slightly damaged frame--ride it?

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I was given a good looking early mountain bike, built about 1990. I took it
to the yard to wash it and discovered slight bulges in the down tube and top
tube. The funny thing is, the undersides of both tubes have these slight
wrinkles, but the top side of the tubes do not look or feel in the least as
if they are bent.

So, I figure someone jumped off of a ledge just a bit too high, causing
these tubes to be compromised like that. Is it safe to just ride on
pavement, though? I can't see that the metal is broken because the paint is
only a bit flaked on the underside of the down tube where the wrinkle is.

I can understand that the head tube/fork angle to the frame may not be the
same as Trek intended in 1990, but what I don't know is: is this frame
dangerous to ride? Can somebody with experience give me some insight on
this?

thanks,

Pat

On Sat, 10 Apr 2004 19:58:47 -0500, Pat wrote:

> I was given a good looking early mountain bike, built about 1990. I took it
> to the yard to wash it and discovered slight bulges in the down tube and top
> tube. The funny thing is, the undersides of both tubes have these slight
> wrinkles, but the top side of the tubes do not look or feel in the least as
> if they are bent.

Sounds like he ran into something.

> I can understand that the head tube/fork angle to the frame may not be the
> same as Trek intended in 1990, but what I don't know is: is this frame
> dangerous to ride? Can somebody with experience give me some insight on
> this?

Eventually it will crack at those points. It is probably also out of
alignment and, as you said, has steeper angles than were intended. You
might be able to ride it for a long time with no problem, but you might
not. At least keep an eye on those areas for cracks. Better to not use
it, in my opinion.

--

David L. Johnson

__o | Accept risk. Accept responsibility. Put a lawyer out of
_`\(,_ | business.
(_)/ (_) |

On Sun, 11 Apr 2004 13:31:20 -0400, "David L. Johnson"
<david.johnson@lehigh.edu> may have said:

>On Sat, 10 Apr 2004 19:58:47 -0500, Pat wrote:
>
>> I was given a good looking early mountain bike, built about 1990. I took it
>> to the yard to wash it and discovered slight bulges in the down tube and top
>> tube. The funny thing is, the undersides of both tubes have these slight
>> wrinkles, but the top side of the tubes do not look or feel in the least as
>> if they are bent.
>
>Sounds like he ran into something.

I agree. The head tube angle is probably steeper now. If it still
has the orignal fork, I'd expect it to be bent as well.

>> I can understand that the head tube/fork angle to the frame may not be the
>> same as Trek intended in 1990, but what I don't know is: is this frame
>> dangerous to ride?

You will only find out if it fails.

>Can somebody with experience give me some insight on
>> this?
>
>Eventually it will crack at those points. It is probably also out of
>alignment and, as you said, has steeper angles than were intended. You
>might be able to ride it for a long time with no problem, but you might
>not. At least keep an eye on those areas for cracks. Better to not use
>it, in my opinion.

I'll second that. The frame might be safe to ride from a simple "will
it fail suddenly and soon?" standpoint, but given that it's already
likely to have toe-to-wheel clearance issues and squirrely handling
due to reduced trail, I can't see that it's worth messing with.
Personally, I'd part this one out and just keep the useful bits.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

Pat wrote:
> I was given a good looking early mountain bike, built about 1990. I took it
> to the yard to wash it and discovered slight bulges in the down tube and top
> tube. The funny thing is, the undersides of both tubes have these slight
> wrinkles, but the top side of the tubes do not look or feel in the least as
> if they are bent.
> So, I figure someone jumped off of a ledge just a bit too high, causing
> these tubes to be compromised like that. Is it safe to just ride on
> pavement, though? I can't see that the metal is broken because the paint is
> only a bit flaked on the underside of the down tube where the wrinkle is.
> I can understand that the head tube/fork angle to the frame may not be the
> same as Trek intended in 1990, but what I don't know is: is this frame
> dangerous to ride? Can somebody with experience give me some insight on
> this?

That is a front impact . Jumping dents the top of the tubes.

Your question is one of degree. Have an experienced frame
repair person look at it or send me photos.

You should turn the fork 90 degrees and sight it, from the
top of the stem straight down. And/or have its alignment
checked by someone with alignment gauges and experience.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

> On Sat, 10 Apr 2004 19:58:47 -0500, Pat wrote:
>>I was given a good looking early mountain bike, built about 1990. I took it
>>to the yard to wash it and discovered slight bulges in the down tube and top
>>tube. The funny thing is, the undersides of both tubes have these slight
>>wrinkles, but the top side of the tubes do not look or feel in the least as
>>if they are bent.

David L. Johnson wrote:
> Sounds like he ran into something.

(p)>>I can understand that the head tube/fork angle to the
frame may not be the
>>same as Trek intended in 1990, but what I don't know is: is this frame
>>dangerous to ride? Can somebody with experience give me some insight on
>>this?

(The cautious DLJ)> Eventually it will crack at those
points. It is probably also out of
> alignment and, as you said, has steeper angles than were intended. You
> might be able to ride it for a long time with no problem, but you might
> not. At least keep an eye on those areas for cracks. Better to not use
> it, in my opinion.

That's not clear to me. A mid price MTB with 1.2mm tube may
be readily straightened with no real risk if the damage is
slight to moderate. We have straightened literally over a
hundred front-impact frames over the years, the bulk of
which are still on the road. OTOH we would refuse the job
if there were cracks at those bulges, for example. The
problem is, we don't know how significant his damage is.
Better to get an experienced eye on that frame, I think.


--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971