stem post won't tighten securely to fork steerer

[petmcgratt]

I have just upgraded my racing bike with a new FSA carbon pro oversize handlebars and the matching FSA oversize stem which fits my 1.18 alloy steering tube. To cut a long story short. I have tightened my stem post using to the 2 screws as tight as they should go but there is still alot of movement. when I secure the front wheel between my legs I can quite easily rotate my handle bars. I out the original stem post back on which fits normal size handle bars and it secures the handlebars fine. also noticed I did not have to tighten the 2 screws as much using the old stem post.
I'm I missing out or should I be doing something different with a carbon pro stem post.

thanks
peter

 

[Gerry Attrick]

When you tighten the screws to the recommended torque, is there still a gap between the clamping halves of the stem? That is the "split" which nips up when the screws are tightened.

 

[petmcgratt]

No there isn't. The split completely closes. How can this be if it is supposed to fit the 1.1/8" alloy steering tube. I know I have gone beyond the recommended torque as the the two screws can not be tightened any further!!

 

[accountantpete]

Check that you haven't got a 1" steerer by measuring it.

 

[petmcgratt]

I definitely have a 1.1/8" stem post which is exactly the same diameter as my old stem post. However, I have noticed that the distance between the splits in the new stem is only ~3 mm whereas the distance between the splits in the old stem is about ~4 mm. Just wondering if the splits are too close together and therefore can't get a tight lock on the steering tube.

 

[Gerry Attrick]

Something doesn't add up here. If the sides of the split are meeting, then either the steerer is undersized or the stem is too big. Just because your old stem fits does not mean your steerer is the right size for the new stem. In addition, by your own admission you have completelt tightened the new stem screws. You could have overstressed the lugs through which the screws pass and bent them in relation to the body of the stem. Could you post a picture of the new stem looking down the steerer tube recess?

 

[petmcgratt]

Not sure if this will work but I've tried to post an image through flickr.

the link is shown below:

http://www.flickr.com/photos/mcgrattanclan/4189008742/

 

[Rohloff_Brompton_Rider]

when you slide the stem on with slack bolts it should already feel snug. you have the wrong size. or a reject one.

 

[Gerry Attrick]

Time to measure the steerer tube very accurately with a vernier calliper. I strongly suspect your steerer is undersized. If not, then you have a duff stem.

 

[Alf]

Bit of a fuzzy picture but it looks as if the stem split is closed up so steer tube too small would seem to be the explanation. You should be able to measure it accurately enough with a ruler across the diameter, at least to tell the difference between 1" and 1.125". Have you mislaid a shim somewhere? Looks like that's what you need, anyway.

Alf

 

[MacB]

Bit of a fuzzy picture but it looks as if the stem split is closed up so steer tube too small would seem to be the explanation. You should be able to measure it accurately enough with a ruler across the diameter, at least to tell the difference between 1" and 1.125". Have you mislaid a shim somewhere? Looks like that's what you need, anyway.

Alf

Yep, have a look in the stem you took off and I reckon there'll be a shim.

 

[petmcgratt]

The diameter of my steering column is 1.1/8 inches (measured from outer edge to outer edge). No matter what it is definitely wider than one inch. I also noticed that the distance between the splits were the two tightening screws are located on the stem post is rather narrow compared to my old stem post. I am thinking that because this distance is so narrow I am not generating enough tension when they meet together to be able to securely fasten the stem post to the steering column. I am thinking that it is a faulty stem post.

when placed onto the steering column it does give a snug fit!!

I have also tried wrapping some electrical tape around the steering column to act like a shim (wrapped tape round twice) but then was not able to get the stem post on. I am trying everything here!!

 

[accountantpete]

If the steerer is the correct size then it must be the stem at fault.

Try the tape on the steerer but wrapped only once round as a short term measure but I'd get a proper fitting stem to be on the safe side.

 

[petmcgratt]

I have taken a better photo of my old stem post (one on the left) and my new stem post (one on the right). You can see they are both exactly the same diameter (i.e. ~1.1/8 diameter) but one difference you might notice is the difference in the clearance between the tightening clamps. The old has a clearance of 4-5mm before starting to teighten the nuts but the new stem has only a clearance of about 2mm before tightening. I think this may be why I am not getting enough torque in the new one when I have to fullt tighten the bolts and why the clamp is completely closing aswell (see my other photo). has anyone found a similar problem with this FSA carbon pro clamp. Could this be a one off or do you think that is the way this stem has been produced as the dealer has suggested I send it back and he will send me out another one. What would be the point if this is the standard clearance in the tightening clamp.


http://www.flickr.com/photos/mcgrattanclan/4190165720/

 

[Gerry Attrick]

Never had any problem with FSA stuff before, but you may have been unlucky. It would be worth getting it swapped.