Topic: Rear disc convention cb750 k

[slikwilli420]

My race bike has stock drum rear and they is way more leverage than needed. It's still very easy to lock up with a shorter rear set lever.

[flybox1]

So I too am putting a rear disc on a cb750 K8 and need a little beta on mounting the master cylinder and reservoir as well as the brake linkage (how I actuate the master cylinder.

IMO, money better spend improving front suspension/braking capability.  The rear un-weights, and can loose traction quickly under hard breaking.

[SOHC4 Cafe Racer Fan]

Rookster -- nice rear brake rig and comments on leverage.  I've never had any fade issues with my rear, but it seems to be more prone to lock than a disc.

[754]

Imo   not Worth going to rear disc  , unless  you are also getting much lower Weight .. or its free..
You can find many lightweight setups and wheels to adapt, that should help handling.

[calj737]

If I'm not mistaken, the OP is getting a new Cognito conversion hub for his bike so there's little chance of persuading him to keep a drum brake. Best to focus on providing answers to his questions than dicker over the merits of his choices.

[RainCityRider]

So I too am putting a rear disc on a cb750 K8 and need a little beta on mounting the master cylinder and reservoir as well as the brake linkage (how I actuate the master cylinder.

IMO, money better spend improving front suspension/braking capability.  The rear un-weights, and can loose traction quickly under hard breaking.

I have a cognito front end already. And I bought the rear wheel, caliper, and master cylinder.
I need help mounting and getting pedal to actuate the master cylinder.
I'm all in just need guidance & pictures of people who have done this.



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[SOHC4 Cafe Racer Fan]

By the looks of the bars and tires, it looks like your bike is going for the scrambler/street tracker genre.

[RainCityRider]

By the looks of the bars and tires, it looks like your bike is going for the scrambler/street tracker genre.

Sure is!

[seanbarney41]

sweet!...awesome breaking power and tires that are a compromise on both dirt and pavement.  Good planning.

[CB_Jeff]

That Cycle X rear disk conversion kit is slick... albeit a bit pricey.  I wasn't aware that they made that.  I am inclined to reach out to Ken at Cycle X to see if that caliper and bracket would work with a spoke CB750F rear wheel that I have.  I have gathered up the parts for a rear wheel disk conversion - my hang-up has always been how to make the rear master and brake pedal work w/o significant frame mods - switching over the rear wheel and swingarm is pretty straight fwd.

[RainCityRider]

That Cycle X rear disk conversion kit is slick... albeit a bit pricey.  I wasn't aware that they made that.  I am inclined to reach out to Ken at Cycle X to see if that caliper and bracket would work with a spoke CB750F rear wheel that I have.  I have gathered up the parts for a rear wheel disk conversion - my hang-up has always been how to make the rear master and brake pedal work w/o significant frame mods - switching over the rear wheel and swingarm is pretty straight fwd.

Exactly what I'm working on.

[RainCityRider]

sweet!...awesome breaking power and tires that are a compromise on both dirt and pavement.  Good planning.

Thanks for your personal opinion......


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[HondaMan]

Rookster -- nice rear brake rig and comments on leverage.  I've never had any fade issues with my rear, but it seems to be more prone to lock than a disc.

This can be mitigated by changing the foot rod to a cable instead: the brake is already floating, so the cable preserves the brake pressure during suspension travel. We used to call this the "full floating backing plate" version, as is found on many dirt bikes. Not terribly simple to perform on the bike, but it really does work well.

[SOHC4 Cafe Racer Fan]

RCR,

Can you post a photo of the opposite side of the rear hub (rotor side)?

[Mantree]

I know this is a old thread but I came across it tooking for ideas on my rear disc conversion. I have chosen to run a harley softail rear hub laced into a 16" rear using a panhead rear brake caliper that ties in where a drumbrake brake stay arm would. I am also running forward controlls so I built my master cylinder into that with a long braded line all the way back and a banjo bolt brake switch. I am waiting on the last of the rear end components fo come in from ebay but I am also pulling my engine to replace my transmition.

[Don R]

 Remember that a brake stay that is being pushed by the caliper needs to be very sturdy, not the flat steel used on a drum. That's why the disc brake stays are on the bottom so they are in tension not compression.
 The reason it came to mind is someone reported here that he did that and had a brake stay failure on the first hard stop.

[754]

 Panheads never had a rear brake caliper.l it may have been on a pan.. but no disc brakes in those  days..

[69cb750]

Panheads never had a rear brake caliper.l it may have been on a pan.. but no disc brakes in those  days..

Panheads never had a front brake caliper either ...
Any caliper on a panhead came from some place else ...

[low-side]

For anyone else looking at a disc conversion, I used 75 F swingarm, wheel, and master cylinder.  I used plate steel to mount the master cylinder with engine mount bolts and welded pieces to the back of my brake pedal to hold an adjustable pushrod.  It worked very well and I didn't have to alter the frame.

[Mantree]

Remember that a brake stay that is being pushed by the caliper needs to be very sturdy, not the flat steel used on a drum. That's why the disc brake stays are on the bottom so they are in tension not compression.
 The reason it came to mind is someone reported here that he did that and had a brake stay failure on the first hard stop.

This one hangs extended down under the axle for the brake stay to attach to so that it puls on the stay instead of compressing it.

[Mantree]

Panheads never had a rear brake caliper.l it may have been on a pan.. but no disc brakes in those  days..

Panheads never had a front brake caliper either ...
Any caliper on a panhead came from some place else ...

You are very right it's from a shovelhead I am not good with harley engine lines because I have never been interested in owning one. The brake I picked is an after market replacment for the banana caliper that supposedly won't rattle so bad and out preform the banana caliper as well.

[754]

 Lets see the brake Is it a PM or a Jaybrake ?

[Mantree]

It's a wilwood caliper. It arrived today but I am out of state so here is the ebay photo.

[754]

Hmmmmm ...looks like a GMA  brake.. maybe Wilwood make them for GMA..ļ

[Don R]

Remember that a brake stay that is being pushed by the caliper needs to be very sturdy, not the flat steel used on a drum. That's why the disc brake stays are on the bottom so they are in tension not compression.
 The reason it came to mind is someone reported here that he did that and had a brake stay failure on the first hard stop.

This one hangs extended down under the axle for the brake stay to attach to so that it pulls on the stay instead of compressing it.

Awesome, you are in fine shape then.