What would result in more stability?

[cowboyz]

When my 98 zx9r gets to go faster than 200k/hr the front drifts along the road. Lifting slightly but not off the ground but enough to make the front very very light. Makes it so you are not sure where striaght is and at those speeds it kind helps to know. I am not talking about tank slappers or anything that dramatic but it would be nicer to be more settled.

So the question being which will offer more support for helping the front to behave itself more at high speed?

1. Changing front springs.

2. steering damper.

3. something else?

Might have a vote on it just for interest.

[spookytooth]

would have figured you are getting wind lift so changing springs wouldnt help alot

[Jantar]

would have figured you are getting wind lift so changing springs wouldnt help alot

+1

Definitely sounds aerodynamic, not suspension related.

[cowboyz]

so I should put a big arse aerofoil on the front?


Or accept that it is going to drift and put a steering damper on to smooth things out?

[dhunt]

When my 98 zx9r gets to go faster than 200k/hr the front drifts along the road. Lifting slightly but not off the ground but enough to make the front very very light. Makes it so you are not sure where striaght is and at those speeds it kind helps to know. I am not talking about tank slappers or anything that dramatic but it would be nicer to be more settled.

So the question being which will offer more support for helping the front to behave itself more at high speed?

1. Changing front springs.

2. steering damper.

3. something else?

Might have a vote on it just for interest.

3. Eat more pies

Is it when you are accelerating only or even when you are at a constant speed?

You could try leaning forward a bit more and see if that helps? That way there is more weight on the front and you'll be more aerodynamic.

[cowboyz]

Under excessive acceleration the ground and my front wheel are not really close friends. That is fine. I dont mind that.

But I was having a drag the other day and got to 220ish and just couldnt go any faster with confidence cause the front of the bike just would not settle. Every little bump in the road hoists the front an inch or so off the ground. (ok. maybe half and inch..)

[FROSTY:Me]

My first thought was get ya suspension sorted--Front and rear
I'd give Glen Williams or Saslex a yell -both those guys raced ZX9Rs
Glen is codgy old racer I think

[sugilite:Me]

The front end of ZX9R's do indeed get light under hard acceleration in the 1st 3 gears, sometimes 4th as well.
A steering dampener will see off those pesky bar oscillations.

[slowpoke]

My first thought was get ya suspension sorted--Front and rear
I'd give Glen Williams or Saslex a yell -both those guys raced ZX9Rs
Glen is codgy old racer I think

Yep, I'd be checking basic suspension setup before I went reaching for my wallet. Those 9's are supposed to be one of the more stable bikes at speed.

[FROSTY:Me]

Sorry Sugi--dunno why I said saslex

[Robert Taylor]

When my 98 zx9r gets to go faster than 200k/hr the front drifts along the road. Lifting slightly but not off the ground but enough to make the front very very light. Makes it so you are not sure where striaght is and at those speeds it kind helps to know. I am not talking about tank slappers or anything that dramatic but it would be nicer to be more settled.

So the question being which will offer more support for helping the front to behave itself more at high speed?

1. Changing front springs.

2. steering damper.

3. something else?

Might have a vote on it just for interest.

Sorry but I dont think a vote is an appropriate way to nut this out.

You need to elaborate with more detail as the suggestions thus far given ( whilst well intentioned ) make assumptions that are too generalised.

What is your personal height and weight?

Is the bike absolutely stock standard with respect to suspension components, springing , settings etc?

Are the forks set to the standard installed position in the triple clamps?

What tyres are fitted and what are the pressures set to?

How many kilometres has the bike done and have the suspension components been serviced within the total distance travelled?

Has the bike ever been invloved in an accident i.e is it straight?

Have you checked wheel alignment?

On receipt of your answers I will be able to give you some suggestions re set-up / repairs etc that should at minimum minimise this problem. These bikes are noted for instability but it shouldnt be at a level that is a danger to you and other road users sharing the same piece of road at the same time.

Steering dampers are a great safety device and I reckon every bike should have one but they should never be a band aid for serious handling / stability issues.

[Drew]

Bloody vague description of what's actually happening alright.

Is the bike weaving at pace? I ask, because at 220+k's, there are fuck all bikes out there, that are still generating enough accelleration to lift the wheel.

Particularly a couple hundred kg's of ZX9.

Hitting a bump at that speed, will still only lift the wheel for a tiny fraction of a second, and although it might travell up to a meter like that, shouldn't give a nervous feeling.

I'd suggest answering RT's questions as best you know, and let the guru give his advice.

My partener got her ZX9 up to 274k's at the sprints, and it was like being on a rail she said.

Her older model (YOUR ACTUAL BIKE) did 269k's (on the actual timer), in the wet and still felt good. Super stable, even with the bumps.
She wonders if you have altered the suspension??????? as she had it well set up for speed.

STABLE bikes, and your one isn't, means there's an issue in my opinion.

[cowboyz]

Sorry but I dont think a vote is an appropriate way to nut this out.

You need to elaborate with more detail as the suggestions thus far given ( whilst well intentioned ) make assumptions that are too generalised.

What is your personal height and weight?

Is the bike absolutely stock standard with respect to suspension components, springing , settings etc?

Are the forks set to the standard installed position in the triple clamps?

What tyres are fitted and what are the pressures set to?

How many kilometres has the bike done and have the suspension components been serviced within the total distance travelled?

Has the bike ever been invloved in an accident i.e is it straight?

Have you checked wheel alignment?

