Topic: Dual/more powerful brakes

[matt]

Hi, I'm new to the forum and cafe racers in general so thanks in advance for any help. I have a 82 cb650 that I'm working on and I'm wondering what my options would be for running dual front discs and hopefully staying with spoke style wheels?

Sent from my C6906 using Tapatalk

[MiGhost]

Watching along as I have interest in this also.
Would the early GL1000 hub work?

[dave500]

you had the single disc fade yet?

[iron_worker]

Dave is too practical for his own good. lol

IW

[MiGhost]

you had the single disc fade yet?

No, but i have had a 30K lbs truck loose the brakes @ 65mph. Exiting the highway on a downhill ramp with a traffic light at the bottom, and a car sitting at it.

Thankfully the light turned green, and I missed the car.  No! It was not fun!!

Brake fade is nothing to take lightly. I am well aware of the fact that the single disc is well capable of locking the wheel. But a sliding wheel in not a controlled stopping wheel.
Ever had a moron pull out in front of you?
Do we need to guess what happens next?

Besides that. I have added considerable extra weight in the form of fairing, and full rear luggage package.
Not to mention. That I prefer the balanced look of the dual disc.
At 70-80 mph. The piece of mind is worth the effort!

[iron_worker]

The GL1000 front end is a fairly popular conversion for the 750s but I'm not too sure if the 650 shares the same steering neck design.

IW

[andrewk]

you had the single disc fade yet?

No, but i have had a 30K lbs truck loose the brakes @ 65mph. Exiting the highway on a downhill ramp with a traffic light at the bottom, and a car sitting at it.

Thankfully the light turned green, and I missed the car.  No! It was not fun!!

Brake fade is nothing to take lightly. I am well aware of the fact that the single disc is well capable of locking the wheel. But a sliding wheel in not a controlled stopping wheel.
Ever had a moron pull out in front of you?
Do we need to guess what happens next?

Besides that. I have added considerable extra weight in the form of fairing, and full rear luggage package.
Not to mention. That I prefer the balanced look of the dual disc.
At 70-80 mph. The piece of mind is worth the effort!

I ride my F2 (triple discs, comstars) everywhere.  Full fairing always, bags when I take a trip.  At 80mph, if you grab a handful of brake in an "oh sh*t" moment. you start to discover the limits of 35mm fork tubes, especially when you're two-up.  Flexy, and not real confidence inspiring when you're trying to bring things to a stop in one of those situations you're presenting.

Point being here- evaluate the benefits/performance gains of piecing together a twin disc setup using stock components and a quality fork brace versus a modern front end swap.  If braking control is your goal, messing with the stock stuff is not much cheaper than a USD fork swap.

[dave500]

or ride accordingly?

[trueblue]

FWIW, the Aussie and European model CB650Z had twin front brakes from the factory, but it also had comstar wheels

[Wobbly]

or ride accordingly?

The brakes on the old Hondas are atrocious. I guess, if you have nothing to compare them too...
After 37 years, I had decided to go for he dual-disc setup on my K7. Together with the steel lines, it is a mild improvement. Compared to the Brembos on my RR, the dual EBCs are still a joke. No, the Honda does not go 190mph, but even at 30mph (riding accordingly), its brake performance is very weak in comparison. For as long as I recall, putting a dual-disc on the CB750 was something commonly done--for a good reason.

[dave500]

the brakes on new bikes are too good?dont drill your disc run a hacksaw slot through the pads.

[eastyork1977]

Dual disc set up does feel quite a bit better than the single disc. But hard for me to compare my 750F braking power to a 500K both with steel lines.

After going from rubber to a single steel line on the 550, braking improved dramatically. I do like the lever nice and tight so I bleed my brakes regularly.

Drilling the discs will give you more friction but the holes really function to wisk water away from the surface in wet conditions.

Single steel line by-passing the stock pressure switch should give you good stopping power with one disc. I often take my 550 on the highway and have no issues now with the brakes. I weigh about 86 kgs so that could factor in.

If you're still having issues with a drilled dual disc setup with steel lines, I would check your pads and renew. I would make sure to bleed and check brake pad gap clearances. Vacuum pump also comes in handy here.

[andrewk]

or ride accordingly?

That's the easiest and cheapest option, but isn't a bit silly to pretend like the machine can't be improved, or that it's entirely needless?  You can ride anywhere safely on the stock kit, but suspension, braking and tire technology has come a long way- We ought to be taking advantage of that.  You don't have to live with a sintered pad squeeling on a 6mm thick stainless rotor that fades in the rain and has rotten modulation.

I'll say for the record though, that era 650 has much better brakes than the earlier bikes.  Looks like it has the twin pot caliper, those are good feeling brakes, and you can get decent pads for them.

