# Steerer wall thickness?



## calstar (Mar 26, 2013)

As frames/head tubes go toward the far end of the bell curve(very tall/large)does the steerer need to have a progressively heavier(wall thickness) steerer?I don't know what the stresses are between the hs bearings on the steerer itself, is this a critical factor? 4130 straight gauge wall thickness, 1.125", go from .058 to.065 to .095, application is an unsuspended "all rounder" that will see some use on fire roads, no single track. Steerer will be approx 15".

thanks, Brian


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## mattty (Feb 26, 2009)

This does depend on the application, but for a mountain/bumpy terrain bike I would suggest .065" or .095" for a big person (200 lbs plus). A large factor to consider is the axle to crown length. The longer the fork, the more stress is placed on the steer tube. 

You could make an aluminum insert that would allow a thinner .058" steerer. An insert would have to be hammered in very snug and be long enough that the steerer doesn't bend past it.

I have made forks with .095 steerers and they're not ridiculously heavy


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## calstar (Mar 26, 2013)

mattty said:


> A large factor to consider is the axle to crown length. The *longer the fork, the more stress is placed on the steer tube*.....I have made forks with .095 steerers and they're not ridiculously heavy


Could you elaborate on the "longer lever" principle placing more stress on the steerer? It seems as though the stress would be focused right at the crown/steerer junction, not over the full length of the steerer. Weight difference: .065 is .736 lb per ft, .095 is 1.045 lb.

thanks, Brian


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## Walt (Jan 23, 2004)

You will not break commonly available 2.1/1.6 butted steerers, or for your application, 1.6/1.2mm butted ones (True Temper makes a nice one). Why are you using straight gauge for a gravel bike?

-Walt


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## TrailMaker (Sep 16, 2007)

Stop and think for a moment;

Take a 4' horizontal bar. Two blocks underneath it (representing the HS bearings); one at the center of the tube and one at the left end, clamped at the blocks to a table. Put a load on the right end. Where will it bend? It will bend along its length to some extent, but the force will be focused at the lower block, which is acting as a fulcrum. It will bend between the blocks. The length of that span will govern how much load can be withstood. The longer the steerer, the more force it will stand - and absorb - without transferring it into other items such as the bearings or HT. Put a bearing inside the HT in the center of that span, and you will decrease the bending there, but increase the force that is then transmitted elsewhere. Better to let it bend in there as it will than transfer force into things that are already highly stressed. 

The distance between the horizontal centerline of the crown arms and the crown race is critical, shorter being better. It is a point of high stress. Thick crown race ends on steerers is requisite!


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## calstar (Mar 26, 2013)

_Walt:Why are you using straight gauge for a gravel bike?_

Uh.....no reason other than only build for myself, thats what I've used before, might as well save a little weight and go contemporary.

_TrailMaker: The length of that span will govern how much load can be withstood. *The longer the steerer, the more force it will stand* - and absorb - without transferring it into other items such as the bearings or HT_

Thanks for the explanation, makes more sense to me now. Does this mean that a longer steerer doesn't necessarily need to have beefier walls?

Brian


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## shiggy (Dec 19, 1998)

calstar said:


> _Walt:Why are you using straight gauge for a gravel bike?_
> 
> Uh.....no reason other than only build for myself, thats what I've used before, might as well save a little weight and go contemporary.
> 
> ...


You are better off using a butted steer tube. Been there... You need the extra thickness at the bottom (fulcrum) and it is less critical at the top.

The quote function works well, too.


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## Walt (Jan 23, 2004)

Straight gauge will be much, much heavier than a butted steerer. 

Maybe I am not understanding something here.

-Walt


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## TrailMaker (Sep 16, 2007)

Or...

Another way of looking at it is the penchant for frames to crack at the DT/HT junction, which illustrates the forces involved. The fact that you don't see steerers fail very often, especially given the existence of bikes with really short HTs, tells you that steerer sizing must be fairly well worked out, and that the commercially available steerers are up to the task. If an aluminum steerer in a super short 29r HT will last, you'll likely have no problem with a proper steel one.


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## Eric Malcolm (Dec 18, 2011)

Brian

To add to what has been said, you are looking at a very tall bike if you are using a 15" stem. A fork is the sum of all its parts just like any other bike part. Make sure that the blades you use are not so strong that if the fork is tested, the stem will collapse at the crown end. Hence the wisdom of using the butted end stem.

Putting that aside, there were many town bikes that used a 20" front wheel using very long steerer tubes in the 1960-70's on 25.4mm dia. When these came in for repairs, it was usually the blades that had bent, indicating a lower grade of steel (they were cheap bikes anyway). Compared to what we would expect of a bike today, they would not make the grade at all. I have yet to use my Humber Duplex fork, on this I used 28.6 x 1.65mm for my stem, but is deliberately used to match the springiness of the blades, and is not intended for challenging use, it is also is sleeved so it is bulked up in the critical area of the crown.

I guess what I saying is match up all the components, blades, crown, stem. Also, a game changer is what brake type are you using, disc's will require heavy duty...

Eric


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## calstar (Mar 26, 2013)

Eric Malcolm said:


> Brian
> 
> .....on this I used 28.6 x 1.65mm for my stem, but is deliberately used to match the springiness of the blades, and is not intended for challenging use, it* is also is sleeved so it is bulked up in the critical area of the crown.
> *
> ...


How far up the steerer did the sleeve go? I'll be using cantis initially but am going to build "disc ready" so yes it will be heavy duty(and I'm 245lbs).

I'm planning on using this crown NOVA CYCLO-X FORK CROWN FULL SLOPE 28.6 7° OFFSET :: FORK CROWNS :: Nova Cycles Supply Inc. and these blades NOVA ROAD OVAL Disk Brake fork blade 1.1 x 24 Oval :: TUBES STEEL :: Nova Cycles Supply Inc. and a Willits mount.

thanks to all for input so far, Brian


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## unterhausen (Sep 28, 2008)

I wonder if the OXPLAT lightweight steerer has ever been used full length, it's so long you could use it as a top tube on a kid's bike. Get a commercial steerer that's long enough for the application and use that, I can't imagine you will have a problem


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## Eric Malcolm (Dec 18, 2011)

Brian

My sleeve went in 50mm.

Looking at your selection, you have chosen well with future proofing the disc option, and I see that Nova have no steerers in at the moment, so, is this where the problem begins?
So it would be easier to try 28.6mm tube and sleeve? In your situation, I would sleeve up 65mm, matching the specifications of the butted version, and if possible, machine the taper that butted ones come with. A 1mm wall would be plenty, as when you silver it in, thicker steerer will carry the heat for you when you draw the silver up the tube. Keep the clearance tight, say .25mm. Also, try to keep the whole tube hot with a larger tip. Unable to advise on tip size as I use a MAPP for my work. When you come to do the crown, you will not disturb the previous brazing.

The better way would be to simply source elsewhere if possible or maybe a follower here could help out with a spare stem?

Eric


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