Topic: Possible Major Brake Improvement?

[ProTeal55]

That rotor looks like a buell.

I thought Buell's had perimeter brakes like below....

Now that would be the ticket for a slick setup on a CB !

[cben750f0]

elder, my though its the larger piston in the master that moves the greater fluid, the standard master cyl, will work, but you end up running out of travel, b/c you need more lever travel to move the extra fluid area of the pads, the modern brake system i just a preassure intensified, and a smaller master cyl would give you more power, but we are limited by the lever travel, there fore, if you have a larger master cyl, then you 'are' goin to require slightly more pressure, but you are cancelling this out by the fact that you have another set of pads gripping rotor , as opposed to just the one....


hope that was clear...

 peace

[cb650]

That rotor looks like a buell.

I thought Buell's had perimeter brakes like below....

Now that would be the ticket for a slick setup on a CB !

The older ones didnt.   Dont know what year they changed. 


                   Terry

[KB02]

The older ones didnt.   Dont know what year they changed. 
                   Terry

I agree. I have been big fan of the Buells ever since they came out. And it's true what they say: If you want to go to a Stoppie compitition, riding a Buell is like bringing  gun to knife fight.. HOWEVER, I think the standard style disk brakes on the older models was a better brake than the new rim mounted one.

Granted the newer one does look cooler in my opinion... or at least different.

But anyway, back to that 400 set up. The rear barke on my Ducati is floating caliper, the disk is bolted directly to the rear wheel, thus maing it a good candidate for the theory (I have no intention of riping off my rear brake to try it out, though). And yes, I know that I could do a front end swap for a modern front end, but the fact is I'm looking for something simpler to do. A simple bolt on that a whole front end swap.

We'll see. My brain is still turning on this one.

[eldar]

I think we just have a misunderstanding, ben. I knew that about the standard. It just does not move enough fluid. SO you either need to have a system under more pressure OR be able to move more fluid to supply the extra pressure for the additional pads to work. We are probably thinking the same thing or close enough but you aussies think in strange ways!

[cben750f0]

here i resemble that remark!!!!!!


yeah its just diametre versus stroke.....

peace

[eldar]

I had to say it you know, after all, you live in the same island as Terry does!

[dusterdude]

let me try to help here guys,with a dual system you need to move more volume of fluid not neccesarily pressure,thats why you need a larger bore mc.

[eldar]

Well if you can move the fluid, what happens? Not enough pressure applied to the pucks. I think thats where things have been sticking on this.

[dusterdude]

tis true master eldar

[cben750f0]

thats why i said you get better effect with a smaller piston, b/c you are creating a bigger difference b/w the master cyl piston area and the total area of the brake caliper pistons.... what limits us is the lack of lever travel, hence the bigger master cyl, more fluid moved at less pressure..

peace....

never met terry, but he sounds very smart....

peace

[justfours]

I know you said you didnt want to do a front end swap,but...
In looking for the right front end for my bike, I accumulated a few sets of forks. One set that I have is (I bellieve) from a DOHC cb750 non SS, because they are for a single disc, but the caliper mounts are the same, so you could use a later 2 piston caliper and probably your stock MC. Depending on if you have spoked or mag wheels, getting it all to line up would be the hardest part. And I dont know how much of an improvement you would get by just adding a dual piston caliper and nothing else. Good luck.

[cafehonda]

I had good luck just going to a dual stock set-up with a new master off of a cbr900rr. Braided stainless lines of course. I get no more than halfway to the grip with the lever before  I can't squeeze any farther. EBC kevlar brake pads really help but you gotta deal with squeal. Grabs hard enough to lock tha front if thats what you want, but nice progressive feel.

[eldar]

Swapping brakes is nice but I would like to know if other forks can be used.

2 reasons.
1: newer forks generally have better operation and modern handling. Better rims and such.
2: how long can we keep using 30 year old forks? Sooner or later, they will wear out no matter how good you take care of them. The forces exerted on them could possibly crack them as they get older. Would be nice to know if a person could get newer forks that fit.
Our calipers will eventually die too and we need to be able to replace them with something newer.

