losing the back under front braking...sometimes?

[Val]

Hello guys,

I wonder if there is something wrong with my front brake. Under hard front brake braking (not emergency hard) my back end starts twitching.

I mean even it is not that hard, way way softer then doing stoppies for example. My back wheel is on the ground but I feel I am losing it.

Happened few times in the last week. Once was I needed to shave off some speed to get in a queue I was overtaking and the back started to go hard left and right. I was thinking that is because I was close to the centre paint line maybe the paint was the reason.

Then it hapenned few times in the middle of the lane too under hard front brake braking (not emergency hard), even not that hard lets say ambitious front brake braking.

Any ideas? I don't have ABS. Never happened to me with the Fazer. I know MT09 is lighter, still doesn't feels right. Obviously I have adjusted my riding, but modern bikes are supposed to brake very well. That reminds me 30 years ago with the drum brakes. Forward planing was the key 

Anyhow not happy to have fast bike that can't stop well. What is wrong?

[Fazerider]

The lighter the bike the more significant the rider’s weight becomes… the centre of gravity may well have moved upward as a result.
What is the state of tyres?
Is the suspension set up for you?
If the front spring rate or preload is a bit low for your weight or if the fork oil is too light then you’ll get more dive… more dive transfers more weight to the front and takes it off the rear.

[Val]

The lighter the bike the more significant the rider’s weight becomes… the centre of gravity may well have moved upward as a result.
What is the state of tyres?
Is the suspension set up for you?
If the front spring rate or preload is a bit low for your weight or if the fork oil is too light then you’ll get more dive… more dive transfers more weight to the front and takes it off the rear.

True I am heavy 109kg. Tyres look great. The suspension is set up for me, but there are not much options here, means it is jacked up almost on max. When I brake there is not big dive.

[tommyardin]

Well I am no mechanic, you say that the front does not dive excessively when braking, I think I would be looking at the arse end rather than the front, swing arm bearings, suspension linkage bearings the shocker itself maybe top or bottom shock mounting, under hard front braking the back will always go lighter but it should not cause the bike to skip and hack about.
Hope you get that sorted cos it does not inspire confidence when riding.


Just had a thought might just be worth checking wheel alignment and or true-ness of the wheel when spinning.
Sounds like clutching at straws I know but just some times it works.   

[celticbiker]

You'll get this if you have too much rebound damping.
Also where do you place your weight when braking?
On a modern bike it should go through your knees to the tank and down to the pegs, there should be virtually no weight carried through your arms to the bars as this upsets the centre of gravity.

[tommyardin]

Hi Val, your MT09 is a 2015 yes? Have you had the bike from new? What sort of mileage has it done? And has it allways run wild at the back under reasonably heavy front braking? Or is it a new thing that's just started? If it is a new thing what have you done differently or what has changed (fallen off it hit a kerb hard) Lots of questions I know but a bit of background history is always good.
I bought an Ambasador 250cc (Villiers two-stroke twin) years ago that had really weird handling characteristics, it was like riding a ruptured camel (not that I have any evindence that a ruptured camel handles poorly) but it transpired that it had been in a front end shunt and although had been repaired well, the steering head tube on the frame was bent out of alinement, slightly to one side and the handling was awful. Looking at the bike from the front when on the centre stand you could actually see that this single frame downtube did not run centrally between the fork legs.
Back wheel bearings maybe? Under power the chain pull will keep the wheel in alinement, slam the throttle shut and maybe the wheel can slap about, it would not take much to upset the dynamics.

[pilninggas]

The rear shock on the MT09 has had appalling reviews and feedback from owners. Your problem sounds symptomatic of the shock having very poor damping characteristics.

Unfortunately the fix seems to be aftermarket shock fitment. The MT forums will shed more light./

[locksmith]

Just a thought, are you changing down as you do this?, the rear will lock up quite easily due to the strong engine braking.

[Dave48]

The rear shock on the MT09 has had appalling reviews and feedback from owners. Your problem sounds symptomatic of the shock having very poor damping characteristics.

