Tern Link snapped in two.
 

Check your welds, folks. Fortunately I was unhurt.
https://cimg0.ibsrv.net/gimg/bikefor...123229279.jpeg

there were no signs of impending disaster: no creaks or cracks.

Oof, glad you are ok! If I recall, there was a big to-do about problems with the early Terns, including some tone-deaf responses from Tern before they issued a recall. What year is your bike? I wonder if was part of the bad batch?

That is scary. You were very fortunate that you weren't badly injured. Please let us know how Tern responds to this.

Do you guys reckon this is part of the reason Dahon has that Deltech cable now?

I suppose an aluminum hinge can only take so much flexing before it gives way, and if that bike's seat and tires are any indication, the bike has quite a few miles on it. (not blaming the rider at all)

I have no comeback with Tern.

I am the second owner and the bike is almost certainly more than 5 years old anyway (frame warranty limit)

I am not looking to throw Tern under the bus here (although their product literally nearly threw me under a bus). I am suggesting that Tern owners check the weld behind the main clamp carefully and frequently.

Perhaps there was evidence that the frame was about to let go? I don’t know. Anyway it’s surely worth doing to hopefully avoid a catastrophic failure.

Again, I am not preaching about helmet use here but I landed quite heavily on my head and was glad to have been wearing one.

Doesn't look like the hinge is what failed, it was the multiple tubes welded to the back hinge plate:

https://cimg3.ibsrv.net/gimg/bikefor...e8b3997098.jpg

I can't say either (of course!) yet quite a bit of the history of this frame is unavailable. You ride hard? Smooth pavement or cobbles, gravel? How that frame was treated had a lot to do with the nature of weld failure, as well as design parameters and production QC.

Glad you're unhurt (you had yourself checked for concussion after a hard heat impact?) and that you're bringing this to the attention of other Tern owners who may benefit from your having had such an unfortunate mishap.

https://cimg4.ibsrv.net/gimg/bikefor...16436f75d.jpeg
Here is a better photo of the failure point.

it gets ridden on all surfaces: tarmac, the odd flat tow path etc. It’s never been abused but yeah, it’s well used. I suppose it got ridden on the odd cobbled section in Brussels last year. It’s not been babied.

I have a bit of a headache but I think that was maybe dehydration too? It’s gone away after a few pints (of water LOL)

I tightened the hinge slightly last week. It was pretty loose, and I tightened it to Tern spec as per their online video. Would that have been a factor? Perhaps.

it certainly wasn’t stupidly tight after I gave it half a turn. It wasn’t as tight as the hinge on any Dahon I have owned, that’s for sure.

This is a great example of terrible design. You're just BEGGING for this to fail. Talk about a leverage arm going through endless fatigue cycles! Oh and let's use aluminum with limited fatigue life while we're at it!

Explains exactly why the triangle-truss design in bicycle frames has been so successful for two centuries.

Glad the OP wasn't hurt, killed, or worse :D!

PS OP, wie geht's in Frankfurt? Bald kommt Oktoberfest!
PPS Thanks for this PSA. Just sent a friend who owns the same bike your pics & a note to check that area!

Frankfurt is as always terrific, but I am currently on a job in London! The failure happened in East London, by Bow.

Well that took a....
Tern for the worst!

One of the downsides of aluminum is there is no set fatigue limit. It does seem though certain makers name surface here more often like Tern and Xootr. These bikes have a sportier ride and may achieve by having a lower factor of safety.

I was told by a friend of mine who worked as a mechanic at a bike store that a pizza shop in the French Quarter bought their bikes for their delivery service. Trying to find parking for cars in the Quarter being difficult. The bikes were aluminum would be used for seven years and retired as it was assumed they were fatigued to death. They were treated rather harshly since the drivers did not own them.

That said, planes are built out of aluminum. Those also are retired at a certain point.

In the past I had always favored steel frame bikes, because the ride seemed more forgiving. As tires became wider, and bikes were being designed that could accept them my view has changed. With 2-inch wide tires I am not sure if one can observe any difference. I bought my Xootr Swift after reading that Peter Reich, the designer had said that he could not tell the difference in ride from the steel and aluminum.bikes. I now try to remember to check for chain stay cracks under and near the bottom bracket. It requires turning the bike over.

looking at this, it seems there was very little weld peneration; the feeler was essentially acting as a glue keeping the hinge plate and the tube together. Unfortunately, this is the issue Tern got infamous for when they split from Dahon (that said, the light dahon frame like Mu SL cracked) ...

As OP said, there is very little to be done as it is out of warranty and has unknown traceability. As OP is currently in London, they may want to get in touch with CH White and see if they have a spare frame somewhere (they do not advertise all their stock)
https://foldingbike.biz/epages/7665e38c-067c-4fa0-9037-afac2266f927.sf/en_GB/?ObjectPath=/Shops/7665e38c-067c-4fa0-9037-afac2266f927/Products/BICKFRAMEFORKARGENT1808BLA

https://foldingbike.biz/epages/7665e38c-067c-4fa0-9037-afac2266f927.sf/en_GB/?ObjectID=1150266&ViewAction=ViewFaceted&FacetValue_CategoryID=1150266&CurrencyID=GBP&CurrencyID=GBP &FacetRange_ListPrice=&FacetRange_ListPrice=

or just order a FHon CrMo steel frame from Aliexpress

FWIW, Tern now has their bikes' designs certified by a third party. Probably this is the issue that led to it.

More than one thread showing Tern failures, and their lack of support for their products.

Too damn bad really.....

How much do you weigh?

Deltech: Damn right, I know it's a plus. Just the small welded attachments might not be robust enough on aluminum frames.

That frame may still be covered under the recall, a recall is not warranty, recalls last forever, and extend beyond the original owner, as it is a safety issue. It looks to me that the frame lacks the additional gusset on bottom forward of the hinge that is present on Dahon Mariner, and I believe was added to post-recall Tern frames, not certain. I ran across a Tern used at the bike shop and it was covered under the recall, I told the shop owner. I know the fracture happened aft of the hinge, but the recalled frames also had issues with weld quality IIRC. Look online for Tern's recall notice, check your frame serial number, see if it is covered.

That's why my first good new bike, '89 Cannondale 3.0 Crit racer in 6061-T6 aluminum, rode like iron, it needed to in order to last in fatigue. I was enamored of the cool look of the frame, but given more experience, I may have chosen a better riding frame. I was able to fit 26 or 28 mm tires later on, and that helped some. But the bike was fun in sprints.

A blast from my past. It was not the most supple ride.
https://cimg5.ibsrv.net/gimg/bikefor...3ffcfbc198.jpg

105kg

https://cimg8.ibsrv.net/gimg/bikefor...e2e0316b3.jpeg

apologies for the poor photo, I wanted to get rolling.

This is its slightly dusty replacement. A bit bigger than the dead one and in need of new cables and housing but it’ll do for now. Rides nicely on the 406/47 tyres.

What's the story with the replacement?

Nice. There's a Tern recall database somewhere where you can check your serial number

A famously failure prone Al-alloy Tern broke on your 105kg frame, and the replacement is a famously failure prone Al-alloy Tern for you 105kg frame? Are you familiar with the Darwin Awards?

A famously failure prone Al-alloy Tern broke on your 105kg frame, and the replacement is another Al-alloy Tern for your 105kg frame? Are you familiar with the Darwin Awards?