Headset play

richardjallen

For a while I've noticed that if I apply the front brake while stationary I can still rock the bike forwards and back very slightly. If I apply the rear brake at the same time the bike does not move a millimetre. At first I though it must be due to the brake calliper being lose. Then I just thought it maybe the fork/headset. Sure enough if I hold the top of the headtube where it meets the headset I can feel play.

Is this normal? Is it bad? Should I do something about this?

oldwelshman

There may be some play in the forks but the bearings should have no play.
You can always tighten them a bit and make sure you can turn handlebars easily but have no bearing play when rocking with front brake applied.
You will no if they are too loose if descending, you will have a job to hold on with one hand and do not try no hands if you want to stay on bike

franklin pierce

richardjallen wrote:

Is this normal? Is it bad? Should I do something about this?

No, yes, yes.

(Tighten your headset.)

(How you do this would depend on what sort of headset you have.)

Jashin

On a related note, how tightly should the bolt in the expander bung in a carbon steerer be tightened? I'm worried about overtightening this, but I got home from a ride yesterday and the headset had developed some play, so I guess the bung wasn't tightened enough.

richardjallen

Ok so how do I tighten the headset?

I removed the cap on top so I could get to the bolt. The bolt was hand tight already, I could not tighten it much further and there was not difference in play. I removed the bolt and a metal pin came out with it. Beneath the pin I could see a circular plastic component that filled the steerer tube and at the centre was the thread that the bolt went into. Again there was no difference in play and I replaced the pin and top cap.

Zendog1

What you have to do first is slack off the bolts on the aheadstem (the forward pointing thing the barrs fasten on to). Then tighten the headset bolt until the play goes but the the wheel still turns smoothy. Then retighten the aheadstem.

richardjallen

This is a lengthy post but I've just spent about 1.5 hours this morning sorting this play out and thought I would share what I learned. What an ordeal! The stem was off, headset was out, the fork was out!

I learned several things this morning. The fork is carbon with a carbon steerer but an alloy crown. The component under the top cap is I believe a fork expander. Not a star fangled nut as it would dig into the carbon. Tightening the fork expander in itself does nothing to keep the fork in the frame. Instead tightening it expands the component so it grips the inside of the fork. I can remove the fork with the expander still in place and did so. I'm glad as well because there was a bit of grit inside near the fork crown I also poked around in the head tube.

Previously suspected my carbon frame was perhaps a carbon alloy hybrid wrapped in carbon. The seed of doubt is now gone. The head tube was completely carbon and the joins to the down tube and top tube were nothing but carbon. It has the texture of fibre glass on the inside btw.

After much fiddling I put replaced fork with the two halves of the headset in place and put the spacers and stem back on. The problem was I could no longer get all the spacers on and I had succeeded only in making the play even worse! Then I realised the top headset cup was the wrong way up. I flipped it over and it seated further into the headtube leaving more space on the steerer for the spacers.

I replaced the spacers and took the opportunity to swap two around so have about 2.5mm less spacer below the stem than before and the bars are slightly lower. I thought I would try this and maybe lower them further later, now I know how. Stem went back on.

Now the expander thing. Much fiddling with this. At first I thought it must be to expand the steerer so that it grips the inside of the headset. No. The top cap needs to screw into something and it screws into a thread on this. The expander expands inside the steerer and grips that. Then when you screw the top cap into the expander it holds in place. I did not know what this was all about to start with and it slide all the way down into the steerer and I could not get an Allen key down to tighten it. I had to keep turning the bike upside down to shake it loose. Then I had it in place but it was too far down for the top can to reach the thread!

So what keeps the fork firmly in place then? I think its a combination of the stem and the top cap! The stem prevents the fork moving up and down because its clamped to the steerer and obstructs this but its ability to do this depends on how firmly you gripped everything together when you clamped it on. However as you tighten the top cap it pulls more thread on the expander into itself, therefore pulling the expander up. The expander grips the inside of the steerer so you are effectively pulling the fork up as you tighten the top cap. This means the expander must be sufficiently tight inside the steerer to prevent it slipping up the steerer as as the top cap is tightened.

I have removed the play, removed doubt about the integrity of my frame and know how to lower the bars. There's only one thing that worries me now and that's the two washers that were beneath one of the headset cups got bent up in the process and I did not put them back in but they did not seem to contact with anything anyway.

I'm guessing this is a non-integrated ahead headset.

bikeit65

Richard check here
http://www.parktool.com/repair/readhowto.asp?id=68

blackhands

The top cap and expander is only meant to take up the slack in the headset bearings - ie to make the necessary adjustments with the stem bolts not tightened. When the headset is properly adjusted then the stem bolts are tightened and it is these which hold everyting together - you could safely leave off the top cap after this with no safety consequences. Do not tighten the top cap once the stem is tightened - all you will do is pull the expander plug up the fork column.

richardjallen

blackhands wrote:

The top cap and expander is only meant to take up the slack in the headset bearings - ie to make the necessary adjustments with the stem bolts not tightened. When the headset is properly adjusted then the stem bolts are tightened and it is these which hold everyting together - you could safely leave off the top cap after this with no safety consequences. Do not tighten the top cap once the stem is tightened - all you will do is pull the expander plug up the fork column.

Ok so it is just the stem that holds it all together not the cap as I had thought. So is the expander plug there only to screw the top cap into? I did realised that tightening the cap could potentially pull the expander up through over tightening. I think overall I managed to do this correctly, although I did it the hardest way when all I had to do was loosen the stem bolts and tighten the top cap :oops:

I understand now why you need to loosen the stem bolts before tightening the top cap. Surely it is how I first thought that when you tighten the top cap it pulls the fork up a bit and takes up any slack. If the stem bolts were tightened then the stem would prevent the fork moving up and instead the expander would be pulled up inside the steerer.