round resevoir 15mm front MC:

http://www.mgcycle.com/index.php?main_page=product_info&cPath=110_112&products_id=3219


And HMB has a beautifully made rear 12mm rear MC:
 
https://hmb-guzzi.de/Master-cylinder-PS-12-T3-Le-Mans-1-2-3-etc

Both fit great and look correct.  Will report to brake feel once I get her fully back on the road




Online Turin

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Re: De Linked brakes
« Reply #6 on: March 23, 2020, 08:18:07 PM »
I think the 15mm is a little big for a pair of F08 calipers. I'm running a pair of 4 piston calipers on my 850T with the stock 15mm master and stainless lines. Stops great with good feedback from the lever.
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Offline wirespokes

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Re: De Linked brakes
« Reply #7 on: March 23, 2020, 11:00:21 PM »
I delinked the LM4 and it's got the 12mm front and 15mm rear and left the master cylinders as is. The rear is a little stiff but totaly usable. I find the front to be excellent now with stronger brakes and lever travel is about an inch or inch and a quarter.

Be sure to bleed the system very well otherwise the lever will have too much travel.

Guys tell me I'm wrong, that it can't work, the charts recommend a larger master, there won't be enough leverage, or nonsense like that. I'm here to tell you the 12mm (actually 1/2" - closer to 13mm) master with twin F08 calipers (38mm pistons) is a great combo.

Offline Nigel

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Re: De Linked brakes
« Reply #8 on: March 24, 2020, 04:02:35 AM »
Many thanks for everyone who's taken the time to reply.  Firstly I don't have a master cylinder at all, at the moment - its missing from the basket ! , so I need to buy a new one.
It makes sense to me now from the comments, I think I will try a 15 or 16mm and then reduce the rear to a 12mm
I did read Guzziology but still wanted opinions from guys who have actually tried and tested solutions.
Thanks again

Online Dukedesmo

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Re: De Linked brakes
« Reply #9 on: March 24, 2020, 05:59:15 AM »


Quote from: Stevex on March 23, 2020, 08:52:46 PM
Nigel, I de linked my LM2 brakes.
What are the MC sizes on the 750?
The LM2 original MCs are PS15 on the two linked calipers and a PS12 on the right handlebar for the single front operated caliper.
I fitted a PS15 onto the right handlebar to feed the 2 front calipers and a PS12 for the rear caliper.
The PS15 is available off the shelf from Gutzibits or HMB-Guzzi.
I sourced a PS12 for the rear from a Ducati 860GT. It is the same as the Guzzi item but needs some machining to the mounting points, as on the Ducati it is mounted the opposite way round to the Guzzi.

___________________ ___________________ ___________________ ____

I did likewise on my LM2; used a 12mm Ducati master at the rear (had to counterbore the mounting holes on the other side to 'reverse' it) and I used a Brembo RCS 15mm for the front.

Works great, the brakes really are very good for a 40 year old bike that weighs as much as a house...


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Offline mtiberio

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Re: De Linked brakes
« Reply #10 on: March 24, 2020, 07:01:20 AM »
in general a bore too big will work but feel wooden. a bore too small may come back to the bar, but if it doesn't it will give great feel.
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Offline acguzzi

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Re: De Linked brakes
« Reply #11 on: March 24, 2020, 07:50:33 AM »
I agree with what wirespokes and mike tibero said, I delinked my LM2 but did not change the master cylinders. I have stainless braided hoses and keep the fluid fresh and bled. The brakes feel great and are really strong, but you have to keep up with condition of the brakes.

Offline philwarner

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Re: De Linked brakes
« Reply #12 on: March 24, 2020, 10:43:05 AM »
My 96 Cali came to me with de-linked brakes and they seem to work well so I haven't given a thought to master cylinder sizes.  Apparently the PO of long ago chose the right combination along with the 7/33 gearing and hydraulic clutch.
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Offline wirespokes

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Re: De Linked brakes
« Reply #13 on: March 24, 2020, 10:49:27 AM »
mtiberio lays out the problem perfectly: Master cylinder too large = minimal lever travel, wooden feel. Too small = too much lever travel before lock up.

The best brakes come with probably about half the possible lever travel.

Yes, the 15mm master will work the calipers, but the lever only travels about a 1/2". Do you want one or two-finger brakes that really grab, or a lever that requires a fair amount of force and feels like you're pressing a block of wood against the disc?

