Fox Debuts New Downhill Fork - 40 RAD

Jun 1, 2012
by Richard Cunningham  
Kathy Sessler showed us some pics of the Santa Cruz Syndicate receiving and testing some prototype forks from Fox. From the pictures, we can say for sure that the new fork is a different platform. It's lowers are slender and the dropout extensions are visibly lightened. The Kashima-coated stanchions tubes are still 40-millimeters in diameter, but the fork looks far more compact than the previous 40. Behind the upper seal-heads are curious bosses with what appears to be fittings for threaded caps. There are a number of explanations for the unusual bosses: the simplest being a mounting position for a fender or a mud flap; or possibly a port for a remote spring preload adjustment (a feature common to road racing motos); with the most far-reaching guess being the integration of an electronic damping control.

Mark Fitzsimmons goes over the details of the new Fox 40 RAD DH fork with Greg Minnaar

Greg Minnaar inspects his proto Fox 40 RAD fork while Fox's Mark Fitzsimmons brings him up to speed on the features. Notice the bosses on the inside of the fork near the seal-heads and the super-slim sliders. Kathy Sessler photo

Greg Minnaar check out the 40 RAD axle and dropout

Mark and Greg inspect the new lowers and dropouts of the 40 RAD fork. The dropouts are visibly smaller, as is the entire slider chassis. Kathy Sessler photo

What Fox Racing Shox Has to Say

Fox Racing Shox would not comment on the new fork officially beyond saying that the name of the new fork is 40 RAD ( Racing Applications Development) and that it is truly an all new fork. Fox suspension guru Mark Fitzsimmons said that 90-percent of the 40 RAD fork's internals are retrofittable to previous 40 forks, which leads one to believe that 40 owners can upgrade to most of the 40 RAD's performance features.

About the fork, Mark Fitzsimmons said he would only speak in the broadest of terms: "Every part of the chassis is new. The goals were to design in some chassis compliance, keep the same stiffness, reduce unsprung weight, and to change the mass location. It does have a new damper that is designed to work with the new spring system."

Multi image showing old-style Fox 40 L with nwe 40 RAD fork features.

(Clockwise) The original Fox 40 on left is huge-looking by comparison to the new 40 RAD prototype fork. Note the raised section at the seal head - just enough metal to house the bushing and wipers. The 40 RAD fork crown has a new profile as well and its underside is more squared off. The new dropouts retain the dual pinch-bolts of the original, but are smaller, lend us to believe that the sliders may be no longer made from cast magnesium. Kathy Sessler photo

About That New Spring System

Fox and Trek developed a hybrid air/coil spring system for the Fox 40 equipped Session 9.9 that incorporates a titanium coil spring which is augmented by compressed air (an innovation well proven by the Marzocchi 888 and 55 forks). Trek initially had exclusive use of the Fox hybrid spring for the Session, which employs a standard shock pump to tune the fork spring, but now it appears that the same or an upgraded version will now appear on the new 40 RAD fork. The advantages of a hybrid air/coil spring are that it spring rate can be fine tuned for any track or weather condition, and that one spring can handle a wider variety of rider weights. Of course, any percentage of the fork's coil-spring rate that can be augmented by compressed air will also save a considerable amount of weight.

In a later communication, Mark Fitzsimmons corrected PB's guess that the 40 RAD's spring was a hybrid: "The spring system is unlike anything out there in the gravity suspension world. It is a 100% FOX design that has several different adjustments for individual riders' weight and riding style. It is not a hybrid system. The Trek World Racing team races on FOX designed spring systems."

Another view of the new Fox 40 shows what appear to be bleed valves for excess pressure. But this view also reveals a new truss structure to the brake arch--not a huge surprise on the revised truss as that was a key point shown at their 2013 product launch immediately prior to Sea Otter back in April

PB photographer Colin Meagher got this closeup of the bosses behind the seal head in the pits at Val di Sole. Interesting that the center appears to be a button of sorts - Air bleed valves? Negative spring adjustment?. (Note: Fox released at Val di Sole that the function is to bleed air from the lowers.).

Why the Skinny Sliders?

This is only guessing, but there is a possibility that Fox switched from magnesium lowers to aluminum. Aluminum is heavier than magnesium and in theory, magnesium has a better stiffness-to weight ratio, but magnesium can be quite porous, so it does not lend itself to thin castings. If Fox figured out a way to 3D-forge its fork lowers from aluminum in the same way that it produces its shock bodies (Squishing a billet of heated aluminum with such force that it gells and flows through the mold like plastic, producing a nearly finished part.), an aluminum slider could be created that would be thinner, stronger and lighter weight than its magnesium counterpart. While this is only guessing, Fox certainly has the intel and the resources to implement such a wild strategy.

