Topic: rear disc brake swap

[thelowmax]

I'm wondering what it would take to switch the rear drum brake on my 78 CB750k with the disc brake from a supersport of the same era? Is it possible?  I've been studying pictures and diagrams on bikebandit but haven't actually seen one in person for a while.

My next inquiry is about the cycle-x rear disc brake conversion kit. Anybody have one?

The issue is that I can buy a whole Supersport (not running but clean) or the conversion kit. They both will cost about the same (bike is actually cheaper). Any input or information would be helpful.

[DavePhipps]

Get the BIKE!!!!!!
It shouldn't be too hard. There have been swingarm swaps from completely different bikes done fairly easily.
The big plus is the guys here might bw able to help get the SS running.

[thelowmax]

I saw the bike, and spoke to the guy for about 15 minutes. Then, the guy wouldn't sell for the price he was originally asking because I told him I really only wanted the rear tire and braking system (shouldn't the price go down?). He immediately put the price for the entire bike on just what I wanted. Then he said I could take the stuff off myself. When I said I would take the whole bike, his price went through the roof, like he was selling each part individually. I offered the original price for the whole bike and he laughed. I just turned around and walked away. As I did, he followed saying, "don't be like that. Let's work something out". As I continued to walk away I thought to myself, "I don't want to have anything to do with this guy's messed up karma".


So, now I'm wondering... Anybody got a Supersport spoked rear tire with a disc rotor they want to part with?

[MCRider]

My problem with both the F rear brake and the CycleX conversion is they are huge humky pieces of hardware, much more brake than necessary. I'd like to know what salvage parts would make a neater smaller package? In the interest of not being a thread hijacker, it seems there are enough parts, or close to it, on eBay right now to do the conversion for about $125. But i don't know about the pedal and linkage. I think the pedals between the F and the K are significantly different.

I was looking for 1975F parts for the spoked wheel.

[thelowmax]

My problem with both the F rear brake and the CycleX conversion is they are huge humky pieces of hardware, much more brake than necessary.

Though it is a lot more brake than necessary, I'ld rather have it and not need it than need it and not have it.  

It is a lot of hardware. And when it's all polished up it looks really, really cool.

I realize my desires aren't conventional but I've got a stock 78 cb750, so this one is going to have the bells and whistles. With a 16" rim in the back, the disc rotor would practically cover the spokes. That coupled with a 21" front  rim will be anything but sensible.

I've been looking at the parts on ebay but my inability to find a spoked rear tire with the disc rotor and the lack of understanding of how the wheel is attached to the disc has me putting this part of the project on the backburner. It's difficult to assess the situation on the bikebandit exploded parts charts. Any idea? The cycle X system fits right into the hub just like the original drum brake. Is that how the supersports rear disc is too?

[MCRider]

My problem with both the F rear brake and the CycleX conversion is they are huge humky pieces of hardware, much more brake than necessary.

Though it is a lot more brake than necessary, I'ld rather have it and not need it than need it and not have it.  

It is a lot of hardware. And when it's all polished up it looks really, really cool.

I realize my desires aren't conventional but I've got a stock 78 cb750, so this one is going to have the bells and whistles. With a 16" rim in the back, the disc rotor would practically cover the spokes. That coupled with a 21" front  rim will be anything but sensible.

I've been looking at the parts on ebay but my inability to find a spoked rear tire with the disc rotor and the lack of understanding of how the wheel is attached to the disc has me putting this part of the project on the backburner. It's difficult to assess the situation on the bikebandit exploded parts charts. Any idea? The cycle X system fits right into the hub just like the original drum brake. Is that how the supersports rear disc is too?

Understood, its your personal design issue. Mine would be a function issue wanting the least weight possible.

The 75F disc setup is a hub that is unique to the 75/76 Fs. it is obviously for a spoked wheel, and has a carrier on the left for the sprocket and a carrier on the right for the rotor. the rotor carrier is part of the hub, unlike the sprocket carrier which is removable.. You would likely need the whole wheel, consisting of Hub, spokes, rim, and sprocket carrier. axle and spacers, and chain adjusters. Then have your own spacers made up to get it centered and in the K swingarm. On the F, the spacer on the right is actually part of the arm that carries the caliper. You may have to have that arm milled to size.

