Niner Carbon MTB Fork Review (RDO BOOST): The History of Rigid

Interested in turning your hardtail into an efficient, Tour Divide-ready bikepacking rig? Or just keen to have a pure rigid experience on the trail? To accomplish either of those pursuits with the most advanced means possible, the Niner RDO BOOST MTB Fork is one of the few trusted, ultralight, carbon forks on the market that’s directly interchangeable with modern thru-axle suspension forks — plus it fits 29+ tires and has bottle mounts. We built up a Timberjack Ti with one and took it into the Caucasus …

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Before I dig in, some folks might immediately ask, “What place does a fancy rigid fork have in the modern world of bleeding-edge and fully tuneable suspension?” To that I’ll let history provide some insight. It wasn’t until the late ‘90s when decent mountain bikes required some form of suspension to be considered a reputable tool for the trail. Then came rear-suspension, which of course wasn’t nearly as efficient, nor as pleasant, as current iterations. Soon thereafter, any mountain bike that didn’t feature at least one springy component was deemed an outdated apparatus. And anyone riding such a rig was a masochist. Then came the 29er, whose big, bump-squelching wagon wheels reminded folks that rear suspension wasn’t a “must”. With a little skill and panache, and a bit of love for suffering, a hardtail or fully rigid bike could be ridden just about anywhere.

Nowadays, tubeless tires accommodate lower tire pressure, and meatier plus-sized tires provide yet another layer of cushion, so anything is possible on a rigid bike with the right mindset. A fully rigid setup may not appeal to everyone, but it certainly has its merits in weight savings, pedaling efficiency, and freedom from maintenance — three things important to most racers, as well as some folks who tour longer bikepacking routes… and, to those of us who appreciate the simplicity of a rigid trail bike.

Niner Carbon MTB fork Review, Boost RDO, 27.5+, 29+

So who spends $500+ on a rigid fork? I’ll defer that question to folks who’ve embraced this monocoque carbon fork since its release back in 2008-2009. Rationale would likely include words such as accuracy, responsiveness, weight savings, and the chatter-absorbing characteristics of carbon. All of which interest folks in the endurance racing world. And, all of which are immediately evident when riding this fork, as I can now attest. On the outset it is no doubt a bit of a conundrum that such a fork can compete – both financially and technologically – with a suspension fork of a decent caliber, and find success in the market. But having spent a fair amount of time on rigid bikes with carbon forks I can see the draw, and what keeps a seemingly outdated component interesting, and to some, exciting.

  • Niner BOOST RDO MTB Fork Review
  • Niner BOOST RDO MTB Fork Review

Niner Carbon MTB fork Review, Boost RDO, 27.5+, 29+

Niner RDO BOOST MTB Fork, Past and Present

Introduced in 2008-09, the original Niner carbon RDO fork practically created its own category. They’ve since upgraded it a couple of times. All the while it’s been a mainstay amongst singlespeeders, endurance racers, and sufferfesters alike. Mostly it’s used on hardtail frames with the intention of going fully rigid. Back in the heyday of 29ers, the RDO fork could often be spotted on classics such as the Karate Monkey, Kona Unit, Niner Air 9, and Salsa El Mariachi.

The latest revamp was released in the first quarter of 2017. The popular platform was modernized with the addition of a 110x15mm bolt-through BOOST Maxle, clearance for 29×3.0″ tires, mid-blade bottle mounts, low rack mounts, and Niner’s RDO carbon construction. It has all the new standards, which makes it quite advanced considering its old school context. The latest version also has a tapered steerer, which by its very nature — a monocoque construction paired with the stout bolt-in Maxle — ties the bike’s steering about as directly to the trail as physically possible. Theoretically, the result of all this new tech results in a very solid fork and a stiff wheel yielding the most advanced rigid front-end available.

Niner Carbon MTB fork Review, Boost RDO, 27.5+, 29+

  • Niner BOOST RDO MTB Fork Review
  • Niner BOOST RDO MTB Fork Review
  • Niner BOOST RDO MTB Fork Review

Matching a rigid fork, by the numbers

Most of those aforementioned 29ers were designed to accommodate a 100mm suspension fork. The Niner RDO fork was originally engineered with that in mind. When looking at those specs the two most important numbers are the axle to crown (AC) height and the rake (AKA fork offset). The AC has a direct impact on several important factors in a bike’s geometry, namely the head angle, seat tube angle, and bottom bracket height. When converting a suspension bike to rigid, you’re ideally looking for an axle-to-crown that mimics the ride height — with the suspension sagged — to maintain the handling of the bike as it was originally conceived. The AC height of the RDO is 490mm. A 100mm travel 29er fork typically has about a 510-520mm AC, give or take a few millimeters, so with 20% sag (20mm), a 490mm rigid fork would be an excellent match. The Surly Krampus, designed for a 100mm travel fork, is a case in point. The specced steel fork on the Surly Krampus has an AC height of 490mm, and a similar offset of 47mm.

