Quantcast

O.K, Kids, What Mods Can Be Done To Improve ‘19 Fox 36?

HardtailHack

used an iron once
Jan 20, 2009
6,930
5,901
Cost Because Flagship?
adjuster shaft inside adjuster shaft on rebound? I can see that being annoying to produce
the non vvc grip 2 base valve is barley more complex.

I was not into the fit 4, bought the latest and greatest grip 2 (pre vvc) and was underwhelmed and went back to an RC2 for the last year, I just put a grip 2 vvc base valve in my grip 2 and put it back into my fork, and im currently experimenting with MOAR SHIMZ and MOAR LEAFZ

What problems were you having specifically?
Id be looking into problems with hub width, bushings, and airspring issues.
I just couldn't make it good at everything and I ended up with a fork that blew through travel or spiked like a spiky thing and I couldn't find an in-between.
I did what I'd normally do and set everything to wide open, get the spring rate about right then add damping.

The Mezzer was supposed to be quite a bit more involved to get feeling right but it was a doddle and it was still acceptable even if you were either side of your desired settings.
If I wasn't getting very close to being unemployed I would have bought another Mezzer as a spare.

Oh, I better add that I am a heavy, a pretty shit rider that has only one bike, a 63deg HA hardtail that is essentially good at nothing.
I've never really owned a decent fork so I am a very happy boy at the moment.
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,962
1,318
SWE
@englertracing
Do you have any pointers about the size (flow area) of the low speed bleed on the main valve ?
I am removing some of the ridge on which the check valve is sitting as a lsc bleed for my Grip damper. It will obviously not be adjustable
Screenshot_20210806-162842_Gallery.jpg
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,962
1,318
SWE
The bleed on the picture above is on the low side but I find out that the blue adjuster also works as a lsc adjuster since it allows to change the float of the shimstack.

The picture below shows the comp side of the piston after being sanded down.
20210806_161252.jpg
 

englertracing

you owe me a sandwich
Mar 5, 2012
1,590
1,086
La Verne
well,
you could have dropped a 6x8x0.1 or a 6x8x0.15 shim in the recess to accomplish the same thing but in a reversable fashion.
the effect with that or what you did will essentially limit how far the loader can preload the shimstack. In the case of a grip 1 the lockout aspect is now mostly disabled.

for the low speed bleed
you could.... drill a hole from compression ports to recharge ports,
use a file to file a trech in the remaining portion of the lip, or grind a v on the edge of a shim
grinding a u on the edge of a shim is the most reversible, as you can make it larger or move it up in the shim stack to delete it, and you have several attempts to get it right.

WAG on sizing, I would say a notch in the shim exposing the equivelent of a 0.5mm hole would be a good conservative starting point.

edit, Just now see you filed a trench on the refill side.
yeah that will probably suffice.
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,962
1,318
SWE
Thanks for your feedback, I appreciate!
you could have dropped a 6x8x0.1 or a 6x8x0.15 shim in the recess to accomplish the same thing but in a reversable fashion.
Yes I could indeed have done that. Now it's done, live and learn :D

The center part of the piston is 6mm in diameter (see picture below) and the comp preload hat is 8mm wide at its tip so that the clamping diameter is 8mm and only "solid " where the 4 bridges are. I don't know how that affects the stiffness of the stack and how the pressure on the stack from the preload hat changes that...? Maybe having a 8mm wide shim at the bottom would have helped getting a more even clamping?
Anyhow, it probably doesn't matter as long as the damping is enough!
Screenshot_20210806-205916_Chrome.jpg


this shim pack would be something I would explore.
I went with something a bit stiffer: five 0.1mm shims in a pyramid shape. I will adjust it after a test ride if needed. Thanks for the pointer!
 

Kanye West

220# bag of hacktastic
Aug 31, 2006
3,743
476
Don't go sanding your goddamn pistons...it's a bush-mechanic "trick" that got popularized in the moto world and 99.9% of the time does far more harm than good.

