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Old 01-30-08, 08:01 AM   #1
sguikema
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Problem with Dahon Speed D7 front latch?

I purchased a new Dahon Speed D7 a couple of weeks ago. Within the first two weeks the little plastic sleeve inside the latching mechanism that holds the handlebar stem to the frame cracked and broke. In its current state, the handlebars will not latch. Has anyone else had this problem with their Dahon folder? If so, did you come up with a solution besides buying another of the suspect plastic pieces? I was briefly impressed with my Dahon, but this seems like a fairly fundamental design problem - a small plastic piece under stress being the weak link in the usability of the bike. Any suggestions for fixes would be welcome.
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Old 01-30-08, 09:17 AM   #2
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I am a proud owner of a '06 Speed D7 and have not had any problem except one time flat. How about using zipties for now perhaps an easy solution until you get to order that plastic latching piece.

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Old 01-30-08, 10:02 AM   #3
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I have a D7 and there is no plastic piece that keeps the stem in place. There is a metal QR that secures the stem in the unfolded position. If you are talking about the plastic safety clip all it does is add an extra level of security to the metal QR - it should not be under any stress at all when riding. I would ride my D7 without it and as noted above you can make a temporary fix with a zip tie.

I do think Dahon should make that piece out of a non-brittle type of plastic. It would save everyone a lot of hassle.
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Old 01-30-08, 10:12 AM   #4
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I have a D7 and there is no plastic piece that keeps the stem in place. There is a metal QR that secures the stem in the unfolded position. If you are talking about the plastic safety clip all it does is add an extra level of security to the metal QR - it should not be under any stress at all when riding. I would ride my D7 without it and as noted above you can make a temporary fix with a zip tie.

I do think Dahon should make that piece out of a non-brittle type of plastic. It would save everyone a lot of hassle.
He's talking about the delrin piece located inside the handlebar post, at the base of the post. It is a known problem that this delrin block can work loose rendering a handlebar post which is unable to latch. Zip ties will not work. As far as I'm concerned, it IS a design flaw, and the biggest reason to own one of their 26" folders instead. You should ask Jur about this design. He has a lot to say. Here's a pic by BruceMetras:

white delrin block





In squikema's pic, notice he's missing the block:
no block

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Old 01-30-08, 10:14 AM   #5
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He's talking about the delrin piece located inside the handlebar post, at the base of the post. It is a known problem that this delrin block can work loose rendering a handlebar post which is unable to latch. Zip ties will not work. As far as I'm concerned, it IS a design flaw, and the biggest reason to own one of their 26" folders instead. You should ask Jur about this design. He has a lot to say. Here's a pic by BruceMetras:


white delrin block
Ahhhh...SNAP...thanks for the pic!...
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Old 01-30-08, 01:47 PM   #6
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Yes, that's the piece

Yes, that's the piece. Here's a picture of my broken derlin piece.

At least Dahon did reply to the e-mail message today (I sent it yesterday) and offered to ship me a replacement plastic piece. We'll see how long this one lasts. They are responsive to e-mail queries. Now if they would just put a phone number for such service requests on their web page...
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Old 01-30-08, 01:49 PM   #7
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it's a slip cover

Sorry for a second post. I meant to say that the derlin piece is actually a slip cover over a metal block, at least in my D7. It's not solid. I guess this is evident if you look closely at the pictures I posted though.
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Old 01-30-08, 02:55 PM   #8
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I meant to say that the derlin piece is actually a slip cover over a metal block, at least in my D7. It's not solid...
Interesting info. Thanks for clarifying.

When you get your delrin cover, I've read that people are using blue loctite to keep tension on that piece, as well as to keep the screw in place as a result of vibration, etc. You should contact Thor (thorusa.com) to see if he has other suggestions, but I think he said he's at a boat expo now. The other option is to check the Dahon forums if you haven't already done so.
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Old 01-30-08, 03:33 PM   #9
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Extensive description on how to improve the latch safety and operation coming up...
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Old 01-30-08, 04:29 PM   #10
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I recommend you dismantle the whole lot, clean it, and reassemble. I hope you can tinker?

1. Unscrew the 2 button-head cap screws that hold the sliding latch in place. There are 2 springs that push the latch by pushing against the button-head screws. Remove the latch but take great care not to lose the 2 little springs. Clean the latch surfaces as well as the surface against which it slides.

2. Unscrew the bolt that adjusts the delrin-covered block and clean the threads.

3. Unscrew the 2 grub screws that hold the springs in place and clean the threads. Apply a medium grade Loctite thread locker (preferably blue Loctite) and replace the grub screws. Ensure they are just below the surface.

4. Apply blue Loctite to the block adjuster bolt and screw it back in with the new block in place.

5a. Apply Loctite to the button-head screws and screw them down, all the way but not very tight, taking great care that the 2 little springs are properly in place. This is very fiddly.

5b. Now carefully unscrew the buttonhead screws a small amount until the latch plate can slide freely. Make very sure the buttonhead screws cannot turn freely after the Loctite has set. Make very sure the latch plate does not bind on one of the buttonhead screws which would cause it to misalign and break the delrin. make very sure the buttonhead screws are not unscrewed more than they have to - this will give the latch plate too much slop.

