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Wheel wobble ideas?

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sullivj
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Wheel wobble ideas?

Post by sullivj on Wed 02 Sep 2015, 9:26 pm

If I release the bars between 35 & 45 mph, the bars give a serious wobble that could turn into a full on tank slapped if not re-gripped.

So, today I had the front wheel balanced and that didn't solve it.

Other ideas I have:

Top Box removal
Inner bar weights not right
Rear wheel not straight

Anything else I should check?
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jerryfudd
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Re: Wheel wobble ideas?

Post by jerryfudd on Wed 02 Sep 2015, 9:48 pm

I know we've spoken about it but just a few questions that spring to mind.

can you feel any indication there may be a problem before you release the bars? have you tried just releasing one side or the other to see if there is a difference? does the problem go away when you regrab the bars? (obviously dependant on the answer to my first question) .....also how does appling the brakes both individually or together effect it?

also to throw into the mix, fork bushes? head bearing tension? (i remember you said it doesn't feel shot but maybe too loose?), wheel bearings?
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ashcroc
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Re: Wheel wobble ideas?

Post by ashcroc on Wed 02 Sep 2015, 9:50 pm

My money's on the topbox causing it.  They can do strange things to airflow at certain speeds, especially if overloaded.

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jerryfudd
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Re: Wheel wobble ideas?

Post by jerryfudd on Wed 02 Sep 2015, 9:52 pm

just on the wheel bearings now that I think about it a friend at work had a wobble issue on the front end of his blade and only found out the cause when just one side collapsed while riding - and this was after a garage assured him they were fine.

maybe it's hard to detect when it's just one side?

sullivj
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Re: Wheel wobble ideas?

Post by sullivj on Wed 02 Sep 2015, 10:27 pm

Good thoughts chaps - thanks.

I will run through the list and report back.
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stormbringer
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Re: Wheel wobble ideas?

Post by stormbringer on Thu 03 Sep 2015, 6:02 am

We've been over the front wheel wobble several times.

What I've picked up so far:

  • Top box will 'promote'the wobble. Lose the top box. Besides; is it an original one? If not, your OCD (this one's for you, @sullivj  Smile ) will thank you for correcting the mistake.
  • Worn bearings, loose headstock, worn stanchion & slider bushes all leave room for wiggling around, allowing the wobble to be set off.
  • Tires. They start out being perfectly round (at least BT45's do...), then develop a 'wear pattern' over time. Run the palm of your hand over the tread of a worn one and you'll notice little hills & valleys on the surface. I'll bet this is not good for keeping wobble at bay. Also, putting on a new front tyre seems to reduce wobble, so I guess it affects the phenomenon
  • Lastly, front wheel wooble appears to be inherent - it's a part of the bike's design and can't be avoided. It has something to do with the bikes' wheels starting to generate gyroscopic effect as you pick up speed. Below trigger-speed the gyroscopic effect is unnoticeable, and above it is dominant in a resonance-scenario with the frame/suspension. Only at trigger-speed will it cause wobble. Have a look at the video below, illustrating the phenomenon and offering an explanation:



Bottom line: It's hard to avoid wobble entirely. It's best not to ride your bike at trigger-speed. Go faster or go slower.
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Jameshambleton
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Re: Wheel wobble ideas?

Post by Jameshambleton on Thu 03 Sep 2015, 8:34 am

I remember reading a thread on here about a year ago now and it was found that the steering wobble between those speeds was caused by the topbox.
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davebike500
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Re: Wheel wobble ideas?

Post by davebike500 on Thu 03 Sep 2015, 10:17 am

Top box will not help 
BUT  low front tyre pressure is common cause as is worn front tyres or unevenly worn tyres

I run with a box and panniers all the time a little extra pressure keeps the wobbles away  well up to 90mph
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jerryfudd
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Re: Wheel wobble ideas?

Post by jerryfudd on Thu 03 Sep 2015, 10:20 am

id be surprised if it was the top box as its a problem that has developed over time which would indicate degradation of a part surely? reckon it's one of those problems where just going to have to start changing and testing everything to pin point Mad

sullivj
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Re: Wheel wobble ideas?

Post by sullivj on Thu 03 Sep 2015, 8:21 pm

It could have been there forever, I've only just noticed it by letting go of the bars.

I wasn't on the bike today, so didn't get to try it again.

Some of those weaves in the video are frightening!!
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badseeds
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Re: Wheel wobble ideas?

Post by badseeds on Sun 06 Sep 2015, 10:49 pm

This is happening on Little Donkey and it's because the headraces are knackered. There's no notchyness, like no definitive notch, with the bike on't mainstand, held down and moving the 'bars. If I brake hard I can feel a clunk though.
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trevor machine
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Re: Wheel wobble ideas?

Post by trevor machine on Mon 07 Sep 2015, 6:31 am

Huh - worth knowing! Think I'm starting to feel the first stages of play in mine on hard front braking. No clunk yet.

sullivj
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Re: Wheel wobble ideas?

Post by sullivj on Mon 07 Sep 2015, 5:18 pm

I don't have a clunk and the MOT guy reckoned the head bearing was fine.  When I've sorted the split tyre, I'll be able to investigate some more.
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ashcroc
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Re: Wheel wobble ideas?

Post by ashcroc on Tue 15 Sep 2015, 6:08 pm

Did the new boots cure the wobble?

sullivj
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Re: Wheel wobble ideas?

