# My bike broke in half......



## FrankCrank (9 Jan 2020)

......luckily not going at speed or I'd have ended up in hospital, or worse. Had the thing a dozen years more and always felt flexy, so guess it's a classic fatigue crack. Won't be getting this type of folder again, least not in aly. This one is a rebadged Dahon, Tern made similar ones as well. I'm around 13 stone, a bit podgy I admit, but within the weight limit for this type of bike. Anyways, a heads-up to anyone owning similar


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## MontyVeda (9 Jan 2020)

It'll be fine with a bit of gaffer


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## PeteXXX (9 Jan 2020)

That could have been painful!!


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## LCpl Boiled Egg (9 Jan 2020)

I can't believe silver gaffer tape was suggested to fix this...



You can get dark blue you know


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## ianrauk (9 Jan 2020)

Blimey.


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## Cycleops (9 Jan 2020)

Sorry. I'm sure a structural engineer in this field will tell us it was an accident waiting to happen.
Looks like all the stress concentrated in one place.


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## Accy cyclist (9 Jan 2020)

Maybe the bike was a cut and shut.


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## Kell (9 Jan 2020)

I wouldn't buy an aluminium frame again.

The only two alu bikes I've had - both the frames cracked. 

Luckily neither was a complete through-and-through like that.

Glad you're OK.


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## numbnuts (9 Jan 2020)

Drop of superglue and she'll be right


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## EltonFrog (9 Jan 2020)

That must’ve given you a start! Were people watching?


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## classic33 (9 Jan 2020)

Any track of failure on the weld? 
The bottom left looks darker, but that may just be the photo.


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## FrankCrank (9 Jan 2020)

We were on hols in Koh Chang when it happened. I take a morning ride a few miles to a posh resort and plonk myself on a sunbed for ten minutes or so. When I got back on the bike and started pedaling, that's when it gave way. Luckily nothing hurt but my pride, and no one saw it, and it was the last day of the hols. Left the bike lying there in disgust whilst Mrs Crank was summoned to rescue me in the car. She took ages getting to me as it was quite early. The resort is exclusive for Russians, and by now a few were up and walking past giving the bike strange looks and wondering what happened. Anyways, I'll strip the bike of all its parts and recycle them onto another project. I've got a Raleigh Twenty here that'll be my new travel bike - over engineered and built to last, they knew how to make a sturdy bike back then that's for sure 

PS - The break looks clean, no track of failure. With steel you get some warning of imminent failure, but aly is different, and then there's carbon


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## 12boy (9 Jan 2020)

Boy, did you luck out. Imagine going downhill at speed....I am glad you are ok.


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## BoldonLad (9 Jan 2020)

FrankCrank said:


> We were on hols in Koh Chang when it happened. I take a morning ride a few miles to a posh resort and plonk myself on a sunbed for ten minutes or so. When I got back on the bike and started pedaling, that's when it gave way. Luckily nothing hurt but my pride, and no one saw it, and it was the last day of the hols. Left the bike lying there in disgust whilst Mrs Crank was summoned to rescue me in the car. She took ages getting to me as it was quite early. The resort is exclusive for Russians, and by now a few were up and walking past giving the bike strange looks and wondering what happened. Anyways, I'll strip the bike of all its parts and recycle them onto another project. I've got a Raleigh Twenty here that'll be my new travel bike - over engineered and built to last, they knew how to make a sturdy bike back then that's for sure
> 
> PS - The break looks clean, no track of failure. With steel you get some warning of imminent failure, but aly is different, and then there's carbon



First of all, pleased to hear you suffered no injury (except, perhaps, to your pride).

Presumably the bike was transported from UK, in aircraft baggage hold? I am no expert, and, I am not excusing the failure, but, I wonder if significant, and, perhaps, rapid, temperature changes could have contributed to the failure?

Just a thought...


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## Reynard (9 Jan 2020)

Eeek! 

It's been a while since I did any metallurgy (I'm a composites gal myself) but am wondering if there was a flaw in the weld right from the get-go if it always felt a bit bendy. It only needs one teeny tiny speck of dirt in there, or one air bubble to initiate a crack in the metal when the structure is under load. And then chuck in the fact that the failure occurred at one of the major stress points. Stress concentrations will always make any flaw worse - anywhere else on the bike and it may well not have broken.

