Delinked Brakes

[sirbike]

—- as I get questions I am adding, editing and clarifying this post to keep the information in one place—-

I delinked to simplify the system

I delinked my VFR to reduce potential problems, and because I had some braided lines laying around that happened to fit.
So when I bought the 2006 ST1300 I considered the idea until another 2006 ST1300 went up for sale as a result of damages caused by a smc failure. Then I thought let’s simplify this. Anyway I rode 9,000 miles linked. (Previously rode 15,000 ST1100ABS II)
I delinked the 06 this winter.
Front master cylinder connects to outer front pistons.
Rear mc operates three pistons in rear caliper, with new oil passage drilled from middle piston to passage between outer pistons.
Edit, Capped the brake line port to the rear caliper middle piston with appropriate size bolt and crush washer.
Capped the front middle pistons and drilled a vent hole through the bleeder to the outside to ensure no pressure build up from heat in middle piston. End edit.
Essentially the known formula for the Blackbird.
What I find riding is that

1. the rear wheel takes more effort to lock up which I happen to appreciate.
   edit 3/1/21, After more miles and a couple more deer, I’d say not much difference if at all. Certainly within the realm of appropriate. end edit
2. I use the rear brake lever more.
3. The front brake lever by itself does not slow the bike down as quickly, presumably because the brake system is not activating the rear braking via the smc and subsequently the front inner pistons.

3a. Using the front and rear levers together stop the bike just as fast as linked.

1. The front wheel can be locked up more or less the same as on similar bikes that I’ve owned like ST1100 or Concours 1000
2. I kinda miss the linked brakes for the last few feet of braking prior to a stop on pavement because I like the landing gear down on both sides while still having the advantage of front and rear brakes applied.
3. I feel safer delinked on gravel coming to a stop where I make a point of using more rear brake bias.

I will test adding in one middle front piston hoping to get a lighter effort.
My ST1300 works fine with 4 but I am curious how 5 would feel.
Just my opinion, but I overcame the fear of delinking when I thought about the 70,000 miles I rode on standard ST1100s with no problems and a thorough study of the ST 1300 system and its comparison to the ST1100, ST1100ABSII, Blackbird and VFR.
Post note.
Remember, I did this to simplify things.
I had the 03 abs just about ready to ride last night when guess what?
The proportional control valve leaks out. Geez! Good thing I delinked the 06 and had a spare valve.
This is a thread where everyone is right.
So let’s keep the peace and saves the proxy wars for the oil thread.

Edit 6/8/20
I finally tied in a fifth piston by drilling a hole to intercept the passage between the outer pistons on one caliper and ran into the same problem that in had in a similar project with my VFR800. After a lot of head pounding it occurred to me that there could be air under the block off bolt that I used.
I cracked that bolt and sure enough a small amount of air came out. There was just enough air to make the lever just soft enough to confuse whether it was a master cylinder to slave cylinder ratio thing or air in the system. I should have stuck to the logic that the lever would move more until the pads hit. Beyond that, within reason, the lever has hit an unmoving wall regardless of ratios.
I had linked the three rear pistons by drilling internally. That brake felt OK. I cracked the bolt while a friend pumped the pedal. Now the rear brake feels excellent.
With 5 pistons working up front the lever travels a little further until the pads contact. Beyond that the lever feel is correct.
I can lay down rubber with two fingers. Not too easily, just right for me to be a definite two finger operation like my linked bike got me spoiled to.

 

[Catmandu2]

Just a point of curiosity,,, Honda has had linked brakes on many models over the years, it seems. Have they continued to use linked systems on recent models ?? Cat'

 

[sennister]

THIS IS A TERRIBLE IDEA!!!

Just kidding.... Neither of my '93 ST1100 bikes have linked brakes. They ride just fine. I agree it is way easier to bleed and is more reliable without all the extra bits in the mix. That said, I don't think I will personally delink the brakes on my 1300. It is interesting to see that someone went through the effort.

I didn't see you specifically mention it but I assume the 06 is a non-ABS model.

 

[bstig60]

I have owned 3 Goldwings over recent years in addition to my ST1300. All had linked brakes, never had any problem with them. Do the proper maintenance and things will work as designed.

