Oversize Rotor/Caliper

[SBKBee]

     I've always wondered why I never see anybody upgrading the rotor size on the FJ.  The FZr1000 320mm bolts right on to the stock wheel and a plate can be made to use the stock calipers.
     
     I understand a lot of folks swap forks, so wheel size, calipers, rotors all follow along, but, with the RPM emulators springs oil etc... the standard forks work great.

     So has anybody made brake plates to offset the 300mm to 320mm?

[aviationfred]

I believe there are actually brackets available to do just that on the 1989 and later forks. Dale (Shaarth) has a set of 320mm FZR rotors on his 1989 with Hyabusa 6 piston calipers mounted to brackets from Morley's Muscle http://morleysmuscle.com/



Fred

[PaulG]

I remember reading an article in an automotive column regarding stock discs vs larger aftermarket ones.  I don't know if this is translatable directly to motorcycles but the gist of it was this (from my hazy memory  ):

• Stock discs are specifically engineered for several factors - like weight, suspension, original spec tires, required safe stopping distances, etc.
• These requirements factor in for the design of the discs/pads in order to heat the disc up quickly enough to provide the friction/torque needed to grip the disc
• Going to a larger disc may theoretically seem better - but - larger discs require longer to heat up - if you haven't changed your calipers to match
• Because they take longer to heat up - you actually increase your stopping distance - even more so in the rain or cold
• For general street use this would be useless - even dangerous - esp if boulevard cruising is the main function of the vehicle
• The larger discs may require more aggressive driving/riding  (not necesaarily faster) to keep the heat in them so they will stop you in a safe distance

Make sense?    Does going from 300mm to 320mm a big enough of change to require larger calipers?  I don't know the physics but then I remembered I had this on my hard drive. Its from a book called Motorcycle Handling and Chassis Design : The Art and Science by Tony Foale (2002).  I found it on the internet in a pdf file.  I thought of printing it out but it's 498 pgs long.     I copied and pasted an edited section (there were lots of charts and graphs) of braking basics, which explains - in great detail - some of what I tried to list above.  I also listed the table of contents below that.  The file is only 64Mb, so if this kind of stuff interets you let me know and I could email it to anyone.  You can PM me or just reply to the post.  If you are prone to moditis, this will get the monkey back on your back....     Sorry for the length - but it's cold & windy & snowy outside, and I have nothing better to do.  Well I probably do but it's too late in the day now...   

Motorcycle Handling and Chassis Design : The Art and Science

Braking - The Basics

At the most fundamental level, vehicle braking is the conversion of kinetic energy into heat energy.
Sometimes a small amount of the kinetic energy is initially converted into sound and light, but this
ultimately turns to heat as well. Brake squeal is the release of the sound energy and when a disc
becomes hot enough it glows red and so dissipates some energy as light.
Kinetic energy is the energy possessed by any moving object, it is dependent on the mass of the object
and the square of its velocity. To slow from a high speed to a lower one we must remove the difference
between the kinetic energy levels at each of these speeds.  Fortunately, at higher speeds
the aerodynamic drag relieves the brakes from absorbing all of this.

The total amount of energy that must be dissipated for each 200 kg of laden mass to come to a halt from
different initial velocities is drawn for a hypothetical machine similar to a typical 500 GP racer.
Even at the relatively low speed of 125 km/h, the drag force adds 11% to the effect of the brakes alone.
As the aerodynamic force acts directly on the machine, it does not use up any of the potential grip from
the tyres, and so is additive to the deceleration provided by the brakes. In the rain the available braking
through the tyres is reduced and so air drag becomes relatively even more important. Rolling resistance
also adds to the total force slowing the bike but it is a smaller effect. Friction in the wheel bearings, chain
and engine/gearbox has to act through the tyres to produce a retarding force, just like the brakes, and so
it is implicitly assumed that this is part of the total force from the brakes. Engine braking is the most
significant of these and in many cases is the principal braking mechanism at the rear.

