berlinonaut

Which seems a bit funny, considering that SRAM publicly announced that they would stop producing geared hubs in spring this year... What Dahon says about this:

Source: Folding Bikes by DAHON DAHON CURL - Answers to FAQs ? Folding Bikes by DAHON

Which translates to: We have no idea which hub we can use in future and we don't care anyway. Regarding the after-purchase service and spare parts of SRAM people needing this for a SRAM Dualdrive hub probably have a clear opinion about the quality of this "service" based on their experiences. And this was while the hubs were still in production...

gataddhin

I am aware of that but I am concerned about the current Curl i8 being fitted with Shimano Nexus 8 spd hub at Shenzen factory now and due to be exported next month.

berlinonaut

This was 20 years ago (in 1997) and a test of 12 lightweight racing bike frames of the top price segment. I would expect that things may be a bit different today as well as in the folding world but what they found out was basically: For endurance of the frame it does not matter too much what material you are using but which attention to detail you have during construction as well as during manufacturing as most breakages in the tests seem to have resulted from misconstruction. This should be easier to avoid today as with today's computing power stress simulations are cheap, easy and common. The more embarising is the problem with the Tern frames.


The video shows machinery that is necessary for the mandatory tests (DIN, ISO, etc.) to be able to sell bikes in most western and some eastern markets. Nothing to praise Dahon for, just a unavailable commodity for any bike manufacturer.

Well, the actual German Brompton manual states 110 kg for the Brompton, the European Dahon homepage states 105 kg for the Curl, the American (Dahon global) homepage does not list the the Curl ( ), only ThorUSA states 130kg (for the 35years jubilee model) as does the Kickstarter Campaign for the Curl 3i. This is exactly the chaos and lack of reliable information that Dahon is famous for. I.e., just as ONE other example, the dahon-eu-page states the curl would have 18" rims while in reality it has proven to have 349 wheels, commonly called 16".

tds101 

As much as I'd like to believe the curl frame, with it's higher weight limit, would be an exception, I highly doubt it would be superior to the Brompton's steel frame. As someone else was so kind to point out, aluminum isn't as tough as steel.

Bonzo Banana

A quick search shows that EFBE frame tested is not highly regarded because the stresses are far too high with the frame's failing far too quickly. If you reduce the load you allow steel to work to it's endurance limit which would make it cope better with a far higher number of load cycles than other materials and be more akin to normal use. Testing frames to destruction does not represent real world use and comparing a steel frame that is attempting to be light weight and competitive with other materials may not represent a typical steel frame designed for strength and long life. If you are designing a performance low weight frame you are not normally using steel.

I think there is some confusion in your analysis because my view why aluminium is weaker long term is not just the material and the fact aluminium is more difficult to weld but the design approach to the frame. There is a design philosophy on creating performance bikes which in the complete absence of aluminium would be steel and again would still be weaker than bikes designed for strength and long term use also using steel. It just so happens because of material properties that bikes are most commonly divided by frame material between performance and standard bicycles.

I do think the endurance limit of steel is a big factor though. Keep within the endurance limit and the frame isn't damaged and straying just outside the endurance limit doesn't fatigue the frame as much. An aluminium frame always gets weaker with use but steel can endure more as long as the loads don't approach very high levels. Mountain bikes which take huge abuse are rarely made of steel nowadays as such excessive loads (drops, jumps etc) would give steel no advantage its only when the endurance limit comes into play can steel show a long term advantage which would be typical of a road bike. Only for that type of use can steel really excel in lifespan.

When you look at typical 20" folding bikes, you often get aluminium models around 12-13kg but a similar steel folding bike would be 15kg or more. That's a 2kg difference, I would suggest that increase in weight is not just the frame material difference but actually going for a stronger design with less regard for final weight.

Maybe your manual says otherwise but on this page Dahon states the Curl only has a weight limit of 105kg. 5kg less than the Brompton. So the Brompton is still the stronger bike for rider weight.

DAHON Curl i3 16" - DAHON

foldingdroid

Maybe in the future, just maybe, Dahon will produce some limited anniversary models of Curl made of steel or titanium. And of course with the provision for front carrier blocks and other refinements.

gataddhin

And Curl made of carbon fiber like Korean's Chedech folding bikes.

tds101 

I highly doubt that dahon will make an effort to go affordable, as the demand is growing, and the price as well. I truly hope the quality rises to meet the cost.

As for carbon fiber,... Who knows.