How Fox Did High-Speed Rebound AdjustmentA fork's high-speed rebound setting has a big say in how your bike reacts when your hitting things hard and fast, but it also plays a part in where the fork will sit in its travel while you're rolling (spring rate determines static ride height). My testing of the GRIP2 damper at the two extremes showed nearly a full inch difference in ride height, which I wouldn't have believed if I didn't see it with my own eyes. More on that later, though.
The anodized orange part is your rebound piston, but it gets weird from there. See that dark gray disk? The high-speed rebound shims rest between it and the piston, and the VVC system adjusts how they react.
It turns out that Lindsley was already adjusting high-speed rebound internally for of many of Fox's athletes: ''When you valve a fork for everybody, most forks are kinda over-valved for a lot of people, so you have this big range with the orifice adjuster. But if someone wants to improve their performance, the first thing I do is go in there and pull a valve or two off if they're lighter, and maybe add one if they're heavier, but that's pretty rare.
''Then it became really important and I was doing that for all those riders, and it worked really well for them, but wouldn't it be nice to be able to do that without having to take the fork or damper apart? So we wanted to do high- and low-speed rebound, but that adds complication. But the reality now is that, with a few clicks, I can basically get the rebound as close as perfect as you can without having to take the fork apart.''
It wasn't that simple, of course, and the 'but' in this one comes down to real estate. As you might expect, simply adding in another external adjustment isn't an easy task, especially when you need to cram it in there without adding more length or width to the whole thing. Don't forget that every single gram counts as well.
High-Speed Rebound VS Low-Speed Rebound
The obvious question is, of course, why the hell would a rider want yet another dial to turn? And what does high-speed rebound even do?
First, always remember that when we're talking about speed, we're talking about damper shaft speed, not your literal speed. That part is important. You could be riding slowly and get a high-speed compression from a big drop with a flat landing that would compress your suspension quickly, and Fox wanted a dial to control the resulting rebound speed from those type of hits, AKA high-speed rebound. But if that drop had a steep landing that eases your transition from being in the air to being on the ground, your suspension is going to compress relatively slowly, making for a low-speed compression and low-speed rebound control. There's a dial for that, too, but that's old news.
The silver part with the pinch clamp is actually the center bolt, and it's attached like that so it can be as small as possible. That silver tong sticking straight up (there's one opposite it, too) is the leaf spring. When you turn the adjuster, the wings on the leaf spring rotate around the spiral that's on the face of the dark-colored disc to change the leverage applied to it.
Traditionally, high-speed rebound adjustment was done via preloading that valve, but that can cause the orifice to choke up, Lindsley explained, and then more force is required to open those preloaded shims. ''You get this in-between shitty point and then finally the valves crack open. It does work, but it's not ideal,'' he went on to describe. For the record, this layout is what's used in many dampers.
It's all about that real estate. ''You're really constrained with the size because there's not a lot of room in there to do stuff, as far as diameter goes. And we wanted to keep the relationship between the center bolt [commonly known as the piston bolt] that holds everything together and the outside [diameter] of the valves. We want as much distance as we can there because that allows the valves to flex more.'' I'm a visual learner, so I pictured a frisbee (the valves) sitting dead center and face up on top of a skinny pole (the small center bolt) - you'd be able to easily flex the frisbee over the pole if you pushed down on it. Now picture the same frisbee on top of a larger diameter pole that covers nearly all of its footprint - it'd be much more difficult to flex.
The patent-pending VVC system sits at the bottom of the GRIP2 cartridge, and while it's actually pretty simple, the small packaging is a clever solution.
They needed a way to provide external high-speed rebound adjustment but had next to no room, didn't want to use an existing and, in their opinion, compromised system, and also wanted to let the valves flex as much as they needed to.
''This is something that Damon and Bill Brown, the Head of Engineering, came up with,'' Lindsley said while holding up Fox's Variable Valve Control (VVC) adjustable high-speed rebound system, otherwise known as The Answer. At first glance, the rebound piston looks a lot like, well, a rebound piston, but then you notice that funny looking center bolt that I just mentioned. And then the dark-colored plate that's between that and the high-speed rebound shims. And then there's the even stranger leaf spring thingy. What's going on in there?
Here's how VVC works: The dark brown disc the looks like a piston with a bunch of tiny holes in it isn't a piston at all, but rather the face for that double-ended leaf spring. On that face is a raised spiral that's been machined into the top of it, with each end of the tiny leaf spring resting on it.
