Headset

DESCRIPTION AND DIAGNOSIS: (C, R, M) The headset is the set of bearings that holds your front fork to the rest of the bike frame and allows the front wheel to steer. The steering column at the top of the fork goes up through the head tube of the frame, and all of those bearing parts (see Figs 4-1 and 4-2) of the headset go around the fork tube. There may be some variation of parts on your headset, such as a special lockring with Allen set-screws, or seals on the bearing races, or interlocking teeth on the washer and the top threaded race, but the general layout will be the same.

(M) Most mountain bikes have a stem that slides over the top end of the steering column and acts as a locknut. These bikes have a top race that is not threaded, as shown in Fig. 4-1. The locknut/stem makes it easy to remove your fork, which is nice if you have a shock fork and need to remove it for lubrication and overhaul. Threadless head sets also make for a much more reliable interface between the stem and the steering column.

Fig. 4-1 Threadless Headset

Fig. 4-2 Standard Headset

(C, R, M) If your steering action gets unresponsive, or you hear clanks or grackly crunchy noises and feel looseness in your front end as you go over bumps, your headset is probably loose. Lift the front wheel off the ground a few inches and drop it; if you hear a clank, the headset is loose for suit. To test for more subtle headset looseness, apply the front brake fully, push down on the handlebars, and rock the bike forward and back. Can you feel a sort of slippery-shifty looseness or see that the front fork is shifting back and forth in relation to the frame? These symptoms indicate a loose headset, too. Just to make sure the problem is with the headset and not the fork (especially a shock fork) or the wheel, rest the front wheel on the ground and try to wiggle the tire from side to side; if the fork slops and wiggles side to side, your shocks are shot; if the wheel wiggles, you may have loose front wheel bearings or a wheel that is loose in the fork. For either of these problems, see the Hub PROBLEMS section.

(C, R, M) If your steering action becomes rough or sticky, and you notice that the bike is a little hard to balance when you are going slow, the problem is probably that the head set is stiff.

PROBLEMS: (C, R, M) Headset loose. If you have noticed a clanky or wandering front end and used the diagnostic tests above to determine that your headset is loose, here is the way to snug it up.

First see if you can turn the big top locknut counterclockwise a turn or two to loosen it. Try doing it by hand. If it has Allen screws set into the sides of it, holding it tightly in place, loosen those with an Allen key, then loosen the locknut. If you have a stem/locknut unit, see the headset loose procedure.

(C, R, M) After you have loosened the locknut, tighten the top threaded race by hand. If the headset is loose, you should be able to do this easily. You can often do it even if you couldn’t manage to loosen the locknut. When you have the threaded race as tight as possible, apply the front brake and rock the bike forward and back to see if there’s still any looseness lurking in there. If so, tighten the threaded race some more, rocking the bike to and fro or turning the handlebars as you tighten, to make sure you are snugging up the race on the bearings as much as possible. When the headset is snug, tighten the locknut down by hand, too. If you have the proper wrench for your headset locknut, tighten the locknut thoroughly. If you are out in the open country and don’t have a tool, just hand-tighten the locknut. That will hold it there for a while. If you go over a lot of rough terrain, you may have to retighten the headset by hand again before you get home. When you do get home, don’t forget to adjust the thing carefully again, then tighten the locknut very thoroughly with the proper wrench.

(C, R, M) You may even need two wrenches, one to hold the threaded race still, and the other to tighten the top locknut. A big channel lock wrench and a huge crescent wrench will work if you don’t have proper headset wrenches.

If you have a lot of trouble with the tools you’ve gotten hold of, don’t knock yourself out or mash up the threaded race or the big top locknut in the process. Take the bike to a good shop. They will have the right tools to do the job. Also, if the headset is an aluminum one, you might want to replace it with a steel headset. Aluminum headsets have a reputation for looseness.

(M) Threadless headset loose. All you have to do is loosen the binder bolts that cinch the stem onto the top of the steering column, then gently tighten the adjusting Allen bolt at the top of the stem. CAREFUL: it’s easy to over-tighten it and mess up the plastic cap or the springy spider-nut that are pulled towards each other by that adjusting Allen bolt; all you want to do is snug the stem down on the bearings. Rock the bike forward and back gently with your weight on the bars to test for looseness. When the headset is snug, tighten the binder bolts thoroughly, and you’re set to go.

