Topic: Brakes!!!

[lefty2023]

I have a stock cb 550k that is used as a daily rider and a project bike. I need better braking power for panic stops. Ive spent a few days searching and didn't coming up with much. I was thinking about doing a stain
less steel line and a drilled rotor for fun but I know that's not going to decrease my stopping distance a ton.  I can't even find a drilled rotor that fits that bike. Anyone have know
)w a company that makes direct bolt on brakes. Let me know please, I'm struggling o find brake parts

[77cafe750]

i have pads availble and you can drill your own rotor there are patterns availbele fromsome of the people on here and on the web peace crash

[Spanner 1]

New front brake line(s) make a world of difference to stopping power ( don't have to be stainless ) along with no air in the system and a good master cylinder seal (new). The other thing that helps stopping power is 'heavy' use of the front brake on a goodly run ( 100 miles?).... the brake will get better and better... IMO.
Drilled rotor = no effect on braking, just cosmetics ( if you like it ).

[AnthonyMichael]

know a good site to get cb750k brake lines?

[lefty2023]

Alright ill get some new lines and check out that seal. I called a brake shop to see how much it costs to get rotors drilled and they said u cant drill used rotors successfullybecause they will crack, is this  true? I'm sure people will have opinions on both but I want to do it the right way and not twice

[BlindJoe]

know a good site to get cb750k brake lines?

http://forums.sohc4.net/index.php?topic=54790.0

[MCRider]

You can drill old CB rotors till your blue in the face. Your shop just isn't familiar. But to your question. Many have lamented on the weak disc brakes of the 500/550.

You can improve the feel especially over rubber lines that are 10+ years old with stainless braided line and unless you want to stay OEM you should. You can experiemtn with pad makeup, but I'm not convinced that on the OEM rotors anything works better than OEM.

But to actually INCREASE the braking force you must increase the force coming out of the master cylinder. That is the point of origin of braking force. Everything else including dual discs, improves feel, fade resistance, stability, but does not increase the actual bottom line force.

And/or you must change the braking material of the rotor itself. As you have found there is not much available for the 500/550. EBC makes a rotor for some, but not all, models of the CB750 which is advertised to increase braking by 15%.

Honda and others use stainless steel rotors as they look good and don't rust. Cast iron is the best material but rusts quickly and looks terrible in the showroom. But no holds barred sport bikes like some Ducatis and custom race bikes use cast iron as they don't care what it looks like. My FJR has a cast iron alloy and will rust up if it sits too long.

I've always wondered what putting a dual disc master cylinder on a single disc would feel like.

That's what I would do if I were you (experiment) and what i intend to do on my next project.

[camelman]

I don't agree on a drilled disk not making any difference on braking performance.  The holes will allow dust and steam to be cleaned off from under the pad, which will increase effective braking force.  The improvement won't be very noticeable when it is dry out, but it will be very noticeable when it is wet out.  In the rain/wet, your disk will be almost ineffective until the water is removed from the surface.  That takes a while if you don't have holes in the rotor for the center of the pad to vent to.

My next build (now that I have a job again) will include a modern sport bike front end with a modern brake.  However, if I was to stay with the stock systems, then I would choose a dual disk setup and stainless lines to improve the braking.  The stainless lines will give a better feel and decrease the throw of the brake lever, and the double disk will double the braking surface to double the braking force for the same amount of pressure on the brake lever.

What is your budget to improve your braking performance?

Camelman

[Kevin400F]

A good recipe is: drilled OEM rotor with an appropriate hole pattern which doesn't leave any portion of the pad "unswept", Ferodo Platinum brake pads, modern smaller bore (the important part) master cylinder, braided-stainless-covered lines. 

If you can find an MC with integral brake light switch, or use one of those nifty banjo bolts with integral switch, run a new one-piece brake line from the MC directly to the OEM caliper, using the appropriate fittings.

[Spanner 1]

I'd be sceptical about a twin disc set-up being any more effective a brake than a single disc with the same master cylinder.... the pressure on each piston would be halved, which would void the double pad to disk area advantage..... ya? 

[scottly]

I'd be sceptical about a twin disc set-up being any more effective a brake than a single disc with the same master cylinder.... the pressure on each piston would be halved, which would void the double pad to disk area advantage..... ya? 

