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Old 16-Mar-2005, 10:24 AM
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Brake Master Cylinder

Thought I may as well make the most of the single disc by fitting a radial master cylinder. Can anyone recomend one. I looked at the Brembo then was asked about bore and stroke but could not give and informed answer. So what do they mean for the rider in terms of breaking power and feel and what should I be looking for to go on the 600ss. Hopefully I can have the parts ready to bolt on when (if ever) I get home. Thanks.

Mike
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Old 16-Mar-2005, 10:55 AM
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I thought about going for the 18mm diameter Radial Brembo but could not justify the cost. A 748/916996 remote reservoir 16mm Mastercylinder should be more than enough for a single disc front end. The replacement levers for the 916 M/cyl can be had for 1/5 of the brice of the Brembo Radial ones. Failing hat Nissin do m/cyls on production bikes with 3/4 inch bore (just over 18m) which again are a cheap option with cheap spare levers available
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Old 16-Mar-2005, 11:31 AM
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For a single disc I believe you need a 16 mm bore m/c from Brembo. It should be the same as the use on Supermotards. There are plenty of other choices if you feel like experimenting, although the costs are very similar. Other makes include PVM, Magura, Dissicati, etc.
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Old 16-Mar-2005, 06:26 PM
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Let me answer the part about braking power first. Changing your stock master cylinder to an aftermarket radial design will NOT give you more braking power to help you stop sooner.

A radial master cylinder with a different piston diameter and/or lever fulcrum-to-piston distance will only change the feel of the brakes at the lever. So keep in mind that Ducati chose a master cylinder size to give you the best modulation characteristics (feel, sensitivity and control) for your bike.

Good modulation means good feedback to the rider during a stop. A good braking system needs to establish the closest linear relationship possible between the force applied to the brake lever and the actual deceleration of the bike. Stopping power is technically easy to achieve, but achieving it along with good proportional braking response is more difficult. This, I feel, is the major factor influencing braking quality.

Thatís not to say that the Ducati engineering departmentís choice is best for all riders or riding conditions. The best choice for the track isnít the best choice for the street.

Different riders have different preferences and weíre all adaptable. A rider is able to compensate for one performance drawback to gain an advantage with another. But again, it's situational dependent; a braking system that gives repeated stops from 150mph with the force application of one finger is not necessarily optimum for a 40mph panic stop in traffic. Even though a rider is adaptive to a braking system's general behavior doesn't mean that in an emergency that he'll use a light one-finger pull to stop.

So letís move on to your choices.

First, thereís a different master cylinder size requirement for single rotor systems than for dual rotor systems. A dual rotor set-up has a lot more caliper pistons to move so a larger volume of hydraulic fluid has to be moved by the master cylinder piston.

Also, since different Ducati models have different size calipers and rotors you canít always translate a recommended master cylinder size to another setup.

A master cylinder size designation is written AAxBB where AA is the diameter of the piston in mm, BB is the fulcrum-to-piston distance in mm.

The master cylinder piston diameter is chosen based on the number and size of the caliper pistons.

A fulcrum-to-piston distance affects two things: the amount of force needed at the lever, and the distance that the lever needs to be pulled through (to displace and compress the same amount of hydraulic fluid which in turns forces the caliper pistons against the rotor discs) to yield the SAME stopping power.

Single Disc

The Brembo aftermarket radial 16mm diameter master cylinders offer you the choice of a brake lever fulcrum-to-piston distance of either 16mm or 18mm. The stock Brembo lever has a 16mm dimension.

So your choice is either 16x16 or 16x18.

From the geometry, a 18mm lever will need to be pulled a 11% shorter distance than a 16mm lever but will at the same time require more lever force than a 16mm to stop the same distance.


Dual Disc

The Brembo aftermarket radial 19mm diameter master cylinders offer you the choice of a brake lever fulcrum-to-piston distance of either 16mm, 18mm or 20mm. The stock lever is 16mm.

So your choice is either 19x16, 19x18 or 19x20.

19x16 (stock) requires the least less lever effort but the longest pull distance.

19x18 requires 11% lighter pull and 11% longer pull distance than the 19x20 MC. More feel (better modulation characteristics) than the 19x20

19x20 requires the most lever force but the shortest pull. More like a trigger action.

Some riders think that this short-pull trigger action means that they have "better" brakes, but they don't - at least not for all riding conditions. What they do get is the same braking power with poorer modulation (feel) characteristics. Good for the track perhaps, but often dangerous on the street, especially in the wet. In an emergency, most of us have the instinct to grab a brake hard. So if you value a better feel, when choosing between the 19x18 and the 19x20 for the street, go for the 19X18. Better still stay with Ducatiís choice, 19x16.

