Is it steering head bearings?

A little help is needed. The bike is a '94 R100RT.

The problem: When the forks extend suddenly, such as when I hit a pothole or on rebound from hitting buckled pavement, I hear a metal on metal sound. The only way I can describe the sound is that it is similar to tapping two metal rods together. It appears to be coming from somewhere near the top of the steering head but hard to tell for sure. No problems when the suspension is compressing, only when it extends.

The forks have recently been serviced. Nothing inside was in need of replacement except for the fork seals. The springs are factory. I think 10 wt oil was used.

With the bike on the center stand and no weight on the front wheel I can detect no movement, no slop, when the forks are moved side to side or front to back. Everything seems tight. I notice no problems in riding. Steering seems to be just as it always was. The front suspension operates as expected when on the freeway or in town. I cannot find anything else that may be loose.

I have not had a chance to do much except have a quick look at the Clymer to see what may be inside the steering head. There may be a part other than the bearings that has worn and needs replacement.

I suspect the steering head bearings are either loose or need replacement. It may not take much wear to cause slop and thus produce the noise I hear.

It could be nothing more than the bearings needing a bit of tightening. I have heard that this may be all I need.

Your suggestions/comments are appreciated.

My thoughts...

As for bearings, try putting the bike on the centerstand, front wheel off the ground, and investigating how the bearings feel. Can you grab the bottom of the forks and physically move the sliders back and forth...noticeably? Check the bearings for notchiness in the straighahead position...not really that could cause the clunk, but a measure of the health of the bearings. Do you feel any notch as you move the bars back and forth through the straightahead position. If so, then the races have been dented.

Try the test of nudging the bars towards the left of right. Do the bars rapidly pick up speed and prang off the stops? If so, then the bearings are too loose. Or do the bars stay in the position you put them...assuming that the cables, etc., aren't providing too much resistance? If so, then the bearings are too tight. Too loose bearings will cause will gyrations in the bars at speed. Too tight bearings will result in a slight weave as you slow down from say 60 to 30 mph.

Do you know how much sag the front forks give you from the full extended position to you sitting on the bike with a full tank of gas? Numbers I've seen are somewhere between 2.5-3 inches. If less than that, it seems like you could be bottoming out on rebound. You want the springs to operate in their middle range.

And the amount of fluid in the forks is the correct amount?

I'm not a supsension expert, but that's where I'd look. Hopefully an expert will weight in...

Since the forks were recently serviced, that is the likely culprit - often a problem is immediately preceded by whatever was done last.
Besides prior post, check for the seemingly trivial dumb stuff like caliper/brake hose mountings, fender mounting, instrument cluster mounting, cable routing, fairing fasteners etc
Depending on the extent of what they did, they may well have removed fairing - which the book says (but i don't) you should do to work on steering head

Check to make sure the top nut on the stem is tight that holds the top plate in place. Although it may seem tight, it may not be tight enough allowing some movement. DAMHIKIT.

This noise was heard before I did the recent fork service. At that time it had Progressive springs, which were too stiff for my tastes. I put up with them for several years but decided to go back to the factory springs. I thought the noise I was hearing indicated that the forks needed some service. Again, no internal damage/wear was seen. The fork oil quantity is per the Clymer manual (I think 300 cc) but those manuals have been wrong before.

I have had several opinions among my riding friends. Over sprung, not enough preload, too much preload, too much oil, too little, etc. Now with the factory springs back in I would think that all internal components are a match regarding rebound damping, etc.

This is very confusing since everything that I can access is tight. However, I have not had a chance to look at that top nut as was recommended.

Calipers are torqued to spec, the fork brace is tight, nothing loose on the instrument cluster, nothing loose anywhere that I can see. I even emptied the storage pockets to make sure something in there was not rattling.

You said forks were recently serviced. Was that just a drain and refill or complete disassembly. I'm not sure I followed that.

My Haynes says the oil capacity per leg for a R100RT '87-on is 320 cc at oil change. It doesn't say but it would be a little bit more if you were to disassemble and fill...maybe another 15cc.

