7005 Head Tubes Cracking

[JonSus]

Has anyone noticed old 7005 Aluminum frames developing cracks on the head tubes? I pressed some Chris King cups into a high quality vintage frame from 1993 a few years ago and just noticed the head tube now has a crack down the side. The frame has just been hanging on the wall since and the crack is pretty obvious. I think I would have noticed it at the time so I'm pretty sure it happened while hanging on the wall. The fame was originally reamed and faced back in 93. The temperature where it is stored probably varies from 10-37 deg celsius throughout the year. Could the 7000 series aluminum harden from age enough that it becomes brittle and cracks from the pressure of installed parts? I'm worried about pressing headsets into my old frames now.

 

[kingoffootball]

I think the Chris King headset is a significant factor. I seem to remember reading on here that they tend to stress the headtubes a little more:

Post in thread 'To repair or not repair cracked head tube'

Jan 18, 2018

That Manitou one was front bottom side so more stressed at the front edge in normal use.
Very weird/rare to get just a top side crack...probably a badly fitted or over-tolerance headset cup.

I see quite a few shiny NOS frames with fancy Chris King cups to go with their cracks...

Is it viable replacing a top tube? Is it even possible to re-weld one in?

Yes, fairly easy with a top tube, since there's no specific requirement on wall thickness, butts etc, unlike head-tubes and seat-tubes, so easier to source suitable tubes.
I have a PACE RC200 in at the moment for a head tube and...

• danson67

 

[bikeworkshop]

Cracked head tube is a common failure style of aluminium frames - even when they were new-ish.
The interference fit must apply stress to the tube - and a difference of a few microns in the inner diameter, or the headset sleeve will make a significant difference.

You would think a quality frame and quake headset would have superior tolerance to cheap items though.

Commonly these vertical cracks appear (most commonly at the bottom) after riding a certain amount, but even hung on the wall, the stress is still there - albeit less than a bad landing after getting big air with some MonsterTs up front - a common failure scenario in the late 90s!

 

[d8mok]

What frame?

CK is well known to be such a precise fit they can cause issues

 

[JonSus]

Hmm. I might have to start sanding down the headset cups to feel at ease. I remember installing a 1 inch King in a carbon frame that felt very tight going in. This frame was an original Manitou hardtail built with Easton 7005 tubing. The one I'm in the air on in my avatar photo so it did have some pre-existing stress. It originally had a Dia Compe sealed bearing headset in it, not a King. Live and learn. Thanks for the replies.

 

[legrandefromage]

It's all in the extrusion process. The aluminium is forced through a die which should squeeze all the crystals out - if you look at cracks closely you will see the structure of the aluminium looking like quartz

Many of the cheaper frames were simply better quality as the process had been done properly which is why so many survived.

6061 has a different grain structure (I think that's the reason) so it's properties when bashing a boutique headset into it means it reacts and behaves different to 7000 series

Garage queens have been known to go ping whilst on display in warm sunshine, Manitou frames have been the worst.

Fisher and Nishiki along with Saracens' aluminium e-stay frames all seem to go pop at the drop of a ha..

'Pinnnngggg!'

Oops, there goes another one

@danson67 is your man for alumininiminiumim repairs and for a better explanation

 

[vtwinvince]

I have a RM Vertex TO with this problem.