Offline moto-uno

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Re: De Linked brakes
« Reply #14 on: March 25, 2020, 12:49:05 AM »
  I de-linked the brakes on my Le Mans 2 about 10 years ago , because the road leading to my place was washed out in a flood .
The alternate route was a hilly gravel road and applying the linked brakes going down hill was rather frightening ( poor traction control)
   At the time I was working at a Yamaha dealership and I found the front master cylinder from the twin disc Yamaha Seca worked well
and rebuild kits are still available . Lots of alternatives , plus the Japanese switch gear is great .   Peter

Offline earemike

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Re: De Linked brakes
« Reply #15 on: March 26, 2020, 07:25:23 AM »
I’ve run 15mm on a couple of bikes but also run the Brembo rcs19 on a couple (one with Brembo 4 piston). I actually liked the rcs19 over the 15 but that might be to do with the adjustment and my expectations. I have a more modern adjustable lever ready to adapt to a traditional 15, might be even better if I have it right where I like...

I just need to find the time as I’m not in lockdown.
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Offline wicks

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Re: De Linked brakes
« Reply #16 on: October 24, 2024, 12:20:46 PM »
Have people de-linked their LM 1's using the original masters? Have decided I need to de-link the LM because the bike is FAST. Quicker than any my other guzzis including the 1000s. Handles like a proper italian sportbike.

What lines would/could I use that look most original (I prefer hose to steel)? Hoping to find a kit...
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Online Antietam Classic Cycle

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Re: De Linked brakes
« Reply #17 on: October 24, 2024, 12:53:22 PM »
Charlie

Offline wirespokes

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Re: De Linked brakes
« Reply #18 on: October 25, 2024, 11:21:05 AM »
Guys will tell you that you need a larger front master to run two calipers. Not true! In fact, the standard front master is oversize of what is actually needed for one caliper and is perfect for two.

The rear master will be oversize for just one caliper, but it's the only size Guzzi offers. It is possible to get a master for a Ducati in a smaller size and only needs minor modification to work. I've used the stock master and it works, but can't lock up the rear - not that I want to. I got used to it and it feels fine. Many others have done the same and when I've asked, get the answer they've run it with the standard master.

I think the best way to run the lines is with a four way splitter mounted at the lower triple tree. Get another right hand rubber line, mount it on the left side, and run it to the splitter. Done deal. Easy, and looks factory.

Online Antietam Classic Cycle

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Re: De Linked brakes
« Reply #19 on: October 25, 2024, 12:13:25 PM »
Guys will tell you that you need a larger front master to run two calipers. Not true! In fact, the standard front master is oversize of what is actually needed for one caliper and is perfect for two.

On a disk brake Eldorado and 850-T, this is true - the original PS15 master cylinder is much too large for a single F08 caliper, but works great with two.

But for later Guzzi with a PS12? It depends on how one wants the brake lever to feel - long travel and "soft", or short travel and firm. From the Vintage Brake website: "For 2 piston opposed calipers, I like ratios in the 27:1 range, feeling some line and caliper flex. For a firmer lever, use 23:1."

In my experience, using the original PS12 master cylinder (which has an actual bore diameter of 12.7/.500") with two F08 calipers (four 38 mm pistons) will result in a ratio of 35.81, long lever travel and "soft" feel. The one Eldorado I did this way stopped great, with little lever effort, but the lever was almost contacting the grip in hard stops.

Using a PS15 (actual bore diameter of 15.84 mm - just under 5/8") with two F08s will result in a ratio of ~ 22.92, and a firmer feeling lever. Still stopped very well, just a bit more effort.   
Charlie

Offline wicks

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Re: De Linked brakes
« Reply #20 on: October 25, 2024, 01:26:04 PM »
Going to try your solution wirespokes, thanks for that.  What did you do with the rear? One clean line to the caliper steel line would be nice.

I just have a feeling that a double switch banjo bolt at the MC would be a good idea, so each caliper gets a full supply or pressure from the MC.

Seems like the original line from front MC would make it to the left caliper with a different routing...and there's room for another line behind the fairing there.

Trying to find a longer switch banjo...could always cut the wire and join it to the stock wiring without cutting anything.

I'm also going to sand the glaze off the rotors and try ferodo platinum pads. The brembo organics don't seem to grab well on these iron discs and are increasing the glaze/polish on them.  The brembo pads work great on the 1000s brakes but I think those are stainless rotors (and the setup is better engineered 16 years later so they work a lot better than le mans system).

