another brake delinking (approach for the front)

[Worfje]

Just want to share my progress on delinking my bike.

 

I got some suggestion / ideas from this forum on how to cope with the 'bracket sub. assembly' aka 'front left brake caliper mounting bracket including a secondary master cylinder'.

One suggested to fixating the pushrod of the secondary master cylinder with some kind of epoxy and another suggested to make a bracket between the fork leg and the two mounting holes which normally hide the SMC from sight. Epoxy... not my thing here.

 

This was my go at it the bracket between fork and interface near SMC:

(also credits to FreeCAD, love that software!)

 

In short, I wasn't happy about how 'off center' the bracket is vs. the force that it will receive during braking.

Next to that, these two M6 bolts, they don't give me that warm feeling if they receive 250 N - 400 N.

 

I considered a rod that replaces the moving parts in the secundairy master cylinder on which the pushrod could be fixated:

(pushrod to be attached on left-top, right slides into the cavity of the master cylinder and circlip would hold the rod into the cavity)

 

Which could have worked and would have been cheap.

But, it would 'act' a bit differently since the opposing force would not be from brake fluid, but from hard contact in the 'cup' of the cavity of the master cylinder.

Next to that, why not make a full replacement in which I would be able to slide on my original brake caliper... 

 

Well, for starters I would need to reserve engineer the bracket regarding mechanical distances / offsets / volume. A lot of effort.

So, I started looking for Honda models that also applied the same 'generation' of Nissin brake calipers (which also would have CBS).

Which I did via lookup of caliper parts on cmsnl.com.

I ended up looking at a Honda CBR1100XX from 1997 - 2006, which proved to have 'moved out' the secondary master cylinder from the front left brake caliper mounting bracket, lovely!

But unfortunately, after receiving a second hand, the mechanical offsets did not come close to the VFR800 (3.5 mm difference of caliper placement in the direction of the wheel axle)... 

 

(next to that, there seemed to have been an issue with the motorcycle, since below is very abnormal wear):

 

So, back to square one on how to tackle this. More tomorrow!

 

 

 

[VFR750F3]

I applaud your effort. You could always install a larger bolt and ie M8 or just use 12.9 M6.  I fixated the rod also. I was not happy with the delinked brakes.  Even after rebuilding the calipers and getting another set of calipers with new seals the center piston was slow to react ie come out of the bore.  I also warped several rotors in the process.  I hope you have better luck.  Do yourself a favor and get F3 fork legs with some nice gold 4 pistons Nissin calipers and a 14 or 16 master cylinder depending on which Nissin calipers you get.

[Captain 80s]

Or VTR1000F fork lowers and some RVT1000R calipers.

[Terry]

I quite like my linked brakes but I would have thought a sleeve between the SMC casting and the clevis was a simple way to stop the SMC moving, or filling the SMC bore with epoxy. Keeps all of the forces in line.

 

But I would also blank off the connection back to the rear calliper centre, ditch/cap the fluid connection from the rear to the SMC, and for S&G one could drill the front calipers to connect all 3 pistons, and use a larger bore front MC to match.

[Captain 80s]

I would think if you are going thru the trouble of de-linking, eliminating the weight, including unsprung weight bolted to a godam fork leg no less, would be a fairly high priority.

[Worfje]

Thank you for your responses.

If I did had not hardchrome the fork tubes and bought the fork cartridge from DMr, upgrading the forks might probably have been the way to go. 

 

Not sure why delinking would be directly related to warping a brake disc. 

 

I promised more today, so let's continue:

 

So, the CBR1100XX caliper mounting bracket was a dud... I was reluctant to made reverse engineer the caliper mounting bracket... what if I could find a motorcycle that would have the Nissin calipers on the left side without CBS?

 

I searched for all models that used the the same right caliper mounting bracket, thus product number 06453-MBG-405.

This included (again) the CBR1100XX, GL1800, NT650V... and what do you know, the NT650V has a similar caliper mounting bracket without any secondary master cylinder with part number 45190-KFG-641. Lovely.

