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SR Suntour RUX Fork

Vital Rating: (Good)
SR Suntour RUX Fork SR Suntour RUX Fork - Black
C70_screen_shot_2013_12_31_at_7.28.37_am C70_sr_suntour_rux_fork C70_sr_suntour_rux_fork C70_sr_suntour_rux_fork C70_sr_suntour_rux_fork
Vital MTB Retail Partners:
Chain Reaction Bicycles Jenson U.S.A. Competitive Cyclist Backcountry

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Vital Review

“Tested: SR Suntour RUX 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? Read on to find out…

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

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.

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.

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.

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?

The SR Suntour RUX is so close to being truly competitive in the long-travel market. The potential is there though. If the spring and damper tuning can be reworked to compete on par with the current market leaders, then they will most definitely have a winner. The 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. Unfortunately the suspension performance leaves a lot to be desired, which is of utmost importance to any serious downhill rider or racer.

UPDATE: For model year 2015, SR Suntour has developed an updated negative spring which is said to improve small bump compliance. They have also developed a modified softer high-speed compression spring for the damper which will allow for more high- and low-speed compression adjustment, potentially addressing the performance concerns expressed in our review. The springs will be available for prior model year fork in late Spring, 2014. Contact the SR Suntour Madison, Wisconsin office for details.

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.

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Vital MTB Retail Partners:
Chain Reaction Bicycles Jenson U.S.A. Competitive Cyclist Backcountry

Specifications

Riding Type Freeride, Downhill
Travel 203mm
Spring Type Air Spring with 5 Position Air Volume Adjust
Damping RC2 Cartridge
External Adjustments High and Low Speed Compression, and Rebound
Crown Dual
Axle 20mm Tool Free Thru Axle
Brake Mounts Postmount Disc
Steer Tube Diameter 1-1/8"
Steer Tube Construction A7050
Stanchion Diameter 38mm AL7050
Colors White or Black
Weight

6 lb 5.9 oz (2.9 kg)

Miscellaneous For 26" Wheel Size
Price $1200.00
More Info SR Suntour Website
Vital MTB Retail Partners:
Chain Reaction Bicycles Jenson U.S.A. Competitive Cyclist Backcountry