When it first launched, the SR Suntour Durolux mountain bike suspension fork was designed to do one thing: Win enduro races. Originally only for 27.5″ wheels with 20mm thru axles, they’ve since introduced 29er versions and adjusting to fit the more common 15mm thru axle standard. Now, they’re adjusting again…by reducing the adjustments.

2018 SR Suntour Durolux enduro mountain bike fork gets new RC2 cartridge to improve rebound damping
Compression controls and damping circuits stay the same, including the PCS system.

The Durolux R2C2 was the top of the line, and will likely continue to be used by their sponsored pros, offering external controls for both high and low speed compression and rebound. Internally, that meant two separately adjustable circuits for each. On the compression end, things stay the same and they’re keeping their PCS (Piston Compensator System) and dual external adjustments.

2018 SR Suntour Durolux enduro mountain bike fork gets new RC2 cartridge to improve rebound damping

The rebound end is where things are changed. Now called RC2, they’ve removed the high speed rebound adjustment dial, instead relying on a pre-set factory tuned shim stack. This replaces the rotatable shim that covers the R2C2’s high speed shim stack, simplifying the system. Their rep told us that, in extreme circumstances, the R2C2 system’s rebound shims could bend permanently and possibly even break a shim, introducing loose metal into the system and causing total failure erratic rebound performance. It’s rare, but this new design fixes that, too.

The low speed rebound, which affects rebound speed on the top 1/2 to 2/3 of return travel and has a more noticeable effect for most riders, keeps its external, user-adjustable knob. (Want to learn more? Read our Suspension Tech article on rebound damping.)

In addition to the new circuit, they reduced the damping piston’s shaft diameter from 10mm down to 8mm. The total oil volume remains the same, so theoretically, this means less oil volume flowing through the circuit at any given moment. More importantly, they reworked the port shaping and flow path, eliminating some of the restrictions to create a more plush fork. Keep in mind, this fork is still winning EWS and World Cup races, so it wasn’t bad, they just thought they could do better. And for non-EWS winning pros, they thought a softer, more plush fork would be a step in the right direction.

The new Durolux RC2 cartridge is easily installed and available as a free replacement for anyone that owns the R2C2 cartridge. If you want. All new forks will come with the RC2 cartridge as the top-level offering for now while they take the R2C2 back to the lab. Oh yes, it shall return, but for now this means a $100 price drop. The 2018 Durolux RC2 forks will retail for $700 and are shipping now. (Note: You might still see the R2C2 on their website, but European and North American distributors aren’t selling it until the new version comes out.)



  1. What gets me, and not that it should because I understand the mechanics of it all, is just how, after more than 20 years (and thrice plus if you include development in the moto world) companies still can’t get things like forks and disc brakes ‘right’. They are not inventing Mars rovers here, just re-doing something that’s been some so often and by so many, that getting it ‘right’ just should not be an issue any longer.

    Yea, yea, I know, then they’d have nothing to sell/flog year in year out, but still….

    • I believe it comes down to matching manufacturing to a specific price point. To manufacture something requires investments in manufacturing processes, teams, tools, etc.; which although is absolutely achievable to do, but comes at a high price if done well (high quality, consistently). Just to make the tools and recalibrating and optimising manufacturing processes and equipment can be an incredibly expensive move for a manufacturer.

      Added to this calculation is the volume of produced units. High setup and manufacturing costs with low production volumes yields a very expensive product. Re-using existing tools, moulds, etc., compromising on quality and optimisation, and aiming at a high-volume segment of the market will yield a low-price-point product compared to doing the opposite.

      This is why Swiss watches are always more expensive than their e.g. Chinese copies which can not match the former’s quality, precision, longevity, etc. Another example would be the car manufacturing industry which explains why a better build car such as a Mercedes is more expensive and more durable (not all, but most) than a e.g. Ford or a Chinese Geely.

      Designing and engineering a “basic” product to perfection is relatively easy and “cheap”. Configuring the product’s production tools and processes can be very expensive. You have to keep in mind, which price-point (market segment) is the producer aiming at?

    • You sound like someone that’s never designed anything.

      In general, making suspension do what you want it to is pretty easy compared to adequately describing what you want it to do. Most riders have a very different idea of what they want than they did 20 or even 10 years ago. Remember the idiotic ideas of the past like Terralogic and SPV? Those technologies did what they were intended to do; what people thought they wanted suspension to do at the time, they’re outdated because no one wants suspension to auto-lockout any more.

