Rear brake options for RC24/26 wheel swaps

Discussion in '1st & 2nd Generation 1983-1989' started by Captain 80s, Oct 21, 2021.

  1. Captain 80s

    Captain 80s Member

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    Been wanting to put this together for a while. It really is the most difficult part of updating these bikes to wheels like the F2/F3 rear wheel. And it's really not that hard, but there is no bolt on scenario that doesn't involve some custom or modified parts. I will be concentrating on using existing parts that are modified to use for this application (as I like to do), with some spacers that need to be machined.

    You can always have a custom caliper brackets machined, and that would be very cool. For someone like me that is modifying multiple bikes on a budget, it's not really a viable option. And when done right with existing parts, it can look like very "stock" like it came that way. Plus it's enjoyable. Crack a beer, put on some music and figure some shit out.

    Most of these options are going to assume you're using the CBRF2/3 sprocket carrier with the wheel. F2 (4.5") or F3 (5.0") mount exactly the same. The key ingredient to start with is a 14mm left spacer. This puts the studs pretty close to the swingarm, but there are no issues. The wheel is exactly factory center.

    20191008_182532.jpg

    Chain center is VERY close to factory. Every bike is slightly different and I've had a couple end up with the chain running perfectly, no changes. You can also flip a factory style sprocket around and the slight dished side that is normally outward, will effectively move the sprocket in a couple mm. That's what I did on the "RC26" and it was perfect. I plan on machining a couple hubs down on the lathe for a worry free install regardless of sprocket type. I suggest mocking up your bike before making any permanent changes and see where it sits. A stock F3/VTR1000F left spacer is 14mm and works perfectly to get started.

    I guess I should mention the OG method was to have the stock caliper bracket sectioned and re-welded to match the smaller disk. Go down that path if you like at your own risk. It has been done successfully, but it's not for me.

    It will be updating this on the fly as I collect the pictures, parts and info to post. I realize that there isn't a HUGE demand for this info, but it will also help me get it all in one place, with comments and ideas from the community.

    Cheers,
    -Mike
     
    Last edited: Oct 21, 2021
  2. Captain 80s

    Captain 80s Member

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    Part I:

    Using the F2/3 rear caliper bracket. Some options:

    Quick and dirty. This is not one of mine, but should be mentioned as it is simple. Drill and tap the bracket and use a spacer to mount the torque arm.

    P9010196.jpg

    Not really for me, but I can see removing a bunch of the forward part of the bracket where it normally engages a slot and shaping and blending what remains for a pretty decent look. You may have to grind / blend some of the torque arm where its passes by the tire for clearance. Pretty simple option.

    Decided to do a play on it for the RC26.

    IMAG0955.jpg

    I machined down the lug to flush and drilled and tapped it for the shouldered stock bolt. Thought it looked more like an original attachment point. Modified a VF750F torque arm so it sat outboard and wouldn't interfere with the tire. You can see that this rotated the caliper back but it didn't interfere with anything. Plus it gave the arm a nice angle near the top of the "arc", directing the force in the correct direction. The original torque arm is too long for this application. The sweet spot for spacers on the right side of the wheel are 14mm between wheel and caliper bracket and 19mm between caliper bracket and swingarm. Clearances on the caliper bracket and disk will allow the use of 15 - 18 (Pictured - 18 being the original sprocket side VFR spacer). You're having a custom spacer made either way, so I would hit the sweet spot.

    IMAG0956.jpg
    IMAG0958.jpg
    IMAG0961.jpg

    Both bolts are still shouldered and bottom out for correct torque setting. I decided to keep going on this route and come up with something different later. Well I did (the point of this thread), but this setup is still on the bike and has worked perfectly. I'm keeping it at this point just because it was my first solution and still looks good to me.

    RC26_2.jpg
    20201015_172919.jpg
     
    Last edited: Nov 2, 2021
  3. Captain 80s

    Captain 80s Member

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    Part II:

    Retaining the original caliper and bracket.

    This one is pretty cool. There is a Triumph rear disk application that has the bolt pattern of the F2/3 wheel and the outer diameter of the VFR disk.

    20191008_182724.jpg

    I scored this EBC disk on a listing that I don't think they knew what they were selling. I should have bought them all. Got it for like $33. I will update later with the part # to help with cross-referencing. I used to have the list of applicable models, but I couldn't find it. This EBC part # will take care of that. A stock one looks like this and actually looks very Honda-like. This is off a Bonneville.

    disk.jpg

    You will have to clearance the brake torque arm for the tire. I also swapped the side the washers go on the shouldered bolts to give the arm a straighter run, but it's absolutely needed. Your right side spacers will be 16mm between the wheel and the bracket, and 8mm between the bracket and the swingarm. Here's a full set I had made at my last job.

    20191008_181124.jpg
    20210214_150539.jpg

    The only down side of this route is that these disks (including the factory Triumph) are thick at 6mm. It doesn't cause any fitment issues, it's just thicker than it needs to be and weighs more. I am going to send this disk to TrueDisk and have it brought down to 3.5 or 4. For a set of spacers, the conversion can look very stock, perform great and help keep costs down depending on the price of the disk.

