[Alan S]

If ABS is involved, DOT 4.
All else gets DOT 5.

Sent from my SM-G965U using Tapatalk

 

[kdkerr2]

Gregg55_99 asked: "Since this thread was brought back from the dead, a question. What master cylinder is used for this dual disk conversion?" Always use the Harley 11/16" master cylinders found on late model H-D Baggers [Road Kings, Electra Glides, etc.]. However Harley did make a 3/4" master cylinder and Brembo's got out a radial RCS19 radial style master cylinder with a 1" handlebar clamp for Harleys. Handlebar Master Cylinder 3/4 Bore Black fits Harley-Davidson | eBay
Brembo RCS19 GP Radial BRAKE w/ FOLDING LEVER for 1" bars (HD/V-Twin) (FREE EXPRESS SHIPPING ) 110.A897.10 (hardracing.com) The 11/16" master cylinder has a .687" bore diameter. The H-D 3/4" master cylinder is .750". The Brembo RCS19 has a 19 mm bore dia. or about .748". All thing being equal the bigger the bore the more fluid the piston can push resulting in more stopping power. These Brembo RCS19's are sold as replacement units for crotch rockets are are supposed to be the last word in motorcycle stopping power!

 

[kdkerr2]

Since this post was about H-D brake upgrades.I decided to post my custom front end I built for my '05 Dyna. It's got 08+ Dyna 49 mm forks with midglide triple trees, a Sportster XR1200 wheel, dual Tokico 6 pot 'Busa calipers and dual 320 mm Brake Tech rotors. I'm running a Road King 11/16" master cylinder. I'm running DOT5 in the brake system after thoroughly flushing out the calipers and installing new seals and pads. Unfortunately last June I ran into Bambi's sister on the road home and my front end was trashed! I'm going to rebuild with all the same components and probably upgrade to the Brembo RCS19 master cylinder.

 

[Greg55_99]

Just to clear up some of my confusion.

Was the 11/16" master cylinder ever used with the dual disks for the early FXR's? (mine is an 87).

It appears the 3/4" WAS available for the early Harley's. Is this the master cylinder to use when upgrading to dual Brembo's?

When using either of these, is DOT5 required in a NON ABS configuration?

Sorry if I repeat myself, just trying to get this clear. I have a set of dual Brembo's already but I currently have a single disk master cylinder on my FXR. I just want to make sure I get the correct parts to upgrade.

Greg

 

[Joe Shovel FXR]

I have to disagree with @kdkerr2 about piston size. A smaller MC piston will give you greater line pressure and more stopping power. Larger MC piston will give a wooden feel to the lever, with no modulation. Think of it this way, the force your hand puts on the lever is the same both ways, but the smaller piston will have less square inches, so there are more pounds per square inch than with a larger piston. I'd go with the stock Harley 11/16" setup.

 

[hillcat]

Sorry if I repeat myself, just trying to get this clear. I have a set of dual Brembo's already but I currently have a single disk master cylinder on my FXR. I just want to make sure I get the correct parts to upgrade.

Greg

If you are running stock switches/housing it's best to run the H-D 11/16" so it fits up and the brake switch works.
Check Ronnie's parts numbers for compatibility.

 

[kdkerr2]

Gregg55_99 asked: "
"Was the 11/16" master cylinder ever used with the dual disks for the early FXR's? (mine is an 87).
It appears the 3/4" WAS available for the early Harley's. Is this the master cylinder to use when upgrading to dual Brembo's?
When using either of these, is DOT5 required in a NON ABS configuration?"
I can't give a correct answer because I don't know. I assume that several of the FXR [like the Low Rider Sport] which ran dual disks used the 11/16" master cylinder. The 3/4" master cylinder posted in my Ebay add was an older model of master cylinder and there's some fitment problem with modern switch boxes [as Hillcat commented on]. Harley switched to DOT4 brake fluid a few years back when they realized that DOT5 was incompatible with antilock brake systems. On all your old brake systems [before the ABS] continue to use the DOT5. It's much easier on paint jobs! I'm running DOT5 in my upgraded custom brake setups and I'm aware of the compatibility problems of the DOT5 in my Tokico calipers. No problems with them so far but I can't recommend them to anyone else. If you are by chance upgrading to an antilock brake system make sure all the DOT5 fluid is thoroughly flushed out of your upper brake components. The two DOT fluids do not mix well!

 

[Turboprop]

My red/white FXR has Brembo RCS master cylinders for the front brakes and clutch. They work very well with most four pot calipers found on sport bikes.

As for the remark about them not having a brake light switch, wrong. These MCs have a pressure switch that can easily be integrated into any oem or custom wiring harness.

This is my FXR with Brembo RCS master cylinders on the RB Racing website.

Scroll down.
RB Racing website with Turboprops FXR.

 

[kdkerr2]

Excellent! You are correct. I wasn't aware until recently that the Brembo RCS master cylinders came with an on board brake lite switch. So hooking up a hydraulic pressure switch for the front brake is unnecessary.

 

[Turboprop]

Excellent! You are correct. I wasn't aware until recently that the Brembo RCS master cylinders came with an on board brake lite switch. So hooking up a hydraulic pressure switch for the front brake is unnecessary.

They also have the ability to mount the same switch on the clutch MC. Typically used for racing applications to trigger another event.

 

[hillcat]

As for the remark about them not having a brake light switch, wrong.

Who said that?