So how about 27.5+ bikes? Most trail bikes in this category, a breed of bike cherished by many bikepackers, are specced with a 120mm travel fork. The Jamis Dragonslayer, Marin’s Pine Mountain, Surly Karate Monkey, and Kona’s Big Honzo, are a few that spring to mind. Suspension forks for 27.5+ with 120mm of travel often have a similar AC height and offset. The 27.5 Fox 34, for example, has an AC height of 525mm with a rake of 51mm. At a 20% sag this would make the intended AC height right about 500mm. Theoretically, when swapped with the Niner RDO fork, it would drop the front end by about a centimeter and steepen the bike a hair. It would also drop the BB height ever so slightly when compared to the bike’s claimed geometry. But given the fact that there is no additional travel on a rigid bike, this should be just fine in most situations. In the case of the Timberjack Ti, a bike made to work with either 27.5+ or 29er hoops, that’s generally specced with a 120mm fork, the 10mm difference was not at all an issue. The slight shift in geometry steepened the seat tube a touch while keeping the front end slack enough to stay trail savvy. In my opinion, that shift actually improved the geometry. And with ‘wide-trail’ 29×2.6” tires, the bottom bracket was plenty high to avoid pedal strikes. In fact, unless you are working with 27.5+/120mm travel bike that already has an unusually low bottom bracket, the Niner Carbon RDO MTB fork should be a pretty good fit.

For reference, here are the AC heights for several common forks. Note that these measurements are often consistent across multiple models of the same manufacturer, but check to be sure.

Rockshox Pike

120mm (27.5): 512mm AC
100mm (29+): 523mm AC
110mm (29+): 533mm AC

Manitou Machete

120mm (27.5): 516mm AC
100mm (29): 510mm AC
120mm (29): 530mm AC

Fox 34

100mm (29): 517mm AC
120mm (29): 527mm AC
100mm (27.5+): 515mm AC
120mm (27.5+): 525mm AC

Niner Carbon MTB fork Review, Boost RDO, 27.5+, 29+

  • Niner BOOST RDO MTB Fork Review
  • Niner BOOST RDO MTB Fork Review

Salsa Timberjack Ti, 29 x 2.6

Contrary to this article’s intro, the bike shown here is not destined for the Tour Divide. My intention was to build a bike for fast bikepacking and quick route scouting. For this purpose, the Timberjack Ti frame with a carbon RDO fork was the perfect pairing to keep it light, nimble, and efficient. As it happens, the TJ was destined for overseas adventure straight out of the gate. However, our trip to the Republic of Georgia’s Caucasus Mountains was cut short, so this is by no means a long term review. Instead, this should be considered 300 mile ride review as well as a report on my line of thinking as to why I chose this fork for such a rig.

As mentioned, the fork had to meet a few requirements, including a tapered steerer and BOOST 110 thru-axle. And of course, room for 29+ tires was a must. I am currently running 29×2.6″ Schwalbe Nobby Nics on 35mm inner width rims, but I wanted to keep the option of running 2.8s as well. The Niner RDO still has loads of space and can comfortably fit 29×3.0″ tires, without a squeeze. Having plenty of air between the tire and a fork legs is pretty important; I’ve seen the inside of a carbon fork get chewed up from a tire caked with mud and gravel. That fact also reinforces the value of BOOST spacing and a thru axle. 100mm QR 29+ wheels are not the stiffest, by any means. They have plenty of flex. So a muddy tire flexed a few millimeters to one side or the other could be the source of abrasion against the fork’s interior…

  • Salsa Timberjack Ti, Best Bikepacking Bikes 2017
  • Bikepacking Tusheti National Park

Touring With Carbon

Some folks might immediately dismiss the idea of long distance bikepacking on anything made of carbon, but I am completely confident in carbon forks, many of which are equally as robust as steel forks — and perhaps even stronger. As a case study, Virginia has several thousand dirt-touring and bikepacking miles on her Salsa Firestarter carbon fork at this point. It’s been pogoed over all kinds of tracks in Africa, beaten up in boxes on flights, strapped to roof racks, and ridden over some ridiculously rugged terrain. Still, I didn’t give a second thought to her bringing it along on this trip as well, battle scars and all.