Glad you are undamaged though...


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## Smudge (9 Jan 2020)

What makes you think its a rebadged Dahon ? 
I've never seen a Dahon with a frame like that, or a Tern come to that. I know Tern had a spate of their folders breaking at the main hinge, but this was after they parted from Dahon.


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## RoubaixCube (9 Jan 2020)

A bit of FlexGlue™ will solve that.


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## FrankCrank (10 Jan 2020)

The bike was bought locally here, place of manufacture unsure, and I presumed it was a Dahon clone as Sunzone throws up virtually no info, Dahon were/are the biggest manufacturer of folders. I also heard of Tern having similar failures. The flexing I think was a combo of the folding/rising stem, and the frame design itself. I would be happy to ride a steel folder, but not aly after this. My R20 is a non folder, but will fit in our Jazz no problem. Anyways, it's not something I want to dwell on, just draw a line under it and move on. As I said - a heads-up to anyone with a similar bike.


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## classic33 (10 Jan 2020)

FrankCrank said:


> We were on hols in Koh Chang when it happened. I take a morning ride a few miles to a posh resort and plonk myself on a sunbed for ten minutes or so. When I got back on the bike and started pedaling, that's when it gave way. Luckily nothing hurt but my pride, and no one saw it, and it was the last day of the hols. Left the bike lying there in disgust whilst Mrs Crank was summoned to rescue me in the car. She took ages getting to me as it was quite early. The resort is exclusive for Russians, and by now a few were up and walking past giving the bike strange looks and wondering what happened. Anyways, I'll strip the bike of all its parts and recycle them onto another project. I've got a Raleigh Twenty here that'll be my new travel bike - over engineered and built to last, they knew how to make a sturdy bike back then that's for sure
> 
> PS - The break looks clean, no track of failure. With steel you get some warning of imminent failure, but aly is different, and then there's carbon


I'd say it's the weld that has failed, not the frame tube.


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## Low Gear Guy (10 Jan 2020)

This design of bike puts a lot of stress at that part of the frame. Very few folders of this style are used for significant distances and are usually seen pootling around caravan parks and along the seafront. I think you have basically worn the bike out after ten years use. For regular use of a folding bike the steel Brompton is more sturdy.


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## Smudge (10 Jan 2020)

To me it looks like a generic no name folding bike, of which many are sold in supermarkets, market sellers on Amazon or Ebay, or box shifters on the net. They are the BSO's of the folder world. Dahons are much better made than folders like this, in their frame design and manufacturer. People have extensively toured on Dahons and rode around the world on them. But on alu folders, particular attention needs to be paid to the fold mechanisms, they need to be maintained and adjusted correctly so there is no play in them. But that wont help poor manufacturing and poor welding such as you often get on no name bikes.
I'd say you did well to get 12 + years from this Sunzone.


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## SkipdiverJohn (10 Jan 2020)

Smudge said:


> To me it looks like a generic no name folding bike, of which many are sold in supermarkets, market sellers on Amazon or Ebay, or box shifters on the net. They are the BSO's of the folder world.



Whenever I acquire anything bike-shaped to ride, the first thing I do is make sure the frame is made of steel. I only get ali framed bikes as scrappers to strip for parts, never to ride. The frames always get binned. Single downtube folders are the worst possible structural design, and the folding flange joint is going to be subjected to massive numbers of bending stress cycles every time the tyres go over bumps, or the rider accelerates or brakes. Steel is the only material that can be trusted to survive that sort of loading without fatigue failure. I'm surprised the ali frame lasted as long as it did, TBH. You wouldn't catch me riding an ali frame with only a single tube keeping the two halves of the bike apart.


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## Smudge (10 Jan 2020)

SkipdiverJohn said:


> Whenever I acquire anything bike-shaped to ride, the first thing I do is make sure the frame is made of steel. I only get ali framed bikes as scrappers to strip for parts, never to ride. The frames always get binned. Single downtube folders are the worst possible structural design, and the folding flange joint is going to be subjected to massive numbers of bending stress cycles every time the tyres go over bumps, or the rider accelerates or brakes. Steel is the only material that can be trusted to survive that sort of loading without fatigue failure. I'm surprised the ali frame lasted as long as it did, TBH. You wouldn't catch me riding an ali frame with only a single tube keeping the two halves of the bike apart.



