Topic: Possible Major Brake Improvement?

[KB02]

Okay, so here's my thought: 
   One of the biggest complaints we seem to have about our bikes is that the brakes pale in comparison to modern rides. All things being equal, the disk itself shouldn't be the issue (as long as it is in good condition), it would be the MC and Caliper that is simply weaker than want we want, right? Switching out the MC is easy and has been done many a time before by many people (including myself). But we always end up being limited by that single pot caliper.
   Why can't we put a modern caliper on these bikes?
   Aside from the obious, "They don't make one," what is to stop us? All we would need is modern, floating, caliper and a little time with a creative machinist, right? (My dad is a Machinist, that's what I think of things.) With the 750's specifically, there is that arm that reaches out from the fork that holds the caliper. A redesign of that arm with the end designed to hold a modern floating caliper (and pssible the removal of the swivel part) would allow the use of that modern caliper on the old bike. Match that with the newer MC and all of a sudden we have modern brakes on a 30 year old bike.

   What do you all think? Am I on the right track? Am I totally off base? Has someone already thought of this years ago and I'm way behind the times?

   Let me know what you all think

[sparty]

If you can engineer the part, I'd buy it.  I posted a similar complaint about our poor brakes.

Sparty

[Roach Carver]

I think it sound like a great idea. There used to be a guy that made kits for the xs650 that had a floating rotor and modern caliper.  If you make 2 sets I will be happy to do some r and d for ya.

[KB02]

Just some pics to add to the thinking:

[MRieck]

 The biggest problem I've seen is lack of clearance between spokes and the backs of 4 piston calipers.

[putnaja1]

I'd like to see better brakes for a SOHC too!

Just a couple of thoughts I have on this topic:

1)  The later year, DOHC CB750F and CB900F models, which came right after the end of SOHC4 line, had dual piston calipers.  They started out in 1979 with single piston calipers, but then went to dual in 1981 (I think!  They certainly had them in 1982)  Since the later year SOHC4 F models had the comstar rims that the DOHC CB's had, I wonder if it would be an easy, drop-in solution to use those calipers on the SOHC bikes?  We might need to use an upgraded master cylinder, perhaps..  Also, anyone know about whether the same fork legs are used between spoke rim'd SOHC4s and Comstar rim models?  If the same forks are used, then it would seem to definately be an easy swap!  Hopefully..

2)  I read somewhere that motorcycles are designed as an entire system- so that, for example, putting really wide tires and super beefy upside-down forks on a SOHC4 bike might be detrimental to handling, because a certain degree of fork flex was anticipated in the front end, and the frame was possibly designed to compensate for it.  Long story short- would vastly improving the brakes cause problems with other systems on the motorcycle?  I'm probably overthinking this, but thought I'd post it anyway..  I'm hoping enough extra strength was engineered into the fork and frame to be able to handle lots of extra braking ability without problems..

Jason

[tsflstb]

The biggest problem I've seen is lack of clearance between spokes and the backs of 4 piston calipers.

That's the rub.  I've got some spare CBR900RR calipers I"ve been dying to fab up and mount, but I see no way to do it with the spoked wheels (I want to keep spokes).  Those calipers are huge and offset much more to the inside.  I've spent hours in the garage holding up the caliper to my forks and scratching my head over this one.  There's plenty of meat on a stock hub to drill and bolt up a 320mm rotor to match.  Just using a single 320mm disk and the matching caliper would be great.  Using both could probably detach your retinas.

There are probably some smaller dirt bike style calipers that would clear the spokes, but I don't think they'd be much of an improvement.  I saw one 400F with brakes from a Honda 125 GP racing motorcycle, but those kinds of parts are kind of pricey for us ebay scroungers.

[cb650]

I'd like to see better brakes for a SOHC too!

Just a couple of thoughts I have on this topic:

1)  The later year, DOHC CB750F and CB900F models, which came right after the end of SOHC4 line, had dual piston calipers.  They started out in 1979 with single piston calipers, but then went to dual in 1981 (I think!  They certainly had them in 1982)  Since the later year SOHC4 F models had the comstar rims that the DOHC CB's had, I wonder if it would be an easy, drop-in solution to use those calipers on the SOHC bikes?  We might need to use an upgraded master cylinder, perhaps..  Also, anyone know about whether the same fork legs are used between spoke rim'd SOHC4s and Comstar rim models?  If the same forks are used, then it would seem to definately be an easy swap!  Hopefully..


Jason

82 was the first year. And they do apear to bolt right on to the 81s.




                           Terry

[scondon]

I'd like to see better brakes for a SOHC too!

Just a couple of thoughts I have on this topic:

1)  The later year, DOHC CB750F and CB900F models, which came right after the end of SOHC4 line, had dual piston calipers.  They started out in 1979 with single piston calipers, but then went to dual in 1981 (I think!  They certainly had them in 1982)  Since the later year SOHC4 F models had the comstar rims that the DOHC CB's had, I wonder if it would be an easy, drop-in solution to use those calipers on the SOHC bikes?  We might need to use an upgraded master cylinder, perhaps..  Also, anyone know about whether the same fork legs are used between spoke rim'd SOHC4s and Comstar rim models?  If the same forks are used, then it would seem to definately be an easy swap!  Hopefully..


Jason

82 was the first year. And they do apear to bolt right on to the 81s.




