2023 YT MX Core 4 Suspension Setup

[Efrosty]

Sorting through several on this new bike and now suspension.

In particular, the front, riding the bike even on smooth trails, front feels like you’re riding over rumble strips. Constant chatter.

Fork is 170mm fox 38 FLoat Factory I followed the YT recommendation. But sag with the air pressure they recommend wasn’t close.

So think I’ve dropped it down to 90 psi, and out riding finally went to LSC and HSC all the way soft. If I hit something large, at speed it’s not bad.

It’s just trying to get it supple over roots and small chop which is the main reason I purchased the bike.

I’m going to drain the air and fill back up per the instruction again. Curious if others have experienced this and what they did? My main goal is roots, rocks and rough chop and a smooth ride.

 

[Efrosty]

Following manual and recommended sag of YT, having to drop the air in the forks to 75 psi vs 116 they recommend..

 

[wenna]

A brand new fork will need some time to "break in".

When you fill it with air, are you equalizing the air chambers? Sometimes new forks can have too much grease blocking the equalizing port.

Also you should have compression and rebound dials all the way open when you pump it with air and set the sag.

 

[skinipenem]

Disorganized response here:

How much do you weigh?
How fast do you ride?

The fox 38 has a very stiff chassis. It won't feel supple at low or moderate speeds ever.

Too low of pressure will result in a harsh feel since the fork will be on a steep portion of the progression curve. In other words, riding in Too low of the travel. Too much Rebound dampening will result in the same problem due to the fuel packing down.

As previously mentioned, you need (I think you are) to allow for the negative and positive chambers to "even out' when pumping up the fork.

Perhaps there are too many tokens/spacers installed.

I've heard of the forks coming with too much ir too little grease... not sure about that though.

There is also a high likelihood that the stanchions are not aligned. Send the fork to a suspension tuning specialist and have them check the alignment and give it a tune as well. An excellent local mechanic can check Too however you might as well get it tuned. Unfortunately, this might be the most likely issue along with the fact the 38 has a very stiff chassis.

If the above does not suffice:

If you are a lightweight you might be better off just switching to a lyrik... less stiff chassis.

And/or

Install a dsd runt.


Fwiw: I unweight the bike to take a final measurement of pressure. The ebike is so heavy that it sags under its under its own weight.

 

[wenna]

One more thing came to mind. I´m not used to MTB forks having a pinch bolt but have been doing this forever with motocross bikes. Loosen the pinch bolt and compress the fork several times before tightening the pinch bolt again. This is to make sure the lower legs are straight and not binding.

 

[skinipenem]

And minor... but... don't forget to bleed the air out of the lowers multiple times each ride. Those are the buttons on the aft portion of the lowers.

 

[Efrosty]

116psi stated for 200lbs. Average around 10mph typically on rides.

I assume you’re referring to stiff chassis and referring to there is no deflection. But the angle of these forks, I was hoping that would put the absorption mainly on the fork vertical travel.

Yes, I did the 10psi at time.

I’m ex MX as well and used to valve my own suspension, been a long minute though. I’m concerned about air pressure but to get the sag to recommended 25 to 30%, I’m having to go down to 75 to get 41mm and they recommend 42 to 50 mm on the fork.

I don’t do big stuff like jumps, hard landings, again just trying to get supple so it’s not like riding a jack hammer through roots around here.

I’ve never had luck with any air suspension. Just watching them riding, the visual, they just don’t seem to be that active except for hard landings, but just seems with a 170 mm of travel that has to be a way or an option to configure.

I’ve seen a few talking about Ohlins but I just got this bike, 2 9 mile rides so I’m hoping maybe there is a break in period.

The other comments, I’ll redo the pinch bolts.

But again find it odd that the fork and YT configurator call for 116psi but to get the sag based on the techniques they indicate to measure, I’m down to a low PSI.

 

[Efrosty]

Bled all air out, brought back up 10psi at a time, compressing. Went to 80psi. LSC, started at 12 out and add a few more while riding and opened up HSC to wide open.
Increased power to increase speed a little.

The bike handles great and a little smoother over all but some roots you’d think you wouldn’t feel, just harsh. It feels like the tires compress and just spring the bike up, what it feels like but sure the fork is working a little, just not what it should.

No air to bleed. Calling YT tomorrow.

 

[Dirtnvert]

Bled all air out, brought back up 10psi at a time, compressing. Went to 80psi. LSC, started at 12 out and add a few more while riding and opened up HSC to wide open.
Increased power to increase speed a little.

The bike handles great and a little smoother over all but some roots you’d think you wouldn’t feel, just harsh. It feels like the tires compress and just spring the bike up, what it feels like but sure the fork is working a little, just not what it should.

No air to bleed. Calling YT tomorrow.

Good call. I bet theyre aware of a possible problem. Recently i heard of someone having to do an alignment on their 38 that came on a decoy. I'm not sure what they meant by "alignment. I was thinking maybe a bushing alignment"? Idk, but it does sound like there is atleast another case similar to yours so probably even more. Yt were great for helping me out. Chances are they pay the bill from a qualified shop or suspension specialist to tune it

 

[Efrosty]

Keeping this thread documented, decided to give AI and a few things new things I’m trying. First just pushing down on the forks just didn’t feel that smooth, even lowering the air pressure. So I put some teflon lube around the dust sweepers and worked the forks some and that seem to help.