 

[sennister]

I have owned 3 Goldwings over recent years in addition to my ST1300. All had linked brakes, never had any problem with them. Do the proper maintenance and things will work as designed.

I haven't had a lot of problems with them, just that it makes a brake pad change take twice as much time. I did have a SMC fail right before a trip. The piston got stuck and the front caliper mount would rattle. The biggest problem was that the rebuild kit was on nation wide back order. I got back on the road by ordering the entire caliper mount. It was 4 times the cost for a part that a delinked bike wouldn't have an issue with. There is a bit of a design issue, more so with the earlier ones where water gets into the SMC. Later they revised the caliper mount to include a drain hole to help prevent this. If you are a fair weather rider you were less likely to have a SMC issue. Simple maint of flushing the fluid every other year or so would prevent problems. The more you ride in more adverse conditions the bigger the problem.

 

[sirbike]

I didn't see you specifically mention it but I assume the 06 is a non-ABS model.

Yes, my 06 is non ABS.

To answer another question, I filled the SMC with brake fluid to keep it from hammering the end of its travel. And to have a spare that could be returned to functioning.

Just a point of curiosity,,, Honda has had linked brakes on many models over the years, it seems. Have they continued to use linked systems on recent models ?? Cat'

Without checking, iirc they have mostly continued.
Interestingly to me the 2014 VFR discontinued linked brakes.

 

[sennister]

Yes, my 06 is non ABS.

To answer another question, I filled the SMC with brake fluid to keep it from hammering the end of its travel. And to have a spare that could be returned to functioning.

So, you filled it with fluid and caped it I take it? That rattling was annoying on my bike when the piston was stuck. I assumed you did something to lock that caliper mount in one place.

 

[heffly]

A machine is just an experiment in progress. Its never a final design. My ST is fixing to have some design alterations. Message sent!!!

 

[sirbike]

Yes capped. No mechanical lock so to speak. Just kept from moving by being filled with brake fluid.

Another question I received
I used the oem rubber line that goes from rear mc towards the rear caliper inner piston and switched that to the hard line that feeds the outer pistons that was formally fed from the front/proportion control valve.
I used a spare part as a spacer to take up the the space the other junction block was in. Might have used a prettier part or stack of washers as a spacer if I knew it would be on display. But I wasn’t going to hardware store for that.
SMC pics here.

 

[sirbike]

BTW my initial investment risk was drilling a spare rear caliper. I swapped the rear brake lines and left everything else in place and tested the bike before I removed link dedicated parts.

 

[Igofar]

Yes, my 06 is non ABS.

To answer another question, I filled the SMC with brake fluid to keep it from hammering the end of its travel. And to have a spare that could be returned to functioning.



Without checking, iirc they have mostly continued.
Interestingly to me the 2014 VFR discontinued linked brakes.

The rattling/hammering end of its travel, means the piston is stuck halfway down the bore, did you remove the piston assembly entirely?

 

[mello dude]

I'm guessing about 20% of VFR owners do a complete stripping of the linked brake system (yes, SMC in the trash) and replace with other standard OEM Honda gear that makes it a standard split system. (I did mine.). With all the noise on the ST SMC, if I grab one, the strip out will be at the top of the to do list.

BTW - the latest VFR 800 bikes have separate brakes.

 

[ST Gui]

IIRC somebody talked about putting a wedge or clamp in play to take an SMC out of play when it failed on the road. It's a worst case scenario idea but maybe keeping a dedicated wedge and a couple of zip ties might be a good idea for the if/when.

Do the proper maintenance and things will work as designed.

This is how I'll roll. I'm fine the the LBS. But as it adds some complexity and expense and is a potential liability if neglected I wouldn't mind seeing it replaced with an electric unit incorporating a failsafe. And maybe an idiot light the functions as does an oil pressure light. This would reduce the likelihood of an SMC becoming a

.

 

[sirbike]

I

The rattling/hammering end of its travel, means the piston is stuck halfway down the bore, did you remove the piston assembly entirely?