(C, R, M) Headset tight. Either the bearings are dry or tight, or the steering column may be bent. Look at the front end of the bike from one side. Does the front wheel look cocked back further than it should be? Have you slammed into a log or rock lately? Taken a bad end-over spill (flipped over the front)? Try steering the handlebars all the way to the right as far as they will go, and then all the way to the left. If the headset gets stiffer at either extreme, you can almost bet you have a bent steering column. They are hard to straighten, but if the bend is severe and your steering is really bad, see below for a way to get the fork pulled out straight.

(C, R, M) If the steering column is straight and the only problem is that the bearings are dry or dirty, get a bit of lubricant worked into the headset. Turn the bike upside down and squirt it in, using the little application tube if your lubricant comes with one. If the bearings aren’t sealed, it’s easier to lube them; I remember squeezing mayonnaise from those packets you get from fast-food places into a headset once. Worked like a charm for the rest of the ride. But if you do any stop-gap lubrication on a ride, make a mental note to do a complete overhaul of your headset when you get home, using proper bike grease and the procedure below to make sure you get it all right.

(C, R, M) If a standard headset is just too tight, you have to try to loosen the top locknut, then loosen the top threaded race just a bit (one-eighth of a turn or less), then tighten the top locknut. You need a headset spanner to do this properly; the one you get with a Cool Tool will work if the top locknut isn’t really tight. If it is really tight, you may have to struggle along with your stiff steering until you can get to a farm or something, then borrow a big adjustable wrench to loosen and tighten your top locknut. Do adjust that tight headset as soon as you can, though; a tight headset feels horrible when you try to correct imbalance by steering, especially when you’re picking your way through a slow, technical section of trail. If you don’t believe this, just try riding no-handed with a tight headset.

(C, R, M) Headset overhaul. Start the overhaul by laying the bike down on its left side with a clean white rag under the headset. Remove the front wheel.

(C, R, M) If you have a standard stem, loosen the ex pander bolt that’s on top of the stem two full turns, then tap the bolt head with a hammer to un-wedge the stem inside the fork tube. Twist and pull the handlebars to get the stem out. If you have enough brake and gear cable slack, turn the handlebars to one side and lash one end to the down tube with an old inner tube or something. Remove the front wheel if you haven’t already. Then loosen and re move the top locknut.

If you have a locknut/stern type of headset, loosen the binder bolts on the stem, then hold the fork so it stays in the frame, as shown in Fig 4-3, then loosen the adjusting Allen bolt that’s on top of the stem, all the way, so you can take the stem off the top of the steering column.

Fig. 4-3 Holding Fork in Headset

(C, R, M) No matter what kind of stem you have, the next step is to either unscrew the top threaded race, or slide it up off the steering column if it isn’t threaded. Then you can slide the steering column of the front fork out of the frame. Take the bearing rings off the races, observing carefully which side of the bearings has the solid ring. On almost all bikes, the bearings will be in retainer rings; if they aren’t, take the loose balls out of the races and count them, NOW, so you’ll know how many go back in there. After you have the bearings off the bike, check for thin little sealer rings that fit around the outer edges of the smaller bearing races in each bearing set. Take these sealer rings off care fully and note which way they fit around the races; they often have a special “stepped” profile so they fit around the edge of the race and stay put. You have to make sure you put them in the same way they came out.

(C, R, M) Clean all the bearing surfaces and the ball bearings with a soft, clean rag. Check the surfaces for pits, roughness, or cracks. Replace any bearing or race that is not shiny smooth. You may have to get help from a shop to re move and replace the set races or the fork crown race; they’re often hammered tight into place, and you need special tools to get them off without bending them and/or dam aging the frame tubes.

(C, R, M) When you have clean, smooth bearing parts, put some waterproof grease on the ball bearings, then put the lower bearings on the fork crown race, making sure you have the retaining ring for the ball bearings on the correct side (up or down) so it won’t rub on the races. Slip the sealer ring around the race (if you have a sealer ring), and push the fork back into place in the frame. Then put the greased top set of ball bearings in place (add the sealer ring too, if you have one), and either turn or slide the top race onto the steering column.

(C, R, M) Now, if you have a standard stem, put your lock rings or washers back on the steering column, turn the top locknut down to them, then adjust the headset, as de scribed in this chapter. When it’s adjusted and the top lock nut is tight, you can put the stem back in, line up the handlebars, and tighten the stem’s expander bolt.

(M) If you have a locknut/stem headset, you have to hold the fork in place while you slide the locknut/stem unit onto the steering column. Then you gently tighten the adjusting bolt until the headset is snug. Then align the stem so the handlebars are straight in relation to the front wheel, and, finally, tighten the binder bolts.

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