Josh Bryceland and Greg Minnaar testing the new Fox 40 RAD DH fork

Peaty and Josh Bryceland testing the prototype Fox 40 RAD forks in preparation for the Val di Sole World Cup DH. Kathy Sessler photo

When can I get a 40 RAD Fork?

Our bet is that the 40 RAD will be in production soon. While the new fork is still in prototype form, Fox Racing Shox has always put its customers needs ahead of its racing development strategy. Fox would not have developed the 40 RAD if it had no intentions of bringing it to market. Expect to see the fork OEM on DH bikes in mid 2013 and at your most lucky LBS about the same time. Until then, all eye will be on Santa Cruz, Trek, Scott Lapierre, GT and Morewood riders at Val di Sole this weekend to see how Fox's 40 RAD holds up under the heat of World Cup DH competition.


  • 45 7
 son of a bitch!!!

I just ordered my new bike and 2013 40's (same as the 2012)
now they are going to release these!

first time I am on fox and they are already killing me before I even get my new forks!!!!!!!!
  • 36 2
 the 40s you have are still awesome though...
  • 14 2
 Really, you work in a shop. If you want the internals, just buy them at cost. Get your stupid bike already.
  • 180 1
 first world problems
  • 87 12
 Roses are blue, violates are red. I'm bad at poetry. Bacon
  • 25 7
 Hahaha you're also bad at spelling. I propped you cuz you said bacon tho. Bacon = Magic. It's like.. A unicorn.. That you can eat and not have to cry because you're eating it. Ahhhh glorious bacon.
  • 47 2
 Amazing how my comment about fox forks can turn into something about bacon and unicorns.... Only on PB!
  • 12 0
 you've gotta love the randomness of comments on here Big Grin props to you all Big Grin
  • 10 1
 bacon is meat candy haha
  • 1 9
flag Matt-Ivory (Jun 2, 2012 at 9:30) (Below Threshold)
 Anyone ever tried bacon jam? Food of Gods.
  • 3 0
 Can't say that I have.
  • 5 0
 Better Picture -

Also... Bacon.
  • 3 0
 Ohhh, I was staring to think those mounts were for rim breaks, this is cool too.
  • 1 0
 @ six66 what a f*ck did i just read ??!
  • 23 1
 dang, super excited to see what else fox has under their sleeve
  • 23 2
 same here, they have too many fun things behind closed doors that should be produced

"Fox would not have developed the 40 RAD if it had no intentions of bringing it to market."

wish the same could be true for the inverted prototype they dropped
  • 60 1
 but will it blend?
  • 13 0
 The inverted proto was a bit of a troll. Fox built it to test and prove some very specific things. It was abandoned almost immediately after initial testing. I got to check it out at the Fox factory - Must have been an expensive experiment. RC
  • 5 0
 wasn't it dropped because to achieve the same stiffness as the right-way up forks, the forks wouldn't be viable weight wise? and the maintanence required would have been a lot more than any other forks on the market?
  • 1 0
 Thats true ^^
  • 2 0
 I was so pumped when I read the title. I thought this was actually about bringing back the inverted one... But this looks just as good.
  • 3 1
 pinch bolts!?!??!?! ewwwwwwww!! gross make them go away. how could they go backwards in technology???
  • 3 0
 Don't forget the one-piece titanium crown/steerer fork they were promising to bring to market for 2011...ebay dealers were going nuts doing pre-order sales of the things, and then Fox just decided.... "oh sorry, we changed our mind".
  • 3 2
 ohhh ffs the maintenance of last years inverted prototype would have been no diferent compared to a regular fork certainly nor more than a boxxer world cup hahaha... where do people get this stuff in their heads... the reason it was canned was because they couldnt get the stiffness up without increasing the weight to what was considered too high and *deeeight* they did release the titanium crown steerers but they were only designed for the xc f- rangeei the f80, 100,120 chassis were all availible with titanium csu options .... pull your head outta your asses people!!!
  • 3 0
 No...they didn't...the titanium steerer F-series forks were cancelled just as production was beginning last year with no explanation. The model was removed from the website and all dealers pulled listings for them. There's no such option for them on the fox website.
  • 1 0
 well they were definately availible here in the uk i had a mate who nearly bought a set from mojo!!!
  • 14 1
 lowers are still mg, the bosses are for venting air and "hybrid spring" is air preload we had forever. the only real news is some weight shedding.

