Unstable under high speed braking

[honda1944]

Tonight while following a truck at a safe distance (thankfully) on an outside lane of a four-lane westbound interstate, an ambulance passed in the innermost lane.  I moved over and started to slow down but the truck in front of me was apparently startled by the ambulance as it got alongside of him and slammed on his brakes requiring me to do the same.  I hit front and rear brakes and pulled in the clutch simultaneously from about 65 mph.  I started to slow normally but then experienced what felt like the rear end sliding back and forth several times.  Happened very fast and all I remember doing was letting off on the front brake and then reapplying several times.  Don't know what I did with the rear brake, but I think I kept even pressure.  Within a few seconds the bike regained stability and I regained control, moved onto the shoulder to avoid the back of the truck.  Slowed to about 35 and then re-entered traffic flow wondering what just happened.  I think I am somewhat educated on braking and weight transfer dynamics and have been riding for 15 years, but I really don't know what I did wrong -- too aggressive on front or rear?  Something wrong mechanically with the bike?  It all happened so fast that I just can't replay every step in my mind and I just drove away thankful that I was still upright and alive.  I really did allow enough distance and was anticipating having to slow drastically and/or pull over for the ambulance which I saw when it was still well in back of me and three lanes inside of me.  At 70 mph on a major interstate, no one (except the truck or some one in front of him) even slowed down, let alone pulled over to the right and stop.  If anyone has had a similar experience I would appreciate some advice on what to do differently if there is a next time.  Thanks.

[sandy]

The only thing I do different is I don't pull in the clutch when stopping. My reflexes usually have me downshifting as rapidly as my hands and foot can make the changes. You didn't say how many miles are on your bike. It could be worn out rear shock bushings (every 10-15K miles) or swingarm bearings. Maybe low tire pressure. My guess is shock bushings.

[Chrisj CMA]

Bottom line....you got it under control and stopped safely, so I cant say you did anyting wrong.  None of us were there and it just wouldnt be right to try to judge.  If nothing at all is wrong with your bike, I would say dont pull in the clutch so fast....let the compression of the engine help slow you and I think that adds stability (the syntrifical force) and drive pressure to the wheels.  Secondly.  I would sooner have thought to release the back brake and reapply and maybe just feather the fronts if letting off on the rear didnt help........again this is if there is no problem.  

If you had low tire pressure, worn shocks/bushings, bad wheel bearings or maybe just caught a worse than you thought wind draft off that truck, or strange road conditions.......all these things change what you experience and some you have no control over

[MP]

+1 on sandys reply.  Keep downshifting as you stop.  Otherwise, you wind up sitting still in fifth gear.  The car/truck coming BEHIND you may not be able to get stopped.  Watch your mirrors as you stop.

You may NEED to get it in first, and get the h**l out of there asap.  If you are sitting in fifth, you are in trouble!

Wobble is hard to say.  May just have been locking up the rear.  Easy to do.  Replacing shock bushings, or checking them, is a good idea.

MP

[clintsdivco]

I got too aggressive with my rear brake recently when someone unexpectedly pulled into my lane at 60 mph, locking up the rear and it set the bike into a wobble.  I knew it locked up as I heard the tire screeching. It recovered as soon as I let off of the rear brake.  I was trying to grab the front brake too but when I grabbed for it my fingers hit the back of the lever and delayed getting onto the front brakes so I knew for sure what caused the wobbling.

Clint

[sandy]

Several years ago, a friend showed me how to drive with my thumb and pointy finger. The other three I keep resting on the brake lever. In a panic stop, your reflexes will cuase you to tense up your hand. With fingers already on the lever, you squeeze the front brake in a reflex instead of having to start a hand motion to get the job done. This habit saved me from rear ending a car when I was distracted once. Without the reflex starting the braking, I'd never have stopped in time.

I got too aggressive with my rear brake recently when someone unexpectedly pulled into my lane at 60 mph, locking up the rear and it set the bike into a wobble.  I knew it locked up as I heard the tire screeching. It recovered as soon as I let off of the rear brake.  I was trying to grab the front brake too but when I grabbed for it my fingers hit the back of the lever and delayed getting onto the front brakes so I knew for sure what caused the wobbling.

Clint

[roboto65]

I know I will cause a stir but your rear locked up !!!   80 percent of your braking power comes from the front brake not the rear.  
When you hit the rear brake all your forward momentum is just that going forward. The rear brake is behind all the weight and when you apply just the rear brake all the Valks weight is dragging the tire along and the weight is all forward still.

Now if we apply the front brake we all know what happens the bike compresses the front forks loading them up and puts downward pressure on the front tire giving it more traction. It takes more to lock up the front tire than it does the rear.
 
Now locking up the rear is not as bad as locking up the front I will give you that but used right the front will stop you faster than the rear and when you use both you will stop faster but you are should be applying more front than the rear.

It all boils down to practice practice and more practice to save your hide when some cage is either yaking on phone and pulls out in front of you or just gets stupid and pulls in front of you.

Ok stepping off the box let the hail storm begin  

[Dogg]

whatever you did, you did fine. you didnt hit hte truck and you are here to tell us about it. congrats. but too much rear braking can seriously get the bike moving around and wobbling. otherwise. good job!! 

[clintsdivco]

Several years ago, a friend showed me how to drive with my thumb and pointy finger. The other three I keep resting on the brake lever. In a panic stop, your reflexes will cuase you to tense up your hand. With fingers already on the lever, you squeeze the front brake in a reflex instead of having to start a hand motion to get the job done. This habit saved me from rear ending a car when I was distracted once. Without the reflex starting the braking, I'd never have stopped in time.

That is good advise Sandy.  I started that on my own after that incident. I never ride in traffic anymore without having several fingers on the front brake.  All physics about the front brakes doesn't mean a thing when you screw up an miss applying the front brakes.

Every mistake I have made I try and learn from.

Clint

[R J]

Tonight while following a truck at a safe distance (thankfully) on an outside lane of a four-lane westbound interstate, an ambulance passed in the innermost lane.  I moved over and started to slow down but the truck in front of me was apparently startled by the ambulance as it got alongside of him and slammed on his brakes requiring me to do the same.  I hit front and rear brakes and pulled in the clutch simultaneously from about 65 mph.  I started to slow normally but then experienced what felt like the rear end sliding back and forth several times.  Happened very fast and all I remember doing was letting off on the front brake and then reapplying several times.  Don't know what I did with the rear brake, but I think I kept even pressure.  Within a few seconds the bike regained stability and I regained control, moved onto the shoulder to avoid the back of the truck.  Slowed to about 35 and then re-entered traffic flow wondering what just happened.  I think I am somewhat educated on braking and weight transfer dynamics and have been riding for 15 years, but I really don't know what I did wrong -- too aggressive on front or rear?  Something wrong mechanically with the bike?  It all happened so fast that I just can't replay every step in my mind and I just drove away thankful that I was still upright and alive.  I really did allow enough distance and was anticipating having to slow drastically and/or pull over for the ambulance which I saw when it was still well in back of me and three lanes inside of me.  At 70 mph on a major interstate, no one (except the truck or some one in front of him) even slowed down, let alone pulled over to the right and stop.  If anyone has had a similar experience I would appreciate some advice on what to do differently if there is a next time.  Thanks.

Are you sure that isn't a warped rotor........          Rear tire should not slip and slide out on an I/State Road that is heavily traveled..     Not enough sand on the surface, unless you were in the middle track where all the oil droppings are at......    Then you will get a radical slip and slide reaction.......