SR Suntour RUX RC2 PCS Fork

Review by Evan Turpen // Photos by Dave Trumpore

It's no secret that the long-travel bike market is a tough one to crack into. The numbers of product produced is much smaller than other areas of the market and the performance and quality demanded is of the highest level, because it has to be. As a result of the highly competitive market, many companies and products have come and gone, and some companies won't even dabble in it for fear of never getting a return on their investment.

SR Suntour isn’t one of these scared companies, and for 2014 they’ve made the leap into the long-travel downhill and freeride market with the release of their air sprung, 200mm travel RUX fork. Retailing at $1,200 fully-loaded with many features and adjustments, is this the fork that will successfully get SR Suntour into the big bike market?

Our first test of this fork showed it to have a lot of promise, but it was held back by overly harsh damping and stickiness off the top. Suntour took the RUX back to the shop and came back with a longer negative spring assembly and a softer compression spring, changes that Suntour says are now featured on the production version (late model year 2015). When it comes to suspension, it's often these seemingly small changes that can have a big impact on performance, so we were more than eager to throw the RUX back onto the big bike for a second go-around. Our findings are in the updated review below.

RUX Fork Highlights

• Air sprung
• 200mm travel
• 38mm stanchions
• Tool-free 20mm axle
• Direct post mount for 203mm disc rotors
• 26-inch wheel compatibility
• Externally adjustable high speed compression (13 clicks), low-speed compression (9 clicks), rebound (14 clicks), and air pressure
• Internally adjustable air volume spacers (6 positions) to adjust progression
• Available with black or white lower legs
• Weight: 2,921g (6.44-pounds) test fork with cut steerer
• MSRP $1,200

Installation and Setup

The RUX has a few unique features that make installation and setup a little different than other downhill forks I’ve used in the past.

First up is the tool free 20mm axle system. Hidden within the axle is a retractable red lever for turning/tightening the axle. At first it was difficult to remove the red lever from the axle, but once it was out, a couple drops of lube had it moving in and out smoothly for the rest of this test. Once tightened down, the axle is clamped in place by a large quick release lever on the drive side of the lower legs. This is in place of a tooled pinch bolt system, saving some time and hassle.

The disc brake mount is a 203mm post type only, requiring your caliper and two bolts to hold everything aligned and properly spaced for a 203mm rotor. My Shimano ZEE brake caliper bolted up perfectly aligned with the 203mm front Shimano rotor, and I have to say it's nice to not have to use any adapters here. The vast majority of downhill riders are running a 200/203mm rotor, so this doesn't present an issue.

The 38mm stanchions also come with height markings for clamping the lower crown at the correct height, showing the safe usable range with “max” and “min” clearly defined. There is 10mm of height adjustment available and I set mine to the maximum height setting (most “choppered out”) to most closely replicate my previous FOX 40 axle-to-crown settings. Once the fork was installed, I set the air pressure to a ballpark setting by feel as well as rebound and compression and went out for a bit of a parking lot test.

Inside the fork, below the air spring top cap, up to five spacers can be used to reduce air volume in the spring and create a progressive ramp-up as you near the end of its travel. The fork was provided to me with four of the five spacers installed. This setting felt a bit too progressive for my tastes and I eventually settled on only one of the spacers installed combined with 64psi in the air spring, which is approximately 8psi over the recommended starting point for a rider of my 170-pound weight.

On The Trail

Updated Ride Impressions:

After reviewing the SR Suntour RUX fork earlier this year, I honestly could not wait to put back on a tried and true coil-sprung downhill fork. Soon after swapping out forks on my DH bike, Suntour asked for the RUX back so they could install some of the improvements and tweaks that they had been working on. Curious to see what would improve, the fork was boxed and shipped to the Madison, Wisconsin service center.