      So really, it’s the customers being fickle that causes this. It’s not like there is an ideal suspension and they’re dragging their feet getting there. It’s a target that’s moved a lot in the past.

      • That is an excellent point about the fickleness of customers. Having said that, while that may explain a lot of what is complained about in the comments above, with companies constantly having to re-engineer a design that has lost favor with consumers, I don’t believe that it is the cause of the Suntour changes in the original article.

        The rebound shims bending, and high speed spiking due to insufficient oil flow capacity aren’t things that I think of as being hot 5-10 years ago, but are now out of style due to changing tastes.

      • I think you have it confused.

        The consumer did not want it, the companies did. In cycling especially, the consumer devours what is offered, especially if it’s new and shiny, every company knows that and they feed it, relentlessly.

        To use your logic, Terralogic and SPV were devices of the consumer, rather than an attempt for Fox and Answer/Manitou to ‘offer’ something better than the next guy.

        What you’re confusing is the idea that fickleness of the consumer causes the inability to design what effectively is a circuit that’s been in use for decades… properly.

        The role of suspension elements has not changed magically, never has. Their role now is the same now as it was when it first came out. Sure, travel amounts changed and how hard the systems were being hit changed, but what suspension is supposed to do… that has not changed.

        Rockshox came out in what, 1988/9? So what you are telling me is in the intervening time, between 1988 and 2018, so 30 years, suspension companies have not been able to ‘get it right’ because customers keep on changing their mind?

        I have a large tract of swampland I’d love to offer you for a great price.

        But if I do concede to one aspect of the idea, the cycling industry has created its own worst customer, that it now has a near impossible time to please. By constantly and relentlessly banging on how last season’s ‘product-x’ is not as good as this season’s, all because “we’ve added .2 grams of Ti and a leaf of carbon”, it has created an entire user base that thinks that 1. it knows better than it and 2. demands something new every year. Where after 30 years a fork is a fork and a disc brake is a disc brake, being expected to ‘reinvent’ them every year, otherwise you loose credibility, that is a system where nothing will ever be ‘right’.

        • Frip, I agree with most of what you are saying. Marketing depts drive consumer tastes to a large degree, and do constantly invent “improvements” as part of planned obsolescence. In the end, these “improvements” are often abandoned within a few years, and there is often a return to a design similar to the one before. The sensible thing, that I think you and I both would prefer, would be to see evolutionary steps, refining anything that needs it in current designs, and leaving the rest alone, rather than creating a false “revolution” that ends up sucking. A great example of this is RockShox dumping the awesome and sophisticated air/oil Mag 21 design, in favor of the closed plastic cartridge elastomer equipped Judy, only to abandon it and return to air springs and more proper metal damping components later. Another example is Avid/SRAM ditching the Juicy brake design, for the now loathed Elixer, before returning to very Juicyesque master cylinder architecture for the Guide. With a system like that, nearly everyone is forced to be an “early adopter” when they buy a new bike, because right when the company has started to get the bugs worked out of the design (assuming it isn’t fundamentally flawed), there is a whole new design released with its own fresh crop of bugs.

          To “i”s point though, there are exceptions. When suspension first came out, everyone was paranoid that it was going to suck up your pedaling power. Hence Terrelogic, SPV, and before that there were compression blowoff thresholds going back to the RS-1 in 1988/9. Then, as consumers became more comfortable with their suspension moving, companies could offer suspension that actually moved, and consumers were finally ready to accept that the pros outweighed the cons. Ideally they would have educated consumers on the proper mechanics of suspension right off the bat, eliminating that period, but people can be slow to change.

          • I agree with everything you said, but want to add that, while the internals of the first Judy forks were a step back compared to those of the MAG21, the Judy had much better externals- much bigger stanchions with far more overlap (although the brace was not as good in some ways as the MAG one). Also, I am not sure how much of the stiction from the MAG21’s air seals could be tuned out with lighter oil. A best of fork would have used the Judy crown, stanchions, and outer legs, and the MAG’s brace and air/ oil internals.

  2. Not all situations, riding styles and terrain can cause the issues. We found an issue and found it late, we admit that. We are working to make it awesome because we know it can work, as an example it has won WC DH races. Our engineering team is great and materials we use are good, just look at the millions of forks on the market today which make riding awesome for many. There are theories of the why and we are looking at them all. We have a great solution today with the RC2 PCS and we will take care of any customer that needs help.

    It happened and the solution will be awesome.

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