I have the same fork as a 29er. These two things helped my fork a lot

1. Burnishing the bushings for less friction. I made a tool to do 40.09mm
2. Putting in the 2021 spec air piston assembly. ~$90 from a bike shop in the US.

I'd do these things before even touching the damper.

@JohnnyC7 said that rider feedback on the new air spring was very positive on another DH fork thread.

I want to try messing with the damper too. I want faster rebound mostly.

I know it's shimmed rebound and compression, so it should be possible to add/remove shims to tune just like (or better than) grip 2. Problem is that fox sometimes uses custom size shims.

 

Thanks for the insight.

So you changed the air spring and felt a good change ? Sounds interesting but trying to figure out how much can that affect the way the fork is damping but noted .

As for custom shims, I contacted two decent suspension tuners in Europe and both said that not much can be done for the Grip 1 in terms in custom valving. Maybe I'm missing something ? As I don't want to play with it , just set and forget, but just make it work better for small chatter that's killing hands on park ridding.

 

Thanks for the insight.

So you changed the air spring and felt a good change ? Sounds interesting but trying to figure out how much can that affect the way the fork is damping but noted .

As for custom shims, I contacted two decent suspension tuners in Europe and both said that not much can be done for the Grip 1 in terms in custom valving. Maybe I'm missing something ? As I don't want to play with it , just set and forget, but just make it work better for small chatter that's killing hands on park ridding.

Yes the airspring feels better, nothing major, but a definite improvement. Kinda like running 1psi less in your tires.

I'd try 220mm rotors if you have steep trails, my arms hurt when I drag brakes too much.

To see if you need your bushings sized, take everything out of your fork (incl wiper seals). The uppers should drop into the lowers under their own weight. If they can't do this, the harshness you feel isn't the damper, it's friction

I was wrong, it's 6mm on the base valve and 7mm ID shims on the midvalve. Plenty of shims to play with 40mm Part Information | Bike Help Center | FOX

Maybe any improvements would cost as much as a better damper so no one bothers.

IMO most peoples problems with forks aren't the dampers. Better air springs and lower friction are really noticeable and are cheap to fix

 

Maybe any improvements would cost as much as a better damper so no one bothers.

 

The biggest change you're feeling from MY20 to MY21 GRIP is the 2? shims they took from the mid-valve.

 

That's between grip 2 dampers but I'm talking here GRIP 1 and GRIP 2. I've tested two bikes (both MY2020) one with GRIP 1 and one with GRIP 2 and the difference is very noticable

 

Regarding the 2021 air spring…is that a drop-in to for the 2019 fox 40s? If so, that’s an interesting option.

 

Regarding the 2021 air spring…is that a drop-in to for the 2019 fox 40s? If so, that's an interesting option.

yes it is

 

Not sure if it's worth noting but I've sent my fork for a tune at an German guy and it's massively better since.

 

Do you know what he did to the damper?

 

I found a Fox explanation somewhere which said E-bike tunes had softer compression to prevent fatigue on longer rides.

Which makes perfect sense for touring sort of riding.

 

Not sure to be honest, but changed something within the shim stack and the valve. I believe this from the parts he returned back with the fork.

 

Who was the tuner you used? I have same fork and want to tune the grip 1 damper.

 

Hi,
let me share my experience on grip 1 tuning.
I have fox 34 SC 2022 with grip 1 damper remote; air side at 60psi with no volume spacers; 120mm of travel. Rebound fully open. My weight is lowish at 64kg and do not make jumps or big drops.
Stock: feels harsh and rebound is too slow. Remote lock is stone hard. Not able to use more than 80% of travel; sag at 25%
1st tune:

• base valve from valve face: 8x6x0.1 + 2x 13.6x6x0.1 + 12x6x0.1 + 8x6x0.1; (stock was 4x 13.6x6x0.1)
• mid valve: changed the thickness from 0.15 to 0.1mm (this is more than 3 times stifness reduction). I cannot tell the isulated effect from this change, but it alligns (and extrapolates) with the overall trend at fox fork to reduce the midvalve shim stifness.
• rebound: stock was 5x0.15; changed to 17.25x6x0.15 (face) + 8x6x0.1 + 2x 17.25x6x0.15. Note this stack is now progressive; the target is to have fast recovery from small bumps, but to prevet fast recoil after drops. I am not sure whether the face shim touches the progression shim stack.
• reclocked the remote dial by 35° in open direction to acheieve less LSC
• rebound was open at 12clicks from closed (almost fully open). Now, rebound needle adjuster has small effect becasue face shim opens quite easily and provides low resistance oil path.

