Downhill speed wobble

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Bonniebird

moped
Whilst touring on my Bonnie SE (09) last week I experienced downhill speed wobble on a number of occasions.
My panniers were evenly packed & not over weighted, only very light items in my top box.
I checked my tyre pressures the week before I set off & adjusted them for extra weight the day before.
After the 1st wobble I adjusted my suspension to the hardest setting, which did improve the handling a lot, but going downhill on big sweepers at about 85mph I still experienced the wobble!!
My tyres are Bridgestone BT 45's and totally confidence inspiring & I've only done 1000 miles on them, so I know it's not them.
Is this a general Bonneville thing?? I really don't want to slow my riding down or buy a different bike.
Has anyone else had this problem & solved it???....perhaps a different suspension kit???
PLEASE HELP,
Laura
 
koifarm

koifarm

Hooligan
Wobblies

Don't discount the possibility of a bad tire...it's been known to happen....
Also, it may need another balance job on both tires...remember, a human being balanced the tire (let alone made it) and we all know human beings are fallible at times....you may want to run it back to the dealer or a good nearby bike shop and have the tires balanced again and at the same time inspect the tire to see if there is anything visibly wrong with it.
New tires aren't necessarily perfect.
 
Texas94fs

Texas94fs

Hooligan
With a smaller front diameter wheel you lose high speed stability but increase turn in. The new bonnies come with a 17 inch front wheel. The older thruxtons bonnies and scrams have a have a high speed instability that you describe that became noticeable when pushing the bike and riding hard. I'd imagine with the smaller front wheel its easier to find that instability. I'd suggest getting the wheels (both) rebalanced and checked and make sure they are aligned properly. If they check out then its just a general rule of thumb that you will get a little wobble under those conditions that can be remedied by a steering dampner. The damper will also help save you shoudl you encounter a tank slapper type situation due to road conditions or rider error. Also having your suspension properly adjusted for your weight and type of riding can help.
 
C

Chris in NC

Street Tracker
Bonniebird said:
...perhaps a different suspension kit???
PLEASE HELP, Laura
Click to expand...

Laura, Before I spent a bunch of quid on new suspension parts, I'd do a couple things. Double check your tire pressure - front and rear, check the setting on both rear shocks - make sure they're the same, and where you want them to be. Lastly, have your Triumph shop check the tension on your neck bearings.

If that doesn't fix your problem, consider adding a Norman Hyde steering dampener. That should take care of any front end wobble.
 
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GT rideaholic

GT rideaholic

Scooter
Laura I just rode from Florida to Colorado and back a few weeks ago on my 09 T100.. I had recently installed a set of Hepco Becker saddlebags on the bike.. Above 85mph I also noticed a slight wobble.. My tires were new and pressure at 34/38.. The problem is the buffeting coming off the bags.. Without them the problem goes away.. This is common on my other bikes with bags also.. I think the only way to rid it completely is get a bike with full fairings.. I now just keep my speed a little slower.. I get to see more things than just the pavement in front of me.. This may not be the answer you are looking for. Good luck..
Take care.

Allen....... Rideaholic
IBA 21871
 
P

paulSF

Scooter
page 51 from the Bonneville user's handbook:

"Never ride an accessory equipped motorcycle, or a motorcycle carrying a payload of any kind, at speeds above 80 mph (130 km/h). In either/both of these conditions, speeds in excess of 80 mph (130 km/h) should not be attempted even where the legal speed limit permits this.
The presence of accessories and/or payload will cause changes in the stability and handling of the motorcycle. Failure to allow for changes in motorcycle stability may lead to loss of control or an accident.
Remember that the 80 mph (130 km/h) absolute limit will be reduced by the fitting of non-approved accessories, incorrect loading, worn tyres, overall motorcycle condition and poor road or weather conditions."
 
C

Chris in NC

Street Tracker
paulSF said:
page 51 from the Bonneville user's handbook:

"Never ride an accessory equipped motorcycle, or a motorcycle carrying a payload of any kind, at speeds above 80 mph (130 km/h). In either/both of these conditions, speeds in excess of 80 mph (130 km/h) should not be attempted even where the legal speed limit permits this.
The presence of accessories and/or payload will cause changes in the stability and handling of the motorcycle. Failure to allow for changes in motorcycle stability may lead to loss of control or an accident.
Remember that the 80 mph (130 km/h) absolute limit will be reduced by the fitting of non-approved accessories, incorrect loading, worn tyres, overall motorcycle condition and poor road or weather conditions."
Click to expand...

