Fox Factory 38 - missing travel

Evolution Stu

E*POWAH Master
Jun 30, 2019
455
447
Blackpool. U.K.
Morning folks,
I wonder if any of you Fox 38 owners have noticed this on your fork…

I have treated myself to a Fox 38 factory 160 at a bargain price as wiggle are selling some OE stuff off cheap. (Very cheap…be quick)

I am 101kg fully kitted and have found I need 100psi to give me between 25 and 28mm sag depending on how I am sat, so probably around 18% average.

My pressurisation technique is all damping off, pressurising 10psi at a time, cycling the fork between settings with both a pushing and pulling motion to ensure equalisation of lower chamber. I have always done it this way and never had an issue on 36s.
However, with the bike stationary and unloaded, if I sit on the front wheel and lift the bars up, (pull up on the fork) I can expose an additional 15mm of shaft.

Lifting the bike off the ground to unweight the fork only exposes about 5mm of additional travel, as I would expect for the weight of bike. But to expose the full travel extension you have to pull against what feels like a spring (so a vacuum causing suck-down)

Surely 100psi should push the fork to its max extension? I have even tried inflating to 125psi to see if additional pressure extends her to full. But it doesnt. There is always extra travel hidden away. (Like permanent built in sag if that helps you picture the issue…)

So my question is, does everyone else with a 38 have this missing travel with their fork? Or is it just mine and it’s suffering from suck down brand new out of the box?

footnote:
This fork has not yet been ridden. It’s brand new. I’m trying to get her ready for a decent day at the Golfie on Sunday and this anomaly has me wondering if there is an issue.

**Edit**
I have also depressurised the lowers via the new push buttons on the lowers.

Pic for some colour.
(Blue decals on their way… this O.E. stealth is boring, but at £800 discount who cares?)

IMG_1064.jpeg


**Update - FIXED. See post 6 **
 
Last edited:

Evolution Stu

E*POWAH Master
Jun 30, 2019
455
447
Blackpool. U.K.
I think most forks do this. You are pulling it past where the +ve and -ve chambers equalise, which should be at 160mm travel.

The equalisation port is normally in the normal travel section, otherwise it would never work... but I am not really sure with this new Fox cartridge system on the 38 as I’ve never seen inside one.
 
Last edited:

Evolution Stu

E*POWAH Master
Jun 30, 2019
455
447
Blackpool. U.K.
**Update - Fixed **
Decided to nip home at lunch and have a play with it as it was bugging me. :unsure:
And its now fixed. (y)

Since this might be of interest to other owners of any fork, I will detail the procedure I used here:

Step 1: Depressurise the fork slowly whilst equalising as you go down.
Step 2: Remove the air cap completely.
Step 3: Remove wheel and refit axle.
Step 4: Stand on axle and pull up hard, to extend the fork as far and as fast as you can multiple times.

The theory is, the huge depression caused in the lower chamber will suck through any grease blocking the transfer port.
I certainly didn't hear anything happen, but i was huffing and puffing as its hard to pull up against the depression there

I then repressurised as normal and found the fork hits full extension about 75psi now.
Happy days. :)
 

Mikerb

E*POWAH Elite World Champion
May 16, 2019
6,283
4,780
Weymouth
Well done.............I have actually seen that method somewhere else but cant remember where now! Another method is to ride it as is on a good trail with drops and jumps...........then go back and see if that has done the trick.
I do not think it is excess grease that causes this problem but more likely the amount of time the fork is on the shelf after assembly before being used...very likely in very different temperatures etc........which turns the grease more sticky.

ps I note you said you set your fork sag whilst sat on the bike. It is more accurate to set the sag stood on the pedals in the ready position in my opinion. I am 77kg riding weight and have my Fox 38s ( non E biketype) at 75psi so if you are c 100kg riding weight I would expect you to need c 85/90 psi.

My other bike also has Fox 38 Factory but is the E bike tuned version which has different tuning in the damper resulting in less air pressure required in the air spring compared to the non E Bike version. So I am running 70 psi on that fork.
 