For starters, positive sealing against a piston by way of dishing is a good thing for repeatability. There are reversible ways to check to see if you would want less preload against a valve with all else being equal (nothing, relief shims, etc).

If you sanded it by hand, I guarantee you that's nowhere near level and is allowed additional bleed on its own. That's a modification that has to be done on a trued up machine to do what you want it to do.

Ultimately, by removing preload from the sealing face of a valve, you remove a major and critical dimension of damping curve manipulation.

Get a new piston and start over.
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,962
1,318
SWE
@Kanye West
I still have a lot to learn, I am aware of that. I appreciate every feedback I can get.

I sanded the piston like I would do when sharpening my woodworking tools with a sheet of sandpaper lying on a flat smooth surface and moving the piston back and forth. I used 240 grit only and didn't go for a mirror like finish.
It is probably not flat enough.

Ultimately, by removing preload from the sealing face of a valve, you remove a major and critical dimension of damping curve manipulation.
Is preload really so important?
The guy behind Novyparts has the piston below in his compression block called Splug which replaces the horrible MoCo block. The sealing face of the valve is flat and he doesn't use ring shims. He actually makes a point about having no preload since preload delays the opening of the high speed circuit and thereby creates harshness.
16730121_1786909228296847_6161667400059197664_n.jpg


Manitou in their ABS+ tuning guide also have a few stacks without preload. They call it the linear serie and describe it as follows
This series of shim stacks is best used when
no pedal platform is desired, and big hit plushness, bottoming resistance, and dive
control are all needed. Without the platform, the adjuster needle can be run closer
to max for improved chassis control (more low-speed damping), while not hurting
the fork’s ability to absorb larger inputs
.

Grip2 doesn't seem to be preloaded either? Or is it by the number of shims added above the "propellers"
Screenshot_20210807-112147_Chrome.jpg
 

englertracing

you owe me a sandwich
Mar 5, 2012
1,590
1,086
La Verne
There's 2 kinds of preload.
The kind that's there to create degressive damping.
And the kind that promotes seal.

Shims can warp after use or the edges can lift when you tighten them down.

Many pistons appear flat, but when you put a straight edge across them you can see they are infact minutely concave to promote a consistent seal
 

6thElement

Schrodinger's Immigrant
Jul 29, 2008
16,284
13,560
‘19 Fox 36? 2022 Fox 36

There. I did it.
FTFY, it fixes the issues with the 2021 model where it was too spikey, not enough mid-stroke support and needed better bottom out resistance. It comes it a cool new colourway too.
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,962
1,318
SWE
I had some time riding on the modified Grip and it turned out great, much better than the harsh and not so supportive original.
 

Kanye West

220# bag of hacktastic
Aug 31, 2006
3,743
476
@Kanye West
I still have a lot to learn, I am aware of that. I appreciate every feedback I can get.

I sanded the piston like I would do when sharpening my woodworking tools with a sheet of sandpaper lying on a flat smooth surface and moving the piston back and forth. I used 240 grit only and didn't go for a mirror like finish.
It is probably not flat enough.


Is preload really so important?
The guy behind Novyparts has the piston below in his compression block called Splug which replaces the horrible MoCo block. The sealing face of the valve is flat and he doesn't use ring shims. He actually makes a point about having no preload since preload delays the opening of the high speed circuit and thereby creates harshness.
No problem.

If you sanded it by hand, put a straightedge against the piston face. One of two things is sure to exist. 1) It's not 100% perpendicular to the stem/bore of the piston, even if it is totally 100% flat, or 2) it is not 100% flat. In either case, the shims aren't creating a seal and it's allowing blow-by. All your low speed and most of the high speed control is gone. This is particularly dangerous on the rebound side (I've had moto tuners do this as their "factory" trick and the extra mm of bleed at every port damn near killed me when I rode it).

Preload by itself doesn't create harshness. Preload of a disproportionate amount creates harshness. Without preload, you lose the ability to independently create force in the low speed regions and high speed regions of a force-displacement curve. If you've got a totally flat piston and basic shimstack, your options are overall stiffer or overall softer, to the point where the piston porting starts limiting fluid transfer. Removing whatever was designed into it creates a LOT more problems than it solves.

