De-linked rear master - 87LM

[wirespokes]

I'm gradually getting out the kinks in this 87 LeMans. The handling was heavy and slow and what finally fixed it was going with the tire sizes recommended for the 88 LeMans. It made a world of difference!

The clutch hub had gotten notchy which made for poor shifts and difficulty getting into first. Since it had the 2mm clutch the only solution was replacing the hub, clutch plates, intermediate plate and the springs.

The bike is transformed.

But there's one more problem left. The PO de-linked the brakes and I'm  happy with them like that so don't rag on me for how good the linked system is. As I see it, linked brakes are an automatic thing - like automatic choke, spark advance or automatic transmissions. I'd rather not have a rear brake that automatically applies a front. I can do that manually. There are times I want, and need, just the rear - like coming down my down-hill driveway that curves to the left. It's got some gravel on it and I don't want or need the front brake at that time.

Anyway, the PO de-linked the brakes, but didn't change the rear master. So it's too large for one caliper.

I was told the V65 front brake cylinder mounts up like stock - but I haven't seen one for sale yet. I'm thinking of possibly having it sleeved for the V65 repair kit.

What have you done? I think the stock size is 15mm and it needs to be more like 12mm.

[Psychopasta]

What problem does the original cylinder give you? Is the rear brake now too abrupt for you?

[Pop]

I thought about doing it to my 65, just seemed like I was asking for trouble. I just left well enough alone. I originally blocked off the front but it felt wrong, too much rear.

[Antietam Classic Cycle]

Anyway, the PO de-linked the brakes, but didn't change the rear master. So it's too large for one caliper.

I was told the V65 front brake cylinder mounts up like stock - but I haven't seen one for sale yet. I'm thinking of possibly having it sleeved for the V65 repair kit.

What have you done? I think the stock size is 15mm and it needs to be more like 12mm.

Do you mean a V65 rear master cylinder? That would be the same as you already have - a PS16. Someone ("pressureangle"?) a while back mentioned using a V50 II  front master cylinder - that was cable operated and mounted under the gas tank. AFAIK, that one is NLA new.

[Moto]

What have you done? I think the stock size is 15mm and it needs to be more like 12mm.

Haven't done it, but Guzziology has an excellent discussion of the possibilities.

Moto

[Triple Jim]

What problem does the original cylinder give you? Is the rear brake now too abrupt for you?

Good question.  Brakes work on fluid pressure.  De-linking does not change anything about the fluid pressure when applying the rear brake.  In other words, for a given rear brake pedal force in the original "linked" system, the pressure in the line is still exactly the same now.  The system was designed to prevent over-braking of the rear wheel.

[Dukedesmo]

I delinked the brakes on my LM2, don't know if yours uses the same setup at the rear but I used one of these; http://www.ebay.co.uk/itm/Ducati-750-860-bevel-drive-NOS-rear-Brembo-brake-master-cylinder-with-NO-SWITCH/360446989620?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649 It's a Brembo 12mm as used on single disc setups on bikes of the same era and is the same design.


I did have to do some minor engineering to fit it, as it is designed to sit the other way around (counterbore on wrong side etc.) but as all the holes line up and the same dimensions etc it not only fits nicely but looks good and works perfectly too.


At the front I fitted a Brembo RCS15 to operate both discs together.


I couldn't get on with the linked system because the front (hand) lever didn't give me enough braking and if I want combined braking I can do it manually anyway. 

[Groover]

I thought the '87 had 16" front and the 88 has 18".. What sizes are working best for you? Did you swap the actual wheel?

Not sure about the braking issue, but looks like you have some great help on this so far.

[kfz]

im running a GSXR750 (old oil cooled) on my de linked LM.  AS said I think its 12mm and it works well but need brackets welded to the frame. to hold the pivot. And a new brake pipe of course.

I considering going back to links on the grounds that Guzzi spares supply is much more reliable and i quite like the links anyway.

Kev

[wirespokes]

Wow! Thanks for a bunch of great replies! I'll check up on the data you've given today.

To answer some questions --- yes, the 87 LM came with a 16" front. A PO changed it early on - probably around 1990. When I got the bike last Nov, it had a 110x80 18 up front and a 130x80 18 rear. It had heavy steering and was pretty sluggish. I had to work at cornering. It also wasn't holding air really well, which complicated matters.

