Shredding enduro so hard you need a bigger fork but a dual crown is overkill? The all-new FOX 38 enduro suspension fork splits the difference between the 36 and 40 with, you guessed it, 38mm stanchions. Both of those models get updates for 2021, too, more on that further down.

The FOX 38 has 160mm-180mm travel, is available in Factory, Performance Elite, Performance and E-Bike models, with VVC GRIP2 and GRIP dampers and updated EVOL Spring. But that’s not all. From elliptical steerers, to lower leg bleeders, we cover all the tech right here…

2021 FOX 38 enduro fork tech details

2021 fox 38 enduro mountain bike suspension fork tech details and specs

FOX say the 2021 line-up boasts their stiffest, smoothest, most tunable forks they’ve ever made. Let’s break that down, starting with stiffness. The claim is a big one. Compared to the 2020 FOX 36, the new FOX 38 is 31% stiffer under transverse shear, 17% in the fore/aft plane, and 38% stiffer torsionally. Not to be sniffed at.

Aside from the additional 2mm diameter in the stanchions, how have FOX achieved this?

fox-38-elliptical-steerer
The FOX 38 is the only fork in the family with the elliptical steerer, but it may find its way onto other forks in the future

Short answer: The elliptical steerer.

It isn’t solely responsible for the increased stiffness, but it is a key piece of the puzzle. It allowed FOX to tune the stiffness to weight ratio by adding material where it is most needed for stiffness, and taking it away where it’s not needed. The ellipse is contained to the lumen of the steerer tube; the outer remains circular to fit standard headset bearings.

Stiffer, smoother lowers for both 38 and 36

For 2021, the all-new FOX 38 and updated 36 rock a brand new lower leg chassis, redesigned to improve that all-important stiffness to weight ratio. The arch now juts father forward, improving full-compression clearance on modern enduro bikes with bulky headtubes.

The new chassis has an aggressive aesthetic, with weight shed from the arch and axle clamp areas, in a bid to offset the additional weight of the larger diameter stanchions.

fox-36-factory
The 2021 FOX 36 Factory Enduro Fork with GRIP2 damper and redesigned chassis. All photos courtesy Fox Racing Shox.

How did they make them smoother?

On to the topic of smoothness. We already found the current offering of FOX 36 forks to be buttery smooth, but Fox found three ways to make them smoother.

fox-floating-axle-quick-release

First up is the 15mm floating thru axle. The concept of a floating axle isn’t new. In fact we’ve seen it on some FOX 36 and FOX 40 forks since 2015, not to mention the Öhlins DH38 fork. What’s new is that the floating axle is now quick-release.

Floating axles offer a distinct performance advantage due to their ability to match the exact width of the fork’s wheel mounting surface precisely to the front hub flange spacing. The result is perfect chassis alignment and the elimination of unwanted friction between the upper and lower fork legs. With the patent-pending quick-release, system spacing is locked in via a floating sleeve. This allows repeated front wheel removal and reinstallation while maintaining perfect fork alignment.

Wait. What?

fox-38-factory
The Pistachio FOX 38 of the Heritage Collection features the light weight Kabolt-X floating axle

You (rightly) might be wondering: How does an axle float to allow the hub to line up precisely? Unless you’ve used their DH forks, it’s unlikely you’ve ever used a floating axle fork. Here’s how it works:

Notice there’s a pinch bolt only on the non-braking dropout. The brake-side threads in like normal, and the hub’s flange rests against that dropout to ensure consistent brake rotor placement.

On the non-brake side, a sleeve sits between the dropout and thru axle. Once you put your wheel in, compress the fork a few times, close the quick release lever, compress a few more times, then tighten the pinch bolt. Voila, you’ve just positioned your wheel perfectly while allowing the lowers to remain perfectly aligned with the stanchions regardless of your hub’s actual width. The keeps everything sliding freely with no extra friction.

2021 fox kabolt-x tooled thru axle for new fox 38 and 36 mountain bike forks
The Kabolt-X has an integrated collar that replaces the sleeve inside the dropout.