When you turn the adjuster, the wings on the leaf spring rotate around that spiral to change the leverage applied to it. When you're in the softest high-speed rebound setting (least amount of rebound), the ends of the leaf spring are contacting the outside of the disc where the spiral is farther away and pushes on the outer end of the springs to provide more leverage on the disc. More leverage makes it easier to move the disc. Turning the knob clockwise to add high-speed rebound damping rotates the spring so that the ends contact the spiral closer to the center, meaning they're both shorter leverage arms and more force is required to get the valves to open, and therefore you have more damping. Pretty clever and very compact.
''It's not preloading the leaf spring, it's just changing the fulcrum point,'' Jordan underlined for me. ''So, instead of pushing on the leaf spring from the outside where it has the most leverage and is really easy to flex, it moves the fulcrum point closer to the middle, effectively making it stiffer.'' The key thing to remember is that a shorter lever, aka the leaf spring, means more damping and vice versa. Lindsley said that the dark colored disc that rides on the leaf spring will move evenly, and there's still a valve stack in there, albeit a fair bit lighter than it would be otherwise.
You've got four knobs to play with on your GRIP2 fork, and Fox includes recommended starting points not just for air pressure, but for damper setting relative to your spring rate.
Fox isn't the first to do adjustable high-speed rebound on a fork - Marzocchi had it years ago - but they were going for a more usable, more tuneable system that provides a nice, linear line on the dyno without any funny spikes. Marzocchi's wasn't as effective, they say, largely due to due there being barely any room from the outside diameter of the bolt to the outside diameter of the valve, so they couldn't get the flex that Fox wanted.
Eeesh, that's a buttload of tech to swallow, and we can talk about valves, piston bolts, and doodads all day long, but it doesn't matter if it makes no difference on the trail. So let's find out if this extra knob on Fox's new GRIP2 damper makes a difference in the real world.
Ended up fixing the issue by putting 35ml oil in the air spring to make it ramp up and running LSC almost all the way on (no difference between clicks up until the last 2 clicks anyway).
Just recently serviced the fork, bled the damper and put Enduro seals on. Had to run more psi as was getting 5% more sag with the reduced friction of the better seals, 2 clicks less rebound damping with the correct weight oil in them and finally a useable LSC dial, forks must have had something like 5wt or lower damping oil from factory the whole time along with the shitty seals.
Have ridden these new Fox 36 forks and they are in a league of their own performance-wise, such a nice feel to them.
Came here just for that comment and what do you know, its at the top of the list
At the current moment it's feeling as good as any air fork I've used. We'll see how long that lasts...
It's understandable that Fox and Rockshox get the most attention, being the largest most popular companies. However, not covering X-Fusion, Manitou, DVO, BOS, etc. enforces the status quo and prevents the big two from feeling pressure to truly innovate and lower prices.
We've also reviewed the DVO Emerald and Diamond, along with the X-Fusion Trace and Sweep. We're not trying to ignore anybody - if there's new, relevant technology out there we try to cover it.
Fox and RockShox happen to be the largest two players in the suspension market at the moment, which means that there are many, many riders out there on their products - it makes sense to open one up and provide a little more insight as to what's going on inside.
Even though the quality of your reviews is going up, we are seeing more comments suggesting the review is nothing more than a commercial plug for your ‘biggest’ sponsor/fincial contributors.
An element of this is sociatal...people are getting pissed with there fun space being monetised (maybe they should pay?). But can we believe that reviews and product discussions are impartial?
I’m wittering...but hopefully you get my point?
Here, Levy reports the high speed rebound to have a huge effect on ride height and quality.
Is that down to the difference between fork and rear damper (both reacting differently to HSR, no linkage involved at the front end) or did I miss something else?
Care to comment @VorsprungSuspension ?
The setup method mentioned in that Tuesday Tune video was for the sake of simplification and getting a decent usable setup from the X2. It isn't the only viable method of finding a good setup, nor will everyone out there necessarily prefer the result it'll give you - it just helps minimise confusion caused by the amount of crosstalk between the HSR and LSR adjusters on that particular shock, without doing anything dumb, dangerous or unpredictable.
Would the compression circuit benefit from something similar?
Keep up the good work, hope there will be more Tuesday Tune eps sometime!
Honestly, all this advancement in Grip2 means nothing to me when I have my ride ruined by a snap-crackle-pop I can feel in my grips.
I would pay $500 more for a fork that weighed 1lb more if I could get a guarantee it wouldn't creak.
So @foxfactory whats the plan?
I know its crazy to assume someone would ride a high end suspension fork for more than two years though.
After 4 CSU's you just gotta sell the fork and start over.
