My 1985 K100rs seems to have developed a front end wobble. At 45 to 50 mph if I take my left hand off the grip a significant wobble or low frequency vibration occurs. Hands back on the bars, and speeding up or slowing down and all is smooth again. Dunlop tires are one year old, inflated properly and look fine. Steering head bearings were replaced last year. Axle bolt torqued to spec. I greatly appreciate your thoughts before I take it to the shop $$$. Thanks.

Usual causes of such a wobble is:

• Steering head bearings - did you replace both complete bearings, including outer races which are an interference fit in the frame?
  
• Steering head bearing - check the knurled nut has not come loose and is torqued correctly
  
• Loss of balance weight off wheel - might be worth getting wheel checked for balance. I tried Dunlop street something tyres, didn’t like them and the wore out fast too.
  
• Buckled wheel - like to think you’d know if you’d hit something or a pothole that hard though
  

When I have experienced the symptoms you describe, it was my steering head bearings that had worn. Changed them and all good.

Recheck the steering head bearings. There's a specific method of installing taper rollers (check your manual - Clymer, I'd guess) and they always need rechecking after X-specified miles.

I had my local shop replace the steering head bearings last year. I trust these guys but I will talk to them. I will check tire for balance weights. Thanks for suggestions!

Mine had a head shake from a bent fork  

Years ago, on the Yellow Peril, ('90 K100LT) riding home from a gathering up north with Charlie and the boys, I had a very similar occurrence. Downhill, about 70 - 80 Km/h, hands off the bars to have a stretch, the front wobbled like crazy. Had to be v.quick to get the hands on the bars again to regain control.

After much gnashing of teeth and numerous enquiries, it turned out to be the front tyre! Replaced and all was well.

Mine too is the Yellow Peril! The tire looks good, but?

Dean, that looks great!

I must admit that at times I do miss the K!   

Taxi!!!

That is not a stock color. I know mine isn't. Looks great and can be seen!

I've also had head shakes when on overrun at those speeds, and it gets worse as the tyres wear out. One time I had a Metzeler Lasertec on the front which was simply horrendous..

So, what pressures are you running and what kind of tread depth have you got left?

Snod Blatter wrote:I've also had head shakes when on overrun at those speeds, and it gets worse as the tyres wear out. One time I had a Metzeler Lasertec on the front which was simply horrendous..

So, what pressures are you running and what kind of tread depth have you got left?

I had 2 Ks that POs had Lasertecs on them. Absolutely horrific tyres and found them really bad in rain.

After that, all got BT45. I set the K100LT on cruise on motorway and did about 5 miles hands off using slight body weight shift to steer. Steady as a rock, head bearings and rear shock and rear tyre all known to be good at the time and not carrying much. Too much weight biased to the rear can cause shake too.

DeanG wrote:That is not a stock color. I know mine isn't. Looks great and can be seen!

Being a Portland-area bike, is this the Bismarck, of Old Goat fame?

What is the recommended (personal experience wise) tire pressure?
  On my RT, running solo, 34psi front, and 38 psi rear seems to do well. If I run 32 front, 32 rear the head shake increases.

schrocketeer wrote:What is the recommended (personal experience wise) tire pressure?
  On my RT, running solo, 34psi front, and 38 psi rear seems to do well. If I run 32 front, 32 rear the head shake increases.

Never less than 38-40 psi front & 40-44 psi rear (load dependent), radial Michelin Pilot Road, on my 1987 K100RS. When I used Pirelli Demon bias ply I used a bit less than 44 psi in the rear, but I have always kept higher pressure in the front for suspension 'feel', tyre life and steering precision.

I have also experienced similar behaviour.
You can check out the thread in the below link.
https://www.k100-forum.com/t14227-unprovoked-wobbling-k100rs#167130


In my case it was the front tire that cracked due to old age (as you can see from the pictures way down in the thread). This shouldn't be the root cause of your issues unless you drove over a nail or pot hole and developed an internal crack.
Everyone on this forum also told me that the tire pressures in the manual are too low for modern tires.
The thread also describes a simple test you can do to check the front wheel bearing which could also be a source of wobble.

