Alu fatigue on old frames

[Isaac.owen]

Hi all,
Whats everyone's thoughts on aluminium fatigue on older bike frames, not just Cannondale in specific.
Obviously I'm more concerned at the welded areas, mostly the headset as that'll hurt the most.
have just been thinking about it as I ride around these beautiful,albeit cracked up new England roads!

Anyone with experience or knowledge here?
Thanks in advance

 

[petergt4]

Not with bicycle frames but have close to 20 years of aluminum tanker truck and trailer maintenance/welding experience. As with welding any material, proper fit-up is essential to welded joint longevity. If there is any measurable gap between the pieces, there will be flex and there will be cracks. Aluminum doesn't have the elasticity of metals like steel, or especially titanium, so it needs to be stout right from the get-go. Aluminum needs plenty of welding amperage as the material dissipates heat so easily.

Aluminum is funny though, because there are times I've seen items just stitch-welded along long lengths and it's fine for many years, and solidly-welded structures spider-cracked everywhere.

I'd expect headtubes to be lower down in the cracking susceptibility. In Cannondale's case with their enormous downtubes and generous tube overlap at the headtube junction, there's plenty of meat there. I'd pay more attention to the chainstay/BB junction and rear dropout junctions as there isn't much material there in the tubing and it is a high stress area.

Whereabouts in New England do you ride? I used to live in Eastern Canada and spent LOTS of time in New York, New Hampshire and Vermont, many years ago. It's one of the things I miss, living here in the Pacific NW...

 

[black lightning 1987]

I've actually seen more cracked steel and titanium frames than aluminum ones. My dealer told me that the 80s Crit Cannondales would crack in the seat tube near the front derailleur mount but I've put 8,000 miles on one I bought used and it's still free of cracks. The cantilever dropouts of the 2.8 frames were highly stressed. I have seen examples of them that have cracked.

 

[Isaac.owen]

thanks for the replies guys, put me at ease now!

I'm currently in Rhode Island, Jamestown and will be moving around New England a bit over the next couple months with work; Martha's vineyard, Nantucket, Boston, Long Island and hopefully some Maine!

 

[black lightning 1987]

Sounds like you have some great riding ahead.

Looks like you have a 3.0 road frame. Especially, keep an eye out for cracking near the FD mount and where the cantilevered dropouts meet the rear triangle. Most fatigue cracks start small and take quite a while to progress to the point of failure. Keep the frame clean and look closely at high stress areas often.

 

[petergt4]

thanks for the replies guys, put me at ease now!

I'm currently in Rhode Island, Jamestown and will be moving around New England a bit over the next couple months with work; Martha's vineyard, Nantucket, Boston, Long Island and hopefully some Maine!

Take a look at this thread of mine of a recently purchased '91 SE1000 with some cracks... I kind of shot down my own theory of the headtube being the most stout area of a frame Oh well.

Nothing that can't be fixed though.

http://community.vintagecannondale.com/threads/1991-se1000.118/#post-475