Had my first real long motorway spin today and after a while I became conscious of a wobble or waggle in the handle bars. When I left the motorway I tried it at lower speeds and it seemed worse at 60kph than at 120kph. The bike tracks straight but the bars move through about 3 or 4 cms at the outer end. At home I checked the head bearings - all ok. It was hard to spin the front wheel enough by hand but I thought I detected the disc/pads on the left disc were dragging in one spot. Would this cause a wobble? Am I looking in the right place. Tyres are new, pads have done about 600 miles.
All input appreciated.
88KE

90% of the time, this problem is related to a front wheel out of balance.
Most of the time, if you have a bad steering bearing, the bike has the tendency to over steer at low speed.

CF

Wea've had several cases of wobble in our two bikes. These were our causes:

Bad or loose steering head bearings.
The wrong front tyre.
Under-inflated front tyre.
Over-inflated front tyre.
Worn front tyre.

Haven't encountered problems from dragging pads or unbalanced wheels, but that may be just luck. Did you get your wheels balanced when you had the tyres put on?

If your bearings are OK, do you also mean tight enough, not just smooth?

If your tyres are new, are you sure they're the right sort, and properly inflated? Are they tyres you've used before?

Underinflate slightly when they're cold, because you'll get up to 4psi extra pressure from thermal expansion when they get up to temperature. Get a good portable gauge and test them after at least 15 minutes, preferably 30, on a warm day. The book says 34psi and that's about right.

If all of that is okay, go around the frame and check that all the bolts are done up properly, loose suspension components is also a possible cause of problems in handling.

Thanks J and Bert. The front tyre is brand new ( only 200miles on it) it was Balanced when fitted. Interesting what you say about the head bearing it is smooth but I felt it was light in it's resistance with the front wheel off the ground. It would be hard to get the Tyres warm here it was only +2 degrees here today before you add in the wind chill factor!
88KE

i have the same issue ...periodically



i have confirmed that it is in fact the disk pad binding and an a out of warp disk ...quite often it cannot be noticed ....but at other times when slowing down it shakes the living hell out of the bars if i let go of both at the same time ...

i also have the low speed viibration at the front fender noise ....if i dismount and give the left caliper a sharp rap , usually the noise disapears as the pad springs back on the quide pins and the piston relaxes just a little more... i intend on doing a good clean up of all those parts soonish and more importantly hope to get a couple of "straight " disks soon.... as mine are below wear limits anyhow (well only in one area as they are scalloped to some degree )



i have a theory about the old rubber brake lines expanding some after a couple of applications of the brakes and not letting the fluid suck back properly ...so the piston kinda stays with some little presure ...out a bit ...



feed back to come after i get time (and dollars ) to do the maintenance properly

About time to try braided lines, charlie

yeah i know jh



its on the list ....

I used to get a wobble when I was running Metzeler Lasertec tyres but am using Bridgestone BT45s and it is good.
With the lasertecs I found an extra 4-5 lb was much better but when they were getting down I was not game to let go of the bars it would shake so much.

K Freak: My partner's K100 had a persistent low-speed wobble with Lasertec's which were brand new when she bought it, but has been ecstatically happy with Pirelli Sport Demon's since switching to those (and I like the way her bike rides, as well!)

My BT45s are fantastic, but when I wore the sides of my front down, it would shake steadily. Mind you, I had a distinct flat spot on each shoulder ...

My RT also shakes the bars hands off at 100kph, although not as bad. The wheel balance, tyre, bearings etc are all ok so I have concluded the vibration is an issue with the bar mounts. Not investigated further as yet. Mine also tracks straight and looking down the forks they seem to be stable when it does it.

pjjms, I would be suspicious of a shake even with what you've checked. What tyres are you running? Have you got bar-end weights? Have you changed the bars at all?

When I got my tyres changed, I rode out to the mechanics with a vibration at some speeds, and could ride back with one finger holding the throttle, the other hand entirely off the bars, going around corners on the highway using my hips to steer (yes, I was very careful!)

I am convinced that these bikes are so precisely tuned that a shake, or wobble, or most vibrations (yes, they vibrate anyway) tell you something is wrong. I have reached the point where I can tell if either tyre is losing air, by how the bike feels.

My '88RT used to do it when the front tyre was worn, as stated by others. I found the Michelin Macadm 50E to be the best on the front because it had a central rib rather than a central groove. Ran it at 44 psi and it never shook the bars at any speed.

pjjms wrote:My RT also shakes the bars hands off at 100kph, although not as bad. The wheel balance, tyre, bearings etc are all ok so I have concluded the vibration is an issue with the bar mounts. Not investigated further as yet. Mine also tracks straight and looking down the forks they seem to be stable when it does it.

Just on that, the bar mount rubbers perish badly because they're exposed, so by replacing all four you'll immediately notice difference

Pirelli demon tyres with 2000km on them, matched set. The front was wildly out of balance when the bike came back from fitting, in fact on a quick squirt to 150kph the imbalance was so extreme it was back off the throttle or.... well not worth the risk. Had weights on the wheel so I don't know if they were from the old tyre or a poor attempt at balancing. Took the time to balance it myself and believe it is spot on. Factory bars with bar end weights fitted. More movement in the bar mounts than I would expect so taking them out for a look is the next step. The forks and tripple clamps are rock solid while the bars are shaking. If they are stuffed has anybody tried machining some from urathane?

88KE, this may not be your problem, but another thing to look at to minimise the problem maybe?

My three cents worth... I waited until I had new tyres fitted and then went to work on checking fork alignment and axle test. (I also have a warp front brake rotor.) following the guide on fork work found HEWRE improved things greatly. The fix was complete with new fork springs. But I went over everything suggested and followed the fork rebuild videos foound on this forum.

? is that link right alby ?

Thanks for the replies so far guys. Ice on the roads here means it's too risky for testing tyre pressures and a -3 even my personal layers of insulation don't last long in the garage these nights. alex & pjjms I had a quick look at the bar mounts and the rubbers there seem a bit softer than I would have expected. Hope I'll get at it over the weekend and report back.
88KE

I have had this problem with both my K100RT and my K1100LT - take hands off the bars whilst decelerating and around 50 to 40 MPH a horrendous wobble/bar shake sets in. I have always used BT45 tyres on my bricks and I like them mostly, however.... once the tread starts getting down a little the front tyre in particular suffers from a "scalloping" effect thereby causing this alarming wobble. I have found that by inflating the front to a minimum of 38PSI (cold) and running the rear at around 40PSI (cold) that this problem can be minimised. However, I think at the next tyre change I will try some different rubber - just my twopence worth

Ok!! I have just gone to the links and some are not working. I will email the owner.. The theory is sound. Ans My spelling is not so sound.

FYI, I am running the bat axe tyres.. There are some videos in here somewhere showing things very simply.