The official BMW R90S Owners Club page

Adjusting Steering Head Bearing Preload On An R90S

by Mac Kirkpatrick

SYMPTONS that tell you this job is needed:

Sloppy steering, the handle bar tends to wobble too much from side to side in turns, and the handlebars go from side to side too easily (this is subjective). The problem is that as you ride your R90S, this symptom sneaks up on you and it is easy to not see or feel it.

There is no interval in time or miles for performing this job as so much depends on the quality of the bearings that are installed, and the “kindness” of the roads you travel. The more bumps you hit, and if your bumps are severe the harder it is on the bearings.

The steering in our R90Ss is like you have just the roll from a roll of toilet paper and hang it vertically. This roll is the very front part of our bikes main frame. On the top and bottom of this roll there is a bearing and race which allow the front wheel to turn right and left and through which our front steering is attached. These bearings must be tightened periodically to take up any slack, but just like the porridge in Goldilocks and the three bears story, the bearings must be “not too loose and not too tight, but just right.” There is a nut over the top bearing that is adjustable up and down to put just the right amount of pressure on the two bearings.

Basically our steering head bearings are just like a set of wheel bearings, but the steering head bearings are vertical.

The most difficult part of this job is the “subjective” part of knowing when enough preload has been applied to the bearings. You sense this by turning the handlebar from side to side while the bike is on its center stand and “feel” how the handlebar turns. It should be smooth but not too easy or floppy.

START by tilting up the seat and putting a cloth over the corner of the seat cowl so it does not scratch the gas tank as you remove it. Do not skip this step  even if you think you are good or in a hurry.

Remove the tool kit, tool tray and the gas tank, (turn off the petcocks!). Support the removed gas tank carefully with blocks of wood and cloths so weight is not on the plastic fuel petcocks or they may break and you may scratch the paint on the bottom of the tank.

Using a Phillips screw driver, remove the steering damper black plastic adjuster and protective rubber cover that is below it.

Loosen the 2 large Allen bolts on the lower triple clamp that go around the fork tubes just under the turn signal stalks, so the triple clamp can move as pressure is applied to the steering head bearings when you tighten the nut that applies pressure to the bearings.

Using the flat closed end 37 mm wrench from your tool kit, loosen the dome shaped nut that is under the dampener adjuster. Once loosened, you will not be able to remove this nut or the 37 mm wrench as they will interfere with the handlebars; that is OK. You just want to access the notched ring nut that is below the dome shaped nut. (The dome nut is a protective cover and jam nut for the ring nut, which does all the work.)

Using the spanner wrench labeled 40/42 from the tool kit, tighten the steering head bearing nut by hitting the spanner wrench with a hammer after inserting the spanner wrench in an appropriate notch in the ring nut. Normally very little is required, maybe just 10 or fifteen degrees.

“Enough” tightening is a feel thing, but you want the handlebars to not swing from side to side too easily by themselves.

If the bearings are too loose, the handlebars will swing too freely.

If you feel a slight “notchiness” or a slight “on-off then on” feeling as you swing the handlebars, unfortunately you need to replace the steering head bearings. The bearings sit in one spot on each race as you steer forward, and they tend to indent the race, causing a notchy feeling. You have to “feel” for this notchiness.

Tighten the dome nut back in place, tighten the Allen bolts on the lower fork by the turn signals, and re-install the other parts you removed. Be careful to not scratch the gas tank on the corner of the seat cowl!

This is not a difficult job to perform mechanically; the hard part is feeling how the handlebars turn as this is very subjective, and whether enough pressure has been applied to the ring nut.

NOTES: The plastic nuts that hold on the gas tank should have washers between the nut and the gas tank. Often these washers are easily lost but they protect the paint and help keep the nuts from loosening by themselves.

And putting a little grease on each fuel petcock before installing the fuel lines will make the fuel lines easier to remove the next time. It is not fun when the fuel lines do not cooperate coming off.

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