Wobble...

[Digby]

...So, I let go of the handlebars today, (just to give my hands a very brief and quick shake) and the bars went into a sort of mini tank slap mode! Now, I wonder whether it has always been like this, but I have just never taken my hands off the bars for long enough to notice (or if I did take my hands off, it may have been at a speed where it doesn't wobble much), or something has worn out or is about to fall off.One of the biker guys at work had a play around with the wheel and checked for signs of movement on the (can't remember the name) part underneath the big nut thing in the middle of the bars, but he said he couldn't feel anything really.He suggested it may be worth seeing if it needs a slight adjustment though anyway.

I get no wobble at all when riding properly, even with very light pressure on the bars, but they go a bit 'star wars kid' if I let go of them.I know keeping hold of the bars at all times is the best advice of course, but something isn't right, so I thought I would test your knowledge.

Bike is only a 125 Varadero, so none of that fancy damper stuff going on and I doubt it is related, but at the weekend I did tighten the chain a small amount and also had the front fairing off to give things a bit of a scrub up.I have never touched anything on the front wheel though and it seems well balanced and the tyre is still decent and inflated ok.

Edited by Digby on Tuesday 5th August 17:54

[RizzoTheRat]

Might be normal, but could be (in no particular order):

Head bearings - This is the bit your mate looked at, run the front wheel up against a wall and push the bars towards the wall while keeping a finger on the join between the frame and the bottom bolt of the head race

Wheel ballance - probably not as you'd feel some vibration when riding

Tyre pressure - you said you'd checked it though

Tyre wear - is the front starting to wear a bit square?

Wheel bearings - lifting the front and seeing if there's any sideways movement of the wheel will show if there's a big problem, but it's a lot easier to check with the wheel off and wiggling the axle around in the bearings

Fork bushes - Lift the front and pull the wheel sideways while looking to see if one fork leg slides up slightly more than the other one.

Lack of weight on the front - it's a fairly upright bike so presumably your body weight wasn't a lot further back to lift your hands off, did you have a loaded top box on?

[PulsatingStar]

Could it not just be lack of no handed skills? I have tried once and didnt like it. Never used to be able to do it on my BMX either as a kid despite having mates who could ride miles and round bends with no hands.

[Chilli]

Interesting, cause when I let go of the bars, they're as steady as a rock. I fear something may be a miss....but not qualified to suggest what. Sorry.

[dern]

PulsatingStar said:

Could it not just be lack of no handed skills? I have tried once and didnt like it. Never used to be able to do it on my BMX either as a kid despite having mates who could ride miles and round bends with no hands.

No. They should be steady.

Also (i.e. plus all the stuff Rizzo said) lean the bike back so it's supported between the stand and the rear wheel with the front off the deck and move from side to side feeling for notchiness which would indicate you headrace bearings are knackered. The blade used to do exactly what you're describing although it was more of a gradually increasing weave than a slap and on inspection the head race bearings needed replacing. Steady as a rock afterwards.

Edited by dern on Tuesday 5th August 21:42

[Digby]

Lots to go on there, much appreciated! It's not down to lack of no-handed skills though I don't think, I was one of those who could ride all day with no hands when I was younger

Top box is an interesting suggestion - I just fitted one! Today was also the first day I have ridden with it on and with my work bag stuffed into it.I usually have said bag on my back.It wasn't that heavy a bag though, probably only the same weight as an average helmet.Would that be enough do you think? It is hanging off the back though, so that weight will be amplified no doubt, so you could be on to something there.In fact, the front end did feel a tad lighter, but I just didn't think about the box being the reason! (seems rather obvious now of course - wood for the trees springs to mind)

I shall use it tomorrow minus the box (it just clips on and off the base) and will report back.

Thanks again chaps!

Edited by Digby on Tuesday 5th August 21:54

[D1 MAD]

Just to add a couple more suggestions......

Carefully try taking your hands off the bars on a couple of different bits of road just in case it was a feature of the road surface that caused it. It doesn't take much of a ripple or tram line to unsettle a light bike.

Check the wheel alignment carefully with a straight edge as you mention you recently adjusted the chain. Most rear wheel spindle adjusters are not very accurate, a 1mm difference on the rear spindle can mean 10mm+ difference or more at the front and this will affect the handling.

[Digby]

D1 MAD said:

Just to add a couple more suggestions......

Carefully try taking your hands off the bars on a couple of different bits of road just in case it was a feature of the road surface that caused it. It doesn't take much of a ripple or tram line to unsettle a light bike.

Check the wheel alignment carefully with a straight edge as you mention you recently adjusted the chain. Most rear wheel spindle adjusters are not very accurate, a 1mm difference on the rear spindle can mean 10mm+ difference or more at the front and this will affect the handling.

I did try different pieces of road matey aye.I tried around four or five on the way to work in the end, including the ultra smooth tarmac outside our works unit - it was the same on all of them.I was so convinced that it was due to the back wheel or due to something wearing out, that I forgot all about the top box though, so I am really hoping it's as simple as that! I would imagine, on larger and heavier machines, a box on the back isn't too big a deal, but it may make a big difference to a 125 jobby.
I noticed a thread explaining how to line up the back just the other day though, so will give that a go too.

Fingers crossed and cheers again all.

[Brummmie]

This tyre "shimmy" can be when certain components resonate, some models of bike are really prone to eg Pan European, worn components can cause this or unsuitable/worn tyres. I'll bet you'll find if you let your hands off the bars in deceleration it will happen at the same speed each time, and will go through it. Has the tyre got a stepped wear pattern? if so a good place to start if you cant find anything immediately baggy.

[Digby]

Update..

Well bu@@er me and call me Susan, I removed the top box and could only manage the tiniest of wobbles on the way to work today!!
I would never have thought it could make such a difference.That's not to say the rest of the bike is perfect of course, so I shall be doing other checks (I am still assuming it really shouldn't wobble with the box on) , but for now, I can breathe a small sigh of relief.

Thanks for all the suggestions and a big thank you to RizzoTheRat for mentioning the top box.

[Hyperion]

My bike (Divvy 900) is exactly as you describe. Removing the top box, even if empty, pretty much cures the problem.
I only found this out after I'd replaced the wheel bearings, fork bushes, headstock bearings, swing arm bearings and tyres!