AAARRGGH my Downtube is dead!
 

Cycling home from work this morning the frame split in two at the seat tube, sending my handlebars one way and the seat post the other, no bruises but my downtube days are over boo hoo.

Its been my everyday commuter and i've cycled from north london to brighton and taken it folded in the car on holiday several times. i will miss it greatly.

just wanted to say a big thanks for all the advice and ideas gleaned from this forum. i've needed to refer to this site several times as parts wore out and problems arose.

oh dear, now i'll have to buy something to stick all the parts on.

thanks again

Holy smokes! That sounds scary! Glad you're not hurt.

It's quite distressing to hear that the frame split, though :eek:.

Sorry to hear that! I had a similar experience with one of my bikes, although I did get a few bruises & scratches, but was just shaken & very surprised really. Sounds like you're ok fortunately.

Can you post a pic' of the broken bike please, as it'd be interesting to know what to look out for?

How long did you have it for?

+1 pics please. Is there a guarantee on it?

Better ask Yan!

Attachment 59144

Attachment 59145

the bike is outside the 1 year warrenty supplied by downtube.

For some reason i'm very calm about the loss. Its roughly 1 and a half years old and i would have expected it to last longer but i bought it as a cheap introduction to city cycling and now i know i need more.

The frame is going in a skip but i'm going to keep the parts in case a project comes along. it wasn't that long ago i had to replace the fork and headset.

thanks for the concern voiced above, thinking about it, it could have been worse.

Did it break where the seat post ended?

Wow, a 1 year warranty on the frame is pretty crappy. Even Dahon has a 5 year warranty that gets extended to lifetime if you get a shop to do a look-over at purchase time.

Glad to hear that you're taking it well. Time for a Brompton?

Don't they only have a 30 day warranty for their ebay auctions too? Why such a short warranty if the product is so good?

Time for a Brompton?[/QUOTE]


funnily enough, i'm just about to move out of london to suffolk and was thinking of getting a smaller folder for the commute, so yep, maybe time for a brompton.

I'm also curious about how far the seatpost was mounted/inserted and if this has anything to do with the breakage.

the break point doesn't mark the position of the end of my seat post. in fact the seatpost ran through both parts of the seat tube keeping the frame together.

Is it an aluminium frame?

Because it's not that kind of good. Don't get me wrong, they are good bikes for the money, but you get what you pay for.

That's not to say that everyone should go drop two grand on a Bike Friday or a titanium Brompton. There's no point spending a lot of money on a bike that will last forever if you're just going to get a new one to better suit your more discerning tastes after a year or two. There's also no point spending a lot of money on a bike that's going to be abused (flying with a softcase, commuting in all weather, haphazardly locking outside, etc).

I bought my Downtube as a starter bike based on the recommendations of this forum that a bike can be a good primary mode of travel as opposed to simply a tool to enhance other modes of travel. However, enhancing other modes of travel was my primary objective and for that I splurged for a high quality bike like the Carryme (which actually wasn't much more expensive than my Downtube because it is, despite its quality, a much simpler bike).

Now that I've seen the difference that quality makes and I ride almost everywhere I'm ready to fill my newfound need with either a Bike Friday Tikit or a Pacific Reach Swivelhead. I still think my Downtube is a great bike. I couldn't have come to appreciate the usefulness of a larger folder without it and it will continue to be a great bike for flying with a soft case, commuting in all weather, haphazardly locking outside, experimental home mechanicing, etc. It is within this niche that the Downtube is a great bike and I don't think the short warranty detracts from it nor do I think that a more expensive bike with a better warranty (or a cheaper bike with a terrible ride) could better fill it.

In my opinion, the Downtube is the best first folder and the best beater folder. If that's not a good product then I don't know what is.

Just my 2c.
[/end rand]

Yep.

-G

barneybarney ... Glad that you are OK. Could have been catastrophic.

More generally, we should be careful to avoid over weighting a single event when making inferences about the entire product line. As regular forum members know, there have been some reports about failures on Dahon bikes; but my bet is that in large their bikes perform well and have a high reliability. Much of this, in my opinion, is due to earlier failures and the negative publicity that resulted. Similarly, we know that there are likely a few bad eggs in a long production run of Downtubes. Whether it is systematic problem, like apparently the Xootr Swift Folder frames suffered before an apparent redesign (I recall that there were failures around the top of the seat tube as well ... although the memory is fuzzy), remains to be seen.

That written, I agree that they are good bikes for the money. They can be excellent bikes with a serious component upgrade. My guess is that most production frames--whether from Dahon, Downtube, Xootr--are pretty robust.

Why not have it welded? That could be fixed for US$50; less if you shop around - repair will be STRONGER than the surrounding area too...

