So here is the question:

The basis of minimum stopping distance is dictated by maximum adhesion of the tires against a given road surface. Applying maximum brake to the point of juuuuuuuuuuuusssst prior to locking them up will produce maximum braking/minimum stopping distance.

With that said, I would imagine a single disc can do the same thing as dual discs. It just requires more pressure on the brake lever. Am I wrong?

Comments and opinions please.

 

I would say yes under the provision that the single disc is able to get the tire to lock up and you are able to maintain said pressure which is easy with the pizza cutter on mine

I am looking at converting to dual disc because I am tired of applying said pressure and I want togo with a fatter tire so I have a larger contact patch to be able to stop faster with less effort

 

Have dual disks on my Fat Bob. There's more braking power and that allows better control. It's much easier to get to the point juuuuuuust before locking it up because there's more control, and it doesn't take any effort that could affect handling.

 

I would think if I had a limited amount of money to spend the fatter tire with greater contact area to the road would the the better way to spend it. The Fat Bob must have the best of both worlds. Add in the wider forks and it is a home run.

 

Yes, your description is correct. However, a few other factors come into play.


Surface area of pad to disc. Dual discs double the surface area and allow less pressure to do the same job, and/or, they provide more grip in hard stopping circumstances. But, as you said, the tire grip is still the weak link.

Heat dissipation. As we know, brakes get hot. Heat reduces the friction at the contact surface. Continued use in aggressive riding or curvy downhill riding will create heat that reduces the stopping power. The more surface area you have, the less heat is created, and it dissipates faster as a result. Brake fluid gets hot too. This reduces its ability to compress and it weakens stopping power.

Dual brakes don't add a lot of advantage until you get into the aggressive mode so long as you are willing to grab harder. They serve a much greater purpose on a race application where heat severely affects stopping power. One could push a Dyna to these extremes and could use the advantages.

Another couple methods of achieving more surface area are:
Larger surface-area pads. These usually coincide with a larger caliper that has more actuated pistons.
Larger diameter discs. These usually go with larger calipers too.

Dual discs are cool, and I'd like to have them, but a less expensive mod would be to add a larger disc/caliper arrangement. Arlen Ness has a new one for single disc Dyna's. I'll probably go that route at some point.

 

Bingo!
I've had my dual 11 1/2" disc's fading bad before where I had to pull very hard to slow for the next corner during a quick run on a winding road. I was surprised how quickly they started to fade with the all out fast as I could go riding.
A single disc would have been worse.

 

The difference is that if you brake until before lock-up (as obviously you usually do), two disks are dissipating twice the heat (i.e. converting inertial energy) as one disk. So you stop quicker.

I have ridden Harleys with a similar weight and with one and two disks. The Softail Slim scared the crap out of me as I found myself unable to stop at lights compared to the much better braking on the Fat Bob.

 

In summary, a dual disk brake setup alone is not going to stop you faster than a single with all other things being equal(same bike, same tire, etc.)...you can still lock up a single disk, BUT a dual disk setup will do it with much less effort and input, and will not fade as quick because each caliper/rotor is sharing the effort with the other one.
on a dual disk setup, each caliper/rotor is doing 50% of the work to accomplish the same thing, whereas one single disk would be doing 100% of the work.

On the down side, it adds unsprung weight to the front wheel.

Having said that, a dual disk setup on a Dyna will require less input from the rider and provide better feedback & control. In this case, 2 is better than 1.

 

To be honest I downshift more than I brake. If I have to do heavy braking all the time, I am not a good rider. For panic stop and quick slow down, 2 discs beat 1 disc for sure. I never had poor braking except riding 2ups, I have ridden Roadking 2up, braking is awesome!

 

its all about what your riding for. you can ride the twisties for the scenery or you can ride them for the road. if your riding for scenery you shouldnt really need to brake hard. if your riding for the road and not braking hard your doing it wrong.