Review: The Suntour Auron 27.5″ Enduro Suspension Fork

Suntour Auron Santa Cruz BronsonCycling is an expensive sport and few components are as important to the feel of full suspension mountain bike as the front fork, so we’re always eager to test new products that promise to save of us some cash without sacrificing performance.

The new Auron fork is Suntour’s premium offering in the burgeoning 150/160mm 650b trail/race/enduro market. It’s reasonably priced, weighs less than some of the ultra premium offerings by competitors, and there’s even an option with both high and low speed compression, so how does it perform on the trails?

Weight Sunout Auron 27.5 Weight

On our Park Tools scale, the Suntour Auron weighed in at 1.96 kg or 4.05 lbs without the steer-tube shortened. This scale shot is in both kilograms and pounds, because we love our non-’Murican readers.

TechSuntour Auron Adjustments

The Suntour Auron in available in four different iterations. The entry level model of the air fork offers only rebound adjustments, the RL version we tested ($650) has both rebound and low speed compression knobs, and the premium RC2 offering ($700) gives riders the ability to tune both rebound and high and low speed compression.

An additional travel adjust model, the TA-RC2 ($800), is also available. This model has low and high spreed compression, rebound adjustment, and can be switched on the fly between 160-120mm of travel.

Suntour Auron Crown and StanchionsHollow forged magnesium crowns help keep the weight down

Suntour uses a pretty standard suspension configuration, with with one leg housing the air system, and the other a closed cartridge which handles damping duties. Whats special is that all Suntour forks use grease rather than oil to lubricate the internals. The advantage to this is apparent when it comes service time. The lack of oil means you can easily adjust the travel, make quick tuning changes, etc.. in just a few minutes. No mess, no fuss. We see this as a huge advantage for racers on forks like the Rux DH, which has an air chamber that can be easily tuned with spacers in minutes.

The only potential downside noticed is that this fork did have a tendency to weep more than comparable products. After each ride, the dust that built up on the stanchions tended to cake thickly around the seals and needed to be cleaned. That said, the fork still feels smooth after months of riding, so the seals seem to be performing their job.

Suntour recommends that the lowers be cleaned and relubed after every 50 hours and that a full cartridge rebuild be performed after every 100 hrs. The full cartridge rebuild consists mainly of draining the old oil and adding fresh lubricant. At the factory, the high grade felt oil wipers are soaked in a light oil bath for least 30 minutes before being installed (which is also recommended you do during rebuilds) and then grease (they use Slickolieum…which is a favorite of ours as well) be applies on the bushings and dust wipers. Additionally, riders can add up to 20cc of oil in the lowers for splash lubrication. If you choose to go this route, Suntour recommends using lighter weight oils, such as 0W fully synthetic.

Suntour Auron Axle Mechanism
Look towards the bottom of the fork and you’ll find the rebound knob in it’s standard position and post mount disc brake mounts.

Suntour Auron Axle Loc2Holding the axle in place is Suntour’s propreitary Q-Loc2 system, which is essentially a spring loaded collet. The red collet expands to prevent the axle from being released and turning the silver barrel allows you to adjust tension.

This one of the simplest axles to use on the market, all though we did have some issues removing the wheel after riding in muddy conditions. When we tried to remove the wheel, we had some difficulty getting the collet to collapse down enough to pull through the hub. It wasn’t till we hosed down and lubed the mechanism in order to remove any latent dirt particles that we were able to easily remove the wheel.

Set-Up

Suntour Auron Adjustments

This fork has been installed on two different high end mountain bikes for testing - the Rocky Mountain 790 MSL and a Santa Cruz Bronson. I put at least a hundred miles on this fork before passing it off to one of our local test riders for further testing, and he has since put a a few hundred miles on the fork. What is interesting is that despite not sharing notes, in order to avoid biasing each other, we came to very similar conclusions about the initial setup and performance of the fork.

We initially set the fork to roughly 20% sag, with minimal low speed compression. With this amount of sag, the fork felt very linear and smooth cruising the parking lot, but could easily be bottomed out by pushing down sharply. Adding clicks of low speed compression did seem to have some impact on the mid-stroke ramp up, but it made the fork feel less supple off the top, and did not mitigate the bottom out issue.

So we tried to find the sweet by reducing the low speed compression clicks by a few clicks, and increasing the volume of air until we had roughly 10% sag. This gave the fork a nice progressive feel under aggressive trail maneuvers, where suspension performance matters most, but had the adverse affect of sacrificing plushness at the top of stroke.

On the TrailSuntour Auron Action Shot

As suspensions performance is best tested on the trails, not the the bike path,  we hit our share of favorite after work loops, trail networks, and even some burly shuttle laps. Out here, that little extra time we spent figuring out how to dial in the Auron really paid off. Particularly when shuttling, where we could test different combinations of sag versus compression, it was very apparent that this is a fork that likes to be aired up.

Set it up with your standard ~20% sag and the fork has a tendency to eat through its travel. If you’re adventurous, you can remove the air spring and trim the elastomer volume reducer to get a more progressive linear tune (a modification that can’t be undone), but we chose to review the fork in it’s stock configuration. To make the fork more progressive Suntour suggests adding between 5-10cc of a 5-10 weight oil. Despite the lack of ramp up, lighter and less aggressive riders will be impressed by the smooth stictionless feel of the Auron. Even when hitting small to medium size drops, the bottom was not harsh.

