Bent Down Tube = Scrap Metal?
04-13-10, 01:15 PM
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Bent Down Tube = Scrap Metal?
I picked up an early 90's Bianchi Mtb with hopes to turn into a beater/winter commuter, it does needs a few parts to actually be road ready. I was cleaning it up and I noticed the bottom of the down tube near where it meets the head tube is bent/buckled. Am I right in assuming it's trash?
(The bike is upside down)
(The bike is upside down)
04-13-10, 01:22 PM
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I had an early 90s Grizzly I did that same thing to (altho more severely), no question in my mind it was a garage wall decoration after that...
04-13-10, 02:14 PM
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I'd say it depends what you do with the bike. That looks like a steel frame, no good as a long distance road bike but probably fine to ride to the corner store with.
04-13-10, 02:37 PM
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Wall art. The good news is that you should be able to find a decent MTB frame to use those parts for very little $$. I find them around here a lot.
04-13-10, 07:00 PM
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Damage like that usually means there was a hard head-on crash at some point in that frame's life. Not only is the downtube buckled but the head tube may be ovalized so the headset will not fit right and the front end geometry was also changed. Wall art or donate it to the recycle bin.
04-13-10, 07:44 PM
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This is typical of a bike that's been in a front end collision. For a good bike it's trash, but it might be OK as a beater or commuter. Ton's of people are riding these special short wheelbase bikes, many not even knowing it. It will fail eventually, but eventually could be a long way off. Just inspect it for the beginning of a crack from time to time.
Ultimately the determining consideration will be how short the new wheel base is, and/or front wheel clearance to the downtube and pedals, so before you put any time into it, stick in a fork and wheel and check. If the clearance is OK it might be fine to build up with leftover stuff and might well last until something better comes along.
BTW - for future reference, the front bottom of the downtube is the first place to check when considering a used frame or bike.
Ultimately the determining consideration will be how short the new wheel base is, and/or front wheel clearance to the downtube and pedals, so before you put any time into it, stick in a fork and wheel and check. If the clearance is OK it might be fine to build up with leftover stuff and might well last until something better comes along.
BTW - for future reference, the front bottom of the downtube is the first place to check when considering a used frame or bike.
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04-14-10, 09:42 AM
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There is a tool used to push the head tube away from the bottom bracket to 'repair' exactly this type of damage, and I have seen frames that have been repaired multiple times and still work fine.
I agree you should not trust it 100%, but as an occaisional errand running machine it can be fine.
Call around and find a shop with the tool.
I agree you should not trust it 100%, but as an occaisional errand running machine it can be fine.
Call around and find a shop with the tool.
04-14-10, 09:52 AM
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Why is a questionable frame better suited to errand runs than say, 100 mile rides?
04-14-10, 09:57 AM
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I painted a frame at the wrinkle with nail polish. If there is any movement the nail lacquer will crack, letting you know well in advance that the frame is cracked. I rode the snot out of that bike for another 5 yrs.
04-14-10, 09:59 AM
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Could it be a bad weld?
04-14-10, 10:29 AM
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When you've seen nearly new aluminum frames break inexplicably and see other people riding their 'wall art' steel frames year after year as I have you get a feeling for what fatigue a frame can take first hand.
04-14-10, 10:42 AM
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You gonna eat that?
I did that to a Nishiki Olympic 12 a couple years ago. It broke my heart; I owned that bike since it was a baby in '84. I rode it like that until I found a suitable replacement bike. The Olympic 12 is now a parts queen and I don't ride it anymore.
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04-15-10, 12:05 PM
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That down tube could certainly be repaired. I think the biggest danger in riding it now would be if you are going fast and really need your front brakes, it could fail further. The front geometry is also changed which might or might not be bad.
One of my old lugged frames has a similar problem and I will probably eventually have it repaired and the entire bike repainted.
One of my old lugged frames has a similar problem and I will probably eventually have it repaired and the entire bike repainted.
04-15-10, 12:22 PM
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Until/unless it cracks it would take the almost the same amount of force to bend it further as it did to create the original buckle, ie. another collision. So that isn't an issue, the geometry and risk of crack propagation is, but that can be checked, and monitored. So it's OK to ride as a beater, but not worth putting dough into.
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An ounce of diagnosis is worth a pound of cure.
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WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
07-21-10, 08:08 PM
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Having had my share of 'road rash', I would advise against using a damaged frame. It might be OK, but how much is YOUR skin worth?
