76 Bonnie front brake upgrade

[vintagemotorbikes]

First post here, so bear with me. I did some research first for threads- hopefully in depth enough so this isn't a repeat. If so then you can tear me a new one- just tell me where to find it.

I have a buddy who's asked me about working on his '76 Bonnie and wants to upgrade his current disk brake to something larger/modern-er. He's been looking into a kit from Brittain but is there anything else available closer by or more reasonable? Or maybe a jap upgrade that is an easy modification? .... something accessible of course

I like the stock disk, but I guess he's going to go fast or something

[Speedfiend]

On the disc Triumph front end, its not the rotor or caliper that needs improvement. Its the master cylinder. The original Lockheed masters have a figgin huge bore, like 14 mm or something. Replacing it with a more modern unit will drasticly improve braking. The Magura MX master cylinders work the trick. The Lockheed calipers are heavey, but work pretty OK (on the front)

But to your question, I don't know of any low-dough kits available. I would love to know if theres a common Japanese caliper or rotor that could be easily be modified to work. I

[Torch]

that was a good brake to begin with. it usually doesn't require any upgrades.

[vintagemotorbikes]

Yeah, i've tried convincing him to just leave it alone, but we'll see what happens. Just was wondering if there's already a common replacement/upgrade out there already.

Thanks guys for you help

[CRFyou]

Yeah, i've tried convincing him to just leave it alone, but we'll see what happens. Just was wondering if there's already a common replacement/upgrade out there already.

Thanks guys for you help

i used a master cylinder/lever combo from a newer yamaha dirt bike on my '73 t-140.

it did the job better than your buddy will need. since he'll have to upgrade the master cylinder anyway. tell him to start there and see if he still wants/needs more.

[vintagemotorbikes]

I agree that would be a good place to start- dirt bike masters/levers are nice and clean looking to boot

[Torch]

I agree with a M/C change there is nothing good looking about the Triumph set up. and a new master cylinder replacement is $200 just for the cylinder itself so a dirt bike setup is cheaper and better looking.

[Guest]

i.m running drilled disc, front/rear does pretty good,on a 1977, bonneville rest is stock setup,stops fine,,,looks ugly on the bars

[dukerollo]

I agree with the master cyl comments. On my current scoot I did not have any of the stock pieces, so I went with a 320mm Ducati rotor and a cheesy Nissan caliper. It is a lot of brake for a 350lb bike and will squeal the tire at near 100mph if you are not careful.

[vintagemotorbikes]

wow! I like the look of the ducati rotor on there though. Nissan is pretty simplistic too- looks good! Maybe just some shorty levers would tidy it up

[76cafe]

so what size bore diameter would be good? there was mention that the 14mm was the stock triumph size, how much smaller should you go?

[guschambers]

I have a 76 t140
I thought that the front brake was ok.
never really messed with it though.
The back brake always would drag and was a pain in the ass to set right though.

[Bonnevilleray]

My son has a 76 Bonnie and wanted to upgrade the brakes a little while we have it tore down We went with front and rear master cylinders from a 99 Thunderbird. Used EasyOff oven cleaner on the front to get rid of the satin black finish and polished it right up. Looks nicer but havent used it yet. They should give a firmer and quicker responce time.

[BigBenAndHisBobber]

I agree with the master cyl comments. On my current scoot I did not have any of the stock pieces, so I went with a 320mm Ducati rotor and a cheesy Nissan caliper. It is a lot of brake for a 350lb bike and will squeal the tire at near 100mph if you are not careful.

Apologies for dredging up a ten year old thread, do you have any more information on what parts you were able to fit. Are they for example standard fork sliders? I've just bought a T140 Bobber that has no front brake setup, but still has the standard hub and sliders. Thanks for any pointers.

[Dougtheinternetannoyance123]

That setup doesnt look to me to be stock forks either, Although its fairly easy to swap front ends, although fiddly, No standard procedure as it depends on stem, bearings and check if trees are raked, as some are.
But I used to swap Kawasaki KZ front ends with discs onto British bikes for people who were upgrading from drum,, its a long read on how. But many people are using modern discs (Floaters as seen in that picture) and modern calipers and Master cyls. A friend in California did one with A mix of parts, but doing the same with a 79 Cafe racer, so I bought some rotors off a Ducati, And Modern Triumph master cyl and calipers and its nice cuz it says TRIUMPH right on the calipers! But doing similar on a CB750 with modern Honda forks, wheels, and brakes.

The 2 issues you deal with, do you have a disc type wheel? Then its a matter of lining up, or machining the rotor to disc hub so the rotor bolts up perfectly centered. Then offset, line up a caliper, some make a adapter bracket for the legs, some modify the caliper. The nice thing is so many modern bikes being parted out, you have a lot of options