Marc Rittner (Part 3) - Icing On The Cake


Marc continues with his excellent write up with an R1 rear caliper swap for the Thunderace conversion.


It is a relatively simple matter to swap out the stock Ace rear brake caliper assembly for an early model R1 brake caliper assembly.  I will be the first to state that there is absolutely nothing wrong with using an Ace rear brake.  It has superb feel, and uses the same master cylinder as the stock FJ rear brake. 


However, I could not pass up the opportunity to add a more finished look to my bike by adding a R1 rear caliper that matched the R1 front calipers.  The end result is a rear brake caliper assembly that not only looks great, but works every bit as good as the stock Ace setup.  Note that the R1 rear caliper pads are smaller than the Ace pads, but are of a sintered bronze material.  This is the same materials as used on the R1 front pads, which have a reputation for great feel and long life, without tearing up your rotors.


The following is a basic task list of what I did to fit the R1 rear brake caliper assembly to the Thunderace Swingarm: 


  1. Parts list:
    1998-2001 R1 rear brake caliper, bracket, bolts, and master cylinder.
    (2) 10mm I.D. x 2mm thick aluminum washers
    (1) FZS1000 (FZ1) rear brake caliper bracket
    (1) Custom stainless steel braided brake hose.  30 long with 10mm banjo fittings.  One fitting is straight (at master cylinder), the other is 30 degree (at caliper)

  2. Modification to R1 rear brake caliper bracket 3 mods are required to use the R1 bracket:

    a)  Weld on a torque arm attachment tab.  This was very easy to do, although a bit wasteful.  I cut the torque arm attachment tab off of a perfectly good FZ1 rear brake caliper bracket.  It was desirable to do this as the tab had the correct OEM attachment configuration, was made of aluminum, was the correct thickness, and provided the correct offset for the rear brake torque arm.

    Preparation of the part to be welded was minimal.  Simply file or grind a flat spot on the lower right edge of the R1 bracket, and have a competent welder TIG weld it in place.


b)  Machine a relief in the backside of the bracket to clear the rotor bolts.  This was a simple lathe job, where 5/8 wide and 0.130 deep relief was made.  We got fancy and beveled the edges to match the rotor bolt heads.

Note:  I used the stock Ace rotor and bolts.  This relief cut may not be necessary if you change to a R1 rotor and bolts.  But hell, then there would be no modifying and what fun is that?  The R1 rotor has already been countersunk to provide this clearance, and uses a different, lower profile bolt.  It is also much thinner than the Ace rotor, so will not take as much heat with a big heavy bike. 

c)  Center the caliper on the rotor with a washer positioned between the caliper and bracket.  I had my machinist make up some custom aluminum washers that were 10mm I.D. x 0.750 O.D. x 2mm thick.


  1. Modification to the R1 rear master cylinder - the R1 rear brake caliper uses a differently bored rear master cylinder than the FJ (1/2 vs. 14mm).  It is necessary to use the R1 rear master cylinder to get proper brake feel and leverage.  There are 3 small changes you will need to make when mounting an R1 rear master cylinder on your FJ:

    a)  The R1 master cylinder body is not threaded for attachment bolts.  Easily solved by using longer bolts through the mounting tabs, backed by lock nuts

    b)  The R1 master cylinder reservoir and hose is different than the FJ.  Fortunately, the R1 and FJ master cylinder reservoir and hose attach to the master cylinder bodies in exactly the same manner.  (they are both Brembo master cylinders) Swap the FJ parts onto the R1 master cylinder.

    c)  The R1 master cylinder linkage is different than the FJ.  Remove the R1 rod, clevis, and nut, and swap for the FJ rod, clevis, and nut. 

  2. Assembly

    a)  Install the new R1 rear caliper bracket between wheel and right side of swingarm.  Bracket hangs below the swingarm, with torque arm tab toward the front of the bike.

    b)  Attach caliper to bracket using stock bolts.  Put the special 2mm spacers between bracket and caliper.

    c)  Attach rear brake torque arm to caliper bracket in standard fashion, using stock bolt, nut, and clip.  The front end of the rear brake torque arm is offset to the outside of the swingarm attachment point.  Use a longer bolt and nut.  Put washers or a spacer in the clevis end to keep it from collapsing when you tighten the bolt and nut.

    d)  Mount modified rear master cylinder.  Attach new brake hose using new copper crush washers.  Bleed brake system and GO!
    Congratulations on a job well done. 

Congratulations indeed. That's a beautiful looking bike Marc. Top job !

Marc's Ace Swingarm Installation

Marc's YZF750 Fork Installation