Handling issue - a question for you suspension gurus

[Syltiz]

A mate of mine asked me to test ride his bike to try diagnose a handling problem. He would not tell me what the bike was doing to see if it was real or just in his mind. It was fairly obvious though in that the bike would not stay leant over, it would take constant countersteering effort to keep the bike tracking the same line through the corner.

I tried a vareity of bends at different speeds and it seems to always be present. Releasing counter-steering pressure on the bar results in the bike sitting up and me re-applying countersteering effort in order to not run wide. This means the bike 'weaves' through a bend and on one high speed corner on the A3 it was actually pretty hairy. The only thing that seems to help is applying some throttle which to me is counter-intuitive as applying throttle should make the bike sit up?

So, not knowing a great deal about suspension myself... i said I would go away and research. Any ideas?

Im also wondering if the forks could be out of alignment? How do you align forks, from the top (i.e. equal length above the yoke) or line up the centre of the spindle holes?

[D-Rider]

Firstly, are the tyre pressures set as per manufacturer's recommendations? I've had a similar feeling with a soft rear tyre.

Increasing rear ride height or dropping the front down the forks a bit would also help turn-in and keep it turned too.

[Syltiz]

Oh yeah.. should have specified. The first thing I did was check the pressures to his manual.

Initial turn in seems ok, its an old 1990 CBR so not the snappiest of turn in, but its keeping it there that seems to be the problem.

[Paulh]

Bent frame?

Knackered head bearings?

Knackered wheel bearings?

Knackered swing arm bearings / bushes?

Old / knackered rear shock / bushes / bearings?

Blown fork seals?

[Paulh]

A The only thing that seems to help is applying some throttle which to me is counter-intuitive as applying throttle should make the bike sit up?

?

Braking usually makes it sit up - applying throttle should help.

[Paulh]

Also worth checking wheel alignment, but on a 1990 bike I would suspect somethings bent rf worn out.

[HowardQ]

You seem to be saying that it is the same on right and left hand bends, is this right?
I have a 1995 CBR1000 and my mate has a 1994 CBR6 and even though they don't turn in too quick, (especially my old lump), they both track steady as a rock once leaned over.
If the frame was bent, I would expect a bit of a difference between right and left handers.
Would look at obvious things like worn wheel bearings, seriously knackered steering head bearings, rear wheel alignment and bent forks as well as possible frame damage.
Assume you've done a basic bounce test on the front and rear suspension, but it would have to be pretty bad to ride like you say.
My old CBR1000 has still on original shocks at 36k or so and is still rock steady.
One final thing, check the tyres for any fuuny wear because if the frame is bent or rear wheel alignment is way out the tyres will be worn in a funny way, possibly stepped blocks etc..

[Samray]

What tyres are fitted?

[Syltiz]

Bent frame?

Knackered head bearings?

Knackered wheel bearings?

Knackered swing arm bearings / bushes?

Old / knackered rear shock / bushes / bearings?

Blown fork seals?

Worth checking then. Would the above really cause the shocking handling that I am feeling?

[Syltiz]

You seem to be saying that it is the same on right and left hand bends, is this right?
I have a 1995 CBR1000 and my mate has a 1994 CBR6 and even though they don't turn in too quick, (especially my old lump), they both track steady as a rock once leaned over.
If the frame was bent, I would expect a bit of a difference between right and left handers.
Would look at obvious things like worn wheel bearings, seriously knackered steering head bearings, rear wheel alignment and bent forks as well as possible frame damage.
Assume you've done a basic bounce test on the front and rear suspension, but it would have to be pretty bad to ride like you say.
My old CBR1000 has still on original shocks at 36k or so and is still rock steady.
One final thing, check the tyres for any fuuny wear because if the frame is bent or rear wheel alignment is way out the tyres will be worn in a funny way, possibly stepped blocks etc..

It handles as above equally poorly on the left and the right. Did the bounce test and the front is probably a little soft and the resulting dive can be felt when braking but the rebound on the front seems quick enough. The back seems fine, maybe slightly too much compression damping.

I will check the above (and the wheel alignment ) this weekend.

[Paulh]

Bent frame?

Knackered head bearings?

Knackered wheel bearings?

Knackered swing arm bearings / bushes?

Old / knackered rear shock / bushes / bearings?

Blown fork seals?

Worth checking then. Would the above really cause the shocking handling that I am feeling?

Depends how much play is there is, but they would all affect the handling.

[Aladinsaneuk]

forget the manual for the tyre pressures - what does the manufacturer reccomend?

the falco manual reccomends pressures that are wrong for most modern tyres - i think, with the exception of michelin you should be running about 36/42...

no idea as i do not know the bike very well, but the front forks are set the same aren't they?

[Syltiz]

forget the manual for the tyre pressures - what does the manufacturer reccomend?

the falco manual reccomends pressures that are wrong for most modern tyres - i think, with the exception of michelin you should be running about 36/42...

no idea as i do not know the bike very well, but the front forks are set the same aren't they?

Well.. there be a can of worms. I did think of this but being nowhere close to the internet I used his manual's specifications. But... surely the difference between tyre manufacturer and bike manufacturer would not cause the severe handling I am feeling? I mean its pretty bad... I am obviously not skilled in assessing handling traits as say a test rider would be, but skipping around one of those small roundabouts (you know, the type the size of a round dinner table) needed me to fight the bike's tendancy to stand up and it felt like the front broke traction briefly. That feeling was also confirmed by my underwear

[Aladinsaneuk]

if so, I would guess at a twisted frame then

[D-Rider]

if so, I would guess at a twisted frame then

Though I'd have thought that would tend to affect things turning one way more than the other.

Tyre pressures, funny tyre wear or maybe notchy or badly adjusted steering head bearings are the things I'd think of first unless it was turning better one way than the other.

Of course on a Falco this is exactly how the standard MEZ3 tyres made the thing feel ......