6. After making very very sure that the screws cannot turn freely (under vibration they will unscrew if they can) and that the latch plate can slide freely without binding, and that the springs push the plate symmetrically, adjust the bolt for correct latch lever tension when closing the handlepost hinge.

So in summary, there are 5 separate screws that all need Loctite and all need to be adjusted perfectly for the latch to work properly. It is important that you understand how the latch works so that you can assemble and adjust it perfectly, your life may depend on it.

It is known in the forums that I find the latch design a scandalous piece of work, but if working properly it should be OK. But even then I won't trust it 100% as there is no fail-safe backup mechanism.

Last edited by jur; 01-30-08 at 04:39 PM.
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Old 01-30-08, 04:51 PM   #11
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Excellent. Thank you! You should post this on a public page that something like Google or Yahoo will find easily too! You'd think Dahon would do something to improve this design. It's clearly a recurrent problem. I appreciate the help, and I'll work on the latch system.
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Old 01-30-08, 06:17 PM   #12
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It is important that you understand how the latch works so that you can assemble and adjust it perfectly, your life may depend on it.

It is known in the forums that I find the latch design a scandalous piece of work, but if working properly it should be OK. But even then I won't trust it 100% as there is no fail-safe backup mechanism.
I am playing devil's advocate here. Is it really that big a deal if the latch comes loose? The stem can still transfer load through the hinge and as long as you always ride with two hands firmly on the handlebars, it should not be a problem? Have there been any known injuries from such mechanisms coming loose?
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Old 01-30-08, 06:39 PM   #13
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Is it really that big a deal if the latch comes loose?
Speeding down a hill, out of the saddle, leaning on the handlebars and the latch comes loose? Yes, I would say it really would be a big deal.
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Old 01-30-08, 06:53 PM   #14
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I am playing devil's advocate here. Is it really that big a deal if the latch comes loose? The stem can still transfer load through the hinge and as long as you always ride with two hands firmly on the handlebars, it should not be a problem? Have there been any known injuries from such mechanisms coming loose?
Here is a thread where the latch was loose and due to the force transmitted through the hinge only, broke clean off. The rider was lucky it happened after he got off the bike moments before.

There is the pic of the failure in the thread. Note the misaligned sliding latch plate.
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Old 01-30-08, 06:55 PM   #15
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Speeding down a hill, out of the saddle, leaning on the handlebars and the latch comes loose? Yes, I would say it really would be a big deal.
WHy would one be off the saddle, seems like asking for trouble?
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Old 01-30-08, 07:31 PM   #16
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WHy would one be off the saddle, seems like asking for trouble?
Sometimes it's uncomfortable having all that vibration/road buzz constantly hitting your @ss while coasting down a hill, especially on ratty roads. But in general, on folding bikes, yeah, you're not out of the saddle much.
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Old 01-30-08, 09:12 PM   #17
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Sometimes it's uncomfortable having all that vibration/road buzz constantly hitting your @ss while coasting down a hill, especially on ratty roads.
Strongly suggest a Thudbuster - it is so comfortable on my Boardwalk S1 that I ordered them on our new Bike Fridays. Really a lot more comfortable to stay in the saddle except for the extreme bumps, which even Cane Creek recommends you raise up on. Wife likes it, too.
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Old 01-30-08, 09:29 PM   #18
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I am playing devil's advocate here. Is it really that big a deal if the latch comes loose? The stem can still transfer load through the hinge and as long as you always ride with two hands firmly on the handlebars, it should not be a problem? Have there been any known injuries from such mechanisms coming loose?
I would respectfully disagree. It could be a big problem. Have you tried to ride a Dahon with the handlebars not latched firmly in place? I have, but not by choice. See the thread above - my plastic chock block cover broke while I was riding this morning - not a complete separation of the handlebars but the handlebars where only weakly attached. At best, it isn't much fun. At worst, it's a recipe for a bad crash, even if you're sitting on the seat and peddling along at a relaxed clip. It's hard to maintain balance when your handlebars unexpectedly give way, at least it is for me anyway. I plan to fix my latch before I ride my Dahon again. It would be even better if a fail-safe latching mechanism (or at least one unlikely to fail to start with) could be designed for these bikes.
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Old 01-30-08, 09:48 PM   #19
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Strongly suggest a Thudbuster - it is so comfortable on my Boardwalk S1 that I ordered them on our new Bike Fridays. Really a lot more comfortable to stay in the saddle except for the extreme bumps, which even Cane Creek recommends you raise up on. Wife likes it, too.
Lookin' good, FT. But I really don't mind standing once in a while, even on a folder.
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Old 01-30-08, 10:36 PM   #20
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Lookin' good, FT. But I really don't mind standing once in a while, even on a folder.
I do stand for entering driveways, unavoidable potholes, etc., but we also have some very bad pavement here in Vancouver, USA - some rather new pavement that is disintegrating, as well as some old roads (like Evergreen Highway) that have 3 layers of pavement in various states of disarray. My 65 yr old backside is a lot more comfortable not having to absorb it all directly.
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