Bonneville T-120 Brake Upgrade

Discussion in 'Technical & Motorcycle Services' started by Hoghead, Aug 7, 2020.

  1. Hoghead

    Hoghead Ol'Timer

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    Given that it seems impossible to post pics from my conputer, see this tech note I posted on the Triumph Rat site:

    front calliper upgrade T120
     
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  2. Ian Bungy

    Ian Bungy Ol'Timer

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    Here We go just for You Robert!
    And what an Impressive and Detailed report I might say! Wow! I would of never guessed You are an Engineer ! Ha Ha!

    WATERCOOLED TRIUMPH T-120 BONNEVILLE FRONT BRAKE UPGRADE

    The Nissin 3 piston calliper upgrade is a known mod for the new gen Triumph airhead models, but I could find no definitive information on using these callipers on the water cooled T-120. PN for the fork legs are different between air and water cooled models so no inference could be made.

    While not a simple bolt on, the mod is a cost effective method to improve the 2016+ Triumph T-120 Bonneville brakes, by using Nissin 3 piston callipers from a Honda CB1000R/RA, resulting in a 29.39% increase in calliper piston area. The modification consists of new callipers with appropriate brackets, calliper machine work, hydraulic plug, and a radial master cylinder on a bespoke mount. Floating brake rotors are optional, and not required for the mod.

    Two alternative Nissin 3 piston calliper upgrade methods are described, using modified Honda CB500/600 callipers for a 14.1% increase in piston area, or a simple bolt on using Honda CB1000 callipers with 12.24% increase in piston area. While not offering the same increase in clamping force, these alternatives are significantly cheaper as a new master cylinder, and little or no machine work is required.

    dsc_6665_resize-.

    3 piston Nissin callipers with Triumph Street Triple 765RS floating rotors

    PARTS LIST

    Callipers:


    1 Pair Nissin 3 piston callipers and brackets from a 2008-16 Honda CB1000R/RA - Honda 45200-MFN-D00 and 45100-MFN-D00 (black) . The CB1000R/RA piston sizes are asymmetrical at (2 x 27mm) + (1 x 22.5mm) for one side and the other at (2 x 25.5mm) + (1 x 22.5mm). When machined to defeat the Honda linked brake system, yields a 29.39% increase in piston area over stock. These came in ABS and non-ABS versions, and if ABS, the sensor appendage needs removal.

    Cross referencing the bracket PN will give you a list of bikes with these callipers and brackets. Other late 2000’s Honda models also used 3 piston callipers, but may not have compatible brackets.

    1 ea. M10 x 1.25 x 15mm stainless bolt with copper sealing washers to plug the now unused centre linked piston hydraulic input.

    The stock brake lines fit. You will need new 10mm copper or aluminium banjo sealing washers. Do not re-use the old washers.

    dsc_6607_resize-.


    Nissin 3 pot calliper before machine work. The centre piston bore needs to be increased to that of the other pistons, in order to intersect the hydraulic connection between the outside bores.



    Calliper brackets:

    If you are not lucky enough to find callipers with the correct brackets you will need:

    1 ea. R bracket #45290-MER-R81. Here in Thailand this is off a locally manufactured, 2011-13 Honda CBR250, and cheap as chips. The ABS sensor appendage will need removal.

    1 ea L bracket #45190-MFA-D11. Seems unique to the 2009 Honda DN-01 / NSA700A, and several EU/UK/Aust Honda models.

    dsc_6610_resize-.


    45290-MER-R81 (top) and 45190-MFA-D11 (bottom) calliper brackets.

    Pads:
    2 ea. Pad sets.
    I like EBC-HH pads, so # FA388HH for street use.
    dsc_6624_resize-.


    dsc_6628_resize-.

    Bottom is EBC-HH stock size pad, centre is stock Honda 3 pot pad, top is EBC FA388HH



    Rotors:


    Not necessary for the mod, and stock rotors will work.

    Several Triumph models including the water cooled Thruxton, and the Street Triple 765RS use significantly lighter, floating rotors, that are a direct bolt on fitment. While this does not increase the clamping force, it is recommended for better braking and handling. See EBC – MD883X (with an even lighter aluminium carrier), for a cross reference list



    Master cylinder:


    With an almost 29.39% increase in piston area with the machined CB1000R/RA callipers, the stock 14mm master cylinder will be too small. I did not consider a larger bore axial MC, as I wanted the radial MC advantage of a slightly higher ratio for less effort at the lever, and more importantly, a wider engagement band. This will allow finite modulation of the brake at locking point, before the ABS Nanny starts interfering.

    MC bore, internal ratio, and distance from rider finger to MC internal fulcrum (inter-axis ratio) is critical. A Brembo RCS19 x 18 internal ratio MC, with the inter-axis ratio at 90mm, will be ideal for most riders. Changing pad CF and varying the inter-axis ratio, will allow fine tuning.



    MACHINE WORK

    Changing the brake master cylinder is a significant portion of the project cost, as the T-120 uses a switchgear/ RBW throttle clamp which is integral with master cylinder. This precludes the use of a stand-alone Brembo style radial MC. I was unable to find suitable modular switches, so had to make my own switchgear and RBW throttle clamp, in order to change the MC.

    The L calliper uses the Honda linked brake system, connecting the centre piston to the rear brake pedal. Defeat this system by interconnecting the pistons by counter boring the centre bore to the same depth as the outboard pistons. The separate hydraulic input for the L calliper centre piston is then plugged.

    dsc_6613_resize-.


    12mm counterbore in the centre piston bore.


    dsc_6664_resize-.

    Plug in the now unused centre hydraulic input. One can only wonder why the input and bleed are not at opposite ends?



    If ABS calipers are used, the R calliper bracket has an appendage for the ABS sensor, and best removed for a clean look.

    dsc_6611_resize-.


    R bracket showing where the ABS sensor appendage was removed

    dsc_6622_resize-.


    Note that 45290-MER-R81 has been machined to remove the ABS sensor bracket




    ALTERNATIVE METHODS


    Using the stock 14mm master cylinder significantly lowers the project cost. Smaller displacement Hondas, use smaller bore 3 piston Nissin callipers, which allows the use of the stock master cylinder. A simpler and cheaper mod is to use Honda CB500/600 Nissin 3 piston callipers with 3 x 22.5mm pistons in one side and the other at (2 x 25.5mm) + (1 x 22mm). When machined to defeat the Honda linked braking system, this yields a 14.1% increase in piston area. While not an optimal ratio, this mod could use the stock master cylinder.

    Simplest of all, and with a better master cylinder ratio, is the 12.24% increase in piston area using the same CB1000R/RA callipers with stock master cylinder, but not doing any L calliper machine work to defeat the Honda linked braking system. A bespoke plug is not required for the unused centre piston.

    The same calliper bracket requirements and modifications apply in both alternative methods, if you cannot find a bike with compatible, non-ABS brackets



    Hoghead;
     
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  3. Hoghead

    Hoghead Ol'Timer

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    Thanks Ian, so will have to show me how you did that
     
  4. Hoghead

    Hoghead Ol'Timer

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    BTW, I have a machined pair of the smaller bore CB500/600 callipers for sale that I did before deciding to change to the bigger CB1000 ones. Note that the bigger callipers requires a new MC and significantly increases the project cost
    Silver as shown in my pics, and ready to bolt on and go
    NOS Honda, (not rebuilt), with new Honda pads
     
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  5. DavidFL

    DavidFL Administrator
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    Damn impressive there Hoghead.
    Well done.
    Well done Bungy for helping out with the pics too.
    TQ both of you.
     
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