Fox Float CTD/RP23

SSD Modification and HSB Adjustment System

Does the performance of the SSD exceed that of the DHX air and are you more satisfied with the end result?

The RP23 is a very poor performance shock with the boost valve, this SSD modification improves the square edged performance greatly, the DHX air is still a better SSD modification because of its better compression circuit that we install. The propedal lever is used in conjunction with the 123 settings to achieve the settings made to the internal changes, the trail or Propedal-off position is the 4th setting. Currently these mods are aimed at the Boost valve versions of the CTD and RP23.

How does it compare/what are your thoughts on the SSD Float X vs the DBair?

For sure the Float X with our high/low adjuster will be the best performing air shock out there!

Can’t say that any of the Fox shocks are better than each other as they are each in a different class, as we have improved the weakness of each model. The DB air has its benefits but is also limited to the external adjuster oil flow, and for higher shaft speeds and lower leverage systems it seems to fall short of the advertised capability.

If so, do the stock adjustments remain or do you install your adjustment knobs?

We modify the internals with our HSB adjustment system and the external stock lever adjusts this system.

With the Float service, is the air can volume still adjustable with spacers or is that no longer necessary because of your internal workings and the external hsc adjustment?

The Float still has adjustable spacers and available air can changes to adjust the volume which changes the spring rate, these are always separate from the damper adjustments.

When do you expect to have parts for the SSD service on the basic CTD?

The SSD service is available now, they are basically the same inside and the levers adjust everything a bit differently

How is the rebound handled in the SSD damper?

The high and midspeed rebound is adjusted by the shim stack internally and is based on the pressure used in the air can. The stock high speed rebound is very firm and Fox relies on the user turning the low speed out to compensate(one or two valving schemes fits all approach). This can make the midspeed rebound seem too fast and the low speed compression seem to soft(oil flows in both directions through the rebound needle). We valve the rebound shims to the air spring rate and try to aim the low speed rebound to the smaller orifice size 4-8 out so it affects the low speed rebound fine tuning only and the low speed compression bleed is a known amount within this range.

Does the SSD mod in those and it's ability to blow off during repeated hits eliminate the spiking that plagues them?

Removal of the Boost valve will solve the compression spike in the position sensitive Float. The CTD shock is essentially the same as the RP23, they reversed the lever system and added the trail position for fine tuning. As for the boost valve removal and replacement with a shim stack, this will be the same for both shocks the difference is how we handle the adjustment of the compression

The volume spacers allow us to tune the progression so that's covered. I think you told me once before that the Push big hit kit/bottom out bumper was a gimmick, but I can't remember the details of your explanation. Is this the case?

It will help the low leverage set-up that use less initial pressure or (you can’t get a smaller can and the largest spacer is installed and you are still using a low pressure), because the air does not ramp up as much in these set-ups the bumper could add a bit more force at the end. For the higher pressures the bumper will be negligible as the air pressure creates much more force. We could add one if this is the case.

Also, how does the RP23/CTD chassis handle heat and fade? I assume it's much less capable than the Float X, but I figured I'd ask as I might be interested in having both shocks tuned.

With proper valving and good oil, the damper fade will not be noticeable as compared to the air spring ramp-up created by the heat. Either way this is really not a big concern for a frequently serviced and a good functioning shock.

This is kind of random, but I have to ask someone in the suspension industry. It seems as though consumers have become so picky lately about their suspensions. Shocks are coming out with more user end adjustments and the aftermarket tuners such as you are doing really well. Obviously, there's a benefit to be obtained and I'm one of those picky riders. Sure, I can go out and ride all of the same stuff on my Float CTD that I can on my DBair, but I feel like I have less control by way of rebound, compression, bottom out, etc.. and have to find a setup that provides the best compromise for all scenarios. However, when I was surfing the internet the other day and looking at all of the pro's rides from the Enduro World Series, I noticed very few of them ran the DBair, but an enormous number of them ran the RP23/CTD, Monarch Plus, X-Fusion O2, etc... So, after all my rambling, here is my question for you... Are these racers running off the shelf stock shocks or are they being tuned for the individual riders weight, bikes, setup, etc...? I'm sure these guys could ride on anything as their skill is exceptional, but I just have to know. If riders like myself can feel the differences and improved performance of the higher end products, how do these pros get along with those same basic shocks? I remember you telling me about Gwin testing out the new Fox shock last year that utilized the smaller shaft instead of the RC4's thick one so I know some of them are testing prototypes, etc... But, the pics of these small stock shocks on the race scene has me perplexed.