Obviously a folder, by its very design, isn't going to be as strong as a normal bicycle frame. But if you need a bike to fold thats what you have to have. Also not all alu framed folders are created equal, you get well made ones and crap made ones. In fact that goes for any alu framed bike, folder or not. Plus steel framed folders like Brompton aren't exempt to breaking, incidences of that can be found.
I'm quite happy with alu frame bikes and i've not had one break yet in decades of cycling.


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## SkipdiverJohn (10 Jan 2020)

I know steel can and does fail; I had a 28 year old Raleigh hi-tensile frame crack a chainstay last year. It gave me some warning though as it felt "funny" to ride for a short period before it actually went. I still managed to complete my 16 mile round trip on it even after failure two miles in, just by using a fairly low gear and not putting too much force through the pedals to minimise flex. What I don't like about alu (or carbon fibre) is that it is prone to sudden failure without much if any warning, which makes failure potentially more dangerous. I was taking it easy and keeping my speed down on my old hack bike when it failed, because I had a feeling something wasn't quite right.


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## Gunk (10 Jan 2020)

Don’t worry it’ll polish out 😂


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## FrankCrank (11 Jan 2020)

Thanx for all the replies folks. Been busy since I got back from hols and not had a chance to strip the bike of parts and take a closer look. Initially it seems like a weld failure rather than the adjacent tubing, and the the weld itself looks very neat superficially. My (sizable) gut instinct is the frame design itself is not good, as mentioned by others, it puts all the loading right at the main frame hinge. I think the reason I got a dozen years from it is because of using it as a travel bike, ie taking it in the car to wherever, rather than a daily plodder. When I first got the bike, I'm sure I read that Sunzone was a spinoff of Dahon, they were becoming very fractious at the time due to 'internal differences'. Anyways, it was yonks ago and memory all a bit fuzzy on that. Apologies to all Dahon fans if I got that bit wrong. If I see anything else under the magnifying glass worthy of mention I'll do another update, but for now thanx again for some great feedback


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## presta (11 Jan 2020)

SkipdiverJohn said:


> I know steel can and does fail


The difference between steel and aluminium is that steel has an endurance limit, and aluminium doesn't.

Steel will tolerate and unlimited number of stress cycles if the stress magnitude remains below the endurance limit, but with no endurance limit, aluminium will always fail eventually, no matter how low the stress.


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## A V Lowe (11 Jan 2020)

Taiwan companies offer a pick & mix of frames & parts like this

Aluminium alloy (no one uses pure Al) is a eutectic - mainly of Al & Cu which has weak grain boundaries that present no resistance to crack propagation, unlike steel - filled with filthy carbon & carbon-iron (perlite) which will give ages of creaking & flexing before the residual section can no longer carry the loads, so you can 'see' key clues, like paint flaking off where the substrate has cracked, or rust stains, where water has got in.

I avoid Al parts wherever possible from the picture there is a dark area (corrosion?) where there may have been a scratch or nick that presented a stress raiser from which the crack grew. Welding = HAZ = local changes in material structure = high risk of crack generation. Presumably the first frame you've snapped. I've lost count...


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## 12boy (11 Jan 2020)

I also prefer steel, although I have 3 Al bikes right now, a Cannondale mtn bike, a Fuji flat bar road bike, and a Xootr Swift folding bike. I don't think they will fail anytime soon but they are not made like the OP's bike. I have never had an Al stem, handlebar nor seat post break either. A Dahon Speed P 8 is chromo and a used one should be fairly inexpensive if a Brompton is too spendy. Those old Raleigh 20 are pretty cool too.