On the other hand, some prefer their lever hard.

So again, I'm not suggesting that every rider will have the same preference in a braking system's modulation characteristics. Depending on your preference (or need) you can have brakes with an initial vague feeling, a strong initial bite, or something in between. You can select pads that have better high temperature behavior. On a race bike you can select brake pad and rotor material that will survive a race without needing replacement, but on the street, materials need to be more durable and function under less severe braking conditions and more varied weather conditions.


Master Cylinder Piston Diameter Selection

Brembo makes 16mm diameter piston master cylinders for use with single caliper brakes and 19mm diameter for use with dual calipers. Why? To give the proper modulation characteristics at the lever. The different diameter MC pistons change the hydraulic relationship between the master cylinder and the caliper pistons.

The hydraulic advantage is the total area of the caliper pistons divided by the area of the master cylinder.

For example:

The Brembo Goldline front caliper has four pistons. Two are 30mm diameter, two are 34mm.
The Brembo Monoblock front caliper has four pistons. Two are 32mm diameter, two are 36mm.

Case 1: A single Goldline actuated by a 16mm MC.

2(30 x 30 + 36 x 36) / (16 x 16) = 2(900 + 1296)/256 = 17 >13

Case 2: Dual Goldlines actuated by a 19mm MC.

4(30 x 30 + 36 x 36) / (19 x 19) = 4(2196)/361 = 27 < 24 > 23 (firm)

Case 3: Dual Monoblocks actuated by a 19mm MC.

4(32 x 32 + 36 x 36) / (19 x 19) = 4(1024 + 1296)/361 = 27 < 26 > 23

It has been my experience that there is a "sweet spot" in the range. I like ratios in the 27:1 range-2 finger power brakes, feeling some line and/or caliper flex.

23:1 is at the other end of the spectrum-firm.


Case 4: Dual Goldlines actuated by a 16mm MC.

4(30 x 30 + 36 x 36) / (16 x 16) = 4(2196)/256 = 34 > 27 (loose)

Case 5: A single Goldline actuated by a 19mm MC.

2(30 x 30 + 36 x 36) / (19 x 19) = 2(900 + 1296)/361 = 12 < 23 NOT GOOD

Ratios lower than 23:1 produce a lever feel so "wooden" as to have little, if any feel.
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Old 16-Mar-2005, 06:48 PM
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Old 16-Mar-2005, 06:53 PM
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I was just going to say that!

Nice one Shazaam, expert advice as always. It appears I've done the RightThing by going to twin Goldlines up front (40mm spacing off an early 916) with a matching 916 style master cylinder then!

Now, if you'd like to knock up one of your charts for the gear ratios and sprocket sizes for the 600ss, I'd be most grateful
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Old 16-Mar-2005, 06:53 PM
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PS. don't forget to add the chain link length in there too
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Old 17-Mar-2005, 09:35 AM
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That just what I needed. Thanks a lot, I just need to print that of and read it a few times.
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Old 17-Mar-2005, 03:25 PM
GlennG GlennG is offline
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Hi,

Quick intro - I know Phil (fil2) as we work at the same place and he oftens talks about the DCS club events and more recently what he's doing with his DD bike. I've been watching the DD forum with interest and until now not posted any replies, but Phil's away for a few days and I thought I might be able to help Antonye, at least until someone who knows excel properly!

"Now, if you'd like to knock up one of your charts for the gear ratios and sprocket sizes for the 600ss, I'd be most grateful"

There's probably prettier spreadhseets outhere but this should give you and understanding of the effect of changing front and/or rear sprockets vs engine revs at your critical points of the circuit ie end of straights max revs in top gear or not:


You'll need to measure the circumference of you rear tyre as the spreadsheet value 77" could well be out (no bike to measure yet!) and the gear ratios and primary ratios were found on the internet for 600ss I beleive, but again you may wish to doublecheck them.

I've added multiple entries with various engine rev limits (which you can modify to suit). So with this printout at the track you can have a good guess at what changes are needed if say you are a few hundred revs over or under your required limit, hopefully this waffle will make sense when you open the spreadsheet up and adjust to suit.


Good luck to everyone at Cadwell.


Cheers
Glenn
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Old 17-Mar-2005, 03:31 PM
GlennG GlennG is offline
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Hi Weeksy,

Yes your name has come up a few times ( all good though, from what I can remember!)

Cheers
Glenn

P.S
Not sure if my gearing attachment worked, I'll try again here
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