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post #1 of 9 (permalink) Old 05-19-2010, 01:01 PM Thread Starter
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Exclamation Danger of using your engine to slow down

And I realize in some circumstances it is o.k. to slow down using the engine, by shifting down. But in most cases this is the more dangerous way to slow down.

The reason is that, by downshifting to slow down, you are depending on the traction of the ground/pavement to force the rear wheel to keep turning, albeit at a slowing rate. If the surface traction is not sufficient to keep the wheel turning against the force of the engine (that is trying to slow the wheel down) the engine power will exceed the road resistance, and the rear wheel will nearly completely stop.

In my case, I shifted from 3rd to 2nd gear, just a few feet before the steel storm drain grate. That grate had about zero traction for my knobby tires. When I went over the storm drain, the rear tire slowed to probably around 5 mph, but my motorcycle was still travelling at about 25 mph. When I reached the other side of the storm drain my rear tire met the far greater friction of the road -- still going nearly 25 mph, but with my rear tire rotating at about 5 mph. This was nearly a dead stop for my motorcycle, and it fell over about 4 feet on the other side of the storm drain, and I went over the front tire.

For more information on my incident, see this:

Do not engine-break
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post #2 of 9 (permalink) Old 05-19-2010, 01:12 PM
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Any type of braking on a slick surface can cause you to lose control.Glad your ok,safe riding!
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post #3 of 9 (permalink) Old 05-19-2010, 01:15 PM Thread Starter
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Quote:
Originally Posted by rustydog View Post
Any type of braking on a slick surface can cause you to lose control.Glad your ok,safe riding!
That is right. I guess I wouldn't have hit the brakes because of the slick surface, but I wasn't thinking about NOT shifting down. A newby (like I was at the time) might not realize the power forcing the rear wheel to slow when down-shifting.
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post #4 of 9 (permalink) Old 05-19-2010, 01:24 PM
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I think when people talk about engine brake they meant to roll the throttle back (release the throttle?), not to downshift without pulling the clutch in (I definitely don't do this unless my clutch's broken)

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post #5 of 9 (permalink) Old 05-19-2010, 02:29 PM Thread Starter
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Quote:
Originally Posted by YamahaFan View Post
I think when people talk about engine brake they meant to roll the throttle back (release the throttle?), not to downshift without pulling the clutch in (I definitely don't do this unless my clutch's broken)
I actually pull in the clutch, shift down, then release the clutch. It really slows the MC down!
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post #6 of 9 (permalink) Old 05-19-2010, 02:42 PM
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I engine brake ALL the time, saves on brake pads! =P I never downshift with blipping the throttle though
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post #7 of 9 (permalink) Old 05-19-2010, 03:57 PM
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Quote:
Originally Posted by dewaine View Post
The reason is that, by downshifting to slow down, you are depending on the traction of the ground/pavement to force the rear wheel to keep turning, albeit at a slowing rate. If the surface traction is not sufficient to keep the wheel turning against the force of the engine (that is trying to slow the wheel down) the engine power will exceed the road resistance, and the rear wheel will nearly completely stop.

Do not engine-break
I engine brake all the time. I think the moral of this story, as well as your other nearly identical post is to be aware of the road conditions you are on. Metal railroad crossings, painted lines, manhole covers, especially when wet are going to have far less traction. Engine braking isn't really that dangerous, being un aware of road conditions is.

Last edited by internationalballer; 05-19-2010 at 04:03 PM.
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post #8 of 9 (permalink) Old 05-19-2010, 04:46 PM
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As to the OP his quote on the link he provided sums it up:

"I agree, now that I think about it -- it would have been just as bad had I hit the brakes. The main problem in my case was I was distracted by a car backing out of a driveway, and I forgot about the storm drain. But I have been putting a lot more thought into the issue down-shifting."

It's really not the down shifting to slow down that was dangerous, but the braking circumstances at the time. This does give us all something to think about though.
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post #9 of 9 (permalink) Old 05-19-2010, 08:18 PM
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Quote:
Originally Posted by internationalballer View Post
I engine brake all the time. I think the moral of this story, as well as your other nearly identical post is to be aware of the road conditions you are on. Metal railroad crossings, painted lines, manhole covers, especially when wet are going to have far less traction. Engine braking isn't really that dangerous, being un aware of road conditions is.
Same here!
I NEVER do NOT use the engine for braking.
(Even on ice. Just in a higher gear for the condition.)

Always be aware of what you are riding ON.

There was another post not too long ago where the poster said that
"he saw the fresh painted lines that were not there the day before",
and STILL slipped on it!

The clue was there!

He still turned on it!

Bottom line: pay attention and stay upright.

Eric
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