That is good to note.
In my case the smc was in good working condition. I left it in place and filled and capped the smc as means of fixing the bracket in place vs having the bracket/smc piston/etc hammering the end of its travel.
see picture in post #9
I figure it was designed to push on fluid with the load spread out on the cylinder/piston surface area. If the seal fails years down the road it won't affecting braking, I'd just take care of it then. There is probably another way to fix it in position, this worked well for me on the VFR.
An aftermarket fixed bolt on bracket is made for the Blackbird

 

[TerryS]

I

My smc was in good working condition. I left it in place and filled and capped the smc as means of fixing the bracket in place vs having the bracket/smc piston/etc hammering the end of its travel.
see picture in post #9
I figure it was designed to push on fluid with the load spread out on the cylinder/piston surface area. If the seal fails years down the road it won't affecting braking, I'd just take care of it then. There is probably another way to fix it in position, this worked well for me on the VFR.
An aftermarket fixed bolt on bracket is made for the Blackbird

I have VFR SMC and compared that to the ST1300, overall dimensions are identical, barring the diameter of the cylinder. I'll make a great leap in logic and suggest on that basis it is likely that any part made to immobilise the SMC on a CBR1100XX will probably also fit both the VFR and ST1300. Honda does like to re-use parts across as many different models as possible.

 

[heffly]

In case you all don't know. IF you experience a lockup the center bleed valve on the rear caliper releases the brakes. In my case it melted the SMC hose off the caliper.

 

[Shawn K]

What I find riding is that

1. the rear wheel takes more effort to lock up which I happen to appreciate.
2. I use the rear brake lever more.
3. The front brake lever by itself does not slow the bike down as quickly, presumably because the bike brake system is not activating the rear brake and subsequently the front inner pistons.

The difference you're noticing is because you've altered the hydraulic leverage ratios. Your modifications added/removed pistons (and therefore surface area) in relation to the master cylinders that operate them.

Too low a leverage ratio causes brakes to have a sort of "wooden" feel and require more physical effort at the lever (which is what it sounds like is happening with your rear brake). Increasing the ratio gives you greater mechanical leverage (more stopping power), but unless you modify the brake lever to increase the distance between the lever's pivot point and the master cylinder piston, you won't get the throw you need at the piston to move the pads far enough to take advantage of the increased hydraulic leverage.

If I were going to de-link my ST, I'd be comparing bolt patterns of other Nissin calipers from other bikes to see if I can find a caliper set that will bolt on. Then, I'd make sure to buy the master cylinder and lever set that came with that bike, too. Off the top of my head, I'd be looking at pre-radial caliper CBR1000RR's as a starting point.

(I tried this before on my 1st-gen linked brake GL1200. Learned quite a bit from trial and error, and the fine folks at HEL Performance.)

 

[ST Gui]

The difference you're noticing is because you've altered the hydraulic leverage ratios.

A similar thing happened when I added a caliper (and rotor) to my single-disc 750-K4. The brake lever when straight to the grip with no resistance whatsoever. I never tried to ride it like that. I used a Yamaha master cylinder that looked like a clone of the Honda's and made the brakes great again. I don't know how the ratios compared to what Honda would have used had they added a caliper but I was very happy.

 

[Shawn K]

A similar thing happened when I added a caliper (and rotor) to my single-disc 750-K4. The brake lever when straight to the grip with no resistance whatsoever.

That's because by adding the second caliper, you doubled the piston area without a requisite change to the master cylinder piston size. As such, you leverage ratio doubled, but now the pistons in each caliper only moved half the distance (which is why your level came all the way to the bar... the brake pads never reached the rotors). That's why the "pivot distance" in the lever is important in the equation as well.

Without seeing the actual parts you used, it sounds like your Yamaha master cylinder was probably of larger diameter than the Honda unit. That made up for the increased piston area by pushing more fluid per stroke of the brake lever.

Just wait until you dig in to the finer points of piston seal size, piston coating material, lever length, pivot distance, and radial vs. axial master cylinders!

 

[heffly]

I was thinking the ratio is volume, ie..the master cylinder rod displacement as rod diameter and travel, compared to volume of the calipers. Then leverage and total pressure.