The deceleration possible of a bike under various conditions is a good measure of the efficiency of the
braking system and grip of the tyres, but in a racing context it is the time to slow from one speed to
another that translates into slower or faster lap times. On the other hand, when riding on the road it is
most often the distance required to stop from a given speed that is of most importance. This relates
directly to collision avoidance and general safety.

The total amount of energy to be dissipated by the brakes and engine friction etc., is
the total amount of heat that must be got rid of. However, that gives no indication of how hot the brake
system will get nor of how much cooling rate is necessary to maintain workable temperatures of these
components. To calculate these things we must also consider how quickly we stop from a given speed.
It is the time rate of dispersing this energy that is important and this is called "braking power".  A heavier
road bike would produce more power during emergency stops from the same speeds than a relatively light-weight racer.

To put this into perspective, we can see that to slow this race bike from 230 km/h we produce an
average power in the brakes of about 60 kw., that is the same amount of heat to remove that we would
get from one thousand 60 watt light bulbs. Most of this will be handled by the two front discs. Little
wonder that brake discs often glow red. For those more used to thinking of power in terms of BHP, 60
kw. is the same as 80 BHP.

The actual temperature that the disc reaches depends on three factors.
·  Braking power required.
·  Degree of cooling.
·  Heat capacity of the disc.

Brake cooling comes from several sources, but the principal one is from the flow of air carrying the heat
away. Some heat travels through the mounting components and into the wheel, but most of this is
ultimately taken away by air cooling also. Heat radiation removes some of the heat, although this is
relatively more important a factor as the disc gets very hot. Radiation is the same process by which we
receive heat from the sun. To maintain a steady temperature the rate of cooling at that temperature
must be equal to the rate of heating or in this case the braking power. Cooling from all sources
increases as the disc temperature rises, and so the temperature will continue to rise until this equilibrium
condition is reached.

Heat capacity is the measure of how much heat we have to put into an object (brake disc) to raise its
temperature, or in other words, the amount of heat stored in a disc at a certain temperature. For a given
material the heat capacity depends on the mass of the disc. The heat capacity of a braking system
doesn't affect the ultimate steady state temperature reached, but it does affect how quickly the disc
reaches that temperature, and how quickly it cools down after the braking has ended.

In the past, the pad materials in use would lose some of their grip at high temperatures. Called brake
fade this could be a serious problem when braking from high speed, and high heat capacity braking
systems could be of considerable advantage by keeping the disc cooler for longer. It is obvious just from
a casual glance that today's brake discs are much lighter than those from a couple of decades back, for
both racing and sports bikes. Amongst the reasons for this are reduced gyroscopic effect for faster turnin
and less unsprung mass for improved roadholding and general suspension performance, but also to
reduce the heat capacity. Modern high performance braking pads use materials that work better at
elevated temperatures and so to get a consistent feel when first applying the brakes we need the discs
to get up to temperature as quickly as possible.


Contents

1 Function and history
Some basic definitions ................................................... 1-1
Function.......................................................................... 1-3
History............................................................................. 1-4
Front suspension.......................................................... 1-16
Rear suspension........................................................... 1-23
Spring types.................................................................. 1-29
Load Compensation ..................................................... 1-30

2 Tyres
Weight support ............................................................... 2-2
Suspension action.......................................................... 2-4
Tyre stiffness or spring rate............................................ 2-8
Contact area ................................................................. 2-11
Area when cornering .................................................... 2-15
Friction (grip) ................................................................ 2-15
Braking & driving .......................................................... 2-17
Cornering...................................................................... 2-17
Mechanisms of grip ...................................................... 2-17
Under- and over-steer .................................................. 2-27
Construction ................................................................. 2-32
Materials ....................................................................... 2-34
Summary ...................................................................... 2-34

3 Geometric considerations
Basic motorcycle geometry ............................................ 3-1
Trail................................................................................. 3-1
Rake or castor angle (steering axis inclination) ............. 3-5
Wheelbase.................................................................... 3-15
Wheel diameter ............................................................ 3-16
Other considerations .................................................... 3-18
Angular motions............................................................ 3-22