 Terry

      The 82 750/900 Supersport brakes bolt right to the 77-78 750F forks. You do need the 82 mounting brackets as well. Most all the 82 Honda models used this dual caliper brake but the Supersport models are the only ones i've found so far that have the right brackets.

      The 77-78 750F has different fork lowers than all the other SOHC 750's. The calipers mount at the rear of the fork leg and the disks are different. I think it would be difficult indeed to find a modern "bolt on" caliper for the 69-78 K's and 75-76 F's.

[cben750f0]

i have seen a set of fork plate off an early race bike that bolted to the fork legs, with apropriate shims, and a single piston brembo caliper was used, so the answer is it was done a long time agon, by brembo, i wonder if they are into making them gain...

the only reason i know this, was b/c there was a set on ebay a long while back, and i got sniped on them.... ..

 so as long as the caliper clears the spokes, and everything is set up properly, there shouldnt be any reason why you couldnt.... just  matter of finding the right calipers..... BTW has anyone thought of using any of the modern floating rear caliper off a modern bike.... was haveing a look at my cbr and thought perhaps they might be usefull....


peace

[DammitDan]

My '82 CB650 had spoke rims and a dual piston caliper that bolted straight to the leg. (although I only had a single caliper)

The forks are air-assist and about 3" shorter than older models though.

[KB02]

In the pic of that 82 CB900, is that a dual piston caliper or a four piston job?

[scondon]

In the pic of that 82 CB900, is that a dual piston caliper or a four piston job?

    If you're referring to my pic those are dual piston calipers mounted to my '78 750F.

[dusterdude]

since we`re on the subject,any ideas for an early gw front end?

[eldar]

How about late model part models? Say a using the forks and such off a newer bike. I mean there has to be something out there that uses forks that will mount into our trees or int othe neck and where the rear wheel fits into our swingarm or we can mount a different swing arm.

Has anyone done that? cause if we could do that, we could get better wheels and such, technically speaking

[techy5025]

I have yet to hear a technical explanation of why changing out the master cylinder does anything to
improve breaking force. Certainly adding more pistons/pads to increase the surface area contacting the disk
helps. I also don't see why adding more pistons radially would cause problems with spoke clearance. It
sounds like we need a master machinist to come up with a new caliper design....maybe a "sandcast"
one. 

Jim

[eldar]

Well techie, with the master, the piston that moves the fluid, is made to move a greater amount of fluid in modern designs, this great fluid push, increases the pressure in the brake line, thus providing more pressure on the pads.

More pads make better use of this pressure than 1 can.

I have not looked into a new style caliper though, to see why they extend futher into the wheel and cause clearance issues.

[techy5025]

To move more fluid requires either a larger bore in the master cylinder or a reduced ratio
of lever arm lengths (brake lever length you grip/length from bolt pivot to master cylinder piston).
Either of these will require more force as they decrease the mechanical advantage. Leaving out losses,
doubling the caliper pistons doubles the force on the disk for the same force on the brake lever.

The idea is to get more force on the disk with the same force on the brake lever.  Moving more fluid
for the same displacement on the brake lever doesn't do it.

Jim

[tsflstb]

I started scrounging around and found this conversion for a CB400F.  It's a japanese site linked on eaglescall.com.  I can't read the details and don't really recognize the caliper, but it's not the big mack daddy six piston variety.  Looks more like something off a smaller more modern bike.  It's mounted up in basically the stock location, just higher to clear the larger diameter rotor.  The big rotor is pretty nice. 

I'm sure it works better than stock, but the kit sells for about 85,000 yen = $750.  

[sparty]

Great detective work.

Hmmmm. That still looks like a single piston caliper???  Because of it's low profile, I can't see it having a piston in the rear (inside).

Sparty

[KB02]

actually looks allot like the rear caliper opn my Ducati. Dual piston, one on each side.

[ProTeal55]

Couldn't you find a newer set of lower legs that will accept the stock Honda fork tubes ?
You would prob. have to run the donor bike front wheel , but that would give you the newer brakes. I know OHIOCAFERACER has a bike where he swapped a newer GSXR front-end on his scoot.

[cben750f0]

just a question, dont cbr250's have the same diametre fork tubes, the RR version was double disc.... NEway, i cant say for sure, just something that i am trying to remember.... also that CB400 set up looks like a brmbo rear caliper off a modern bike.... and the bigger disc would push the caliper higher, making clearance less of an issue on the spokes....  you could always do a 35mm fork search on ebay, and see what comes up


peace

[eldar]

well I guess I didnt feel the need to state the obvious, techie. Of course you would need a larger piston or longer piston travel to move more fluid. But moving more fluid through the same diameter hose into a like sized area, WILL increase the pressure in the system. But modern brakes work by using larger amounts of surface area, not tremendous amounts of pressure.

The added fluid movement is required though to achieve the desired pressure of the pad on the rotor.  I am not going to waste my night on math but in theory, if you double the pad area, you double your braking force, now I am sure the math works out to less than that but again, I am not going to waste my time. Fact is, more pads produce better stopping power, there is a certain point I am sure where it does not matter, but more pads require more fluid to be moved in order to achieve the amount of pressure required to produce the needed friction.

We all know this, which is why so many do dual caliper set-ups or try to graft on dual puck systems, you will notice that those who do this, rarely use the stock master as it cannot move enough fluid to make the change worth anything. It cannot move enough fluid to build up the required PRESSURE.

[cb650]

That rotor looks like a buell.




                      Terry