Stability lost

[growingvegetables]

Struggling up York Road towards the Shaftesbury, in the bus/cycle lane, and quite suddenly the bike starts to sort of weave. Just not going in a nice steady straight line. NONE of my doing.

D*** - frame fracture at the rear lug, derailer side. Complete fracture.

Hmm - still feeling quite euphoric about it. A couple of minutes later, I'd have been doing 25-30, mixed in with the craziness that passes for 40mph on the main carriageway.

 

[fullcycle]

I had a similar experience last year, id just come through a busy roundabout at peak hour after finishing work,as i went up a dropped curn to a cycle path on the pavement my frame gave way where the derailer was attached to the frame - only just managed to stay on the bike, makes you think some ones looking down on you really

 

[Biker Joe]

Oh dear. Very nasty. As you say, good job it happened there and you stayed safe.
What is the frame material? I'm guessing it's aluminium and a case of metal fatigue.

 

[S1mon]

when i read your location wondered if some one was trying to bike jack you!!!

 

[growingvegetables]

What is the frame material? I'm guessing it's aluminium and a case of metal fatigue.

Aye - aluminium and metal fatigue!

 

[Andrew_Culture]

Gah!

 

[matthat]

Aye - aluminium and metal fatigue!

Glad you were ok @growing vegetables!! That's a bit worrying as i'm about to receive my ally bike this week that i'm eagerly waiting for. Is this a common problem on ally frame bikes or is it just with hard/heavy use??

 

[Accy cyclist]

I have a tiny crack on my aluminium road bike as a result of having my saddle too high. I'm keeping an eye on it and it hasn't grown in the 6 months since i noticed it. If it spreads to the crossbar will i have to bin the bike?

 

[growingvegetables]

Glad you were ok @growing vegetables!! That's a bit worrying as i'm about to receive my ally bike this week that i'm eagerly waiting for. Is this a common problem on ally frame bikes or is it just with hard/heavy use??

We've had several aluminium frames, and never had a problem. My Dawes Discovery is 10 years old and just runs and runs and runs.

This one was a second hand bike though, and I knew it had been in a big fall as there was a big dent in the top tube. I'd looked over the rest of the frame damned carefully for cracks, paint wrinkles, or signs of other damage --- but didn't spot this crack happening as it was more or less hidden by the derailler hanger. Maybe the accident had also pretty seriously banged that bit of the triangle, and the previous owner had replaced the hanger? Just guesswork on my part.

 

[snailracer]

I have a tiny crack on my aluminium road bike as a result of having my saddle too high. I'm keeping an eye on it and it hasn't grown in the 6 months since i noticed it. If it spreads to the crossbar will i have to bin the bike?

The standard fix for this problem is to drill a small hole (3mm) at the end of the crack to "arrest" it. Smooth the edges (inside and outside the tube) with a tiny round file or emery cloth.

It sounds a bit strange, but the crack grows at the end because all the stress is concentrated at that tiny point - adding a round hole there spreads the stress all over the edge of the hole, so no single, small point is overstressed. This is why the clamping slot in the seat tube has a big hole drilled at the bottom of it.