Wobble from front end?

[Miztaziggy]

My bike feels funny under hard braking. As it decelerates, there is a noticeable wobble through the bars at a certain speed.

Eg, I can be doing 70 and brake hard, everything is fine for an instant (other than the massive amount the front end dips under braking as usual). At some speed (say approx 60) as it is slowing down, there is a wobble through the front end, like when a car tyre isnt balanced. As it slows down more (say approx 40) it goes away.

Every now and again, there is a slight click from the front end as if something isnt quite tight...but I dont know what. Feels as though the caliper moves a little and clicks. All the bolts feel to be tight???

Oh and the reason I ask now, is that im heading over to Wales with Benny tomorrow and am worried about how bad it will be when im hammering it trying to keep up with him

[benny hedges]

will have a look at it tomorrow matey

[AMCQ46]

The noise is your steering head bearings a bit loose, and the vibration is a slight disc warp.

And don't let benny near your front or rear end

[Miztaziggy]

Hmm, steering head bearing sounds likely, does it mean fitting a new one to fix it or just tighten this one?

And I thought disc warp, but I dont understand why it would only wobble at certain speeds. I would have thought disc warp would have made it wobble all the time even when braking lightly....but it doesnt...

[AMCQ46]

Any vibration has a natural frequency, so you only notice the wobble when the wheel speed corresponds to the natural frequency of your forks, hence it is only noticeable at a certain speed.

I had same problem on mine, but was only evident after I fitted better calipers and improved the braking. Between 100 and 60 it was very bad, then below that it was gone. I measured the run out on my discs and they were to spec, and I tried to deglaze them as well but only solution was to fit new discs.
Strange thing is I gave the discs to one of the other guys on here as he needed some quickly, told him that I had vibration when braking, but he was happy to try them and he reported no problems!

Try retightening the bearings and see if it gets better

[benny hedges]

And don't let benny near your front or rear end

Richard!

chances are it's still got the original head bearings in so changing them would be an improvement.
usually they go a bit notchy first though as the bearings wear and leave a space in the race.
the knocking is likely to be the headbearings but also could be the slider in the forks...
or possibly the wrong brake pads have been fitted or a poor pattern part?

warped discs cam be corrected with a well aimed smack with a mallet
you can either use a proper dial gauge or what ive done is take each caliper off in turn and put a length of m10 threaded bar through the top hole with a nut either side.
adjust it so it touches the disc at each high spot, mark it and give it a smack until it runs true, then same with the other one.
you dont have to hit them hard btw lol!
they are only designed to be strong in one direction.... changing tyres, anything like that where the wheel could be laid flat could damage the discs.
also they are meant to float on the bobbins - they may be sticking a bit.

[Twinpotter]

And don't let benny near your front or rear end

Especially with a hammer!

Benny, are you positive that a properly warped rotor (and not one that has shifted on the float mounts) can be

corrected with a well aimed smack with a mallet

I don't agree with you mate. As I understand it, warpage is the result of uneven heat in material stresses/defects and no 'lateral correction' can remove these inherent properties. IMO if they're warped they're only good for the bucket.

Front end wobbles, right up there with electrical woes! And these things are often compounded. Last year I helped my pal out with his then recently acquired Varadero that had the same issue and with 27k on the clock (and not a sign of owner maintenance on the thing) there was much to check so we went through the whole front end. After fitting new wheel bearings, rotors/pads and a caliper overhaul and a quick tightening to torque at the headstock, the wobble remained but less so. The front wheel had an OK tyre on it but when he changed his tyres the problem went!

Annoying it is but go through the lot and you'll nail it.
Good luck with the check-up and the run. Let us know how you got on.

[tony.mon]

That's why I always have my tyres dynamically balanced, not statically.
Statically, they balance around the wheel spindle centre, but can be out of balance left/right and then you get wobbles.

Kevin Ash covered exactly this in MCN this week, puts it rather well and easy to understand.

[Stormer Dave]

I had the same...after the cam chain incident and contemplating re-arranging hondas set up with Tommy Hammer (4lb short shank) I decided to fix the lot changed the head bearings one night....

As per comments on here, hand tightened then ran around the block then 1/4 turn...now no probs and superb.

Takes less than hour to put tapers in, £20 to buy........makes sooooo much difference.......

Dave

[sirch345]

Takes less than hour to put tapers in, £20 to buy........makes sooooo much difference.......

I should have got you to do mine Dave it took me nearly as long to remove the bottom inner race from the steering stem using a hand held grinder. Mind you I did want to re-use the bottom seal, so I had to go carefully

Chris.

PS. I wouldn't recommend hitting the brake disc's with anything, if they're warped (I agree with Twinpotter) the bin/bucket is the best place for them. Remember your brakes could save your life one day, so you hardly want to be taking a chance on them.

Chris.

[Styler4077]

I had the disks or disk from AMCQ46 and replaced just one as I'd moved off with a disk lock still on and bent one of the spokes of the inner disk. Never noticed at the time.
Vib from the front end was only at certain speeds when braking.
Funny how the same disk from AMCQ46 and one from mine work OK.
However I did change the brake fluid, hoses to SS braided, Fireblade MC, EBC HH pads and refurbed caliper from Jonesey all at the same time. No chance of finding the faulty item after that lot.
Brakes are fab now and the lever never feels soft