How Much Better are Dual Front Discs vs. Single?

I see numerous posts about "How To" convert from Single front disc brakes to Dual, but very little about how much improvement can be expected. I presume that it reduces the force required on the front brake lever for stopping from a given speed, but are there other benefits?

I hesitate to go to all the trouble and expense, plus adding the weight of another disc and caliper unless the results are significant. I know that Dual discs on a KZ will not stop like a modern sport bike, but how much difference will it make?

Thanks for the input.

The only real benefit is that under severe riding, the brakes will "stay in" a lot longer and not fade out from heat saturation. I think for racing it's a real benefit, for street riding the single disc on mine whill brake so hard it will put your face through the windshield. The maximum stopping force is limited by the front tire's traction, not the brakes friction.

Not to sound stupid, but it is literally twice as good. The major effect is that you are putting torque on both forks equally, reducing any twisting forces. When I get off of mi GPz1100 and get on my KZ900, it feels like my breaks are failing. What you will have to get used to is the extra dive.

Had the single front disc brake on my Z1 for years and thought the brakes were fine. Had to squeeze harder then I wanted too but they stopped me in good fashion. Bought me a 1980 LTD with dual disc front brakes. Every time I would use the brakes, I kept hearing a squealing sound. Inspected the brakes and couldn't find anything. This went on for a few days and then one day after using the front brakes and hearing the squeal, I happened to look back. All this time, the dual brakes weren't squealing...the brakes were so good I was actually sliding the front tire and leaving black marks. Big difference in performance...and this was from stock brakes. Can't imagine what it would be like on a new bike, but those dual brakes made a believer out of me. Worthy improvement in my book in most circumstances. Maybe not on a dragbike on where weight might be an issue but otherwise, dual brakes are GREAT!!!

These old single piston brakes aren't that good to begin with so 2 will be better than one. Try to find a 79-80 master cylinder. It has a larger bore and will provide better pressure.

but how much difference will it make?

Thanks for the input.[/quote]

A Lot!!

You wouldn't believe it.

All the diffrence in the world. Roy:ohmy:

One modification I would do in conjunction with adding the second disc, is to install air caps and put a little pressure in the forks. This will reduce the dive and will make the brakes even more affective.

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.

Bill I may be wrong on this because my 650 CSR is an 81 and yours is an 82 but I don't think you have the needed mounts on the lower fork tube for a second caliper on your bike.

racer54 wrote:

Had the single front disc brake on my Z1 for years and thought the brakes were fine. Had to squeeze harder then I wanted too but they stopped me in good fashion. Bought me a 1980 LTD with dual disc front brakes. Every time I would use the brakes, I kept hearing a squealing sound. /// one day after using the front brakes and hearing the squeal, I happened to look back. All this time, the dual brakes weren't squealing...the brakes were so good I was actually sliding the front tire and leaving black marks.

That's the point I was making: the single disc can stop the wheel dead and so the maximum braking is limited by the traction of the front tire. How is it any different if two discs are locking the wheel or one?

It may be true that duals would give a specific amount of stopping action for less pressure applied to the brake lever. But, if I can lock the wheel with a medium pull, why would I care at what pressure my normal braking action is?

Dual front disks do result in additional unsprung weight, but they apply braking forces evenly to both fork legs and require less lever pressure because you have double the energy transfer/heat dissipation for a given level of pressure. With a really sticky front tire that doesn't skid on dry pavement I believe the dual disks make hard braking considerably easier. With the Michelins of old, I couldn't make the front tire skid on dry roads even though I could easily brake hard enough that I had to be careful not to end up sitting on the tank. I don't know if the single disk setup could apply that kind of braking force, but if so it would certainly require an iron grip. Unfortunately, the current Michelin Macadams don't stick as well as the old A-48's, so I am forced to remember not to apply too much pressure or the front tire will skid a little. I guess either setup will work, it's a matter of how much or little lever pressure you’re comfortable with. Ed

I have been riding dual disk for a long time. One or two fingers on the brake lever is all that is needed. I hardly used rear brakes.

The bike i got now i use four fingers and the rear brakes and it is a lot of effort to get the thing stopped. Roy