My fix was simple. Change tires and inflate to the above suggested pressure range.

Hope this might be of help.

Best regards,
Einar.

I have Avon RoadRiders on Low Flying Brick and run them at 38/42psi. Much better feel than the recommended pressure by a long, long way.

Dai wrote:I have Avon RoadRiders on Low Flying Brick and run them at 38/42psi. Much better feel than the recommended pressure by a long, long way.

+1 on those pressures for my BT45s and Pirelli Sport Demons. Massive improvement in road grip, stability and tyre wear.
(A bit more in the back if I'm loaded up for a trip.)

Bill

I have been running tires a pressure recommended in original owners manual. I will try with more air and report back. Thanks.

Read in CLYMER. BMW do not recommend V rated tyres on K75s .
Anybody know why.

Dai wrote:I have Avon RoadRiders on Low Flying Brick and run them at 38/42psi. Much better feel than the recommended pressure by a long, long way.

I use these same pressures too on Battlax BT45 and arrived at them by trial and error before I came on the forum. I can tell on the bike if they have dropped even 1psi

I get my tyres on at a Honda dealer and they send every bike out at 30/30.

moriarti wrote:Read in CLYMER. BMW do not recommend V rated tyres on K75s .
Anybody know why.

That's old, out-dated info from the time when V-rated tyres were very soft and wore out quickly. The heavier the bike, the faster the tyres wore. More manufacturers don't even make H-rated tyres any more.

Thanks Dia,SENIOR MOMENT, my mate rides a 75 so needed to ask 



see what i mean cant even spell DAI 

38/42 here as well.  One up or two, an afternoon ride or taking off for three weeks those pressures work pretty well on every brick I've owned.  Metzlers, Continentals, Shinkos or Bridgestones, 38/42 works.

When the pressure gets down to 32 front or 34 rear I can feel how hard the bike is to push around the garage.

92KK 84WW Olaf wrote:

Dai wrote:I have Avon RoadRiders on Low Flying Brick and run them at 38/42psi. Much better feel than the recommended pressure by a long, long way.

I use these same pressures too on Battlax BT45 and arrived at them by trial and error before I came on the forum. I can tell on the bike if they have dropped even 1psi

I get my tyres on at a Honda dealer and they send every bike out at 30/30.

It amazes me what various dealers do and say to their customers. Last year I was riding in Podunk Montana and had a slight front end vibe on my K1300GT. I saw that a couple of the wheel weights had gone walkabout - weights I had improperly 'installed' the week before. I went straight in to the Honda/Kawasaki/farm equipment service department enquiring whether I could buy a strip of 1/4 oz weights from them. The service manager stayed sitting at his desk 20 feet away and with almost a pained expression, defensively told me to go and look at any of the 200+ mph bikes on the floor (not a single bike there would go more than 186 mph, but that's another story). "None of them have weights on them." he proclaimed. "We don't balance any tires here. Haven't for years." I didn't even answer him, just turned round and walked out the door. A salesman saw the exchange and snuck outside to hand me a business card of a local guy who did work on the side on bikes. I imagine this scenario plays out regularly there.

A Michelin distributor rep told me a coupla years ago that every new Michie radial made has no natural rubber in it (all silica, he said) and that you should just air them both to 42 psi, that there's no real 'warm up' period as in the 'olden daze', checking pressures every once in a while. I don't take that advice as gospel and can feel the difference when my front tyre(s) are above or below 40 psi.

As long as we're talking tire balancing, let me add that I check my wheels before I install the tires.  Every one I check has the heavy spot somewhere other than the valve stem. 

I mark that spot and that's where I put the dot on the tire.  Sometimes it's as much as 90 degrees from the valve stem.  It has made my anal pursuit of balance perfection a lot easier.