Wish someone made floating disks for these old LM wheels...
« Last Edit: October 25, 2024, 02:04:12 PM by wicks »
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Online Antietam Classic Cycle

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Re: De Linked brakes
« Reply #21 on: October 25, 2024, 02:10:29 PM »
Charlie

Offline wicks

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Re: De Linked brakes
« Reply #22 on: October 25, 2024, 02:41:19 PM »
Ahh magic thanks Charlie. Ordered up those floating discs. And this replacement rear M/C: https://hmb-moto.de/Master-cylinder-PS-12-T3-Le-Mans-1-2-3-etc

Also found a front switch with room for two banjos from Brembo in italy: 0626MQ30 is part number
And from MG ordered all new calipers and an extra right front brake hose

*need to find:
- another right front brake hose holder/guide (so I can add one for the the left hose)
- correct hose hopefully original type to connect new rear master directly to the rear caliper hard line (which I'll also replace). Maybe one of the existing miscellany of lines in the tractor currently can be used, have to have another look at the linked setup.

DOT 4 is good for all this no? Remember some noise about DOT 3 vs. 4.
« Last Edit: October 25, 2024, 03:51:08 PM by wicks »
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Offline John Croucher

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Re: De Linked brakes
« Reply #23 on: October 25, 2024, 06:25:45 PM »
http://vintagebrake.com/

This is a great resource for brake systems. 

Offline wirespokes

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Re: De Linked brakes
« Reply #24 on: October 25, 2024, 07:31:49 PM »
 When I was delinking the G5, I found a stainless brake line set-up with one line that branches above the fender to both calipers. It doesn't look the greatest, but works well. A friend, on the other hand, on his T3 did something different. His front master has a flex line to a splitter at the lower triple tree which had the hydraulic brake switch and the line going to the right caliper. He sourced a rear splitter and mounted it at the lower clamp because it has four ports instead of three. He was able to mount a right side flex line on the left up to the splitter, just like the right side. He did have trouble with one of the lines sealing, but a special expensive seal from McMaster Carr took care of that. It looks very stock and I like the look of that more than mine.

I've used the 12mm master and the 15. Like Charlie said, they both work, but with the 12 it's critical getting it totally and completely bled. e Once all the air is gone, the brakes work great with normal lever travel.

Offline wicks

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Re: De Linked brakes
« Reply #25 on: November 08, 2024, 02:43:31 PM »
The rotors from HMB work amazingly well. I set them up with new calipers, HH pads, new hoses (double the right side hose) and a dual banjo. Works like modern bike brakes. Centered the calipers perfectly (required two spacer washers per bolt on both sides. Only issue is the travel of the original front master at 12.7mm is a bit too much - almost too easy to pull and gives too much "resolution" for normal trail braking etc. Must try to find a solution for that while keeping things stock looking.

The rear with a new caliper and the new master from HMB is still useless, so ordering a rear rotor from them and will use HH pads. May need to delete the original integrated brake union and fit a direct line there.

Will need a solution for rear brake switch though - looks like not enough room for a switched banjo bolt. Any ideas?
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Offline wicks

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Re: De Linked brakes
« Reply #26 on: November 09, 2024, 10:44:27 AM »
I made a dual hose guide...but just realized it's gonna get crushed by the torque on the lower tree bolt...need to remake out of steel rather than aluminum wire...or if someone is good with torches and such I'd pay a good fee ;)





Oh also found from HMB rear brake switch banjo bolt that fits, also ordered their rear rotor.

On the front lever travel, is this from MG the best we can do (closest to stock style)?  https://www.mgcycle.com/index.php?main_page=product_info&cPath=110_112&products_id=3219

Also wondering if the original front left hose is the best to replace the rear circuit with a direct line - it's a bit long maybe but can fit. Happen to have a new one.

FYI the all metal locknuts as original on the rotor bolts that people don't seem to stock: https://belmetric.com/conical-lock-nut-class-10-steel-din-980v-iso-10513-7042/?sku=NCLH8CLZ

I am using a power bleeder (porsche 964 happens to have the same cap size), working well so I think the front end is clear of air. Will do it again after riding some, maybe there's a bit more hiding.
« Last Edit: November 11, 2024, 09:51:44 AM by wicks »
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