Last edited:

Harry Fettes

Member
Aug 29, 2022
5
0
Aberdeenshire
**Update - Fixed **
Decided to nip home at lunch and have a play with it as it was bugging me. :unsure:
And its now fixed. (y)

Since this might be of interest to other owners of any fork, I will detail the procedure I used here:

Step 1: Depressurise the fork slowly whilst equalising as you go down.
Step 2: Remove the air cap completely.
Step 3: Remove wheel and refit axle.
Step 4: Stand on axle and pull up hard, to extend the fork as far and as fast as you can multiple times.

The theory is, the huge depression caused in the lower chamber will suck through any grease blocking the transfer port.
I certainly didn't hear anything happen, but i was huffing and puffing as its hard to pull up against the depression there

I then repressurised as normal and found the fork hits full extension about 75psi now.
Happy days. :)
This seems to reinforce the view that the best thing to do with Fox or Rockshox fitted as OEM equipment is to send them for a service. QA/QC on stuff supplied to OEMs doesn't seem great.
 

Planemo

E*POWAH Elite
Mar 12, 2021
601
705
Essex UK
If the port was blocked, are you saying the forks were never equalised prior to your stripdown? Or that they were, but only from the original factory pressure, and that your process of pumping/equalising didn't change what was in the negative from the factory?

Theres also the school of thought that equalising every 10psi can actually hinder rather than help. Eg if you go to 50psi pressure over negative then theres a much higher chance of blowing out any grease from the port. I'm not saying one way is better than the other though as personally I do a stripdown on every new set of forks to make sure it's lubed right.
 

Evolution Stu

E*POWAH Master
Jun 30, 2019
455
447
Blackpool. U.K.
If the port was blocked, are you saying the forks were never equalised prior to your stripdown? Or that they were, but only from the original factory pressure, and that your process of pumping/equalising didn't change what was in the negative from the factory?

Theres also the school of thought that equalising every 10psi can actually hinder rather than help. Eg if you go to 50psi pressure over negative then theres a much higher chance of blowing out any grease from the port. I'm not saying one way is better than the other though as personally I do a stripdown on every new set of forks to make sure it's lubed right.

Morning,
It didn’t have a strip down. It is a brand new unridden fork. I checked pressure and it was at 70psi out of the box so I inflated it and noted it never went to full extension travel of its own accord.

I get your point about the differntial pressure probably being of more help and in reality, that is EXACTLY what my eventual fix created, a huge differential pressure across the transfer port.

There may well be some mileage in tour suggestion that doing it in small increments could cause more harm than good to a contaminated fork.
 

Planemo

E*POWAH Elite
Mar 12, 2021
601
705
Essex UK
Ah sorry yeah I just re-read your post, you just took the top cap off.

I still think it's strange that such a small nubbin of grease can stay put even with minor pressure differentials. But you're yet another owner that seems to have proved this is indeed the case. Maybe the manufacturers just need to use a thinner grease...although I'm sure they have thought of that...
 

Shjay

Well-known member
Apr 30, 2019
835
491
Kent
Thing is we moan the forks shipped with too much grease, & then moan no oil in the lowers yet we are basically getting a fork at 60%+ off RRP as they are older forks sat around in a warehouse for year or so.
 

Evolution Stu

E*POWAH Master
Jun 30, 2019
455
447
Blackpool. U.K.
Thing is we moan the forks shipped with too much grease, & then moan no oil in the lowers yet we are basically getting a fork at 60%+ off RRP as they are older forks sat around in a warehouse for year or so.

Unless when they drop the price of the fork they also strip it down and add a ton of grease then I don’t really see your point. 🤷‍♂️

Regardless of actual purchase price, this is a high end £1450 product that should perform as advertised.
 

Shjay

Well-known member
Apr 30, 2019
835
491
Kent
Unless when they drop the price of the fork they also strip it down and add a ton of grease then I don’t really see your point. 🤷‍♂️

Regardless of actual purchase price, this is a high end £1450 product that should perform as advertised.
Any fork sat 6-12 months won’t perform so well. They put in extra grease to ensure there’s some in 12months time. You could measure 20 different fox forks & their stanchions would all be different measurements of same 160mm fork. End of day fox QC is poor & not considered high end as come on most bikes
 

Evolution Stu

E*POWAH Master
Jun 30, 2019
455
447
Blackpool. U.K.
Any fork sat 6-12 months won’t perform so well. They put in extra grease to ensure there’s some in 12months time. You could measure 20 different fox forks & their stanchions would all be different measurements of same 160mm fork. End of day fox qc is poor & not considered high end as come on most bikes

Ok mate. :)
 

Alexbn921

Well-known member
Sep 27, 2021
545
508
East Bay CA
It wasn't the grease. There is zero chance that grease could hold back even 5psi.

