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How Much Better are Dual Front Discs vs. Single?
- Lukes6
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- Bluemeanie
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1980 KZ650F1, Bought new out the door for $2,162.98!
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- donthekawguy
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Rathdrum Idaho
1971 Kawasaki g3ss
1972 Yamaha R5 350
1965 Suzuki Hillbilly
1964 Yamaha 125
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- WABBMW
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- Let The Good Times Roll !
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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?
Bill Baker
Houston, Texas
1982 KZ650 CSR
2008 Yamaha FZ1
2006 Yamaha FZ1
1977 Honda Supersport 750 four (sold)
1984 Honda Nighthawk 650 (sold)
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- 650ed
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Smaller in what way? Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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- Patton
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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!
1973 Z1
KZ900 LTD
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- KawiConvert
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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.
1978 KZ650 D1 ~ Carb jetting: 107.5 & 20 & 4th groove with pods and 4-1 Exhaust
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- wompy5000
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jpriderdesigns.blogspot.com
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- tachrev
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- Rubber Side Goes Down
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1977 Kawasaki KZ1000 : Street/Strip
Build Thread
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- The Garbone
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- User is Currently waiting for his bailout check..
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Then again, I could be wrong.
2007 Royal Enfield Iron
1979 KZ650 & Hack
1949 Ford 8n
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- JMKZHI
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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).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....
I've got a couple of sets of 750 forks & 750 dual disk caliper handy if you'd like to do a test fit.
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- Z1109R Fin
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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
Z1000R ´83...Slightly modified...
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