A few weeks passed and the RUX returned with the upgrades installed. Suntour said they had installed an improved longer negative spring assembly and a lighter high-speed compression spring. I was hesitant at first to believe these could magically turn this fork around, but I had to test it. I had to see if they had truly improved it. I set the air pressure, stanchion height, rebound, and compression all to the exact same settings as my finalized settings from the previous test [see below]. After doing so I had a brief parking lot test and I could instantly tell that a lot had changed... and it felt for the better.

The fork felt much more forgiving on its compression damping circuit and the air spring was an entirely different beast. I actually had to crank in the compression settings (both high and low-speed) quite a bit from the old settings until the fork had what I thought to be a desired feel. This was a big departure from the almost fully open settings on the old fork.

Once on the trail the improvements to the fork were immediately noticeable. VERY noticeable. So much so that I was smiling from ear to ear at the bottom of my first downhill run. Suntour had gotten it right. The updates created a fork that I truly enjoyed riding. It was supple yet supportive and had a very predictable feel to the air spring that was very much coil-like, but honestly felt a touch better. I used almost all the travel with a tiny bit still in reserve from its perfect feeling progression. It was light, tracked well, and was a joy to ride.

With these updates done, Suntour has created something that now seemingly performs with the best of the best, yet the reasonable $1,200 retail price makes the RUX that much more desirable.SR Suntour says these changes will make it to production, which means the new kid on the block will give the big names a run for their money. It’s that good. I'd gladly race with it mounted to the front of my bike, and I'm one picky dude. They just need to make a 650b version...

The revised RUX as ridden in this second test has received a 4.5/5 star rating, placing it among the best performing forks in this category.

Notes from SR Suntour:

"Consumers who have purchased or plan on purchasing a RUX have the option to custom tune their fork with alternative spring set ups to match their riding style and feel (pricing will be affordable but will vary depending on what changes and level of service are requested). For information contact SR Suntour’s Madison, Wisconsin service center who are happy to help get you set up properly."

Three changes have been made or will soon be made to production forks:

• Bleed ports on the lower case starting on forks produced starting 02/19/2014 (Serial # TE00171951 and later)
• Longer negative spring on forks produced starting 2/27/2014 (Serial # TE00208591 and later)
• Softer compression spring starting the next production run

The compression spring (late model year 2015), lowers and longer negative spring are parts that the service center has in stock.

Original Ride Impressions:

The things I most look for in a good downhill fork are chassis stiffness/precision, adjustability, and above all else suspension performance. Weight is less of a concern of mine, although a light fork is obviously more desirable.

First and foremost, once on the trail the chassis stiffness and feel is very good. The large 38mm stanchions provide precise steering and braking at all times with no noticeable flex. There is also tons of mud clearance around the tire and fork arch (20mm at the closest point between my 2.5-inch Maxxis Minion DHF and the fork lowers). No complaints here!

The RC2 damper is highly adjustable through its external adjusters, but I found myself having to run minimal amounts of high-speed compression, low-speed compression, and rebound to get the fork feeling at its best. I usually run much firmer spring and compression settings than your average Joe so this worries me a bit. Beyond air pressure there’s not much else that can be done to soften the fork for riders preferring softer settings.

Medium to big hits are absorbed in a controlled, no-nonsense fashion by the RUX. The air spring with one air volume reducer installed provided a nice ramp up near the end of travel. I never once felt the fork bottom out hard so in hindsight I could have probably gotten away with even less progression by removing the last spacer. I'm of the opinion that using most of the available travel on your fork once/twice per run is a good thing, otherwise why have it? With fewer spacers installed, however, support under hard braking leaves some to be desired. Unfortunately when I tried to dial in more low-speed compression to combat brake dive the RUX would become too harsh at higher speed square edged hits as well as small bumps. It also felt as if the fork became a bit harsh while trying to rebound from multiple hits in succession at high speeds. This was even with an almost fully fast rebound setting.

The air spring itself has a decidedly “air” feeling to it - stiff off the top, wallowy in the mid-stroke, and rampy towards the end. It uses a positive air chamber and a simple inline dual coil negative spring. Compared to other systems on the market it is extremely simple, but unfortunately not very effective at making the fork supple at the top of its travel.