This tune is much better than the stock - much less harshness, rebound is about right. I can use about 80% of the travel. (I realize air spring progression is too much for me, but no spacers to remove). I tried to reclock the remote dial by ~120° - the LSC was too low and fork was oscilating a lot, while not helping with bigger hits.

2nd tune:

• base valve from valve face: 8x6x0.1 + 13.6x6x0.1 + 12x6x0.1 + 2x 8x6x0.1 (removed one more 13.6shim). The different diamter of the two shims helps distribute elastic energy in larger volume and decrease stress peaks, and increase fatigue life. I would have choosen lower shim thicknesses to increase fatigue life, but such are not available.
• reclocked the remote dial by 35° in open direction to acheieve less LSC (same as tune 1)
• increased pressure to 62psi to imporve mid stroke support

Going through rough rock garden is definetly smoother, due to the decreased HSC from the base shim. Lock is not rock solid due to the lower base shim stack stifness, but OK for my weight. Now I am able to use 90% of travel. I tried running the fork without reclocking the compression dial, but LSC seems to be too much and the fork felt harsh on small bumps, which were not able to bent the base shim stack.

future tunes:

• add carbon air insert like carbon air. This is expected to reduce progression and reduce adiabatic stiffening from the air spring.
• base valve: move one of the 8mm spacer shims to the face of the valve. This would mitigate the need to reclock the compression dial afterwards. The expected effect is equal to 36° reclocking. (this change will not allow me to have more LSC by reclocking, if needed)
• decrease the stifness of the rebound stack. Mostly the LSR by changing the shims to the valve face; I may increase the distance to the HSR shims. I plan to use thinner shims of 0.1mm, to increase fatigue life. I still want to keep the rebound needle adjuster quite open to reduce mid valve compression damping as much as possible; this might be chalanging to achieve from one try.
• I may increase the float of the mid valve shim by 0.1mm, but do not have the reasoning to do so - compression is fine now.

I am attaching a schema of the changes. I would be happy if this knowedge sharing helps someone. And do not forget this tune is aiming not aggresive, light riders.

 

I have a 2020 49 grip1 on a DH bike I bought used. I liked the fork so much I bought a 2023 40 grip2 for my kenevo to replace the boxxer.

They are so different and I prefer the 49.
49 0 tokens and 70psi.
40 4 tokens and 90psi.

The seller did say he had the 49 tuned but I have no further details on what was done or by who. Same really as I would send the 40 off for the same treatment.

 

I have a 2020 49 grip1 on a DH bike I bought used. I liked the fork so much I bought a 2023 40 grip2 for my kenevo to replace the boxxer.

They are so different and I prefer the 49.
49 0 tokens and 70psi.
40 4 tokens and 90psi.

The seller did say he had the 49 tuned but I have no further details on what was done or by who. Same really as I would send the 40 off for the same treatment.

GRIP1 has very little compression damping open and gets really firm as you close it, GRIP2VVC has more compression when fully open but not much when closed.
They are both harsh on sharp edges. Both need modifications to tune up properly.

Stock GRIP feels better riding sedately but gets out of control ridden faster.
Stock GRIP2VVC feels harsher ridden sedately and has a bit more control ridden faster. The HSR/LSR rebound gets most people lost.

 

Made a test with the setup, I described a few posts above. I closed the rebound needle. This has little effect on rebound, as the HSR is low due to the changed shim stack. But, the LSC increased significantly, adding harshness even on small bumps. I start to think the helical spring on the midvalve has too much preload.

 

There's no way to swap the valving between the Grip2 36 and the Grip1 40 right? I assume the damper shaft & top cap sizing are different.
I ask this as the owner of a Grip1 40.

 

The midvalve really needs more stroke.

I found this old post from @Dougal . Does it still holds true? How much additional stroke is needed (ballpark value)?

