While repainting an aluminum frame, my dad used a Dremel to remove some hard-to-reach bits of paint. This resulted in a couple gouges in the aluminum along the bottom of the seat tube, near where it connects with the bottom bracket shell.

I'm planning on taking this bike on a 1200 mile tour of the Midwestern/eastern US in a couple of weeks. Is this something to worry about? For reference, it's a 1980s Cannondale that was never ridden much. Not a "super-light" frame and seems generally pretty robust (except for this, maybe).

ride it.

if it were the chain stays that got nicked, or the down tube near the head tube, i'd be worried... seat tubes are a compressed member of the frame.

Good to know, thanks.

Normally I wouldn't agonize so much, but I really want to avoid getting stranded in rural Michigan with a broken frame and 40 pounds of gear...

I think it'll probably be OK for the length of that trip, but it's a bad place for a stress riser.

The seat tube near the BB is one of the most highly stressed area on a bicycle, being pushed down and rocked with every pedal stroke. Seat tube failures near the BB are among the most common non-crash breaks of older frames. see below



On the bright side, this kind of failure is among the least likely to cause a crash or injury. Speaking from first hand experience, it can be field repaired (won't be pretty) with readily available stuff and a bit of creativity.

So, as I said, enjoy the tour, and after that ride it as long as it lasts, but if/when you start to hear creaks or clicks as you pedal, you know where to check first.

Oh wow. That's somewhat more alarming.

I didn't mean to alarm you. I just wanted you to understand the realities.

Fatigue failures take time, so while the gouge may have a significant effect on the LONG TERM life of the frame, the odds still favor you completing your trip and riding for a long while afterward.

A factor to consider is the terrain, since standing (or even not standing) with high pedal pressure to climb is the kind of thing that would be hardest on the area. Another is your weight and strength. Lastly there's your riding style, with spinning lower gears being easier on the joint than mashing big gears.

I have a Cannondale T700 with worse damage than that and so far, so good. Keep an eye out for paint wrinkles and cracking in the area. I would smooth the edges of the gouge(s) to prevent a possible stress riser.

Brad

I wouldnt worry.

Thanks, I'll try to avoid mashing. I weigh 165, plus 40lbs or so of panniers. I'm guessing the panniers won't add much stress to the area, though.

No sweat related to panniers.

The major local stresses on the bottom bracket area are due to pedaling. Nothing you do or don't do now will make much difference. The tube will last until it cracks, which will happen sooner than it originally would have,

In the meantime, focus on enjoying the bike as if I had never given you a reason to be worried about it.