My final settings after two months of riding and tuning are listed below:

• Air pressure: 64 psi
• Air volume spacers: 1 installed
• High-speed compression: 10 out
• Low-speed compression: 7 out
• Rebound: 11 out

Things That Could Be Improved

Air Spring: Throughout the entire test I was wishing for a much suppler feeling off the top of the stroke and more support in the mid-stroke. This could be accomplished with a redesign and tuning of the negative spring assembly. Shipping the RUX with multiple negative spring setups for tuning to different air pressures could be a good way to go too. Honestly though, I would have without a doubt much rather seen the RUX as a coil version that hit a slightly lower price-point, albeit at a slight weight gain. Suspension performance is key on long-travel bikes and a coil spring would improve the feel and performance of this fork drastically, especially given the good chassis feel. UPDATE: The revised version of the RUX that we re-tested provides an entirely different level of performance from the airspring, addressing all the points raised here. See our updated ride impressions above for full details.

Bleed Valves: There are none. Pressure builds in the fork lowers from going up in elevation or an increase in temperature. Sliding a super thin ziptie down between the stanchion and seal releases built up pressure in the fork lowers and improves the performance. It would be nice to see a button activated bleed like what comes on the new X-Fusion and FOX downhill forks. UPDATE: as of late model year 2015, the RUX will ship with bleed valves on the lowers.

RC2 Damper: The compression adjustment range needs to be shifted to the softer side. Like I found with the SR Suntour Auron fork that I tested previously, the RUX could benefit from increased low to mid-speed compression with drastically less high-speed compression. I felt it could benefit from more support with less harshness when things get really fast and rough. The rebound also should be tuned to have less deep stroke rebound to make the fork better respond to successive hits. This could be accomplished by redesigning the rebound valve to flow more oil and adding a shim element that could control this flow further depending upon the forces applied to it. UPDATE: the revised compression assembly addressed our concerns here, with the updated fork providing a supple yet supportive ride.

Long Term Durability

Everything about this fork looks, feels, and functions in a way that inspires long-term confidence, except for the air spring. Part way through the test the fork became extremely stiff off the top and a handful to ride. It turned out that the air piston had a bad seal and was allowing quite a bit of air to leak past and pressurize the lower leg. SR Suntour sent out a replacement air piston and seal assembly which we installed, bringing the fork back to its originally designed performance. Luckily the fork is extremely easy to service and maintain. With routine maintenance of the air spring, seals, and lubrication, this fork should be able to run strong for many years to come. Suntour has a helpful series of tech videos to help walk you through servicing your fork should you be up for a little DIY action.

What's The Bottom Line?

UPDATED:The RUX chassis is great, it's easily serviceable, competitive in the weight game, and offers a lot of the features found on much more expensive forks at a fraction of the price. With the updates introduced to the late model year 2015 version, the performance is now also right up there with the best. At this price point, the RUX will be a handful as far as competition is concerned, and we no longer have any qualms about running this fork as the primary fork on our DH bikes.

For additional info, visit www.srsuntour-cycling.com.

About The Reviewer

Evan Turpen has been racing mountain bikes for over 12 years. He raced downhill as a Pro for the last 8 years with his career highlight being selected to represent the U.S. in the 2006 World Championships. More recently he can be found competing in enduro races and having a blast with it. He is an aggressive yet smooth rider who loves to flick the bike around to put it on the fastest line or to smooth out the rough sections. Fast flowy trails and long technical descents (Garbanzo style) are his favorite. With an extensive knowledge of the mountain bike industry and its technologies, Evan is able to take all things in to perspective during a review. He has helped design, develop, and test products for multiple major mountain bike companies and has an attention to detail well above most. When he's not out ripping around on a bike he helps run the recently introduced California Enduro Series and is also in charge of the bike park at China Peak Mountain Resort.