Highside and How To Avoid Them. - Chicagoland Sportbikes
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post #1 of 16 (permalink) Old 05-05-2008, 02:52 AM Thread Starter
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Highside and How To Avoid Them.

After witnessing one today I thought it might be good to discuss this topic and bring some new riders up to speed on this. The following text has been copied from Wikipedia for starters. I really wish some of you would chime in with you knowledge and experiences. This may help some of the newer (and even the older) riders here to avoid what I saw today.

For visual reference I offer the following video:



----------

A highsider or highside is a type of motorcycle accident which is caused by a rear wheel gaining traction when it is not facing in the direction of travel. For a highsider to take place, the rear wheel must first lose traction and drift out of the line travel of the motorcycle. The initial traction loss may be caused by a rear locked wheel due to excessive braking or by applying too much throttle when exiting a corner.

Highside accidents are typically caused by over-acceleration or braking in corners, but are also a result of locking the rear brake in an emergency stop while traveling straight at high speeds, such as on a highway. Chopper style motorcycles with the front brakes removed are especially prone to highsider accidents.


Avoiding a highsider

When braking, use both front and rear brakes on the motorcycle, and avoid locking the rear brake.

When exiting a corner toward a straight direction of travel, do not apply sudden acceleration inputs until the motorcycle returns to a near upright position. Lower gear selection and sharp acceleration inputs increase the likelihood of a rear tire abruptly losing traction on acceleration. Instead smoothly apply throttle as the bike becomes more upright and traction increases. If a riders experiences a rear tire slide under acceleration the best thing to do is slowly roll-on the throttle. If one reduces throttle while the bike is sliding you may regain traction suddenly resulting in the highsider. Tire warmers can increase tire grip for track days and racing. Riding conservatively until the silica in rubber compound and friction generate heat within the tire can also improve grip. Many highside incidents result from aggressive riding on tires that have not yet achieved a temperature suitable for optimal grip. Many tire manufactures add silica to the rubber compound to generate heat as the tire flexes. Temperatures of 170 F (77 C) are common for race ready tires.


Technical explanation

Forces occurring between the motorcycle and the road (such as accelerating, decelerating and steering) are transmitted by friction occurring in the contact patch. There is a limited amount of force the contact patch can transmit before the tire begins to lose contact and slide.

When going through a curve on a motorcycle, the rider has to apply force on the motorcycle in order to make it alter its direction of travel. This centripetal force is transferred from the road to the motorcycle through the contact patch and is directed at a right angle to the path of travel. Applying too much throttle will increase the stress in the contact patch, because now there is an additional force which also has to be transmitted through the contact patch, this time parallel to the direction of travel. This additional amount of force may cause the tire to slide. It is during this slide that reflex will cause the rider to rapidly shut the throttle and cause the rear tire to lock. This same condition can be caused by applying too much rear brake while cornering. If braking is applied equally to both tires, the rear tire will begin to slide first because braking causes a weight shift towards the front tire, improving its contact with the road while lessening the rear tire's grip.

Other reasons for the tire losing grip may be too little tire profile and/or bad road conditions like gravel, water, snow etc.

Once a tire slips in a curve, it will move outwards under the motorcycle and cause the cycle to lay down in the direction the rider is already leaning to counteract the centrifugal force and lead to a lowsider.

The usual maneuver to get a locked tire to stop slipping is to make it turn again by reducing the amount of force applied by the brakes (thus reducing the amount of force acting on the contact patch and reestablishing the grip on the road). However, this is critical at this stage. If the tire suddenly regains traction while the motorcycle is moving sideways, this is similar to hitting an obstacle in the road: the tire will stop its sideways movement causing the motorcycle to suddenly jerk into an upright position (and beyond). This movement can easily cause the rider to be thrown off.

The name derives from the side of the motorcycle that the rider will separate from. If forcibly thrown over the bike, the rider is said to have dismounted on the high side.

Riders are usually advised to do a lowsider rather than a highsider if neither can be avoided. The highsider has the additional disadvantage of the rider often being catapulted into the air by the sudden jerking motion of the motorbike and the increased possibility of the motorbike sliding behind the rider and threatening to crush him.

