Jump to content

steering damper


beamergirl

Recommended Posts

Firefight911

A steering damper acts like a shock absorber does. It controls movement of the handle bars from side to side.

 

The prime use of a steering damper is to dampen head shake. This typically manifests itself under hard acceleration when the steering becomes light.

 

It also helps to dampen head shake in situations where there is a steep head angle. This can be imagined by taking the forks and placing them in a more vertical plane. This tends to cause the handle bars to be much more sensitive to both rider input and road imperfections. Best thing to do here is look at a modern sportbike (i.e.; GSXR, R1, etc.) vs. a modern day cruiser (i.e.; Harley)

 

As for play, there really should not be more than a few millimeters of movement in the bars before you start to feel the 'resistance' of the damper.

 

In my old K1200RS, I noticed an increase in play and traced it back to a leaking damper. Replaced under warranty.

 

Another issue that can arise is from a damper that has air in it. This can be felt under high heat days (Willow Springs). This can cause an increase in the resistance. This will feel the same as if your steering head bearings are too tight. Your steering will tend to feel vague and the bike will tend to wander a bit.

 

Hope this helps and answers your questions. Let us know what else you need!

thumbsup.gif

Link to comment
beamergirl

Hi Phil,

 

Thanks for reply, guess I understood it from the research done, but was wondering about the play the actual steering damper has if you grab it and move it from side to side; should it have freedom of movement??

 

Haven't gone back on the bike, but this is what happened:

 

Hit pothole, bent rim, sent rim out and was fixed.

 

Rebalanced wheel, heavy spot had changed and was duly noted.

 

Tire was remounted (Mets w/red dots = light spot and this was aligned with heavy spot on rim).

 

Rebalanced w/valve stem and cap in/on, air pressure checked. Weights added equally to both sides of rim. Held tire at 9 and 3 o'clock, not movement.

 

Reinstalled wheel, compressed front end of bike, everything retorqued, yada..yada...yada.

 

Took out for test run and in a nice wide left turn at @ 60-70 mph it felt like bike was wobbling from side to side - kinda scared me a little as I found myself running out of pavement, ran wide.

 

Went down in speed, and flicked bike side to side - no problem - DID not retry at higher speed, turned around and came home, parked bike and haven't back on it to recheck - kinda bummed.

 

I have to admit I was tired, cold and aching from working around the house, but don't think that really has too much to do with it.

 

SO, what ye say?

 

I'm confused.gif

 

De

Link to comment

Ok so I read all of this stuff and now I get to a point of minor understanding. So I decide my steering damper is bad and I buy an adjustable damper. Installation is easy, so now how do I know that I have adjusted it correctly?

Link to comment
ShovelStrokeEd

This will vary a bit from bike to bike and rider to rider but it has worked for me on all my bikes.

 

Get the bike propped up so the front wheel is off the ground and disconnect the steering damper. Turn the bars from side to side and get a feel for the amount of friction you have.

 

Now reconnect the damper and do the same. When turning the bars slowly, you should feel little or no change. If you try to turn the bars rapidly, there should develop a definate resistance to movement.

 

The damper on my 1100SBX failed (seizing) and I just took the thing off. The bike had been steering a bit funny, felt like low air pressure in the front tire, and I couldn't pinpoint the source. I do get a little head shake now on bumpy corner exits when really on the gas in first or second gear but it is nothing that can't be dealt with and the bike actually gives me better feedback without it.

 

I ran two dampers on my drag bike but that was more to help with the nearly stationary front wheel coming back to the ground and quite often not perfectly aligned with the rear. That bike would carry the front wheel till about 90 mph and then dance it, just skimming the pavement, up to about 120. eek.gif

 

BMWs, in general, have pretty conservative steering geometry and shoudn't really need a damper. I think the one on my S was there just to give a more racy look to the bike. Might even be necessary with slicks on it but, I don't contemplate that kind of duty, nor am I capable of riding it that hard.

Link to comment
beamergirl

Took the wheel back off and rebalanced, seems to be better. Only question now is should a bike track to one side or the other when you let go: Took a ride on I88 and got up some speed, let go and bike seems to want to track to the right. dopeslap.gifdopeslap.gif How do I correct this?

Link to comment
ShovelStrokeEd

Mostly corrected by sliding your butt a little left on center on the seat.

 

You might check your rear wheel for a shim between the wheel mounting surface and the final drive. If one is there, try removing it.

 

BMW seems to think that a few MM of difference between the center line of the front and rear wheels is not a real issue and it probably isn't. It can cause a little fork lift type steering when under power though my old turbo K100 has been well over 170 mph and the wheel offset there is on the order of 1/2".