I ordered it and regarding offsets / distances of the mounting points to the fork and guide pin offsets it is identical to the brackets on the VFR800FIW.

 

(shown on left is VFR800FIW front right bracket, shown at mid is VFR800FIW rear bracket and shown right is NT650V front left bracket)

 

The existence of this NT650V bracket made reverse engineering a lot easier! I 'only' had to get all dimensions correctly by combining information / measurement from the fork leg, the original caliper mounting bracket with secondary master cylinder and the caliper mounting bracket from the NT650V. So, with some luck the 8.00 mm diameter aluminum rod were near perfect fit for the bushes in the fork leg, allowing for a relatively precise distance measurement:

 

 

Same for caliper mounting bracket, which I fitted with pins for desk wheels that have some M8 thread:

 

 

By combining the position measurement from fork leg, NT650V left bracket and the VFR800 left bracket I could conclude the dimensions required for a custom bracket:

 

 

 

After several iterations (around 10), I converged to this:

 

 

 

 

I ordered it to be milled from 7075 aluminum and are now awaiting delivery. 

[Worfje]

For information: the rear VFR800FIW caliper bracket seems to be identical to the left NT650V caliper bracket, but this does not hold for the 'slit' which is there for the brake disc. 

This is in the a bit in line with the difference in thickness of the brake disc between rear and front. 

The slit for rear is 9 mm wide and 8 mm wide for front. 

[Captain 80s]

7 minutes ago, Worfje said:

Thank you for your responses.

If I did had not hardchrome the fork tubes and bought the fork cartridge from DMr, upgrading the forks might probably have been the way to go. 

 

My last comment and I'll leave you alone...

 

VTR1000F lower fork sliders install right on your shiny new chrome tubes with custom cartridge internals. 

 

Good luck with your project.

[Worfje]

I am very happy with your suggestions / additions, so no need to 'leave me alone'. A next person who reads it can probably fully benefit.

[Captain 80s]

1 minute ago, Worfje said:

I am very happy with your suggestions / additions, so no need to 'leave me alone'. A next person who reads it can probably fully benefit.

 

Cool dude.  I'll still leave you alone.  You know where I stand and I have not explored these components as far as mix-n-match to accomplish what you are after.

 

Sincerely, good luck!

 

-Mike

[DrErgal]

As a mechanical design engineer I must only applaud to your effort and ability.
But I also must agree with Cap: a VTR upgrade (even the fork lowers only) would be a much better, leaner and more efficient job.
And last but not least, it would allow you to throw those crap calipers in the bin and install a couple of much worthy 4-pistons VTR calipers.

Tidy, LEAN, and efficient.
And (I think) as costly as your modification, or pretty close.
I just did, and I paid less than 200€ in total

[/

If you'd prefer to install your de-linking brace, well, it will be a great piece of engineering as well; there's no doubt about it  🤙

[Ughandi]

3 hours ago, DrErgal said:

But I also must agree with Cap: a VTR upgrade (even the fork lowers only) would be a much better, leaner and more efficient job.
And last but not least, it would allow you to throw those crap calipers in the bin and install a couple of much worthy 4-pistons VTR calipers.

I have had my bits for the VTR upgrade laying around for a while now. Only just received ownership of a steering-head lift to make it happen.This is an excellent testimonial of the upgrade & reinvigorates my decision.

Did you change springs, valves or any bits inside the forks (or just raw-dogged the OEM fork internals)?

...to the end of me wondering if Jamie Daughtry is privy on this swap, and if I should have any concerns before the swap on gutting the internals for some premium bits

----
(Apologize for any thread hijacking this causes)

[Mohawk]

That's a lot of work when just replacing the SMC actuator with a bolt & washer achieves the same. 
 

One of my old threads shows how & how to drill the bracket to reduce weight. 