I usually go with the manufacturer's balance spot, of course meant to located near the valve stem. But recently I fit a set of Conti Road Attack 2 EVO GT - what a handle! - to my 13GT. They didn't have a balance spot at all, and neither did the set my mate fit to his '98 K1200RS, on my recommendation. Both of our sets used only two 7 gram (or 1/4 oz) weights to spin smoothly with nary a shudder or rumble of imbalance. I do also check my bare naked wheels for their own heavy spot. 

I've noted lately on the newer BMW front wheels with the sideways to the right facing valve stem, that this is the heaviest area of the rim. Additionally, I've removed the TPMS from the K13GT wheels because it took so much weight to get them smooth running that checking the pressure with a standard pencil gauge regularly is easy, fun to do, and potentially lifesaving anyway. I don't need no stinking warning light reminding me of maintenance I should be doing anyway.

The last two sets of Michelin Pilots were good from the start and gripped straight off not greasy. I just took it easy for around 100 Km's. The guys who fitted the rear tyre couldn't balance it as the BM wheel wouldn't fit their machine. He told me rears didn't need balancing anyway. I tried a few other places including a car tyre place and the only place I was told that could do them was southside Brisbane. I ended up making my own blade type balancer which although a bit finicky it proved accurate. I later modified it to the four bearing type.
Regards Martin.

Set my Speed Demons at 38/42. Did not help. 6000 miles in year since installation .

DeanG wrote:Set my Speed Demons at 38/42. Did not help. 6000 miles in year since installation .

You said you have Dunlops in your original post. Pirelli make the Sport Demon which several here, including myself, have used.

MartinW wrote:The last two sets of Michelin Pilots were good from the start and gripped straight off not greasy. I just took it easy for around 100 Km's. The guys who fitted the rear tyre couldn't balance it as the BM wheel wouldn't fit their machine. He told me rears didn't need balancing anyway. I tried a few other places including a car tyre place and the only place I was told that could do them was southside Brisbane. I ended up making my own blade type balancer which although a bit finicky it proved accurate. I later modified it to the four bearing type.
Regards Martin.

Martin, have you seen this BMW rear wheel balancer adapter?   I got mine used on eBay, I think Harbor Freight used to sell them.  Might be something your machinist guild might want to manufacture.

Very interesting Gryph it would be something the Guild could manufacture, however still closed at the moment. Before we closed we were trying to come up with something else we could manufacture. The chippie shop is flat out as is the casting foundry, there is however a bit of resistance in the machine shop, which Bernie and I are trying to overcome. The four other guys in there are only interested in doing there own thing. Which balancer does it work with Static or Dynamic. The one I ended up making and then adapting will work on brick front and rears plus heaps of other brand motorcycles. However there looks to be more involved in making my version.
Regards Martin.

Martin, it is designed to work with a static balancer.  It essentially just provides a hole for the balancer's cone to be inserted into. 

The side with the threaded holes needn't be that complicated.  It really only needs the four holes to match the classic K bike hub.  The other holes are there to accommodate other bolt patterns.

If you like, I can provide you a sketch with dimensions.

Thanks Gryph it would be appreciated. How much were they when they were available? 
Regards Martin.

Martin, I'll get something for you this weekend.  Might be something you guys can sell.  As far as cost, I think I paid $35 "used" for mine.  I have no idea of what they cost new, maybe around $30-40?

Thanks Gryph but no panic. I can't even use my own lathe at the moment as the Guild shutdown caught me in the middle of a lathe rebuild. 
Regards Martin.

My apologies to the forum for this thread hijack.

Point-Seven-five wrote:My apologies to the forum for this thread hijack.

I never met a hijack that didn't intrigue.



I got mine from Harbour Freight some years ago and used them for several years before my machinist mate told me - when he'd borrowed them to make copies - that the centre was offset a tiny red pubic hair fraction of mm's. He remedied it for me and now I'm accurate. But I was ignorant of my lack of accuracy prior so it doesn't matter much.

These do not work on the newer bikes (R1200, K1600, K1300, etc.) with five spokes but fit Oilheads and all of the older K's.