Hope that all makes sense. I am not knockin brake swaps or anything like that.

[GoatBaSS]

Wouldnt you just need some forks that were 35mm to fit right in the trees? The CBX Lowers bolted right on to what is Ledbetters bike(75 CB750SS same 750 front end), brakes and all, just a longer brake line bolt for the extra line from the junction box. Would stop you like a brick wall, if you needed to. They were comstars though...

[jevfro]

There are some crazy custom jobs I've seen in japanese magazines (Custom People) It appears they switched out the whole front end including the trees.  The new trees were beefy billet jobs and looked sweet.  I do think you would most likely have to lose the spokes, but who knows maybe there are some modern chopper designs that are low profile enuf to keep the spokes...

[KB02]

Clean it. And I mean the whole system. Pull apart the caliper and the MC. Clean out the lines (or replace them) and use fresh fluid from a sealed container.

I had an 82 Nighthawk that kept seizing the brakes on me. I kept trying to temp fixes, but it always seized up again. When I pulled the whole syste apart, cleaned and reassembled with fresh fluid, the problem went away.

[logana]

I know this is kind of an old thread and mabey thats why what I am going to say hasn't been said. However, recently on dotheton.com (Bike of the Month winner for March) used a HD NarrowGlid front hub to gain enough clearance for GSXR calipers. Admittedly he also installed pertty much the whole GSXR front end, but my guess is that it would be possible to mount the GSXR calipers to the stock forks if you simple made an adaptor plate and there was enough room between the fork lower and the spokes (because of our conceptual hub change). Anyway, just my thought. I do have one question, how do the later 1 piston stock calipers and the even later 2 piston calipers compaire to the original 1 piston design?
Thanks Logan.

[ev0lve]

Okay, so here's my thought: 
....
   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?

Where's FishHead? 

Anyways, from his site and I think I'd believe him 
"I Have been asked to make up a Big Brake kit for the CB 750 SOHC K model This is the prototype. I doubt that I will be making any kits for the SOHC Forks because of the total end cost of the kit will far exceed replacing the front end with a(better) GL front and getting a GL Big Brake kit"
http://www.fishheadbigbrakes.com/GLbrakekits.html

I know this is kind of an old thread and mabey thats why what I am going to say hasn't been said. However, recently on dotheton.com (Bike of the Month winner for March) used a HD NarrowGlid front hub to gain enough clearance for GSXR calipers. Admittedly he also installed pertty much the whole GSXR front end, but my guess is that it would be possible to mount the GSXR calipers to the stock forks if you simple made an adaptor plate and there was enough room between the fork lower and the spokes (because of our conceptual hub change).

Industrial Cafe ran the process out pretty in-depth in this thread - Harley hub IIRC but pick through it to be sure.
http://forums.sohc4.net/index.php?topic=63784.0

[Bodi]

The problem is not pressure. Brakeline hydraulic pressure is proportional only to lever force, M/C piston diameter, and brake lever mechanical ratio. What differs is the volume required to operate the brake and the braking effect produced with a given pressure. If you add a second identical rotor and caliper to a CBxxx brake you will double the braking power for a given lever force. It will also take twice as much brake fluid volume to move the pads onto the disks. Once the lever hits the bar you don't have any more volume available. There are two solutions: increasing M/C piston stroke and lowering the lever mechanical advantage, or using a larger diameter M/C cylinder. Both reduce the hydraulic pressure for a constant lever force. If you double the brake pad swept area you will increase maximum brake power. If you match that with the correct M/C you will be able to use it all. The wrong M/C will be very hard to squeeze hard enough to get maximum braking (skid or stoppie) or have the lever tight to the bar before that point.

[fishhead]

Where's FishHead? 