Because highsider accidents are so much more deadly than lowside accidents, the Motorcycle Safety Foundation recommends that if a rider locks the rear brake, it should be kept locked until the motorcycle comes to a stop. If necessary, locking the front brake to deliberately cause a lowsider is recommended.

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Last edited by SloRoll; 05-05-2008 at 02:04 PM.
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post #2 of 16 (permalink) Old 05-05-2008, 03:56 AM
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Simple. two things:

You can turn the throttle in a corner if and when:
1) You can see the exit
2) You can take away lean angle

Roll on smoothly as you exit the corner, drop the head and push the bike away from you. The lowest point your head should be in the turn is at the exit, outside arm resting on the tank.

Thought to avoid: Wow, the view is nice from up here.

===========
Great Quote - One would think that the Secret Service was smart enough to get serviced secretly.

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post #3 of 16 (permalink) Old 05-05-2008, 08:44 AM
 
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If you are starting into a highside you should roll onto the throttle more? Wouldn't that make you definately lowside?

Can someone explain for the newb? I've only experienced a bigtime slide once in Wisconsin on gravel. I had both tires go and it slid me all the way into the wrongside lane. Sqrly was right behind me got a good view of me shitting myself. lol Lucky to keep it upright and even luckier that nobody was coming. First lesson in saving it for the track because road conditions are always unsure on the street.
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post #4 of 16 (permalink) Old 05-05-2008, 08:46 AM
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Listen to Wink, he speaks the truth.

The only other thing I would add:

It is important to "set" the rear tire before going full throttle. A smooth initial throttle roll on will set weight of the rear wheel and then with the decreased lean angle (that Wink spoke of) causing a larger contact patch on the rear tire, you should be in a good position to roll the throttle to the stop.

Avoid abruptness, it will hurt you.

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post #5 of 16 (permalink) Old 05-05-2008, 08:55 AM
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Quote:
Originally Posted by FullThrottleZX View Post
If you are starting into a highside you should roll onto the throttle more? Wouldn't that make you definately lowside?

Can someone explain for the newb? I've only experienced a bigtime slide once in Wisconsin on gravel. I had both tires go and it slid me all the way into the wrongside lane. Sqrly was right behind me got a good view of me shitting myself. lol Lucky to keep it upright and even luckier that nobody was coming. First lesson in saving it for the track because road conditions are always unsure on the street.
Yesterday at Putnam coming out of turn 4, I was driving hard off the apex on completely worn out tires right after I dropped 2 teeth off the rear sprocket. All of a sudden I heard the engine start to really rev up fast...too fast. This was my first indication that I had lit up the rear tire.

I didn't highside and I didn't lowside. Here's why.

1. I had my body position way off the inside the bike, causing the bike to be at minimal lean. This caused the rear end to step out slowly enough to give me time to respond. If the bike would have been at more of a lean, it could easily have stepped out too far too quickly and the whole thing would have been over before I even knew what happened. Body position is IMPORTANT.

2. I held the throttle exactly where it was and gingerly pushed the bike as upright as I could get it while very very very slowly easing off the throttle.

The key here is that I was not at max lean angle. This gave me time to react.

I got lucky on this one. But I also put myself in the best position to "get lucky". Highsides hurt. I hate them.

Hope that help a little.

Ron Hix
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post #6 of 16 (permalink) Old 05-05-2008, 08:57 AM
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Wink and Ron =

Take heed to their advice and you may never ever have to experience the world of suckiness that is a highside

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post #7 of 16 (permalink) Old 05-05-2008, 09:21 AM
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Ron nailed the keys. I too had the rear step out a few times yesterday as I was getting used to a new bike. Nice gradual rear slides, plenty of time to react and gently (Very) gently roll-off a fraction of the throttle until it hooks back up.

Note: If the rear brakes loose and you close the throttle, instant highside.

And FWIW above, NO, we are not suggesting actions that will cause a low side, BUT, if you ever have a choice between a high-side and a low-side, lay the bike down. It is FAR better for you and fro the bike. Just pull the bike down and lean into the pavement (BTW - Gear helps here)

I had to lay the bike down last year once when riding with Ron on VIR South to avoid hitting him (It wasn't his fault, we had no where to go after the rider in front of us screwed up). It was amazingly easy to make the choice to lay it down rather than hitting Ron, as well as it was very easy and gentle to low-side the bike, I just pulled it down to the ground. No damage to me or the bike, more importantly, no damage to Ron.