[Terry]

You can pretty much mix and match all sorts of Showa fork parts, and I have done so between the VFR (5th and 6th), VTR and CBR600F4, depending on your desired outcome. They all use the same diameter cartridge and shaft so the pistons and shims can be reused or replaced as needed. The VTR and VFR share some pretty similar shim stacks (possibly identical, I don't quite recall)  and the same pistons, so aside from the adjustable rebound needle you aren't getting any real benefit. Unless you are a flyweight Japanese test rider, the springs can definitely be improved and I have used 0.9 or 0.95kg/mm with good results. Personally if you are down this rabbit hole I would replace the springs and add Gold Valves (or equivalent) at the very least in the compression position.

 

Personally I think the CBR954/SP2 callipers are much better than VTR for brake feel and power. My VTR had brakes that were a bit feeble then too grabby, and I think Honda could have done a better job matching the bore dimensions of master and calliper. 

[mello dude]

Posted this before, but for grins... left side with SP2 Caliper and VTR lower tube....

[JZH]

Well, if he's going to sell the brackets, there's probably a (small) market for a simple(r) bolt-on solution.

 

In addition to the SP2 calipers, there are 3-4 visually similar versions of those calipers available with different piston sizes.  929, 954, etc.  I used to have some black ones from an early CBR600RR on my RC36 (or were they from an F4i?)  Matched with the correct master cylinder, they are all more than adequate.  (I also had VTR1000F calipers on my first VTR1000F fork conversion, and they worked well--just not as well as the newer design.)

 

Ciao,

 

JZH

[VFR750F3]

I was warping rotors because I was doing track days and the 3rd piston was hanging up causing a lot of chatter.  Whatever I did I could not solve the problem.  For street use they probably will be fine,  Honda developed the linked system for a reason.  I watch You tube video explaining why you should use like 5% of the rear brake to get the bike to squat in order to get the most grip out of the rear tire. ie MotoGP rear squat device.  If Honda only made them into  6 piston calipers that mounted them axially and with no sliding pins they would be awesome.  How many of us over the years have had caliper pins seize up on cars.  It just a poor design. Nevertheless, I have Nissin 4 piston calipers on my 1986 VFR750F, 05 RC51 and my 02 VFR800.  Never had a issue and went back to using only Honda pads.  All other pads I tried were very abrasive. I do like my Brembo on my RRR they are not as grabby.  We come from different walks of life to share our loss of money from experience and to save a few people from agony on their journey.

[Worfje]

Still waiting on a 'flawless' milled piece, but I got a picture of the first attempt (it had some milling imperfections which they themselves did not find acceptable):

 

 

 

In the meantime, I fully serviced all clutch hydraulic parts and installed the first new Hel line in the proces.

 

I also anticipated that the hard brake line, which runs between the two front forks could need a different length (yes, I have trust issues).

After taking of 4 mm of the length, it was a perfect fit. 

The brake line tube nuts were reused and made a copy from CuNiFe tubing with an ATE tool.

 

 

I adjusted a CBR600F 1999 master cylinder to fit the VFR. The mounting point needed to be drilled, the threaded push rod needed to be shortened and I moved the connection from original to this one:

 

 

[ggathagan]

I would definitely consider the VTR lower swap, but I suspect that you have enough time/money invested in your approach that you want to see it to the end.

 

[Worfje]

Yeah, it is well under way and financed. Let's see what it brings.

 

 

Regarding the CBR600 F4 rear brake master: I copied the use from others that delinked.

Normally the original (close to) 17 mm bore pushes 2 rear and two front brake pistons (+ some loss due to all the length of brake line needed for that?).

 

I drilled the rear brake caliper, so all three pistons will move.

Switching to the CBR600 F4 should reduce the bore to 14 mm, which should circumvent a hard / oversensitive rear brake experience. 

[Terry]

1 hour ago, Gaz66 said:

WoW!!!.

You really need to read up on hydraulic braking systems, especially linked & more to the point delinking a linked system, you clearly aint got a scooby doo.

Filling a master cyl with epoxy?

What ever you do bro, don't ever offer to help anyone service their bike if you consider using epoxy a wise move.

It would be like handing a chimp a hammer in a glass factory.

