Front, Back or both???

[Stasher]

Your front brake on a modern sportbike is responsible for more that 70% of the braking force, it's more like 90-100%.  If your braking near the limit of the bikes capabilities the back end will want to come around, causing the bike to slide sideways; this will worsen if the back brake is over applied.  The rear brake may be used at high speed to settle the chassis before going into a corner, helping to keep the bike flat but that will also effect bikes ability to turn into a corner.

When I race the rear brake is rarely touched, when I'm on the street it's used for slower speeds with the front but never on it's own. 

BTW: trail braking is braking into the corner up to the apex with the brake pressure decreasing until you nearly hit the apex, it's not about using the rear brakes.

A fellow racer speaks the truth

[antichrysler]

break
–verb (used with object)
1. to smash, split, or divide into parts violently; reduce to pieces or fragments: He broke a vase.
–noun
2. an act or instance of breaking; disruption or separation of parts; fracture; rupture: There was a break in the window.



brake
–noun
   1. a device for slowing or stopping a vehicle or other moving mechanism by the absorption or transfer of the energy of momentum, usually by means of friction.
–verb (used with object)
        2. to slow or stop by means of or as if by means of a brake.


[/OCD grammar nazi]

haha! i conquer

Is this actually true??

 I've never heard of the engine being considered a gyro that helps stabilize a bike. I understand where the theory may come from, but engine bits spin in all sorts of directions and I would have thought all that commotion would neutralize any possible benefit

I think Toms right about the engine being used as a gyro.  Even if you think about the forces going in all directions you have to think of the summation and the final number that you have which can be calculated into 3 forces for the 3 dimensions that are all perpendicular to eachother, think back to 1st year physics i hat, j hat, and k hat.

[Westicles]

haha! i conquer

Concur?  Or did you actually mean conquer?  Or is it a running gag of yours that I'm just not understanding?

[TGSXR]

Wes, you beat me to it.

Regarding the boxer motors... My old man's R1100RT will pull to the left IIRC when sitting at a light and blipping the throttle. You'd be surprised about the gyroscopic force of the crankshaft in your typical transverse I4 sportbike motor. I would imagine that not many guys have held the crank shaft on its own. When I rebuilt the motor on my 1100, lifting the crank caught me by surprise. Its bloody heavy. I would venture a guess as to well over 50lbs. This will be much heavier than the wheels - and you combine this with the fact that the crankshaft is spinning at a higher rate than the wheels will be, I would say that the gyroscopic effect of the crank will be more than that of the wheels.

The gyro aspect of this topic begs for a new thread!

[T-bar]

Engine parts don't spin in all different directions. If you think about it, almost everything in a motor that turns, turns in parallel planes.  Almost all rotation is parallel and in the same direction.  So while there may be many individual gyros inside the engine, the engine collectively is one large gyro.

[GMCdriver]

I understand how all the moving parts of an engine moving in parallel plane rotation create a gyroscopic effect however...
I have some doubts that it is the gyroscopic force of the engine that stabilizes the bike during low speed manouvers.
If it were simply the gyroscopic force of the engine then why would there be any need to feather the clutch and rear brake against each other?
One would be able to get the same gyroscopic force simply by holding in the clutch and reving the engine but we know that doesn't actually increase stability.

Answer to original question(back on page 1) - I use both brakes and I have no idea what % I apply to the front or rear.  For those of you that do know, how do you measure or determine that you are applying 90f/10r or 75f/25r or whatever.

[antichrysler]

I say just ride.  Apply both.  If you put too much on the back tire it'll lock so lay off a bit.  Better to have too much on the back than on the front.  Just treat riding a motorcycle like riding a bicycle.  On a pedal bike I always apply what I think is a safe amount without locking the back tire, then apply the front according to comfort.  You should have a pretty good idea if you're going to go over the handlebars.

Long story short...... just get to know your bike and ride it the way that maximizes your braking performance.  As you get more experience it will just come as second nature.

[orion]

I have issues with people using your clutch for braking.  Can anyone explain exactly how the safety course teaches that.  Honestly (WARNING - OPINION ON THE WAY) I've heard a few things the safety course teaches that I have issues with - can someone educate me? 

haha...you have issues about some of the things the course teaches?

This coming from a guy who uses only his rear brake the majority of the time?

I use my rear 80% of the time for casual braking. in a hurry use both

"in a hurry" - you won't be in the habit of using both.

[antichrysler]

"in a hurry" - you won't be in the habit of using both.

Yeah..... what if your throttle starts sticking and you need to overpower your engine using the brakes but you don't think of the emergency kill switch or pulling the clutch or putting your bike in neutral...... you'd be screwed!!

[cowboyrt]

Fair enough, but i do practice my emergency braking. i just feel alot more comfortable with my back tire underload than my front. when i need to stop in a hurry, its front time.
thanks for quotting the "can some one educate me" comment.  Clearly i knew i was missing something.   
Another benifit to letting my engine and rear brake slow me down - cheaper to replace one set of pads than two lol

[TGSXR]

Fair enough, but i do practice my emergency braking. i just feel alot more comfortable with my back tire underload than my front. when i need to stop in a hurry, its front time.
thanks for quotting the "can some one educate me" comment.  Clearly i knew i was missing something.   
Another benifit to letting my engine and rear brake slow me down - cheaper to replace one set of pads than two lol

And rear tires are cheaper than front tires?

[claffix]

I'm not gonna take it easy on the brake that provides 70-90% of the braking force just to save a couple bucks on brake pads.  If you only wanna replace one set of pads, make it the front ones.

[cowboyrt]

For what its worth 98% of my braking is not "emergency braking"

[orion]

That's my point. When you are braking with just your rear 98% of the time - you won't be in the habit of utilizing the front brake the 2% of the time when you need it most. And that habit will come back to bite you when you're least expecting it dude.

[cowboyrt]

cody pleads : no argument
lol you got me