4 Balance and steering
Balance........................................................................... 4-1
Steering .......................................................................... 4-3
Gyroscopic effects only .................................................. 4-9
Gyroscopic with tyre camber force only. ...................... 4-12
Gyroscopic with tyre camber and steer forces............. 4-14
Tyre forces only – no gyroscopic effects. .................... 4-18
Body lean only – no steering........................................ 4-20
Conclusions: ................................................................. 4-23

5 Aerodynamics
Drag ................................................................................ 5-1
Evolution of the racing fairing......................................... 5-9
Internal air flow ............................................................. 5-10
Lift ................................................................................. 5-11
Airflow evaluation ......................................................... 5-18
Side wind stability (traditional view) ............................ 5-21
Steady state directional stability................................... 5-24
Dynamic directional stability ......................................... 5-28
Summary ...................................................................... 5-31

6 Suspension principles
Springs............................................................................ 6-1
Damping ......................................................................... 6-8
Sprung and unsprung mass ......................................... 6-21
Basic suspension principles ......................................... 6-21
Other factors................................................................. 6-31
Lateral suspension ....................................................... 6-42
Summary ...................................................................... 6-49

7 Front suspension
Head stock mounted forks ............................................. 7-1
Alternatives to the head stock mounted fork................ 7-13
Hub centre steered....................................................... 7-14
Double link.................................................................... 7-18
McPhearson strut based .............................................. 7-27
Virtual steering axis ...................................................... 7-31

8 Rear suspension
Effective spring rate........................................................ 8-3
Chain effects................................................................. 8-11
Wheel trajectory............................................................ 8-15
Structural ...................................................................... 8-16
Single or dual sided...................................................... 8-19
Summary ...................................................................... 8-26

9 Squat and dive
Load transfer .................................................................. 9-1
Squat and dive................................................................ 9-4
Shaft drive....................................................................... 9-4
Chain drive.................................................................... 9-13
Aerodynamic squat....................................................... 9-25
Braking reaction (rear).................................................. 9-26
Dive (front) .................................................................... 9-29
Dynamic effects............................................................ 9-37
Summary ...................................................................... 9-47

10 Structural considerations
Fatigue.......................................................................... 10-1
Structural efficiency ...................................................... 10-1
Triangulation................................................................. 10-2
Beam frames ................................................................ 10-5
Triangulated frames ..................................................... 10-9
Tubular backbone....................................................... 10-11
Structural comparison ........................................10-12
Fabricated backbone.................................................. 10-14
Monocoque................................................................. 10-15
Structural engine ........................................................ 10-17
Conventional multi-tubular ......................................... 10-20
Twin-spar .................................................................... 10-23
Other types ................................................................. 10-27
Summary .................................................................... 10-28

11 Engine Mounting

12 Braking
The basics .................................................................... 12-1
Effects of CoG height ................................................... 12-7
Generation of torque .................................................... 12-9
Hardware .................................................................... 12-10
Discs ........................................................................... 12-11
Calipers....................................................................... 12-14
Pads............................................................................ 12-15
Linked brakes ............................................................. 12-15
ABS............................................................................. 12-17

13 Materials and properties
Typical properties of some common materials ............ 13-3
Frame ........................................................................... 13-5
Wheels .......................................................................... 13-8
Fuel tank ..................................................................... 13-13
Brake discs ................................................................. 13-13
Bodywork.................................................................... 13-13

14 Stability & control
Under-/over-steer ......................................................... 14-2
High-siding.................................................................... 14-7
Stability under braking.................................................. 14-9
Instabilities .................................................................. 14-10
Damping ..................................................................... 14-14

15 Performance measurement
Track side ..................................................................... 15-1
Laboratory..................................................................... 15-9
Strength analysis .......................................................... 15-9
Measurement and simulation..................................... 15-12
Future development ................................................... 15-14

