Brake piston stuck

[Firewa11]

I had a front brake failure at Cresson a few years back on the zx10.. Not a good feeling when you've just passed a cmra buddy you've been chasing and have the throttle pegged. Let off the gas and grabbed the lever... Straight to the bar with no resistance.


Thank god for the slipper clutch

Had that happen when I glassed a set of pads out at Eagle's Canyon coming off that long back straight. That's a pucker moment from hell!

[fixxervi6]

I had a front brake failure at Cresson a few years back on the zx10.. Not a good feeling when you've just passed a cmra buddy you've been chasing and have the throttle pegged. Let off the gas and grabbed the lever... Straight to the bar with no resistance.


Thank god for the slipper clutch

How did a slipper help you in that situation?

[Firewa11]

To provide max engine braking power, squeezing as much out of the back brake at the same time... After that happened I started changing pads before every track day / race weekend.

[Rhino]

To provide max engine braking power, squeezing as much out of the back brake at the same time... After that happened I started changing pads before every track day / race weekend.

1. How does engine braking help you more than your rear brake? Your rear brake can brake to the limits of traction.

2. Was it failed pads that made your lever go to the grip? Sounds like a hydraulic issue to me.

[Stardog]

Perhaps the rear suspension articulates more correctly with engine braking and stays a bit more planted? Hell I don't know...

[milesmiles]

Even if you are applying rear brake, engine braking helps slow the bike down

[Rhino]

*facepalm*

If your rear brake can brake to the limits of traction, how is engine braking going to help you slow down more?

What gives out first under hard braking, the brake pads or your tires?

[Stardog]

Well, the engine braking obviously lets the wheel continue to spin, I would think that is kind of like feathering the brakes in a car with no anti lock. And to be fair I have driven a 66 Mustang that could lock up the brakes on the highway. That didn't mean that it could stop worth a damn.

[DLSGAP]

Right... I only had to shed about 25 or 30 mph to make the next turn... Downshifted 2 gears and feathered the rear brake... It slid a little, but not quite to the point of backing it in. Had I been all over the brake, chances of it locking were greater. The slipper clutch helped me maintain traction to control the corner entry by helping match the engine and wheel speeds.

The issue was attributed to stock lines and fluid with a design flaw in the calipers. They were made with thinner piston walls which transferred more heat to the fluid. I boiled the fluid and lost pressure. Did a caliper swap and didn't like the feel. Did stainless lines, rbf600 and vesrahs and it resolved the issue

[fixxervi6]

Slippers give you way less engine braking than non-slippers, when the rear tire tries to turn the engine (which results in engine braking, and in excess can over drive the engine and cause wheel hop) the clutch - slips, you have way less engine braking with a properly tuned slipper clutch than a bike without it. Anyone that doesn't believe that take something like miles 675 out vs my GSXR 750 and pop a gear at high rpm and see which bike engine brakes so hard it tries to throw you out of the seat.

And as Rhino pointed out, the rear brake is strong enough to max out your braking adding engine braking on top of that doesn't help you.

Slippers also work in one direction, so even when applying heavy braking the engine will still drive the rear wheel if you give it gas.

I love my slipper but I don't understand how it could help me if I lose my front brake.

edit: just read the last post, if you dumped two gears I'm going to assume your slipper was slipping, aka very little engine braking allowing you more control with the rear brake vs dealing with large amounts of engine braking + rear brake?

[milesmiles]

I see what you are saying now. I just look at it as the rear break locks up sooo easy and with engine braking that helps a little not doing that because you are slowing down the rate at which the tire spins

[Firewa11]

I would say it was more of an oh-shit moment and when you're screaming down the track at a 90 degree turn and expecting the brakes to work and they don't. Don't have a lot of time to think about "let's see, with force X applied to rear gyroscope, max friction will be obtained by applying optimal braking effort"... you're staring down the outside of the corner thinking oh shit this is gonna hurt. Was downshifting / using engine brake the best solution? Hell if I know, what I do know is that while I ended up taking that left hander incredibly wide and at a high lean angle, the solution I chose worked for me at the time.

For me it wasn't a hydraulic issue, the pads themselves were glazed, as in, with max application of brake lever they weren't stopping the bike. Not like with rubber brake lines and the brake lines expand (which is why I stress braided steel lines for anyone on the track), not pushing enough fluid to the calipers. When I got the front pads off and looked at em, they were smooth and polished like glass. Learned later you can deglaze them with some steel wool / wire brush, but once it happens you never fully trust those brakes again. That's the same time I quit running Galfer pads and went EBC and never had it happen again.

[Stardog]

So what is the procedure for deglazing rotors? Like what grit sand paper? I also have a die grinder, would a wire wheel do the trick?

[fixxervi6]

I see what you are saying now. I just look at it as the rear break locks up sooo easy and with engine braking that helps a little not doing that because you are slowing down the rate at which the tire spins

Engine braking will slide the rear quite easy. Every time I go to a non-slipper bike it takes my brain a couple rear tire slides to go "OH yea, I forgot I can't do that on this" and then I'm good.

going from non-slipper to a slipper wasn't that noticeable for me

Going from a slipper clutch to a non slipper sucks ass, I have touch the bike with a softer touch on the clutch and I tend to over drive the engine (used to just banging through the gears).