Not sure, I would say most of them ride what is given to them, and that would be stock. Most tuners really can’t make the shock perform much better than stock unless they go all out and make allot of new parts like we do. I think things like CTD are a crutch for companies like Fox, it is better to give 95% of the riders 3 choices than infinite ways to mess it up with the high/low adjusters. Less complaints from the masses means more money for them.

Your site describes the RP23 lever. Can you tell me what each setting does on your modified CTD? Climb (firm), Trail (3 lsc settings), and Descend (full open on lsc or minimal lsc)?

Basically the lever pushes on a rod inside the shaft, each position puts the rod closer to the end of the shaft where we use a tapered plug to resist the flow of oil through the shaft center, thus creating compression adjustment. Our system uses an assortment of different spring rates spring that allows the plug to blow-off under higher shaft speeds, creating a high speed threshold valving adjustment (HSB). This allows high speed adjustment as well as a low speed platform feel. The open or descend position is a lighter low speed setting with less preload on the high speed blow-off, the Trail increases the preload in smaller fine tuning increments and the Climb or “on” position adds the maximum low speed and preload with very little blow-off float, creating a more usable lock-out mode.

HSC set internally?

The compression shims on the piston valve control the low to mid speed transition as well as the high speed valving.

The rebound shims on the piston valve control the low to mid speed transition as well as the high speed valving.

Volume spacers, I can only use one with my current can size. Do I need to have the volume spacers already figured out or can I do that after you modify the shock? I don't know if your valving takes those into consideration or not?

Based on the leverage and the rate (regressive, linear and progressive) we will recommend the best option for spacer and can size. This figures into the rebound and compression valving curves.

Do you install an aftermarket piston like the high flow one that Push installs?

The stock piston is correctly sized for most damping curves, it just needs to have the boost valve system removed and a more speed sensitive valving stack installed instead. If more flow is required we modify the ports as needed, i.e. drill them slightly larger, too much flow requires too many valving shims and creates a high speed valving lock-out issue .

I did note that the climb setting is no longer very stiff and I couldn't really tell any difference between it and trail. The shock kind of felt like the different settings were very subtle between them. I'm not a suspension guru so may be this is how Craig intended for it to be.

Thanks for the feedback! Hopefully this will help describe our approach to the Float SSD/HSB conversion. We felt the climb and descend positions are not very useful on the stock CTD. The Climb was too firm and harsh to ride on any terrain and the descend was too soft and blew though the stroke. Our goal was to create an adjustment system that was more geared towards DH rather than pedaling. The middle trail 2 position would be the standard setting that provided adequate pedaling performance with a plush small bump feel, not blow through the stroke like the descend position did and improve the high speed square edged action. The threshold adjustment system would create a firmer position in the climb position, softer position in the descend position with the trail position having 3 finer tuning DH/Enduro positions. So yes, the SSD/HSB creates a few more usable adjustment positions as compared to the stock CTD but the differences are more subtle, but useful between them.

I bought a Knolly Endorphin in September, and about two months after general trail riding, started to develop a "clacking" noise. After some research, it seems it is the rear shock making the noise, and not the bike or hardware itself. I have a few questions about the process.
1.) Will your upgrade/service remove the "clacking" noise?
2.) Can I expect to hear the noise come back after service?
3.) Do you have a warranty to cover it in the event it does come back?

This shock relies on a high pressure IFP to maintain the clamping force of the boost valve. The clanking noise is caused by the air bleeding by the shaft and IFP seals leaking the overheated ifp charge into the damper oil, this creates an air gap in the damping oil and causes the clank. Due to the higher IFP pressure in the boost valve, this stock set-up tends to leak by faster, and if the shock overheats this increases the pressure. All this means is the oil does not last very long before it causes the damper to fail.

Removing the boost valve and replacing it with the speed sensitive damper shim stacks allows for lower IFP pressures, reduced oil wear, no hydraulic lock(oil being forced to extrude the seals) and lower internal operating temperatures. We also use a higher temperature IFP o-ring and a better shaft seal for cold temperatures. This helps extend the oil life and reduces air contamination, but it should be known all air shocks, no mater which brand are subject to this issue over time.

We would expect the service interval to be 60 hours of hard riding, same service life as fox expects in the service manual.

My shock has developed a squishing sound at the top of the stroke. It has only been about 40 hours since the last service.