Anyways, from his site and I think I'd believe him 
"I Have been asked to make up a Big Brake kit for the CB 750 SOHC K model This is the prototype. I doubt that I will be making any kits for the SOHC Forks because of the total end cost of the kit will far exceed replacing the front end with a(better) GL front and getting a GL Big Brake kit"
http://www.fishheadbigbrakes.com/GLbrakekits.html

I prefer the GL 1000 front end because it is a lot wider than the CB front end, has sturdier 37mm tubes and most important, the caliper mounts are on the back of the fork legs instead of inside the fork legs. The CB caliper mounts (inside the fork leg) take up valuable "real estate" when trying to do this type of conversions. The caliper mount and the disc want to be in the same area and cant be. If you move the disc in to give more clearance for the caliper mount, then the caliper starts hitting the spokes. On any fork assembly, there is only so much room to work with and with a wider set of forks, there is more room to play with, not to mention the "better placed" caliper mounts of the GL forks.

For reference the CB "big brake" prototype above has a 320mm disc.

Here's a few pics of a GL 1000 front end with 6 piston calipers.
   The titles of the pics states that they are either 310mm discs or 330 mm discs(2 different kits are shown). The "clearance" pics are of the 310 mm disc set up. Notice the clearance between the caliper and spokes/the disc and fork leg. I'm not going to say that the same can't be done with the CB fork legs, but it is more feasible with the wider GL forks.

 Using the 330 mm discs put the calipers further away from the center of the wheel and also gave more available clearance (spoke to caliper/disc to fork leg). Using the wider GL fork legs helps make this custom brake kit possible.

 

   

[Old Scrambler]

Basic Improvement:  Use best pads and apply more pressure sooner with SS lines.

K0-K6 & F0-F1; add second disk to stock legs for double the braking pleasure - works with standard MC with splitter at switch.  K7-K8 will need replacement legs as they have no right-side lugs.

Use SS brake lines to eliminate line expansion that often requires a larger MC

Install a GL1000 '75-'77 front end with wire-spoked wheel, double disks and larger MC - Better brakes and less fork flex due to 37mm tubes and stronger axle mounts with a slightly wider triple-tree.  Use GL speedo drive.

High Performance - Use GL1000 front end and increase the radius of the disk and mount free-floating double or triple calipers.....$$$$$.  Mount low-profile tires for less flex and faster brake response.

[Anti-Johnny]

I am still educating myself on how these brakes work. I may be off or misunderstanding. But lordmember added a modern caliper to his bike by welding a bracket to the fork. Would this be a way to add more braking power easily?

My front brake lever is quite stiff, and I am reading up on ways to increase braking power.

You guys seem to be the ones to ask, how much better is the braking with the dual disc mod? I am looking for easy to understand instructions(noob). Would that be easier than trying to find a modern brake that would work?

[odiewan]

My CB750 has, as far as I can tell, a front end off of a GS750 or GS850. Twin rotors and two single piston calipers.

The braking is pretty bad, but I don't know if the MC is the one that came with the forks or the stock off the CB and the pads have been contaminated with grease and who knows what else.

I am going to try a stock MC off my 2002 SV which had a similar configuration (two rotors, two single piston calipers). The key is if the total caliper piston area vs MC piston area is appropriate.

I am going to go with a full set of SS lines and some EBC pads.  Then next thing to do is get a Brembo radial MC.

The next thing one could do is see if there are larger diameter rotors available that will bolt on. That will give you a big improvement in braking, especially with these large diameter wheels (as compared to a modern sport bike).

[logana]

I don't see why simply welding a bracket to your existing fork lowers wouldn't work. So long as you are aware of warping/causeing damage to the fork lower. Moreover, the joint is going to take alot of force when you apply your brakes, so you might consider having it done professionally. As far as the second disc brake, if understand it correctly it should yield roughly double the braking power. However, it may might require you to change out your master cylinder. (2 calipers take twice as much brake fluid volume to engage correctly.)