I'm completing a build, and i have one final thing to do.

I have worked out the correct stack height for my fit. However my stem now sits below the compression plug that is currently in there. So i need to get my steerer tube trimmed at my LBS.

my question is:
can i safely ride to my LBS (with my stem below the compression plug) without damaging anything?
it is a short ride (7km)

or would y'all recommend i just walk it over / take it on the subway?

thanks,

Do you have a carbon steerer tube?

yes. carbon fork/steerer tube. (columbus minimal)

Ride it over. Tighten the stem clamp bolts enough to keep it in place but don't go nuts with the torque. Once the steerer has been cut to the correct length, torque the bolts to spec. The reenforcement of the compression plug is a useful safeguard but not essential for many forks.

...how many spacers above the stem right now?

great. thanks. carbon scares me.
currently I'm 1 newton metre below the recommended torque. I'll ride it over, and re-torque once it's all done.

quite a lot. 30mm above. 20mm below stem.

so the stem is way below the compression plug so worrying about cracking the steerer tube is justified...

yea it's nowhere close. ugh. maybe i'll just play it safe and walk it over.

I disagree with those who recommend riding it over.

Carbon layup in steerer tubes is vertical, top to bottom, and they have great resistance to bending loads. There are usually no fibers running around the tube horizontally and so the tube has little resistance to crushing loads.

Slight pressure from the stem in an area not supported by the compression plug or slight pressure from the compression plug in an area not supported by the stem can deform (expand or crush) the tube significantly. It is very easy to deform the steerer tube to the point where it begins to crack by doing this. Loads from riding only exacerbate the risk.

A compression plug 30 mm above the stem means that a significant portion of the steerer is unsupported. Don't risk riding it.


-Tim-

10 minutes long but definitely worth watching. It explains expansion plugs and steerer tubes very well and shows a vivid example of how they are easily deformed.



-Tim-

I don't need it, so I stick with safe, steel.

+1, steel is real.

I understand some companies add a metal liner to a carbon fork steerer, once it is sized.. so it can better resist the stem clamp forces.

If your cables are long enough, you could put all the spacers under the stem and clamp the stem at the top of the steer tube just long enough to ride to the shop.

Reviving this oldish thread.

So, I ended up walking the bike over to get it trimmed
It’s all good.

One more question:
The fork I’m using is a Columbus minimal 1”
I’m using a shim inside the 1 1/8” stem, with 1” spacers.

My Columbus minimal fork came with a really nice Columbus top-cap (with a nice dove graphic) that I would really like to use. Except, it’s a 1 1/8” top-cap ... it came with the 1” expander plug I bought from Henry-James. Go figure.

The fork recommends a 5mm spacer above the stem. So that’s what I’m using.

Could I put a 5mm 1 1/8” spacer instead of the 1” spacer above my stem, and drop my nice Columbus top-cap on there? ... or would that be unwise?

Thanks.

I don't see how that would hurt anything. I'm 'gonna keep an eye on this thread and learn something too. I like the cap that came on my bike so I understand the desire to use it.

Cervelo does this. You have to mix adhesive, smear it inside the steerer and insert a metal sleeve.

An compression plug is not used however. Once the sleeve is in place it uses a regular starfangled nut.


-Tim-

The reason for the spacer above the steerer is to assure the stem is completely supported by the steerer with no overhang. That spacer serves no structural purpose so you could use a 1-1/8" spacer if you wish. You will want to keep it centered as you adjust the headset preload but after the stem clamp bolts are torqued properly it won't matter. If it shifts around while riding you could use a thin shim to keep it centered.

So one expects the relatively thick carbon steerer, + your adding the sleeve

gets you in the range of a 1" threadless fork steerer star fangled nut. .. that ID around 22,2mm..


If the liner is long enough you have an aluminum and carbon steerer, which is not bad... belt & braces..


A good machine shop could thread the inside of your sleeve and make a cap of aluminum to thread into it,

the cap being also threaded for the pre load bolt.. then that does the star nut job ..


and offers less weight and more bragging rights..




....

thanks.