How Much Better are Dual Front Discs vs. Single?

For me the biggest benefit is heat dissipation. When racing or really pushing on the road a single disk tended to have a element of brake fade when slowing quickly from high speed. The feel of dual disks also encourages you to brake harder when racing as the front of the bike is more stable. As stated though to get full benefit some shock mods are essential.

I have to stick up for the single disc. I've ridden both and IMO my larger single disc stops as hard as the smaller duals. Just my .02

I have never noticed a difference.

Thanks to all for the excellent replies and opinions. The Gringo is right about my right side fork not having a mounting for the caliper. That is why it will be quite a major task to do this conversion for me, and why I am weighing out the pros and cons.

A co-worker of mine was involved in an accident a few weeks ago, whereby a car ran a red light. He was "almost but not quite" able to stop his motorcycle before hitting the rear quarter panel of the car. A week after this, a car who didn't see me, shot all the way across the lanes in front of me. I was able to slow enough, but had that "Holy Crap" feeling at how hard I had to squeeze the brake lever to do the stop. This got me to thinking about the dual disc issue again.

One other question. Scroll up to the photo of "Bluemeanie's" front wheel. His caliper has, I think, a round brake pad that covers the entire disc. Mine has rectangular pads that do not cover the inside holes on the disc. I have wondered which might be more effective. Both probably have the same surface area, but the rectangular is further outboard on the disc. Any opinions?

Bluemeanie wrote: "IMO my larger single disc stops as hard as the smaller duals. "

Smaller in what way? Ed

Jeff.Saunders wrote:

You are adding considerable unsprung weight to the front - well over 10lbs of weight depending on the disk rotors and calipers used.

This can result in much more shock coming up to the bars - changing out fork springs or going with slightly heavier weight fork oil can help.

On a bike like the Z1, I don't like double disks - I've run them, and removed them - just too much weight. Yes, you do get slightly more braking force, but you are still at the mercy of the tire...

The Z1, KZ900 and 77 KZ1000A used 7mm thick rotors. This progressed to drilled rotors, then 4.5mm drilled rotors on late 70's KZ's with double disks.

Have enjoyed long term experience with 1973 Z1 with 14mm m/c pushing single front disc (having in 1973 moved up from CB750 Honda to Z1).
Also have enjoyed long term experience with 1976 KZ900-B1 LTD with 5/8" m/c pushing dual front discs (purchased new in 1976 when first introduced).
Both systems are well maintained and now in perfect as new condition.

Perceive little if any difference in real world stopping power under normal spirited riding conditions.
Emergency stopping is about equal -- and at mercy of front tire grip.
No "pullin" to either side during hard braking with either bike.
No excessive "diving" during hard braking with either bike.
Both bikes will "howl" the front tire under extreme braking.

This thread began with the premise that reducing the force required on the front brake lever for stopping from a given speed is a "benefit" of converting from single to dual front discs and asked about any other benefits. Imo this a false premise, and it may well be counter-productive and actually dangerous if retaining the same m/c used with the single disc.

The smaller 14mm m/c is designed with optimal fluid pressure range from light braking to hard emergency braking with single front disc.
The larger 5/8" m/c is designed with optimal fluid pressure range from light braking to hard emergency braking with dual front discs.

Imo it's undesireable and dangerous for a front braking system to be so powerful that it may result in unintentional front wheel lock-up in a panic braking situation where you're instinctively squeezing the brake lever for all its worth. And this is what reportedly happens when the smaller 14mm m/c is used to push dual front discs. The front wheel locks with resulting loss of control and bike tip-over.

Imo it is courting disaster to continue using the smaller 14mm m/c when converting from single to dual front discs. Akin to "power brakes" being too powerful.

MaKaw had good reason to discontinue the smaller 14mm m/c used with single front disc and begin using the larger 5/8" m/c with dual front discs. The objective was a balanced system. The smaller 14mm m/c exerts more pressure into the brake line for any given amount of lever squeeze, is designed to push a single caliper on a single disc, and is capable of providing too much maximum power when used with dual front discs.

I believe this is the reason Kawasaki's factory accessory dual disc kit also included a larger 5/8" m/c along with the additional caliper, lines, and related fittings.

Some folks have run 14mm m/c with dual front discs, and so far with no problems. Good for them, and may their good fortune continue. Meanwhile, ask the others who have lost control and wrecked their bikes when the front wheel unexpectedly locked up in an emergency braking situation, due to using 14mm m/c to push dual front discs.

I would agree that in a road racing environment, an advantage of dual front discs would be slower to heat up and suffer diminished braking ability. At the expense of increased unsprung weight.

Then again, maybe I'm all wet 'cause it sometimes gets to raining pretty hard up here in the peanut gallery. :laugh:

Good Luck!

My thoughts are you'd be better off to upgrade your brakes to something newer that has more power. Duals are nice, but compared to newer braking systems they don't compare.

However, maybe you can find a newer MC that puts out more fluid to provide a little more squeeze on the rotors. Also, braided hoses will improve them, good pads, and a clean non-glazed rotor. Thats if you want to get full performance.

If having only one fork with caliper mounts is an issue why not use a late 90's tokico 2-piston caliper with a machined adaptor. I have used these in various applications and work great. Plus they are floating calipers which means they center themselves around the rotor.

What do those come on stock?

I imagine the dual disks are more important if your ride with more weight on the bike. If going 2 up most of the time or in my case towing a hack a twin disk might make a difference. More weight shifting means more friction before lockup. Also if it takes less force to lock the front brake it would make it easier to manipulate brake pressure in a stop as you might be better able to get a feel of whats happening instead of just jamming on it with all you got..

Then again, I could be wrong.

WABBMW wrote:

Thanks to all for the excellent replies and opinions. The Gringo is right about my right side fork not having a mounting for the caliper. That is why it will be quite a major task to do this conversion for me, and why I am weighing out the pros and cons....

Bill, the forks shouldn't be a problem. The 750-Ltd-4s have the same triple tree, so I'd wager that the caliper & disk will line up (this is assuming you did the easy thing & got a 750 dual disk wheel - I have no idea if your alloy wheel will work).

I've got a couple of sets of 750 forks & 750 dual disk caliper handy if you'd like to do a test fit.

OK, I do understand that if you want to keep you bike as stock as possible then you might want to stay with one disc. Dual disc is more efficient and adding 2 or 4 -piston calibers makes braking even more effective.

I do not understand any argumentation that " too powerfull brakes cause accidebntal dips":huh: Come on now, I´d rather dip it that fly through a windscreen!

Do modern sportbikes just dip over when ever they brake? The idea is that you should practise and learn how to make a panic-stop. How many of you have even tried practising it? Braking till rear wheel is in the air? That is how much braking power can be used in order to stop. It´s called "endo" in stunting....

And this is why I got dual-disc 6-piston Tokicos from a Busa in front and a opposed (2)-piston rear caliber from a ZRX1100. I´ve ridden my ELR with stock brakes, then with ZRX750 brakes and this current set-up. I´m not going back, I just love that 2-finger-braking power:P