I think it would be relatively easy as these things go, but you'd need the whole wheel/rotor/caliper/master cylinder/brakepedal, to make it so.

With the 16/21" combo you're obviously going for a chopper or bobber style and the CycleX brake is down your alley I'd think.

[Sam Green Racing]

My problem with both the F rear brake and the CycleX conversion is they are huge humky pieces of hardware, much more brake than necessary.

Though it is a lot more brake than necessary, I'ld rather have it and not need it than need it and not have it.  

It is a lot of hardware. And when it's all polished up it looks really, really cool.

I realize my desires aren't conventional but I've got a stock 78 cb750, so this one is going to have the bells and whistles. With a 16" rim in the back, the disc rotor would practically cover the spokes. That coupled with a 21" front  rim will be anything but sensible.

I've been looking at the parts on ebay but my inability to find a spoked rear tire with the disc rotor and the lack of understanding of how the wheel is attached to the disc has me putting this part of the project on the backburner. It's difficult to assess the situation on the bikebandit exploded parts charts. Any idea? The cycle X system fits right into the hub just like the original drum brake. Is that how the supersports rear disc is too?

Andrew, had you asked a few weeks ago you could have taken a look at mine, it was sat in Boston at the begining of the month.
The CycleX system bolts into the hub from the sprocket carrier side. It's a very well made unit but heavy.
I chose it for a reason but on your average street bike the drum brake is more than adequate.

Sam.

Some pics of brake fitted Andrew, not connected up yet though. http://forums.sohc4.net/index.php?topic=61876.325

[voxonda]

Am building a (vey) light version now, with a front 750 hub, light 240 mm disk and a transmission damper. It is done before, but doing it  'my way' (thanks Frankie)

rob

[turboguzzi]

Am building a (vey) light version now, with a front 750 hub, light 240 mm disk and a transmission damper. It is done before, but doing it  'my way' (thanks Frankie)

rob

common practice here too, just make sure to add a third bearing for the sprocket, the chain pull will kill the single left bearing if not and dont ask how i know

where is that 240mm disc from, any stock model?  need one....

[voxonda]

I put in different bearings and a extra bigger one in the damper. Ducati, Voxan. 240 m/m just 4 m/m thick.

[turboguzzi]

just checked, damn, it'll have to be a 250-255, otherwise the caliper touches the disc bolt bosses on the wheel  

Seen at least two front hubs used at the rear wheel break the left bearing but they were not using the third bearing for the sprocket carrier, so make sure you use one when you put in a front hub a 20mm axle the 6004 bearings are quite weak compared to stock, have a set in front of me right now

[Retro Rocket]

My problem with both the F rear brake and the CycleX conversion is they are huge humky pieces of hardware, much more brake than necessary.

Though it is a lot more brake than necessary, I'ld rather have it and not need it than need it and not have it.  

It is a lot of hardware. And when it's all polished up it looks really, really cool.

I realize my desires aren't conventional but I've got a stock 78 cb750, so this one is going to have the bells and whistles. With a 16" rim in the back, the disc rotor would practically cover the spokes. That coupled with a 21" front  rim will be anything but sensible.

I've been looking at the parts on ebay but my inability to find a spoked rear tire with the disc rotor and the lack of understanding of how the wheel is attached to the disc has me putting this part of the project on the backburner. It's difficult to assess the situation on the bikebandit exploded parts charts. Any idea? The cycle X system fits right into the hub just like the original drum brake. Is that how the supersports rear disc is too?

The back brake does not need to be all that efficient, if you are not using about 90% front brake when stopping you are not braking correctly. Being heavy on the rear brake will get you killed. I have seen people die because of poor brake use, one was right in front of me, it was a Harley and its weight still wouldn't help it stop any faster on the back brake and he run up the back of a boat on a trailer and the bottom of the motor almost cut his chest in half length ways. Learn to use the front brake properly or face the consequences, a simple rider training course will help.
Back on topic, I have a 70's Hurst Airheart rear disc set up that i will be using on my "F" build...