[andrewk]

Dual disc set up does feel quite a bit better than the single disc. But hard for me to compare my 750F braking power to a 500K both with steel lines.

After going from rubber to a single steel line on the 550, braking improved dramatically. I do like the lever nice and tight so I bleed my brakes regularly.

Drilling the discs will give you more friction but the holes really function to wisk water away from the surface in wet conditions.

Single steel line by-passing the stock pressure switch should give you good stopping power with one disc. I often take my 550 on the highway and have no issues now with the brakes. I weigh about 86 kgs so that could factor in.

If you're still having issues with a drilled dual disc setup with steel lines, I would check your pads and renew. I would make sure to bleed and check brake pad gap clearances. Vacuum pump also comes in handy here.

Stainless/braided lines are the best thing you can do to the stock brakes, IMO.

[eastyork1977]

Couldn't agree more. Both my 550s and 750F have steel braided lines on them now in black so they look stock. One 550 has one line, the other has two using the original pressure switch.

I've got a 400F with rubber lines that works fine, but to compare it to the 550 brake? Night and day, especially since I weigh almost 200 pounds. haha.

[Wobbly]

If you're still having issues with a drilled dual disc setup with steel lines, I would check your pads and renew

I have all of this, drilled EBC rotors, new Honda pads and calibers, steel lines, new cylinder for dual disc setup. However, the front brake of my kid's moped (Honda MBX 50) seems better. The CB 750 was the first motorcycle in mass production with a disc brake--and that is awesome. It was also the first mass-produced four-cylinder engine. The four cylinder did not only pass the test of time but is the most common standard now. However, the floating caliber simply was not a good idea and has been replaced with a fixed one for a good reason.

the brakes on new bikes are too good

The modern brakes and ABS are an awesome improvement. It's the one thing, I really wish I would have on m CB. After all these years and lots of mileage, I am still standing. So, it can be done. But, especially now that I am older and slower, I would like to have better brakes. Thus the dual-disc conversion.

[DH]

Dual disc set up does feel quite a bit better than the single disc. But hard for me to compare my 750F braking power to a 500K both with steel lines.

After going from rubber to a single steel line on the 550, braking improved dramatically. I do like the lever nice and tight so I bleed my brakes regularly.

Drilling the discs will give you more friction but the holes really function to wisk water away from the surface in wet conditions.

Single steel line by-passing the stock pressure switch should give you good stopping power with one disc. I often take my 550 on the highway and have no issues now with the brakes. I weigh about 86 kgs so that could factor in.

If you're still having issues with a drilled dual disc setup with steel lines, I would check your pads and renew. I would make sure to bleed and check brake pad gap clearances. Vacuum pump also comes in handy here.

Another thing about drilling is that it lightens the rotor. It also, provides an escape route (thru the holes) for the gasses that build up between the pads and the rotor during braking, so fade is less of a problem.
I've never done to bike pads before, but the hacksaw groove in the pads probably has a similar effect, to a degree, of eliminating the gas build up. A lot of automotive pads have this cut manufactured into them when new for this same purpose.
Heat goes down, and resistance to fade is better.

[TwoTired]

If you can lock the front wheel with a single disk brake, what does dual disk give you other than a touchier brake lever that makes it easier to lock the front wheel in a panic stop?  In my experience, locking the front wheel puts you down sliding without much directional control.  I'd rather be able to steer all the way to object impact, or make the choice to lay it down without the machine doing it it for me.

I can certainly support the SS lines improvement though, just from the lever feel aspect.  But, then I'm comparing fatigued rubber lines to the SS type.

Still, if you want new bike performance, buy a new bike and forget all the "old" technology and the riding style of the era, imo.

[andrewk]

If you can lock the front wheel with a single disk brake, what does dual disk give you other than a touchier brake lever that makes it easier to lock the front wheel in a panic stop?  In my experience, locking the front wheel puts you down sliding without much directional control.  I'd rather be able to steer all the way to object impact, or make the choice to lay it down without the machine doing it it for me.

I can certainly support the SS lines improvement though, just from the lever feel aspect.  But, then I'm comparing fatigued rubber lines to the SS type.

Still, if you want new bike performance, buy a new bike and forget all the "old" technology and the riding style of the era, imo.

One of these SOHC bikes with good brakes is a helluva nice package though.

If you just double up the stock caliper and rotor, I agree. But if you're using a modern (single or dual) brake, then you have more control of your situation because the brake actually modulates.

[trueblue]

If you can lock the front wheel with a single disk brake, what does dual disk give you other than a touchier brake lever that makes it easier to lock the front wheel in a panic stop?  In my experience, locking the front wheel puts you down sliding without much directional control.  I'd rather be able to steer all the way to object impact, or make the choice to lay it down without the machine doing it it for me.

I can certainly support the SS lines improvement though, just from the lever feel aspect.  But, then I'm comparing fatigued rubber lines to the SS type.

