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Fox 38 grip 2 custom tuning
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flag dazza1
Posted: Oct 26, 2023 at 13:15 Quote
Im looking to get my fox 38s custom tuned would like some recommendations of what are the best things to do option wise and any companie recommendations im in the uk so would need to be uk company.
A few issues i don't like are the small bump sensitivity isnt the best they also dive a lot in the travel almost like pedal bob a rear shock if that makes sense and it would be nice if they were a bit plusher on the medium size slower hits as whats on one of the local trails i ride its very steep and rooty blown out and rough
I could run less compression but then my forks dive more i could also take out a volume spacer as i rarely use full travel unless i mess up but i was wondering if that would make the diving worse.
Im definitely not an expert rider by any means but progressing every time I ride but i bought the bike because it fox factory suspension with lots of adjustability coming from my old 2013 trek slash i quickly outgrew that suspension particularly the rear shock
Any advice would be great
flag Dougal-SC
Posted: Nov 9, 2023 at 12:36 Quote
dazza1 wrote:
Im looking to get my fox 38s custom tuned would like some recommendations of what are the best things to do option wise and any companie recommendations im in the uk so would need to be uk company.
A few issues i don't like are the small bump sensitivity isnt the best they also dive a lot in the travel almost like pedal bob a rear shock if that makes sense and it would be nice if they were a bit plusher on the medium size slower hits as whats on one of the local trails i ride its very steep and rooty blown out and rough
I could run less compression but then my forks dive more i could also take out a volume spacer as i rarely use full travel unless i mess up but i was wondering if that would make the diving worse.
Im definitely not an expert rider by any means but progressing every time I ride but i bought the bike because it fox factory suspension with lots of adjustability coming from my old 2013 trek slash i quickly outgrew that suspension particularly the rear shock
Any advice would be great

I found this from the front page article. You're completely correct in your observations. The GRIP2VVC damper used in the F38 is harsh and lacks support. The harshness comes from the mid-valve choking. This gets worse the more you close the LSR dial as the LSR ports are a significant oil flow path during compression.
The total compression damping available is low even with HSC and LSC fully closed. But the harshness from the mid-valve choking leads everyone to run compression more open and try to compensate with more air pressure.

To fix it requires significant modifications (i.e. cutting metal and adding new parts). I think I'm the only one worldwide doing this.
flag BCSuspension
Posted: Nov 10, 2023 at 1:39 Quote
dazza1 wrote:
Im looking to get my fox 38s custom tuned would like some recommendations of what are the best things to do option wise and any companie recommendations im in the uk so would need to be uk company.
A few issues i don't like are the small bump sensitivity isnt the best they also dive a lot in the travel almost like pedal bob a rear shock if that makes sense and it would be nice if they were a bit plusher on the medium size slower hits as whats on one of the local trails i ride its very steep and rooty blown out and rough
I could run less compression but then my forks dive more i could also take out a volume spacer as i rarely use full travel unless i mess up but i was wondering if that would make the diving worse.
Im definitely not an expert rider by any means but progressing every time I ride but i bought the bike because it fox factory suspension with lots of adjustability coming from my old 2013 trek slash i quickly outgrew that suspension particularly the rear shock
Any advice would be great

Just to say there are a number of Suspension Service Centre's now working with Fluid Function tuning for Fox and Rockshox Forks in the UK. These have been developed by Fluid Focus in the US and can now be added onto a Full Fork Service by those of us who deal with them.

I will be able to do this service for you in the UK and if you speak to Rick @ Slick and Slide Suspension in Macclesfield he will know what works best as he is the distributor for their products.

It involves a revolving of your Fox Grip2 VVC damping system and will open things up to get the feel that you require. From all reports this is a fantastic upgrade and well worth looking into.

Let me know if I can help further!

Cheers

Ben
flag CSdirt
Posted: Nov 10, 2023 at 7:22 Quote
nah man you don't need a custom tune. Is the tune great, nope, but certainly usable. Here's some advice from someone not trying to sell ya something...