Unfortunately the fix seems to be aftermarket shock fitment. The MT forums will shed more light./

The original MT09 OEM shock was,according to many owners on the relevant forums here & in US, simply not up to the job. How many miles has the bike done now? Anything over 5000 miles will result in poor performance. I had a 2015 MT07 from new & the shock was nothing to write home about albeit I weigh 70 kilos without my riding kit on.
I believe the MT09 Tracer has a better shock fitted than the naked MT09. The one on my 2016 Tracer700 is better than the one on my 2015 MT07.


Speaking to the guys who supplied my Wilbers aftermarket shock for my FZS 600(53000 miles) I understand that even some BMW & Triumph owners are binning their OEm shocks for something that actually works properly(Cost cutting by manufacturers to increase profit/reduce build cost).
 All this presupposes no other problems exist with bearings & tyres. Let us know the cure!

[Tmation]

Being a fat bloke myself I can tell you exactly what is happening to your bike.


Your suspension is budget and not designed for your weight, when you sit on the bike you will use up all the sag.


As soon as you brake all the weight will go to the front and the arse end will go light and wander around. (the poor rear suspension doesn't help here.)


If you can't afford to have the suspension rebuilt to suit your weight, at least get springs rated to suit you and take advice on oil weight and amount.


I always have my bike suspension rebuilt and set up for me, K Tech front and rear on my Gen 1 1000, serviced every 3 or 4 years by MCT.


You could also try applying the rear brake a bit first, the bike should then stay a bit flatter when braking hard.

[Val]

thank you all guys I will try to get the bike checked by suspension specialist and will keep you updated...

[slimwilly]

What's a rear brake ? , I race on track and are guilty of not using the rear brake at ALL,  , I must start to try it, I am a lightweight and the front does fine, mind have not had a wet race yet,,will use it then

[fazersharp]

Being a fat bloke myself I can tell you exactly what is happening to your bike.


Your suspension is budget and not designed for your weight, when you sit on the bike you will use up all the sag.

If you can't afford to have the suspension rebuilt to suit your weight, at least get springs rated to suit you and take advice on oil weight and amount.

Wouldn't it just be cheaper all round to eat less pies

[darrsi]

Being a fat bloke myself I can tell you exactly what is happening to your bike.


Your suspension is budget and not designed for your weight, when you sit on the bike you will use up all the sag.

If you can't afford to have the suspension rebuilt to suit your weight, at least get springs rated to suit you and take advice on oil weight and amount.

Wouldn't it just be cheaper all round to eat less pies

Wash your mouth out young man!!

[Frosties]

Being a fat bloke myself I can tell you exactly what is happening to your bike.


Your suspension is budget and not designed for your weight, when you sit on the bike you will use up all the sag.

If you can't afford to have the suspension rebuilt to suit your weight, at least get springs rated to suit you and take advice on oil weight and amount.

Wouldn't it just be cheaper all round to eat less pies

[Val]

Just a thought, are you changing down as you do this?, the rear will lock up quite easily due to the strong engine braking.

Nope I rarely do that. If I change down usually I don't use the brake until last few meter before stopping, because the engine braking is very strong on MT09.

That happens only when I need the brake - something happens and I need to use the front brake in a sharpish way.

Update today I was overtaking few cars with 70ish or more and I was in the opposite lane while doing that. The lane was straight and free more then 500-600 meters ahead. A car has popped up from a driveway in front of me in the lane. Luckily there was enough distance. The front brake was pulsing hard at the lever when braking from speed and the whole front was jumping like going through speed bumps.

Any ideas?

[slappy]

Are you sure that it is not the ABS kicking in? The lever will pulse when it happens, or could be warped discs, front wheel bearings or headstock bearings.

[darrsi]

Just a thought, are you changing down as you do this?, the rear will lock up quite easily due to the strong engine braking.

Nope I rarely do that. If I change down usually I don't use the brake until last few meter before stopping, because the engine braking is very strong on MT09.

That happens only when I need the brake - something happens and I need to use the front brake in a sharpish way.