You thought you put in 300cc per leg...not sure how much a difference that might make if it should have been 320 or even 335cc. Might be worth checking out.

This noise has been with me for some time. It is rare but when it happens you definitely hear it.

The forks were disassembled. Several months ago I had the local shop take them apart to see what may be causing the noise. No damaged parts were found, nothing excessively worn. Of course, something could have been missed since I do not expect a shop to know everything about every component.

When the noise continued and with those stiff springs I figured it was worth looking at the forks again. If nothing else I could replace the springs with the factory parts to get the softer ride I was after. I removed the forks and took them to a shop that does suspension tuning. The mechanic said everything looked good inside and he installed the factory springs. I told him the oil quantity and I left the Clymer with him in case he needed it for any reference. He put in 300 cc of 10 wt.

Those rubber boots that close up the fairing exit create enough resistance that I cannot tell if the bearings are too loose. I slowly rotate the bars and I can feel no notchiness, no roughness. Again, with a weight on the rear seat to get all load off the front wheel, I can push and pull on the bottom of the forks and I detect no noise, no looseness.

I will look for something other than forks or steering. There may be a loose component somewhere, I just have to find it.

It could be the bearings, but it could also be the damper pistons bottoming out atthe bottom of the fork tube. Ther are some bikes that had small springs under the pistons toact as shock absorbers for that reason. However, before disassembling the front end again, look for other causes. You might try having another person put their ear closer to the area and try to narrow the focus as you put the bike on the centerstand.

My R100RT Front End

I had been experiencing front end problems that may give you some more food for thought. My metal clunking I heard turned out to be a broken upper fairing mount. While I had this off I was able to more accurately evaluate my steering head bearings. With the fairing and gaiters on I could not really feel what I had. With this stuff off I could feel some drag and the dreaded notch on center of the head bearings. I am currently in the process of bring it all back together after replacing the bearings and having the bracket welded.

Mike in Iowa

Does the bike have Brembo or ATE calipers. The ATE calipers were known to bounce up and down on the attachment shaft. I added phenolic washers top and bottom between the calipers and fork boss to prevent the bounce, which also helped tighten up the brake action.

So, roll the bike forward and grab the front brake. Roll backward and brake. If you hear the metallic clank, it's the caliper mounting.

Different BMW airhead forks had different internals, and some had rubber washers to quell the noise when they extended or compressed fully. Changing the fork springs may have put the dampers closer to the top.

Usually, grabbing ahold of things and appling some vigorous shaking will unearth the culprit. How are your wheel bearings? Fender mounts? etc.

The steering head bearings should be snug enough that with the tire off the ground, the front end will rotate toward the stop by itself over about two seconds, and without banging into the stop or pausing in mid-swing.

It is not uncommon, when replacing tapered roller bearings, for the race to be not quite bottomed. Then, with use, the race finally gets pounded down, but that leaves some bearing slop. Steering head, swing arm, wheel bearings.

It is also possible that a noise from the rear end is being heard up front. So don't ignore the stuff behind the steering head.

pmdave

I think the calipers are Brembo. When I roll backwards in the driveway and apply the brakes, sometimes I hear a metallic click, not a very loud clank or banging sound. More like dropping a paper clip on a hard floor. I doubt that this click is what I am hearing when riding. The sound I hear when riding is louder and resembles, as I mentioned, two metal rods being rapped together.

When the forks were off the bike, we (mechanic and I) pushed on them to simulate compression. Everything felt fine. We then tried to pull the forks apart to see if maybe something was wrong during rebound. We could feel the resistance increase and at no time did we encounter anything that would indicate bottoming out or topping out. We did not feel any sudden stops in either direction, no sticking, etc. However, in a shop setting, it is probably impossible to duplicate the dynamics of the forks that would actually take place on the road.

With the weight of the bike on both wheels, I have pushed on the bars while applying the front brake. I hear nothing, feel nothing out of the ordinary. When on the center stand and a weight on the rear seat to make sure there is no load on the front wheel, I shake the bars left to right, front to back. I hear nothing, feel nothing.