"Divey and harsh" often means not enough air and to many tokens. So, sounds like your setup is not great, no offense. Forks with all the knobs are easier to make shit than good tbh.

Do a lower service (20 min). When you're in there take out all your bottom out tokens. Add more air pressure than you currently run (fox's chart is bad). Maybe set up for 15-18% sag to have a baseline, that's just a baseline and you may end up with less or more per preference. If you bottom out add 1 token and repeat, but if its divey don't add a token but add 2psi instead and repeat. If you dont bottom out remove 2psi at a time and repeat. Get the air spring figured out and then adjust LSC and HSC.

It takes lots of time, shuttle runs or a section of trail you can quickly repeat A LOT.

Problem is most people jam too many tokens in and not enough air pressure. Then they're riding on a divey fork sitting on the ramp up of the air spring....harsh as f*ck. Also, if your rebound LSR and HSR are too slow its gonna make the fork feel even more divey/harsh and keep it sucked down on that spring ramp up.

Anyway hope that helps.
flag Dougal-SC
Posted: Nov 10, 2023 at 22:20 Quote
CSdirt wrote:
nah man you don't need a custom tune. Is the tune great, nope, but certainly usable. Here's some advice from someone not trying to sell ya something...

"Divey and harsh" often means not enough air and to many tokens. So, sounds like your setup is not great, no offense. Forks with all the knobs are easier to make shit than good tbh.

Do a lower service (20 min). When you're in there take out all your bottom out tokens. Add more air pressure than you currently run (fox's chart is bad). Maybe set up for 15-18% sag to have a baseline, that's just a baseline and you may end up with less or more per preference. If you bottom out add 1 token and repeat, but if its divey don't add a token but add 2psi instead and repeat. If you dont bottom out remove 2psi at a time and repeat. Get the air spring figured out and then adjust LSC and HSC.

It takes lots of time, shuttle runs or a section of trail you can quickly repeat A LOT.

Problem is most people jam too many tokens in and not enough air pressure. Then they're riding on a divey fork sitting on the ramp up of the air spring....harsh as f*ck. Also, if your rebound LSR and HSR are too slow its gonna make the fork feel even more divey/harsh and keep it sucked down on that spring ramp up.

Anyway hope that helps.

You can't fix damper problems with air spring changes. You can only compromise setup further in the hope of getting something workable.

When you're changing air pressure by 2psi it means you're juggling. When you're in the middle of a good setup 10psi isn't a problem.

When you fix the damper everything comes together. It requires significant modifications to mid-valve and base-valve and then revalving.
flag CSdirt
Posted: Nov 11, 2023 at 8:59 Quote
Dougal-SC wrote:

You can't fix damper problems with air spring changes. You can only compromise setup further in the hope of getting something workable.

When you're changing air pressure by 2psi it means you're juggling. When you're in the middle of a good setup 10psi isn't a problem.

When you fix the damper everything comes together. It requires significant modifications to mid-valve and base-valve and then revalving.

Eh nah not really. A bad air spring set up with a good damper will still ride like ass. The OP is just wanting something good, not world class. World class is a different discussion. The Fox 38 grip2 is capable of good, but must have proper air spring set up and most users get this wrong. I'm saying start there before investing $

Highly skilled people (perhaps you) can benefit from damper tuning and knob clicks, but most people are going set it up wrong and make it ride even worse. Sure 2psi is potentially too small, but telling someone 10psi might be too large a jump when they dont know what they're doing. Maybe 5psi is a happy medium.
flag Dougal-SC
Posted: Nov 11, 2023 at 11:48 Quote
CSdirt wrote:
Dougal-SC wrote:

You can't fix damper problems with air spring changes. You can only compromise setup further in the hope of getting something workable.

When you're changing air pressure by 2psi it means you're juggling. When you're in the middle of a good setup 10psi isn't a problem.

