Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Max spacing on alloy steerer tube

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

Max spacing on alloy steerer tube

Reply

Old 07-12-18, 04:42 PM
  #1  
MyTi
6-4 Titanium
Thread Starter
 
Join Date: Jul 2018
Posts: 139
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 92 Post(s)
Max spacing on alloy steerer tube

Is there any guidelines for the maximum length of a alloy steerer tube. I posted a pic of my bike recently and a post commented on the safety of the steerer tube length:


This is a origin8 1 1/8 carbon fork with alloy steerer, set up with a total of 85mm of spacers. A 60mm spacer between headset and stem, and 25mm of spacing between stem and top cap. I've googled this and it seems to be accepted that carbon steerers can have a max of 60mm of spacing. As for alloy, I wonder ifthe additional 25mm of spacing would be an issue. Should I be concerned or leave it be.
MyTi is offline  
Reply With Quote
Old 07-12-18, 04:51 PM
  #2  
Kontact
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 3,628
Mentioned: 32 Post(s)
Tagged: 0 Thread(s)
Quoted: 2141 Post(s)
Anything above the stem doesn't really matter. But I wouldn't go above 40mm between the headset and stem.

Aluminum is not known for making steerers extra tough. Lot of broken Madone aluminum steerers at one time. You can push things with steel, not aluminum.

If you need your bars that high, use a sloping stem.
Kontact is offline  
Reply With Quote
Old 07-12-18, 05:05 PM
  #3  
MyTi
6-4 Titanium
Thread Starter
 
Join Date: Jul 2018
Posts: 139
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 92 Post(s)
Originally Posted by Kontact View Post
Anything above the stem doesn't really matter. But I wouldn't go above 40mm between the headset and stem.

Aluminum is not known for making steerers extra tough. Lot of broken Madone aluminum steerers at one time. You can push things with steel, not aluminum.

If you need your bars that high, use a sloping stem.
I see. I don't feel I need the bars that high and was thinking about lowering it actually. I think I will reduce the spacing between headset and stem to 40mm as advised.
MyTi is offline  
Reply With Quote
Old 07-12-18, 06:50 PM
  #4  
dsbrantjr
Senior Member
 
dsbrantjr's Avatar
 
Join Date: Sep 2010
Location: Roswell, GA
Posts: 5,971

Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta

Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 569 Post(s)
Isn't the lever arm from the bars to the headset? Any way you increase that distance, spacers or riser stem, should produce an equivalent (roughly) level of force on the steerer. I think.
dsbrantjr is offline  
Reply With Quote
Old 07-12-18, 07:00 PM
  #5  
Kontact
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 3,628
Mentioned: 32 Post(s)
Tagged: 0 Thread(s)
Quoted: 2141 Post(s)
Originally Posted by dsbrantjr View Post
Isn't the lever arm from the bars to the headset? Any way you increase that distance, spacers or riser stem, should produce an equivalent (roughly) level of force on the steerer. I think.
That is the lever arm, but the failure point has to do with where the steerer is clamped and how much that lever arm can withstand. Spacers are not rigid and don't give any strength back so more of them aren't helping anything. A 46cm bar is designed to be that long a lever. A steerer tube is only designed to be a 40+stem lever.

I'm sure an argument could be made for anything, but 40mm is the industry standard, so whatever failure testing is done assumes that it isn't much greater than 40. I would be happy with longer than 40mm if the steerer was steel or a thicker than standard aluminum, but not otherwise.
Kontact is offline  
Reply With Quote
Old 07-12-18, 07:29 PM
  #6  
MyTi
6-4 Titanium
Thread Starter
 
Join Date: Jul 2018
Posts: 139
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 92 Post(s)
Originally Posted by Kontact View Post
That is the lever arm, but the failure point has to do with where the steerer is clamped and how much that lever arm can withstand. Spacers are not rigid and don't give any strength back so more of them aren't helping anything. A 46cm bar is designed to be that long a lever. A steerer tube is only designed to be a 40+stem lever.

I'm sure an argument could be made for anything, but 40mm is the industry standard, so whatever failure testing is done assumes that it isn't much greater than 40. I would be happy with longer than 40mm if the steerer was steel or a thicker than standard aluminum, but not otherwise.
I was reducing the spacer length and just with all the spacers off and trying to flex the tube by hand...I know it's aluminum but that is one thick walled tube. I can't imagine ever having the force to snap that unless in some kind of accident. I wonder if it helps that the 60mm spacer is one spacer between the headset and stem, rather than a bunch of small spacers. Does that factor in at all?
MyTi is offline  
Reply With Quote
Old 07-12-18, 07:35 PM
  #7  
Kontact
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 3,628
Mentioned: 32 Post(s)
Tagged: 0 Thread(s)
Quoted: 2141 Post(s)
Originally Posted by MyTi View Post
I was reducing the spacer length and just with all the spacers off and trying to flex the tube by hand...I know it's aluminum but that is one thick walled tube. I can't imagine ever having the force to snap that unless in some kind of accident. I wonder if it helps that the 60mm spacer is one spacer between the headset and stem, rather than a bunch of small spacers. Does that factor in at all?
Well,
Originally Posted by Kontact View Post
I'm sure an argument could be made for anything, but 40mm is the industry standard, so whatever failure testing is done assumes that it isn't much greater than 40. I would be happy with longer than 40mm if the steerer was steel or a thicker than standard aluminum, but not otherwise.
It's your call.
Kontact is offline  
Reply With Quote
Old 07-13-18, 08:41 AM
  #8  
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 37,463

Bikes: 8

Mentioned: 143 Post(s)
Tagged: 0 Thread(s)
Quoted: 5606 Post(s)
Consider changing to an up angled stem to reach the same bar height?

An alternate would be the BBB BHP 21 internal-quill stem raiser (Euro Import)
as a reinforcing liner *..
or perhaps lining the existing steerer with additional aluminum ,
doubling the wall thickness..

*I have used one as a fix for a too short a fork, it replaces the star nut,
and can go entirely in a fork steerer with a 1 " inside diameter.
top cap headset pre load is retained..





...
fietsbob is offline  
Reply With Quote
Old 07-13-18, 11:41 AM
  #9  
Litespud
Senior Member
 
Join Date: Oct 2017
Location: Chapel Hill NC
Posts: 205

Bikes: 2000 Litespeed Vortex Chorus 10, 1995 DeBernardi Cromor fixie

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 81 Post(s)
Originally Posted by MyTi View Post
I was reducing the spacer length and just with all the spacers off and trying to flex the tube by hand...I know it's aluminum but that is one thick walled tube. I can't imagine ever having the force to snap that unless in some kind of accident. I wonder if it helps that the 60mm spacer is one spacer between the headset and stem, rather than a bunch of small spacers. Does that factor in at all?
The issue isn't whether you can visibly flex the steerer - likely you can't. The issue is thousands of sub-visible torques on the long steerer, leading to fatigue and eventual failure. That being said, unless you're a hammerhead who's constantly torquing on the bars, I wouldn't be too concerned with 60mm on an Al steerer, but it does look a little goofy - makes me wonder if your frame's not a little small.
Litespud is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service