Is a broken frame the end of life for a Dahon Mu P8
 

Hello,

Sadly, the frame of my Mu P8 developed cracks in the hinge area. Basically, some aluminum pieces of the frame body fell. It is not the steel piece of the hinge itself (for which I could have hoped for a replacement part), but rather the frame extensions that are kept together by the hinge.

A bit of background. The bicycle has more than 18000 km mileage, used extensively in the last 4 years for urban commuting. There is a long list of parts that wore and had to be replaced:
- 2 cranksets and 3 pairs of pedals
- 2 handleposts (one was officially recalled but it broke while used)
- 1 fork (that is because I fell once on the bicycle)
- 1 bottom bracket
- 1 chain and 1 cassette
- 1 rear wheel rim (break wear) and 1 spoke

In terms of accidents, I had just about 3 where I fell of the bicycle in the early months of getting used to it. And only one last year when the fork was broken because I fell on the handlepost/bar. The main reason of the frame failure I suspect is the stress caused by urban riding. I'm not using streets (too crowded) but sidewalks. I was reasonable (that is my valuation) with how I negotiated the curbs. I slowly climbed small ones (like up to 5-6 cm) and slowly put the front wheel first then almost at zero speed fell with the rear wheel from slightly larger ones (up to 7-8 cm). Anyway, the sidewalks are of poorer quality than the roads, often with holes and various shock creating obstacles.

The Mu P8 is claimed to be the sturdiest of the Dahon models. But if the normal urban riding is enough to put it to sleep, then perhaps I should look for a fixed frame bicycle, not folding.

Okay, with these data, what do you think? Have you ever heard of replacing the entire frame of one Dahon (a 2007 model)? Do you consider this mileage the "normal expected lifetime" of a folding bicycle? For the record, if I would have known that I should not ride small curbs with Dahon, I would not have bought one.

Thanks,
Chris

Pictures would help, but it does sound like you migjt have been ill served by this bike. The thing about AL frames is that if you take them into the plastic zone (above yield stress) they get fatigue stress cracks at lower mileage then they would have otherwise. An accident that breaks a fork would do it.

Thank you for reply. Here is a picture. Two things can be seen. One is a missing "tooth" at the top right that would be pushed by the hinge against the other side of the frame (see the shiny aluminum). The second is the broken loop of the hinge (center of the image) which is the one at the bottom in real life. That is why I said that it might be stress due to curbs: when the weight of the rider falls few cm from the sidewalk on the rear wheel (I used high pressure, low profile, low width 1.5-1.65" tyres), the tension goes in the bottom loop of the hinge that is keeping the frame from breaking in two.
http://bikeforums.net/attachment.php...hmentid=397196

18000 km hard urban riding ...Hmmm ? Now this talk about alloy again... wow ...
Ok ... lets get to the actual problem ...
Where are you located ? In the US I am pretty sure I can help ... outside USA so far so good... mostly I am successfull but there are freight charges etc etc which makes it complicated.

Depending on your weight, riding style, depending on the care you give to the bike, the way you do the actual folding .... meaning you make sure that the clasp is not swiveled and grabs the "ear" in lack of better words on the corner and puts undues pressure on the on of the ears versus slide easily behind both ears ... when you tighten the lever. Depending on that the folding mechanism is nice and clean and lubed, adjusted properly ...
and and and ...
Especially if this is a bike I sold, ( but not limited to that of course ) I would at least try to get some kind of replacement frame from Dahon.
Now.... I did not necessary said free, or warranty. I would try ... of course, but sometimes its not that easy.

18000 km is a good clip. but there are plenty of alloy Dahons out there with more km ( or miles )

That sounds like some good service you got from the bike!

Thank you for commenting (you are famous on the Dahon website and I tried once to buy a 20" rim from you but Evans Cycles won because it is in the UK and I'm closer in the continental Europe - you were the only two suppliers I could find). I will search the forum for the alloy debate. There is an internal struggle in my mind now about my future bicycle ... whether it should be from steel or not ... my brain associates AL 6061 to my broken Mu P8.


You are right that I was an aggressive rider and not going for a leisurely pace, but NEVER jumping. Only 28+ road bikes with slim tires went faster on their road.
Actually, I felt something on the Sunday I took it for a four hours ride at the end of which I discovered the issue. At unfolding, I met some unusual resistance from the lever. I do care for my bicycle without overdoing it though, and I did not force the lever. Instead I pushed it back to the fully open position, flexed the frame (i.e. open it) and restarted the unfolding by closing the frame (i.e. lining it) and pushing again the lever to lock the frame. This time it worked (I mean as usual, like in many thousands of unfoldings I did) and I never looked back. At the end of the ride I encountered difficulties opening the hinge, some creaks that I NEVER HEARD from my hinge in my life, and I saw the disaster inside after opening the hinge. Usually my hinge worked pushed by one finger (but opposing some resistance towards the end of the movement at closing) but this time it was very difficult to open it.

Thank you for advice. My Dahon is "built by hand in EU" and I heard a lot of skepticism from Dahon personnel about the supply chain in Europe. I waited a lot for my replacement fork that I think it was adapted from another model and not from Mu P8. But I will send some inquiries.