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## FrankCrank (12 Jan 2020)

A V Lowe said:


> Taiwan companies offer a pick & mix of frames & parts like this
> 
> Aluminium alloy (no one uses pure Al) is a eutectic - mainly of Al & Cu which has weak grain boundaries that present no resistance to crack propagation, unlike steel - filled with filthy carbon & carbon-iron (perlite) which will give ages of creaking & flexing before the residual section can no longer carry the loads, so you can 'see' key clues, like paint flaking off where the substrate has cracked, or rust stains, where water has got in.
> 
> I avoid Al parts wherever possible from the picture there is a dark area (corrosion?) where there may have been a scratch or nick that presented a stress raiser from which the crack grew. Welding = HAZ = local changes in material structure = high risk of crack generation. Presumably the first frame you've snapped. I've lost count...



Yes, first frame I've snapped, if it was me you referred to? Actually, the Raleigh Chopper I had as a kid needed a repair weld carried out, but it wasn't snapped in half. Quite a big gap between snaps 
Got the frame stripped now, married the two halves up and looks like a very clean break, with no obvious flaws or trigger points (photo may be deceptive). I can weld stainless and mild steel, not alu, not that I'd even attempt to in any case. Just keep it as a conversation piece  The Raleigh Twenty I have here is from '77, and I have another in UK from '80 awaiting modernisation. Both are non-folders, but I think it says something about the longevity of steel.


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## simon the viking (12 Jan 2020)

I can't believe that people are suggesting mending this with gaffa tape or superglue! Its a weld gone! Wheres the safety factor! It would break again as soon as he sat on it..

Everyone knows for a break like this cable ties and a wooden stick are the answer... sheesh... bodgers


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## 12boy (12 Jan 2020)

Frank, I presume you have read Sheldon Brown on Raleigh 20s? Bitchin rides in there.


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## FrankCrank (13 Jan 2020)

12boy said:


> Frank, I presume you have read Sheldon Brown on Raleigh 20s? Bitchin rides in there.


....yeah, no worries, I'm a fan of them now for sure. Twenties were Raleigh's best selling bike, there must be so many languishing in the back of garages looking sorry for themselves. It is 2020 after all, so dust off that Twenty and give it a new lease of life - definitely deserves it


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## doginabag (13 Jan 2020)

If it is going to fail, it's not an unexpected place for it to happen. When aluminium is welded, it's limit stress reduces to around 50%, depending on the grade.

when you stick a hinge int he middle of a the frame where the bending stresses are at their highest, you will end up needing a tube sizes twice the size of what you would need if the frames was continuous without any welded joints to compensate.


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## 12boy (13 Jan 2020)

Here is my Al folder, a Xootr Swift. It's frame is fairly stout and the seat post, which holds it together is fairly thick. Earlier Al Swifts had breaks where the chainstays crossed the seat post and later ones such as mine, have beefier ones. Note the gusset below the head tube/top tube.
This is a very rigid little bike, although the wheelbase is actually the same as many hybrids.
area.


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## Schwinnsta (13 Jan 2020)

doginabag said:


> If it is going to fail, it's not an unexpected place for it to happen. When aluminium is welded, it's limit stress reduces to around 50%, depending on the grade.
> 
> when you stick a hinge int he middle of a the frame where the bending stresses are at their highest, you will end up needing a tube sizes twice the size of what you would need if the frames was continuous without any welded joints to compensate.


I think it likely that the heat treat takes place after the welding.


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## doginabag (14 Jan 2020)

Schwinnsta said:


> I think it likely that the heat treat takes place after the welding.


It's possible, and maybe more likely in a high end product, but in my experience it's not the norm. 

It isn't an issue as long as it is considered during the design, but if there is going to be a failure, the heat affected zone is where you would expect a failure to occur. 

Some info and strength tables here, I would expects most bikes are made from a 6xxx grade.
https://www.esabna.com/us/en/education/blog/the-haz-in-aluminum-welds.cfm


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## confusedcyclist (28 Jan 2020)

Kell said:


> I wouldn't buy an aluminium frame again.
> 
> The only two alu bikes I've had - both the frames cracked.
> 
> ...


You might be disappointed to hear this, but all frame materials fail... eventually.


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## Kell (28 Jan 2020)

confusedcyclist said:


> You might be disappointed to hear this, but all frame materials fail... eventually.



Of course, but as said, with steel it's never quite as dramatic and is often repairable. 

Of those bikes, one had been ridden for less than 4 years, the other for less than a year. I don't really see that as acceptable. 