Still, if you want new bike performance, buy a new bike and forget all the "old" technology and the riding style of the era, imo.

A well set up dual disc is far better than a single.  It is a simple matter of leverage, you don't need to squeeze the lever as hard to get the same stopping power.  Twin disc gives you double the leverage on the wheel so it takes half the effort to stop.  Because you aren't squeezing the lever as hard to produce the same stopping power you are less likely to lock the front wheel.

It is like trying to undo a tight bolt.  You may be able to do it with a 6" spanner, but when it does come loose your hand with fly off and you will crack your knuckles, where as if you use a 12" spanner you will be able to use less effort and achieve the same result without the busted knuckles because when you hit the breaking point you aren't forcing it and you can control much easier.

Same principal works for the brakes on your bike, one brake works but in a sudden stop situation you are squeezing the lever that hard that you can't precisely control the pressure on the lever.  My 650 has twin rotors and under most situations 2 fingers on the lever is more than enough to stop it in a hurry, I have even in an emergency stop had the rear wheel off the ground a few inches simply because I could control the braking on the front end with minimal effort.  I am certain that if I only had a single disc I would have been into the side of the ute that pulled out on me that day.

[Proto]

I am kind of in TwoTired's camp on this one.  From my accident investigator schools back in the day, the maximum/optimum braking point is one just shy of where the tire locks and starts skidding.  The skid is actually creating small pieces of rubber "bearings" that get between the tire and surface of road, thus decreasing the coefficient of friction which increases stopping distance.  So if your brake system can get you easily to the point of locking the wheel, you have more than enough brake for the job.

An ideal brake system is the ABS system which attempts to keep you at that point as the max.  If you are putting an ABS system on your bike, I can agree that would be an improvement.  I did notice a better braking feel when I got my first bike with a front disc after riding drum braked bikes.  However, subsequent bikes with dual front discs just didn't feel that much better.  My "other" bike right now is a Harley Ultra Classic with the dual front discs and really can't say that it is any better than my old F1 at stopping.

On my recent 2700 + mile 2014 relay ride, I had occasion to "panic brake"  three times, where I momentarily locked both front and rear brakes.  Twice I had oncoming cars veer into my lane to pass a slower car with total disregard to me or the traffic behind me.  We all ended up on the shoulder to avoid colliding with those idiots.  This happened in northern AZ and northern TX.   The third occasion was in north Denver, early Sunday morning with light to medium traffic.  Right hand lane traffic was suddenly tooling along at about 1mph!!  Turns out a car was broke down and the poor guy was pushing it along in the travel lane as there was no shoulder to pull off on due to construction.  As traffic stacked up behind him, the rear most cars were idling along with their foot off the brake waiting for a chance to pass.  Kind of a surprise to run up onto a car at 70mph that was virtually stopped in your lane!! 

At any rate, my old '76 F1 with single front and rear disc was fully capable of stopping/slowing me in time.  This bike wears a Vetter faring with lowers that had gear stowed in the compartments.  It also wears large, hard saddlebags that were jammed with gear.  It was topped off with a big duffle bag.  Add to this my 240lbs and this bike is heavy!  Sure, I have to pull the front brake lever a little bit harder than when running light, but I think we are only talking about ounces here.  It is not noticeable at all when your life is passing before your eyes in an emergency situation!

I think the arguements for the dual disc set up are valid for a racing situation with the hard, excessive braking, as are drilling the discs.  I doubt that one can (legally) regularly get into a situation where the two front discs would really benefit these old bikes in 99.9% of our riding.  If you are doing it to make your bike look like a racer, go for it.  If you drive your bike like it is a racer (like one of my buddies does!  He has ABS though, new Honda) go for it.  I just don't think there is a vast advantage to duals on our bikes. 

Of course I may be totally wrong with my thinking.........

[Wobbly]

Of course I may be totally wrong with my thinking.........

After 37 years, I switched to the dual disc brake setup. It is an improvement every time I use the brake in daily driving. Performance is still poor in comparison to a modern bike, but it is an improvement nevertheless. The problem with the CB 750 is not so much that it has only one disc, but the floating-caliber technology--which is total crap.

[dave500]

handier on long steep decents,more braking reserve.

[bjbuchanan]

One suggestion that would take a little fine tuning, a different master cylinder so that you can 'possibly' modulate the existing brake system easier. With my stainless lines my lever is STIFF. I stop in panic stops just fine but I always think about a different sized MC that would allow me to modulate easier to the threshold.

Some of the modern bikes have that advantage that is overlooked. Everybody talks about two finger braking, but you can have the best brakes for the situation and an incorrectly sized master cylinder and crash every time as a result. It is a system

[Retro Rocket]

Ever had a moron pull out in front of you?

Silliest question of the week....