Hello all!

I recently purchased a 85 bmw k75s , and i´m still getting used to the bike. . so about a week ago, as i was ridding ( about 50 km/h) i decided to release my hands from the throttle and release both hands from the handle bar.

I was expecting for the bike to ride straight foward, but instead, the steerig started to shake almost to the point of no control.
It scared th sh*t out of me!!lol  

When i bought the bike , i already knew i would have to change tires, because they have been in the bike for almost 17 years now. but they are not too worn.. so i thought i´dd wait till the rain season to change tires..

i´m now looking for tires and the ones that are recomended are bridgestone bt45
Does any one has this kind of tires?
What do you recommend?

May want to replace the steering head bearings if they haven't been done in the last 17 years.

seems a common issue ,,,(head shake with hands off bars )
i dont think anyone has a solution besides fitting a damper or some such

advice at the time was.... dont let go ....  grin 

but if someone has found a viable solution or good reason ...always willing to find out

Loose or worn head bearings would exaserbate head shake.  Test for steering looseness/tightness by taking pressure off the front (have someone sit on the back, and lean backwards to force the front up), center the steering and gently push the bar end.  Steering should gradually flop over to lock position.  If it is too loose, it won't even hold center; if its too tight or the bearings are notched, the triple tree will stop through its movement.  While the front wheel is up in the air, grab the rim at 6:00 and 12:00 and try to move the wheel towards and away from you.  You should not hear or feel clicking.

I had the same issue with my 89 RS.  I sold the bike (not because f that) but replaced and adjusted the steering bearing, rebuilt the front forks, new springs, replaced with new RAM shock on back, nothing.  Still a head shake from 47 to 50 MPH, but only with hands off bars, you could feel it with one hand off. 

Like others my advice is keep hands on handlebars.  It was worse with worn tires, better with new ones.  If you find out anything let the forum know, but I did all the recommendations and it was still there.

New silicone grease in the steering damper could also make a difference.

17 year old tyres are lthal, no matter how much tread they have. They will also have flat spots. They go hard. Change them immediately. Over here car tyres more than 5 years old are not legal. A bike tyre over 3 years is not good. 5 years max.

I have BT45 on the K, find them great in good or wet and even in winter. Old tyres on bike when I got it and the difference with new ones was unbelievable.

I then also did the head bearings and it was a huge further improvement. I would do them if they have never been done.

orforester wrote:I had the same issue with my 89 RS.  I sold the bike (not because f that) but replaced and adjusted the steering bearing, rebuilt the front forks, new springs, replaced with new RAM shock on back, nothing.  Still a head shake from 47 to 50 MPH, but only with hands off bars, you could feel it with one hand off. 

Like others my advice is keep hands on handlebars.  It was worse with worn tires, better with new ones.  If you find out anything let the forum know, but I did all the recommendations and it was still there.

Mine is exactly the same, now with the rear being very worn it is sometimes like riding a bucking bronco. Hitting bumps while leant over at speed is a very interesting experience too.

It seems to be a basic flaw in the design somewhere, my money is still on the frame flexing in the spine, the extra bracing on the 1100 suggests this is possible. Do the 1100s suffer from this head shake?

possible not a design flaw but typical of the design ...

I see kawasakis and many others now with the single sided rear end suspension...but a totally revamped subframe  with I note, super double walled and tubed diagonal bracing to towards the steering head  from that rear pivot point ..

interesting to note all the same

None of my Ks has done that. I can take my hands of the bars and ride for miles with the cruise control engaged and the 93 K1100 is exactly the same frame as the K100.

From years of fixing bikes that have had accidents, if it is shaking its head then there is something wrong with the geometry.

Check the fork tubes for straight, triple clamps for twisted, steering head for a slight twist the swing arm for laying over and twisted and alignment of front and back wheels.  Your steering head only needs to be bent so that the bottom of the front wheel is 2-3mm out of line with the centre line and it will shake like a dog shitting razor blades.

Use a plum line to check for the wheels being vertical when at centre.

About 40 years ago, I had a Suzuki GT750 with the same problem. It was solved very quickly. A simple re-balancing of the front wheel solved the shaking. (You cannot imagine how bad an unbalanced wheel will shake the stearing).
One other thing is that the BT45 is a dual compound tire. The rubber on the side is a lot softer than the rubber on the flat part. If under inflated, it could quickly develop a scalloping shape and this would create the same problem.
For the head bearings, before changing them, I would recommend to generously spray them with WD40. After years of service, the grease is drying and it becomes like a varnish and the bearing is not working smoothly.

