Steerer tube spacers

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neilob
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Steerer tube spacers

Postby neilob » 27 Jul 2020, 1:03pm

I have just bought a new pair of forks with longer steerer tube to lift the cockpit of my road bike. Forks are carbon and steerer is alloy. What is the conventional wisdom regarding how high above the top of the head tube you can have the stem? I seem to remember reading that it isn’t a massive height to protect the fork from failure.
Using a car to take an adult on a three mile journey is the same as using an atomic bomb to kill a canary.

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CJ
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Re: Steerer tube spacers

Postby CJ » 27 Jul 2020, 3:43pm

Depends on the fork - the manufacturer will have some guidance on that, because the higher the handlebars stand above the top head bearing, the greater the bending stress exerted by your upper body upon the steerer tube at that point, in one direction with every bump in the road and other directions when you heave your way up a hill. Steel fork steerers are generally tough enough to stand a lot of that and some steel touring frame specialists, such as Surly, even go so far as to set no limit on the spacer stack under your stem! Carbon and especially aluminium though, you'd better be careful with, especially if you're a biggish bloke with wide shoulders. If in doubt, stick at 5cm.
Chris Juden
One lady owner, never raced or jumped.

neilob
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Joined: 31 Jan 2008, 3:58pm
Location: Notts/Lincs borders

Re: Steerer tube spacers

Postby neilob » 27 Jul 2020, 5:45pm

Thanks Chris but just to be clear the original forks were 225mm steerer while new ones are 300mm but I am cutting them down to 275mm. This will require around 75mm of spacers under the stem but obviously not including the stem itself. I assume your 5cm/50mm also excludes the stem? So my plan exceeds your limit by 25mm. The replacement fork is brand new and is Tifosi branded but goodness knows who makes it! I don’t want anyone to recommend whether this is ok or not because it is unfair but it doesn’t seem a massive risk or does it?
Using a car to take an adult on a three mile journey is the same as using an atomic bomb to kill a canary.

cyclop
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Re: Steerer tube spacers

Postby cyclop » 27 Jul 2020, 6:22pm

Think about alloy quill stems,1inch diam,4 inches sticking up,2or 3 inches in the head tube-----i.e.I wouldn,t worry about your 3" of steerer,1.25in diam,firmly anchored to the forks,enormous strength.

fastpedaller
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Re: Steerer tube spacers

Postby fastpedaller » 27 Jul 2020, 6:38pm

cyclop wrote:Think about alloy quill stems,1inch diam,4 inches sticking up,2or 3 inches in the head tube-----i.e.I wouldn,t worry about your 3" of steerer,1.25in diam,firmly anchored to the forks,enormous strength.

And only 3mm wall thickness? (my guess)

Jamesh
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Re: Steerer tube spacers

Postby Jamesh » 27 Jul 2020, 7:33pm

Your fork steerer is mainly in compression at front and tension at rear the spacers take the compression and the tension at the rear is nowhere at capacity with a small amount of torsion for steering, nothing imho to worry about.

Btw where they tapered forks?

If so I'd happily take them for my silly mate who cut his Boardman steerer too short!!

Cheers James

mattsccm
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Re: Steerer tube spacers

Postby mattsccm » 27 Jul 2020, 8:04pm

I'll bet you find no manufacturer happy with that sort of extension. If it worries you enough to as us then ask them and either be reassured :D or unhappy.
I wouldn't. The damn things will flex and annoy me.

neilob
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Joined: 31 Jan 2008, 3:58pm
Location: Notts/Lincs borders

Re: Steerer tube spacers

Postby neilob » 28 Jul 2020, 7:15pm

Jamesh wrote:Your fork steerer is mainly in compression at front and tension at rear the spacers take the compression and the tension at the rear is nowhere at capacity with a small amount of torsion for steering, nothing imho to worry about.

Btw where they tapered forks?

If so I'd happily take them for my silly mate who cut his Boardman steerer too short!!

Cheers James

The forks are 1” steerer so probably no good for a Boardman?
Using a car to take an adult on a three mile journey is the same as using an atomic bomb to kill a canary.