 

I opened my grip1 revound assembly. Surprysiling, the valve is not plastic, but metal (maybe metal injection molding). Pushing the midvalve seems it has no hardstop machines in the shaft, but it's travel is limited only by the solid height of the spring. Still not sure, had to pay more attention when it was dissasembled. Anyway I added a copper ring between the valve on the shaft at OD 6mm to raise the valve position and increas the midvalve stroke by 0.2mm. First ride impression is the fork fells much better when going thrugh rockgardens; most noticebly isolating you from high speed impacts.

 

I opened my grip1 revound assembly. Surprysiling, the valve is not plastic, but metal (maybe metal injection molding). Pushing the midvalve seems it has no hardstop machines in the shaft, but it's travel is limited only by the solid height of the spring. Still not sure, had to pay more attention when it was dissasembled. Anyway I added a copper ring between the valve on the shaft at OD 6mm to raise the valve position and increas the midvalve stroke by 0.2mm. First ride impression is the fork fells much better when going thrugh rockgardens; most noticebly isolating you from high speed impacts.
View attachment 2091826 View attachment 2091831

So you increase the float of your midvalve, I did the opposite but used a 0.1mm thick shim instead of default 0.15mm, resulting in more lsc, less hsc and faster response, not letting any hits go undamped and it feels awesome everywhere. Fox is doing the exact same thing for their new grip x2 and also grip2 2024 tune, but I have even less float than 2024 tune.

 

To clarify, I already have changed the mid valve from 17.35x0.15 to 16.6x0.10 to decrease HSC. The last change increased the float by 0.2mm. I am 66kg and aim for less damping.
In one post Dougal clearly says "The midvalve really needs more stroke." (see few posts above for link). I guess, the increase in midvalve stroke, imporves the choking issue. I followed his advice and I am happy with the results.
p.s. On the next service will try to see/measure what is the actual float.

 

The float is 0,35mm stock, so now you have 0,4mm + if you increase it by some other spacers you have 0,6mm.. stroke doesnt mean float.. the midvalve doesnt have enough room to bend open, actually with more float it gives more hsc because of how the shim bends when it collides with the bolt.. I really suggest you to try less float, but first you would need a proper functioning basevalve to go with it. I have sanded my basevalve piston flat and drilled the basevalve bolt to have a real lsc bleed adjuster. Then I put enough spacers to have 6x8mm clamp with 3x 13,6mm shims, its perfect for 75-85kg rider. For your weight I would use only 2x 13,6mm shims.

 

I agree, I should have 0.6mm float, as described.
I cannot understand how the midvalve shim could collide with the bolt, during bending - kindly, could you sketch it?

My basevalve is modified by using (piston side)2x 8x6x0.1 + 2x13.6x6x0.1 + 1x 8x6x0.1. I am using remote lock, which provides very little verical movement (rotation range is about 90°), compared to non remote lever (rotation range ~270°). I need the two 8mm face shims to set the hardstop of the adjuster. The locked position is not hard solid, but enough for me. In open mode LSC is adequate. I agree with you 2x13.6 provides good basevalve damping. I can fine tune the bleed in the different modes, by reclocking the adjuster knob and wire fixation point. So far the two 8mm spacers are OK. It is quite strange why FOX designed the remote and non-remote versions with such big difference in tunability range.
So, you have basically converted the shim preload adjuster to LSC bleed adjuster?

 

I could but I won't. I have already told you too much. I have simulator data on how it collides, but it's not my data. It collides because there is a huge flow and the shim bends a lot.

It's completely different damping on basevalve when you are still using perimeter piston instead of 4 port when piston is sanded flat. Yes my adjuster is now lsc bleed adjuster.

 

I could but I won't. I have already told you too much. I have simulator data on how it collides, but it's not my data. It collides because there is a huge flow and the shim bends a lot.

It's completely different damping on basevalve when you are still using perimeter piston instead of 4 port when piston is sanded flat. Yes my adjuster is now lsc bleed adjuster.