Mick

[MCRider]

My problem with both the F rear brake and the CycleX conversion is they are huge humky pieces of hardware, much more brake than necessary.

Though it is a lot more brake than necessary, I'ld rather have it and not need it than need it and not have it.  

It is a lot of hardware. And when it's all polished up it looks really, really cool.

I realize my desires aren't conventional but I've got a stock 78 cb750, so this one is going to have the bells and whistles. With a 16" rim in the back, the disc rotor would practically cover the spokes. That coupled with a 21" front  rim will be anything but sensible.

I've been looking at the parts on ebay but my inability to find a spoked rear tire with the disc rotor and the lack of understanding of how the wheel is attached to the disc has me putting this part of the project on the backburner. It's difficult to assess the situation on the bikebandit exploded parts charts. Any idea? The cycle X system fits right into the hub just like the original drum brake. Is that how the supersports rear disc is too?

The back brake does not need to be all that efficient, if you are not using about 90% front brake when stopping you are not braking correctly. Being heavy on the rear brake will get you killed. I have seen people die because of poor brake use, one was right in front of me, it was a Harley and its weight still wouldn't help it stop any faster on the back brake and he run up the back of a boat on a trailer and the bottom of the motor almost cut his chest in half length ways. Learn to use the front brake properly or face the consequences, a simple rider training course will help.
Back on topic, I have a 70's Hurst Airheart rear disc set up that i will be using on my "F" build...

Mick

Thanks for the comments on the rear brake and braking. I couldn't agree more.

Was the F rear brake one of the first on a production machine? I think so. I remember Hurst AH from the 70s. Will your HAH set up be going on a spoked wheel? I'm going to start searching eBay etc for a HAH brake for my 75F. Is the 75F known as the F1, or is it an SS?. I remember they supplied brakes for various aftermarket cast wheels. Small efficient units I think.

[Retro Rocket]

My problem with both the F rear brake and the CycleX conversion is they are huge humky pieces of hardware, much more brake than necessary.

Though it is a lot more brake than necessary, I'ld rather have it and not need it than need it and not have it.  

It is a lot of hardware. And when it's all polished up it looks really, really cool.

I realize my desires aren't conventional but I've got a stock 78 cb750, so this one is going to have the bells and whistles. With a 16" rim in the back, the disc rotor would practically cover the spokes. That coupled with a 21" front  rim will be anything but sensible.

I've been looking at the parts on ebay but my inability to find a spoked rear tire with the disc rotor and the lack of understanding of how the wheel is attached to the disc has me putting this part of the project on the backburner. It's difficult to assess the situation on the bikebandit exploded parts charts. Any idea? The cycle X system fits right into the hub just like the original drum brake. Is that how the supersports rear disc is too?

The back brake does not need to be all that efficient, if you are not using about 90% front brake when stopping you are not braking correctly. Being heavy on the rear brake will get you killed. I have seen people die because of poor brake use, one was right in front of me, it was a Harley and its weight still wouldn't help it stop any faster on the back brake and he run up the back of a boat on a trailer and the bottom of the motor almost cut his chest in half length ways. Learn to use the front brake properly or face the consequences, a simple rider training course will help.
Back on topic, I have a 70's Hurst Airheart rear disc set up that i will be using on my "F" build...

Mick

Thanks for the comments on the rear brake and braking. I couldn't agree more.

Was the F rear brake one of the first on a production machine? I think so. I remember Hurst AH from the 70s. Will your HAH set up be going on a spoked wheel? I'm going to start searching eBay etc for a HAH brake for my 75F. Is the 75F known as the F1, or is it an SS?. I remember they supplied brakes for various aftermarket cast wheels. Small efficient units I think.

Hi MC, It is on a spoked wheel now, mine is the first model "F" bike. It uses a nice thin disc and the calliper isn't anywhere near as big as the Honda item. I also have some GSXR wheels that i may use on the bike depending on which style of build i go for on this bike, i may even be interested in selling the whole Hurst set up.....let me have a think about it....