Post by sullivj on Tue 15 Sep 2015, 7:08 pm

Sadly not. I just put the wheels back on and took her for a blast. It's still there, same as before. Only noticeable when you release the bars.

This time I rode without the box, so I know it's not that.

I am going to investigate the inner bar weights as I think there's a bit missing on one side from a previous drop. All the bearings seem fine, so I'll start with the weights.
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badseeds
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Re: Wheel wobble ideas?

Post by badseeds on Tue 15 Sep 2015, 7:29 pm

Odd that you've not been able to narrow this down. You've looked at all the obvious stuff, especially the topbox. I'm all outta ideas!
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mcalvert39
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Re: Wheel wobble ideas?

Post by mcalvert39 on Thu 17 Sep 2015, 10:58 am

Not being rude but how heavy are you?
Im a priddy light guy and get the wobble at the same speeds you have. The only way I managed to keep it at bay was by ducking down under the screen (CB500S) reducing drag a little. It does work... for me.
Ive had two other people ride my bike who are much heavier than me and couldn't fault it, so it may also be due to where and how much weight is in the centre of the bike.
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burning_rubber
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Re: Wheel wobble ideas?

Post by burning_rubber on Thu 17 Sep 2015, 1:17 pm

i had this when riding, at the time i had a top box and two side boxes took them off same thing happens...
so i think it was  the front wheel being balanced badly/ wheel wait falling off. 
when it was sorted i didn't have the problem
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jimbobs63
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Re: Wheel wobble ideas?

Post by jimbobs63 on Thu 17 Sep 2015, 2:25 pm

@Jameshambleton wrote:I remember reading a thread on here about a year ago now and it was found that the steering wobble between those speeds was caused by the topbox.





Hi,

I think james is referring to the thread I started on this topic some time back.  Yes the top box made some difference but didn't eliminate it, as confirmed by others experiences in the messages above.

Having asked in another recent thread on this forum "what's wrong with Avon Roadriders?" and got some strong responses, I have this past week been shamed into getting rid of the Avons  I've had on my CB since I got it, and I've replaced them with Pirelli Sport Demons.  I made sure I got the front wheel balanced at the same time.

Apart from the fact that I have immediately noticed in both dry weather and that monster rain we had yesterday that the new tyres felt so much more confidence inspiring than the old ones (I'll post more details separately), I have also noticed that the wobble has been much reduced, even with the top box still on.  I will have a play with combinations of top box/no top box, with fly screen/without fly screen, etc. just to find out what works and what (if anything) makes the wobble worse.  As for wheel and head bearings having a part to play, I don't doubt it for a moment, however on my CB they seem rock solid.

So, as mentioned earlier in this thread, it may be that you can't get rid of the wobble entirely, but there are a number of factors which can make it better or worse.

On the issue of a heavier rider making it better, I come in at around 14st so I'm not sure that makes a difference.

Jim

sullivj
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Re: Wheel wobble ideas?

Post by sullivj on Thu 17 Sep 2015, 5:26 pm

If a heavy rider improves things, mine should be absolutely fine!

My bike thinks there's always a pillion, but it's just me!!!

The tyres are new and well weighted, so it's not that.

I still have to investigate the inner bar weights. I will find it eventually.
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wornsprokets
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Re: Wheel wobble ideas?

Post by wornsprokets on Thu 17 Sep 2015, 10:23 pm

Is it possible one of wheels might have taken a heavy bang from say going into a pot hole and maybe put a kink in rim causing wheel to slightly wobble. Ive slight kink in rear wheel of my fireblade. I never noticed it but tyre fitter did
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jim157
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Re: Wheel wobble ideas?

Post by jim157 on Thu 17 Sep 2015, 10:36 pm

^^^
I was going to say the same thing but thought the tyre fitter would've pointed that out?

sullivj
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Re: Wheel wobble ideas?

Post by sullivj on Thu 17 Sep 2015, 11:22 pm

It's possible. I'll measure the run out with a clock gauge again. I know they were fine. 

That said, I would expect that to show at all speeds...
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phorx999
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Re: Wheel wobble ideas?

Post by phorx999 on Fri 18 Sep 2015, 12:30 am

Hi im just pitching in. i had this when i first got the bike in march, between 30-45 mph the bars wobbled dramatically, no topbox or flyscreen, the wheeling weights where fine but the tyres where worn and i found the head bearing was a bit buggered (longstory with that mostly paranoia and OCD) but i ended up getting fresh boot (pilot actives) and swapping the head bearing and the wobble went totally. (weight regards im 11st btw so that theory went)
I'm surprised it didn't go with your new tyres.
i doubt wheel alignment would be significant, then surly the whole bike would wobble?
If it annoys you enough you could adjust/grease the head bearing, doing this you go over the fork pinch bolts and the axle and everything checking torque settings, fork levels, etc.
i would NOT recommend replacing the head bearing unless you know its F@cked, its a Bastard of a job. i only did it because i was bored and had 3 months to kill.

Then again its not really a massive problem for the bike as far as i know, just a bit of annoyance.

sullivj
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Re: Wheel wobble ideas?

Post by sullivj on Fri 18 Sep 2015, 6:29 am

Thanks for that.

How did you know your head bearing was shot? Mine shows no sign of notchiness whatsoever and there's no movement at all when I yank about on the forks.

Having lived through JerryFudds replacement, I know what a bugger it is to change!

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