The only caveat is that I found out later (i.e. after both bikes had cracked) that the rider weight limit was 95kg. Which is/was my weight almost to the gram.


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## confusedcyclist (28 Jan 2020)

Aluminium, if constructed correctly should give many years of service, rider weight not being pushed to the limits of course 

I agree though, I personally opt for steel as I'm not a weight weeny, and durability and repairability are important factors in my choices, and I'm no feather weight either.


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## Drzdave58 (28 Jan 2020)

I have had many aluminum and steel frame bikes...I much prefer how my steel frame bikes ride...way more comfortable imo...


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## Smudge (28 Jan 2020)

In aluminium framed bikes and steel framed bikes, both can fail if they are poor quality. I just dont buy that reasonable quality alu framed bikes will break easily, many alu bikes have been around for a long time. I've never had one one break on me, or fracture at the welds yet and i'm not exactly a lightweight rider.


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## FrankCrank (29 Jan 2020)

Back on hols in Koh Chang, where my folder snapped in two. This time with my trusty R20, a '77 vintage, and wouldn't be surprised if it kept going for another few decades.........


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## the_mikey (29 Jan 2020)

Smudge said:


> What makes you think its a rebadged Dahon ?
> I've never seen a Dahon with a frame like that, or a Tern come to that. I know Tern had a spate of their folders breaking at the main hinge, but this was after they parted from Dahon.



I owned a Tern from 2011 that was subject to a recall, (2013) the weld on the hinge part was suspected and I had the frame replaced free of charge as part of the recall.


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## Smudge (29 Jan 2020)

the_mikey said:


> I owned a Tern from 2011 that was subject to a recall, (2013) the weld on the hinge part was suspected and I had the frame replaced free of charge as part of the recall.



Good that they did a recall. I guess they didn't want to be stuck with the reputation of frames breaking. Although i expect it cost them a lot of sales around that time.
Have you still got the folder ?


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## the_mikey (29 Jan 2020)

Smudge said:


> Good that they did a recall. I guess they didn't want to be stuck with the reputation of frames breaking. Although i expect it cost them a lot of sales around that time.
> Have you still got the folder ?



I don't have it, but I know the person who uses it now and it's still going well, I replaced the jockey wheels, cassette and tyres for the current owner a few months ago!


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## Kell (2 Feb 2020)

Smudge said:


> In aluminium framed bikes and steel framed bikes, both can fail if they are poor quality. I just dont buy that reasonable quality alu framed bikes will break easily, many alu bikes have been around for a long time. I've never had one one break on me, or fracture at the welds yet and i'm not exactly a lightweight rider.



Not sure how you judge ‘quality’. If it’s just down to price then, at £900 each, the Dahons should have been better.

My first folding bike was a second- hand one I bought on eBay for £200. Aluminium, designed by the guy who designed the folding hinge for Dahon, and lasted well. Didn’t crack - even when I got knocked off and it got a little bit squished.

That was a Rabbit.de bike.


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## Smudge (2 Feb 2020)

Kell said:


> Not sure how you judge ‘quality’. If it’s just down to price then, at £900 each, the Dahons should have been better.
> 
> My first folding bike was a second- hand one I bought on eBay for £200. Aluminium, designed by the guy who designed the folding hinge for Dahon, and lasted well. Didn’t crack - even when I got knocked off and it got a little bit squished.
> 
> ...



But this thread isn't about Dahons and Dahon dont have a reputation for breaking. It was Tern that had a spate of bad frames and they did a recall after that episode.


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## Kell (2 Feb 2020)

Pretty sure the OP stated he believed it was a rebadged Dahon.

I also didn’t claim anything other than I wouldn’t have another aluminium framed bike. As 66% of the ones I did have have cracked. And both of those were Dahons. 

What I was asking is what you believe a ‘quality’ aluminium bike to be.

Where do you draw a line and say that one is and one isn’t? That’s all I was asking.

As far as I was aware at the time, when mine cracked, Dahon was in the process of suing Tern. Certainly Joshua Hon had already started Tern, and David Hon was in proceedings with them. Info was sketchy at the time and the UK distributor had stopped importing, so despite having two bikes - each worth £900 new, and both with lifetime frame warranties - I was left with no help.

