Front end wobble

Robbknoll

Bikes been laid up since late December and only back on the road the last few days. Under deceleration, when not holding the bars, the front end starts to wobble after a couple of seconds. Quick checks on the internet quote tyres and tyre pressure, both I've checked and after inflating to spec the problem is better but not fixed.

The problem wasn't there before it was laid up and over the past 2 years I've never had this problem. Anyone have any experience with this before I bring it to a mechanic? Bike is a 00 gsf600. Thanks lads.

CJhaughey

Robbknoll wrote: »

Bikes been laid up since late December and only back on the road the last few days. Under deceleration, when not holding the bars, the front end starts to wobble after a couple of seconds. Quick checks on the internet quote tyres and tyre pressure, both I've checked and after inflating to spec the problem is better but not fixed.

The problem wasn't there before it was laid up and over the past 2 years I've never had this problem. Anyone have any experience with this before I bring it to a mechanic? Bike is a 00 gsf600. Thanks lads.

Is there a flat spot on your tyre?
Fork seals OK and not leaking?
Cold weather makes forks stiff and old oil may be past its best, consider changing fork oil for fresh stuff?
Rear shock linkage not seized from lack of use, this can make a bike very nervous as the front compresses and the steering angle changes.
Push down on the saddle and see if it compresses through the stroke.
Steering head bearings ok and not seized up?
Prop the bike up and see if the forks swing freely and don't bind in one spot.

Robbknoll

CJhaughey wrote: »

Is there a flat spot on your tyre?
Fork seals OK and not leaking?
Cold weather makes forks stiff and old oil may be past its best, consider changing fork oil for fresh stuff?
Rear shock linkage not seized from lack of use, this can make a bike very nervous as the front compresses and the steering angle changes.
Push down on the saddle and see if it compresses through the stroke.
Steering head bearings ok and not seized up?
Prop the bike up and see if the forks swing freely and don't bind in one spot.

Not that ive noticed, my commute is quite straight so tyre is worn more in the centre (but with same tyre all was grant a month ago).
Fork seals are good and havent noticed a stiffness in them either. Couldnt hurt to change the oil though regardless.
Didnt notice anything out the ordinary with the rear shock when putting on the luggage but will test it out.
And ill check the steering head bearing and the swing of the forks later.

Thanks a bunch.

CJhaughey

Robbknoll wrote: »

Not that ive noticed, my commute is quite straight so tyre is worn more in the centre (but with same tyre all was grant a month ago).

I don't mean radially I mean if the bike was parked for a while the part of the tyre that contacted the ground and was holding the weight of the bike can deform and get flattened.

Robbknoll

CJhaughey wrote: »

I don't mean radially I mean if the bike was parked for a while the part of the tyre that contacted the ground and was holding the weight of the bike can deform and get flattened.

Ah i get ya. Well doesnt matter now anyway, had a quick check when i got home and found out i picked up quite a big metal passenger in the front tyre, wasn't there before i left. We'll be seeing if a new tyre sorts it ha.

Hotblack Desiato

I posted a youtube video about this before.

Bikes have a natural tendency to wobble the front end at certain speeds with your hands off the bars, why would you be riding with no hands on the bars anyway?

https://www.youtube.com/watch?v=z3OQTU-kE2s

That is at 2 mins in the video. Not really dangerous (except that riding with your hands off the bars makes you slower to react to any hazards) and should be less likely to happen on modern bikes with radial tyres and decent suspension


High speed weave though is at 3 mins in, looks pretty scary, a lot of the 70s bikes shown were prone to it at 80-ish MPH depending on the rider weight and the state of the tyres. Shouldn't happen on modern bikes unless there is something very wrong with tyres or suspension, a stiff frame and good damping means the bike can be designed to be stable right up to its maximum speed. A fair few riders would have been killed by fighting the weave back in the day, the solution isn't to brake or steer but just put your head on the tank to put a bit more weight over the front. A modern bike especially anything sporty is going to have a lot more front biased weight distribution than a 70s UJM anyway.

Can't speak for cruisers though. The larger engined ones can hit pretty high speeds (if you can hang on) and I've heard of a couple of cases of riders coming off in unexplained crashes on fast straight roads which might have been weave.