I didn't ever have a shimmy in either the L T or the RT. But they are in my opinion very sensitive to fresh yres and having them at the right pressure.

I am not so sure the head bearings would cause it, I did them on both Ks and the effect was very obvious at low speeds in town but less so on open road speeds.

Look at wheel balance and also that the fitting of the front wheel is correct, tighten axle bolt and then tighten clamp bolts. Not the other way round. K75 has the damper which can go wrong too.

A scalloped BT45 front tyre will also do that. Higher tyre pressure will help to reduce it but if scalloped change the tyre.

I did tighten mine from the axle upwards and have checked everything for play and notchiness, I cannot find anything wrong. The number of reports on head shake shows this is definitely a common theme, something in the K100 design is at least very marginal if not completely wrong. Cornering above 80MPH is also a very interesting test of character on mine, accelerating round each corner really helps settle the bike but it is still far from being totally under control.

Rick G - don't all K1100s have a couple of extra tubes from the headstock to the first "cradle"? Was that added later?

Snod Blatter wrote: don't all K1100s have a couple of extra tubes from the headstock to the first "cradle"? Was that added later?

On the LT's it was from 07/93 (-94 year models).

I travelled quite a few miles on the motorway one night, 4000rpm/100kmh/60mph, hands off, just leaning left and right using only body weight to follow the curves. No shakes, followed the line of the road perfectly. A bike should be able to do that if its set up ok and you are riding within specs too. I did have the top box and panniers on.

Inge K. wrote:On the LT's it was from 07/93 (-94 year models).

Ah okay, did BMW give any reason for that change at the time? Are those later bikes known to be any more stable than the earlier ones?

As long BMW did make this change, I would guess they did find out it was needed.

If giving it some extra throttle will lessen the effect then I would be looking at the tyre first, tread wear or pressure which as CF said will make for bad wear patterns. Once the wear pattern has been set by an under inflated tyre it will continue to wear like that and there is not much you can do about it except put a new tyre on or ride it as is till the tyre is finished.

I rode with an under inflated rear tyre and it started to scallop and even though I inflated it to the correct pressure it still was bad. I ended up just getting rid of it because of the noise it made. It was a dual compound tyre and it only took 350km to do that.

Thank you all for the good advices  .

I decided to change both tires..easy things first  .
My local bmw shop will change both tires and check front and rear rims about unbalance. ( both Bridgestone bt45 and balancing wheels for about 250 euros).They also had metzeller me800 but those would cost about more 100 euros If that doesn´t do it, i´ll check the bearings on the rims and the on the fork.

But do you really think a bike with low mileage like mine could have damaged bearings on the fork?

RicK G wrote:None of my Ks has done that. I can take my hands of the bars and ride for miles with the cruise control engaged and the 93 K1100 is exactly the same frame as the K100.

From years of fixing bikes that have had accidents, if it is shaking its head then there is something wrong with the geometry.

Check the fork tubes for straight, triple clamps for twisted, steering head for a slight twist the swing arm for laying over and twisted and alignment of front and back wheels.  Your steering head only needs to be bent so that the bottom of the front wheel is 2-3mm out of line with the centre line and it will shake like a dog shitting razor blades.

Use a plum line to check for the wheels being vertical when at centre.

You dont´t have shimmng problems while using cruise control, but in my case, the bike was in decel as soon as i removed hands from the grip. Should that have something to do ?

One should not equate "Low Mileage"  to suspension related issues.  If you think about it, the bike has SAT unused for long periods (or the p.o put the miles on 1/4 of a mile at a time).  On either stand, the weight is on the bearings and springs.  Weight + Time + lack of use = compression of spring length in the forks and flat spotting of bearings.  Additionally, grease or lubricants bound in the bearings, head stock and steering damper, depending on model, dries out.

That will usually make it worse but for it to do that in the first place means there is something not right. Putting new tyres is a good start.
As for a bike with low miles that means very little. I have seen bikes crashed on the way home from the dealer after buying them. You don't know the history, only what the previous owner chooses to tell you.

RicK G wrote:That will usually make it worse but for it to do that in the first place means there is something not right. Putting new tyres is a good start.
As for a bike with low miles that means very little. I have seen bikes crashed on the way home from the dealer after buying them. You don't know the history, only what the previous owner chooses to tell you.