16 Practical frame building
Welding......................................................................... 16-1
Distortion....................................................................... 16-3
Gussets......................................................................... 16-5
Jigging .......................................................................... 16-6
Tube profiling................................................................ 16-8
Tube types .................................................................... 16-9
Tube sizes .................................................................. 16-10
Frame finishes ............................................................ 16-11
Design layout .............................................................. 16-12

17 Case study
Measurement................................................................ 17-2
Main frame.................................................................... 17-2
Engine mounting........................................................... 17-5
Results .......................................................................... 17-5
Material ......................................................................... 17-5
Swing arm..................................................................... 17-5
Forks ............................................................................. 17-6
Caution ......................................................................... 17-6
Tuning........................................................................... 17-6

18 Future developments
The status quo.............................................................. 18-1
Future possibilities........................................................ 18-2
Active suspension......................................................... 18-2
Rheological Fluids ........................................................ 18-4
Two wheel drive (2WD) ................................................ 18-4
Two wheel steering (2WS) ........................................... 18-8
Feet-Forward motorcycles. (FF)................................ 18-12

Appendices

A1 Experiments with rake and trail
Rake..............................................................................A1-1
Trail...............................................................................A1-7
Conclusions ..................................................................A1-8
Post script.....................................................................A1-8
A2 Glossary of terms
A3 Units conversion
A4 Gyroscopic effects
A5 Basic physics of motorcycles
Basic Trigonometry ......................................................A5-1
Units of angle................................................................A5-2
Velocity .........................................................................A5-3
Acceleration..................................................................A5-4
Mass .............................................................................A5-4
Momentum....................................................................A5-5
Newton's laws...............................................................A5-6
Force and weight ..........................................................A5-7
Moments, couples and torque......................................A5-8
Centripetal & centrifugal force......................................A5-9
Addition and resolution of velocities and forces ........A5-10
Work, energy and power ............................................A5-12
Nomenclature and sign conventions..........................A5-13
Normalization..............................................................A5-14
A6 Analysis of mechanisms
A7 CoG and mass distribution of rider
A8 Typical data

[fj1289]

I'm thinking SBKBee has more practical experience with high performance motorcycle brakes than maybe half this list combined.  Several years ago (during the yahoo list days) I had the fortune to meet Superbike Bee and see his fully kitted FZ750 Suberbike racer (see his avatar) that had been returned to street use.   I don't recall any particulars, but as I recall the bike had done pretty well at the national level with him as the tuner.  I'm thinking he can show you several "specifically engineered" stock brake rotors that belong in a pringles can because they couldn't hope with the heat loads they were subjected to.   

I've wondered this one too - seems the next logical step for improving the brakes for reasonable cost and effort.   

[aviationfred]

    

     So has anybody made brake plates to offset the 300mm to 320mm?

I will get photos of Dale's front wheel with the 320mm rotors posted in a day or so.

I know that I really like the 320mm rotors on the gixxer wheel. 


Fred

[ribbert]

I remember reading an article in an automotive column regarding stock discs vs larger aftermarket ones.  I don't know if this is translatable directly to motorcycles but the gist of it was this (from my hazy memory  ):

• Stock discs are specifically engineered for several factors - like weight, suspension, original spec tires, required safe stopping distances, etc.
• These requirements factor in for the design of the discs/pads in order to heat the disc up quickly enough to provide the friction/torque needed to grip the disc
• Going to a larger disc may theoretically seem better - but - larger discs require longer to heat up - if you haven't changed your calipers to match
• Because they take longer to heat up - you actually increase your stopping distance - even more so in the rain or cold
• For general street use this would be useless - even dangerous - esp if boulevard cruising is the main function of the vehicle
• The larger discs may require more aggressive driving/riding  (not necesaarily faster) to keep the heat in them so they will stop you in a safe distance

Paul, I couldn't agree more but as I used up my weeks "rant quota" last night on clutches, I will be brief. Brakes need heat to work properly and it is near impossible to match race track conditions on the road for a number of reasons, no matter how hard you ride.