move along, nothing to see here.
  • 3 0
 Yes, those lowers still scream mg casting. Good luck forging the lowers in one piece! That would be very tough technically and hella expensive.
  • 12 2
 i read in a different article the bosses were for purging excess air. i might just be being thick...but if they were for purging air would it only be on the air/spring side and not on the cartridge side as well? i guess if the air collects in the lowers they that isnt the case...but whenever i've needed to purge the air, or as we call where i'm from "burping" you just loosen off the bottom hex nuts and give em a tap, pretty easy...hopefully they are actually grease ports for maintaining the beaut shakira coating compression action yo.

but actually, i think we all know exactly what is going on...they're f*cking V-BRAKE BOSSES SUCKA. MAGURA HYDRO V-FTW
  • 1 0
 Could definitely be mg casting, maybe pressure injected from the bottom of the casting like BMWs mg engine blocks
  • 1 0
 Colin Meagher's new closeup pics from Val de Sole look like magnesium castings (I added one in the story, more in his feature)..
  • 5 0
 Just below the seals are what appear to be oil ports which would allow the user to apply grease directly to the seals.
The old manitou had that option
  • 2 0
 Exactly what I was thinking! Grease ports.
  • 4 0
 Considering the location, isn't this the obvious answer? A lube/grease port?
  • 1 1
 Well, non inverted forks like this shouldn't need bleed ports because the air naturally rises to the top. In inverted forks the oil sits at the bottom and the air on top of them builds pressure forcing the oil below it, out your seals. And Crakmasta, if they were for bleed ports, they would want them on the cartridge side, not the air spring side, because that is were air and oil would mix, but fox uses a bladder to isolate oil, so this should also be irrelevant anyways. Who knows, maybe I'm talking out of my ass, grease ports seem logical, but that just like a patching a tube, it gets you down the hill but rarely lasts in the long run. I mean, I guess a lube/grease port does make sense, because there is no oil to lubricate the seals like an inverted and/or open bath system. So if the ports are to keep the seals lubed it makes sense, but packing your seals with grease to keep them from leaking is just a band aid fix.
  • 1 0
 does not look like a grease port? anyone familiar with grease ports would expect to see a Zerx-style fitting with spring-loaded BB centre for the grease gun tip to mount into

unless the 2 small bolts are removed, then the silver plate to expose a greasing port, but its not good practise to continually remove/install bolts into threaded Mg Alloy castings, unless there are steel helicoils in there

we keep guessing???
  • 1 0
 If it's for oil, my thoughts were that button could be depressed by a syringe and open the 'valve', letting oil flow around it once it's been pushed in.
  • 1 0
 Ya, I mean they look like air bleed ports to me, but bleed ports just don't make sense to me and grease kinda does. But what do I know, obviously fox knows more than me so I suppose we'll see with a pr.
  • 1 0
 my oppinion is that fox has become so obsessed with weight that theyre for attaching a vaccum pump to suck all of the air inside the fork can be removed to save oj its realistically an port for oiling the foamies in the forks... prob not recomended for use all the time but it would make sense if youre doing a few weeks on holiday riding and your forks needed servicing but its inconvenient to take that many tools... solution.. unscrew add oil and re attach cover.... would make allot of sense... something like that on my 36 180s would be a godsend!!!
  • 1 0
 @crakmaster88 Its KASHIMA coating not shakira, she's a singer. Sick of people.gettimg it wrong now!! :/
  • 5 0
 Those "buttons" on the lowers actually are air vents to remove excess air from the fork. This air pressure seems to increase the progression of the fork the longer you ride it and has nothing to do with the actual air spring. The air can be released by simply pressing these buttons. See here, if you know German Wink
  • 6 0
 Fox is just throwing marketing BS at you guys. They should be spending more time reducing friction on FIT dampers and improving the range of adjustment, proper bushing lubrication systems etc.
  • 1 0
 Thank you! i didn't have to say it haha
  • 8 0
 Why do i never understand these thingss...
  • 45 0
 haha totally. all I'm thinking is "will girls like it?"
  • 3 29
flag Williss (Jun 1, 2012 at 21:11) (Below Threshold)
 chicks dig bmx riders Wink why am i even reading this?
  • 23 1