When you fix the damper everything comes together. It requires significant modifications to mid-valve and base-valve and then revalving.

Eh nah not really. A bad air spring set up with a good damper will still ride like ass. The OP is just wanting something good, not world class. World class is a different discussion. The Fox 38 grip2 is capable of good, but must have proper air spring set up and most users get this wrong. I'm saying start there before investing $

Highly skilled people (perhaps you) can benefit from damper tuning and knob clicks, but most people are going set it up wrong and make it ride even worse. Sure 2psi is potentially too small, but telling someone 10psi might be too large a jump when they dont know what they're doing. Maybe 5psi is a happy medium.

There aren't any examples of excellent dampers with bad air springs though. Because it's far easier to make an air spring work than to make a good damper. The companies that can't make a good spring definitely can't make a good damper.

The fox 36 and 38 air springs stock are good. They can be improved but they aren't the problem.

You cannot get around the grip and grip2 issues with setup. There is no combination of knob twisting that will help. So everyone runs basically no compression damping and over springs them to get by. Especially the racers.
flag EuanBisset145
Posted: Nov 11, 2023 at 14:22 Quote
Dougal-SC wrote:
CSdirt wrote:
Dougal-SC wrote:

You can't fix damper problems with air spring changes. You can only compromise setup further in the hope of getting something workable.

When you're changing air pressure by 2psi it means you're juggling. When you're in the middle of a good setup 10psi isn't a problem.

When you fix the damper everything comes together. It requires significant modifications to mid-valve and base-valve and then revalving.

Eh nah not really. A bad air spring set up with a good damper will still ride like ass. The OP is just wanting something good, not world class. World class is a different discussion. The Fox 38 grip2 is capable of good, but must have proper air spring set up and most users get this wrong. I'm saying start there before investing $

Highly skilled people (perhaps you) can benefit from damper tuning and knob clicks, but most people are going set it up wrong and make it ride even worse. Sure 2psi is potentially too small, but telling someone 10psi might be too large a jump when they dont know what they're doing. Maybe 5psi is a happy medium.

There aren't any examples of excellent dampers with bad air springs though. Because it's far easier to make an air spring work than to make a good damper. The companies that can't make a good spring definitely can't make a good damper.

The fox 36 and 38 air springs stock are good. They can be improved but they aren't the problem.

You cannot get around the grip and grip2 issues with setup. There is no combination of knob twisting that will help. So everyone runs basically no compression damping and overs prings them to get by. Especially the racers.

I'm in the same trade (motocross/enduro) and I agree when it comes to MTB suspension. You can't fix a damper problem using the spring side, it simply doesn't work and it can be seen on some of the best World Cup rider's bikes. Suspension that doesn't offer much in the way of traction or movement over small bumps and then dives almost uncontrolled when hitting holes, braking bumps, or other similar choppy bumps.

The base valve adjuster/ adjusters can't compensate for the lack of a good mid valve and even if the rebound is closed a simple check valve allows far too much flow for it to make a meaningful difference to compression.

In your explanation, you talk about the mid valve choking whilst simultaneously saying there is very little damping overall. if we compare a Manitou Dorado mid-valve piston and damper tube (15.8 i.d) versus a basic fox grip mid-valve and tube (20 i.d). With the manitou roughly 2/3s the volume of oil has to pass through the mid valve in the same distance traveled at a given velocity as a fox grip damper, ignoring the base valve. This is where the size of pistons ports/mid valve comp stack and float come into play, the dorado(36mm pro) ports are miniscule in comparison to the Fox ones and Mezzers aren't much different; if the Fox ones choke it would suggest Manitous will choke sooner even when considering that they are dealing with a lesser volume of oil.

If it was choking then to have very little damping the oil would have to be blowing through/by passing the base valve stack almost unhindered.

I'd be interested to see these dyno charts that show the mid valve choking on fox forks and what you class as choking?

