Steering Bearings Preload Check

[AZJW]

 

Repost of great write up by @jdub53 saved here for easy reference.

 

6 hours ago, electric_monk said:

Would you mind explaining how to set/measure the preload on the bearings?

 

From the OEM's T7 Shop Manual; Periodic Maintenance, p. 3-2, item 14, the steering bearings are to be checked for looseness at 600 miles and then at every 6,000 miles. Screen prints provided below (sorry if these are unreadable, but I don't know how else to embed pdf pages into a post).

 

 

 

The adjustment procedure is on pp. 3-19 & 3-20 in the shop manual.

 

 

 

 

Although I followed the T7 manual's bearing tightening procedure, I still follow the procedures I was taught 39 years ago by a very experienced BMW mechanic for checking looseness/proper adjustment and determining if the bearings are already damaged. This has served me well on every motorcycle I've owned since that time (not applicable to BMW Telelever bikes though). Disclaimer: These are the procedures I use and assume no liability or responsibility for anyone else attempting to use these procedures.

 

Static check:

For preload - With the bike's front end clear of the ground (front end complete with wheel/tire/brakes, etc.), if the bars/forks fall fast and effortlessly all the way to the stop on either side the bearings are too loose. Properly preloaded bearings should fall to either side more slowly, and if they fully stop on their own during the sideward fall the bearing preload is too much. Subtle but noticeable differences.

 

For damaged/indented/notched races - With the bike's front end clear of the ground, if bad enough the damage may be felt as light notchiness when moving the bars back and forth.  

 

Dynamic check:

For preload - While riding on a straight, level and smooth road at about 40 mph, take your hands off the bars and as the bike begins decelerating punch one end of the handlebars. With properly preloaded steering head bearings the front end will immediately stabilize and continue straight. If the bearings are loose the front end will begin to oscillate and not stabilize - Warning: This could progress to a tank slapper and it should go without saying but KEEP YOUR HANDS NEAR THE GRIPS THE ENTIRE TIME AND THEN GRAB THE BARS AGAIN. 

 

For damaged/indented/notched races - While riding at a parking lot/walking pace and with your hands lightly on the grips, on a smooth, level hard surface the front end should track perfectly straight. If the bearings are damaged, the front end will 'hunt' slightly back and forth as the rollers pass back and forth over the indentations in the races. 

 

When setting steering head bearing preload on many bikes, beware that when the proper tension is reached (raised front end falls slowly to either side), tightening the lock nut on top of the adjustment nut can alter the tension so be sure and recheck for proper tension then and readjust if necessary. Tiny movements of the adjuster nut make the difference between too loose, correct and too tight.

 

Hope this helps.