 

[Doward]

I'm running dual disks + '13+ touring brembos on my FXR - 11/16" MC here!

 

[kdkerr2]

Doward posted: "I'm running dual disks + '13+ touring brembos on my FXR - 11/16" MC here!"
Excellent! The 4 pot Brembos actually had slightly smaller diameter pistons than the earlier H-D 4 pot pistons. However the Brembos develop more stopping power because they ran a 300 mm dia. rotor vs. the earlier 292 mm dia. rotor stock on all the FXR's. I suspect the top of the line gear would be to run the 320 mm Brake Tech rotors along with the Brembo RCS19 master cylinder like Turboprop did on his FXR. Running them with either the H-D '00 4 pot calipers or the H-D Brembo 4 pot calipers should be sufficient! I was told the newer 4 pot radial calipers don't actually give the rider more stopping power. What they do is give the rider better feedback so he [or she] can use their front brakes more efficiently without doing a stoppy.

 

[kdkerr2]

Turboprop, are you running Dot 5 or Dot 4 brake fluid in your FXR's front brake system?

 

[Turboprop]

Dot 4.

 

[Greg55_99]

OK, I'm back for MORE clarification because, as usual, I get confused. So...

I have a set of the 2000+ black Nissen (I think) four pot touring calipers. I have a set of fork adapters. I have a set of 1988 39mm forks. I have an 11/16" master cylinder. Can I re-use my 35mm front axle and wheel AND 11.5" rotors.

Greg

 

[kdkerr2]

Gregg55_99 posted: "I have a set of the 2000+ black Nissen (I think) four pot touring calipers. I have a set of fork adapters. I have a set of 1988 39mm forks. I have an 11/16" master cylinder. Can I re-use my 35mm front axle and wheel AND 11.5" rotors." According to all you have written you should be good to go with your caliper adapters. In 2000 when H-D switched to the new four pot Nissan calipers they changed the bolt hole pattern on the sliders of Sporties, Dynas and FXR's so the new calipers don't mount up on the old fork sliders. I'm pretty sure H-D used the same sized 3/4" front axle on both Sporties, FXR's and Dynas on both 35 mm forks and 39 mm forks. So, your engineering change should be a simple bolt together op! And all the front four pot calipers were interchangeable on the all the Sporties, Dynas, Softtails and baggers. Call me at 270-234-6211 or email me at kdkerr2@msn.com if you have any problems. Please post a pic of your bike when you get your changeover completed.

 

[kdkerr2]

Summary:
In summary for this thread, to run the Brembo 4 pot calipers on an FXR [this also goes for Sportster and Dynas up to 05] you need to be running the 2000 and up 39 mm fork sliders with the 300 mm diameter rotors [08 and up]. You can run the earlier [pre 2000] sliders with the 2000 Nissan 4 pot caliper if you have adapter brackets with the 292 mm diameter rotors. Also a late model H-D Sportster wheel is in order for the 300 mm rotors because the rotor center hole was enlarged. The 300 mm [11.8"] rotors [08 and up] can only be run with the Brembo 4 pot calipers. The 292 mm rotors [11.5"] have to be run with the 4 pot Nissan calipers. When upgrading from a single caliper to dual calipers everyone agrees it's best to upgrade to the H-D 11/16" master cylinder used on H-D baggers like the Road King and Electra Glide. You can run the Brembo RCS19 radial master cylinder with the dual disk system but it's recommended that you switch over to DOT4 brake fluid in your brake system. You can upgrade to the Brake Tech 320 mm rotors but adapter brackets are needed to bolt up your Brembo calipers. They're available from Brake Tech.

 

[kdkerr2]

Note on post #23. Don't try this unless you're a machinist or you have a machinist who can do this work. I used an H-D XR1200 front wheel because it's supposed to have better handling and braking then the stock 19" Dyna wheel. Also the Tokico Hayabusa 6 pot calipers were designed to use DOT 4 brake fluid. I've been running DOT 5 in them. So far there's been no problems or on my 06 Sportster which had the changeover several years ago. But this might not be a good idea. Harley switched over to DOT 4 a few years back when they finally brought out their antilock brake systems.

 

[olmatey]

Summary:
In summary for this thread, to run the Brembo 4 pot calipers on an FXR [this also goes for Sportster and Dynas up to 05] you need to be running the 2000 and up 39 mm fork sliders with the 300 mm diameter rotors [08 and up]. You can run the earlier [pre 2000] sliders with the 2000 Nissan 4 pot caliper if you have adapter brackets with the 292 mm diameter rotors. Also a late model H-D Sportster wheel is in order for the 300 mm rotors because the rotor center hole was enlarged. The 300 mm [11.8"] rotors [08 and up] can only be run with the Brembo 4 pot calipers. The 292 mm rotors [11.5"] have to be run with the 4 pot Nissan calipers. When upgrading from a single caliper to dual calipers everyone agrees it's best to upgrade to the H-D 11/16" master cylinder used on H-D baggers like the Road King and Electra Glide. You can run the Brembo RCS19 radial master cylinder with the dual disk system but it's recommended that you switch over to DOT4 brake fluid in your brake system. You can upgrade to the Brake Tech 320 mm rotors but adapter brackets are needed to bolt up your Brembo calipers. They're available from Brake Tech.

I have a 2000+ front end and 2 brake calipers to put on my 85 fxr, i just need to buy a right side fork lower. Will 11.5" rotors work with my calipers?