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Would you use this cracked frame?

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Would you use this cracked frame?

Old 08-04-20, 05:21 PM
  #1  
ddeand 
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Would you use this cracked frame?

So, I got this aluminum bike knowing that it has two cracks in the frame - the parts were interesting and the price was right. I would like to build up a bike for use on my fluid trainer for this coming winter since I donít want to go to the YMCA for my usual off-season spin classes. The bike I build up will NEVER see the road - it will only be used in my basement on the trainer. One crack is along the top of the down tube and is about 3 inches long. The other crack is on the head tube and is about 2 inches long. I have no idea how those cracks came into existence. My question is would any of you consider using this frame on a trainer or would you look for something else? Opinions appreciated.


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Old 08-04-20, 05:33 PM
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I wouldn't ride a bike with even a rumor of a crack or a "pristine" carbon frame of unknown provenance. However, for a trainer I'd drill the ends of those cracks, wrap the business in some sort of epoxy tape and have at it.
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Old 08-04-20, 05:34 PM
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Pull the fork for some future project. make a stool with the shell, ST and rear end and toss the rest. Andy
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Old 08-04-20, 05:52 PM
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On a trainer, probably. Anywhere else noooooooo. But I'd be looking for some other cracks first and keeping a good eye on it regardless. I mean what's the worst that can happen on a trainer?
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Old 08-04-20, 06:16 PM
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Originally Posted by Andrew R Stewart View Post
Pull the fork for some future project. make a stool with the shell, ST and rear end and toss the rest. Andy
if the forkís been through the same hell as the rest of the frame, Iíd be hesitant to use it for anything, even if thereís no obvious damage
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Old 08-04-20, 06:33 PM
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Originally Posted by Litespud View Post
if the forkís been through the same hell as the rest of the frame, Iíd be hesitant to use it for anything, even if thereís no obvious damage

The fork looks to made of steel, not more crack prone Al. I also suspect the fork was from another factory then that of the frame, as is often the current outsourcing manor. Andy
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Old 08-04-20, 06:54 PM
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A couple of rolls of Gorilla Tape around the head tube and you'll be all set.

What kind of trainer do you have? I presume you're not using rollers, but rather some kind of rear wheel trainer (either replacing rear wheel, or locking rear wheel in dropouts).

I'd be tempted to use that bike ONLY on the trainer. No last minute grabbing it as a spare commuter.
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Old 08-04-20, 06:57 PM
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put abide clamp on that headset tube.
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Old 08-04-20, 08:45 PM
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I'd be tempted to use that bike ONLY on the trainer. No last minute grabbing it as a spare commuter.
My basic plan is to set it up with flat bars, probably no brakes, rear derailleur, rear downtube friction shifter, spd pedals, basic computer on the rear wheel, and comfy saddle. It will go on a Kurt Kinetic Road Machine fluid trainer. I just don’t want to submit my other bikes to the wear and tear to the drivetrains on a trainer. I’ll keep mulling this over. Thanks for the suggestions.
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Old 08-05-20, 10:14 AM
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I'm with Andrew and Litespud on this. You bought it for the parts, take the parts off. The bike's almost certainly been in a wreck.

Originally Posted by Trevtassie View Post
I mean what's the worst that can happen on a trainer?
Can happen? How about the downtube shears the rest of the way, cuts through any tape you might have put on as a band-aid, and slices a nice gash in your leg?
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Old 08-05-20, 11:19 AM
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Put a steel worm screw band on the headtube, much stronger than any tape would be. As to the down tube crack: use a sharp
pointed center punch to dimple each end of the crack and drill ~3/32" hole there. This will reduce the risk of propagation of the
crack. FWIW back in the '70s I crimped a downtube at the shifter bosses (ran into curb) eventually it broke, got welded and
ridden for a time. About 15-18 miles from home the down tube split in half a year or so later. Had to ride it to get home so used
some 14g copper wire to bind the top tube and down tube together, kind of bouncy but I was able to get home. No injury, no crash
just a WTF and then a search for wire or something.
I think it is ok to use on a trainer, especially if the fork really is steel, especially the Kurt kind where the front wheel just sits on
the floor and the rear is clamped in place. Just don't do any 1200 watt standing sprints or maybe even 800watt.

