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  1. #1
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    2013 Fox CTD Kashima w/ Trail Adjust setup questions

    Gurus, I need your input. I bought a new bike, Santa Cruz Tallboy LTc with a Fox Float CTD Trail Adjust rear shock. I set up the air pressure via the shock chart on Santa Cruz's website. For the past month, I've felt like the shock was using too much travel for the terrain I've been riding on. I increased the pressure +20 psi over what is recommended for my weight, and that helped a little. Adjusting the Trail Adjust setting to 3 also helped, but I still felt like it could be better, ie use less travel.

    I read about the Fox volume spacers and thought I'd give them a try to see if increasing the compression ratio of the shock would help. I though it prudent to check and see if there was one installed in the shock and in fact there was already a spacer in there. Slightly disappointed thinking I'd need to send the shock to get pushed to increase the compression damping, I reinstalled the air can and set the air pressure back to the SC recommended, placed the bike on the ground and found the rear shock to be absolutely solid! No movement at all with me on the saddle. Then I remembered that I needed to set the shock to descend mode and rebound all the way in in order to set the sag correctly. So I deflated the shock all the way, set the lever to descend and compression knob all the way in. Pumped halfway to my recommended pressure, checked function, all was good. I increased pressure back to recommended, checked operation, all was normal. I set the lever to trail, and returned compression to where I had been running it for the past month. I took the bike around the block, speed bumps, curbs, & stairs and noticed that the rear shock behaved much better. It wasn't using a ton of travel like it had for the past month, in fact I really didn't have a complaint about how much travel it used at all.

    So, here is where I need your input. What changed when I loosened the air can (note I only removed it slightly to peek inside the shock cap to see if there was a spacer, It never slid all the way off the shaft, shock was installed in the frame the entire time). Did I reset the negative spring? Why did the shock become fully rigid after re-pressurizing with the lever in trail mode? Admittedly this is my first air sprung bike (both front and rear), so setting this up is new to me. I tried researching how the shock functions but there isn't a lot of technical information published by Fox. Any help in understanding what I did right/wrong would be greatly appreciated, thanks in advance!

  2. #2
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    I had the same concerns, I just came up on the pressure. Seams to have helped. And yeah, fox is very short on putting info out there.

  3. #3
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    No clue what caused your shock to completely lockout...the Fox CTD w/TA doesn't have a true lockout, but the important thing is your shock seems to be working now.

    I just finished dialing in my CTD Trail Adjust shock on my Turner 5.Spot and mine also came with a large volume spacer. The spacer (Fox makes five unique sizes for the CTD) is designed to modify the PROGESSIVENESS of the shock's compression. Effectively, the spacer helps the shock "ramp up" as the shaft is compressed. It makes it increasingly more difficult to use incremental travel. My guess is SC spec'd the Fox CTD with that spacer to complement your bike's suspension design and curve.

    Since it's your first FS bike, I'll say that, if it were me, I'd first start with SC's recommended SAG setting (not PSI based on weight). Their sag % is driven by a lot of things but getting it right will help you/the bike acheive the proper feel on the trail (and yes, that goes beyond your expectation of how much travel you THINK the shock should or shouldn't be using).

    As for compression damping, Fox really designed the Trail and Climb modes to offer added low-speed compression damping (to help with pedaling, etc.). Climb Mode does not equal Lockout. PUSH could only help, but it sounds you really need to dial in your initial set-up. LBS should help with that.

    Good luck

  4. #4
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    Quote Originally Posted by trojan08 View Post
    No clue what caused your shock to completely lockout...the Fox CTD w/TA doesn't have a true lockout, but the important thing is your shock seems to be working now.

    I just finished dialing in my CTD Trail Adjust shock on my Turner 5.Spot and mine also came with a large volume spacer. The spacer (Fox makes five unique sizes for the CTD) is designed to modify the PROGESSIVENESS of the shock's compression. Effectively, the spacer helps the shock "ramp up" as the shaft is compressed. It makes it increasingly more difficult to use incremental travel. My guess is SC spec'd the Fox CTD with that spacer to complement your bike's suspension design and curve.

    Since it's your first FS bike, I'll say that, if it were me, I'd first start with SC's recommended SAG setting (not PSI based on weight). Their sag % is driven by a lot of things but getting it right will help you/the bike acheive the proper feel on the trail (and yes, that goes beyond your expectation of how much travel you THINK the shock should or shouldn't be using).

