Advice request - steerers and stems =]

[raidan73]

DIY is the way to go in this situation, as you're not looking to shim between two standard sizes. Think cut up Coke cans, thin sheet metal, foil tape etc

 

[SquirrelStu]

DIY is the way to go in this situation, as you're not looking to shim between two standard sizes. Think cut up Coke cans, thin sheet metal, foil tape etc

=D Perfect, thanks there is a load of coke cans round here so I will give that a go! really appreciated =]

 

[2manyoranges]

Yep those measurements are a recipe for slipping stem. Good call on having callipers to hand.

Adrian votes for shim and it’s worth a punt.

Do you have any other stems to play around with? Reason is this...why on earth would this happen, if it’s the original stem and steerer? Could be that it was loose and has worn due to movement - unlikely, but possible if someone undertightened it and kept twisting it back whilst semi-tightened - that can wear away soft stem alloy very quickly. Could be that they butchered it during some servicing - I have seen people do Very Weird Stuff due to brain fade or ignorance.

 

[SquirrelStu]

Yep those measurements are a recipe for slipping stem. Good call on having callipers to hand.

Adrian votes for shim and it’s worth a punt.

Do you have any other stems to play around with? Reason is this...why on earth would this happen, if it’s the original stem and steerer? Could be that it was loose and has worn due to movement - unlikely, but possible if someone undertightened it and kept twisting it back whilst semi-tightened - that can wear away soft stem alloy very quickly. Could be that they butchered it during some servicing - I have seen people do Very Weird Stuff due to brain fade or ignorance.

haha - I just hope it wasn't me in that case xD

The thing is when, I got it a couple of weeks ago, it looked almost unused I dinged the top tube the other day (much to my annoyance and dismay) but have only been on 2 rides with it (it's lovely to ride though - good old days!).

I'm wondering if it was like this from new and that's maybe why it wasn't really ridden. But if it has hardly been ridden, then I can't see another explanation for how the stem got that way.

Maybe it's had a harder life than I'm led to believe - or the stem is a switcher from a more battered bike. I guess there's loads of explanations.

Yep yep - shim, I'm going to go that route first then, let's see.

Any science based problems from sticking a coke can to a steel steerer (assuming it's steel)?

Thanks guys, you're all awesome! I learned so much in these few hours =D

 

[KermitGKona88]

I have a theory as to why this is happening... Wait for it Kermit C. Clarke moment coming... I think it has to do with the design of the DiaTech headset which removes the starfangled nut and uses a clamp and a plastic bung in the top of the steerer. This leaves the steerer unsupported where the stem clamps, it would probably not take much for an ape with a long allen key to start to deform the steerer thus weakening it until when you clamp the stem it just deforms the tube rather than clamping it. I would suggest that along with using a shim that you insert a starfangled nut to support the tube too and this means you can use a nice top cap too.

 

[SquirrelStu]

I have a theory as to why this is happening... Wait for it Kermit C. Clarke moment coming... I think it has to do with the design of the DiaTech headset which removes the starfangled nut and uses a clamp and a plastic bung in the top of the steerer. This leaves the steerer unsupported where the stem clamps, it would probably not take much for an ape with a long allen key to start to deform the steerer thus weakening it until when you clamp the stem it just deforms the tube rather than clamping it. I would suggest that along with using a shim that you insert a starfangled nut to support the tube too and this means you can use a nice top cap too.

Thanks Kermit - I agree, I just order a nice top cap and nut - so that's sorted too =]

 

[2manyoranges]

Good call KGK - made me think - I hadn’t considered that issue of internal support to the steerer.

 

[Gtpulse]

I do think there’s something in the design of the headset being an issue - consider someone not familiar with the design or operation of a headset noticing some play then hulking on the stem bolts as it’s the only obvious thing to “tighten up”!
It’s not a design I’m familiar with but a quick read and it’s the bolt on the cable hanger part that I think gives the preload to the bearing, not obvious to me before I read this thread.

I always went on the assumption that the star fangled nut/bolt/top cap doesn’t serve a purpose once it has preloaded the bearings and the stem tightened up but I’m open to being further educated!

 

[Splatter Paint]

Badly made, out of spec stem? As stems are cheaper than dentistry, I’d humbly suggest a replacement stem rather than shimming an over-tightened one.

 

[KermitGKona88]

I do think there’s something in the design of the headset being an issue - consider someone not familiar with the design or operation of a headset noticing some play then hulking on the stem bolts as it’s the only obvious thing to “tighten up”!
It’s not a design I’m familiar with but a quick read and it’s the bolt on the cable hanger part that I think gives the preload to the bearing, not obvious to me before I read this thread.

I always went on the assumption that the star fangled nut/bolt/top cap doesn’t serve a purpose once it has preloaded the bearings and the stem tightened up but I’m open to being further educated!

You are correct about the star fangled nut in theory if you were a totally nutty weight weenie you could remove the top cap and bolt... 'In theory'