Last edited by sch; 08-05-20 at 11:23 AM.
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Old 08-05-20, 02:12 PM
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I wouldn't use it at all. Even on a trainer the crack in the head tube might let go and allow the fork and front wheel to shoot forward. A faceplant off a trainer is only slightly better than a faceplant on the road.
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Old 08-05-20, 02:21 PM
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Sure, I'd ride it on the trainer, I'd mark the crack ends with marker or tape and perhaps make an adjustment to my trainer setup so if I fell, I wouldn't suffer serious injury. If I did hit the deck, how hard can I hit it at 3 mph? (A sprinter's lunge.)
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Old 08-05-20, 02:52 PM
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I'm with the "trainer use only" club.
How I've patched non-bicycle things before was to tightly wrap the tube or with enamled magnet wire or copper clad steel (because that is what I had on hand) & made sure to impregnate the windings with JB Weld or similar epoxy. However you do the lay up, I would think at least 2 layers ought to be perpendicular to the crack with ample wrap extending beyond the crack area itself if possible. It can be a messy process if you are not careful. But the result is a wire reinforced epoxy composite structural band-aid. If you can wrap it tight enough to close the crack, so much the better. Then you *know* the stress is off the defective area & bourne be the new wire reinforced epoxy composite.

I like the hole idea. It's how we would repair aricraft when they'd come in. The trick is finding the actual real end of the crack, not just where it looks like it stops. If you have a reamer available, that would be preferred over a standard consumer grade single margin. But this is not an aircraft, so going with what you got is better than nothing at all. Removing any surface coating down to bare should go with out saying. And of course, proper relief/smoothing of the hole edges so stress has no place to gather.

Probably overkill for a trainer, but the materials are super cheap & the risk is minimal. More involved than a hose clamp though.
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Old 08-05-20, 04:23 PM
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Wife rode this for a while (headtube crack). After you drill the end of the crack it will stop spreading. You may have to remove paint to verify the real end of the crack.


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Old 08-05-20, 07:11 PM
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Wow definitely two camps here. For me, I'd be worried that the bike has beed pretty abused and what else is hidden under the paint. Those cracks are HUGE. I woild not ride it even on a trainer like it is, and even if all of these repair suggestions would work, I woild not waste my time Rube Glldberging them together. I'd go to a local coop or search on Craigs List for a frame that suits me better and send that frame to to be recycled for a new life as a Cannondale or a Tesla, or as Reynolds Wrap...
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Old 08-05-20, 07:32 PM
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Originally Posted by ClydeClydeson View Post
I wouldn't use it at all. Even on a trainer the crack in the head tube might let go and allow the fork and front wheel to shoot forward. A faceplant off a trainer is only slightly better than a faceplant on the road.
It took eleven posts to get a sensible response. I suppose if you're just spinning on a trainer, ok. But if you're doing any sort of intervals or sprints, no way! If you do, you probably won't get a Darwin Award but consequences could be nasty.
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Old 08-06-20, 06:56 AM
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While I go with the worm clamp and drill crew I also think I'd start looking for another cheapo frame to transfer parts over too. Having it let go on the trainer isn't as bad as it letting go while going 30mph down a hill but it would still suck.
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Old 08-06-20, 07:36 AM
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Originally Posted by 79pmooney View Post
how hard can I hit it at 3 mph?
Where do you get the 3mph from? On the Earth where I live, acceleration due to gravity is approximately 9.8 m/s^2, so falling from atop a bike would see you going quite a bit faster than 3mph.
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Old 08-06-20, 07:42 AM
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Yeah, I wouldn't do it. Especially if you're doing anything other than really low effort spinning on the trainer.
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Old 08-06-20, 07:46 AM
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ahhh hard no! Dental work is costly.....
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Old 08-06-20, 07:46 AM
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I have a Dahon with a cracked seatpost tube. I drilled a hole at the end of the crack and have ridden it for 1500km without issues.

I wouldn't ride your frame though. It seems like a really long crack in places that are crucial to safety. Also, I definitely wouldn't buy a Dahon again.
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Old 08-06-20, 02:50 PM
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[QUOTE=pdlamb;21625031Can happen? How about the downtube shears the rest of the way, cuts through any tape you might have put on as a band-aid, and slices a nice gash in your leg?[/QUOTE]

No offense but you and some others sound like insurance salesmen.

It doesn't look like its been in any accident, probably was made from some 'chinese aluminum' and the cracks are from tired material. On a bike trainer, this frame might still have some future, unless you are in your prime age and are stomping on the bike like a wannabee pro racer. for peace of mind, you can put metal clamps on the offending parts (those you normally put on a car radiator hose to hold it in place) and maybe also drill those crack ends as advised above (I suppose you know what that's about) if you don't mind the resulting frankenstein looks.

But I also like that idea of a shop turntable...
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Old 08-06-20, 03:00 PM
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Originally Posted by fooferdoggie View Post
put abide clamp on that headset tube.
The tube abides?
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Old 08-06-20, 11:43 PM
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I don't see a way to hose clamp the HT..... So off to the gaRbage it goes....Hasta la vista.
Way more than dangerous, IMO.
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