On receipt of your answers I will be able to give you some suggestions re set-up / repairs etc that should at minimum minimise this problem. These bikes are noted for instability but it shouldnt be at a level that is a danger to you and other road users sharing the same piece of road at the same time.

Steering dampers are a great safety device and I reckon every bike should have one but they should never be a band aid for serious handling / stability issues.

righto . answers as follows.

I am 5 11 and 91kg

Drew will be able to answer if the bike Is standard. I am not sure to be honest. The only obvious change I can see is the arrow can on it. There is plastic welding down the sides of the fairings which looks like its been down but the bike is striaght.

Not long after I brought it I went for a ride with suglite. He sat on it and spent less than five minutes adjusting the front suspension which made the bike a heap more stable than it was cornering. Suglite was a great help and the adjustments he made were on the side of the road for a few minutes and he never actually rode the bike. (Because this is in written word and meanings can be misinterpreted I would like to make it clear to anyone who might suggest suglites setup was wrong/misleading then that is not the case. It was a quick tweak on the side of the road and the guy obviously knows what he is doing)

Forks/triple clamp appear to be standard position.

rear tyre is a michellin road attack 2 and the front is a metz roadtec. Tyre pressures are recommended (42? I think from memory)

Bike has now done 85000km. I brought it in the low 70s in march. I havent serviced the shocks.

I havent checked the wheel alignment.

On a personal note. I come from a "bike touring" background riding a gsx600F where I have clocked up my share of ks at close to, if over (not by much) road legal speeds. I recall having a conversation with DMTD when I was up in Kaitaia and commenting I had done 2700km that in 3 days and not exceeded 130km/hr. He was very surprised.
Since upgrading to the 9 and having the handling of a real sports bike and power to boot I have slowlt increased my speeds and have started riding a fair bit quicker than I used to. (power is addictive) Broadening into the >200km range I am not feeling like I am out of control but as I am sure you are aware, things start happening a shit load quicker. Maybe the bike is doing what it is surposed to be doing at those speeds. I dont feel like I am out of control. Just really really light in the front. That is why I was thinking steering damper to stiffen the steering up. It is not bouncing all over the road. In fact it is more than capable of staying in one half of my lane. It holds a striaght line even with the front wheel skipping.

[cowboyz]

Bloody vague description of what's actually happening alright.

hope last post clears that up a little.........

Is the bike weaving at pace? I ask, because at 220+k's, there are fuck all bikes out there, that are still generating enough accelleration to lift the wheel.
Not weaving. Just skipping or bouncing over the bumps in the road. Still riding striaght though.
Particularly a couple hundred kg's of ZX9.

Hitting a bump at that speed, will still only lift the wheel for a tiny fraction of a second, and although it might travell up to a meter like that, shouldn't give a nervous feeling.

I guess that depends how brave you are?

I'd suggest answering RT's questions as best you know, and let the guru give his advice.

My partener got her ZX9 up to 274k's at the sprints, and it was like being on a rail she said.

Her older model (YOUR ACTUAL BIKE) did 269k's (on the actual timer), in the wet and still felt good. Super stable, even with the bumps.

good to know. Being as you have already seen how fast this thing can go maybe next year at the sprints you will be able to see how slow this thing can go.
She wonders if you have altered the suspension??????? as she had it well set up for speed.

STABLE bikes, and your one isn't, means there's an issue in my opinion.

replied in line . hope it works.

[TDC]

righto . answers as follows.

I am 5 11 and 91kg

Not long after I brought it I went for a ride with suglite. He sat on it and spent less than five minutes adjusting the front suspension which made the bike a heap more stable than it was cornering. Suglite was a great help and the adjustments he made were on the side of the road for a few minutes and he never actually rode the bike. (Because this is in written word and meanings can be misinterpreted I would like to make it clear to anyone who might suggest suglites setup was wrong/misleading then that is not the case. It was a quick tweak on the side of the road and the guy obviously knows what he is doing)

All of the following assumes that the bike is straight and the suspension components are in good / serviceable condition.

Not wanting to knock anybody's abilities but reading through this thread there are a couple of things that have changed it would seem from a previously stable bike.

1/ The weight of the rider has gone up!

2/ The front suspension has been adjusted!

One of the most common things that riders get wrong is they mis-adjust their front suspension (well actually both ends) by way of applying way too much rebound damping.

If this has been done this will cause the front end to dynamically ride lower in the stroke than it will sit at rest. This is due to the time it takes for the forks to extend after each compression cycle being increased (by way of too much rebound damping). This mans after successive compression cycles (read several a second) the forks will ratchet (or pack) down as they have not had enough time to extend between compression cycles. This results in the bike sitting lower in the front at speed and the suspension compliance degrading as a function of how much the front end is packing down.

This has several undesirable effects firstly it makes the front sit lower which effectively decreases the steering head angle and the trail (both critical to stability). Additionally it makes the response of the forks abrupt for the size of the bump encountered. This could quite conceivably add up to an unstable bike at speed.

If the front is already sitting low because of the increase of rider weight (assuming it was not adjusted to compensate), given the packing down effect described above the bike could be beginning to enter the region of front suspension travel that is dominated be the effects of the internal hydralic bump stop, if this is the case due to the aggressive action of the same it will make for a very frightening ride at speed. And given the history and symptoms would be my guess assuming all of the parts of the bike are still serviceable.

This suggestion is just that a suggestion after reading the information posted with a whole bunch of assumptions, but if I were a betting man its where my money would be.

The ZX9 has soft springs from stock, at your advertised weight and height at a minimum replacement fork springs should be on your shopping list!