I was thinking on the risk of midvalve shim colliding the piston. I try to make rough estimation of the shim bending. Assuming:

• my weight is 650N (65kg);
• half of the weight is transfered to fork;
• the peak spring force is about 3 times the sage spring force;
• peak damping force is same as peak spring force;
• midvalvel shim produces half of the damping force (other half beeing basevalve and midvalve orifice damping)

650 / 2 * 3 / 2 = 487.5N should be produced from the midvalve shim bending.
I made an FEA model of a shim 16.6 x 7 x 0.1 (I use a little smaller OD than stock). The shim is supported on the inner edge and normal pressure is applied to produce the desired reaction of 487.5N.

The shim bends about 0.93mm at the OD. I don't see any collision risk. Here is an overlay:

Doubling the weight and hence the displacement might create a risk of collision with the flange. However, rider with such weight (65*2=130kg) will choose much stiffer midvalve, that will reduce shim displacement.
Looking forward your comments.

 

Thank you for the input!
Let me try to summarize the effects happening on the mid-valve:

Low shaft speeds
The stock float of 0.35mm is consumed, providing very little (insufficient) damping. During the shim float, the damping isn't consistent and spike can be seen (in simulation). Is the inconsistency due to rotation of the shim (tilting the shim left/right)?
The improvement is to reduce the float. Practical way is to add spacer shims below the main shim.
Is there a way to improve the inconsistency?

High shaft speeds
The float is consumed, the shim bends so much it collides with the bolt. Oil flow gets restricted producing too high HSC. Thinner shim will reduce the HSC to certain extend. How can the HSC be reduced after the shim colision with the bolt?

Very high shaft speeds
The float is consumed, the shim bends so much it collides with the bolt, the piston ports are not large enough to allow enough oil flow. Chocking happens, damping is too high.
How can this HSC be reduced?

 

For hsc reduction after shim has bent maximum you can use lower viscosity oil. For lsc from mid valve it's a lot about faster response. That's why less float is better, also for providing more actual lsc. To reduce all float there would need to be more ifp pressure aka preloaded ifp spring. For inconsistency I mean that the damping isn't linear or digressive but becomes very progressive at parts of the curve, those translate into spikes for fast hits.

 

Interesting, although it's a different damper, Ch2.1 RC2, when I tune one, I'm aiming for complete opposite - to increase the float, lower the damping on mid valve and do as much of damping on base valve as possible.

 

You make me wondering. Beofre last service, I ran 0.1mm mid valve shim with 0.4mm float.
Now I changed to 0.1mm mid valve shim with 0.6mm float. I am quite happy of the change - the fork feels very reactive and plush on rough terrain. It might be due to the service of lowers / airspring.

 

When the damper reacts with delay it means it feels plush on single hit but it makes it go too deep on multiple hits to recover fast enough and it will reach the hard section of the spring too soon.

 

I use a custom rebound stack with two stages. The LSR is only one shim 0.15mm, followed by 0.2mm gap and 2 * 0.15mm for HSR. The idea I had is to recover as fast as possible at small velocities, like in the case you described. I even think to reduce LSR further on next service (17.35x0.1 + 13.60x0.1).

 

I was wondering the same. To be more precise here is the change I recently made on the rebound of GRIP:

Before the change I rode with ~10clicks from open, now with~6clicks it has the same rebound. I test the rebound by compressing at ~40% and rapidly release the front wheel to check for wheel lift.
I actually tend to ride the new setup with ~10clicks as well and feels OK.
The addition of the 12mm shim clearly reduced rebound damping. Next change will be with two 8x0.1 shims.

p.s. Pike manual from 2014-2017 has light rebound tune, where 0.2mm cross over is set. Though it is different architecture.

p.s. What is "Grip damper IRL"?

 

If you want, I can check your rebound tune behavior in ReStackor, I just need the piston geometry or at least some high quality photo of it. Send me PM for more info if you re interested.

p.s. What is "Grip damper IRL"?

Sorry, I just meant that I never saw Grip damper In Real Life

 

^ There are so many things wrong in this, or I just dont understand what you are calculating. Where in your calculations you are using the 10mm shaft displacing oil for the basevalve and 20mm piston and its ports flowing through 3 ports (not a perimeter piston like you seem to have calculated, force being applied to whole perimeter of the shim, it bends in 3 spots and you cant really calculate it that simple..
Here is the actual simulation for the default grip 1 midvalve shim lift(its with a 0.15mm shim which is over 3 times as stiff as 0.1mm shim):