engine braking vs braking... braking

[ariacode]

Guy Martin's recent incident at IOMTT brought up something that's confused me for a while: what are the functional differences between engine braking and braking with the pedal?

Intuitively they seem very similar -- and exactly the same in toy force models i can picture -- but neutral+pedal feels more out of control to me than always having the engine engaged, whether I'm driving a car or riding a bike. Then there's Guy Martin's crash.

I guess I can accept that having the engine engaged will help keep the rear wheel spinning at a more consistent rate when performing aggressive, tire-smoking riding like guy does. But then why do I feel like I'm just a passenger when braking in neutral during my dopey beginner/intermediate riding?

What's going on here? Why could Guy Martin not pedal-brake his way out of that scenario? Was it a matter of not having enough time to adjust his braking method? Is my feeling of being out of control just unfamiliarity with the effects of the controls when in neutral, or is there really something substantial that is lost?

 

[Krooklyn]

When you ride a 2T first the time in a while the lack of engine braking is the first thing you notice. If you're expecting it (as most ppl are that ride a 4T) and it's not there it can be a pretty terrifying experience, especially at the speed they go around the IoM.

 

[stangmx13]

Guy was expecting some engine braking, got none, and missed the line. perhaps he had .5s to realize he screwed up the downshift and needed to apply more brake (either end), perhaps not. but thats what happens when pushing the limit on a "track".

IMO, bikes feel weird with 0 engine braking because we never enter corners that way and arent used to it. the feeling of a lack of control stems from exactly that. when engine braking, u can very easily adjust throttle to remove all engine braking and accelerate. when it neutral, the rear brake cant cause accel so it literally offers less control.

there is a subtle geometry difference btw rear brake and engine braking because of the chain pull force. but the effect is tiny because engine back torque is very small. its even smaller on a bike w/ a slipper clutch or with ride-by-wire setup to reduce engine braking. but we all still feel better entering a corner in gear because thats what we are used to.

 

[Honey Badger]

To be honest it reminded me of a moment I had with an instructor a number of years ago.

He came over to and waved me over to my bike to "show me" something.

He grabbed the brake lever, and said: "See this?"
Me: "yes"
Him (grabs throttle): "See this?"
Me (wtf?): "yes"
Him (grabs brake): "see this?"
Me (getting mildly annoyed): "Yes."
Him (shakes brake lever): "THIS is how we slow down the bike!"
Him (twists throttle): "See this?"
Me: "yes"
Him: "this is NOT how we slow down the bike"
Him (grabs brake again): "THIS is how we slow the bike"
Him (grabs throttle): "this is NOT how we slow the bike. Got it?"
Me: "ya : |"

As dorky as that interaction made me feel, it has actually saved my bacon twice on track - once when I got a false neutral going into a corner, and once when I missed a downshift. My brain remembered this embarrassing interaction, and I focused everything on my brakes and rode out both situations still keeping the bike on pavement.

I think Robert pretty much nails it - Guy was expecting something, had his plan set around that, and when he didn't get what he expected, his line was messed up, curbing hit, no throttle to adjust with, and a crash following.

Anyone who rides a bike to the limits those guys do can have serious consequences if something goes against plan.

For the rest of mere mortals, I think the advice I was given is pretty damn applicable.

 

[ariacode]

Thanks, all. Really helpful to have that cleared up.

 

[Schnellbandit]

Kinda depends on the situation. Say you are exiting the freeway and at the end of the exit is a pretty sharp turn. As you exit you can use engine braking to slow your rate of speed and then without having to sync engine speeds because you'll be in an appropriate speed (gear) throttle application is a one step process.

On the street, V-Twins like the moto guzzi and others can provide quite a bit of "engine braking", and riders can use it to their advantage.

Certain shaft drive bike handle quite different than chain drive so only considering chain drive bikes leaves out quite a few others.

With good throttle, clutch and shift control, a rider can use engine braking to a great advantage and be smooth enough that it feels like an automatic. IMO not using engine braking where it can benefit you is wasting a resource.

 

[NSR500]

I had the reverse experience because my first bike was 2T. The first time I rode a 4T twin I freaked out at the engine braking.

 

[Holeshot]

Engine braking has the same effect as a rear brake: it slows the rear tire(s) at roughly the same rate as the front tire. On a motorcycle, it also pressures the rear end downward, keeping the chassis more neutral. If you've ever gotten a false neutral in a car at speed entering a corner, the result is pretty darn close and usually results in understeer.

Engine braking is called "braking" because that's exactly what it is. While we don't use the engine to primarily slow the bike, we do use RPM to stabilize the chassis into a corner which has the effect of slowing the rear tire. When a motorcycle false neutrals, there is nothing slowing the rear tire while we're using brakes to slow the front tire.

Where does unassisted potential energy go in a false neutral situation?

 

[EastBayDave]

Where does unassisted potential energy go in a false neutral situation?

off the road, or PAST the place you expected to have it. =....waaaaaaaa SPLAT! :laughing

That's why having dirt bike/& or 2-stroke experience, really teaches you the difference between having engine braking & not having it.

As mentioned already, it can & will be for most, part of the "plan." It eventually becomes instinctive.

