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Small amount of rocking in the fork

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Small amount of rocking in the fork

Old 07-22-18, 09:06 PM
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RockyRacc00n
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Small amount of rocking in the fork

I have an old 90 rockhopper. When I put the front brake on and try to move the bike, there is some rocking back and forth happening in the head tube. Meanging, the front tire stays put, but there is some back and forth movement in the fork, as if there is some play room in the head tube. Local bike shop suggested that the bearings might be damaged.


So I removed the stem, unscrewed the lock nut, removed the threaded top race, (I looked up these part names so I hope you are able to follow me. It seems I am not allowed to post pictures). At this point, I saw the ring of bearings. They looked ok to me, but I replaced them anyway and screwed the parts back in the order I took them out. When putting the parts back I made sure to tighten them down tight (without over tightening). I noticed that the threaded top race should not be too tight, otherwise the fork would not turn. So I did not make that too tight. But I made sure the lock nut was tight. And finally, I put the stem back on.


After everything was put back together, I tried the samething. Put the front break on and tried to move the bike back and forth. The amount of rocking seems to have been reduced, but there is still some amount of rocking happening. I am wondering if this is normal, or if there is more that I need to do? Do I need to remove the part that I saw where the bearing were sitting on and replace that? Not sure what that part is called. Could it be there there is some play room in there that is causing the small amount of rocking?
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Old 07-22-18, 09:19 PM
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Brake, not break.

Check that the brakes are bolted to the fork tightly.
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Old 07-22-18, 09:37 PM
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Check whether the rocking is actually happening in the connection between the brake arms and the posts on the fork. If it is, check to make sure that the bolts securing the brake arms on the posts aren't loose. If they weren't loose and the brake arm was rocking on the post anyway, then as long as it's subtle you're probably fine; cantilever and v-brake arms rocking slightly on their posts isn't unusual.

Last edited by HTupolev; 07-22-18 at 10:23 PM.
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Old 07-22-18, 09:59 PM
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I always like to start a headset adjustment with a tad of slop/rock. It can be hard to tell if a bit over tightened preload is present as there's so much leverage that the bars and front wheel can offer the bearings one can still turn the fork (to steer) even when the adjustment is too tight. Starting with a tad of rock and trial and erroring to no slop but still free fork rotation is the best way and what I train those who work for me to do. By turning the fork (and wheels/bars as a headset adjustment is only valid after all is assembled) 90* and repeating the front brake on and rocking fore and aft can offer more data. Especially with suspension forks or disk brakes as both can induce some slop most noticeable when the wheel is pointing straight ahead. If the headset is a tad loose the bike will rock the same amount regardless of how the fork is turned. Now if the headtube/crown seat isn't faced properly, if too many balls are installed, if the steerer is bent or if the headset is VERY BADLY and unevenly worn the amount of rock/slop will vary with the fork's rotational position. Andy
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Old 07-23-18, 08:34 AM
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Originally Posted by TimothyH View Post
Brake, not break.

Check that the brakes are bolted to the fork tightly.