Mick

[MCRider]

Pardon to ...lowmax for the thread jack. Quick finish to Mick. I expect I can get my machine shop to mod an adapter to put a small disc on my 75F, and mod the caliper holder for a smaller caliper. CBR or GSXR types. I'd consider the HAH unit but shipping is problem, perhaps.

[Retro Rocket]

Pardon to ...lowmax for the thread jack. Quick finish to Mick. I expect I can get my machine shop to mod an adapter to put a small disc on my 75F, and mod the caliper holder for a smaller caliper. CBR or GSXR types. I'd consider the HAH unit but shipping is problem, perhaps.

Yes, sorry for the hijack mate. I will talk to Terry about shipping and get back to you...In pm's

Mick

[fishhead]

Using an F Model rear disc wheel would be the "easiest" way to get the rear discs done. I think I had to machine some of the caliper mount away and use the K sprocket mount to get it to fit the K swing arm.(1st pic). I may have had to make new axle spacers also to get the wheel centered.

On my bike I used a K front hub mounted to an 18 inch hoop and machined adapters to get it to fit/work. An extra bearing is also installed in the sprocket adapter. (2nd- 4th pic)

The 5th pic shows a 1975 GL 1000 rear disc "Fishhead" braking system. The same could be accomplished with the 750F as it is very similar to the GL , just mounted on the other side of the wheel.

[voxonda]

Hey Fishhead,

Really like your work. It is similar to what I do, almost everything can be made fit. One question, why not run a cushdrive on your setup with the front hub?

Cheers, Rob

[turboguzzi]

cool fish, but why such big discs? looks like you could lock the wheel by just caressing the pedal...

TG

[thelowmax]

Pardon to ...lowmax for the thread jack. Quick finish to Mick. I expect I can get my machine shop to mod an adapter to put a small disc on my 75F, and mod the caliper holder for a smaller caliper. CBR or GSXR types. I'd consider the HAH unit but shipping is problem, perhaps.

No worries. Seems like it's all relatively on topic. Although, I am starting to rethink the whole idea.

Maybe I should get all my bikes going before I start modifying how they stop.

[fishhead]

My front hub/rear wheel replaced a Shelby-Dowd wheel that also didn't have a cush drive. My wheel works fine, but I do pay attention to it more to be on the safe side (spokes). It also has steel pins that locate the sprocket adapter to the hub (between the bolts, to take the grunt of the rotational torque off the bolts that hold it all together).

  The "big" discs just look like they are big. They are actually about the same size as the stock F and GL rear disc, just a lot lighter.
   This pic shows the new "big" disc mounted with the stock caliper (GL 1000). The pads on the stock GL caliper would hit the buttons on the disc and couldn't be used like this (and the new discs is a lot thinner than what it replaces).

  

[750essess]

Has anybody found a lighter rotor off of some other bike that fits on an f rear wheel?

[MCRider]

Has anybody found a lighter rotor off of some other bike that fits on an f rear wheel?

That's my question too. If its just lighter we want, then drilling and thinning the stocker like Fishhead, would be the way to go.

If its the whole smaller look, with caliper and everything, we've got some machine work to do.

[thelowmax]

Using an F Model rear disc wheel would be the "easiest" way to get the rear discs done. I think I had to machine some of the caliper mount away and use the K sprocket mount to get it to fit the K swing arm.(1st pic). I may have had to make new axle spacers also to get the wheel centered.

On my bike I used a K front hub mounted to an 18 inch hoop and machined adapters to get it to fit/work. An extra bearing is also installed in the sprocket adapter. (2nd- 4th pic)

The 5th pic shows a 1975 GL 1000 rear disc "Fishhead" braking system. The same could be accomplished with the 750F as it is very similar to the GL , just mounted on the other side of the wheel.

Holy Cow! You answered my question and then some. Nice work.

[MCRider]

I keep forgetting the resources we have here at SOHC4.

http://www.fishheadbigbrakes.com/