For the record, I have been playing around with grip dampers and did have to modify the mid-valve to do what I wanted but it wasn't as drastic as you describe.

Euan
flag Dougal-SC
Posted: Nov 11, 2023 at 17:08 Quote
EuanBisset145 wrote:
Dougal-SC wrote:
CSdirt wrote:


Eh nah not really. A bad air spring set up with a good damper will still ride like ass. The OP is just wanting something good, not world class. World class is a different discussion. The Fox 38 grip2 is capable of good, but must have proper air spring set up and most users get this wrong. I'm saying start there before investing $

Highly skilled people (perhaps you) can benefit from damper tuning and knob clicks, but most people are going set it up wrong and make it ride even worse. Sure 2psi is potentially too small, but telling someone 10psi might be too large a jump when they dont know what they're doing. Maybe 5psi is a happy medium.

There aren't any examples of excellent dampers with bad air springs though. Because it's far easier to make an air spring work than to make a good damper. The companies that can't make a good spring definitely can't make a good damper.

The fox 36 and 38 air springs stock are good. They can be improved but they aren't the problem.

You cannot get around the grip and grip2 issues with setup. There is no combination of knob twisting that will help. So everyone runs basically no compression damping and overs prings them to get by. Especially the racers.

I'm in the same trade (motocross/enduro) and I agree when it comes to MTB suspension. You can't fix a damper problem using the spring side, it simply doesn't work and it can be seen on some of the best World Cup rider's bikes. Suspension that doesn't offer much in the way of traction or movement over small bumps and then dives almost uncontrolled when hitting holes, braking bumps, or other similar choppy bumps.

The base valve adjuster/ adjusters can't compensate for the lack of a good mid valve and even if the rebound is closed a simple check valve allows far too much flow for it to make a meaningful difference to compression.

In your explanation, you talk about the mid valve choking whilst simultaneously saying there is very little damping overall. if we compare a Manitou Dorado mid-valve piston and damper tube (15.8 i.d) versus a basic fox grip mid-valve and tube (20 i.d). With the manitou roughly 2/3s the volume of oil has to pass through the mid valve in the same distance traveled at a given velocity as a fox grip damper, ignoring the base valve. This is where the size of pistons ports/mid valve comp stack and float come into play, the dorado(36mm pro) ports are miniscule in comparison to the Fox ones and Mezzers aren't much different; if the Fox ones choke it would suggest Manitous will choke sooner even when considering that they are dealing with a lesser volume of oil.

If it was choking then to have very little damping the oil would have to be blowing through/by passing the base valve stack almost unhindered.

I'd be interested to see these dyno charts that show the mid valve choking on fox forks and what you class as choking?

For the record, I have been playing around with grip dampers and did have to modify the mid-valve to do what I wanted but it wasn't as drastic as you describe.

Euan

Yes I modify the 36mm Dorado midvalves too. They're restrictive in a different way to the fox grip/grip2 ones so the feel is different and the fix is quite different too.

Fox got the midvalves right in the fit4 forks but not in the grip/grip2 forks. Tube diameter and oil for volumes are a large part of the problem.

You can't isolate midvalve behaviour in a simple dyno test. It requires comparative testing. I think this is why so many manufacturers get it wrong.
flag EuanBisset145
Posted: Nov 12, 2023 at 2:37 Quote
Dougal-SC wrote:
EuanBisset145 wrote:
Dougal-SC wrote:


There aren't any examples of excellent dampers with bad air springs though. Because it's far easier to make an air spring work than to make a good damper. The companies that can't make a good spring definitely can't make a good damper.

The fox 36 and 38 air springs stock are good. They can be improved but they aren't the problem.

You cannot get around the grip and grip2 issues with setup. There is no combination of knob twisting that will help. So everyone runs basically no compression damping and overs prings them to get by. Especially the racers.