There were complications in steering geometry with this model. The early 85LM came with the 16" front and no modifications to the steering geometry (same as earlier models). Later in 85 the factory came out with steel triple trees with more trail to slow down the steering. Shortly after, the triples were made of aluminum. So my bike was converted from 16 to 18 (which slowed steering) and has modified triples (factory stock) with more trail that also slow steering. I was thinking I needed to source a set of early 85 triples, but Dave Richardson said the difference between the early and later was minimal, and besides, the early ones are almost impossible to find.

It's now wearing new Shinkos (great tires, and cheap!) that even look great, but best of all, it feels like it's got power steering. It flicks over so easily - it's a dream to ride. 100x90 front and 120x90 rear. I would have gone with a 110 rear except the rim is too wide and the 120 is the smallest recommended for that width. I'm extremely happy with it as it now is. So the tires on it now are what are recommended for the 88LM that came with an 18" front.

My front master cylinder was changed and it feels fine. From what I've seen, front masters tended to be too large, so adding a second caliper evens things out nicely. But the rear in the linked system running two calipers winds up being too large for just one caliper.

That's an interesting thought that the proportioning valve should take care of the situation if one of the calipers is removed. Mine still has the valve, but the brake pedal barely moves at all. There's not much control - between some brake and skidding. I'd remove the valve (extra complication) but the brake light switch is plumbed into it. AT this point it doesn't seem the valve is helping, or making an difference at all.

Charlie - yes, that's it! A V50 under-tank master was what I'd heard of before, but didn't remember the details. I've heard that works perfect, but haven't seen one for sale. I'll probably go with one of the other solutions.

One of the things I don't like about linked brakes is there isn't 100% braking up front. When the rear brake is applied, only a percentage of the front is used. Guys say they really like the fact that with linked brakes the whole bike squats rather than dive. For one, I don't mind dive. Secondly, that's what happens when you get on the brakes really hard - it's just how it is. Extreme maximum braking will actually lift the rear wheel off the ground, which puts all the weight on the front, of course, compressing the front end. I think linked brakes work in a majority of situations and is probably a good solution for a lot of guys, especially new riders. When linked brakes were introduced, I believe they were intended to solve the problem of riders who feared using the front brake and mostly used the rear.

I've been riding the T3 (linked) for a year and a half, and it only bothers me in a few instances. I will de-link it at some point, but it's nothing urgent.

[JBU]

I have a T3 with delinked brakes.  I had an 11mm MC for the rear but it was like stepping on a rock I changed it to a 12mm and now it's just right. 

[Stevex]

I de linked my LMII and fitted a 12mm master from an 860GT.
Just had to have a bit of machining done so it fitted the right way round.

[redrider90]

Good question.  Brakes work on fluid pressure.  De-linking does not change anything about the fluid pressure when applying the rear brake.  In other words, for a given rear brake pedal force in the original "linked" system, the pressure in the line is still exactly the same now.  The system was designed to prevent over-braking of the rear wheel.

Jim,
How does the linked system work?  It regulates the front left and rear disk via what mechanism.  How does that system effect the relationship between front and rear.
If the linked rear MC is 15 mm and others who delinked moved to 12mm and one to 11mm who reports it felt like a rock..... meaning he clearly was not getting enough pressure on the rear caliper, then what is the reason for moving to 12 mm MC?  Anybody out there who delinked who kept the stock rear 15 mm MC? It seems that you are correct that the rear MC does not need changing.  The changes in delinking has to be done at the front where your MC has to be changed to accommodate 2 disks vs one disk. As an aside I love the linked system. It was ABS before ABS came available on MCs. It's my savior when I need just a bit of braking if I enter a corner to fast.

[Triple Jim]

Jim,
How does the linked system work?  It regulates the front left and rear disk via what mechanism.  How does that system effect the relationship between front and rear.

It varies between Guzzi models.  Some sense swing arm position to take load on the rear tire into the equation.  My Mille just has an automotive type proportioning valve.

It seems that you are correct that the rear MC does not need changing.

If you want a lot of rear brake with light pedal pressure, the stock rear master cylinder is too large.  I don't like a lot of rear brake with light pedal pressure.  It's a recipe for locking the rear wheel in an extreme stop.  In a stop like that, the vast majority of stopping comes from the front wheel, and the rear wheel isn't far from coming off the pavement.  Any more than slight rear braking in that situation will cause a locked rear wheel and the resulting loss of directional control.

When the system is "de-linked" and retains the stock rear MC, the rear brake will seem surprisingly lame compared to when it was "linked", and I think that's why a lot of guys then go to a smaller MC.  I prefer a lame rear brake, as long as I can lock the rear wheel with heavy stomp, in the event that I lose front wheel braking for some reason.

