Topic: Dual Disc Brakes??

[SOHCiro]

So I'm thinking about going dual front disc set up and came across interesting thoughts... It's for a 76' 750 Super Sport.
Right now I have a stock caliper with a drilled disc and I've got an extra NON-drilled disc.

I was wondering if it would affect the performance in a negative way in these conditions:

1)Have a drilled disc on one side and non-drilled on the other (weight difference and different cooling rate) both with exact same stock calipers.
2)Put a different, perhaps a dual piston caliper on one side (Different stopping power on each side)

I'm no mechanical engineer, but I can imagine the force acting weirdly on the wheel, and have one side wearing pads quicker
I realize that people usually have matching rotor/caliper on both sides, which must have some reasons, but just had to ask!
What are your thoughts??

[kaptainkid1]

I would always put matching rotors and matching calipers on the front discs considering that the majority of your braking will be the front tire.  Additionally putting odd set up with different calipers would create different wear patterns. I'm sure it could work but why do a half ass job and risk possible injury to yourself or your bike.

[ekpent]

 Plus it would look goofy 

[Bodi]

No problem with braking - the stock system manages with all the work on one side - but it would look strange.

[slikwilli420]

Why not drill the second one or have it done? It will look half assed and anyone would look at it and wonder what else you skimped on. Some people dont mind hack jobs but it reflects poorly on the owner, so why not ride something you can be proud of?

[M.Henry]

How bad of a job would it be to just use a drill press with the drilled disc as a template to drill the holes in the other disc then come back and deburr anyways? Just a thought.

[MauiK3]

DIY drilling can be done. It's pretty tough to get it right, stainless steel is notoriously difficult to drill. Send both discs to TruDisk for a light surfacing and drilling, they will match and work great.

 https://truedisk.net/

Change the brake lines to stainless braided lines for more positive feel. They come from Slingshot.

[PeWe]

Or use 2 not drilled

[michaelb_650]

If the desired effect is maximum stopping power, then both disks should be the same material, size, shape, etc, and the pads should all be the same.  If one grips before the other, you lose stopping efficiency, effectively braking on one rotor.  When they are all well-matched, you get better stopping.  If the desired effect is appearance, then do what makes you happy.  Anybody, and i mean ANYbody that looks at your ride and points out "one drilled, one not drilled" deserves whatever they get next whether they see it coming or not. 

[Bodi]

No. Two disks on one wheel will never both have exactly the same stopping power. Total stopping power will always be the sum of the two disks' work.
There will be a difference between an undrilled and a drilled disk, depending on conditions. I don't know which might be better in dry but probably the solid one, in wet the drilled one will shed surface water first and drag more for a while. It really does not matter for braking, the stopping power will be the two working together: one having more power does not reduce the other's.
Two disks will always stop better than one, especially in hard use because the two disks will dump the heat energy (this is from the total work done slowing down) twice as fast as one does so heat fade will be considerably reduced.
Make sure you get a master cylinder sized for dual disks, the single disk one will probably go to the bar before maximum braking is reached because the MC has to pump twice the fluid volume it was designed for.

[M.Henry]

Yes it is essentially a super position of the two rotors braking power. Both rotors are independent systems applying braking torques (Moments is the engineering term, I'll continue using "torque" since that is the more commonly familiar term) to the hub, the braking that you feel is just the sum of the torques (moment balances) of the brake systems, the tires roll resistance, as well as momentum of the bike. By adding a second rotor you are just increasing the braking torque in that balance of radial balance of torques.

what this comes down to is that adding a second rotor that is mis-matched doesn't really do anything but add more braking force.

(technically there are minute gyroscopic forces that are different but they are minuscule and ignoble)

[SOHCiro]

Thanks for the input! Bodi and M.Henry's ideas made a lot of sense to me, especially in terms of the physics and engineering POV.
But again like all of you said it would look so odd
Anyways I feel much safer now going down that route, and will probably have matching drilled rotors eventually.

Another thing I wondered, if one is drilled and the other isn't, that means the wheel has unbalanced weight.
Maybe that'd affect handling a tiny bit?

[754]

Not as unbalanced  as a single disc..
 I ran duals with stock master cyl, -3 lines... nice 2 finger braking?

[M.Henry]

The only legitimate down side is increased rotational mass leading to more rotational momentum in the wheel system, but there is so much excessive momentum happening on these bikes in transnational and rotational orientations that it doesn't matter. The only time I would be concerned about that with these bikes might be on a very very serious race bike where an ultra light wheel rotating assembly would mean better accel and decel of the RPM of said rotational systems.

I.e. there is downsides that a race car engineer might be considered with, but not us enthusiasts.

[MRieck]

DIY drilling can be done. It's pretty tough to get it right, stainless steel is notoriously difficult to drill. Send both discs to TruDisk for a light surfacing and drilling, they will match and work great.

 https://truedisk.net/

Change the brake lines to stainless braided lines for more positive feel. They come from Slingshot.

Thanks for the website.

[setdog]

Dual disc front sounds great, and I hope to install a setup like this on my next build as I have dd front wheel ready to go.

While scoping out a good setup I thought about how to solve the problem of keeping my rear brake light activation.

Since The three way would be used up by with by an extra caliper hose, I intend to buy an aftermarket master cylinder with a 2 prong brake switch buolt in and then  splice the wires that would normally go to the brake light switch on the three way, to the new master

Hope it works

[Bodi]

You can use a new master with switch or get a "switch banjo" with a hydraulic switch in it. Both work well.

[Don R]

 I did a 76F. I drilled both rotors and used the stock M/C. It worked great. I even cut up two rotor fenders and made one for the right side. Drilling one isn't so bad, the coolant/lube is very important and I did two rotors with one bit. I bolted them back to back to transfer the pattern.

 All that said, the 83 gl1100 brakes one front rotor with the handlebar master cyl.  and the foot operated one is split between the other front and the rear brake.
 Don't make it look wonky, wait until you can do it right.

[MauiK3]

You won't lose the brake switch if you use a double banjo for the brake lines.