Available optionally is the new Kabolt-X, a lightweight bolt-on floating axle exclusively for the 2021 FOX 38 and 36. Not only does it shave grams, it also increases torsional stiffness thanks to a sleeveless design. But, unlike with the quick release axle’s set-it-and-forget-it install, Fox says you’ll have to loosen the pinch bolt each time you remove the wheel when using the Kabolt-X axle.

Got it, now switch the channel…

lower-leg-bleeders
Lower leg channels and bleeders of the 2021 FOX 36 and all-new FOX 38 enduro forks

The redesigned lower leg of the FOX 36 and FOX 38 now features channels, the benefits of which are said to be twofold. First, they help the fork achieve full compression, under the right loads.

FOX explains it like this: “As a fork compresses, the air volume within the lower legs decreases, increasing air pressure. The more the fork compresses, the more pressure increases. This effect can have the unintended consequence of preventing full travel from being achieved. Our lower leg channels help alleviate this issue by dramatically increasing air volume within the lower legs and thereby reducing the amount of additional unintended pressure ramping.”

Another benefit of these channels is that lower leg bath oil is circulated to the upper reaches of the lower legs, continuously lubricating the foam rings and bushings as the fork compresses and extends through its travel.

testing the new fox 38 mountain bike fork

The new lowers of the FOX 38 and 36 forks also get bleed valves. Pressure build-up doesn’t just limit full travel from being achieved. It also diminishes small bump sensitivity and responsiveness. And it doesn’t just happen from fork compression. So, the addition of a bleed valve allows for atmospheric pressure equalization at the simple press of a button.

…to a better tune.

FOX 36 with VVC GRIP2 damper allows 8-Clicks of high speed compression and high speed rebound adjustment

Damping is also updated for 2021. The GRIP2 damper features 4-way adjustability – high and low speed compression,and high and low speed rebound circuits. So what’s new?

The compression circuits are now endowed with FOX’s proprietary VVC (Variable Valve Control) system, bringing 8-clicks of adjustment to the high speed compression circuit. We’ve previously seen VVC on the rebound circuits of the GRIP2 damper, on FOX 36 forks since 2015. Now for the first time, VVC adjusts compression damping too. Basically, it adds a higher quality of valving adjustments, feeling more like what you’d get by tearing down the damper and revalving it. Ain’t nobody got time for that.

The 38s’ air spring is all-new, and hard to explain

The FOX 38 uses a quasi-cartridge system for the air spring. Meaning, the positive air chamber is in a tube that sits inside the slider. So, tube within a tube. The space between those tubes is used as part of the EVOL (EXtra VOlume) negative air spring.

Why?

Most (basically all other) air forks use the inside of the stanchions as the air chamber, with a piston seal sliding along up it during compression. So, the positive air chamber sits at the top and gets compressed during, um, compression. That’s why your volume spacers go into the top of your fork leg. Because of the 38’s large diameter upper tubes, that positive air chamber’s volume would be too big.

Well, technically, it really meant that there wouldn’t be enough room in the lowers to create a large enough negative air spring. So, they had to find a way to reduce the positive spring’s volume. Thus, thus the smaller tube inside the stanchion.

Still, they told us the 38 has the largest negative chamber they’ve ever used, both in terms of absolute volume and as a percentage of positive volume (the positive air chamber is still larger than the negative). All that, along with using a smaller diameter piston than in the 36, means that, rider weights being equal, the 38 will run higher air pressure than the 36.

While designed completely differently, both the 36 and 38 get their oversized FLOAT EVOL negative spring to keep it supple over small bumps. As expected these days, it’s said to deliver plushness off the top, extra mid-stroke support, and more tunable bottom-out progression. The leg channels and bleeders, which both function to reduce air pressure captured in the lower legs, allow the EVOL air spring to operate freely without unintended interference.