Yeah, i absolutelly agree with you.

I like to think that the previous owner never had accidents, but you just never know..
My bike doesn´t have steering damper, ( i dont know if any k75s has), but ill wait on the tires and the ill say something.

thanks for the help

psoares87 wrote:My bike doesn´t have steering damper, ( i dont know if any k75s has)

Every K75 has a steering damper.  It's the Fluidblok system built into the stem. Inside the steering head downtube is a tubular assembly with special grease between its moving parts.  This unit grips the stem and screws on the outside of the downtube walls fastens it to the downtube.  It performs the same function as would an externally mounted steering damper.  The fluidblok looks like this:

You'll see it if you remove the forks and peer down the steering head downtube.  In Post #6 above, Inge was alluding to replacing the grease in this unit.

psoares87 wrote:

RicK G wrote:None of my Ks has done that. I can take my hands of the bars and ride for miles with the cruise control engaged and the 93 K1100 is exactly the same frame as the K100.

From years of fixing bikes that have had accidents, if it is shaking its head then there is something wrong with the geometry.

Check the fork tubes for straight, triple clamps for twisted, steering head for a slight twist the swing arm for laying over and twisted and alignment of front and back wheels.  Your steering head only needs to be bent so that the bottom of the front wheel is 2-3mm out of line with the centre line and it will shake like a dog shitting razor blades.

Use a plum line to check for the wheels being vertical when at centre.

You dont´t have shimmng problems while using cruise control, but in my case, the bike was in decel as soon as i removed hands from the grip. Should that have something to do ?

You could very well have a point there. I was able to travel quite a few miles by leaning body weight to steer the bike and not bad effects. As for BMW modifications, if it was made in 1993 then the previous frame ran for 10 years and would not have done that f there was a problem.

Don't expect low mileage to mean no problems. Lack of use creates often worse problems, especially in seals etc which can dry out due to non use. A good example are fork seals and corroding stanchions.

I haven't tried hands off decelerating because many years back found that this did cause a problem.

robmack wrote:

psoares87 wrote:My bike doesn´t have steering damper, ( i dont know if any k75s has)

Every K75 has a steering damper.  It's the Fluidblok system built into the stem. Inside the steering head downtube is a tubular assembly with special grease between its moving parts.  This unit grips the stem and screws on the outside of the downtube walls fastens it to the downtube.  It performs the same function as would an externally mounted steering damper.  The fluidblok looks like this:

You'll see it if you remove the forks and peer down the steering head downtube.  In Post #6 above, Inge was alluding to replacing the grease in this unit.

Oh my!!
i thought you guys were talking about an external steering damper ( i´ve noticed some k100 rs have those) but i had no idea i had these on my steering head.
I guess if tires and balancing of rims won´t do it, i´ll probably go to this next.
thanks for posting the picture!! it helped a lot !!   

P.s- By the way, what kind of grease should i get to lubricate these?

Inge K. wrote:New silicone grease in the steering damper could also make a difference.

Do you know any particular brand?

psoares87 wrote:P.s- By the way, what kind of grease should i get to lubricate these?

The grease that BMW did use isn't available anymore....as an alternative some have used Liqui Moly 3312 silicone grease.

But first examine your old damper, they are often damaged from the screws
which should lock them to the frame......the newer type is more solid.

A new damper is packed with grease from factory.

http://www.bmwmoa.org/forum/archive/index.php?t-27340.html  for a discussion about Fluidblok grease substitutes.

The grease they discuss at moa is the same type as this.............
very expensive, NOK 250,- + VAT for 100 grams  ~20 years ago   .

Hello all!

So, my problem is solved. . .changed both tires and balanced the rims.. .throttle the bike till 60km/h, hands off and. . .voilá. . straight as an arrow. .

Thank you all for the support!

Perfect result.

As you can see the K is sensitive to having he tyres correct. Did you go for the Bridgestone BT45?

I did some miles at the weekend, first time I had a pillion on the K and we covered a few nice miles on some lovely roads.

I really notice the need to the rear pressure for carrying pillion but perhaps that was all the steaks 88KE and myself went through over the weekend......

Yeah, i changeg tires to bridgestone bt45. .
The previous tires i had were metzeler, but i only realized how bad they were once i placed the new ones side by side with the old ones. They were really worn in the middle section
 ( i think the previous owner only rided straight forward   )