It probably leaked positive air into the negative and then trapped in preventing it getting to top out and the port. Putting extra air in and pulling past the dimple would fix this just like the OP did.

Excessive grease in the negative chamber will ride harsh and not be supple off the top.
 

irie

E*POWAH Elite World Champion
Subscriber
May 2, 2022
2,220
2,157
Chichester, W.Sussex, UK
Why Fox continues to ship forks with excess grease is beyond comprehension. It's a known issue that has been around for a while.
Same as Rockshox.

Decided to do a lower leg service on my new ZEB Ultimate A2 forks. Found far too much grease on the airshaft. Cleaned off all the grease, re-greased with the correct amount of grease, and put the right amount of the right oil in the damper and airshaft sides. Now work very nicely.
 
Last edited:

Downhillr

Active member
Jul 2, 2021
257
131
SF Bay, California
Well done.............I have actually seen that method somewhere else but cant remember where now! Another method is to ride it as is on a good trail with drops and jumps...........then go back and see if that has done the trick.
I do not think it is excess grease that causes this problem but more likely the amount of time the fork is on the shelf after assembly before being used...very likely in very different temperatures etc........which turns the grease more sticky.

ps I note you said you set your fork sag whilst sat on the bike. It is more accurate to set the sag stood on the pedals in the ready position in my opinion. I am 77kg riding weight and have my Fox 38s ( non E biketype) at 75psi so if you are c 100kg riding weight I would expect you to need c 85/90 psi.

My other bike also has Fox 38 Factory but is the E bike tuned version which has different tuning in the damper resulting in less air pressure required in the air spring compared to the non E Bike version. So I am running 70 psi on that fork.
Wow, you appear to be running fork air psi well below Fox setup recommendations…

Is anyone else finding the Fox guidelines to be so out of line?
(Looks like you’re using settings for rider 1/2 your weight range). I’m using Factory 38 with 108-110 psi for my 200 lb rider weight on Santa Cruz Bullit ebike.
 

Downhillr

Active member
Jul 2, 2021
257
131
SF Bay, California
Wow, you appear to be running fork air psi well below Fox setup recommendations…

Is anyone else finding the Fox guidelines to be so out of line?
(Looks like you’re using settings for rider 1/2 your weight range). I’m using Factory 38 with 108-110 psi for my 200 lb rider weight on Santa Cruz Bullit ebike.
Should note it’s ebike version fork and aI pulled one volume token since I didn’t have any harsh progression at end.
 

RickBullotta

E*POWAH Elite World Champion
Jun 5, 2019
1,824
1,556
USA
Wow, you appear to be running fork air psi well below Fox setup recommendations…

Is anyone else finding the Fox guidelines to be so out of line?
(Looks like you’re using settings for rider 1/2 your weight range). I’m using Factory 38 with 108-110 psi for my 200 lb rider weight on Santa Cruz Bullit ebike.

Yup. I tend to run 5-10 psi lower than spec - otherwise the front end pushes.
 

Bones

E*POWAH Elite
Subscriber
Apr 3, 2020
828
1,074
Harrogate
Well mine came back from silverfish with a new damper and full service.
Set them up on local ride with 91 PSI for 34mm sag, I'm around 86kg.
None ebike factory 38s. 170mm
I've just got back from a big ride and I've been shaken to bit's on the fast rocky descents.
Part way round I opened up the fast rebound a couple of clicks and it seemed to be better but I lost the front wheel a couple of times so maybe not.
Anyway back home I checked the sag and it was about 15mm!
I have had to adjust it to 70psi to get 30mm.
I'm sure that's far too low pressure.
Bloody things 🤔
 

