24 replies to this topic

[Juju]

Herro.

Please may I pick your brains about my bike? I've just been cleaning it after a ride & noticed some mini-style bubbling. I didn't think aluminium frames rotted?

It's a Cannondale, 7 years old, it's covered about 30,000 miles & been well looked after, but it looks like it's oxidising beneath the paint:

Rear of the frame, chainstay near the drainage hole:



and the rear forky-bit, just above the wheel (or below in this pic because the bike's upside down...)



It's not brilliantly clear, but it is bubbling....



I've seen alu frames shear under the forces of a 15 stone gear grinder, but it is normally near the welds, but I've never seen this happen before.

Will my frame fail me? Is it time to get a new one? Whasshappenin' to my lovey-lovely bikie?

Please help?!

Ta.

[Purple Tom]

I saw this a few times when I worked in t'trade. It was particularly bad on a Jekyll I worked on, the guy had owned it for about 5 years, ridden it to work every day and never really did any maintenance at all, other than the usual misguided half a tin of 3-in-1 oil on the chain in the winter...

Anyway, that oxidisation is caused by water/salt/mud etc getting onto the bare aluminium through damage to the paint. It is usually more prevalent on the back end, because it gets the most abuse - the chain slapping on the chainstays, stones, grit etc being flung up by the back wheel.

Depending on how bad it is you may get away with rubbing it down to good metal, then repainting and relacquering it. However, you say the frame is 7 years old and its covered a decent mileage - it might be time to consider looking at building your components onto a new frame. They're not designed to last forever, and the forces at work during normal riding (even with someone as petite as you Juju!) are pretty considerable, so the inevitable fatigue takes place over time. That is why most manufacturers only guarantee Alu frames for 5 years or less.

Thats my opinion though, other people may say differently Hope that helps a bit.

Tom

[RobJaxon]

It looks like a 7 year old bike should do. My old Orange had some 'bubbling' on it after 2 years of intense riding. I got out the orbital sander and got all the paint off, took the rusty bits out, (luckily it hadn't gone all the way through) but just incase i got out the rotary tool bit cut around the rust and welded a new aluminium plate to it, then i sanded that off, then painted it over. Looks as good as new!

[mighty mini jack]

Yep think you've covered that in a nut shell Tom, although the first pic of the cahinstay does look abit severe!


Think it would be good to sand the frame back to metal then build the layers up as Tom said.

[panelbeaterpeter]

I was speaking to a friend of mine who studied aluminum corrosion as part of a uni course, said if you rub away all the corrosion and repaint it, it'll come back worse than if you rub it down leaving a little of the corrosion, then paint over it again. Makes no sense to me, but hey!

[paulrockliffe]

It's certainly not a reason to go buying a new frame, I wouldn't even worry about that on my frame.

[Juju]

Thankings, Dudes.

Tom - your answer wasn't really what I wanted to hear (I love my "Eve" ), but nehmind, if I needs a new frame, then I needs a new frame. Thanks.

I wouldn't want to sand my own frame back myself & patch it up, and the money spent on that (with no guarantee that it won't come back) I might as well spend on a new frame.

EDIT - sorry Mister Rockliffe, you were too fast for me! Have you had this happen to any bikes of yours, then?

Edited by Juju, 05 May 2008 - 07:33 PM.

[Purple Tom]

Juju - My opinion isn't by any means fact, in all likelihood the frame will go on for years to come, and I'm not saying that you must go out and buy a new frame - more that it might be something to consider, and look at what options are available. I myself ride a 1999 FSR Comp with god-knows how many miles under its wheels, but I like it and I'll only get a new frame when it breaks - but its always at the back of my mind that the next drop off or technical section could be its last!

It may be worth taking it to a local specialist bike shop and seeing what their advice is, or contacting a frame specialist (I use Mercian Cycles - they're local to me) such as Argos Racing Cycles.

[Mayfair85]

I was speaking to a friend of mine who studied aluminum corrosion as part of a uni course, said if you rub away all the corrosion and repaint it, it'll come back worse than if you rub it down leaving a little of the corrosion, then paint over it again. Makes no sense to me, but hey!

This could be something to do with the fact that bare aluminium protects itself from corrosion by forming a thin layer of oxide over itself.

[paulrockliffe]

Sorry, no I haven't had it happen to me, but I do know that the tubes are pretty thick, so that sort of corrosion isn't wortth worrying about in terms of your bike snapping.

I do ahve an aluminium road frame that was clued together, one of the chainstay bonds failed and the bike was ok to ride home without a catastrophic failure. Took 6 months to find someone that could weld that back together!!

[RobJaxon]

Sorry, no I haven't had it happen to me, but I do know that the tubes are pretty thick, so that sort of corrosion isn't wortth worrying about in terms of your bike snapping.

I do ahve an aluminium road frame that was clued together, one of the chainstay bonds failed and the bike was ok to ride home without a catastrophic failure. Took 6 months to find someone that could weld that back together!!

Very true. When I cut into the piping it was atleast 3cm thick.

[The Matt]

Sorry, no I haven't had it happen to me, but I do know that the tubes are pretty thick, so that sort of corrosion isn't wortth worrying about in terms of your bike snapping.

I do ahve an aluminium road frame that was clued together, one of the chainstay bonds failed and the bike was ok to ride home without a catastrophic failure. Took 6 months to find someone that could weld that back together!!

Very true. When I cut into the piping it was atleast 3cm thick.

Huh? Must've weighed a lot!

[Juju]

Juju - My opinion isn't by any means fact, in all likelihood the frame will go on for years to come, and I'm not saying that you must go out and buy a new frame - more that it might be something to consider, and look at what options are available. I myself ride a 1999 FSR Comp with god-knows how many miles under its wheels, but I like it and I'll only get a new frame when it breaks - but its always at the back of my mind that the next drop off or technical section could be its last!

It may be worth taking it to a local specialist bike shop and seeing what their advice is, or contacting a frame specialist (I use Mercian Cycles - they're local to me) such as Argos Racing Cycles.

Cheers Tom. I have a couple of mates in the business so I will get a 'second opinion' before we pronounce her dead. I might we worrying aboot nowt. She may well go on for another 30,000.......it might just be down to the niggling at the back of my mind that the next ride could lead to a stint in hospital & a new bike.


And no, the alu tubing is no way near 3cm thick, 3mm mebbe.......

[Juju]

I took my bike to see Uncle-Dan-the-Bicycle-Repair-Man in Dorking, and he said "Oooh, Dear. Best contact Cannondale."

I've emailed them the piccies & described what has happened.

Now I'm hoping Cannondale will honour their lifetime guarantee policy. One can but try.....



PS - I still went out for a ride afterwards, anyhoo.

[RobJaxon]

I took my bike to see Uncle-Dan-the-Bicycle-Repair-Man in Dorking, and he said "Oooh, Dear. Best contact Cannondale."

I've emailed them the piccies & described what has happened.

Now I'm hoping Cannondale will honour their lifetime guarantee policy. One can but try.....



PS - I still went out for a ride afterwards, anyhoo.

It's nothing structural.