Niner’s carbon forks have been around a relatively long time. The carbon RDO has been tested over the years and beat to no end by singlespeeders, endurance mountain bikers, and rigid aficionados. It’s certainly been a common sighting around rocky Pisgah and the root-strewn East coast over the years. If second-hand assurances aren’t enough to convince you, Niner is so confident in the strength of their product that the Boost RDO Fork is backed by a 5-year warranty. In addition, the upgraded tapered steerer would theoretically make it even stronger than this one:

  • Niner BOOST RDO MTB Fork Review
  • Niner BOOST RDO MTB Fork Review

There is one area for concern with long distance bikepacking on carbon frames and forks. Straps and bags can inflict some serious damage to carbon while rubbing against it day after day for miles on end. No other place is more vulnerable to this kind of damage than the base of the headtube and the fork crown. With the strap at the base of the handlebar roll or harness — as well as the bag itself — constantly moving against this area, deep gouges can form over time. The same can be said for steel. I’ve had straps rub down to the bare metal and then some. But, carbon is more sensitive to abrasion, and I’ve seen gouges that almost became holes.Fortunately, it’s easy to protect against this. I use a product called Shelter by Cantitoe Road. It’s like a thick gel tape that, when applied neatly (not as shown0, is almost invisible. There are other brands too, such as Everclear, by Miles Wide. This thin layer provides complete protection against straps and other wear. In addition, there are are handlebar harnesses such as Salsa’s Anything Cradle and the Specialized Bura Bura, which clamp to the bars, eliminating such straps and keeping the load away from the headtube and fork crown.

Ultimately, I have very few gripes with the Niner Carbon RDO fork. It rides well, has all the bells and whistles I want and need, and I expect it to last a long while. However, it isn’t without fault. I would really like to see Niner add a third bottle mount on each blade, so they can accommodate triple mount cages such as the King Manything Cage. Alternatively, Niner could space move the current pair of mounts down so the bottom rack mount doubles as a triple cage mount. With the pair as is, it could be argued that the current mounts are placed a hair too high on the fork legs when used with larger water bottles and a handlebar roll. While using full one liter bottles, such as my prefered Zefal Magnum, the location of the mounts makes the bottles sit a little too close to the handlebar roll. Although it took a little more effort to remove and replace these long bottles, this issue wasn’t a deal breaker, and the spacing is just fine with standard size bidons.

  • Niner BOOST RDO MTB Fork Review
  • Niner BOOST RDO MTB Fork Review

Pros

  • One of (of not the only) carbon MTB fork with BOOST hub spacing and bottle mounts.
  • Fits 29×3.0” tires.
  • Longstanding history which has proved the RDO fork’s durability.
  • Bottle and rack mounts.
  • Simple, clean design.

Cons

  • No third bottle boss for Anything or Manything cages, or bags like the new Oveja Negra Bootlegger.
  • No internal dynamo wiring.
  • Model Tested Niner BOOST RDO MTB Fork
  • Axle 110x15mm bolt-in Maxle
  • Axle to crown 490mm
  • Rake 51mm
  • Weight 585 grams (20.6 oz)
  • Price $550
  • Manufacturer’s Details Link

If you can’t support a local bike shop, find it at Tree Fort Bikes

WRAP UP

When I was building this bike last summer, there weren’t many carbon forks available that fit of my requirements, and there still aren’t. There are even fewer that are interchangeable with the latest BOOST 110mm thru-axle suspension forks. The ability to swap a suspension fork and not be required to have another wheel was in my best interest. This might also be the case for some bikepackers whose trail hardtail doubles as their bikepacking race rig.

In addition, the Niner RDO BOOST MTB fork is about as versatile as they come. It fits up to 29×3.0” tires, has plenty of mounts, and works well with a 27.5+/29 trail hardtail.

Ultimately I chose the Niner RDO BOOST MTB fork because it was the only carbon fork available that ticked all the boxes. But it also has a long history of durability, which was crucial when considering a component that would be taken into the middle of the Caucasus mountains and beyond…

  • Kevin Mulcahy

    I believe the carbon fork from the Trek 1120 has bottle mounts and has boost spacing. Should be available through Trek dealers.

  • nat

    Would one be able to get away with drilling a hole on the front/top face of the fork just above the arch to run wires inside from a dynamo? Like this? http://uploads.disquscdn.com/images/76684d954a4071720a1798cd74a8a6fb5e88bb1bdb717ba71e16d62321a6c70d.jpg I know it would void a warranty. I’m guessing that’s a big no no but wonder what you think?

  • Shyone

    Do you have enough experience to say how it compares to the Salsa Firestarter fork, which I find rides harsh. One of the things I appreciate about road/gravel bike carbon forks is that they are supple and shock absorbing. Maybe that’s not possible to achieve with a carbon fork suitable for carrying bikepacking loads in rocky terrain.

