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  1. #1
    Metal
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    RS Recon 351 U-Turn vs Preload, Pop-lock vs Compression

    I recently got a 2006 Rock Shox Recon 351 Coil U-Turn fork. It has the U-Turn coil with travel adjustment on one side and a pop-lock adjust with remote on the other side.

    In the manual I see that there is more than one diagram on the page. The other diagram shows a preload adjuster where my U-Turn adjuster is, and a compression adjuster where my pop-lock thing is.

    So my questions are:

    1. By having the U-Turn spring am I giving up my ability to adjust my preload (at a given travel height)?

    2. By having the pop-lock, and I giving up all of my range of motion control adjustment?

    Thanks
    Straight is better than flat.

  2. #2
    Singletracker
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    2. Yes. Poplock is either "on / off" with no range to adjust your motion control. Most people only ever use it with on / off so its not a big deal. You can replace the motion control damper (very easy replacement), by getting a non-remote one for probalby under $80.

    I look forward to the day when they will bring out a remote compression adjuster that allows the full range of the motion control including lockout. Would be very useful.

  3. #3
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    You can use PopLoc Adjust or (better) a friction shifter lever to adjust the compression on intermediate levels between minimum compression and lockout.

  4. #4
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    I installed a Tora 318 U-Turn on a friend's bike-came with the pop-loc but no lever (!) so we bought a $10 friction shifter at the LBS and he is able to use it for full-range compression adjustment. When the RS pop-loc lever arrived, we looked it over and came to the conclusion the friction shifter was a better option and left it on!

    The Recon 351 U-Turn does not have preload adjustment (at least mine doesn't), which is why I think the spring rate ranges listed are narrow: 140-160 lb was my stock spring. My Z-2 springs are rated at 140-180 lb range, but it has adjustable preload. I'm at the lower range of the weight scale (145#) and briefly contemplated installing the lighter spring, as the new fork felt quite stiff compared to my Z-2 Atom. However, this forum convinced me to leave it alone, and I can now state it works great when riding and I don't miss the lack of adjustable preload at all. You should note that cranking the U-Turn down to 85 mm does appear to increase the spring rate (per the manual), but given the reduced amount of available travel this makes some sense to me.

  5. #5
    Metal
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    So I hit a medium-sized drop (about 3ft) and my forks bottomed out. I am about 205 lbs, so I am thinking I better get a stiffer spring. I got the fork used and I am not sure what's in there now, but I assume it is stock (M?). I think the extra-firm would be appropriate for my weight, but I will be running it at less than full extension (100-110mm, out of 135mm total), so I wonder if Firm is more appropriate. I'll probably go with XF.

    I am still a bit mystified about what being able to adjust through the range of my Motion Control will really do for me. I read about it being a way to adjust to prevent brake dive and the like. I am wondering if the XF spring will alleviate the need to replace my simple pop-lock with something that allows a range of settings.

    Maybe I am out to lunch.
    Straight is better than flat.

  6. #6
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    Seems to me if you are bottoming out on a 3 ft drop with a trail fork, you aren't doing too bad. General rule of thumb is you should bottom out a couple of times on your tougher rides, as this means you are taking full advantage of all your travel. If more than this, you may need a higher spring rate. Using a zip tie or O-ring around one of the stanchions to assess how much travel (and sag) you are using can also be helpful.

    Another problem could be low oil level in the damper leg, which affects your compression damping/lock-out. The way this fork is designed, a leak in either of 2 O-rings at the bottom of the right stanchion leg allows your damping oil to leak into the lower leg casting, eventually leading to loss of compression dampening and then hydrolocked fork.Does the fork lock out if you manually hold the MoCo adjust all the way clockwise and compress the fork? It should have a very small amount of movement under this condition at most.

    Your fork SHOULD already have the good Motion Control damper. You DO have access to its full range of compression adjustment if you either use the generic friction shifter approach, or buy the Pop-loc Adjust lever. As it stands right now, with a pop-loc and no bar lever, you have no compression damping other than the default wide open setting and can't use the lockout because of the spring loaded lever either (the spring on my friend's Tora was not obviously removable).

    Given the age of your fork, I would take this fork apart and examine the spring color code on the left to see what it it set up for now, and given its age I would replace the O-rings with the appropriate service kit and refill the oil levels to stock. I would get the generic friction shifter and install it. Only then would I think you can accurately assess what you need spring-wise.

    Fork is very easy to service with the on-line RS manuals and a few basic tools: most exotic are 24 mm socket and internal C-clip pliers. Some 5wt fork fluid and 15W motor oil and an $18 service kit and you are done.

  7. #7
    Metal
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    Thanks. I will try the cable tie thing.

    The fork does have a working pop-lock remote, and when I engage it the fork stays locked out, and has that bit of expected movement.

    The fork seems to be in good working shape, but I know it's better to make sure, especially with used stuff.

    I had planned to break the fork down and service it when I got it, but decided to ride it first and get a baseline of performance. That way I would be able to make better decisions like spring firmness and MoCo adjust options.

    I think I will take your advice and service the fork, determine which spring I have, add a MoCo adjust of some sort, and ride some more.

    The fork is definitely not causing problems. First ride I had a little trouble hitting some small jumps. Just felt unstable in the air. Half way through that ride I adjusted the travel from 100mm to about 107mm just to try it. It seemed alright. Then I took it out again and rode it at 107mm the whole time, including on the jumps. Either I am just getting used to it, or the increased travel helped, because my air time was way more stable that ride.

    Thanks
    Straight is better than flat.

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