Friday, June 10, 2016

2012 Fox Float 29 FIT CTD damper upgrade

In 2013 I upgrades bikes from a five year old Giant Trance XO with 26" wheels, that I built from the frame up with a Fox Talas RLC (adjustable 100/120/140mm travel), to a state-of-the-art 29er: a 2014 Santa Cruz Tallboy 2 Carbon. The sum of many small--and big--technology improvements in the Tallboy took my riding to a whole new level of fun.

Once the honeymoon period ended and I understood the Tallboy's personality, I began to question the performance of the Fox suspension components. The bike came specced with Fox Float CTD front and rear, with a sweet Kashima-coated version of the FIT CTD fork and a less-sweet, non-Kashima shock under the seat. Both components were a clear improvement over the RLC and RP23 on the Trance: they responded better to bumps, were easier to adjust, felt plusher and, in the case of the fork, were noticeably stiffer and lighter--not least because of the thru-axle design.

But I found it hard to get the fork feeling totally dialed. It was either too firm and bounced off small obstacles like roots, or too squishy and prone to diving. I could get it feeling good, but not great, no matter what settings I tried.

Some online discussions revealed similar complaints with the 2012 and earlier models. And it turns out my fork is a 2012 model--which certainly explained its performance. This was a surprise because I'd bought my bike in the summer of 2013 as a just-released 2014 model (no discount there!) and I reasonably expected a 2013 fork.

The good news is that the problems were tied to the damper design and Fox introduced an improved damper in the 2013 model. All reports indicated that the new damper performed really well, solving the damping problems of the 2012 and earlier CTD models. Even better, since the fork body remained the same, the 2013 damper can be installed into the 2012 fork. Fox even offers an upgrade path on their website. If you're in the US, you can deal directly with Fox. In Canada, you need to arrange the upgrade through your local Fox dealer/bike shop, who will send it to Outdoor Gear Canada for the swap. It's not cheap (I think I paid around CAD$250 for the upgrade, and OGC kept my old damper) and it's best done at the same time as a fork service (e.g. seal replacement).

This is what the adjustments on the new damper look like (apologies for the poor focus).

The red rebound knob now has a very satisfying click.

Is it worth it?

Yes! I immediately noticed a significant performance improvement in the form of better tracking and control over stutter bumps and roots. This is where tight damping control is absolutely essential to keep the front wheel planted on the trail so it can do its job of traction, braking and steering. With the old damper, I was never really able to eliminate the tendency for my wheel to either bounce off small obstacles or just pack up, no matter how much I played with compression and rebound damping. Cornering on rough ground felt sketchy, especially at high speed. With the new damper, the fork just sucks up roots and square-edge hits, keeping the rubber planted. This is especially noticeable on off-camber turns where traction is critical. Now I'm able to ride significantly faster while maintaining control.

Here's how I set up my suspension:
  1. Set tire pressure. I weigh about 195-200 pounds ready to ride, without water in my pack. I'm running Schwalbe Hans Dampf tires (29"), tubeless, on 19mm rims. Most of my riding is on hard pack and/or mud with exposed limestone and granite, sharp baby heads and rock gardens, and lots of roots. When it's wet, it's very slippery. I tend to ride 22 psi front and rear, but may air down to 20 psi if wet. 22 psi gives my tire enough lateral stability that it doesn't squirm, but isn't so hard the suspension can't compensate or traction suffers. At 20 psi I find the rear wheel tracks less predictably through rocks and roots. I've also run other tires but the Schwalbes seem to give the best overall performance for my conditions.
  2. Set sag. This is really important: your suspension needs to be able to travel down as well as up so it can track into depressions and maintain traction. I aim for 25% compression when fully kitted and sitting on my bike. For my rear shock this means about 160 psi although for me that still feels hard, but any lower and I get too much pedal strike. For my fork, 75 psi is about right. Focus on the actual sag, not the numbers, because your pump gauge is small and hardly accurate, and temperature and elevation can affect results. Another way to gauge pressure is to see if you've used your full suspension travel after a hard ride. No? Then your pressures are too high and you're wasting available travel. If you find you're bottoming out on moderate obstacles where you shouldn't, then air up. Make adjustments in 5 lb increments. 
  3. To start, set rebound and compression damping in the middle of the range. The goal is to find the sweet spot so that when your wheel hits small obstacles like roots, the wheel doesn't bounce up and off the root but rather tracks right over it and plants back on the ground. I run my compression damping a click or two above the middle setting, and rebound damping a click below middle setting. This slows the sudden diving action my fork makes when hitting square edges (because I'm heavy), but allows the fork to return a little quicker so it doesn't pack up.  It may not be scientific but it really works well for me.
  4. Ride and adjust. Are you still bouncing up off square edges? Turn down compression damping. Do you feel a little "kick" when coming off the top of a root? Turn up rebound damping. Make one-click changes and ride the same section to feel the difference. Try riding fast over roots and other stutter bumps, and rough or loose off-camber corners to get a good feel for your settings. Then write them down! 
This upgrade has breathed worthwhile performance into my shock, extending its useful lifetime and making riding more fun for much less cost than upgrading the whole fork or bike. Now it's time to address the shock. The Float CTD only has adjustments for sag (air pressure) and compression damping. Despite having its damper serviced at the same time as my fork, it still feels harsh over small bumps and bottoms out easily if I lower the pressure. Running it in the "open" setting (the only mode where your compression settings take effect) helps somewhat, but is not efficient for pedaling. I'll be looking into an alternative shock, perhaps a Fox X2, to see if performance can be improved. It's interesting to see how prices on my CTD shock have plummeted to as low as $80 new. It's not worth servicing again, and I would get better value by upgrading.

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