front end wobble?

[raphski]

Hi,
This evening I was out for a little ride when I noticed a shimmy. I forget if I had both hands on the bars when it started. What I discovered is that when I took both hands off the bars it would wobble away. It has recently rained a bit and my bike was parked in the dirt of New Mexico but I didn't notice any caked on mud. Has anybody else experienced this? Or ideas on where to start?
Thanks!
Raphael

[Tony Smith]

Hi,
This evening I was out for a little ride when I noticed a shimmy. I forget if I had both hands on the bars when it started. What I discovered is that when I took both hands off the bars it would wobble away. It has recently rained a bit and my bike was parked in the dirt of New Mexico but I didn't notice any caked on mud. Has anybody else experienced this? Or ideas on where to start?
Thanks!
Raphael

Start at the back - wheel bearings, swingarm bearings, shocks (unlikely) and check the tyre for damage.

Then move to the front - check wheel bearings, damage to tyre and then any play in head stem bearings and whether or not there is too much (or too little) pre-load in the head stem bearings.

If all the above fails to find/eliminate the cause then other things come into play - what brand of tyre is fitted? How old are they and how worn?
 
I have had experience with my R100 that it simply did not "like" a particular brand of tyre (back in the 80s Pirelli Phantoms would result in tank slappers after only minimal wear - happened to two sets of Phantoms and has NEVER happened with any other variety of tyre). I have never heard of the R65 being particularly tyre sensitive (in fact quite the opposite) and I have long experience withthe wife's R65/80 and over the years it has had a wide variety of tyres on it and it has never created a problem - I am strongly inclined to think you have a bearing problem.

[georgesgiralt]

Tony, I respectfully disagree.
My R65 was very dangerous with Dunlop tires (K81 if my memory serves me right) and some Michelin tires : A48/M48 were the worst.
I had a pair fitted and had no money to change them, so I rode the bike until they worn out. Going above the 60 km/hour barrier was a frightening challenge, as the bike would slap your hands on the tank if you did not hold the bars very very hard.
At that time I spoke with French police (they had R80 and R100 bikes and used Michelin tires, made in France...) They told me I was insane to drive with them. They had an accident with those tires.
At that time, you couldn't get others guy's advice through the Internet... Now, all you've to do is ask and listen....  

[jamo]

Hi Raphski
 see my thread shaking its head I had head brgs changed. It appears they need a preload. Take a look at the recommendations. Jamo

[Tony Smith]

Tony, I respectfully disagree.
My R65 was very dangerous with Dunlop tires (K81 if my memory serves me right) and some Michelin tires : A48/M48 were the worst.
I had a pair fitted and had no money to change them, so I rode the bike until they worn out.  

Thank you very much, I think my wife has been lucky because from time to time her bike has had some truly questionable tyres fitted to it

I have from time to time wondered why my R100 reacted the way it did and now you tell me that the R65 has the same hidden vice.

Have you ever seen or heard a plausible reason?

[nhmaf]

All the suggestions are good, but before you go too far into the seriously technical, just make sure that your tire pressures are good.   My R65 runs great with the BT45 tires on it, but once time I unintentionally let the front tire pressure drop down to 22-25 PSI, and it developed a significant wobble right in the 40-45 MPH zone that was very off-putting, and came and went as if on a switch.  Having too low tire pressure can cause all sorts of oddities, even with modern tires.   Adding air to get front and rear back up to 35-36 PSI and my worries about bad head bearings went away immediately.

[raphski]

Thanks!

I have not had a chance to investigate further yet but tires should be good.
Back is just a few months old, Metzler Lazertec 4.0-18
Front came on the bike also Lazertec 100/90-18 in great shape.

I just checked pressure and I will have to go for a ride to see if that's the issue. I did just realize my little pressure gauge is not accurate. It read 31 for the rear but when I put the pump on it the digital gauge read 28, I'm not sure if that's enough for a wobble but I will find out. I'm running 32 front 34 rear which is what's speced on the tires.

[skippyc]

Agree with the tires I have a sneaky front tire leak and i can tell straight way if its down too low.

[georgesgiralt]

Pressure into tires is not sensible only on the BMW. When I ride the Honda, if the pressure is too low, it looks like I've a leaky rear damper, and steering column bad bearings. I let a co-worker use it and he said I should  change bike because it was too lousy. I told him "I'll put some air into the  tires" and  that fixed the problem...
So since that time, I'm  called "put some  air into the tubes"... at work.
Tony, I've no explanation about the sensitivity of the BMW to tires or some tires, but it is not that uncommon. I've heard that the Ducati are better on some tires and my Hinckley Triumph liked very much the Bridgestone over the Michelin. Bot make/model where approved for the bike by Triumph.
One should ask a   R&D person at a big tire company to have an answer...

[Bob_Roller]

Any sign of balance weights missing on the front wheel ??

Look at the sidewall on the front tire, there is guide line that is comprised of very small vertical lines right around where the tire meets the wheel, it should be consistent all the way around, if not the tire may not be mounted properly .

[raphski]

No sign of a missing weight but also no weight on the front wheel. The pressure didn't change much. It still has the wobble and it's speed sensitive. My speedo is not accurate but I would guess around 35 mph it kicks in as I have my hands off the bars and am decelerating.

[donbmw]

Sounds like loose steering head bearings. To me

[Matt Chapter]

I would guess around 35 mph it kicks in as I have my hands off the bars and am decelerating.

I can't remember, do you have a fairing / windscreen / front end modifications?  My Pichler, in all its various configurations, has always caused a front end wobble if my hands aren't on the bars while decelerating.

[raphski]

I do have a small Emgo fairing, I can't imagine it's the cause but time will tell as I get to diagnose. At the moment I'm starting an addition on my house so my focus is there.
Thanks!
Raphael