strange headset adjustment

Steve said:

Hi Everyone, I replaced the stem on my new mountain bike (ahead) and I noticed that the headset was
a bit loose, so I torqued it according to mfg. spec (22 in-lbs) and tightened down the stem. When
tightened down, the headset appears to become looser. I can hear this as well as see slight motion
in the spacers above the headset. When I loosen the stem (without touching the preload cap) the
play goes away. To get the headset to an acceptable adjustment, I need about twice the recommended
preload. Adjusted in this fashion, there doesn't seem to be excessive friction, so I don't think
it's too tight.

Anyone ever seen this? could something be going on with the stem (change in geometry when
tightened)? I'm tempted to just leave it, and toss the headset if it eats itself due to excessive
preload. I've already checked the cap clearance, etc.

Any sage advice would be appreciated.

Thanks,

Steve.

This does not happen to be a welded aluminum stem?

If you set the stem on a flat surface, you may see that the stem does not sit flat. You may notice
that there is a difference at the "gap" that the pinch bolts tighten. This makes the headet load
crooked when tightened.

Common among "sale" welded aluminum stems (aka rejects). Whent they weld the stem together, the
expansion and contraction due to the intense heat of welding distorts the material.

You can take a file and make it flat again, but you also need to be sure to keep it square with the
steerer tube. A little filing, a little checking, more filing...soon enough it will be good to go.

G

GregR, Thanks, I suspected as much. The stem is an inexpensive forged weyless stem from supergo. If
it's still too loose after the last adjustment I'll look into modifications.

Thanks again,

Steve.

GregR said:

Steve said:

Hi Everyone, I replaced the stem on my new mountain bike (ahead) and I noticed that the headset
was a bit loose, so I torqued it according to mfg. spec (22 in-lbs) and tightened down the stem.
When tightened down, the headset appears to become looser. I can hear this as well as see slight
motion in the spacers above the headset. When I loosen the stem (without touching the preload cap)
the play goes away. To get the headset to an acceptable adjustment, I need about twice the
recommended preload. Adjusted in this fashion, there doesn't seem to be excessive friction, so I
don't think it's too tight.

Anyone ever seen this? could something be going on with the stem (change in geometry when
tightened)? I'm tempted to just leave it, and toss the headset if it eats itself due to excessive
preload. I've already checked the cap clearance, etc.

Any sage advice would be appreciated.

Thanks,

Steve.

This does not happen to be a welded aluminum stem?

If you set the stem on a flat surface, you may see that the stem does not sit flat. You may notice
that there is a difference at the "gap" that the pinch bolts tighten. This makes the headet load
crooked when tightened.

Common among "sale" welded aluminum stems (aka rejects). Whent they weld the stem together, the
expansion and contraction due to the intense heat of welding distorts the material.

You can take a file and make it flat again, but you also need to be sure to keep it square
with the steerer tube. A little filing, a little checking, more filing...soon enough it will
be good to go.

G