At the ragged edge of top racers control, not getting what you expect can be deadly. That's why learning how to deal w/both helps riders just "in-general," & dirt riding, can be a plus.

Try it w/caution. Pull in the clutch before coming to a stop. Every brake input is felt by the rider. Straight up & down @ slow speeds it's easy/ok. Again, at top riders high-speed racing corner approach speeds, it's a very, very different thing...

-d

 

[stangmx13]

There is no potential energy. Everything is already moving when it comes time to brake. It's all kinetic, just waiting for u to turn it into heat.

:nerd

 

[Smash Allen]

False neutral unloads the rear and can push the front if you don't adjust brake pressure

 

[afm199]

False neutral unloads the rear and can push the front if you don't adjust brake pressure

I don't think it really pushes, you end up losing your line because you end up losing braking. And once that false neutral happens you never get your line back, it's more like a scuffle to leave the corner with a tatter of dignity intact as you pretend it never happened.

 

[Smash Allen]

I don't think it really pushes, you end up losing your line because you end up losing braking. And once that false neutral happens you never get your line back, it's more like a scuffle to leave the corner with a tatter of dignity intact as you pretend it never happened.

Agreed, but theoretically if you lost the rear brake via false neutral you have less available traction on the front wheel for braking. So if you are maxed already, hitting a false neutral can cause the front to slip, or start to. Right?

Edit: Wrong

 

[afm199]

Agreed, but theoretically if you lost the rear brake via false neutral you have less available traction on the front wheel for braking. So if you are maxed already, hitting a false neutral can cause the front to slip, or start to. Right?

No, you'd have more available traction as the front loaded more, but less braking because you need almost a second to react and brake harder to make up the difference. Thus your turn in is retarded by a second, blowing your line.

As to max traction on the front, almost never happens for most trackday riders in braking. If it does, the rear is six inches in the air.

 

[Smash Allen]

No, you'd have more available traction as the front loaded more, but less braking because you need almost a second to react and brake harder to make up the difference. Thus your turn in is retarded by a second, blowing your line.

As to max traction on the front, almost never happens for most trackday riders in braking. If it does, the rear is six inches in the air.

This is great information, thank you :thumbup:teeth

 

[EastBayDave]

No, you'd have more available traction as the front loaded more, but less braking because you need almost a second to react and brake harder to make up the difference. Thus your turn in is retarded by a second, blowing your line.

As to max traction on the front, almost never happens for most trackday riders in braking. If it does, the rear is six inches in the air.

any way around, when your riding 100% on the ragged edge trying to win a race THERE, there's just no room for error. A momentary unexpected calamity (missing a downshift/catching false neutral instead of expected engine braking) at a critical point is all it took to get him spit off...

It's why some of the more talented racers ride 98/99%, leaving a tiny space/room for error (~1-2%.) So if the unexpected happens, you can save it & not get killed/injured...these are the guys who rarely bail. :x

This is why I respect/am awed by those guys so much, they have virtually nothing to fall back of(in reserve) when trying to win. A couple tents of a sec is the difference between winning & losing, & it takes BIG cajones to do it...:cool

 

[afm199]

any way around, when your riding 100% on the ragged edge trying to win a race THERE, there's just no room for error. A momentary unexpected calamity (missing a downshift/catching false neutral instead of expected engine braking) at a critical point is all it took to get him spit off...

It's why some of the more talented racers ride 98/99%, leaving a tiny space/room for error (~1-2%.) So if the unexpected happens, you can save it & not get killed/injured...these are the guys who rarely bail. :x

This is why I respect/am awed by those guys so much, they have virtually nothing to fall back of(in reserve) when trying to win. A couple tents of a sec is the difference between winning & losing, & it takes BIG cajones to do it...:cool

Yup, when that mistake happens, the very best you can do is stay upright. There's no time to correct the line, find stability again, regain rhythm, or anything else. You're doing well if you stay upright.

 

[EastBayDave]

Yup, when that mistake happens, the very best you can do is stay upright. There's no time to correct the line, find stability again, regain rhythm, or anything else. You're doing well if you stay upright.

Yah know, Guy Martin make a damned good try to save it. He almost (to my bad eyes) made it. He hopped up the curb onto the yard wide uh...(ok let's call it sidewalk cuz I can't think of the word), & tried to ride it out.

Scraped off the bush, then the stone wall, & then steered it back toward the road, only to get the wheels caught on the outside of the curb, & THEN the dirty Honda high-sided him. A valiant effort indeed...:wow

 

[GAJ]

Us mere mortals that don't ride like we're in a road race have a MUCH better chance of recovery than a racer on a tight course like IOM.

I'm just glad Martin survived relatively intact.

Certainly shook him up mentally as would be expected.

 

[afm199]

Us mere mortals that don't ride like we're in a road race have a MUCH better chance of recovery than a racer on a tight course like IOM.

I'm just glad Martin survived relatively intact.

Certainly shook him up mentally as would be expected.

You'd be astounded. I recently saw a guy coming over the crest of the hill to the corkscrew at laguna. Really taking it easy. He fixated on something and went to the brakes. The REAR brake, which he used to leave a nice dark strip of rubber all the way to the gravel, at all of 35 mph. People lose focus.