I doubt if it is a problem in the rear. When this sound occurs, it is immediately after the front wheel makes contact with a bump, before the rear wheel makes contact.

I do not feel any looseness in the front wheel when I grab it and shake with no weight on the wheel. However, I have not closely looked at the front wheel bearings. I suppose I could start at the bottom, so to speak, and work my way up, eliminating possibilities one by one.

Have you made a measurement as to how much spring compression you get from fully extended to when you're sitting on the bike with a tank of fuel. I'd be interested to know how far the spring compresses with the dead weight.

88bmwJeff said:

Check to make sure the top nut on the stem is tight that holds the top plate in place. Although it may seem tight, it may not be tight enough allowing some movement. DAMHIKIT.

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me either.

the acorn cap on my bike was loose, allowing the top triple clam to slide around, the bearing pre-load adjuster was tight, so there was not much noticeable "bearing slop"

"ker-klunk" as the top piece slid forward and hit the steering stem under extreme braking or a big pot hole

20774 said:

Have you made a measurement as to how much spring compression you get from fully extended to when you're sitting on the bike with a tank of fuel. I'd be interested to know how far the spring compresses with the dead weight.

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I have not yet made this measurement with the factory fork springs installed. I made this measurement with the Progressive springs and got 1.25 inches of compression with just the dead weight of the bike on the wheels. No rider, no passenger, just the weight of the bike and maybe a half tank of fuel.

I would expect to get at least 2 inches with the factory springs. They are quite a bit softer.

There is a rubber/plastic "doughnut" at the bottom of the fork tubes. Over time it sort of dissolves. When this deteriorates, it looks like a circular wad of dirty grease that's just settled in the bottom of the fork. Used my fingertip to clean it out of the bottom of the forks and promptly got the same sound you describe and new "donuts" was the cure. About a $9 part, plus labor on fork disassemble and reas'y.

26667 said:

There is a rubber/plastic "doughnut" at the bottom of the fork tubes. Over time it sort of dissolves. When this deteriorates, it looks like a circular wad of dirty grease that's just settled in the bottom of the fork. Used my fingertip to clean it out of the bottom of the forks and promptly got the same sound you describe and new "donuts" was the cure. About a $9 part, plus labor on fork disassemble and reas'y.

Click to expand...

What is the year/model of your bike?

I wonder if this rubber doughnut is typical of all forks. I do not have my Clymer handy so I cannot look at the exploded parts view to see if it is there.

The local dealer mechanic mentioned this rubber "cushion" as being in some forks he has seen. However, he made no mention of it as being in my forks and needing replacement. The independent mechanic who last had the forks apart also made no mention of this item. Neither mechanic found anything out of the ordinary inside. So, either the design of these forks does not require this rubber doughnut or if it does, it was overlooked by both of them.

This sounds like a possibility since the problem has gotten worse over time, indicating something that has been deteriorating.

26667 said:

There is a rubber/plastic "doughnut" at the bottom of the fork tubes. Over time it sort of dissolves. When this deteriorates, it looks like a circular wad of dirty grease that's just settled in the bottom of the fork. Used my fingertip to clean it out of the bottom of the forks and promptly got the same sound you describe and new "donuts" was the cure. About a $9 part, plus labor on fork disassemble and reas'y.

Click to expand...

based on my airheads, I think this donut went away with the new Brembo bearing sliders in 1981

mine's a '78. try the Max BMW online parts fiche

Check to make sure the fender is not hitting. Softer springs allow more travel. May have to check to make sure all is adjusted for maxium clearance. DAMHIK

The Max BMW parts fiche drawing and the exploded view in my Clymer appear to be the same drawing except for numbering and nomenclature. Nothing in either is identified as any sort of rubber cushion or bumper. That does not mean it is not there, just that it is not identified as such.

Fender and fork brace are tight. The noise I hear is present with both the stiffer Progressive springs and the softer factory springs.

One thing I have not checked is that large nut on the center of the stem. It is between the handlebar clamps and the only wrench I have to fit it is a large adjustable. The wrench will not fit in the gap between the handlebar clamps. I will have to remove the bars first.