Originally Posted by HTupolev View Post
Check whether the rocking is actually happening in the connection between the brake arms and the posts on the fork. If it is, check to make sure that the bolts securing the brake arms on the posts aren't loose. If they weren't loose and the brake arm was rocking on the post anyway, then as long as it's subtle you're probably fine; cantilever and v-brake arms rocking slightly on their posts isn't unusual.
I see. I have cantilevers and I can see what you guys are saying. I will have to check that.
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Old 07-23-18, 08:42 AM
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Originally Posted by Andrew R Stewart View Post
I always like to start a headset adjustment with a tad of slop/rock. It can be hard to tell if a bit over tightened preload is present as there's so much leverage that the bars and front wheel can offer the bearings one can still turn the fork (to steer) even when the adjustment is too tight. Starting with a tad of rock and trial and erroring to no slop but still free fork rotation is the best way and what I train those who work for me to do. By turning the fork (and wheels/bars as a headset adjustment is only valid after all is assembled) 90* and repeating the front brake on and rocking fore and aft can offer more data. Especially with suspension forks or disk brakes as both can induce some slop most noticeable when the wheel is pointing straight ahead. If the headset is a tad loose the bike will rock the same amount regardless of how the fork is turned. Now if the headtube/crown seat isn't faced properly, if too many balls are installed, if the steerer is bent or if the headset is VERY BADLY and unevenly worn the amount of rock/slop will vary with the fork's rotational position. Andy
You used the term "slop" which makes me think, if there is a term for it, then it's not an uncommon thing. I think you gave some good info here, but I am not following everything you said. I will have to read this again and try some of the things you mentioned. Thank you.
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Old 07-23-18, 08:56 AM
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I too am the owner of a '90 rockhopper.
there was an incident where I slapped on the front brake, folded the fork, and slightly ovalized the head tube. That gave me the feeling you're describing.
that is a possibility in your case.
Its a worst case scenario, so don't automatically jump to conclusions. It is a possibility, and repairable.
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Old 07-24-18, 04:10 PM
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Originally Posted by Andrew R Stewart View Post
I always like to start a headset adjustment with a tad of slop/rock. It can be hard to tell if a bit over tightened preload is present as there's so much leverage that the bars and front wheel can offer the bearings one can still turn the fork (to steer) even when the adjustment is too tight. Starting with a tad of rock and trial and erroring to no slop but still free fork rotation is the best way and what I train those who work for me to do. By turning the fork (and wheels/bars as a headset adjustment is only valid after all is assembled) 90* and repeating the front brake on and rocking fore and aft can offer more data. Especially with suspension forks or disk brakes as both can induce some slop most noticeable when the wheel is pointing straight ahead. If the headset is a tad loose the bike will rock the same amount regardless of how the fork is turned. Now if the headtube/crown seat isn't faced properly, if too many balls are installed, if the steerer is bent or if the headset is VERY BADLY and unevenly worn the amount of rock/slop will vary with the fork's rotational position. Andy
I came back to your post, after checking that my front brakes weren't hanging loose on the fork, as few other suggested that I check.

Reading your post again, I get what you are describing and will try this this weekend.

Question, if the amount of rocking does vary depending on how much the handle is turned, indicating uneven wear, what would be the next step? Replace the entire headset assembly?
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Old 07-24-18, 04:21 PM
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You did verify that it was the headset, right? Suspend the front of the bike off of the ground. It helps to have a repair stand, but you might be able to improvise something if you don't have one.

Take the front wheel off. Grab the *end* of one of the forks where the front axle goes. Feel for play. Rotate the forks and repeat the test as you rotate. If you're not feeling any play, then it might actually be the front wheel hub that's loose.
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Old 07-24-18, 04:27 PM
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I had a Cannondale road bike years ago, that I could never get the front fork tight enough on. If I tightened the headset up enough that I got rid of the rocking, then the headset was compressed too tightly and didn't rotate freely. But, any looser, and i'd get the rocking. After lots of screwing with it, i finally took it to my favorite LBS (who i actually bought the bike from) , and they agreed that something weird was going on with it, and it wasn't able to be correctly adjusted, and recommended i install a new headset, which is what I (they) ended up doing, and it was fine ever since.
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Old 07-24-18, 10:05 PM
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Originally Posted by RockyRacc00n View Post
I came back to your post, after checking that my front brakes weren't hanging loose on the fork, as few other suggested that I check.

Reading your post again, I get what you are describing and will try this this weekend.

Question, if the amount of rocking does vary depending on how much the handle is turned, indicating uneven wear, what would be the next step? Replace the entire headset assembly?
Uneven wear, unevenly faced frame/fork faces/seats and too many balls can result in uneven rock/slop when the fork is pointed straight ahead and at 90*. So next step in my world is to look for bent/misalignment issues and then to try to base line (or blueprint in the auto racing world) the fork/frame interface. Then reassemble a known headset and move on. At any point a stop might be called for, hopefully not. Andy
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Old 07-25-18, 05:07 AM
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Check the bottom end of the head tube for distortion. Bikes with a 1-inch-diameter head tube that are ridden hard off road are prone to "ovalizing" there. I fixed it on one of my bikes using Loctite bearing retaining compound.
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Old 07-25-18, 08:13 PM
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Originally Posted by toast3d View Post
You did verify that it was the headset, right? Suspend the front of the bike off of the ground. It helps to have a repair stand, but you might be able to improvise something if you don't have one.