The point is that there are a lot of things to adjust internally before you start removing key pieces of the damper architecture without knowing what all of the effects are. And realistically that takes a dyno and modeling software to correlate it.
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,962
1,318
SWE
Thanks @Kanye West !
I will not sand my pistons again. And yes, without a dyno, I am mostly shooting in the dark... But I like to play the game. I go by feel and sometimes use a Shockwiz as a confirmation bias device when tuning my suspensions. I got a perfect score for this tune, FWIW

@bullcrew I will come back to you later with some details about the mods. I don't have my notes with me.
Beware that my fork is a 120mm 34 and I weight 165 lbs. You might need to adjust the shims to your liking / fork.
And I will also tell you how to avoid the sanding.
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,962
1,318
SWE
@bullcrew
Here is what I used
Comp:
14x6x0.1 *2
13.6x6x0.1 *2
12x6x0.1
To avoid sanding the piston, use first enough thickness of 8x6 shims to almost fill the recess. I didn't measure how deep the recess is but it should be around 0.3 to 0.4mm

Mid:
18x7x0.1
12.5x7x0.1

Rebound:
17.35x6x0.15 *2
15×6×0.15 *2
13×6×0.15 *2
8×6×0.3 (clamp)
Revalving not needed but my OCD requires pyramid shaped stacks :bonk:
 

englertracing

you owe me a sandwich
Mar 5, 2012
1,590
1,086
La Verne
@bullcrew
Here is what I used
Comp:
14x6x0.1 *2
13.6x6x0.1 *2
12x6x0.1
To avoid sanding the piston, use first enough thickness of 8x6 shims to almost fill the recess. I didn't measure how deep the recess is but it should be around 0.3 to 0.4mm

Mid:
18x7x0.1
12.5x7x0.1

Rebound:
17.35x6x0.15 *2
15×6×0.15 *2
13×6×0.15 *2
8×6×0.3 (clamp)
Revalving not needed but my OCD requires pyramid shaped stacks :bonk:
have you considered trying LEZ SHIMZ on rebound?

I found on the grip 2 with 3x 17.xx the hsr was a bit slower than the RC2
I went to
17
17
11
But ended up adding some stiffness back in with the vvc adjuster.
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,962
1,318
SWE
have you considered trying LEZ SHIMZ on rebound?

I found on the grip 2 with 3x 17.xx the hsr was a bit slower than the RC2
I went to
17
17
11
But ended up adding some stiffness back in with the vvc adjuster.
No I haven't yet, I might.
The original rebound stack was 5x 17.35x0.15 and since I went for a pyramid shape, I thought that adding one of the smallest in diameter would more or less compensate for loss of stiffness due to the pyramid.

I run 93psi and 2 tokens on the air side for 120mm of travel on an Evol 34. Rebound is 3 clicks from closed.

3 clicks from closed? That should be enough to justify less shims, don't you think?
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,962
1,318
SWE
Screenshot_20210821-105702_Instagram.jpg

I saw that on Instagram the other day from Mojo rising about their 36 Mork upgrade.

What puzzles me the most is the "lower bushing sliding inside the lower legs"... is that possible? I mean the 36's lower legs have not been designed for that from the beginning so that it might require some machining to make the surface round and smooth on the inside where the lower bushing will be running.
On top of that removing metal on an already weight optimized casting sound risky...
Or maybe they push a sleeve in instead?
 

HAB

Chelsea from Seattle
Apr 28, 2007
11,583
2,012
Seattle
View attachment 163897
I saw that on Instagram the other day from Mojo rising about their 36 Mork upgrade.

What puzzles me the most is the "lower bushing sliding inside the lower legs"... is that possible? I mean the 36's lower legs have not been designed for that from the beginning so that it might require some machining to make the surface round and smooth on the inside where the lower bushing will be running.
On top of that removing metal on an already weight optimized casting sound risky...
Or maybe they push a sleeve in instead?
IIRC that was Chris' sketch for what an idealized MTB fork would look like, from quite a few years ago. And then they said the MORC 36 was starting to get pretty close. I don't think it actually has the sliding bushing.
 

