How important is Compression Plug / Top Cap Tightness after stem is tightened?

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ms6073
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by ms6073

Sacke wrote:Has anyone here actually broken a steerer tube by over tightening the stem bolts?

Not the stem on a fork steer tube, but 15-16 years ago, I over torqued the seat post clamp while installing a carbon seat post on an alloy frame, resulting in stress risers in the seat post.
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Calnago
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by Calnago

Sacke wrote:Has anyone here actually broken a steerer tube by over tightening the stem bolts?
I didn't put the recommended aluminum sleeve in my Cervelo steerer tube, but just an expander bolt.
Now if some brands say it has a structural support function, I might just glue it in there, just to be safe.

Not me personally, but just the other day a guy brought over a fork where this had happened. I'll see if he's still got it and check to see if the compression plug was too small for the fork.
Also, I have a cervelo P3 and I absolutely expoxied the aluminum sleeve that Cervelo supplied for the fork.

These things often do provide structural support for many carbon steerers. Sometimes even though you loosen the stem bolts, the stem is very difficult to get off until you loosen the compression plug. If the fork is supplied with a compression plug that looks like it might even remotely provide some support or reinforcement to the steertube, I will use it every time.
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AJS914
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by AJS914

It's hard to imagine ever crushing/cracking a steerer tube if you are only torquing the stem bolts to 5-6nm.

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cyclespeed
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by cyclespeed

11.4 wrote: but modern steers require some kind of internal buttressing that goes the full height of the clamping pressure of the stem.


I only have experience of Specialized carbon road steerers, but as I mentioned previously, I had a hard time making any kind of impression on an offcut that I put in the vice.

Manufacturers can never be sure what type of bung you are using, or how much steerer you have above the stem (some are left uncut by a large margin at first whilst a new rider settles in). So they cannot design a steerer that has to rely on the bung. As long as you don't overtorque your stem, I don't see any issues. But the US does have some very good, powerful lawyers......!

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Calnago
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by Calnago

cyclespeed wrote:
11.4 wrote: but modern steers require some kind of internal buttressing that goes the full height of the clamping pressure of the stem.


Manufacturers can never be sure what type of bung you are using, or how much steerer you have above the stem (some are left uncut by a large margin at first whilst a new rider settles in). So they cannot design a steerer that has to rely on the bung. As long as you don't overtorque your stem, I don't see any issues. But the US does have some very good, powerful lawyers......!


I'd say most manufacturers supply the compression plug with their forks and expect you to use it, so from that standpoint they know exactly what type of compression plug you should be using at least. And they generally provide guidelines as to where it should be in relation to the stem, etc. Most fork steerers are pretty strong these days, but if they supply a compression plug, I'd use it unless they specifically say it's not necessary (Canyon maybe?). Any other manufacturers that do not supply a compression plug with their forks?
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Kayrehn
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by Kayrehn

I'll use the original... If it weren't so damn heavy. If an ultrastar can do the job, then the original is an overkill. I've tried crushing carbon tubes with half the thickness of steerer tubes and can't do a thing to it either.

Btw an extralite hyperstem specify a maximum of 4nm torque on the bolts, and if you stick to 3nm as recommended by them I don't think there's a chance of crushed steerer tubes.

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