Emergency stop - rear wheel lock?

[Daveog]

Morning,

Just had a near miss. Had to emergency stop so hit the brakes and changed down into second - rear wheel completely locked up and the gearbox seemed jammed. :smt104

I've stopped suddenly before and the gearbox has struggled to change down (odd bit of clanging) but I must have gone quite some distance today before I had traction again, veering from left to right trying to stop it tumbling either way. Luckily the car didn't turn. Very rarely have I thought, "I'm coming off here" but this was close. In hindsight, I should have tried pulling the clutch in to release the rear wheel...

Anyone else experienced this on an SV?

[Owenski]

MAny many many times, Im quite short so sit over the tank more than over rear. Couple that with weight shifting forwards under heavy breaking the rear has very little imposed load so I found gearing from 3rd to 2nd used to lock the rear quite a bit, a nice little judder would be felt to serve as a reminder to be smoother.

[andrewsmith]

Its normal under emergency braking (or very hard) for the rear to lock going down 3rd to 2nd

As owenski has said just a little reminder

[timwilky]

go back to when you were a learner, it is a fail to change gear etc in an emergency stop. so of course in the real world it doesn't matter. But far better get it into your head to simply brake.

V twins do lock up if you go down under power. so don't.

I know under panic braking you can tend to grip the bars hard, even increasing the revs.

Have a bit of practice on an empty car park to remind yourself how it should be done

[Reeder]

I know under panic braking you can tend to grip the bars hard, even increasing the revs.


Very true, my first emergency stop in the yard on my lessons I accidentally revved the tits off the poor little bike as I held on so tight and accidentally pulled the accelerator at the end!

[Viney]

Dunno. I just usually hit the deck and crash horribly. However, i do get the rear squirming every now and again through over enthusiastic down-changes :)

[Stuuk1]

Used to get this all the time when I first passed and seemed obsessed with changing down at high revs when turbot corners... Don't ask, the back would lock up, I'd **** myself and then everything would be ok again...

I also had a thing for my back brake and almost stuffed the bike up a cars ass when I didn't see she had slowed to turn right and I stuck the rear brake on.

[yorkie_chris]

turbot corners... Don't ask,

I've got to. How the devil did you ride an SV underwater?



Just to be awkward to everyone, it's not a LOCK, it's a SLIDE. As long as you're pointing vaguely in the right direction don't worry about it.

To the OP, it sounds like something MAY be wrong with your gearbox. However the only things to cause a full lock (i.e worn or knackered forks letting you go into 2 gears at once) will completely grenade the 'box.

So go practice changing down in a big hurry. Make sure your timing with blip and shift is alright as the odd clanging is usually someone who shifts down like a size 12 spastic and a maladjusted/crunchy chain.

[Rob969]

I had it on my first trackday I'd only been riding a few months and hadn't mastered the blip on down changes, (still haven't really should probably practise it a bit more) Braking hard for a tight turn i knocked it down a few gears released the clutch and the rear locked just pulled in the clutch to get it rolling again.

[Daveog]

Thanks guys, it's reassuring to know I'm not the only one. I've had the juddering and clanging before where it's tried to get traction and felt halfway between gears but never a full-on, long distance, lock-up.

I shall be practicing heavy braking and avoid changing down - somehow I've rode for three years :confused: and never heard that you shouldn't change down while emergency stopping. Additionally, I'll attempt a little blip of the throttle on the down change in practice.

However, i do get the rear squirming every now and again through over enthusiastic down-changes :) <-- I burst out laughing after reading this quote! :D

Thanks everyone!!

Dave

[yorkie_chris]

Who says you shouldn't change down while emergency stopping?
Edit: except the DSA and since when do they know sh*t all about riding bikes.

If you're stationary in 6th gear how are you going to get around the obstacle, or possibly avoid that truck behind you that was late braking and is about to squish you?

[Viney]

Who says you shouldn't change down while emergency stopping?

If you're stationary in 6th gear how are you going to get around the obstacle, or possibly avoid that truck behind you that was late braking and is about to squish you?Exactly, as long as you know the consequences of your actions when you do these things, the thing is to stop/avoid the obstacle.

[Reeder]

I'm almost 100% certain that during my emergency stops on my MOD 1 I changed from second to first every time when practising and then even on my test?!

[Stuuk1]

I've got to. How the devil did you ride an SV underwater?

Rear wheel locked up and put me in the sea... Or river, wherever turbot's live.

Stupid iPhone auto correct!!

