Bikesure_adrianflux

Severe tank slapper

wasang

wasang

Registered
Joined
Oct 7, 2025
Messages
20
Location
Southampton
Bike
M900ie
Hi fellow Monster owners. Ref. 2008 Monster S4RS. Had a very near miss the other day when overtaking a car that decided to turn right without any indication. Nice one!
Apart from soiling my pants I did manage to stop just before the turn but had to brake so hard it locked the front wheel. In doing so the steering went into a uncontrollable violent tank slapper which nearly sent me hitting the road.
Has anyone experienced this extreme wobble when braking at max on a Monster? I've checked the discs on there is next to zero run out ( using a dial gauge) and brake shoes are well within the wear limit. I have a DP damper on the handlebars which seems to be working and oil levels in the forks are at spec. There is also no play in the headstock bearings. The bike is built using top spec parts (Ohlins front end, Brembo brakes ect) so I would not expect this to happen.
I don't want to experience this wobble again so any ideas would be much appreciated. Anything else I should be checking for?
Thanks
 
I've never had that happen on my S4RS so can't offer any advice.I did have all the Ohlins serviced and set up correctly last winter and there were several things that required attention,fork seals were slightly leaking,wrong grade and amount of fork oil,one or two bushes needed changing.Made a big difference and the bike is much nicer to ride now.Maybe the locked front wheel hit something in the road that set the tank slapper off?
Good luck
Kimbo
 
Well you get what you deserve young man, as they say.

It wouldn't have mattered what bike it was and how well prepared it was. The incident was down to poor riding skills and very poor roadcraft.

What on earth were you thinking overtaking approaching a right hand tuning? There is signage to help you with this and you also have a couple of good eyes. (I hope anyway.)
It shouldn't have surprised you that a vehicle might want to turn right there. Even if it had not turned, I wonder if you would have also been surprised if a vehicle had emerged from the turning whilst happily checking over their shoulder for traffic coming down from their right?

You say you braked so hard you locked the wheel. In fact what you did was brake too hard too soon.
An emergency stop should be executed by starting to brake with moderate pressure until the forks are fully compressed. Continue to increase the lever pressure until the tyre contact patch is at it's largest, then you can brake hard. It's likely that the rear wheel will leave the ground if you're doing it right, but do not use the rear brake, the still spinning rear wheel will stabilise the bike until it drops back onto the tarmac.

Try any of the roadcraft courses the Police run in various counties. There are also machine handling courses dealing with various aspects of machine handling.
The police will be able to teach you how to read the road and the other will teach you how to operate your bike properly.

Lucky you got away with it this time, but at least you now have some time to practice... 😉
 
Odd that it did it under braking, I've only ever experienced any wobbles at speed, usually under acceleration though my Monster has never misbehaved, despite the steering feeling a tad 'light' at higher speeds.

Maybe a mismatch between front/rear ride height?

The only bike of mine that has ever done such a thing is my old Guzzi that got me into a violent tankslapper whilst crossing diagonal painted hatching. I managed to hang on though it was close and the front brake pads shook themselves into the calipers so much that I had to prime the lever a few times before they would work.
 
I was an IAM senior observer for a number of years and I always taught riders to never, never overtake at a junction. People (car drivers) do all sorts of stupid things at junctions. I think you had a lucky escape there wasang, could have been a lot worse.

All riders must take at least half the blame in an accident (see Mr Gazza's response above) but take all the pain.
 
The only time I experienced a tank slapper I was misbehaving a bit..
On my way to work one evening riding my S4rt I approached a T junction and I am about to turn left, the road is easy to see around and carry enough speed in second gear so as not to come to a complete stop in safety, the road I an turning onto has a gentle uphill grade, I would regularly wind the throttle on into an easy wheelie in second and third, but this time as gravity brings the front wheel down gently it must have landed slightly crossed and started a violent tank slapper, I tried to stop it by holding the bars as tight as I could but it made it way worse, the face of the driver coming towards me on the other side of the road was abject fear looking at my situation so using a combination of skill and pure luck I completely relaxed my grip, barely touching the bars and very gently accelerated which instantly stopped the shenanigans, all of this excitement only lasted perhaps 15 or 20 seconds but it felt like a lifetime when it was happening. It certainly tightened my sphincter, all self inflicted, but lessons were learned...
 
