No top cap or expander

[jamesbass]

Hi,

Just out on a ride with someone who has never had a top cap/expander. He claims it's "not needed as long as the stem is installed properly".

I was inclined to agree but, If this were true, why do all these WW bikes I see use them? It's just dead weight...

Thoughts?

[grouk]

the expander and top cap is only utility is for perfect fit the stem and the bearings, after all perfect fit you could take of. i am now using a tune gum gum expander only for anchor the top cap bolt

[AJS914]

Most people probably keep a top cap because it looks finished.

I tried to fit one of those J&L (Extralite copy) expanders and it would shrink small enough to fit inside my C59 fork.

[Calnago]

Once the top cap has been used to set the preload on the headset bearing, and the stem has been tightened, the top cap itself is not needed. But the expander bung or whatever is in there that the top cap screwed into is a whole different story. Most manufacturers have pretty explicit instructions where they want that support to be, be it in the area where the stem bolts clamp or in the area where the top headset bearing meets the steerer or both (some of these expanders are quite long). Some are short, some are long, some are actually meant to be epoxied in the inside of the steertube. The only way I would not use one is if the manufacturer specifically advised not to or states that is unnecessary. Are Canyons like that? But then you still need a system to apply some preload to the headset. Some Acros headsets with the "wedge" underneath the stem allow for this, but that tiny little bolt is prone to loosening up and then you have a loose headset.

Really depends on the steertube and it's construction etc. I still like the top cap on there regardless. I would hate a big gaping hole in the top for water to get into. Like was mentioned, it just looks unfinished to me. And the support that a lot of expander plugs provide (not all), is something I'd rather know is in there than not.

[ergott]

DO NOT remove the expander.

[F45]

I'm using the Tharsis Di2 stem which uses a different way of tightening the headset bearings. No expander needed. Is my carbon steerer going to crank n fail?

[AJS914]

No, IMO.

I've seen this debate here several times. Despite some manufacturers, like Cannondale, saying that the expander is required to support the stem I don't believe it is. An expander is not being tightened enough to support compression of the steerer tube and the stem is not being tightened enough to compress the steerer tube. Think about it, if you've compressed the steerer tube with the stem, you've broken it.

I think some manufacturers make this recommendation in order to protect the steerer tube from ham fisted mechanics.

[ergott]

I'm in the camp of follow the manufacturer's recommendations here. Compromising the connection between my hands and the bike is not something I'm prepared to gamble with.

Too many other ways to lose weight on a bike, like pouring one ounce of water out of one bottle (about 30g).

[mattyNorm]

If you don't need any sort for internal support for a seat post I could see it not being needed for a steerer. Sure the forces are higher but they are distributed over a much bigger area (area a seat clamp contacts vs a stem).


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[shimmeD]

I remove both, and use a bar end cap with a little bit of electrical tape to friction fit. Manufacturers issue all sorts of warning: I chose to ignore this one.

[Derf]

If you don't need any sort for internal support for a seat post I could see it not being needed for a steerer. Sure the forces are higher but they are distributed over a much bigger area (area a seat clamp contacts vs a stem).

Unless, of course, the respective manufacturer(s) of the stem, steer tube, frame, and seat tube all optimized their wall thicknesses appropriately for the predicted forces.

[kgt]

There are really light top cap/expander combos in the market so not using anything makes no sense IMHO.

[kkibbler]

My bike effectively comes without any top cap or expander (Canyon and their Acros expanding bearing cover). After cutting down to a conventional bearing cover, I use an expander to set the preload, then replace it with the original friction-fit top cap when I'm done.

That said, maybe Canyon forks are designed to have the stem clamped on without internal support. It's unlikely but possible that other brands' steerers have thinner walls that require an internal expander.

[mrgray]

i too have seen this debated numerous times and sometimes with much vigour! in the case of my colnago the top cap and expander is 56 g. these are cheap grams to lose but on the other hand i take various poster's point which amounts to "even if you can, is it worth it?". also it is unsightly and does collect sweat and water. various parties have opined that it is not necessary to resist clamping forces via the expander plug and there does seem to be some logic to this.

it is great to see this come up and see different opinions on this sometimes controversial issue peacefully co-exist. so far.....

[jamesbass]

Thanks for the responses.

The stem clamping forces thing is always the argument I've heard for keeping it in, but would a super-lightweight expander even generate enough force to stop a large tube of carbon from being crushed? If you can crush it, it's too late surely?

Anyway, after trying to install a fork last night without the top cap, I have realized it's extremely difficult to get the headset 100% without it.