Naw, the pressure is the same on both pistons, so the braking force is doubled. I had a set-up like this on my bike, and it was like having power brakes. Two fingers on the brake lever was enough for most braking.

[Spanner 1]

Yeah, but with the same master cylinder ??

[scottly]

Yeah, but with the same master cylinder ??

Yes, two calipers with the single caliper master cylinder. The brake handle moves twice as far; it doubles the "leverage".

[Spanner 1]

Can't get my head around that!.. as the m/c volume is the same and only moves a fixed amount of fluid and with 2 pistons your asking it to apply that fluid into 2 calipers which must 1/2 half the pressure in each brake cylinder..... huh?... i.e. the brake pad pressure to disc would be half what it would be with a single disc.

[Kevin400F]

Keep thinkin' about it, Spanner 1.  You'll get it eventually.

For a given master cylinder, the same sqeeze on the lever develops the same pressure in the line each and every time...it doesn't matter if there is one caliper hooked on the end of the line or two.  You'll get a bit more lever travel since you have to move two sets of pads into contact with the discs, but once the pads are hard on the discs and you're squeezin' the lever like always....fluid pressure is same thoughout the system.  Two discs = twice the braking force. 

Does that help?  If not, someone smarter than me can take over.....Bryan?

[scottly]

Can't get my head around that!.. as the m/c volume is the same and only moves a fixed amount of fluid and with 2 pistons your asking it to apply that fluid into 2 calipers which must 1/2 half the pressure in each brake cylinder..... huh?... i.e. the brake pad pressure to disc would be half what it would be with a single disc.

Ah, I see your problem. Yes, 1/2 the Volume goes to each piston,(why the lever moves twice as far) but the PRESSURE is the same to both pistons.

[Spanner 1]

O.K., got it.... the variable is the lever travel then, double disc will take 2x volume of fluid ( 2 times the lever travel ) to apply the same pressure on the 2 pads compared to 1.... very interesting !!

[scottly]

Now you got it! Brake math simplified: 1 disc/caliper + 1 disc/caliper + 1 hand-full of brake lever = nose-wheelie.

[Spanner 1]

So, to restore minimal brake lever travel vs. braking effect a larger diameter master cyl. should be used for a twin disc set-up.... less piston travel for same volume of fluid moved, right?

[scottly]

So, to restore minimal brake lever travel vs. braking effect a larger diameter master cyl. should be used for a twin disc set-up.... less piston travel for same volume of fluid moved, right?

Yes, a larger MC piston will reduce the lever travel, but also reduce the mechanical advantage. You get used to the stock MC, it is really quit controllable. 

[MCRider]

I started a thread on this some time ago, and many responded with deep math etc. Essentially, The force coming out of the MC cannot be increased by increasing the braking area. Increasing the braking area simply spreads out the available force. Heat will dissipate faster. Wear will be distributed and reduced. But one time panic force braking is the same, one disc or two.

Bottom line you do not double braking force by adding a disc to an otherwise unchanged system.

The pressure coming out of the MC is the same, but its spread out over more braking area so the end PSI reduces accordingly.

[Spanner 1]

So was my first hypothesis correct, before I was sold otherwise ?.... even with 2 x times the lever travel it's no advantage having 2 discs ( same master cyl.) ??

[MCRider]

So was my first hypothesis correct, before I was sold otherwise ?.... even with 2 x times the lever travel it's no advantage having 2 discs ( same master cyl.) ??

That's my understanding and belief. Personal experience confirms, but I'm not an engineer. However I would require a fairly convincing presentation to move me otherwise.  Something with third party support.

[scottly]

Bottom line you do not double braking force by adding a disc to an otherwise unchanged system.

Sorry, you are wrong. I know from first-hand experience. My advice to anyone that wants to improve the brakes on their CB is to add a disc and caliper. It can be done with stock parts, although there are variations between models and years.

[Spanner 1]

I can see it both ways,...... MC is correct that pushing the same volume of fluid into 2 brake cyls. would 1/2 the pressure on each disc = no advantage, but the pressure the master cylinder CAN produce may be many more times what it is asked with a single disc set-up... i.e.  pull the lever as hard as you can will only produce so much pressure on the  single disc, with 2 discs the same pressure may well be obtainable..... seewhatimean?