2021 FOX 38 tech specs:

fox-36-integrated-mud-guard
The FOX 38 and 36 forks of 2021 feature an integrated fender, not compatible with older generation forks

You’ve heard the tech, here are the all-important “will it work for my set-up” details:

  • Travel options: 160mm-180mm
  • Wheel size(s): 27.5″ and 29″
  • Offset(s): 37mm, 44mm and 51mm
  • Available in Factory, Performance Elite, Performance and E-Bike Models
  • Damper options: GRIP2 with VVC, FIT4, GRIP
  • 8-CLICK HSC and HSR adjustment on GRIP2 damper
  • Starting weight (claimed): 2180g
  • MSRP: USD $949 – $1199 / CDN $1249 – $1579 / €1259 – €1589

2021 FOX 36 tech specs:

fox-38-factory

The FOX 38 with GRIP2 damper is available in Gloss Orange, Gloss Black and a limited edition Pistachio colorway. The Orange is available with 180mm travel only, the Black is adjustable between 160mm and 180mm, while the Pistachio is 170mm only. Offset also varies according to color. The Gloss Black is available in 37mm, 44mm and 51mm offset, while the Gloss Orange and Pistachio flavors are limited to 44mm only. The Pistachio is available with the Kabolt-X floating axle only.

  • Travel options: 150mm-160mm
  • Wheel size(s): 27.5″ and 29″
  • Offset(s): 37mm, 44mm and 51mm
  • Available in Factory, Performance Elite and E-Bike Models
  • Damper options: GRIP2 with VVC, FIT4, Live Valve, GRIP
  • 8-CLICK HSC and HSR adjustment on GRIP2 damper
  • Starting weight (claimed): 1965g
  • MSRP: USD $849 – $1099 / CDN $1129 – $1449 / €1339 – €1495

fox-factory-36

The 2021 FOX 36 with GRIP2 damper is available in Gloss Orange, Gloss Black and a limited edition Root Beer colorway. The Orange boasts 160mm travel with a 44mm fork offset only. The Gloss Black offers 150mm and 160mm travel options, with the choice of 37mm, 44mm or 51mm offset. The Root Beer flavor has 160mm travel with a 44mm offset. It features the Kabolt-X floating axle, which is 75g lighter than the QR.

All FOX 38 and 36 forks are spaced at 15mm x 110mm, with 1.5 tapered steerers. The direct post-mount takes a 180mm brake rotor but is compatible with up to 230mm rotors. Check out the FOX website for full details on the FOX 38 Performance Elite, Performance and E-Bike models, and the FOX 36 Performance Elite, and E-Bike models.

2021 FOX 40 dual-crown DH fork

FOX-40-DH-FORK-2021
What happened to the 49? Nothing! It’s still here. It’s just called 40 now.

The new 2021 FOX 40 dual-crown downhill dedicated fork gets all the tech updates seen on the FOX 38 and 36 enduro forks, distilled into 203mm of 40mm stanchion mediated travel. That’s the new chassis, lower leg bleeders, new air/oil channels, new arch shaped for improved headtube clearance, plus a 110mm x 20mm pinch-bolt floating axle. Here are the details…

FOX 40 DH FORK AXLE

  • Travel options: 203mm
  • Wheel size(s): 27.5″ and 29″
  • Offset(s): 48mm, 52mm and 56mm
  • Available in Factory series only, with Kashima Coating
  • Damper options: GRIP2 damper now with VVC, GRIP
  • 8-CLICK HSC and HSR adjustment on GRIP2 damper
  • Weight (claimed): 2816g
  • MSRP: USD $1749 / CDN $2309 / EUR €2299

fox-40-factory-DH

FOX Heritage Collection

The limited edition 2021 Heritage Collection draws inspiration from the original 36 and 40 – the iconic forks that shaped modern enduro and downhill riding 15 years ago. So, in celebration of the new FOX 38 addition, FOX have released a limited edition Heritage Collection run of the 36, 38 and 40. All Heritage Collection forks feature special black adjuster knobs, a Kabolt-X axle, and include a matching graphics kit, compatible with all 2021 and 2020 models of FOX rear shocks.

fox-38-pistachio-heritage

No specifics on numbers, but Fox say the Heritage Collection forks are available in extremely limited numbers at time of launch only. Act fast!

RideFox.com

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