On a slipper I can downshift beyond what I normally can, slow down into the turn, then get back on the gas at a higher RPM, aka I can get all of the shifting done real early for the turn, for example.

Lets say at turn Y at the apex I can drive out in 2nd gear at 90mph (just making this up) but I come into the turn in 4th gear pretty hot. In the straight before tip doing well over 100 I can just pow pow down to 2nd gear and the engine does not over rev, tip in, trail brake to apex, then get on the gas. Non slipper you can't do that, you'll over drive the engine, blipping or not.

Watch the onboard telemetry of some of the race bikes, look how high their RPM is in like 5th gear and those guys will just dump down to 2nd gear boom boom boom. 2 strokes can do that and slippered 4 strokes can (as long a the slipper is tuned properly).

I buried the tach on the 250 a few times "setting up for corners" it doesn't have enough engine braking to tell me "hey asshole don't do that" and it doesn't have a slipper so I over reved the engine more than a few times, once so bad the engine cut out entirely and the oil light came on, I thought I killed it.

If you have a slipper and your feeling significant engine braking or it pushes your revs up hard past the limiter on downshifts take it to Scott and tell him you want it tweaked.

Hijack over

[Firewa11]

I would say honestly a slipper clutch is really a necessity when you're trying to milk every ounce of throttle time on a straight before a corner, and you have limited time to downshift while braking to get set up for the next corner. Slipper clutches still chatter the rear wheel, but on a bike like my first bike (Katana) without a slipper, downshifting too soon caused the rear wheel to basically skid along, which is waaaay worse than a little chatter.

So, I guess all that being said, the slipper clutch wasn't so much to slow the bike down, but to get me low enough in the RPM band to negotiate the corner. And when that particular situation happened to me, it was just a track day, I wasn't that fast yet, I wasn't racing, etc. I would be willing to bet looking back, the speed and line I took around that corner was probably the normal speed I took it later on

[DLSGAP]

That was too long to read lol..


The back end is easy to slide around on my yammi. My fiancé gets pissed when I back it in to the entrance to our neighborhood

[milesmiles]

After I think about it I've never used engine braking with rear break so I probably should keep my mouth shut. Although I still see it as helping slow the engine down therefore helping. However little it may be

[Firewa11]

Yeah I think the biggest benefit is for a) screwups and downshifting too soon or going down instead of up a gear, and b) allowing you to downshift with the bike is still not slowed down to the max RPM of the engine in that next lower gear... all by slipping the clutch for you instead of suddenly hitting the rev limiter and having a rear wheel spinning faster than the engine can go.

I think that's how you can blow an engine too right?

[fixxervi6]

Rev limiters don't work on downshifts, when 4 strokes and 2 strokes were mixed in races 2 stroke riders where destroying the valve's in the 4's when they used them because they were downshifting them too much and over revving, a problem 2 strokes don't suffer from. slippers give you the ability to do something that non-slppered 4 strokes can not.

Blip all you want, you still can't get the same work out of the bike as you can with one running a slipper.

[Firewa11]

Ahhh, that makes sense then, I always thought the engine sounded higher pitched than normal max RPM when downshifting too quickly. Wasn't looking at the tach when it happened.

[Striple]

I'm so used to running without slippers, the rear stepping out doesn't bother me anymore at all. In fact, when the front tire squirms from heavy braking and the rear is simultaneously kicking out from banging it down a couple of gears, everything actually feels pretty controlled.

[DarcShadow]

I see what you are saying now. I just look at it as the rear break locks up sooo easy and with engine braking that helps a little not doing that because you are slowing down the rate at which the tire spins

The brake slows down the rate at which the tire spins. If you're braking to the max, the wheel will be slowing the engine down, hince the need for blipping and down shifting. Engine braking is the least effective form of braking and if you're using it, you are either letting off the gas too soon and coasting, or not braking to your full potention (again letting off the gas and braking too soon).

[Firewa11]

I'm so used to running without slippers, the rear stepping out doesn't bother me anymore at all. In fact, when the front tire squirms from heavy braking and the rear is simultaneously kicking out from banging it down a couple of gears, everything actually feels pretty controlled.

Yeah, I finally got used to that, first time it happened to me it felt like I was skating on ice, but after that I realized it wasn't all that unstable, even though you're at the absolute limit, it's amazing how much more our machines can do vs. what we feel we can do on them.

If you've never had the opportunity to cornerwork a CMRA event, I highly recommend doing it, and try to get on a corner where you are close enough to watch as the experts brake hard and a hit the corners. Watching the likes of the top CMRA experts braking before turning in, and watching the extreme lean angles they hit through the corners is insane. I watched Ty braking and the way his bike was sliding around front and rear it really looked like he had the wheels locked up, and then bam into the corner. Also, hearing the difference in 'coast time' was impressive too, you hear the novices coming in and you hear the engine downshifting as they brake, then you hear a coast for a few seconds, then hear them on the gas as they negotiate the turn. The experts cut that coast time to fractions of a second before they are right back on the gas.

[Rhino]

Well, the engine braking obviously lets the wheel continue to spin

ORLY?

Get up to 60, downshift to first, dump your clutch. See what happens to your rear tire if you don't have a slipper clutch.

[Firewa11]

Hah, on my bike if I get up to 60 I'm only halfway through first