Kanye West

220# bag of hacktastic
Aug 31, 2006
3,743
476
Nobody is going to control the lower assembly fitments well enough to have a telescoping bushing in a sleeve down there. It also means the stanchion has to get thicker to accommodate a groove in it, and there are some tricky engineering details of that groove that are critical to the performance too. Overall that layout would mean a sizable weight and cost increase.

Adjusting the offset by inserts in the clamps is also a good idea. On paper...only. Adjustable offsets have been answered in steerer tubes of moto clamps and keeping them keyed to 0 and 180. No alignment errors that a user can make that way.
 

englertracing

you owe me a sandwich
Mar 5, 2012
1,590
1,086
La Verne
Nobody is going to control the lower assembly fitments well enough to have a telescoping bushing in a sleeve down there. It also means the stanchion has to get thicker to accommodate a groove in it, and there are some tricky engineering details of that groove that are critical to the performance too. Overall that layout would mean a sizable weight and cost increase.

Adjusting the offset by inserts in the clamps is also a good idea. On paper...only. Adjustable offsets have been answered in steerer tubes of moto clamps and keeping them keyed to 0 and 180. No alignment errors that a user can make that way.
the only reason i can see for a sliding lower bushing is that if at top out the bushings were the same distance as a fork with a fixed lower bushing, at any point in the travel the bushing spread would be greater on the sliding bushing fork. and you GET to do the fancy crowning of the bushing land to create a swiveling bushing in contrast to none of that action being available with a fixed lower bushing. So theoretically you can reduce friction this way butt as you said it will add weight, and if you minimize that with a bunch of machine work you get a lot of extra cost, and waste.


can anyone say KASHIMA LOWERS?
:happydance:
 

HAB

Chelsea from Seattle
Apr 28, 2007
11,583
2,012
Seattle
Nobody is going to control the lower assembly fitments well enough to have a telescoping bushing in a sleeve down there. It also means the stanchion has to get thicker to accommodate a groove in it, and there are some tricky engineering details of that groove that are critical to the performance too. Overall that layout would mean a sizable weight and cost increase.
I haven't thought about it very hard yet and I am into beer #3 already (rough work day) but what's the thinking behind the grooved stanchion? I'm missing why that's needed. Definitely with you that that would be a miserable thing to have to manufacture though.

Adjusting the offset by inserts in the clamps is also a good idea. On paper...only. Adjustable offsets have been answered in steerer tubes of moto clamps and keeping them keyed to 0 and 180. No alignment errors that a user can make that way.
That is how Mojo actually does it. I've had a set of their 40 crowns for a couple years, and they're sold. That sketch is... a rough sketch. Doing it in the stanchion clamps would be dumb for... a whole bunch of reasons.
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,962
1,318
SWE
IIRC that was Chris' sketch for what an idealized MTB fork would look like, from quite a few years ago. And then they said the MORC 36 was starting to get pretty close. I don't think it actually has the sliding bushing.
Indeed, you are right!

@Kanye West
This french guy behind CRConception has sliding bushings on his up side down fork. You can see some details below. FWIW
70062837_2410583122360251_7321531269458690048_n.jpg

39227209_1827381284013774_1916577298404868096_n.jpg
 

Balgaroth

Chimp
Oct 22, 2021
45
29
Alsace (FR)
@bullcrew
Here is what I used
Comp:
14x6x0.1 *2
13.6x6x0.1 *2
12x6x0.1
To avoid sanding the piston, use first enough thickness of 8x6 shims to almost fill the recess. I didn't measure how deep the recess is but it should be around 0.3 to 0.4mm
I can confirm that the gap to fill on the compression side of the BV is 0.3mm. I filled it with what I had at hand so 10x0.3mm shim. Ideally you'd want to use 8x6 with a 0.1mm and a 0.15mm to improve piston face seal but since the grip damper compression knob influences stack float/preload I am not sure it is that important, unless you still want some pedal platform when fully closed.