  • Hmm, that’s a tough comparison. Namely because the Firestarter forks I’ve tried have been on different bikes, tire sizes, etc… and only on short rides at demo events. Gin has one on her Deadwood, but has never really ridden another to compare it with. That said, I don’t find the RDO fork harsh, but 29×2.6″ tires set up tubeless at or just under 20PSI probably play into that. I will say that I have been impressed with how this fork feels overall since day one… and I feel like it does a pretty good job at taking vibrations and chatter out of the ride.

  • I am not sure, to be honest. I probably wouldn’t do it…

  • Good point. it certainly wasn’t out at the point when I built this bike. I would be curious to know if it is available, and at what cost. Also, it looks as if it has less rake than the Niner…

  • Eric Fosdick

    The niner fork changed the rigid fork game but it was far from the first carbon fork on the market. There were a while handful of carbon tube with alloy crown forks that paved the way.

    As someone who has put thousands of miles on the latest version of the rdo, and each version before it, it rides pretty nice but rigid certainly isn’t for everyone. And there is basically no need for a third cage mount. I did white rim last year with a gallon of water on each side on a Blackburn cage. It did great. I also did coconino on it with a little less weight up front but it still did great.

  • Yeah I remember those alloy/carbon tube models… still see them around from time to time. I’d be curios to find out who made the first carbon monocoque fork. I couldn’t find that tidbit. Niner definitely cornered it though…

    I would like to see a third mount though… I agree that Blackburn cages are useful, but a third could allow options (like the Oveja Bootlegger or other such bags/cages), and lower mounting for a two bolt cage… and it wouldn’t be that big of a deal to add.

  • Eric Fosdick

    You don’t know how hard it was to get two mounts! I think the first carbon tube/alloy crown forks were made by woundup. I think niner was the first monocoque. But before that you had bontrager, white brothers, origin8, dt Swiss?, And more. They were more forgiving than the niner forks but if you ran large rotors then you would start to see their downfalls (when the tire hit the downtube)…

  • Ha! Yeah, they were noodly. I borrowed my buddy’s Misfit 29er SS for a week or so; it had one (can’t remember the brand, maybe Orgin8) … but I remember that feeling.

  • Shyone

    Thanks!

  • Pawel Kudela

    I think that there is also other fork which tick all the boxes, namely Travers XC Prong Boost Carbon but I don’t have idea about its durability.

  • Scott Loveless

    The 1120 fork is currently unavailable and there is no ETA. I’d imagine they’ll be inbound with the next batch of bikes. Rake is 51mm, axle-to-crown is 510. MSRP is $400.

  • Interesting.

  • Alan Love

    Regarding the lack of a 3rd eyelet for Anything-like cages, it looks like the lowest rack/fender mount is inline with the other 2. Would Wolftooth’s extra long B-RAD 4 system stretch across the 3 mounts? If so, problem solved. More bits to buy, but it would allow some extra security for those larger cages. I’d rather see Niner add the third eyelet in the standard 3 hole configuration in the next redesign, but until then…

  • Henrik

    Drilling a hole in carbon, makes for a very high chance to start pull fracture. The Salsa Cutthroat fork has dynamo cable routing.

  • I think so… otherwise you could use the B-RAD 3 and the included rubber pad and zip tie.

  • Barry Kyler

    The B-RAD 4 does work but I prefer the B-RAD 3 (without zip tie). Still had the templates here at work so added a couple photos. I use the Anything Cage and mount Wanderlust Monida Bags (11″ high) so there was no benefit to go with the B-RAD 4 in my case. Happy Trails! http://uploads.disquscdn.com/images/32ab32b27f217374bae5450a95d6a1f6c828a20b8ef024efdbbe634a6da8f9b7.jpg http://uploads.disquscdn.com/images/6f216cca6c96ac5c8d585fbb59785de93b967074180d97d396bbba5a45dd61cb.jpg

  • Nice.

  • Scott Loveless

    Well, that didn’t take long. Trek has a few in stock now.

  • Do they sell the front rack too?

  • Scott Loveless

    It looks like they have a few in stock. About $130 retail.

  • Cool, thanks. is this online or through a retailer portal?

  • Scott Loveless

    Any Trek dealer should be able to order these for you. You’re looking for part number 561208 for the fork, and 560997 for the front rack.

  • Mark

    Really interested to know how the Timberjack Ti frame went. Am very interested in it as I have a steel El Mariachi and want something a bit longer and lighter for long distance bikepacking. Is it any good?

  • Hi Mark. I have a little writeup coming sometime soon. More of a pictorial/rider and rig kind of a thing than a review — since it all depends on how you build it. But I will say that I love it. the steep seat tube, slack HTA and long stance make it perfect for my style of riding.

  • Mark

    Hi Logan. Sounds perfect. It’s so tempting, think I better start saving… Look forward to your writeup. Cheers.

  • Stephan

    Any idea what the Bontrager 1120 fork weighs?

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