@yetikid Yup totally. Gotta have it serviced to get the CSU replaced. No guarantee it wont start creaking again in 8 weeks depending how and what you ride.
I had one creaky fork (not Fox) and it worked like a charm.
Not sure why @foxfactory isn’t working harder on this it must cost them a fortune.
I have a buddy who’s been through 3 I’m less than a year. Sometimes only lasting weeks. So Godamn ridiculous.
I’m ready to ditch Fox in favour of RockShox despite their superior performance. The customer service BS just isn’t worth it!
From my experience the creaking / crackling sensation is most felt while in big compression's, or when hard on the front brake. Its an awful, ride ruining feeling tht can be heard / felt in the grips. Mine currently feels like something is cracking or about to snap off.
Nothing worse than your 1600$ suspension fork feeling like a loose shopping cart.
High-speed-rebound is extremely important especially regarding the fork, compared to the rear shock. When the HSR is too slow to return as Levy discussed, you end up "packing up" through chundery repetitive hits. In other words, the first root you may hit feels fine, but as the tire moves closer up to the next obstacle, if the front tire did not shoot back down to the ground fast enough, your fork is already sitting deeper in the stiffer zone of the travel, and ALL the next quick hits after the first are going to feel STIFF. Same cycle over and over...
The adjustable part of this is important as Levy notes, as a pro 200+lb rider may have 120psi in the fork, and a pro 130lb rider may have 70psi in the fork. Both riders need the fork to shoot back to the ground at the same speed. If the HSR is not adjustable and both riders are on the same fork tune, the 200+ lb pro may have a perfect/fast rebound speed, and the 130lb pro might be stuck with a fork that won't rebound/extend fast enough.
The new Marzocchi Z1 is a close match but uses the heavier 6000 series chassis. As much as it is nice to have the additional adjustments the ability to use the compression sweep of the 3 way 36 Performance Grip fork is perfect before a big climb or to open it wide open on a long descent. So far the simplicity of the base Grip fork has far outweighed the fork tuning I used to look for. Moral of the story is buy the Bomber Z1 fork and just ride unless you are a knob grabber it's the best value/performance fork out there right now in the AM/Enduro space.
The obvious competitor to the 36 Grip2 isn't the PIke.... Why not a comparison to the new RC2 Lyrik???
regards,
Pinkbike Forum
You didn't have the metric system fed to you in school like the Canadian kids did.
He didn't actually say meters though.
Just Saying.
Bottom line, if I had a creaking CSU on a test fork (or a test bike), you'd hear about it. But I haven't had this come up on any test (or personal) bikes.
Mike
The big issue is that Fox doesn’t care, or is in denial, because they NEVER have enough spare CSUs (here in BC at least) to be able to cope with the demand for replacements.
I’ve got one bike, so lost riding time for four months last year waiting for a CSU for my 2017 36, bought a 2018 because I was tired of waiting, and have now waited four months again, because the 2018 started creaking after five months. Throughout, Fox and their distributors have been nothing but empty promises. I could give you a list of people who would report the same BS service!
It definitely highlights how the LSC/HSC (or LSR/HSR) function as a team. If your LSC is a bit more closed...it'll overflow earlier on high velocity cycles/hit thus engaging the HSC more often and earlier in the travel. I used to think of them as more separate but thats not the case.
Makes you wonder how good the new Motion Control Damper is by comparison.
They took the tech from the top level WC RC2C Motion Control dampers that were on the Boxxers and what not and stuffed it all in a single turn dial damper system and its proved to be pretty dang good.
But if we are comparing the Motion Control budget damper to the Budget Grip dampers... different ball field
The easiest way I can explain it is the Grip Damper feels as if it is taking care of the terrain and does well managing very rough terrain where as the Motion Control damper felt a little more stiff off the top (lower small bump compliance) and when things got chaotic on the trail it was surviving more than controlling.
I am more than confident there are gonna people on here that can better explain the differences from a technical standpoint than I can, so lets leave it to them haha.
I'm not a flyweight, about 200lbs geared up, ride hard. The fork felt under-damped and divey in the first half of it's travel, though it did feel like butter on small chop. If I turned the compression dial up a few clicks, it felt really harsh when smashing into anything chunky.
Even if I had the compression set all the way open, it would feel fine 99% of the time, but then when pushed really hard it would spike and cause lack of control. That might not sound like much, but it's only that 1% when your fork really matters.
Weirdly, I rarely used that last 15mm of travel, even without bottomless token. On anything rough it would spike instead of smoothly going to the end. Basically blow through the first half of travel, start ramping up quickly, then BAM! it would try to blow your hands off the bar. This is going fast on DHish stuff. Fork felt great on anything low-moderate speed, loamers, etc.