FWIW, I've watched "my guy" cut a Pepsi can in half and weld it back together...

From one who had a Dahon fail, I think you're mostly right. Most Dahon bikes come from China, I'm guessing Downtube and the mass-production Xootrs are similar. The problem there is quality control. The average frame can be great, but the odds of getting one with a defect are higher than with a bike from a company with better quality control. The many frames that aren't defective are great.

Dahon (and others) have a decent frame warranty period. They correctly replace broken frames as an acceptable cost of their cheaper manufacturing methods. I'm still surprised Downtube only has a one-year warranty.

You know, this type of failure this really raises some questions. I know Yan is a professor and has way more schooling than I do, but when you look at that part of the frame, you can see where there is going to be a problem. Why doesn't the frame have some sort of gusseting there? Ideally, you'd want the rear triangle to meet the crosstube to reduce the moment and shearing load in the seat tube. I realize that this has to be balanced with support for the actual seat post, which gives us our problem, but this is something that _has_ to be addressed. It's not an acceptable issue.

When people get hurt, they generally don't get hurt the first time that a problem occurs. The first couple times a certain problem occurs, they get away with it and ignore it thinking to themselves, "Well, that could have been bad!". Well, that could have been bad. Now before the next guy has the same problem, get's pitched into traffic, and is run over a 'fix' needs to be in place.

I totally agree. It seems most everyone who has responded to this post is not seeing how dangerous this type of failure can be. If I went to Walmart and bought a cheapo MTB for $50, I'd expect this type of failure-- but not on a Downtube. Sure, things happen from time to time, but I wonder how often this type of failure has occurred and what Downtube is doing about it, if anything.

Quality control? It did not break at the welds. Are you going to blame them for the quality of aluminum as well?

As with the other bikes mentioned above, maybe their failures have more to do with their designs (which are done in the US) than anything else.

Agreed! But this ain't the Space Shuttle we're talkin' about...:)

No - it's a simple tubular structure that you stake your life on. It has no emergency systems, no telemetry, no parachute, and if it breaks again you may find your digestive system spread all over the road because a truck disemboweled you, smashed your limbs and stood throbbing over the top of bits of your corpse while the emergency services tried to extract the rest from up around the prop shaft.

I've never heard of anyone repairing a cheap aluminium frame by welding. First it is difficult to do safely, and second, what's the point? Its just about the cheapest bike on the block. When it dies, it's dead, and it owes nobody anything, does it? Much better to buy another one.

http://blogs.kansascity.com/photos/u...accident_1.jpg

http://www.community-newspapers.com/...ages/cover.jpg

Umm, yes it did.

The weld either weakened the metal by using too much heat, or left a space/nick which served as a stress concentrator and led to the failure.

If their tubes are failing outright, Downtube has a much bigger problem on their hands... And yes, if their aluminum was that bad, I'd blame them for it too.

Why do you expect it from a Walmart bike, but not a Downtube? After all, the cheapo folders at Walmart cost about the same as the cheaper Downtubes (especially if you consider the ebay ones).

Why not? Isn't securing decent materials part of the job of building a bike?

Load question
 

Please forgive my asking, but how much did the rider weigh at the time of the breakage?

I'm thinking many here suppose that Yan didn't bother to check. This might be true, and if so, would be very short-sighted on his part, esp. if he's trying to make a name for DT. Another possibility is that the manufacturer could have baited and switched materials. We'll see how this pans out.

You may be right; I take that back.

What still needs to be determined though is if DT's "tubes are failing outright" or if this is related to how the OP uses the bike. As a fellow commuter, I know how I treat my IXFS esp. now that I don't use public transportation anymore, and enjoy the challenge of getting home as fast as I can. :D

If you look at the first picture, you can see that one end of the shear starts at the edge of a weld. It doesn't go _through_ the weld, it starts right at the edge. This is called the 'heat affected zone' (HAZ). I'd bet the farm that this weld was undercut(not enough filler) and that was the initiation point.

You don't need a problem all the way through the tube....all you need is one 'dotted line' and time will take care of the rest.

I will say that before this actually broke, I would suspect that there was at least some sort of tell-tale signs going on if the owner would have inspected everything very closely. Probably this would have been more closely than normal. I would also think that there might have been a few seconds of the bike really moving around under the rider before it actually let go. But, since there isn't much bending in the ends of the tubes, it very well might have been a sudden brittle fracture.

My guess is that you could weld this, gusset the tubes a bit and get a fair bit more time on the bike. It would take a decent fabricator to do it, but they aren't _that_ hard to find. The bike is 6061 AL if I remember right, and that's a very common alloy that is easy to weld. Once it's welded, it will be no stronger or weaker than it was previously (except for the possibility of an undercut weld). The gusseting would made a big difference, though.