Bones

E*POWAH Elite
Subscriber
Apr 3, 2020
828
1,074
Harrogate
Well mine came back from silverfish with a new damper and full service.
Set them up on local ride with 91 PSI for 34mm sag, I'm around 86kg.
None ebike factory 38s. 170mm
I've just got back from a big ride and I've been shaken to bit's on the fast rocky descents.
Part way round I opened up the fast rebound a couple of clicks and it seemed to be better but I lost the front wheel a couple of times so maybe not.
Anyway back home I checked the sag and it was about 15mm!
I have had to adjust it to 70psi to get 30mm.
I'm sure that's far too low pressure.
Bloody things 🤔
Edit and that's with a spare battery in my backpack so something is miles out
 

Downhillr

Active member
Jul 2, 2021
257
131
SF Bay, California
Well mine came back from silverfish with a new damper and full service.
Set them up on local ride with 91 PSI for 34mm sag, I'm around 86kg.
None ebike factory 38s. 170mm
I've just got back from a big ride and I've been shaken to bit's on the fast rocky descents.
Part way round I opened up the fast rebound a couple of clicks and it seemed to be better but I lost the front wheel a couple of times so maybe not.
Anyway back home I checked the sag and it was about 15mm!
I have had to adjust it to 70psi to get 30mm.
I'm sure that's far too low pressure.
Bloody things 🤔
My apologies if this is redundant info but here’s another Fox guide on 38 fork setup, this isn’t ebike version (which actually are a bit softer internal shim) which list a bit higher psi setting.
I’m just curious if your fork is extending fully since there’s a couple mentions regarding that issue in this thread? If it’s not then you could be measuring sag from wrong starting point.
My fork was gone through when new: excess grease in negative, dry fork seals, wrong fluid level… and missing a correct shim in stack. Since my son’s a trained/schooled bike, Mercedes, Acura and light rail technician he addressed the shim stack issues with Fox techs who said yep, you’re right and provided correct pieces at no charge. Seems their production QC is not consistent so you may want to be sure forks at spec.
 

Mikerb

E*POWAH Elite World Champion
May 16, 2019
6,283
4,780
Weymouth
I base my settings on what performs best rather than what Fox or RS say!! I fail to see how Fox etc can make recommendations for a fork when it could be fitted to different bikes with differing head angles and trail etc.
Both my forks are supple at the top of the stroke, sit mid stroke mostly when descending and have enough progression to a void any bottom out (and have full travel........180mm on the Ebike version, 160 on the non Ebike version). That said, the setting are very different on my Ebike tuned 38s compared to my non Ebike 38s. I am close to Fox recommended settings for compression and rebound ( high and Low speed) on the Ebike 38s, but quite a bit more open/fast on all settings on the non Ebike 38s............... that is also the case for testers on some reviews I have read. The Ebike 38s are on my Whyte e180RS, the non Ebike 38s on my Whyte E160 RSX .
 

Bones

E*POWAH Elite
Subscriber
Apr 3, 2020
828
1,074
Harrogate
Me again 😅
Being retired and bored shitless I decided to have another play with my forks. Now everytime I check my sag it's at a different psi to get 34mm!
So I have spent an hour or so at different pressure's and tokens to give me some idea of where I need to be with my forks.
The photo might be of some use to you guys?
IMG_20230703_144059.jpg
 

Alexbn921

Well-known member
Sep 27, 2021
545
508
East Bay CA
Your spending too much time worrying about sag. It doesn't matter other than a check at the end to make sure you are not completely screw up with your settings.

You want the least amount of tokens you can run without bottoming. Remove a token and and air until you don't bottom out. If you don't have any sag, add tokens and reduce psi until you find the sweet spot of compliance and end stroke support.

I tend to prioritize very fast rebound and add compression to help with bottoming vs adding a tokens and getting a harsh ramp.
 

Cramman

Member
Oct 22, 2022
14
5
South Shields
Infuriating mate, at full retail price this is a £1450 product.
How the hell can it be turned to crap by over application of grease after all these years?!
Thanks for this. Just tried on my fork that won't use full travel and very harsh off the top. Couple of big sucking noises then I first pulled up then it stopped. Fingers crossed it's all good this weekend but I still think I'll be sending it off for a service
 

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