I have always felt that the one part on a motocross bike that most determines how fast I can ride the bike around the track is the front fork, and therefore have always been fascinated with the technical evolution of the modern cartridge fork. Here is a guy with some YouTube videos that provides the best explanation of the evolution and workings of a modern cartridge fork that I have seen;
The difference between Open & Closed cartridge forks | Offroad Engineered - YouTube
How cartridge front forks work | Offroad Engineered - YouTube
He explains how adoption of a closed cartridge system, the addition of a free piston and spring tubes have been the last biggest advancements in the technology of the modern front spring fork.
Not much has advanced in fork technology over the last 20 years aside from a few years of manufacturers playing around with air forks. The very latest trend seems to be going backwards a bit on lower tube size with the consensus seeming to be that 48mm is the happy medium. WP still has their 52mm fork although the lowers are made of aluminum. I don't think any pros are running the 51mm works Showa forks anymore, are they? And it seems the biggest Kayaba works forks that factory teams are running are back to the same 48mm tubes found on the oem bikes. It also seems that Showa factory/ A-kit forks are now using cast aluminum axle lugs now instead of CNC as a latest trend.
Anyone aware of any other recent trends in MX fork technology?
As the frames get more rigid the need for bigger forks goes away.
I don't know where forks go from here like you say there hasn't been much advancement in design but a lot goes into the tubes, lugs and other materials.
Advancement in oils is a big one. Oil stability is very important and getting the tolerances lower and removing heat and friction.
I was interested when air forks came back around....then talk of a shock.
Really? Wow. They couldn't make it work in 77 but air properties have changed?
Dungey's shock failure shuttered the notion. Blown spring shocks are one thing, blown air shocks are fatal.
And when you tell me EVERYONE had Fox AIRSHOX......no they didn't(people with money did) and OHLINS and everybody else killed difficult to operate air shocks and forks. The negative effects of heated air were and are still well known. And when you tell me Simons forks were the bomb.....no they weren't as they quickly went away. For obvious reasons. Nitrogen(even now) is Star Wars tech for most folks. So are air pumps and massive pressures.
Making air forks shed 5 pounds quickly. Now, people put heavy internals back in. Around the tree we go. Anything to make a buck.
Short of levitation or anti-gravity whatever, the rest will be about the same.
Way back, folks in the 70's used air to overcome sacking springs. They learned that sacking springs were better than awful air qualities. Everyone just got stiffer springs like S&W. Every factory team shed Fox SHOX.
It's hard to believe how much money is spent on fork and shock valving. Or even performance mods. I always rode a basically stock bike and did relatively well. I became expert and won lot's of races. I would say my success was limited by my courage and having to go to work the next day. My bikes certainly had way more to give.
Whatever happens with the evolution of current suspension theory....it will be more than enough for average racers and really just about everyone.
Perhaps frame rigidity is not the key reason for going away from bigger fork tubes. I believe the principal for the bigger tubes is that as you take bigger hits, they are less likely to bend/ cock in the upper tube bore and bind, with the negative tradeoff of an increased rigid feel. In fact, aluminum frame manufacturers have been incrementally working more flex into their frames since the early 2000's. Now the trend has been to work more flex into the triple clamps to soften the harshness in the front even more. HRC triple clamp evolution on this front started early in 1999/ 2000 as the HRC triple clamps originally had square edges and HRC factory mechanics found that by filing the edges of the clamps, the factory riders would notice a less rigid feel. Then HRC incorporated beveled edges into their machining and that evolved into rounded edges on the HRC clamps as they came from the machine shop. Now the trend is the new split clamp designs to reduce front end rigidity even more. It seems the trend of the 70's, 80's and 90's of going bigger and stiffer on everything has reversed to find more/ just the right amount of flex in frames, fork tubes and clamps. We are at the stage of MX technological evolution of incrementally finessing the existing technology. Ken Roczen has just shown us that you can finish in the top 5 in the ultra-competitive premier class of a pro race on the design of about 15 years ago (the RMZ).
I agree there has been a significant improvement in synthetic oils as well as low friction seals like SKF makes. I have tried them all and maybe there is some very small incremental improvements, but the advent of DLC as a lower tube and shock rod coating is the one change I could easily feel when the track got choppy. (When the track is smooth, you really don't notice the improvements so much.) Nevertheless, these improvements are not related to changes in fork design, they are just helping the current design of the last 1/4 century do their job better.