Too much heat will fry your brakes, not enough and they won't work properly, the latter being the most common problem with road riding. It's rare to see someone ruin their front brakes from overheating on the road.
I often wonder when I see huge discs and 6 pot calipers, how on earth you get enough heat into them for them to work on the road. I recall a member here some years back saying the standard set up worked better than 6 pots and big discs. He had tried both.

What more do you need than one or two finger lock up with great feel?

Manufacturers can make discs any size they like and calipers with as many pistons as they like, there must be a reason they settle of the configuration they do. What about Buell discs, the biggest in the business, I don't recall ever reading a glowing review of their brakes.

My brakes are every bit as good as current BMW, Ducati, Yamaha, Triumph etc, all of which I ride regularly. I wouldn't mind trying a radial M/C though.

i second this opinion, i went with the EBC rotors , HH pads, and did the blue dots, XJR master
braking modulation and power rivals my modern sportbike that has a RC19 master and brembo full floaters
"confidence inspiring" is a great way of saying it

Noel

[fj1289]

Aren't we talking about rotors made by the same manufacturer from the same era that were used on a lighter motorcycle that would generate less heat to stop from the same speeds?  Doesn't seem like getting these rotors up to temp to function well in a daily basis would really be an issue? 

[SBKBee]

Yup. I was thinking of bolting on FZr1000 rotors, they are identical, and just make offset brackets.

My question was, anybody have a pattern for 300 to 320mm.

[PaulG]

Aren't we talking about rotors made by the same manufacturer from the same era that were used on a lighter motorcycle that would generate less heat to stop from the same speeds?  Doesn't seem like getting these rotors up to temp to function well in a daily basis would really be an issue? 

(Sorry for bloating an "Ask a simple question - need a simple answer" thread.)

Open for discussion I guess. With so many variations available - bone stock vs. bigger discs on stock wheel w/stock calipers vs... [insert combo here]

As we tweak our brakes with braided lines, blue/silver/gold dot calipers, different master cylinders - these definitely improve the feel of the brakes and may lead to more confidence in them.  Does this increase the stopping ability?  In one sense yes. If the rider has more confidence in the machines ability they may be able to stop/avoid quicker than previous.  But I think rider experience has a much greater effect on that than mechanics/physics. I think an expert rider on a dual set of drums might embarrass me on a test course. 

Does adding larger discs have any more to offer? Arguably to the average Joe I would say no. Would an expert rider be able to take advantage of it? Probably yes - but would an expert rider really need to? If you get my drift 

Do they look good - absolutely. Do they add value to the bike - depends on the seller/buyer. I should clarify I'm looking at this from a fairly stock bike. If you start adding front end conversions, USD fork conversions, lighter wheels, even rear end conversions, this may make it all a moot point.

Opinions? Rants?   

[aviationfred]

Here are photos of Dale Sharps 320mm rotors with Hyabusa calipers.



Fred

[fj1289]

Fred - any more details on those brackets?

Morleysmuscle doesn't seem to have a website any more - and the way back machine won't let me drill down far enough to get to the brake brackets...

Thanks!
Chris

[aviationfred]

Fred - any more details on those brackets?

Morleysmuscle doesn't seem to have a website any more - and the way back machine won't let me drill down far enough to get to the brake brackets...

Thanks!
Chris

Chris,

Try Morleys Muscle on Facebook. He has an active page there.

Fred

[fj1289]

Thanks - just found it from a link on the wayback machine archive

[SBKBee]

FJ1289, are you going to share what you found? Maybe post the link.

[SBKBee]

These are cool, you could use the 320's then use radial calipers.




http://www.ebay.com/itm/FZ1-FZ1N-FZ1S-YZF-R1-Beringer-Brembo-Adapter-Hanger-Bracket-100mm-/222407911443?hash=item33c88b6813