As an aside, it’s also the reason I don’t use Evans any more as they left me high and dry. I had my receipt, my contract was with them, they should have sorted it. 

But I’m not bitter. 

Like for like, Terns weren’t wildly different in pricing to Dahons, so I’m stuggling to work out how anyone would know what constitutes quality.


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## Smudge (2 Feb 2020)

Kell said:


> Pretty sure the OP stated he believed it was a rebadged Dahon.
> 
> I also didn’t claim anything other than I wouldn’t have another aluminium framed bike. As 66% of the ones I did have have cracked. And both of those were Dahons.
> 
> ...



OP's bike doesn't look anything like a Dahon, they haven't ever produced a frame like that. Its a no name folder, the like of which can be bought cheaply at many places.
Its these no name bikes that i wouldn't have any faith in and i certainly wouldn't spend my money on.


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## ukoldschool (3 Feb 2020)

but you would buy a Dahon, despite the fact they are known to crack....


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## roadrash (3 Feb 2020)

FrankCrank said:


> View attachment 502419
> 
> Back on hols in Koh Chang, where my folder snapped in two. This time with my trusty R20, a '77 vintage, and wouldn't be surprised if it kept going for another few decades.........




I like the added v brakes  must be ten times better than original brakes..


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## Smudge (3 Feb 2020)

ukoldschool said:


> but you would buy a Dahon, despite the fact they are known to crack....



Its simply not true that Dahons have a reputation for frames breaking. Some may have, but also Brompton frames have been known to break, and no one would say they have a rep for it.


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## FrankCrank (4 Feb 2020)

roadrash said:


> I like the added v brakes  must be ten times better than original brakes..


Yeah, original brakes are ......... erm ........ not for the faint hearted. 
I'm a fan of V-brakes, simple and effective when set up right. As I've got a TIG welding box it was a no-brainer really. 
On my next one, I'll try and keep the original fork and add bosses to it, max tyre size though will be 1.75" for front. 
Anyways, they're cracking (not literally of course) little bikes, and as oft been said, they ride just like a full size bike........


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## roadrash (4 Feb 2020)

yeah I like twentys ive had one or two


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## ukoldschool (4 Feb 2020)

Smudge said:


> Its simply not true that Dahons have a reputation for frames breaking. Some may have, but also Brompton frames have been known to break, and no one would say they have a rep for it.



There you go again misquoting, you seem to make a habit of this. 

I didnt say they had a reputation for cracking, I said they are known to crack. Kell has had 2 Dahon fames and both cracked.



ukoldschool said:


> but you would buy a Dahon, despite the fact they are known to crack....



I appreciate you are clearly a Dahon fanboy, but please read what people wrote instead of what you think they wrote.


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## Smudge (4 Feb 2020)

ukoldschool said:


> There you go again misquoting, you seem to make a habit of this.
> 
> I didnt say they had a reputation for cracking, I said they are known to crack. Kell has had 2 Dahon fames and both cracked.
> 
> ...



I'm not a fanboy of Dahon at all. I only entered this thread because i questioned why the op stated his folder was a rebadged Dahon. Yet it then transpired he just assumed it was. Then people come on talking about Dahon frames breaking like they have a rep for it, which they dont.
I was putting the record straight against generalised views.


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## icowden (4 Feb 2020)

Similarly Tern Frames are okay, it just the hinge that tends to crack and break (the closure bar, so it remains structurally sound).

I have had a Dahon frame break while riding, but that was because Evans decided that a tern bike could be fixed by replacing the frame with a Dahon Frame and didn't notice key details such as the seatpost being a different length - and not long enough to reach past the safety point of the seat socket. Luckliy I only sustained minor injuries and after a brief discussion about legal action got my shiny new Tern Joe P27 as a replacement.


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## mitchibob (13 Feb 2020)

Smudge said:


> Plus steel framed folders like Brompton aren't exempt to breaking, incidences of that can be found.



True, but seriously impressed with only getting a very slight frame bend and still ridable bike after hitting car side-on at 20mph, where my right hand, left wrist, and helmet, didn't come off quite as a well.


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