Singlespeed & Fixed Gear - what am i missing? ebay question

ok, whenever i'm browsing ebay, ppl list bikes or frames with lines like "some scratches, but the bike has never been crashed."

i don't know bout y'all, but i tank on my bike fairly frequently, and it never results in any serious damage to the frame, although my bars are a bit bent now on the one side. things get scratched, but not dented.

is a crashed bike really a problem, assuming there's no big dents in the tube? i'm not thinking of buying any such frames, i'm merely curious.

-rob

a crash can cause really nasty stresses on the tubes...but usually, if there's no huge dents, or the downtube hasn't collapsed in on itself, it's reasonably safe...there might be some minor allignment problems with it...but that's nothing the old F.A.G. and D.A.G. tools can't fix.

it can be a problem because the crash might exceed the material's fatigue limit type thing [i'm a mechanical engineer i should probably know the correct term but can't thinkof it right now]

basically if the stresses in a material stay below a certain level, it will never fatigue. but if the stress rise above that level, any stresses after that will contribute to weakening it.

you can try this at home with a paperclip. keep bending it in the same place and it will eventually snap.

aluminium has a really low fatigue level [which is exceeded in ordinary use half the time]
steel has a quite high limit, but stresses could rise above it if it's crashed
i'm not sure if titanium has a limit.

fssb
sparky

yeah,yeah, i hear ya. but we're talking about a mildly fat guy in some relatively low-speed crashes on a steel rig. there's no visible damage, no dents, no obvious problems where things are misaligned, etc. i could clearly sell the thing as having 'never been crashed', and no buyer would know. further, if i was looking to buy the frame, and the seller told me it had been crashed, it wouldnt even worry me at all.

really, now, how long can one ride a bike daily (thru icy conditions, drunken conditions, with a hub failing/locking up, etc) without crashing his rig? it's just bound to happen eventually, and i cant imagine anything but a minority of crashes cause serious damage to the ol' frame.

at least, that's my experience. heck, i've seen more damage done thru shipping a bike then thru crashing it. =P

fs- vintage track frame, never been shipped... =P

-rob

I thnk the term "never Crashed" really refers to
Race type crashes, not the usual stuff that joe average
cyclists would do.
just my .02 worth

Marty

I thnk the term "never Crashed" really refers to
Race type crashes, not the usual stuff that joe average
cyclists would do.
just my .20 worth

Marty

Marty-

Why is your advice ten times more valuable than the rest of ours?

Marty-

Why is your advice ten times more valuable than the rest of ours?
He is Moderator GOD (so he thinks) :)

I always took "crashed" to mean "hit by car." IMHO if you're not crashing, you're not riding hard enough anyway. Of course I am biased.

If you fall over the frame usually really doesn't even touch anything. (Bars, pedals, and rear axle absorb most of the fall.) I think you would have to really hit something solid to cause the frame to be damaged. A friend of mine ran straight into a lightpole with my steel Miyata track bike and I am pretty sure it is still good, haven't actually ridden it since though. The "never been crashed" is probably something that people just include to make you more inclined to bid and less worried about the condition of the bike..

-Jason

When I was a kid, I had a bad habit of crashing into cars. You can always bend the steel forks back.

to quote my buddy homer

DOH

When I was a kid, I had a bad habit of crashing into cars. You can always bend the steel forks back.
if you crash hard enough all you need to do is turn the stem 180

and the brake block carriers... don't forget them.

fssb
sparky