[Paul the 6th]

I shall be practicing heavy braking and avoid changing down - somehow I've rode for three years :confused: and never heard that you shouldn't change down while emergency stopping. Additionally, I'll attempt a little blip of the throttle on the down change in practice.


tbh in the past when something has changed in front of me and caused me to shed a lot of speed I'll happily get hard on the brakes and drop down the gears - but always brakes before gears or you might end up in a situation like you've just found yourself today...

Then the times where it's a code brown emergency stop and there's nothing to think of other than "F**KING STOP YOU BASTA*D!!!!" bring in the front brake and increase pressure *quickly but smoothly* (no yanking, save that for self love time) and introduce the back brake a half second after you're on the fronts..

[Paul the 6th]

Who says you shouldn't change down while emergency stopping?
Edit: except the DSA and since when do they know sh*t all about riding bikes.

If you're stationary in 6th gear how are you going to get around the obstacle, or possibly avoid that truck behind you that was late braking and is about to squish you?


Because obviously when you've done your emergency stop you do the two lifesavers (one over each shoulder) see the truck coming, get off calmly (left foot down, right foot over the bike and down on the tarmac all the while holding the front brake to maintain control of the machine) and push it to the side of the road, while still making observations all around you.

Pretty certain that's the DSA method of "How to avoid being squashed by HGV and/or other large goods vehicles after performing an emergency stop in higher gears, 2007 edition"

[yorkie_chris]

There are 3 things at play to make the wheel slide or become skittish excluding the brakes.

Engine braking
Inertia of the engine
Inertia of the drivetrain

Engine braking is fairly straightforward, there isn't as much as you'd think.

Inertia of the engine is where you fail to match road speed to engine speed with your blip, as you ping the clutch out the engine must immediately speed up from near tickover to some higher rpm which it cannot do immediately, the difference means the rear breaks traction a bit and slides for a while until the engine matches the road speed.

Drivetrain inertia is where you're braking realllly hard, and the drivetrain can't actually slow down fast enough to keep up with the slowing of the wheels and you get the waggly floaty feeling at the back due to the rear wheel still driven forward by this inertia. A bit of a tap of the back brake will knock this on the head.


All of these are made worse by any front braking, which by it's nature unloads the rear, thus reducing traction. Of course if you're REALLY braking with the front then the rear has ZERO traction 'cos you're at the limiting case, the hardest you can possibly brake, about to do a stoppie. You can't slow down ANY HARDER than that. (turn your pockets inside out as air brakes maybe?)
At that limiting case there is nothing to do with the rear except to downshift steadily to keep it somewhere near road speed.


Way I'd interpret the physics of it:
You're better off learning good, smooth downshifting way in advance as part of normal riding. It pays off massively.
When in an emergency apply 100% of concentration to using the front brakes as hard as possible without lock or stoppie. Ignore what the rear is doing. Chances are downshifts will happen automatically, if not no worries, you can't spare any concentration to thinking about them.

[davepreston]

Exactly, as long as you know the consequences of your actions when you do these things, the thing is to stop/avoid the obstacle.
and one day we will learn that its better to do it with the bike still under you, not nessesarlily going over the top of the obstacle alone
:)

[tim8061]

Personally I don't touch the rear brake on emergency stops because I like to stop under control. The engine braking is enough at the rear. YMMV

[Specialone]

I was taught to leave the gears alone cos while practising I was changing down while doing e stops.

When I did my trackday on my sprint, couple of times early on, I was braking into a corner off the long straight and had the rear end squirm and slide a bit cos I was changing down without a big enough blip.

It's much harder to get right on my sprint, it was easy after a while on the sv.

I had my sprints rear end at 45degrees when I locked it up on a greasy road back in October.
Thought the rear was gonna come right round, but let go of the rear brake and re applied then it slid out the other way, in the end I just coasted past the thing I was braking for, it was safer.

[hongman]

Getting blipping on downshifts right is massively gratifying (at least for me). The sound of a perfectly timed blip, the smoothness of it, lurvely. I still miss the timing on an odd blip and it disappoints me somewhat but I've only been riding a few months here and there...

[Daveog]

Thanks everyone - that's great, hopefully with practice I can iron out lock-ups as I'm not a fan after this mornings heart in mouth moment. Thanks Chris for the physics lesson too, now I know what I'm trying to acheive it makes more sense. Just like that time I read an article on the physics of couter-steering - makes it much easier to put into practice.

[nikon70]

stuff changing gear, ignore the clutch, just hit the brakes hard! if you get a lock, release and reapply quickly!
your bike will stall, you will be in the wrong gear but you will have stopped quicker and hopefully not had that crash.