Reading around, this is a known thing, but I think expert riders rarely get on the Lyrik R. Word has it that it's massively over-shimmed on the HSC circuit in order to make the lockout feel like a lockout. Who knows if this is true, but it makes logical sense.
TLDR; Lyrik R is great for intermediate riders, horrible for experts. Higher end Lyriks are fine.
Yari charger rc and revelation charger rc both have a spring backed ifp life the grip damper
So far it has been a great fork. I can confirm it doesn't have the lock out like the charger RC so the compression tune is much more reasonable. I also rode a moco yari, my least favorite fork ever, @thebearden did a great job explaining its issues. The Charger open bath does not have the high speed choking issue and is really smooth on big hits. Also doesn't have the diving issue. I broke my finger on my first big ride so I only have a few short rides, but its a very promising damper! Only negative I experienced is more hand fatigue than I'm used to getting with my 170mm avalanched yari, but without HSBV thats expected. A little less air spring pressure may nearly fix it.
I'd love to see a comparison of the GRIP damper vs the Charger RC respectively on the 34/Rev and 36/Yari.
"A Fox 36 working well is about as newsworthy as anything from the most recent Interbike, so not at all, in other words. We know the 36 is badass."
My 2017 Fox 36 is not badass. It's harsh as hell or it's too soft and blows through travel, without spending a ton of money on a custom damper and tune.
The forecast for 2020 forks is not promising. Sporadic precipitation is predicted that may lead to inconsistent damping and overfilled lowers.
The special "Screaming Orange Select" crop is not likely to be affected but supplies will be limited to select customers in Temecula and Pietermaritzburg.
www.pinkbike.com/forum/listcomments/?threadid=177704
So compared to the c2r2, it's truly refined completely different HSR making the rebound more adjustable is the most noticeable.
But also consider comparing the compression damper as well. the piston is smaller and lighter, the IFP is much simpler and lighter, and only utilizes 1 spring and a smaller seal for less friction.
As an expert on the subject, Marz stole this from Showa/Kaybaya etc moto forks, they used the design in their moto forks and shrunk it for MTB. When fox bought the patents they figured out the marzocchis parts were cheap and worked. but by no means is this the same damper.
Grip is to C2r2 what the Lambo Adventador is to the Countash. The logical progression of refinement and engineering.
So what do we get when we upgrade from the c2r2? Refinement and tuning, I don't have to take my shit apart any more, lighter weight, and even less friction, with the same easy service. AND you get better slipperier more consistent oil (ptfe 5wt vs marz 7.5).
I loved my 380 but I ain't mad, I think it's awesome and the new MARZ stuff is Rad too.
nearly a litre of sloshing about, Rebound adjusted internally, Compression and spring curve adjusted by changing the oil. A Schrader valve on the top of each leg. 10+ years between services.
That was peak suspension. Give me that, in a 29er with 36mm stations and a 20mm bolt through.
Great article and read, these articles are always appreciated. I love seeing and understanding what's going on inside suspension.
The Grip Dampers do not have a change in feel like the RS Charger Dampers can fall victim too over time. Every 6 months on the Charger dampers I'd give them a bleed (time it to do this during a routine lowers service)) and they would go back to feeling super good, but its still an additional service thing to do. This has not been the case with my Grip Damper, it has yet to give me a change in feel at anytime and thats a nice feeling.
I will say, if you get a new fox fork, I suggest getting the oil needed to do lowers on them. My 36 was nearly bone dry on the air shaft side and definitely not the correct amount on damper side.
I have never been a fox suspension guy, but the Grip damper on the 36 has deeply changed my feelings about their products. Cant wait to try out the GRIP 2
Another huge benefit to the easy bleeds is that its easier to make internal adjustments. You dont even need shaft clamps to pull the valves, so a little simple messing around to get the perfect high speed tunes and youre set.
Had a FIT4 for a short time, and then a GRIP. I actually liked the GRIP better. Actually, that Rhythm GRIP fork was the first FOX fork I actually liked. Well, to be fair, the first Fox fork I rode was assembled wrong and had all the lower leg oil in the air chamber, so it was like running 4 tokens or something and would never use more than 2/3 of its travel. Didn't know it until I did a rebuild. It felt great after, but then 27.5 and Boost came out and it was time for a new ride.
Riding a Pike and a Lyrik now, Pike feels better than the Lyrik. But may be swapping a bike again soon, may go back to a GRIP fork.
Marzocchi >Fox
All i want to know is:
How it rides and how often i need to take it apart to keep it decent.