I am an old guy that raced in the 70's so remember the first experiences with air suspension well. We had few options to tune our spring suspension for weight or ability. There was not an array of spring rates for our forks or shocks or clickers for adjustability. The most we could do is use a heavier oil to increase compression dampening/ rebound dampening, drill holes in the damper rods or shim the springs. In the mid-70's we would cut a piece of 1/2" to 1" tubing and bolt that at the bottom of the damper rod with a longer bolt and that would give us an equivalent amount of increased fork travel at the safety risk of reduced upper/ lower fork tube overlap. Then we drilled our fork caps to install air valves. I thought this was great at first as it allowed some adjustability and could really allow you to hit bigger jumps, but then as time went on, I realized I would lose the feel for my front end in corners.. especially bumpy corners that got progressively worse with each lap as the forks heated up. It was enough to slow your lap times down. I went back to mechanical fork springs and never looked back. Much better front end feel in the corners.
The Fox Air Shox were a different matter. The oem spring shocks of the 70's were so bad on most bikes, that the air shocks worked fairly well compared to the spring shock technology of the time. Even the fastest pros' had them on their factory bikes. I never blew out a Fox Air Shox, but I did blow out a couple of sets of spring shocks in that era. By the early 80's, spring shock technology improved enough that they finally surpassed the Air Shox. Fox already had their own spring shocks anyway, even before the popularity of the Air Shox disappeared.
Watching the video's I attached above, the narrator talks about the pros and cons of the open vs closed cartridge forks. He commented that the open cartridge forks have more air volume and can offer better/ more progressive bottoming resistance at the cost of inconsistent air spring rates as the air volume heats up quickly in motocross. I think he mentioned that the open cartridge fork still makes a lot of sense for dual on/off road bikes.
For the next technological advancement in motocross suspension, I am waiting for the electronics now found on high performance OEM automobiles like the Corvette and the Camaro which have the "magnetic ride control". With these electronics, shock dampening can automatically change with the conditions the shock is experiencing at the moment. I would rather have that than the ability to switch engine maps electronically.
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When I bought my 20 husky 450. I fully expected to buy the kyb kit for the forks . But I was actually amazed at how much I love the air forks . A big thing for me was running wayyy more air than people were suggesting.
Wow!.. thanks for sharing! MTB's already have this and it was Fox suspension that introduced it. I wonder if there is any reason why mx bikes would not feasibly benefit from the same technology. I always dreamed of having a supple suspension where you would not be risking injury for overjumping a big jump (to a point) or worrying about the rear rebounding violently from an untimely hit to the rear wheel w/o risk of being thrown over the bars. Maybe this technology could help achieve that.
1980 was it for AIRSHOX. 1981 single shock systems killed whatever was left. Again if you were rich...you had Fox Shox. Husky was about it for dual shocks....and they had OHLINS.
Around here about 1 in 50 racers, more or less. Just too expensive and difficult to deal with.
I compared the forks on the HRC factory bikes with the current Showa A-Kit suspension offering. The A-kit seems to have CNC billet lugs, but for all I know they could be cast and then CNC'd. The A-kit also has red anodized aluminum for caps. I looked at Sexton's, Roczen's and Gasjer's 2022 suspension. It looks to me that the fork is the same as the 49mm A-kit offering, as well as the same shock. What is different on the factory bike's forks are the different fork caps which are anodized blue on the factory bikes. I had read somewhere that some of the fork internals may be different, but they seem to be using the same tubes and outer coatings as the A-kit. I even heard an HRC mechanic in one video refer to Sexton's forks as "A-kit". The factory riders also seem to have switched out the A-kit CNC lugs for oem cast lugs. I don't think I could feel the difference. I think they did the same for the shock.. same housing/ body as the A-kit, but some of the internals may be different. No more fancy magnesium fork caps, larger fork tubes, or special CNC lugs unique to the full factory forks. What the general public can buy today is getting closer and closer to the full factory stuff.
The Showa 49mm A-Kit forks have forged fork lugs. The photo below is from one of my bike builds. You can see the forging seam running vertically just below the outer pinch bolt. If you get Showa A-Kit from Pro Circuit- those can have CNC lugs that are made locally to Pro Circuit's specs (you can tell by the grey/bronze anodizing).
The last picture above is a cast production lug with black coating- and yes, it seems more pro riding are using those.
I did notice what looked like a casting seam in a couple of pics of the A-kit lugs, but wasn't sure if it was a reflection. Thanks for confirming they are forged castings.
Is that some sort of speedo pickup that is bolted to the disc?
That's a speed sensor- which is "triggering" for the traction control conspiracy theorists
I've never noticed one like that before. Only the magnet style. So it must get triggered by the openings?
ABS
Same ring style as HRC Rally bikes. Magnets collect metal and stop working LoL.
Definitely not ABS- that's the kiss of death on dirt bikes haha.
Has anyone realised that Roczen's fork cap has a two way adjuster? I have seen such designs for a long time. But never got to someone who knew something about it.
It could be either high speed compression damping or spring preload.
Realised they use RC car servo horn as adjusting lever on fork caps on that cropped video photo.
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