High speed weave

[Fuzzy]

Really a question for those with a raised rear end, whether by using shorter links/jack up kits or longer shocks. Have any of you noticed a weave at high speed? And how much have you raised by?

I have a longer shock, about 5mm longer which I think equals about 25mm at the seat, and get noticeable instability at approx 70 to 80mph even when set-up with less preload to get more sag.

I know there are a lot variables such as rider weight, aerodynamics etc but just wondered what people's experiences were 

[noggythenog]

Mine is jacked up at least 25mm as i went for 130mm dog bones, Im about 17 stone plus with all my kit on
I havent had any issues, did a 200 miler recently at about 70-80 ish and the bike felt spot on & i feel pretty confident with it.
the rest of my suspension is standard but i did have to come a few clicks down on the rear shock from max as it felt a bit dodgy at max.

[Motorbreath]

Mine is raised too, 6mm shorter dogbones and 3mm longer shock. Swapped wider front wheel and 170/60 rear tyre too. No problem.

It weaves when not enough rear preload. Try stiffening it.

Sometimes it is wizardry. My bike had a handlebar wobble at about 70km/h with different Pirelli tyres. Bridgestone and Dunlop solved it.

[Fuzzy]

It weaves when not enough rear preload. Try stiffening it.

That's what I thought to begin with but the opposite is true. It is far better behaved with less preload - I think this is due to the fact that it sags more creating a less aggressive geometry and a more equal weight distribution. Two up with luggage it was spot on (with the preload adjusted of course) which suggest there's not enough weight at the back when solo. I've heard so many people having a 25mm lift or even more like noggythenog with no problems.

I'm only 11ish stone geared up so I think it might be a lack of weight causing a problem. I've stiffened up the front a bit already to compensate and that hasn't helped much. Has stiffer springs in there too. I think the only solution is to drop the rear ride height a bit again. Shame as it handles a lot nicer than standard under 80ish or when two up. Maybe I should just more pies  :b


Quite an interesting video (although rather old) about wobble and weave presented by none other than Murray Walker. Starts from about 4mins10secs.

Murray Walker talks about Wobble and Weave on Motorbikes

[Motorbreath]

Poorly aerodynamic luggage can cause it too. Do you have a topbox? Many people have to remove them from their bikes.

Hayabusa's subframes weren't made of aluminum anymore when some were broken carrying topboxes at high speed.

[noggythenog]

Test

[noggythenog]

Could it just be different characteristics i.e.-is it just the bike constantly trying to turn in?.Im nit sure thats even possible but my bike is more on a knife edge & turns in very quickly, almost too quickly so just thinking its maybe more difficult to keep it in a true straight line and feels like its weaving (turning in) but im only a newbie so thats prob a load o bollocks :\ , just a theory.


For info ive got my rear shock adjusted half way between max and min at present which many would think was a bit too soft for a big lump like me & although going up to max made it feel more sporty it felt too unstable mid corner whilst hitting imperfections & undulations.


On the front adjustors I've wound out to the 4th ring just showing, it feels good but I'm gonna try some fine tuning.

[Fuzzy]

No it's not the luggage because it behaves more with panniers and topbox or either on their own.

I have a MRA screen thats quite large. I suppose that could be contributing factor but I think the main issue is the rear ride height. Tyres are PR3s in good condition so can't think they're a problem. The head bearing + all wheel bearings are okay. Besides the only thing that changed before I got the weaving was the shock.

Could it just be different characteristics i.e.-is it just the bike constantly trying to turn in?.Im nit sure thats even possible but my bike is more on a knife edge & turns in very quickly, almost too quickly so just thinking its maybe more difficult to keep it in a true straight line and feels like its weaving (turning in) but im only a newbie so thats prob a load o bollocks :\ , just a theory.

That's right and is the main effect of shorter dogbones and resulting steeper fork angle. I know the standard length is 140mm whilst I'm pretty sure the + 25mm bones are 135mm. If you've got 130mm bones, I'm guessing that'll equate to around +50mm? That's quite a bit of difference and is likely to be the cause of any twitchiness. Sounds like we're in the same boat. I think I'll have to get the shock changed back to normal length.

So the moral of the story is to bear in mind your weight when choosing how much you jack up by. Bugger.

[noggythenog]

Yep you could be on to something with the weight thing fuzzy & i suppose it's all down to what folk want.Im after more sporty handling so im happy with it but some people may find that it just doesnt suit their type of riding much.
if you havent seen the other recent posts about jacking up then heres a couple of links:-
firstly this was a recent link
http://foc-u.co.uk/index.php/topic,7924.0.html
and then within that link i copied in my original question and subsequent discussion here:-
http://foc-u.co.uk/index.php/topic,4000.25.html

[fazed600]

Also worth checking front and rear wheel bearings, even if just to discount it as a cause.

[darrsi]

I have a topbox and get the wobblies at high speed, but not with a passenger on the back, as it changes the weight and aerodynamics of the bike!
Much worse with a head on wind when the front lifts up as well.
Passengers tend to not like that for some reason?  :rolleyes

[Fuzzy]

Its a bit of a minefield it seems....

At least with shorter links you can swap them out fairly easily. Its a shame as it definitely handles better otherwise and I like sitting higher up. I did a 600mile round trip with luggage and a pillion and it was positively a pleasure to ride.

Maybe I'll test the waters in the for sale section to see if anybody heavier than me would be interested as I think it'd work pretty well if you're not a weeny like me. Its the oem shock rebuilt with the lower collar flipped upside down resulting in no more than 5mm increased length.

The thing that baffles me is that it's not even a major lift. I'm a short arse and even had my seat lowered previously and although I can feel a rise I can still get both feet down so it can't be that much of a difference.
Amazing what a few mm difference can do.