===========
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post #8 of 16 (permalink) Old 05-05-2008, 09:38 AM
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Quote:
Originally Posted by Wink View Post
Ron nailed the keys. I too had the rear step out a few times yesterday as I was getting used to a new bike. Nice gradual rear slides, plenty of time to react and gently (Very) gently roll-off a fraction of the throttle until it hooks back up.

Note: If the rear brakes loose and you close the throttle, instant highside.

And FWIW above, NO, we are not suggesting actions that will cause a low side, BUT, if you ever have a choice between a high-side and a low-side, lay the bike down. It is FAR better for you and fro the bike. Just pull the bike down and lean into the pavement (BTW - Gear helps here)

I had to lay the bike down last year once when riding with Ron on VIR South to avoid hitting him (It wasn't his fault, we had no where to go after the rider in front of us screwed up). It was amazingly easy to make the choice to lay it down rather than hitting Ron, as well as it was very easy and gentle to low-side the bike, I just pulled it down to the ground. No damage to me or the bike, more importantly, no damage to Ron.
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post #9 of 16 (permalink) Old 05-05-2008, 09:44 AM
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+2 on Wink's and Ron's comments. Running out there with Ron this weekend I was spinning up the rear out of a few corners as I was getting on the throttle hard and early (to keep up with Ron's cheater bike ) But like Ron mentioned, was hanging way off the bike while pushing it up. As I felt the rear regaining traction, I was able to continue to apply more throttle. The key is to listen to that rear and keep your cool. Being smooth on the controls goes a long way...

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post #10 of 16 (permalink) Old 05-05-2008, 09:47 AM
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T7 @ BHF I highsided. It hurt.

The cause: too many heat cycles on the tires. Lesson learned.

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post #11 of 16 (permalink) Old 05-05-2008, 09:55 AM
 
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Thanks guys I appreciate the info. Keeps me rubber side down!
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post #12 of 16 (permalink) Old 05-05-2008, 11:46 AM

 
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This is why it's important to be smooth. Load the rear, roll into the throttle gradually. It's also super important to be relaxed on the bike. If your tense and "hit" the throttle, the rear steps out and or spins up quickly. Your already tense and nervous at this point. When you feel the bike move, you immediately react, and make another abrupt change to correct what you've caused. This upsets the chassis, and everything goes away quick.

As Ron stated, if your smooth and load the tire, your relaxed, you notice the rear has begun to spin. Because your relaxed and smooth, this feeling is subtle and not a shocking wake up call. As such you don't react instantly and can make small changes to deal with the tire spin.

If your smooth in the throttle application and approaching the tires limits in small amounts as your skill increases, the first few times the rear loses traction, it will probably be replanted by the time you realize it was even spinning.

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post #13 of 16 (permalink) Old 05-05-2008, 11:59 AM
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^^^^ Good info from the masters. Thanks

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post #14 of 16 (permalink) Old 05-05-2008, 01:02 PM
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Good info guys.

Yeah, that last bit from the article about if you know you're heading into a high side, lock the fronts to force a low-side.. didn't know about that. Same thing I guess as laying the bike down, but good to know.

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post #15 of 16 (permalink) Old 05-05-2008, 04:48 PM
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It does look like it took about 1.5 secs between tire stating to slide and the rider in the air shot. During that time, one needs to recognize situation and apply corrective action - which in simplest case is to lock the front. Both steps will consume the time and sometimes are simply beyond abilities of the human to react to. The point is - sh**t happens. Top level GP riders highside too.

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post #16 of 16 (permalink) Old 05-05-2008, 06:29 PM
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Quote:
Originally Posted by Chills View Post
T7 @ BHF I highsided. It hurt.

The cause: too many heat cycles on the tires. Lesson learned.

Ditto but mine was in the rain. Pulled a newb move and chopped the throttle. And it is amaizing how fast 275 lbs can be thrown over the top.

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