    After looking at the pic of the stock Triumph rotor, I bought a used EBC version so I could see it mocked up.

    20211103_172358.jpg

    I really like it. Looks very stock Honda with the original bracket and caliper.
     
    Last edited: Nov 3, 2021
  4. Captain 80s

    Captain 80s Member

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    Part III:

    CBR929RR rear carrier and caliper.

    This is probably the best looking option if you want the smaller single piston caliper. Source a 929 rear bracket.

    20211102_173844.jpg

    Machine down the lug where it normally engages the 929 swingarm to nearly flush and drill and tap a hole for the VFR torque arm bolt.

    20211102_173904.jpg

    There's plenty of material for full nice full threads.

    20211102_174002.jpg
    You will need to have a press fit spacer made to reduce the axle hole down to 20mm for the VFR axle.

    20211102_174015.jpg
    20211102_174026.jpg

    The good news this can be the only custom spacer if you want. The other two for the right side are a 14mm (F3/VTR1000F sprocket side) and the original far left VFR spacer from the sprocket hub (18mm).

    20211102_174329.jpg

    This perfectly centers the F2/3 disk and the torgue arm has a straight shot to the front swingarm mount. Nice.

    20211102_175332.jpg

    2 things. The torque arm bolt above (that has doubled up washers just for this pic) needs to be shortened so the shouldered bolt with the original metal and rubber washers will bottom out against the caliper bracket and can be properly tightened, but doesn't contact the disk thru the back. And the arm will likely need to be clearanced in the right area for the tire.

    Sweet.

    20211102_175437.jpg
     
    Last edited: Nov 4, 2021
  5. Captain 80s

    Captain 80s Member

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    Part IV:

    Using a Hurricane 600 (87 - 90) caliper bracket. Allows the use of the F2/3 disk and stock rear caliper.

    Source a 87 - 90 CBR600F rear caliper bracket.

    20211103_165919.jpg

    The right one stock at 17mm. The left one has been drilled out to 20mm for the VFR axle. A step drill bit in a press can handle this job. You're spacers will be 10mm between the wheel and bracket (close, but fits no problem), and 20mm between the bracket and swingarm. Puts the disk right down the middle.

    20211103_165600.jpg

    You can machine off a few mm from the bracket to give the arm a straighter run, but it's not absolutely needed. There's plenty of play to still tighten the shouldered bolts properly, and the arm doesn't looks askew.

    20211103_165800.jpg

    You might have to relieve the arm a bit for the tire. Caliper sits on there nice, as the inside pad wears, the caliper will slide to the outside. This was a pretty thick Ferodo pad for a good example. A Hurricane 600 caliper might sit slightly better initially with new thick pads, but I actually think they are the same caliper.

    20211103_165519.jpg

    Looking pretty damn good.

    20211103_165510.jpg
     
    Last edited: Nov 4, 2021
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  6. sixdog

    sixdog New Member

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    Map
    I bought some extra microwave popcorn Mike …


    Sent from my iPhone using Tapatalk
     
  7. Captain 80s

    Captain 80s Member

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    Bump. Intro and Part I updated.
     
  8. RogueRC24

    RogueRC24 New Member

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    Don't deny it, you knew I was going to ask you questions about this and you wanted to have it all in the clear so I wouldn't bother you. lol Just got little red insured so I am clear to ride, but I already want to mod. Popcorn indeed. Good show Capt.
     
  9. Captain 80s

    Captain 80s Member

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    Haha! I was surprised you hadn't asked already! I have been wanting to do this for a while, but your registering success and known desire to mod nudged me a bit. Might as well get this shit down.
     
  10. Captain 80s

    Captain 80s Member

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    Bump. Part II updated.
     
  11. Captain 80s

    Captain 80s Member

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    Bump. Part III updated.
     
  12. RogueRC24

    RogueRC24 New Member

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    ^^^^ Excellent info. Not sure which to go with. Already have the f2 rotor so maybe the 929 version. hhmmmmm decisions. :thumbs:


    You can stop anytime now...lol sooo many options. Excellent photos.
     
    Last edited: Nov 3, 2021
  13. Captain 80s

    Captain 80s Member

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    Bump. Part IV updated.
     
  14. Captain 80s

    Captain 80s Member

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    Sticky !
     
  15. RogueRC24

    RogueRC24 New Member

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    OO ooooo . I am going with the 929 version. I like the single-piston look and I already have the F2 disk and I found the 929 caliper, bracket, and ss brake line shipped for $26. Just need the sprocket hub/cushions, each of the wheels spacers, and the axle reducer spacer. Your sticky is invaluable! Getting excited again especially since this might be first and only real mod.
    Thank Capt. There will be more questions I am sure. lol
     
  16. Captain 80s

    Captain 80s Member

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    I almost bought that caliper and bracket! Good deal.
     
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