Okay, now I have to go out in the garage and get the dial indicator out.

Tire inflation ✓
Tire tread ✓
Wheel balance ✓
Steering head bearings ✓

Nevertheless a pronounced front end wobble occurs between 45 and 50 mph. My mechanic suggests the problem may be caused by worn suspension and is recommending new rear shock and springs up front. Any thoughts on this mystery? Any recommendations for product?

recommend a set to 'Pounders' 17oz by the Manic Salamander

Fork alignment

https://w6rec.com/duane/bmw/fork/title.html

https://brook.reams.me/bmw-motorcycle-rebuilds/1973-bmw-r755-rebuild-project/31-bmw-r755-install-and-align-front-forks/

In my slightly different world. 38, 44. Solo plus chair. Battlax 45.

If it really is the suspension, upgrades depend on your pocket. The cheapest upgrade is a Hagon rear shock coupled with Motorworks own progressive fork springs. Cost; somewhere in the region of £250. Midrange upgrade would be a RamShok rear and Hypro/Wurth progressives up front. Cost; somewhere in the region of £400. After that, take out another mortgage because you're into Ohlins territory.

What difference does it make? I did the midrange upgrade on Low Flying Brick about six years ago. I thought someone had stolen my bike and then given me a new one back but with all the old scratches and marks on it.

My RamShock rear was also transformational. HD rears on the leading links, got for 40 quid the pair with delivery mileage only on them.
If I won the lottery I'd look at getting a pair of something specifically matched to the outfit.

Advice on suspension work is optimistic. As I am not an experienced mechanic I suspect that I can probably swap out the rear shock but I am no so confident on working with front forks and springs. I shall probably proceed as I would want to even without the mid-range wobble just don't know if it will fix it.

Some things I would do:

First, have you lowered the bike by sliding the forks up in the triple clamps?  Try raising the front if it's been lowered.

Second, Does either brake rotor drag against the caliper.  Get the front wheel off the ground and rotate it slowly to see if the rotors run true in the calipers.

Third, loosen every fastener that holds the forks in position including the mudguard bolts.  Bounce the bike several times on the front end, and then go through and snug everything up a little bit starting with the triple clamps followed by the axle clamps and axle nut. Then do the mudguard and fork brace.  When they are all snugged, go back and torque them.

Point 75. That sounds like good advise. Yesterday I had the boffos at Cheshire Motors here in Portland double check steering head bearings, inspect and test drive. Wobble was still the same. I will discuss with them again next week. Thanks for all the ideas!

Agree with P75's suggestions :

1) Have the front forks been maintained ? New oil etc ? Fairly easy job to change it and can make a huge difference. The check valve will be sensitive to oil with the wrong viscosity and/or old oil losing its properties. Alternatively it could be a malfunctioning check valve in one of the forks.

2) What rear shock absorber do you have ? If you can adjust / preset the spring load to different settings, try doing that and do test drives. If it changes the wobble and/or the range when you experience the wobble, that would give you an idea if that is the root cause. If the behaviour doesn't change with different load settings, then the rear shock is likely not the cause.

3) The brake discs yes ! If one of them are slightly bent or deformed (front of rear) that could be a source of wobble.

E/

Surprise! Last week I installed a Laminar Lip.windscreen extension. I tried adjusting the little BMW lip to allow more air to flow under the Lip. Guess what? The wobble seems to have disappeared! Still seems too sensitive if this minor adjustment makes a difference. My intention is to move ahead with rebuilding front forks and replacing rear shock.

DeanG wrote:Surprise! Last week I installed a Laminar Lip.windscreen extension. I tried adjusting the little BMW lip to allow more air to flow under the Lip. Guess what? The wobble seems to have disappeared! Still seems too sensitive if this minor adjustment makes a difference. My intention is to move ahead with rebuilding front forks and replacing rear shock.

When you thought you read every thing a Laminar Lip wobble, bloody brilliant

Progressive springs and Ohlins rear damper to match your moto color nicely. ride on