Because your balls finally dropped?
  • 6 1
 chicks do not "dig" people that ride kiddy bikes
  • 2 0
 @Williss, how about you man up and ride big wheels instead of pissing around on kids bikes?
  • 7 0
 looks awesome, only downfall is that I always thought the Fox 40's huge sliders and dropouts looked awesome :p
  • 3 0
 I agree. I'm down for better tech/weight/strength but keep the growling monster looks.
  • 1 0
 The single most important thing many of us can take away from this - as we won't be fondling, demoing, or owning this fork anytime soon - is that it still looks like a big bad Fox 40. Definitely interested to hear what's going on inside at some point too though...
  • 2 0
 Cunningham's theory on the reason for the "unusual bosses' behind the seal head is a bit odd, considering Fox confirmed what they are yesterday and it's been all over the web:
  • 2 0
 Fox didn't reveal what the ports were for until AFTER RC had written this article and submitted it for publication, and after a good number of other articles appeared several days ago on Bikerumour, Bikeradar and other places. A few days ago, the leading speculation on the ports was for greasing the seals.
  • 1 0
 Thanks Deeeight, I couldn't get that info from Fox when I wrote it. The buttons on the ports would not be necessary to lube the seals, and race forks are usually lubed before each race run anyway. Air bleed makes perfect sense, but I would like to know if it is an adjustment function or a way to bleed of unwanted air pressure that builds up behind the seal head during a race run. The Fox racers seem to be enjoying the fork at Val de Sole, eh?.
  • 1 0
 Really funny that they're releasing the air/coil hybrid now, because I asked the Fox guys at Interbike last year and they said that they would never bring that technology to a production fork for anyone besides the Trek guys.
  • 1 0
 the bosses behind the seal head could maybe be for an easier lubricating grease change or something like that? because i think for negative spring adjustment, a one-sided boss would be enough...
  • 2 0
 I don't think the technology is going to make that big of an impact on the standings, but of course we'll just have to see.
  • 2 0
 Good god!
  • 1 0
 I know, All this time we were joking about them coming out with electronic suspension, they were completely serious about it!
  • 3 0
 Oh no! My fork ran out of battery! Anyone have a charging cable?
  • 2 0
 Absolutely love fox! Super stolked on this coming out soon can't wait to pick one up!
  • 1 0
 that looks sick!! i was hoping that it would be the inverted one that they announce last year Frown
  • 2 2
 Justin Leov was saying that Aaron Gwin was taking around 7 seconds off his runs with these forks. I wana see kashima cartridges
  • 1 0
 Perhaps those bosses they are simply an injection port for lube in the dust seal? Location looks perfect for that.
  • 1 0
 what are the two holes (seem threaded) in the arch for? They look freshly made.
  • 1 1
 mud guard mounts perhaps?
  • 1 2
 They are grease ports so you can grease the seals with ease. A few old forks had it but it never really caught on.
  • 1 0
 i'm pretty sure he's talking about the threaded holes in the ARCH !!
  • 1 0
 question: why is fox putting these forks on teams scott, lapierre, trek, etc and not on yeti... as in team fox/yeti?
  • 1 0
 they are riding them
  • 2 0
 I for one would rather see the Inverted fork make it into production.....
  • 1 0
 The bosses could be to insert fox fluid into the foam rings. At least i would like to have that option on my 180 van.
  • 2 0
 Lets have bets on the RRP. Im saying they will break the £2500 mark.
  • 2 0
 ive never thought of the lowers as the "sliders"
  • 2 1
 "Fox 40 RAD" Such an appropriate name lol
  • 1 0
 and i just bought the 2012 fox 40....
  • 1 0
 so glad i am waiting to upgrade my 2010 40's!!
  • 1 0
 peat wears the royal kit, minaar wears oneal
  • 1 3
 I'm willing to bet those bosses are for a fender or mud flap of some sort look on the back of the crown there is 2 little drilled silver holes in line with them. Custom fit carbon fender kinda like the v10's?
  • 1 0
 would be awesome if they fit the spz demos...
  • 1 0
 yay 'retrofittable' to previous 40 forks Big Grin
  • 4 3
 soooooo RAD-ICAL!
  • 1 0
 Last photo: Minnaar?
  • 1 0
 And Bryceland.
  • 1 0
 Peat and Bryceland
  • 1 0
 pretty sure its peaty and bryceland..
  • 1 0
 Peaty, unless Minnaar gained weight. PB detectives never fail. RC.
  • 1 0
 you callin' PEAT FAT.
  • 1 0
 HAHA! No,' LARGE.' Ya can't make the big guy small. Minnaar is fitter than I have ever seen him. He wants it this year
  • 1 0
 ouuu pretty Smile
  • 1 0
 Is slimmer better?
  • 1 2
 Oh WOW they use MANITOU MICROLUBE TECHNOLOGY!!! Its the nineties all over again... then again that'll probably work great
  • 1 0
 Gimme! Gimme!
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