Currently the steerer is cut to run 30mm spacers under stem with a 5mm one on top.
Chris King 1 1/8 no threadset.
ENVE 2.0 forks + Compression plug.
The reason of HakeemT's point is that without proper inner support a light steerer tube often comes with a thin wall which is easily ovalised (if not destroyed) by the pressure exerted by the stem's fixing screws.
Hence his suggestion for the use of a T-shaped bung/topcap that runs from the top of the steerer tube all the way down to the expander proper which is then placed in the area where to lower fixing screw of the stem is.
A not so common system that works well provided the steerer is either cut to precise length to accomodate the T-shaped device which also precludes the use of spacers on top of the stem.
If a long enough expander is used and sits inbetween the fixing screws then no damaging compression could occur. Not sure such a device exist. I doubt it.
Another solution and I feel one that works very well is to use carbon mounting paste between the steerer tube and the stem i.e. put on the outside of the steerer tube which allows to reduce torque on the stem bolts by about 30% which in turn should be low enough so the steerer tube is not ovalised or prone to crushing damage.
In all cases work with the utmost care so the steerer is not damaged. Best to use a torque wrench and go easy on the torque you apply. With carbon paste applied to the tube the chance of twisting or lifting the stem clear off the steerer tube is virtulally non-existant for road use.
Point is, that if a steerer really needed reinforcement from small deformations wouldn't that reinforcement have to extend from the top of the stem to below the top bearing of the headset to truly be effective?
iamalex wrote:I couldn't see anything about max. spacers on top of the stem - I'll check again in the morning though. I read the 1mm steerer above stem and 5mm spacer on top. And a max. of 40mm spacers between headset and base of stem.
Maybe I'm misreading this, but it does say something about max. spacers above stem, namely 5mm.
And fa63, that looks like a fairly common length for an expander; keep in mind that running 40mm of spacers above a stem means you'd need close to 80mm of expander length (i.e spacers + stem stack which often (not always) ends up being in the 40-45mm region); I doubt that the expander pictured is that long.
That being said, as long as it is for fitting purposes only I think you will be OK with running a couple of spacers above the stem for a short amount of time and while doing easy riding. Keep in mind though that 40mm is a big range so if you're that unsure about your position it may take a while longer to dial in the right stem height...
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