Suntour Auron Fork

When jamming down trails with big hits and rougher terrain, adding that extra PSI made a huge difference in performance. The stiff initial feel didn’t soak up the little hits, which did cause unnecessary arm and hand fatigue, but it did a more than adequate job of smoothing out rocks and roots.  On shuttle days, places a150mm travel bike would have been considered out gunned a few years ago, the big hits had a tendency to bottom the fork out unless we were either ultra smooth or ran essentially no sag and dialed up the compression, but again – it didn’t suffer from excessive diving under hard braking or cornering and took bottom out situations really well.

After reaching out to Suntour about the fork, we were told that the travel adjust model has a more progressive tune than the RC model we tested. We were also told that they have now switched to a softer hi speed compression spring inside the cartridge, which will allow for a wider range of adjustment on the high and low speed compression settings.

While we give Suntour high marks for improving the adjustability of the fork, it didn’t do anything to mitigate our one major annoyance on the trail…the noise. In an era where modern bikes are whisper quiet, the Auron is jarringly loud. It’s so bad in fact your buddies might develop a running joke about its “mating call.” As soon as we installed the fork, we noticed it was louder than anything we’ve tested before. When rebounding, it would make a loud whooshing noise which bad annoying but bearable, but the noise quickly escalated to a high pitched squeal wooshing noise clamor (I don’t really know how to describe it, sorry) when the fork was rebounding quickly. According to Suntour, this is due to the rebound shim/shaft orifice sticking and does not negatively affect the performance of the fork, and can be fixed by doing a simple cartridge rebuild.

Aside from a few small annoyances, the Auron is a really nice quality product. Considering it retails for nearly half of what the other major players go for, it’s really hard to find anything to dislike. We wholeheartedly believe that someone with the knowledge, patience, and skill could rip the cartridge apart and tune this fork to perform flawlessly. Out of the box though, the RC fork, with it’s lack of high speed compression damping left something to be desired. The current tune will work well for novice riders purchasing this fork as an entry level because of it’s supple feel, and aggressive riders on a budget will be happy to sacrifice suppleness at the top of the stroke for the forks great performance on high speed descents.

Comments

Marcassin - 03/07/14 - 10:31am

Thank you so much for giving us the weight in metric system lately. Good guy Bikerumor :)

DaveG - 03/07/14 - 11:01am

“trim the elastomer volume reducer to get a more progressive tune”

You’ve got that 100% backwards.

Luiggi - 03/07/14 - 11:33am

@DaveG, I was about to note the same issue with this article.

@Saris, did you by chance open the air chamber? Perhaps the volume adjust elastomer had been already trimmed. That could be the culprit for the uber-linear feeling in the fork… I mean, I have already seen a couple of similar reviews of this fork, and none of them complained about it being too linear.

Spencer - 03/07/14 - 11:52am

DaveG- True; but anyone that doesn’t know that, probably isn’t tuning their fork for a more “progressive ride.”

GreenG - 03/07/14 - 11:58am

Unless “real” pricing is significantly lower, I can’t see a single reason not to buy a Pike instead.

Saris Mercanti - 03/07/14 - 12:13pm

@DaveG

Thats exactly what I was thinking when Suntour recommended trimming the elastomer – which is one of the reasons I didn’t do it, but check the other reviews of the fork. Evan Turpan actually trimmed the foam spacer extensively for his review on Vital. One thing to note is he and others were riding the RC2 model, with the adjustable high and low speed compression. The fork we tested lacked the high speed compression adjustment that might have ameliorated some of our bottom complaints.

I’ve used plastic spacers several times in the past to reduce the volume of the air chamber, and Suntour’s Rux Downhill fork employs a similar setup. Just so you guys don’t think I’m a crazy flip flopper, here’s a review I wrote in 2012 regarding the Fox RP23 volume spacer kit I installed on a bike with a regressive suspension curve:

http://www.bikerumor.com/2012/09/11/fox-float-air-volume-spacer-kit-installed-and-reviewed/

@Luiggi

I did not open the fork because I am lazy and it was (and still is) with one of our test riders. What I can tell you is that this fork doesn’t ramp up towards the end of the stroke, so it bottoms out if you’re riding aggressively unless you run almost no sag. For me and the much faster guy we have wailing on it, that means it’s not progressive enough.

Luiggi - 03/07/14 - 12:35pm

@Saris, that’s why I thought the fork might have been tweaked before you got it. It’s not clear in the review if it was brand new (it might be, since you weighted it with a full-length steerer) or if it was a sample product SR Suntour was handing to several people for testing/advertising purposes. If the latter was the case, it might have had the elastomer cut or completely removed, and as I said before that might have led to it being not progressive at all.

Anyway, thanks for such a comprehensive review and even more for replying our comments. This is what keeps me (and many more I think) coming back for more.

Saris Mercanti - 03/07/14 - 12:47pm

*Update*

I went back through my emails and updated the article. I had corresponded with Suntour some months ago about methods to make the fork more progressive and they referenced trimming the elastomer, which created an incorrect mental association. My apologies for the confusion and thanks for helping me get that straight. It was bugging the hell out of me

Mr. P - 03/08/14 - 12:05am

A fluid squealing sound is air pockets being stretched in the oil. Not good for consistent damping.

p

Dan Dacko - 03/10/14 - 11:28am

SR SUNTOUR official response. Trimming the elastomer under the air cap will make the fork more linear. Adding a small amount of heavyweight oil (gear oil 80+ W) will make the fork more progressive. These points were part of the discussion with BikeRumor and yes they would cancel if done together. There was a communication mistake made, we apologize for this.

The Auron is slightly progressive with the full air volume spacer, bottoming out is not something we normally see.

The Auron BikeRumor tested was brand new with no modifications, we did add new grease before sending out.

WE appreciate the comments and support. The Auron is a solid performing fork, we stand behind that 100%! We have 2 Demo fleets traveling North America if you want to test ride one.

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