spectastic

i found out the hard way that without any spacers between the stem and the top cap, then you shouldn't use a star nut on the carbon steerer, but a compression plug. However, my cervelo 3t funda team carbon fork is built weird, in that it has an aluminum sleeve bonded to the inside of it. It has a 21 mm inner diameter. most compression plugs for 1 1/8 are 23-26 in diameter, and won't fit my steerer. Should I buy a compression plug for a 1" steerer to make this work? If a 1" compression plug does work, would it need a different top cap that fits the 1 1/8 steerer?

ingo

On the Cervelo fork the aluminum sleeve is there to hold the star fangled nut. What happened to your fork steerer tube that prevents you from using the existing star nut or replacing it with a new one within the aluminum sleeve?

spectastic

i'm trying to raise my stem such that there is no spacers above my stem, in order to obtain a more favorable seating position. I was careful to not make the stem too high from the top of the steerer, and still have enough room to accommodate the top cap. but when I tighten it, I noticed that the top bolt was compressing more than the bottom nut. I did not want to torque it down like this, because I've already cracked a steerer tube doing this. it's pretty clear to me at this point that an expander plug is needed, if I want to put my stem on the top of my steerer.

ingo

I'm not sure that the expander plug will help since you are intending to run the stem above the top of the steerer tube and the plug will not fully support the tube from the inside. Without a spacer, the top cap will need some room below the top of the stem to fit. Not that it matters, but I have my S2 stem installed without a spacer (using the star nut) and it is OK after some 13,000 km. Another possibility is to get a stem that has only one clamp bolt, such as the 3T ARX II Pro. I'm using one on my S3 and clamping is not a problem with the single bolt. I guess the other possibility is to flip the stem to get the bars higher without moving the stem higher on the fork.

McBTC

...the aluminum sleeve does not go to the top of the carbon steerer tube so it's crushing when you tighten the top stem bolt?

DrIsotope

The sleeve for the Cervelo fork comes with a star nut in it, and the sleeve is to be epoxied in place after the steerer is cut to length. It should also have a star nut in it, so if it doesn't... where did it go? You can only run ~40mm spacers below the stem, if I recall the fork manual correctly. This is the part I don't understand:

spectastic

I'm not trying to run the stem above the steerer tube. I'm just trying to put the stem right below the top cap.. and I'm talking about a 5 mm spacer under it. The steerer is a little short. I'm finding that if I put the stem right below the top cap, and try to tighten it, the top stem bolt is clamping more than the bottom bolt..

Sy Reene

Change the 5mm spacer under the stem to a 2.5mm spacer?

DrIsotope

I'm trying my best, but still have absolutely no idea what that means. How is the top bolt on the stem "clamping more" than the bottom one? It's a CF steerer, you should be using a torque wrench or Torqkey. Per the Cervelo manual, the top of the steerer tube should be at least 3mm below the top of the stem, so that the top cap doesn't hit the lip of the aluminum insert.

If by "top stem bolt" you mean the bolt through the stem cap-- and that it is bottoming out, allowing the stem/fork to still rotate, then the stem is too low and needs a larger spacer underneath it.

dsbrantjr

The only thing I can think of is that the OP's top stem clamp is closing further than the bottom i.e. smaller gap. But only a guess.

TimothyH

Cervelo steerers are supposed to use the aluminum sleeve with a star nut. I know two people who have used a compression plug instead. The Specialized plug is long and very supportive inside the steerer. It is $10 and worth every penny.

https://www.amaincycling.com/special...4-2010/p691196

If the aluminum sleeve is bonded into place then you can't use the compression plug. You are stuck with a star nut.

Using a star nut, if the top cap sits directly on the stem then the stem will need to extend 1mm to 2mm above the steerer. Adjust spacers under the stem so that this is the case. It should look like the photo below with the steerer just below the top of the stem.



Use a torque wrench to tighten the stem bolts. If the top bolt on the stem is crushing the steerer then STOP - my guess is that you are completely over tightening the bolts or the aluminum sleeve is too far down into the steerer to support the stem, or both. The aluminum sleeve should go to the top of the steerer. If it doesn't then another piece can be added.


-Tim-

fietsbob

Fabricate.. machine a solid aluminum plug just the right diameter ,

and thread the center in the 6 by 1 mm bolt standard, simple lathe job.

Epoxy it in place..

the usual carbon steerer a star nut is Verboten ..
but as a workaround that aluminum sleeve lets you hammer one in ..


and so alternatively, simpler tools needed..
Take the star nut to your bench grinder

keep it cool,
quenching in water often to not remove the spring temper,
is a consideration .

take a little bit off the ends of the star edges..

[Math] Assuming they were made for a 22.2,, ID,
that's like 1.1mm off each end edge..

chuck a bolt, You screw into the star nut , into the drill-motor
cause it to spin in the opposite way from the grinding wheel rotation

and you are more likely to keep all the metal removed, equal...




...

spectastic

this

spectastic

my current setup looks something like that, except no spacers under the stem, and I would like to bring the spacer on top to be below the stem. I am using a 5 nm torque wrench, but the stem bolt on the top part of the stem is compressing more than the bottom bolt, which is already at 5 nm. the top bolt isn't anywhere close to 5 nm, and it's already screwed in further than the bottom bolt..

DaveSSS 

See my post on how to completely fill the clamp area with epoxy.
Ongoing fork plug loosening saga...
The only problem with this is that you already have a star nut in place. I placed foam rubber into the steering tube first, to limit the area filled with epoxy. When done right, the steering tube can be extended quite a bit.

My other comment is that you don't need to tighten the top bolt that tight. I've never used a torque wrench of any type to tighten a bolt to 5Nm.

Here's another thought. If you install a bolt with extra length and use some masking tape or a drinking straw to mask off the threads, you could use epoxy plumber's putty to stuff the whole top of the steerer full of putty. Once that hardens, there's no chance of cracking the steerer.

spectastic

no need to do anything at this point. was able to get a -10 deg stem from a friend to replace my -17 deg stem. brought my bars 1 cm higher. pretty happy with my new position compared to before. thanks for all the input. will consider for future if needed.