I'm in the same trade (motocross/enduro) and I agree when it comes to MTB suspension. You can't fix a damper problem using the spring side, it simply doesn't work and it can be seen on some of the best World Cup rider's bikes. Suspension that doesn't offer much in the way of traction or movement over small bumps and then dives almost uncontrolled when hitting holes, braking bumps, or other similar choppy bumps.

The base valve adjuster/ adjusters can't compensate for the lack of a good mid valve and even if the rebound is closed a simple check valve allows far too much flow for it to make a meaningful difference to compression.

In your explanation, you talk about the mid valve choking whilst simultaneously saying there is very little damping overall. if we compare a Manitou Dorado mid-valve piston and damper tube (15.8 i.d) versus a basic fox grip mid-valve and tube (20 i.d). With the manitou roughly 2/3s the volume of oil has to pass through the mid valve in the same distance traveled at a given velocity as a fox grip damper, ignoring the base valve. This is where the size of pistons ports/mid valve comp stack and float come into play, the dorado(36mm pro) ports are miniscule in comparison to the Fox ones and Mezzers aren't much different; if the Fox ones choke it would suggest Manitous will choke sooner even when considering that they are dealing with a lesser volume of oil.

If it was choking then to have very little damping the oil would have to be blowing through/by passing the base valve stack almost unhindered.

I'd be interested to see these dyno charts that show the mid valve choking on fox forks and what you class as choking?

For the record, I have been playing around with grip dampers and did have to modify the mid-valve to do what I wanted but it wasn't as drastic as you describe.

Euan

Yes I modify the 36mm Dorado midvalves too. They're restrictive in a different way to the fox grip/grip2 ones so the feel is different and the fix is quite different too.

Fox got the midvalves right in the fit4 forks but not in the grip/grip2 forks. Tube diameter and oil for volumes are a large part of the problem.

You can't isolate midvalve behaviour in a simple dyno test. It requires comparative testing. I think this is why so many manufacturers get it wrong.

Taking into account the symptoms that you describe and that the mid valve compression ports are adequate in size on both the fit 4 and Grip dampers, relative to their respective tube diameters and oil volumes. Both the dorado damper and Fit 4 also have considerably more check valve float than the 0.4mm of the grip, grip 2 with the stock tune is less. The removed material is to increase the amount of float allowing more oil to pass through. I take it you're then modifying and valving the base valve stiffer (massive over simplification) to account for most of the damping?
If that is the case I would say we have a slightly different approach to our tuning.

Of course you can't just isolate a single working part of the damper with the dyno. But it will show up in a force vs velocity graph to a trained eye. I think we both know our Dynos are essentially just a comparative tool, the trick is relating what we read on the screen to how we see/feel the suspension is reacting on the trail. After all our eyes are a dyno of sorts.
flag Dougal-SC
Posted: Nov 12, 2023 at 12:14 Quote
EuanBisset145 wrote:
Taking into account the symptoms that you describe and that the mid valve compression ports are adequate in size on both the fit 4 and Grip dampers, relative to their respective tube diameters and oil volumes. Both the dorado damper and Fit 4 also have considerably more check valve float than the 0.4mm of the grip, grip 2 with the stock tune is less. The removed material is to increase the amount of float allowing more oil to pass through. I take it you're then modifying and valving the base valve stiffer (massive over simplification) to account for most of the damping?
If that is the case I would say we have a slightly different approach to our tuning.

Of course you can't just isolate a single working part of the damper with the dyno. But it will show up in a force vs velocity graph to a trained eye. I think we both know our Dynos are essentially just a comparative tool, the trick is relating what we read on the screen to how we see/feel the suspension is reacting on the trail. After all our eyes are a dyno of sorts.

There are 5 different factors in play with a mid-valve and your mid-valve/base-valve balance depends on a lot of factors too.