 

I suspect it is more of a weight issue on a K bike. All the really heavy stuff, crankshaft, final drive, swingarm, etc is located to the right of centerline on the bike. It doesn't make much difference with hands on the bars but they do tend to want to fall to the right a bit without some steering help. Some have even found it gets to the point of fatigue what with having to maintain a little left bar pressure all day on long days. I never really had much issue with mine when I owned it so it may vary a bit from bike to bike.

 

On the K100's you could also shim the motor mounting system to change the angle of the rear wheel a bit and that allowed some adjustment to eliminate the problem. Not sure that applies anymore with the K12 series with their cast frames.

Link to comment
beamergirl

Thanks Ed, really appreciate the response.

 

Didn't even think about the final drive/shaft, etc all being on the right dopeslap.gif

 

Had rear wheel off before, what would this kind of shim look like?

Link to comment
ShovelStrokeEd

You are up early and my response is late but, it is a thin metal disk with a hole pattern that matches the bolt holes on your wheel. There are a couple of other holes in it sometimes but I don't think they matter. Some bikes have them, some don't, although all of mine came with one.

Link to comment

That spacer should be in ALL 5" wheels, but some 5.5s need it, and some (later ones) not. Mine was installed with the spacer, and started oscillating like crazy around 80 mph. Removed it, and was 90% better. The 5.5 wheel has a bit more offset than the 5 incher (to clear swingarm), so it'll never feel the same, but if you didn't compare them back to back (like I did), you'd never know. It just oscillates a bit more when following semis, but nothing objectionable. A lot of GT owners complained about handling problems with their bikes, when it was just the idiosyncrasy of the 5.5" wheel.

Bottom line: ride your bike to 100 mph (on a track, of course dopeslap.gif) with and without the spacer, and it'll be pretty obvious if you should keep it or not.

Link to comment
JerryMather

Brian T, who has a GT and I were both talking about your oscillating front ends when we were riding to Torrey. While I was behind him at speed, 90mph and above, his bike would oscillate from side to side. My 98 KRS would do the same above 100mph.

He told me that his old KRS did the same thing.

So........If he has a stock 5.5" wheel and it does it and I have the stock 5" with a spacer, do you think mine will clear up by removing the spacer too?

Both of us are running the Pilot Roads.

Link to comment

ALL K-bikes should have that shim installed bewteen the final drive carrier and the rear wheel. Here is a recent posting from Paul Glaves.........

 

Instead of speaking in veiled terms lets add some clarity here. It is important to our health, safety, and welfare. It is a shim (BMW calls it a "spacer ring - 2mm") sort of a washer, and is also asserted to be a device which increases the friction between the wheel and the final drive output shaft. This technical argument arose during a (guess what?) - lawsuit in a case where an improperly fastened rear wheel fell off the motorcycle at speed. That specific case involved a wheel with the five bolt pattern using the center hole for a 5th bolt. The four outer bolts were (probably or arguably) improperly torqued and they all loosened and became unattached. They stayed in the wheel cavity because of the hub cap.

 

The rotary motion of the output shaft served to tighten the single center bolt a bit at a time until the stress exceeded its strength and it snapped causing the wheel to become completely disconnected from the rest of the motorcycle, while going down the highway at considerable speed. The resulting crash was catastrophic - fatal I believe.

 

It has been a while since I read the specific particulars of the claims of the plaintiff's and defendent's attorneys in this case. I have quite frankly forgotton whether the spacer as friction modifier was a claim of the defendent manufacturer/servicer or of the plaintiffs. Given the legal nature of this tragic event I would not suggest that a person ought to remove the spacer. I would observe that this specific failure would not occur if all of the wheel bolts were properly torqued and the outer 4 bolts remained in place. Rotary slippage of the wheel would neither loosen nor tighten the four outer bolts. Vibration might loosen them, and then they might shear, but shear strength of the 4 outer bolts would be controlling - not whether the friction at a given clamping force was modified by a spacer. I would further observe that the specific failure without warning of the 5th bolt retaining the wheel for a little while would be non-applicable with a 4 bolt pattern.

 

I would add that the propensity of the K series bikes to pull right has little to do with wheel alighnment and a great deal to do with the distribution of weight left-right. Divided down the center line between the two contact patches, the right side of the motorcycle weighs more than the left side of the motorcycle. That is a matter of final drive, swingarm, driveshaft, transmission shaft, and crankshaft placement. Removing the shim does move the contact patch slightly to the right, placing a slight amount of weight on the left instead of the right of that line between the contact patches. But the motorcycle is still considerably heavier on the right than on the left. About 10 pounds in the left saddlebag vs your sleeping bag on the right side pretty much cures the imbalance. But I have never seen a naked K75 which wouldn't pull right on level pavement in a still wind condition. Weight is weight and physics is physics. And moving the wheel 2mm compared to where the final drive, transmission shafts, crankshaft, etc, are located on the bike has a minimal effect.

