Hey y’all! I mostly ride frankenbikes and have a hard time committing to modifications that make parts less versatile. Any suggestions for reputable options for longer compression plugs that would allow for some stack variation with a carbon steerer tube? I’ve been running my Crux at the max allowable stack height and would like the option of a racier position, but since the OE compression plug is short any stem position other than at the top of the stack puts the stem beyond the area supported by the compression plug.
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Pro makes a long compression plug. PRO Gap Cap Expander Long | Pro Bikegear
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Thanks a bunch, Greg!
I fully empathize with your plight. I have long plugs I got off of Amazon in a couple of bikes. Maybe Neco brand? Seems well made. Always disassemble to grease the sliding bits before install.
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Origin8 sells one that is 90mm long.
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There’s also this one from Zinn for a more permanent solution as it’s supposed to be bonded into place.
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Super intrigued by this option! I’d love to be able to treat a carbon steerer like a steel one.
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Thanks for the suggestions, y’all!
I’d probably still avoid treating it like a steel one.
Wouldn’t put a stack of spacers like what you see on some Radavist builds for example.
The carbon steerer will still have a different flex characteristic further down, past the insert, compared to a steel steerer. Simply put, when you reinforce a structure in one spot to take a higher stress, then the failure point will move to where the structure is weaker - and that may well be the non-reinforced sections of steerer.
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Great point. Maybe the move is to go for a short compression plug that can positioned anywhere along the steerer tube so that it can always coincide with the stem clamp. Or to just cut the steerer tube like everyone else does :). Thanks for taking the time to help!
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This Deda one is 70mm https://dedaelementi.com/expander-70
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I used the Cane Creek Ancora plug.
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Isn’t that what Cervelo used on some of their forks a while back?
I had the displeasure of working on one of those bikes where the initial installer had been how can I put it, ‘conservative’ with their use of epoxy and the insert started to pull itself out when I tried to preloading the headset bearings.
It was NOT a fun time fully removing it and a job I’d happily never do again.
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I believe they may have had something similar.
I remember that at some point, maybe in 2014-2015 or so, they included a thin aluminium sleeve and a satchel of epoxy to bond the sleeve in once the steerer had been cut.
The sleeve only served as a liner inside the steerer and a regular expander plug was used for the compression.
Obviously if going for a solutuion like the one fron Zinn, one would have to go through the appropriate steps to clean, prep the surfaces, and bond the piece in with the appropriate amount of epoxy.
Best done by someone trusted.
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One thing to consider is the insert diameter range vs steerer internal diameter, which is a function of steerer wall thickness. Not all steerer wall thicknesses are the same - I believe Cannondale beefed theirs up some time after the CAAD12 was released, and the Trek Emonda AL steerer has thick walls.
As an example, my original CAAD12 thin-walled steerer ID measures 23.78-23.81mm. A Specialized insert with a maximum expanded diameter around 24mm would always slip. The long Deda insert with 23.6-24.1mm diameter would also loosen after a few rides on rough roads. This was not a preload path issue. The slippage was fixed with the bonded Zinn inset.
The Deda insert is too wide to fit in a thicker walled Trek Emondo AL steerer. In this case a narrower (22mm) Colnago long insert was needed - it has a similar design to the Deda.
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Do fork manufacturers recommend the plug reinforce the stem clamp?
I haven’t ever thought about that. At a theoretical level, wouldn’t the fork experience the same stress even if there’s a plug behind it? If you look at hoop stress, which is the opposite of clamping force (hoop stress is when the pressure comes from the inside of the cylinder wall, the stem clamps from the outside), the stress is tangential to the cylinder wall. There’s no stress in a radial direction - i.e. where a supporting sleeve would act.
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This. Better quality than most in my experience.
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The tube wall can deform a lot more due to the stem clamping load without the extra internal support. The stem clamp will force the steerer into a non-round shape, creating localized stress etc etc.
All that said, whether or not the fork requires the clamped area to be entirely internally supported (or at all) depends on the fork manufacturer. For instance, Enve compression plugs only support the very top of the steerer. The plug is shorter than most stem clamp heights, and they don’t state that the stem should be at the top of the steerer. Cannondale states that the expanding portion of their plugs overlaps the bottom edge of the stem clamping area, but the entire top section is unsupported. Specialized compression plugs support the top and are something like 50ish mm long, and they state that spacers should only be run on top of a stem for short periods when adjusting for fit, and the steerer should ultimately be trimmed.
I’m rambling now and have forgotten the question…
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Interesting, thanks Greg. I’d like to think a fork should be strong enough to be clamped without a sleeve behind it. And that they are recommending the sleeve just to be safer.
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Most carbon steerers have a max amount of length from the upper headset bearing to the underside of the stem. For example my Ritchey Outback has a max of 30mm. The steerer plug should cover the length of the steerer that is being clamped by the stem. It is surprising how much the steerer bulges when you tension the steerer plug so you are balancing the internal force of the plug with the compression of the stem.
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