Talk to me about stiffening up a flexy steerer tube

Discuss light weight issues concerning road bikes & parts.
FastforaSlowGuy
Posts: 85
Joined: Fri Dec 30, 2011 10:02 pm

by FastforaSlowGuy

My existing bar/stem setup is pretty stiff (Pro Vibe 7S), and the new one should be equally or more so (Thomson bars/Zipp SL stem). Where I do get some flex is in the steerer tube. I can see it when I hold the front wheel and twist the bars. Any way to stiffen that up without either (a) adding a bunch of weight, or (b) replacing the fork? The expander in there now is quite large and was intended to stiffen/strengthen the steerer. I thought about replacing it to save weight but didn't want to make the steerer even MORE flexy.
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Seven 622 SLX
Colnago C50 Extreme Power
Zanconato CX

sigismond0
Posts: 236
Joined: Tue Feb 05, 2013 8:29 pm

by sigismond0

There really isn't much that can be done about a flexy steerer without replacing the fork, I'm afraid. Much like you can't fix a floppy stem without replacing it, I think you're just out of luck.

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Stolichnaya
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Location: Vienna, AUT

by Stolichnaya

But this brings up a question - who makes the longest compression plug?

I had an issue like this on a bike and finding a compression plug that went below the stem and the HS top cap helped quite a bit (albeit up top, the fork blades were noodles too. Bummer.)

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N.T
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Joined: Wed Sep 08, 2004 7:13 pm
Location: Finland

by N.T

you are imagining things.
This is weight weenies not stiffness weenies.
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sigismond0
Posts: 236
Joined: Tue Feb 05, 2013 8:29 pm

by sigismond0

Yeah, I don't know how I'd feel about being a member of a website called "Stiffness Weenies"...

On topic: Are you talking about a soft compression plug or a starnut?

FastforaSlowGuy
Posts: 85
Joined: Fri Dec 30, 2011 10:02 pm

by FastforaSlowGuy

To reconnect the original question to the broader mission of the site:

Is the collective "wisdom" that changing from a burly compression plug to a lightweight one will have minimal - if any - effect on the stiffness/durability/etc. performance of my fork?

If so, it seems like a cheap & easy way to drop some grams.
__________
Seven 622 SLX
Colnago C50 Extreme Power
Zanconato CX

Privateer
Posts: 383
Joined: Thu Feb 03, 2011 2:28 pm

by Privateer

If you're sure that the flex is in the steerer tube and not the fork blades or the head-tube/downtube/seat-tube junction maybe you could get Mattias Hellore or someone like that to epoxy another carbon tube inside your steerer?

em3
Posts: 888
Joined: Tue Dec 23, 2008 2:57 pm
Location: NYC

by em3

FastforaSlowGuy wrote: Where I do get some flex is in the steerer tube. I can see it when I hold the front wheel and twist the bars.


OK, but that does not necessarily translate into a flexy cockpit/steertube/headtube when you actually ride the bike. Are you actually feeling flex when you ride...noticable enough to be robbing energy from your forward momentum?

FastforaSlowGuy wrote:The expander in there now is quite large and was intended to stiffen/strengthen the steerer.


The plugs that are epoxied in to your steertube do not stiffen your steer tube, but are claimed to add a bit of internally reinforced strengthening of the steertube to protect agains ham fisted "mechanics" who over torque stem bolts.

Tell us more about the frame you are riding? How many spacers are you using below ur stem? You may also want to double check the adjustment of your headset and make sure that your bearings are properly compressed.

EM3
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FastforaSlowGuy
Posts: 85
Joined: Fri Dec 30, 2011 10:02 pm

by FastforaSlowGuy

I confess that I do not know if the flex is from the fork blades or steerer tube. I'm confident it is neither the wheels nor stem/bars. My basis of comparison is a very rigid fork on my winter/cross bike (Stevens Team Carbon), which just feels much more solid when I pull on the bars riding the same road wheels on the the same roads.

I run about 1cm of spacers under my stem, and there is a conical spacer that I can't recall the height of - maybe 1.5cm? By comparison, my cross/winter bike has 0 spacers and a top conical spacer of about equal height.

If there's nothing to be done, I'm not necessarily bummed. It just means I may try to pull out the compression plug and sub in a lighter one. I'm my own ham-fisted wrench, so if I stupidly over-torque a stem bolt then I deserve a cracked steerer tube.
__________
Seven 622 SLX
Colnago C50 Extreme Power
Zanconato CX

kulivontot
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Joined: Sun May 16, 2010 7:28 pm

by kulivontot

Get another frame set? :noidea:

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dwaharvey
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Joined: Thu Oct 26, 2006 8:54 pm
Location: USA

by dwaharvey

Considering that the typical steerer tube on a fork is about 200mm long I don't think there's any way that beefing up the top 30mm with a thicker plug (or conversely replacing such a plug with a light one like an extralight ultrastar) can greatly affect your perceived stiffness. I highly doubt that the flex you're feeling is the top 30mm of the steerer bending while the rest stays entirely rigid; rather than the entire steerer is bending (whilst the positions supported by the headset stay still; eg if your stem is going to the right then inside the headtube the steerer is going to the left). As others have said, I think the only way you'll improve your stiffness is either to 1) change the fork; 2) get Mattias or someone to reinforce the entire length of the steerer of your existing fork (probably not cost, or weight effective); or 3) reduce your leverage by lowering the bars relative to the upper headset race (by removing the spacer and/or getting a shorter headset top cover).

sungod
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by sungod

what fork is it?

mises
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by mises

Get rid of all spacers. Other than that you'll have to get a different fork.

Your test jig is also seriously flawed so the "flex" you're seeing could be almost anything, from tires to perceptual distortions from much force you feel you're applying.

mattr
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Location: The Grim North.

by mattr

TBH, comparing a cross bike fork (designed for 1 hour race pace blasts at speed over varying surfaces, using Canti brakes) to a road bike (designed for several hours use at varying pace on moderately smooth tarmac with a crown mounted caliper) is a bit odd. I'd expect the cross fork to be significantly stiffer in most directions, especially on a bike as focused and "race ready" as Stevens Team Carbon.

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bikerjulio
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by bikerjulio

I can see it when I hold the front wheel and twist the bars.


Like another here, I believe you are seeing fork blade flex rather than steerer tube. Some forks are flexier than others. Tell us what you have.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

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