Thanks for all of your replies. After 40+ years of riding I've never overtaken at a RH junction but a lapse of concentration for a moment could have ended in complete disaster I know. Brought home to me the irrational way drivers can sometimes behave and re-awoken my survival instincts. My mindset is to think that "All car drivers are out to kill you". Bit extreme I know but it has kept me safe so far, touch wood.
As for the tank slapper, still a little puzzled by it but it may have been me slamming on the front brake too violently as suggested as the Brembo brakes are ultra efficient. It only takes a moderate amount of pressure to lock the wheel. Will definitely take care when braking hard next time.
Thanks again for all of your advice.(y)
 
I wouldn't go quite so far as to say that all car drivers are out to kill you, but I do believe that maybe one in fifty are fairly incompetent (maybe that's a tad generous) and a further one in fifty might be fine most of the time but could easily have a lapse of concentration.
This means that one in every couple of dozen are a potential danger and you will come across one of these approximately every mile you travel. Perhaps less.
Since you have no way of knowing in advance which drivers these are then effectively yes, every driver out there should be seen as a potential hazard.
It amounts to the same thing in the end, but perhaps from a slightly different, more tolerant and maybe more accurate mindset.
Which can only be a good thing.

As to the tankslapper, I would imagine that your instinct would have been to turn the bars (even just slightly) away from the hazard as you slammed on the brakes.
This could have been the starting point of the slapper which would have then been amplified and sustained by the weight transfer to the front wheel.
Maybe.
Its all kinda instantaneous and therefore difficult to analyse.

I empathise with your momentary lapse of concentration.
Its one thing to know of the dangers but another to be on top of your game 100% of the time.
I've lapsed myself. Not particularly often I hope, but still enough times to have come seriously unstuck if luck had not been on my side.
Its easy to become complacent.
I noticed this very much when I had a break from motorcycling and drove a car for a few years.
I found myself falling into exactly the same traps that I used to criticise car drivers for in the days when bikes were my only form of transport, eg gazing too long at the scenery, being distracted by the antics of other road users or just generally being less alive to what was going on around me.
And of course, as I suggested earlier, all the other drivers out there are subjected to the same.

Every now and then you get a jolt from a near miss and this can serve to reawaken your instincts.
Glad you got away with it this time.
 
Assuming they're all out to get you, isn't a bad thing. My most concentrated period of close calls, was definitely while despatching round London, cabs u-turning, being run over by pedestrians, stationary cars opening doors to stop my progress, ect. But probably the closest was down to me, I was just mentally somewhere else and suddenly found myself halfway across a busy cross road (4lane in both directions) with traffic moving at 90 degrees to me in both directions. Stopped in the middle and waited for the lights to change.
 
I've experienced extreme juddering when bottoming out front forks (Monster 620) at Donington, combine that with public road surface as opposed to the smooth tarmac approaching Goddard's hairpin and you've got a potential tankslapper.
 
I had a massive tank slapper once riding a 400vvc Suzuki Bandit when I accelerated to over take a car on a two way street. To this day I feel that it was probably due to the front end being light, crossing a white line diagonally and possibly a bit of bad luck.

Scary experience that I wouldn't wish on my worst enemy
 
Only time it happened to me on a monster was on track at Oulton, accelerating out of Park corner which is fast and has a ridge on the exit which unloaded the front wheel, violent tank slapper ensued which I managed to bring under control, only to have another fright a moment later when I hit the brakes for the next corner and there weren't any (pads shaken loose in the callipers) and I had to frantically pump the brake.
 
"All car drivers are out to kill you" is a mindset that will definitely aid longevity. A tank slapper induced by hard "front" braking can be caused by several things, misaligned frame/fork geometry is one.
 
my S4 likes a bit of a front end wobble approaching a tanks slapper at speeds above 130mph ,,, but never on the brakes .. had a massive tankslapper many years ago 1993 on a yamaha FZR1000 at over 120mph on the A2 in Kent braking made it worse giving more beans up to 150+ cured the problem ??? needless to say a brown trouser event .....oh and the cause was a slow puncture in front tyre ...
 
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