[wirespokes]

Triple Jim - You got it! Exactly!

I may get used to the rear as it is, but think it would be better with a smaller master.

Redrider - I think JBU got a little mixed up on his conversion. The original rear is something like 14 or 15mm. That is the one that feels 'hard as a rock'. Because the master is designed for two calipers, it now takes half the distance to activate only one. The ratio is all off and there's not much leverage. It's hard to think with this logically. But believe me, I've been through this a number of times and this is how it works. When the master is too large, there will be very little movement of the lever and will require a LOT of effort to really clamp the brakes on hard.

Moving to a smaller master will give more travel in the lever and more leverage. It will be significantly easier to clamp the brakes on HARD.

The downside of a small cylinder is if it's too small, lever travel will be too great. There's an optimum where you get maximum power with acceptable travel. On a hand lever, that's super important it not come clear back to the grip before lock-up.

If you can get a good 'feel' on the rear brake then the smaller master (about 12mm it seems) is the way to go. If you're concerned about possibly locking the rear up, then the large (original) could be the right choice since it takes a fair amount more pressure to do that.

Dukesdesmo - the LM4 uses a master more like the GSXR with the remote reservoir. I'd have to move some stuff to make that one work with the attached reservoir. Thanks for the link - I'll probably get one like that for the T3.

KFZ - could you post some pix of your set-up? I'm thinking there must be a way to mount a lever without welding one to the frame. I think those GSXR masters are mounted vertically, not horizontally. That's an interesting thought. I'm still trying to figure out a lever arrangement to make that one work. I sort of recall someone mounting a master like this horizontally near the foot peg.

[JBU]

Sorry no confusion.  Yes the original rear MC of a linked system is 15mm.  When delinked and keeping the 15mm the rear break was almost useless.  Pedal to the ground with little stopping power.  I went with an 11mm but this had zero feel, stepped up to a 12mm and now have good stopping power and nice feel.

[Orange Guzzi]

Jim,
How does the linked system work?  It regulates the front left and rear disk via what mechanism.  How does that system effect the relationship between front and rear.
If the linked rear MC is 15 mm and others who delinked moved to 12mm and one to 11mm who reports it felt like a rock..... meaning he clearly was not getting enough pressure on the rear caliper, then what is the reason for moving to 12 mm MC?  Anybody out there who delinked who kept the stock rear 15 mm MC? It seems that you are correct that the rear MC does not need changing.  The changes in delinking has to be done at the front where your MC has to be changed to accommodate 2 disks vs one disk. As an aside I love the linked system. It was ABS before ABS came available on MCs. It's my savior when I need just a bit of braking if I enter a corner to fast.

The master cylinder does not care how many calipers it is connected too.  It is the total surface area of all the pistion/pistons it is moving.  The comment about going from 15 mm to 11 should have made the m.c. squishy, not wooden.  with good braking/poor feel.  A wooden feel is caused by to large a m.c. piston.  Giving you a wooden fill and no braking power. 

The "valve" is  a proportioning valve.  It redirects some of the master cylinder fluid pressure to the front brake caliper after it passes a spring controlled ball and reducing the pressure. 

There is a proportioning/sizing chart on the Vintage Brakes web site. 

I delinked the brakes on my 2003 California, duel disk front.  15mm front, 12 mm rear.  I have 1 finger brakes on the front and rear that takes a good push on the peddle to lock the rear. 

[redrider90]

Triple Jim - You got it! Exactly!

I may get used to the rear as it is, but think it would be better with a smaller master.

Redrider - I think JBU got a little mixed up on his conversion. The original rear is something like 14 or 15mm. That is the one that feels 'hard as a rock'. Because the master is designed for two calipers, it now takes half the distance to activate only one. The ratio is all off and there's not much leverage. It's hard to think with this logically. But believe me, I've been through this a number of times and this is how it works. When the master is too large, there will be very little movement of the lever and will require a LOT of effort to really clamp the brakes on hard.

Moving to a smaller master will give more travel in the lever and more leverage. It will be significantly easier to clamp the brakes on HARD.