Take the front wheel off. Grab the *end* of one of the forks where the front axle goes. Feel for play. Rotate the forks and repeat the test as you rotate. If you're not feeling any play, then it might actually be the front wheel hub that's loose.
You're suspecting that the looseness might be where the hub attaches to the fork? I didn't do the test you described, but I'm pretty sure the movement is in the head tube because I looked up close and I could see a slight movement at the bottom of the head tube where the fork enters the frame.

Originally Posted by Brocephus View Post
I had a Cannondale road bike years ago, that I could never get the front fork tight enough on. If I tightened the headset up enough that I got rid of the rocking, then the headset was compressed too tightly and didn't rotate freely. But, any looser, and i'd get the rocking. After lots of screwing with it, i finally took it to my favorite LBS (who i actually bought the bike from) , and they agreed that something weird was going on with it, and it wasn't able to be correctly adjusted, and recommended i install a new headset, which is what I (they) ended up doing, and it was fine ever since.
Noted...

Originally Posted by Trakhak View Post
Check the bottom end of the head tube for distortion. Bikes with a 1-inch-diameter head tube that are ridden hard off road are prone to "ovalizing" there. I fixed it on one of my bikes using Loctite bearing retaining compound.
"Ovalizing".... I'm thinking that's what happened. I recently bought it used so I don't know its history but I can see how the stopping force could over time ovalize the bottom of the head tube. I just looked up Loctite and I see that its some kind of an adhesive that can fill small gaps. Between what two parts did you fill the gap?
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Old 07-25-18, 09:16 PM
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Ovalization of headtubes when the tires really don't leave the ground (as in jumps) is a very uncommon thing. Using a gap filling LockTite compound isn't wrong if the tube isn't ovalized, But might make removal of the headset a real challenge later on. Ovalization is far down the list I would be checking off. Andy
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Old 07-26-18, 12:44 PM
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Originally Posted by Andrew R Stewart View Post
Ovalization of headtubes when the tires really don't leave the ground (as in jumps) is a very uncommon thing. Using a gap filling LockTite compound isn't wrong if the tube isn't ovalized, But might make removal of the headset a real challenge later on. Ovalization is far down the list I would be checking off. Andy
Ovalizing of the bottom of a head tube is not particularly common but not unheard of, especially for 1" headtubes of bikes ridden at speed (happened to one of my bikes after a couple of years of East Coast singletrack, which is much rougher on bikes than smooth fire trails). In any event, the OP says that this sounds like the correct explanation.

To the OP: I used Loctite bearing retaining compound, which is way up there in strength among their adhesives. I pulled the stem out, used a head tube cup removal tool to pop out the bottom cup (or maybe it just fell out because of the ovalizing; I did the repair about 30 years ago, so I don't remember), painted the cup with enough compound to fill the ovalized gap, and used a headset installation tool to clamp the top and bottom cups in place. I think I left the glue to dry for about 24 hours before I reassembled the bike.
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Old 07-26-18, 02:50 PM
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Originally Posted by Trakhak View Post
Ovalizing of the bottom of a head tube is not particularly common but not unheard of, especially for 1" headtubes of bikes ridden at speed (happened to one of my bikes after a couple of years of East Coast singletrack, which is much rougher on bikes than smooth fire trails). In any event, the OP says that this sounds like the correct explanation.

To the OP: I used Loctite bearing retaining compound, which is way up there in strength among their adhesives. I pulled the stem out, used a head tube cup removal tool to pop out the bottom cup (or maybe it just fell out because of the ovalizing; I did the repair about 30 years ago, so I don't remember), painted the cup with enough compound to fill the ovalized gap, and used a headset installation tool to clamp the top and bottom cups in place. I think I left the glue to dry for about 24 hours before I reassembled the bike.
I'm going to check more thoroughly this weekend. It's possible that I didn't do a good job of putting the lock nut and the threaded top race correctly. I am going to adjust that more and see what else I can learn from the process. The idea of putting on Loctite... I don't know that I know enough to try to do that. Last resort, I will take it to a bike shop, but hoping to figure things out myself.
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Old 07-30-18, 08:58 PM
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Just want to post an update. It had to do with the threaded race not being tight enough. I was becoming loose because the lock nut wasn't tight. And if I try to make the lock nut tight enough then the threaded race turns with it, making fork not steer. I have a proper 32mm cone wrench on order so that I can hold the threaded race in place while I get the lock nut tighter. Yeah... simple newbie mistake. Learned after few trial and error.
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