As for drilling front calipers, front  master cyl isn't capable of running 6 pistons, it's only designed to run 4 pistons, drilling em, you'd have massive lever travel & little to no front brake effort.

 

Linked braking systems need to be either left well alone & serviced as stated in shop manual.

or

Swap out fork lowers & calipers for known parts that work.

 

Jeez !!! Epoxy FFS...OMG...Fakulaka.

 

Well that was more of a dick response than I was expecting. Maybe you could try reading a post and considering its merits before turning into a social media flame warrior.

 

I was referring to the SMC and preventing it from moving so the calliper stays where it ought to. Any means of locking the SMC will do, and using a cured epoxy to fill in the void will do quite nicely as all it is doing is replacing the fluid that normally sits in there. I was not suggesting that the epoxy would also be in the brake lines. I'm not sure that I understand what your rational objection to that is, but I try and stay open minded to the views of others so let us know.

 

As for your comment about the master cylinder ratio when drilling using all 6 pistons up front, maybe you missed the comment "and use a larger bore front MC to match".

 

I've actually done a delink on my previous 5th gen, the "proper way" by replacing the fork lowers with VTR parts, CBR600F4 callipers, CBR600RR master, cbr600F4 rear master and joined hoses at the rear master, and I have worked through the maths of master to slave hydraulic ratios by spreadsheet to ensure I understood what I was doing. 

[Worfje]

I appreciate your input Terry and your reminder on the front MC bore that needs to be enlarged. I will arrange that. Some nice info here.

 

As stated: the VTR option is proven and in general should be the cheaper option in parts.

The custom bracket set me back around 390 euro... this might be lowered if I had taken the time / patience to get more quotes.

Actually, I was already happy that a company would take on my single piece work. 

 

Regarding the front master cylinder bore:

VFR800FI 1998/2001 is roughly 12.7 mm diameter

CBR400F4 1999/2000 is roughly 14 mm diameter

or go for a Nissin radial? It is nice to know the bore, but in the end it is the needed handle travel, resulting displaced volume and the (added) piston volume.  

 

[Terry]

If you needed it, the masters for the VTR1000SP2, CBR954 and CBR600RR are all 17.46mm diameter. And the VFR800 6th gen also uses the 14mm master.

 

The stock area ratio (slave pistons/master piston) for the 5G front (master to 4 piston) is 16.0, if you connect all 6 pistons that rises to 19.1. A 14mm master brings it back to 18.2 and a 17.46mm master makes it 11.7.

 

A higher ratio value gives more leverage over the pistons and makes them grabbier, or a lower ratio makes for a more wooden feel to the brake but less grabby. Based on these numbers a 14mm master is probably the best compromise to drive all 6 front pistons. For reference the 6th gen VFR front drives 5 pistons (just the left middle is from the rear brake).

 

 

[Captain 80s]

5 hours ago, Terry said:

If you needed it, the masters for the VTR1000SP2, CBR954 and CBR600RR are all 17.46mm diameter. And the VFR800 6th gen also uses the 14mm master.

 

The stock area ratio (slave pistons/master piston) for the 5G front (master to 4 piston) is 16.0, if you connect all 6 pistons that rises to 19.1. A 14mm master brings it back to 18.2 and a 17.46mm master makes it 11.7.

 

A higher ratio value gives more leverage over the pistons and makes them grabbier, or a lower ratio makes for a more wooden feel to the brake but less grabby. Based on these numbers a 14mm master is probably the best compromise to drive all 6 front pistons. For reference the 6th gen VFR front drives 5 pistons (just the left middle is from the rear brake).

 

9 hours ago, Gaz66 said:

WoW!!!.  Physics!!  OMG...Fakulaka!

[DrErgal]

On 2/12/2025 at 7:16 PM, Ughandi said:

Did you change springs, valves or any bits inside the forks (or just raw-dogged the OEM fork internals)?

Internal OEM equipment, just renewed (new oil, bushings and seals)
As you can figure out, the behavior is slightly the same of the stock fork. The only improvement comes from the rebound adjustment and (obviously) the fact it can hold solid calipers 👍