What about moving to a rear caliper that is larger? That is what I did with the Mille on the front right. I took off the smaller F08 and replaced it with an F09. The F08 was wooden and required a big handful to get it to stop. I had no "feel"to it. I was not lacking for a hand as  I am 6'5" but I hated it. Putting the F09 the front was like making the front master cylinder smaller. Am I correct? I do know that with the F09 it is a 2 or 3 finger stopper on the single right brake with the left front brake linked. The difference is nothing short of dramatic.
As I under stand it the older SPs had a rear F09. The F09 is now available again through MG cycles. The older F09 is an awful design with 2-6mm bleeder valves that need to be opened and closed every year hence the freeze and break off. I think the newer uses an 8mm nipple.
This is what MG says about the F09

 "F09" caliper, twin opposed 48mm pistons. This is a reproduction caliper based on the discontinued Brembo F09 from the 1970s and 1980s. Guzzi used these in rear brake applications on various models in different markets, and they were popular as a modification on many others. Caliper comes complete, but no pads are included. The originnal F09 caliper was sometimes used to improve the master cylinder ratio on early single disk 850T and Eldorado with ~15mm hand master cylinders. Similarly, these calipers can be used to improve the master cylinder ratio on models where the integral braking system has been disabled and the rear caliper is driven by a ~15mm foot master cylinder. The original F09 was also used by Moto Guzzi as a component in the integral braking system, for USA, this was limited to early versions of 1000SP.
This caliper fits front right when the caliper is mounted in front of the fork, and rear when the caliper is mounted above the axle."

[wirespokes]

Orange Guzzi - what 12mm master did you go with?

Red - that's an interesting solution and worth looking into. Thanks!

[blackcat]

I delinked the brakes on my LM2, don't know if yours uses the same setup at the rear but I used one of these; http://www.ebay.co.uk/itm/Ducati-750-860-bevel-drive-NOS-rear-Brembo-brake-master-cylinder-with-NO-SWITCH/360446989620?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649 It's a Brembo 12mm as used on single disc setups on bikes of the same era and is the same design.


I did have to do some minor engineering to fit it, as it is designed to sit the other way around (counterbore on wrong side etc.) but as all the holes line up and the same dimensions etc it not only fits nicely but looks good and works perfectly too.


At the front I fitted a Brembo RCS15 to operate both discs together.


I couldn't get on with the linked system because the front (hand) lever didn't give me enough braking and if I want combined braking I can do it manually anyway.

Can u post a photo of the minor engineering you did for the rear mc? thanks.

[Dukedesmo]

Didn't take any pics of the progress but basically the MC I used was originally for Ducati 860 and others but was fitted the other way around so had both the counterbore for the allen/hex fixing bolt and the locating screw on the other side.
 
To fit it in the position that the original sat I needed to 'flip' it so needed (maybe able to get away without?) a counterbore for the head of the screw to sit in on the non-counterbored side, so I drilled it with a suitable counterbore and then made a bush for the other side so that it had sat nice and solid.
Then need to remove and 'flip' the other locating screw (by the pivot) and the pivot bolt which IIRC (at least one of them) required a thread cutting into the body of the MC? That done it can be fitted to the bike as the old one was, I used a banjo bolt pressure switch for the brake light switch as my bike had a pressure switch on the (now removed) splitter valve.
Basically you need to make this;
 

into this;



Unless of course you can locate one of the correct orientation?

[Antietam Classic Cycle]

750 and 860 Bevel Ducatis have a drum rear brake, so that master cylinder must be for some other model.

[guzzista]

Right you are, Charlie. So perhaps it's the  Darmah, Darmah SS or perhaps the fancy version of the parallel twin 500 , the Sport Desmo 500. I used to have a 900 GTS with Darmah rear swingarm and  rear disc brake . The  rear master cylinder had to have a Bracket welded to to the fame in order to attach it

[Dukedesmo]

Well it was used on an old Ducati with rear disc brake, but likely also on other Italian bikes of similar vintage?


The important part is that the mounting holes all line up and the linkage goes straight on so it fits, with some modification.   
 

[wirespokes]

I picked up a dual bleeder caliper thinking the duals are all 48mm, but they're not. This one is 38. Are all the 48s stamped 48 on the back? How can you tell without measuring the pistons?

[Antietam Classic Cycle]

I picked up a dual bleeder caliper thinking the duals are all 48mm, but they're not. This one is 38. Are all the 48s stamped 48 on the back? How can you tell without measuring the pistons?

The circular area of the caliper body is a bit larger on an F09, that's how I tell them from an F08. I think you'll be able to see the difference in these photos.

F08:
http://www.mgcycle.com/index.php?main_page=product_info&cPath=110_115&products_id=1034

F09:
http://www.mgcycle.com/index.php?main_page=product_info&cPath=110_115&products_id=4602

[salsaman1964]

I've been running a Brembo F09 on my Lemans 3 with delinked brakes and it works brilliantly with the standard 15mm master cylinder.  Highly recommended:thumb: