The rear end of the bike started to get... wobbly. With each pedal stroke the rear would flop back-and-forth. I took the bike off the road to ensure it would not get worse. This post is about Dahon Jetstream suspension pivot maintenance. I'm going to say that again three times, because when I searched the Internet for
any information on this topic, there was nothing. So here goes:
Dahon Jetstream suspension pivot maintenance!
Dahon Jetstream suspension pivot maintenance!
Dahon Jetstream suspension pivot maintenance!
OK, Google bot... come find me!
So at first I tried to just casually remove the pivot by removing its retaining bolt - a coarse threaded 8mm bolt with a hex cap - and coaxing out the pivot pieces (two pieces). See the pic below, the suspension pivot is centered, the frame is to the left and the rear triangle to the right. The bottom bracket is seen, crankless, to the lower left:
It would not budge. I decided rather than escalate my efforts slowly I'd just go right to max effort - so I took the
entire bike apart! This way the frame would be lighter and less junk would be in the way. This turned out to be
a very good decision because It let me find another unknown problem...
With the bike on the stand and stripped of all parts, it was not hard to get the pivot out. Sure, I had a few false starts, including the (likely unnecessary) use of a blow torch to heat the pivot up/expand it...
So let me show you what these parts look like:
Here they are extracted and cleaned up. They were a fair bit dirtier prior to this pic. You can see 1/2 of the pivot is "male" and the other is "female" - see next pic for more on that...
The two halves of the pivot mate together, and the 8mm bolt threads into the male half: Also shown, some stainless steel 0.2mm thick, 20mm ID x 28mm OD shims.
Prior to this teardown, I could wiggle the rear triangle back & forth and I'd see the suspension pivot heads moving relative to the front of the bike frame. But after removing and cleaning them, when I bolted them back in tight they basically locked to the frame as one solid piece. Sure, I don't have the leverage of the rear triangle as a moment-arm, but these are definitely seated right and are likely ready to go...
Oh yeah - forgot to say how I got those parts out. Well I bought an 80mm long bolt with matching thread pattern, hand-tightened it into the male half of the pivot coming in through the female side, and tapped its hex head firmly with a hammer to drive the male half out of the bike frame:
Once that half was out, I placed a deep socket that was ever so slightly narrower than the pivot into the now vacent right side of the pivot, and hammered that until the female half came out.
Here's a look at the front half of the frame: Look carefully you might see the aluminum is warn a bit from when the pivot came loose
Here's the rear triangle. Notice the brass bearing insert. The bubbled paint is probably from when I used the blow torch, unfortunately.
What next? Well, I had to put Humpty-Dumpty back together again. I put new thereadlock blue on the retaining bolt, and grease on the suspension pivot outer diameter. I held the rear triangle in place, hand-inserted the suspension pivot (then drove it lightly with rubber mallet - tight fit!), then hand-tightened the retaining bolt into place. Note the male half of the pivot has a hex shape molded into it so you can keep it from turning when you tighten the retaining bolt
Oh and remember those shims - seen blurry in the background above? Their inner diameter is
perfect for the suspension pivot halves, but about 1mm larger in diameter than the lip on the outside of the suspension pivot halves. This is almost a best case scenario. To help mitigate the aluminum wearing off the front half of the frame where the pivot seats, I placed one shim on each side of the pivot assembly essentially as washers. Then as I tightened the two halves of the pivot until the retaining bolt bottomed, the stainless steel sort of curved up and alongside the flanges of the pivot halves. Think of a bearing race pressed into a shaft housing. The entire assembly fits together nice and firm and the rear triangle pivots without any sideways slop.
Mission Accomplished
As a post-text - I mentioned early on that disassembling the bike led me to find another latent problem. I'll talk about that in another post, but it all boils down to the fact that shock eyelets come in both 12mm and 0.5" sizes...
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