 

If you believe that the effect on handling is outstanding, and the arguments that the roughened surface of the spacer serve to provide increased friction at a given clamping force are just lawyer hooey - then by all means be my guest and remove the spacer ring, but do so understanding what the issues are or may be.

 

Paul Glaves

 

p.s. 77 ft.lbs. is your friend!

 

Mick

Link to comment
JerryMather

OK......Removing the spacer isn't the answer to stopping the ocillating problem at speed.

So what is ? The tires were new at the start of the trip and properly inflated, as per BMW recommendations, 36 Front / 42 Rear with very little weight in the city bags and the flat type lids on.

Link to comment
OK......Removing the spacer isn't the answer to stopping the ocillating problem at speed.

So what is ? The tires were new at the start of the trip and properly inflated, as per BMW recommendations, 36 Front / 42 Rear with very little weight in the city bags and the flat type lids on.

 

What does BMW reccomend for a maximum speed with luggage? On the R1150RT it is 80mph.

 

Andy

Link to comment
NoLongeraK1200RSRider

Gosh oh golly gee Batman.. I came back from Jackson Ca at speeds around 135 to 140 (only when the road was clear of course) on my previously wrecked '99 K12RS and brand new Metzlers with NO noticable shake.. tremor.. or any other ill handling manifestation.. should I do something to ensure that this doesn't happen any more? dopeslap.gif lol. I do have the "HyperPro steering damper" fitted and run it on the median setting.. so maybe that helped? confused.gif Thanks for any input. wave.gif

Link to comment
JerryMather
What does BMW reccomend for a maximum speed with luggage? On the R1150RT it is 80mph.

It's the same for the KRS. frown.gif

 

I know that a lot of folks over here with these bikes don't restrict themselves to that number while on road trips. They have their side bags loaded with the large lids on and they still don't have this problem.

Maybe an aftermarket damper is the answer.

Link to comment

Hey Jerry; sorry for the delay. Yes, ALL 5" wheels need that spacer in there. If you remove it, it'd only make matters worse. Only the 5.5" might need it or not, and the high-speed test would tell your buddy which way he should go; it only takes a few minutes to remove and replace the tire (make sure your buddy refers to the manual for the torque value and sequence).

As for your oscillation, my bike was absolutely rock solid with the 5" wheel, even with the crappy stock tires (D220s). As a comment, I noticed the slight oscillation after the wheel swap almost went away when I replaced the D220s with the Conti Attacks. And after feeling a bit more instability with the tires wearing out, I pumped up the pressure from 38/40 to 40/42 (and am always by myself, and weigh just 155 lbs), and the bike immediately felt just like when tires were new. The K is a very heavy bike to have the front tire at 36psi IMHO, so pump that sucker to 40 and leave the rear at 42. Test ride it WITHOUT bags, and see how it feels. Then go with the bags and see if you feel a difference.

I can speed at triple digits with the bags on, but as I said in the past, my bike handles really weird above 90 mph with them if it's even a bit windy (it always is around here), so I avoid sustained speeds above 90. Besides, my fuel mileage goes down the toilet under those conditions anyway.

Let us know how it goes buddy. Good luck.

Oh, and check your wheels for balance too.

Link to comment
JerryMather

Is there any difference in performance between the Wibers and the HyperPro steering dampers for the KRS's?

They both look alike and their cost is about the same, $340.00 ?

 

HyperPro

Link to comment

I'm the buddy Jerry was talking about. I normally run 40psi front and 42 rear unless 2 up then up the rear to 44 psi. The bike is rock solid without sidebags at any speed. Add the side bags and 90+ starts oscillating, especially in dirty air around trucks or breezy conditions. I've just chalked it up to an aerodynamics issue with the bags, but I'm really hoping it's something else that can be fixed instead of just staying below 90 when I'm on a trip. I do have the 5.5 inch rear wheel, but not sure if it has the spacer in it or not.

 

After watching Jerrys rear wheel dance around I'm not sure a new steering damper would help at all. Although it feels like the front end is oscillating back and forth, I think it really is the rear wheel bouncing around that gives you that oscillation feel. It's similar to when I got a rear flat under speed and I couldn't figure out what the hell was wrong with the front end of the bike as it oscillated. Got off the bike and saw the flat rear tire and realized there was nothing wrong with the front end. dopeslap.gif

Link to comment

De,

Did you check the front tire after the mishap? If it's damaged (ie, cut cord) then you might get the problem you described in the turn.

 

The damper is really there for the rare occassion of a tank slapper or the more frequent possibility of hitting an object or hole in/on the road. It does a marvelous job of reducing bar shakes quickly - damhik. Depending on the miles on your bike, it may be a candidate for replacement. Many owners are describing a change is warranted in as little as 20,000 miles.

 

Since you didn't have this issue prior to the bent rim, I'd be looking at a replacement front tire.

Link to comment

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...