I kept my original stack (4x13.6x0.1mm) to which I added another 14x0.1mm shim. I also created a small notch on the check valve ridge.

I didn't find any wave washer in my Z1 grip damper.

So far I only had the chance to test the result on carpark, stairs and curbs but the whole range of adjustment is actually usable, closing the compression knob offers a very supportive feel but seems like it could actually be used on the trails too, the harshness is nowhere near what it is in stock form past 2/3 open. Hopefully I get to try this soon enough on the trails.
 
Last edited:

Balgaroth

Chimp
Oct 22, 2021
45
29
Alsace (FR)
So far I got a few rides with the setup above, the fork is very supportive which is great to push in turns and pump. I am using less travel on bigger impacts but comfort is down a bit (usable tho). The adjuster has been closed pretty much all the way (to the contact point with the shims) so far to get a feel for the current setup before playing with the adjuster. I will try opening up the adjuster a touch to see if I can find support and more comfort. Otherwise I suspect that the 10x6x0.3mm shim used to fill the preload gap is too stiff/too big and restrict the flow. In which case next experimentation will be with 3 shims 8x6x0.1mm which are smaller and way softer than one 0.3mm shim. If that doesn't solve it I might go with thicker fewer face shims and reduced clamping diameter.

Does anyone know the compression hat face clamping diameter ? I think I saw it somewhere on the internet but can't find it anymore.
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,962
1,318
SWE
by compression hat, do you mean the one circled in red below?
1649834052018.png

I am not sure but I remember 8 mm. Maybe you can get some info from the drawings on Fox's site?
 

Balgaroth

Chimp
Oct 22, 2021
45
29
Alsace (FR)
by compression hat, do you mean the one circled in red below?
View attachment 174911
I am not sure but I remember 8 mm. Maybe you can get some info from the drawings on Fox's site?
That's the one yes. I'd like to know the size of the flat spot. Not something that will be on Fox's website.
If you are correct and it is 8mm (more or less) there isn't much room to play with clamping diameter to reduce HsC so no point looking further into this. Could mean that you can increase HsC if needed by adding some 10x6x0.3 or 12x6x0.3 at the back of the stack if needed tho.
 

Balgaroth

Chimp
Oct 22, 2021
45
29
Alsace (FR)
So far I got a few rides with the setup above, the fork is very supportive which is great to push in turns and pump. I am using less travel on bigger impacts but comfort is down a bit (usable tho). The adjuster has been closed pretty much all the way (to the contact point with the shims) so far to get a feel for the current setup before playing with the adjuster. I will try opening up the adjuster a touch to see if I can find support and more comfort. Otherwise I suspect that the 10x6x0.3mm shim used to fill the preload gap is too stiff/too big and restrict the flow. In which case next experimentation will be with 3 shims 8x6x0.1mm which are smaller and way softer than one 0.3mm shim. If that doesn't solve it I might go with thicker fewer face shims and reduced clamping diameter.

Does anyone know the compression hat face clamping diameter ? I think I saw it somewhere on the internet but can't find it anymore.
Quick update. The setup was good enough on my home trails (soft loamy with few rock gardens) but when I hit the Bikepark it became apparent quitte quickly that the 10x0.3mm shim used to fill the gap restricts the flow too much, especially at the clicker setting I was using. I had to open the clicker fully in order to finish the day and it was hard on my hands. I doubt this is the result of the extra 14x0.1mm I put on top of the stack. I will replace the 10x0.3mm shim by 3/9x0.1mm shims and see how this works. Aside from lower OD which will have less effect on flow, it is also 9 times softer than a single 0.3mm shim, that way, when flow need more room it will be able to push these out of the way a lot more that the previous shim.
I also got a second grip cartrigde for spares, this way it will be easier to test stuff, additionnally it means I have a spare piston which I could flaten like Happymtb did.