That's all about liability.. Mr. Bloor is covering his arse.. nothing more.
 
O

otherwise

750cc
If it happened with throttle backed off, I'd start playing about with tyre pressures. My T100 shakes it's head when shutting off if pressures are not spot on. Also, when it happens again keep power on but gently apply rear brake, this can tidy up a bike when it starts to get out of shape.
 
DandyDoug

DandyDoug

750cc
Hi Laura and welcome,

Good sound advice given so far, remember this: most bikes will develop some sort of wobble or handling oddity under varied and differing conditions, from tire pressures to load and load placement.

I notice some head shake on my 05 T100 occasionally, it's usually something I am doing that the bike does not like at that moment. I just slow down a little and it usually goes away.

Unless it is serious in your opinion and remains constant after checking out all the basic stuff mentioned in other posts. Then I would first add a steering dampner, and maybe a fork brace.

At any rate , please let us know how it all turns out.
 
B

Bonniebird

moped
Thanks for all your advice guys.
I am considering a steering dampner, but at the same time this just treats the problem & I want to eliminate it.....yeah yeah....I know....slow down on those sweepers :flag:
 
2Monkeys

2Monkeys

Street Tracker
I just installed a friction dampner from Farley & Ace. Doesn't stick out the side and look silly like the Hyde and LSL ones, admittedly it is old school and probably not as good as hydraulic dampeners, but it does work really well. I've put 400 miles on it thru some wicked twisties, preforms like a champ.
 
Bullitt

Bullitt

Two Stroke
Hi guys, I got some pretty scary speed wobbles the other day doing well over 85mph. Aside from the steering dampener and proper tires, how much impact does it make running the front end with no fender and no brace?
 
PieMan

PieMan

Two Stroke
If you have checked the setup of the bike and it is all correct and it still wobbles over 85mph, then you'll have to adapt your riding style and position.

I have had this problem for the last three years and after changing to cartridge forks, 17" cast wheels, upmarket rear shocks, steering damper and changing all bearings in the wheels and steering, it is still there above 85mph. (a steering damper won't stop this, it just limits it a little)

The cause of my problem is Hyde Western bars and 28mm risers, but for 80% of my riding they are a great setup and very comfortable. The more upright your riding position and the more you go over 85mph, the more violent the wobble. It seams the wind blast acting on your body lifts the front end and causes the wobble.

The only cure to the problem I have found, is to take the pressure of the wind blast on your torso, in your stomach muscles and put no rearward force on the bars, just hold them firmly. With this riding style I can go up to around 115mph and if I lay on the tank over 120mph with no wobble.

Give it a go next time you're heading to the ton and see if it cures your problem.:)
 
Speed3Chris

Speed3Chris

I like Dick
Before you do anything, find another road similar to what generated the wobble only this time remove the bags and see if you can repeat the issue.
A list of things contributing to wobble:
- Displaced tire belt or tire that can't be balanced.
- Wheel out of balance.
- Bent wheel
- steering head nuts too tight or too loose.
-wrong tire pressure front and rear relative to payload.

A bent wheel and steering head tightness can be evaluated at home with a lift. Easy to spin the wheel for runout and there is a procedure in the service manual to determine proper steering head nut torque.
You need a balance machine to determine wheel balance.
Tire integrity is hard to determine. A wheel that won't balance is generally a telltale the tire is bad if the wheel has little or no runnout.

Good Luck.

A windshield can create a wobble at high speed as well. Running both windshield and bags maybe creating a disturbance...but generally these items simply magnify an existing condition. Upgrading the suspension won't necessarily help your issue if the root cause is related to the above.
 
S

strokerlmt

Moderator
I have the 17 inch from alloy wheel. I always check tire pressure. I have a fork brace, steering damper and I have played with the internals on the forks. I have seen 100 on numerous occasions with and without my saddle bags. I have to be honest that is not the norm for me. But 70-80 on the highway loaded happens a lot. I have never had a wobble. Having said that I don't know which bit would be the best.
LMT
 
B

BonnePhill

moped
Remove wind blast from your torso

I agree with Pie Man, with regard to pressure of the wind blast on your torso.

I have felt the wobble during some high speed cornering. Rolling on the throttle and leaning forward put a stop to it.
Since then I have put a small Dart screen on the front of the Bonne. It deflects the wind from my chest. It may give some down force to the front.
The bike is much nicer to travel at speed and I had forgotten about the wobble till reading this thread.:ride:
 
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