Steering - Wobbly D6!

[Gobbie]

Hi,
I've noticed that if I pretty much let go of the handlebars the front wheel/bars develop a wobble which quickly gets fairly severe. Grab the grips again and I'm ok! I'm not planning to ride around no-hands but I'd like to sort it.

I've read some threads suggesting wheel bearings, tyre, and head bearings. I've tried to move the front wheel sideways and it feels ok, to my acknowledgeable hands. Nothing feels wrong in the steering either.....again, to me. Can someone tell me how to test which could be causing it?

Also, my bike has aftermarket bar-end weights....the coloured alloy type. Could this be part of the problem? This is my first big bike so I'm not at all familiar with the effect these weights have. I'm guessing I'd be better of with the original ones. Any thoughts?

Cheers.......

[bobh]

Hi Gobbie,

You don't say what sort of speed it happens at. Also whether you have any luggage (particularly a heavy topbox) or are carrying a passenger.

I shouldn't have thought the bar end weights would cause this problem. They are mainly there to damp out engine vibrations.

Three things to try:

1. Check that the wheels (particularly the front one) are running true, and that there are no flat spots or bulges on the tyres.

2. Check that the tyres (again, mainly the front) are balanced. You should be able to get an idea on this if you either pull the pads back so they're not rubbing on the disc(s) or just detach the calipers and hang them up out of the way, als detach the speedo cable. Spin the wheel and see if it always stops in the same place. Spinning the wheel should also reveal if there's any roughness in the wheel bearings.

3. Check the wheel alignment, both visually and with a plank or piece of string. At the same time, check as far as you can for any evidence of the frame or forks being bent or out of line. If the forks were bent back even slightly it can alter the steering geometry and cause this.

Good luck - Bob

[darren]

what he said

[CD]

At about 40mph the front will naturally flutter slightly. Its normal and holding the 'bars should stop it immediately. 70's bikes do it around 35mph. Modern sports bikes about 60mph. Divvies 40 to 45mph. Its caused by the self-centering action of the front wheel geometry and the wheel gyro effect.

But knotchy steering head bearings can make the normal front wheel flutter into a full on wobble. As already said, dodgy swing arm bearings and wheel bearings also wont help.

[amorti]

D6's are horrible for it by all accounts including mine.

Things that don't help:
Avon tyres, they're too pointy.
Soggy forks (typical of D6 particularly older model single disc / skinny forks)
loading the top box / pillion seat.
notchy steering bearings (mine are recent)

Thing is, it'll never throw you off, tis not that strong, so just ride around it or stop taking your hands off the bars

[CD]

All bikes do it to some extent - they are in effect a small articulated vehicle with a substantial percentage of the total weight ahead of the steering hinge. If its allowed to flutter the rider's arms will damp out the effect. Lock it up with a steering damper and under some conditions the whole frame can start wobbling causing a proper weave.

[gitsy]

had the same problem try putting new oil in forks it seems to have cured mine

[neilmud Lord Protector]

Tyre pressures my D900 would do it at about 40 mph when tyres at correct pressure it was hardly noticeable it was a good way to let me know when pressure needed checking.

Neil

[CD]

Mine's the same though it was far worse before I changed the steering head bearings. I guess I just got used to it until the MOT failed on knotchy head bearings.

Strangely enough I've had a seriously stepped Conti Road Attack with some tread on the centreline and worn out shoulders yet the 40mph wiggle was no worse than with a new tyre.

I've no idea if the worn head bearings contributed to the tread going stepped.

Edit headwind on M-way today with top box and at speed = naughty it would weave/wobble a couple of times when changing lanes. But the effect never threatened to get out of shape.
It reminded me of how it was with the old head bearings - really not nice. Instead of doing a wiggle the whole frame would flex and it got worse as I slowed down.

[nero]

Greetings, I currently own single disc D600 (1996') and have a horrible wobble at about 90mph.I can release handlebars up to 60mph and there is no wobble at all,but after 90 it gets ruff.When I have my girlfriend on bike it does 110 mph with no wobble at all.New Michelin Pilot Activ tyres, new main bearings, new wheel bearing,new oil in forks....any ideas?

[General Gman]

If it does it at speed, it's usually wheel balance.If you're anywhere near Slough, pop round and I'll balance the front for you

[CD]

Nero, yours sounds like tight or knotchy steering head bearings. I always say this for speed wobbles but so far every bike I've had that does this - the steering is the cause.

Top boxes and luggage make it worse but the root is usually in the steering.