[maxinc]

I always thought that emergency breaking is about stopping as quickly as possible under full control. The way I see it, messing with gear changes in crisis situation, can only steal away from your limited concentration or even worse, destabilise the bike.

[Weirdfish]

If it's a real emergency DON'T touch the clutch or gears, engage the clutch and you disengage the drive to the rear wheel and it becomes much more likely that you will lock the rear wheel when your foot goes onto the rear brake pedal as there is nothing physically driving the wheel around thus it is much more likely to lock. The DSA teach this method for a reason, sure if you are Valentino Rossi F*ck about with the gears all you like but unless you are a true riding God just concentrate on the brakes, believe me getting it right in a sticky situation takes 100% concentration. As for the truck behind you well if he's that close to you that he's likely to flatten you then maybe you should anticipate that by increasing the distance between you and the car in front, don't they say prevention is better than cure? Good luck and practice will always help!:)

[tim8061]

stuff changing gear, ignore the clutch, just hit the brakes hard! if you get a lock, release and reapply quickly! :confused:

If you hit the rear hard you'll lock it up and probably crash, if you grab the front the same could happen IMHO

Get on the front quickly and progressively to load the tyre, rapidly building up to maximum front brake without locking it - something you can practice on a clear road sometime. As for the rear - well maximum front will probably have the rear skipping, so how much rear do you think you can apply?

[Bluefish]

ABS, runs away ;)

[loonytoon]

i had a near miss a couple of months ago where i had to brake fairly hard brought it to a nice controled stop tthen thought to my self a lil close pay attention then check mirrors make sure all was ok behind i then had a brown pants moment to see the car behind hadnt even started to brake here comes an sv sandwich. but training had kicked in even though i had to stop in a hurry i had spotted my escape up a curb only place to go which i did in a hurry an the car slid through where i was an slammed straight into the car that was infront of me due to being on his dam phone.
But after i thought that bad habit of mine on emergency stops had just possibly saved my life. ( bad habit flicking into first as i stop) dont do it intentionaly it just happens.
cheers
Ben

[Holdup]

i do get the rear squirming every now and again through over enthusiastic down-changes :)

I miss that

stupid slipper clutches

:smt072

[nikon70]

ABS, runs away ;)

cheat!

[beabert]

i had a near miss a couple of months ago where i had to brake fairly hard brought it to a nice controled stop tthen thought to my self a lil close pay attention then check mirrors make sure all was ok behind i then had a brown pants moment to see the car behind hadnt even started to brake here comes an sv sandwich. but training had kicked in even though i had to stop in a hurry i had spotted my escape up a curb only place to go which i did in a hurry an the car slid through where i was an slammed straight into the car that was infront of me due to being on his dam phone.
But after i thought that bad habit of mine on emergency stops had just possibly saved my life. ( bad habit flicking into first as i stop) dont do it intentionaly it just happens.
cheers
Ben

Or, step off the bike :smt040

[loonytoon]

ha ha ha, i didnt fancy my bike getting crushed either though hell no im saving me an the bike.

with the blipping the throttle been trying that over the past few days an dam it makes so much diffrence i cant beleive.
hit it right nearly every time after a couple of days not bad going.

[kwak zzr]

- rear wheel completely locked up and the gearbox seemed jammed. :smt104

yea good in'it lol :) i used to to this into tight junctions for fun, after a few times you know its going to happen so it comes of less of a shock - i miss it TBH because little gixer wont do it :(

[Daveog]

ha ha ha, i didnt fancy my bike getting crushed either though hell no im saving me an the bike.

with the blipping the throttle been trying that over the past few days an dam it makes so much diffrence i cant beleive.
hit it right nearly every time after a couple of days not bad going.

So the blipping - is that when the clutch is dipped/disengaged? Did try it last week, sort of just before pulling the clutch in, with great results and much faster changes.

Discovered a nail on Saturday so just put the rear wheel back on, give it a try in the morning.

[hongman]

Yeah. You are essentially matching engine speed with road speed so the downshift is much smoother, as you greatly reduce that lurch forward

[Specialone]

Yeah. You are essentially matching engine speed with road speed so the downshift is much smoother, as you greatly reduce that lurch forward
That lessens though if you ease the clutch out ;)

[yorkie_chris]

increases clutch wear too. Blip the throttle. Also means no nasty clacking sounds from the gearbox. Also one less thing to think about.

[beabert]

I find myself blipping the sodding thing even when its not needed now :smt040 in fact i might ride the day not blipping to see if i'm even doing it right anymore.

[Daveog]

Think I'm getting the hang of it slowly, much improved gearchanges - thanks guys!!