    As for compression damping, Fox really designed the Trail and Climb modes to offer added low-speed compression damping (to help with pedaling, etc.). Climb Mode does not equal Lockout. PUSH could only help, but it sounds you really need to dial in your initial set-up. LBS should help with that.

    Good luck
    Thanks for the reply and tips. You're statement "sag % is driven by a lot of things but getting it right will help you/the bike achieve the proper feel on the trail (and yes, that goes beyond your expectation of how much travel you THINK the shock should or shouldn't be using)" got me thinking, maybe my expectation about how the bike reacts is wrong. I'll play with my base setup some more this weekend. I'll start with the % sag, as you recommended, I'm curious how that will change how the bike acts. Through it all, I'm shocked at how much better/faster I'm riding with this new bike. The engineering that these bikes have behind them is quite impressive!
    Last edited by whoodie; 02-22-2013 at 05:05 AM.

  5. #5
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    Sounds good. I checked SC's website and they're recommending 12-15mm of sag. So convert that to inches, grab a tape measure and begin the process. Most people would say to flip the CTD lever to Descend (least amount of compression damping) and open the Rebound to full fast BEFORE you set/measure sag. Less sag (12mm) will give you a firmer/racier feel; more sag will have you sitting a little deeper into the travel and will feel more active and sensitive to small bumps. After reading a few reviews on your bike, it's evident that most agree the Tallboy LT's sag has to be spot on. So spend some time getting it right and "set and forget"!

    Then you move onto rebound...great Pinkbike article here. To The Point - Rebound Damping - Pinkbike

  6. #6
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    I don't get why you don't want to use the majority of your travel. I have that bike and shock and on a ride where I don't leave the ground, I used 85-90% of the travel. If I do jumps and drops of a few feet, I used 95-99% of the travel. Air shocks are progressive. It's pretty easy to get the first 75% of travel, and the VPP link is designed for that type of use. You have a Tallboy LT. Use the LT.
    I'm 145-150 pounds and run the shock 5 psi below the recommended setting for x-country days, and right at the recommended psi for bigger hitting rides and I leave at on the trail setting all the time except for putting it in climb if I'm riding pavement to and from the trail.

  7. #7
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    Whoodie and colleagues: I wonder whether you may have discovered more facts about this issue. I am having a lot of trouble with my new Fox CTD (remote). See my post: new Fox CTD rear shock bottoming out at 300 psi!. I would be extremely grateful for any help!

  8. #8
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    Quote Originally Posted by adriano View Post
    Whoodie and colleagues: I wonder whether you may have discovered more facts about this issue. I am having a lot of trouble with my new Fox CTD (remote). See my post: new Fox CTD rear shock bottoming out at 300 psi!. I would be extremely grateful for any help!
    Read your thread, sounds like you need to send it in for service. Definitely not normal behavior.

  9. #9
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    no worries, I am monitoring my thread! I was waiting with feedback until I spoke with the Swiss Fox guys. I am still flummoxed at why the shock would bottom out at high pressure though. Sag should be dependent only on (1) pressure, (2) leverage, and (3) weight - hence even if all the innards are broken, if the pressure is high and does not dissipate, it shoudn't be affected?

  10. #10
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    I stand corrected (by myself). Sag is actually good - as expected from the physics of it. Bottoming out appears instead to indicate excessively "loose" travel, which may well point to internal issues.

  11. #11
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    Quote Originally Posted by trojan08 View Post
    Sounds good. I checked SC's website and they're recommending 12-15mm of sag. So convert that to inches, grab a tape measure and begin the process. Most people would say to flip the CTD lever to Descend (least amount of compression damping) and open the Rebound to full fast BEFORE you set/measure sag. Less sag (12mm) will give you a firmer/racier feel; more sag will have you sitting a little deeper into the travel and will feel more active and sensitive to small bumps. After reading a few reviews on your bike, it's evident that most agree the Tallboy LT's sag has to be spot on. So spend some time getting it right and "set and forget"!

    Then you move onto rebound...great Pinkbike article here. To The Point - Rebound Damping - Pinkbike

    I'm very interested in this comment about setting the sag at the Descend mode and rebound fast. I have done this a few times and compared it to climb and there is a big difference. Sag is so essential to the best performance of the shock and fork and there is no one (as in FOX) willing to say this is how it is done. I put the question out there, on another thread and no responses. So yes I'm very interested in finding out more about this. Tks

  12. #12
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    Well I got an official reply from FOX, quite surprised.

    "When setting sag you will always want your suspension in the most open compression setting possible to isolate just the air spring. On this shock this would be the [CTD]descend position."

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