JD 929 rear shock upgrade set up & result

Discussion in '5th Generation 1998-2001' started by OZ VFR, Apr 18, 2014.

  1. OZ VFR

    OZ VFR Member

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    I got a JD 929 shock a couple of weeks ago, & have been playing around with it trying to set it up.

    I replaced the front springs with Racetech .95 a while ago, & replaced the oil with 5 weight and 10mm extra oil level. I also raised the forks on the triple clamps 6mm, it felt much better then the too soft standard set up, & thought I would leave the damping rods for a while as I liked it as it was.

    The standard rear shock was too soft, & damping adjustment did very little.
    I weigh 75kg, and often ride with my wife who is also 75kg (65 according to her, but our scales have a memory function). I would set the spring preload to max when we did, & to the third position when solo.
    I thought it wasn't too bad, but mid corner bumps would upset it & it felt every bump on the road.
    It would also do a wallow when hitting dips mid corner & was never confidence inspiring.
    After I removed it I realised it was bottoming out, as the rubber stop was demolished.

    When I ordered the new shock from JD, I told him I wanted it set up for 70% solo, 20% two up! & 10% two up with lots of luggage. I also mentioned I didn't mind it a bit stiff.

    After installing the new shock, which wasn't that hard, I went for a quick ride.
    First impression was that he had installed a way too stiff spring. I thought, what has he given me? I was getting bounced of the seat & felt every tiny bump.
    I looked up spring rate tables & read all I could find on bike suspension trying to figure it out.

    Went for a 100k ride a few days later thinking it was a matter of getting used to it.
    No way, it was so hard a ride that it wasn't enjoyable or safe.

    So I sat & thought about it for a while.
    I'm not very good at setting up suspension because I can't tell why it's doing what it's doing.
    Realising this I went about it in a more scientific way to see if it was JD or me.

    I first got a mate to help me, he held the bike for me while I pushed down on the seat as hard as I could. I noticed that it was going down no problem, but was taking around a full second to come back up. So I backed off the rebound damping half a turn, not much difference. Turned It one full turn and it was better. At one and a half turns it was coming back only a bit slower then it was going down.
    I set this as a starting point for the rebound damping (the bottom screw).

    I then placed the bike on the centre stand and measured the rear wheel position (top of axle to square trim under mudguard) it was sitting 20mm lower then standard shock (raised rear).
    I then again employed my mate while I measured static sag (wheel position with bike on ground but no rider).
    I found this was only 5mm. I thought it was not enough but had read that the slow speed compression damping can have an affect on this (I think this is the only thing that the top screw adjusts, if I'm wrong feel free to correct me).
    So I backed it off one full turn, now static sag was 10mm, I set this as a starting point.
    I then got my mate to help me again to measure sag with rider in position, sitting on seat with both feet on the pegs.
    At the lowest spring setting it was 30mm, perfectly where I thought it should be.

    Today I went on a 140km ride on my favourite road, what a difference, the bike now no longer feels little bumps and surface irregularities, it stays on line on both hard bumps and dips, it is totally confidence inspiring & predictable.
    I still get a little wallow when I do an aggressive change of direction on a fast s bend (120km/h), but nothing like before. I will do some fine tuning to iron this out, if anybody can point me in the right direction, it will make things easier.
    If anything, it has shown me how bad the original shock was, & now shows the short comings of the front damping, as soon as I can squirrel away some dosh, I'll be getting it sorted.

    Sorry JD, for all the names I called you after my first ride, it is bloody perfect.

    I installed the shock with the reservoir facing front of bike, thinking that when I had more time, I would trim the under tray and turn the shock around, but I don't think I'll bother.
    I can use a long skinny screw driver between the heat shield and frame to adjust the compression damping, and from bellow for the rebound damping, all while on the side stand which makes it easier.

    If your contemplating replacing the rear shock, I can totally recommend this option.
    I'm sure an Ohlins or such would even be better, but I don't think it will come close in bang for buck value.

    I still have fine tuning to do (sadly, I went on the ride today to adjust shock, but forgot my long skinny screwdriver at home, this is what you get when you try & multitask (ride a great road on a sunny day and adjust something)), but I now have a smile on my face.
     
  2. OOTV

    OOTV Insider

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    I had a similar experience with my 6 Gen shock JD rebuilt, but I knew I had to "tune it" before it would give me what I was looking for and like your experience, all it took was a few "adjustments" and now it's just what I was expecting! I also had JD send me the shims and springs for my forks that I could install but I had not put those in at the same time I installed the rear shock and I was even more impressed once I did. Having a "balanced" front/rear suspension really made a tremendous difference. Even if you had bought an Ohlins, you'd have to go through the same procedure, but as you said, the JD 929 shock is a great back for the buck investment!

    Cheers!
     

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