Update today I was overtaking few cars with 70ish or more and I was in the opposite lane while doing that. The lane was straight and free more then 500-600 meters ahead. A car has popped up from a driveway in front of me in the lane. Luckily there was enough distance. The front brake was pulsing hard at the lever when braking from speed and the whole front was jumping like going through speed bumps.

Any ideas?

I had what i used to describe as a pulsing/juddering sensation on my bike for months which i couldn't figure out which was doing my head in, and the only thing i had left to try was changing the braided brake lines that were on the bike and they turned out to be the culprit.
The previous owner never really looked after the bike and they were either most likely damaged or possibly just faulty, but once changed to a new set everything was sorted.
Before that i'd more or less replaced the whole front end of the bike spending a lot of time and money in the process, ie: head bearings, pads, discs, forks, but because they were aftermarket brake lines, and braided, i just never thought they would've been the solution.
Dunno what lines you have on your bike, but i'd imagine there's an even higher chance of this possibility if they're not braided.


I'm not saying this is your problem, but it's certainly an option to consider and not rule out as i did.

[fazersharp]

Just a thought, are you changing down as you do this?, the rear will lock up quite easily due to the strong engine braking.

Nope I rarely do that. If I change down usually I don't use the brake until last few meter before stopping, because the engine braking is very strong on MT09.

Just a side note- I always blip the throttle when changing down to counter the engine braking, unless I am just pootling around slowly   

[locksmith]

Just a thought, are you changing down as you do this?, the rear will lock up quite easily due to the strong engine braking.

Nope I rarely do that. If I change down usually I don't use the brake until last few meter before stopping, because the engine braking is very strong on MT09.

That happens only when I need the brake - something happens and I need to use the front brake in a sharpish way.

Update today I was overtaking few cars with 70ish or more and I was in the opposite lane while doing that. The lane was straight and free more then 500-600 meters ahead. A car has popped up from a driveway in front of me in the lane. Luckily there was enough distance. The front brake was pulsing hard at the lever when braking from speed and the whole front was jumping like going through speed bumps.

Any ideas?

I'd put some money on warped disc.

[darrsi]

Just a thought, are you changing down as you do this?, the rear will lock up quite easily due to the strong engine braking.

Nope I rarely do that. If I change down usually I don't use the brake until last few meter before stopping, because the engine braking is very strong on MT09.

That happens only when I need the brake - something happens and I need to use the front brake in a sharpish way.

Update today I was overtaking few cars with 70ish or more and I was in the opposite lane while doing that. The lane was straight and free more then 500-600 meters ahead. A car has popped up from a driveway in front of me in the lane. Luckily there was enough distance. The front brake was pulsing hard at the lever when braking from speed and the whole front was jumping like going through speed bumps.

Any ideas?

I'd put some money on warped disc.

It's a common misconception to blame a warped disc, but as i found out the hard way it's not always the case even if all the signs point in that direction.
The trouble is, you have to spend a fortune on discs to find out if it is them or not. They're not as easy to check as people make out unless they're completely shot.
If you consider warped discs then you have to back track and see if there's a reason why they would warp, like a sticking piston for example.

[locksmith]

My reason for saying that being that in a car I had a terrible juddering when braking heavily from speed, yet normal braking at normal speeds was unaffected. Turned out the discs were badly worn and replacing them was the cure. Now I assume am MT, a couple of years old won't have worn discs, so I mention warped. Possibly just slightly untrue just enough to give the heavy braking symptoms.

[darrsi]

My reason for saying that being that in a car I had a terrible juddering when braking heavily from speed, yet normal braking at normal speeds was unaffected. Turned out the discs were badly worn and replacing them was the cure. Now I assume am MT, a couple of years old won't have worn discs, so I mention warped. Possibly just slightly untrue just enough to give the heavy braking symptoms.

We're talking about semi floating discs though, it would take some savage race type maniac braking to warp them through heat for example.
Sticking piston certainly could cause issues but i would've though Val would've picked up on that earlier.
He actually described perfectly what i was getting before, as if you are braking on a cobbled road.