The base-valve on the GRIP2VVC uses 4mm ID shims and preloaded VVC fingers on a cup. The shim stack is so soft you can stack 4x the number of shims in there and still not gain any meaningful damping. It's almost all from the preloaded cup and fingers. Which doesn't help the harshness and lack of support.
flag CSdirt
Posted: Nov 13, 2023 at 6:49 Quote
Dougal-SC wrote:

There aren't any examples of excellent dampers with bad air springs though. Because it's far easier to make an air spring work than to make a good damper. The companies that can't make a good spring definitely can't make a good damper.

The fox 36 and 38 air springs stock are good. They can be improved but they aren't the problem.

You cannot get around the grip and grip2 issues with setup. There is no combination of knob twisting that will help. So everyone runs basically no compression damping and over springs them to get by. Especially the racers.

Good discussion,

Totally agree!

Im just trying to save the OP $ and make sure they have tried to make basic setup as good as possible. Its not going to solve the damper issue, but should be ridable for a lot of folks. Tuning these is nearly impossible and a drop in damper is big $$. Its a major bummer Fox put out such a poor compression damping profile on these.
flag EuanBisset145
Posted: Nov 13, 2023 at 11:51 Quote
Dougal-SC wrote:
EuanBisset145 wrote:
Taking into account the symptoms that you describe and that the mid valve compression ports are adequate in size on both the fit 4 and Grip dampers, relative to their respective tube diameters and oil volumes. Both the dorado damper and Fit 4 also have considerably more check valve float than the 0.4mm of the grip, grip 2 with the stock tune is less. The removed material is to increase the amount of float allowing more oil to pass through. I take it you're then modifying and valving the base valve stiffer (massive over simplification) to account for most of the damping?
If that is the case I would say we have a slightly different approach to our tuning.

Of course you can't just isolate a single working part of the damper with the dyno. But it will show up in a force vs velocity graph to a trained eye. I think we both know our Dynos are essentially just a comparative tool, the trick is relating what we read on the screen to how we see/feel the suspension is reacting on the trail. After all our eyes are a dyno of sorts.

There are 5 different factors in play with a mid-valve and your mid-valve/base-valve balance depends on a lot of factors too.

The base-valve on the GRIP2VVC uses 4mm ID shims and preloaded VVC fingers on a cup. The shim stack is so soft you can stack 4x the number of shims in there and still not gain any meaningful damping. It's almost all from the preloaded cup and fingers. Which doesn't help the harshness and lack of support.

If you really want to go down the rabbit hole there's far more than 5 variables effecting how a mid valve needs tuning when you start going from damper to damper.

All of that information is available to anyone on the fox site, so I did a lot of sifting through drawings before opening either damper to see if it was going to be viable working with either the grip or grip 2 dampers to do some testing with a couple of local world cup riders over the off season. I picked the standard grip just because it eliminates the extra complexity involved in having to work around the high speed adjuster setups on the grip 2.

It is quite simple to address the issue of the 4mm shims and go up to 6 or 8mm i.d to get a better selection of different shim thicknesses to make the base valve work as it should within the limited available space. There's a lot that can be done in there to get the performance we're looking for without completely butchering the damper.
flag Dougal-SC
Posted: Nov 13, 2023 at 16:41 Quote
EuanBisset145 wrote:
If you really want to go down the rabbit hole there's far more than 5 variables effecting how a mid valve needs tuning when you start going from damper to damper.

All of that information is available to anyone on the fox site, so I did a lot of sifting through drawings before opening either damper to see if it was going to be viable working with either the grip or grip 2 dampers to do some testing with a couple of local world cup riders over the off season. I picked the standard grip just because it eliminates the extra complexity involved in having to work around the high speed adjuster setups on the grip 2.

It is quite simple to address the issue of the 4mm shims and go up to 6 or 8mm i.d to get a better selection of different shim thicknesses to make the base valve work as it should within the limited available space. There's a lot that can be done in there to get the performance we're looking for without completely butchering the damper.

It's not possible to fix it without surgery. Literally adding and removing metal.

That's why I'm still the only one with the tunig for these sorted.
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