This noise is an indication that the oil has become compromised, it is an inherent problem with all air shocks, the air can air will migrate past the damper shaft seal over time even if the shock is not ridden. Some shocks have more of an issue then others, and there is really no way to tell, could be the model, how old it is, how much wear and tear on the parts, condition, factory tolerances, starting air pressure(over 185 psi), too large of voulme spacer required or just slowly migrating over 50-100 hrs of riding. It slowly will happen and at some point it will be noticeable. We do warranty our work for set-up and ride performance, but there is really no way to tell if there is going to be a limited life of the oil. We replace all the seals during our modifications with higher quality ones than Fox provides to help with this issue, but this does not always guarantee long term success, we did not design the shock we are just modifying it.
In your case we feel that we have done our part, but keep in mind this is a 4 year old shock that most likely fits one or more of the potential issues we mentioned that the shock might have, so it will most likely require maintenance a bit more often than other shocks. BTW Fox has updated there maintenance schedule to 50-100 hrs or when ever an issue occurs. Rockshox recommends every 50 hrs. Keep in mind these are very tiny little shocks with only 1-2 oz of oil and extremely over stressed.

I don't need much LSC with the VPP to help with pedaling, but have been running the shock now in Trail 1 mode. This has helped with the bottoming by keeping the bike/shock higher in its travel. Actually it has help a fair amount, but has compromised the compliance/plushness of the shock.

I think if there was a "Trail 0.5" that would be a compromise I could live with. That is why I've thought about a CCDB, so that I could dial it "right in".

Spoke to Fox about it a few times. Not much help there.

This is the typical compliant we get about the Float CTD, descend is too soft and trail takes away the plushness. Our removal of the boost valve and SSD/HSB conversion fixes the issue, you will be able to run it in T2 and have the ramp-up through the middle and be plusher initially. You will be able to adjust to T3 or T1 to make the shock a bit firmer or softer. Climb and descend are are useful settings now but are a step firmer and softer that the whole T1-3 range. This conversion works because we are able to remove the threshold boost valve and replace it with a custom tuned shim stack tailored to the leverage and riding that you do.

I see that you offer a upgrades for the Float CTD, DHX Air and Float-X though the upgrades performed for each shock seem quite different. So I'm unsure how the different shocks would compare in performance after the upgrades.

Basically the differences are in the compression adjustability and oil volume. The performance is similar, but each gets a bit better compression adjustment as you go up in price, ctd, dhx air and then the float x, this is because the oil can be metered and adjusted a bit better than the lesser model. The ctd has a HSB low speed adjuster, the dhx air has a shimmed high speed with low speed adjustment, more clicks if you can find a knob version, and the float x gets our high/low speed adjuster. As for fade the ctd in stock form is over damped and causes the shock to overheat prematurely. The piggyback shocks will dissipate heat more quickly and have about 30% more oil.


I decided to Avy the CTD on my 13 Endorphin. After a few rides I can say that I am happy with the improvements Craig made to the shock. I asked for the standard tune and it feels great with the Endorphins suspension curve. The biggest improvement is in the mid range support.

I can actually use the descend mode now due to the added support. Prior to the Avy tune it was hard to predict what was happening at the back of the bike in descend. I have also noticed better control for jumping in both descend and trail modes. Jumping now feels controlled and is almost as good as the Chilcotin/Woodie set up.

The only place I did not see improvement was on high speed chatter. From what I understand, the Endorphin's suspension curve was not designed to be soft like the Chilcotin and that is the price you pay for performance in other areas.

Climb mode is less stiff and I will probably just use the trail and descend modes for simplicity. I did notice better traction at the rear wheel on steep climbs. With the stock CTD and DBair, I never seemed to have the rear tire traction that I expected. Again, technical climbing now rivals the Chilcotin/Woodie set up. (with exception of the low bb on the Endo)

Craig was not able to predict if his mods will improve reliability of the Fox CTD. However, he did say with the boost valve gone, it should be better. Looking forward to another season on the Endorphin. As a bigger rider I did not think this shock would ever work for me, I was wrong.

Float X a worthy upgrade on a Bronson?

Another option might be getting a DHX air for cheap and sending it to Avalanche Suspension for Craig's full custom tune and speed sensitive damper mod. It'll definitely be setup for your riding style and the bike. I have the Avalanche fork cartridge and had my CTD Evo shock revalved (cheaper Evo can't accept the ssd damper) on my Bronson and such a huge difference to the handling and small and big hits. After having custom setup suspension I don't think I could ever go back to an off the shelf shock.