Cycling UK Forum

I've lost count of the amount of times I've advised people not to ignore creaks and clicks and to attend to them quickly in case you either make a small problem into a big one over time, or in case it's hiding something more catastrophic in the making.

So what have I been doing for the last 2-3 weeks? Yup, that's right, stubbornly ignoring the ever increasing volume of the clicking and creaking coming from my commuter.

Well it got a bit louder again this morning, and was happening while seated as well as standing and then I got a little bit of shimmy going down one of the hills on the way to work, alarm bells started ringing in my head so I stopped to check it over and discovered the crack that has now propagated about 1/3rd of the way around the downtube

Suffice it to say the rest of the trip was taken at a sedate pace and I'll be paying more attention to my own advice in future. Another commuter bites the dust

how old is the bike?

steel, aluminium, or what? IME aluminium tends to be noisy as it fails.

Good that it failed in a fairly benign fashion though; i.e. that the shimmy alerted you to imminent failure.

I had a similar (but silent) happenstance on my steel hack bike a couple of years ago, and I also climbed off to see what had made the bike so wobbly....

Tsk tsk, the frame was only ~50 years old too, no age....

BTW because I can, I welded my frame back together and I am still using it.... The joys of gas pipe...!...

cheers

how old is the bike?

Not very, ~18 months maybe, less than 2000 miles use though as it's not my default choice for longer trips.

Steel, a Charge MTB frame made from Tange Prestige tubing. From initial inspection (I'll look properly later) it seems that the crack has started near the end of a re-enforcing gusset under the downtube, didn't have enough time to check if it's started form a weld or not but I suspect it has. It's then propagated up and round the side of the tube as you would expect. Due to where it's started and how it's progressed it's not something I'd be happy welding.

Good that it failed in a fairly benign fashion though; i.e. that the shimmy alerted you to imminent failure.

Aye, true, but if I'd been more diligent I probably would have found the crack a week or two ago if I'd actually looked...

amediasatex wrote:
... but if I'd been more diligent I probably would have found the crack a week or two ago if I'd actually looked...

I felt exactly the same way when my frame broke.

I painted the repaired area a light colour so that I would see if it cracked again at the same point.

FWIW I would expect the crack to have started at the weld; I am not convinced by the usual gusset design BTW.

BTW doesn't your frame have a warranty on it?

cheers

I am not convinced by the usual gusset design BTW.

Same here, although I think it depends whether it's been properly designed and executed, I have a couple of Bontrager frames (one road, one MTB) from the 90s which are still going strong but Keiths gussets are notably different to many current off-the-peg frames.

BTW doesn't your frame have a warranty on it?

I'm looking into this as it was bought from eBay, BUT...from a business seller and described as 'new'. I've checked and it's actually younger than I thought*, 12 months and 5 days since purchase. I'm going to contact them and see what they say.

FWIW I would expect the crack to have started at the weld

That's my working theory too, I'd be very surprised if that's not the case. Might add some weight to any 'fit for purpose' discussions with the seller as can argue the 'inherent defect angle' of it.

*I initially bought one in a small size a few years earlier that got stored for a while, used it for a few months and liked it but then bought a medium as I felt it was a bit small for me. I swapped the frames over and sold the small frame on so this one has actually only had about 10 months use, and my GPS log for this bike says 2336 miles but that actually includes a few hundred miles on the small frame as I didn't bother starting a new log after the frame swap, either way that's not exactly a good innings...

seems like nothing in terms of mileage

so are you expecting contact from the person who bought the small one from you?

seems like nothing in terms of mileage

indeed, rather poor

so are you expecting contact from the person who bought the small one from you?

No, I doubt all the other frames have similar defect or else they'd be breaking left right and centre, and I know of several other people who've had the same frame for years with no issues so likely a QC issue/isolated fault.

Adding a reinforcing gusset to a prestige frame is a strange thing to do. Its heat treated steel, very thin with gauges specifically designed to cope with the forces each tube is subjected to. An additional 'layer' is a potential stress raiser as the transition from thick to thin creates wildly differing stress distribution in the metal and the material is prone to fracture.

For those that are interested here are few photos of the crack.






Thankfully the retailer has agreed to refund (they have no replacement options) and is sending a courier next week to collect it

From what I read elsewhere on the Forum.....how can this be true??? Steel frames go on for ever and ever and ever , only those appalling new inventions in alu and carbon fail in less than a 100 years......Oh dear.

the gusset that broke is a very bad shape indeed. The unbroken one on the top tube is a better shape, in that it has a deeper scallop, thus leaving the end of the weld (where there is liable to be a start/stop defect unless the weld is dressed) to see lower service stresses. Even so the stress reduction via small changes in gusset design applies mainly to bending stresses in the tube, rather less to torsional stresses, which a DT sees when hauling on the handlebars.

It is difficult to tell (because there is so much paint) but it looks as if the weld started at the point of failure. Unless dressed, there would almost certainly have been a cold lap at the weld start, giving

- a nasty stress concentration,
- a nasty microstructure, and
- a small unpainted region that could work as an anode once exposed to winter road salt etc

The corrosion aspect is important; the stress required to start or propagate a crack can be ~1/3 that required in the absence of such corrosion.

IME a crack like that would usually be small for a fairly long time, then run the last 1/2" or so in a short time, as short as a single ride. If you can check the fracture faces for corrosion, you can gauge how old various parts of the crack are by how much they have rusted.

The gusset on the top tube is a better shape but it is (to my eyes) the wrong way up, in that the crevice between the gusset and the tube will more easily trap rainwater and will start corroding PDQ. I'd treat areas such as those with waxoyl, run in molten with a hairdryer.

cheers

From what I read elsewhere on the Forum.....how can this be true??? Steel frames go on for ever and ever and ever , only those appalling new inventions in alu and carbon fail in less than a 100 years......Oh dear.

Well, this is the 14th Frame to die under my 'care' in the last ~20 odd years, and the 18th time I've cracked or snapped one (some frames broke more than once), breakdown as follows

5x Steel (2 broke more than once)
7x Alu (2 broke more than once)
2x carbon
No Ti breakages...yet, but I've owned fewer Ti frames.

It's a got a lot more to do with design, execution and circumstance than material.

IME a crack like that would usually be small for a fairly long time, then run the last 1/2" or so in a short time, as short as a single ride.

I think that's exactly what happened here, The crack round the side and over the top of the tube is what appeared very quickly, it's easy to see from the faces that the initial crack was around that weld/point on the gusset and it looks like the crack 'under' the gusset is a little older, and probably hence why I didn't spot it early, but it was making noise, a cursory glance would miss it under there, I only noticed it had cracked under the gusset too when I looked properly after spotting the 'new' bit of the crack round the side.

Anyway, we can learn something from every failure

EDIT - glad nobody commented on my horrific mudguard mounting bodge on the fork

amediasatex wrote: It's a got a lot more to do with design, execution and circumstance than material.

yup, totally agree.

EDIT - glad nobody commented on my horrific mudguard mounting bodge on the fork

I tried to avert my gaze and not think too hard about it....

cheers

I tried to avert my gaze and not think too hard about it....

It was a late night 'make it work before work tomorrow' bodge, and then I was too lazy to sort it out ~9 months later and it's still there