Also, there was a suggestion of going to one air spacer from two. However, I found mine had 3 and it’s 170mm. I removed them to test this week.

Read an issue with grease and there was globs of grease inside. I got it out and then used a clean paper towel to put a light film coating.

Another thing to note, with no air, fork didn’t seem like it would full compress. I’m going to have to research what these look like fully compressed.

Around 60 to 70 psi in the forks adding air back in them, forks at least feel good for as far as I could compress them. 95+ still moved but just still seem overly still and not going to get the 30% sag they recommend. I’m going back to 90PSI.

I’ve been reading different things such as closing HSR and opening up LSR as much as possible so that’s what I’ll adjust on next time on the trail.

Attaching pics of grease, but they don’t seem to show how much was actually inside.

 

[Bones]

Good luck in setting them up. I've had mine for over 2 years and still adjusting them .
A few things I thought I'd mention is. Fox recommend 20% sag and on the 170 that's 34mm.
With my 2021 factory 38s that's around 110psi after a factory tune. Way to harsh without tokens so currently trying 90 psi.
Also you have to fully strip the air shaft out as the excessive grease is underneath what you have shown in the picture. You need to get some special tools for that job, like a tube clamp and a blow torch to remove the bottom stud.

 

[Efrosty]

Good luck in setting them up. I've had mine for over 2 years and still adjusting them .
A few things I thought I'd mention is. Fox recommend 20% sag and on the 170 that's 34mm.
With my 2021 factory 38s that's around 110psi after a factory tune. Way to harsh without tokens so currently trying 90 psi.
Also you have to fully strip the air shaft out as the excessive grease is underneath what you have shown in the picture. You need to get some special tools for that job, like a tube clamp and a blow torch to remove the bottom stud.

I was trying to follow what YT recommended, but started at their recommend air pressure, but sag isn't close. I went down to 80 but going to try 90 with no air spacers and today if I get to ride, I'm going to just start with the rebound and open up the LSR as some have suggested. Interesting, I thought the Grip 2 was the damper you wanted but I have read some indicate they swapped out to a Grip.

I'm starting to come to the conclusion that air shocks just may not can do it and spring is the way to go. We'll see what YT has to say, thanks for the input.

The grease the pictures aren't clearly showing the amount that was at the bottom of the tube, I'm going to see what this does first.

 

[Bones]

This may help or completely screw things up for you
I did some fast rocky descents on Saturday with some small jumps over land drain pipes.
I weigh 80kg in ordinary clothes.
PSI was at 95 and comps fully open. That got me to within 30mm or so of full travel and I was well happy with that.
The ride was harsh but I had HSR fully open and that was wrong!
Now everyone will tell you not to get too hung up on sag and full travel but setting the air spring soft for comfort increases travel and puts the fork into the harsher middle stroke.
Adding compression stops it diving fast into the stroke but makes it harsher .
so it's all a bit of a compromise!
Here are my yet to try settings but they should be somewhere in the ball park.
PSI 90 although possibly might need a spacer especially if I go any lower.
HSR at 6 clicks in from fully open with lsr closed
lsr then set at 8 out from fully closed.
Compression set at fox recommend settings.
HS is 5 out and ls is 10 out from fully closed and they seem to be working in the garage but on the track could be miles out.
The 38 is a hard hitting enduro type fork that is not designed to act like a soft pillow on the rough stuff and you have possibly got the wrong tool for what you want.
I also still think the air shaft needs to be fully removed and checked for excessive grease.
Good luck with your latest hobby trying to set them up

 

[Efrosty]

Wrong tool, if you mean expecting an air fork to be really adjustable and perform I'm starting to agree.

One thing I wills say, the level of what our bodies have been through and what we're willing to accept is different and tends to change with age. Hard tail used to be fine, then front fork only because a 17lb bike was the goal.

Then full suspension and now ebike with more MX type of suspension.

This should be simple, define the requirements, adjust a $1000 fork to accomplish those. If I were trying to absorb 3" chop with a 100mm fork, I get it. But 170mm should be more than enough and the whole purpose of the fork was adjustability.

In my case be able to absorb 2 to 3" at 8 to 15 mph hour . Valving, shimming or whatever should allow you to do that no matter what the fork. Sure it may not be valved properly from the factory, ok but should be an option to do so for a $1000 fork.

I'm starting to think it's just air forks, because no matter which one I try, it's generally the same conversations.

I don't need a pillow but would certain expect the fork to absorb some roots on a 4.5 mile ride without chipping my teeth or hands going numb. Maybe I just need to get on a spin bike and turn on a paint shaker and hold on it and not waste gas driving out to the trails?

FYI, in the past, I came to the conclusion it was just using forks that didn't have enough travel to be able to properly handle 1 to 3" type of chop such as roots or rocks.

I'm to the age, I don't want to destroy wrist and joints riding a bike which I love to do. I like turning laps around single track trails with elevation changes and try to keep my heart rate in whatever range. I typically use Eco mode to accomplish this.

However, I've turned the power up a tad but at the point of average 11.1 mph on trails around here and hitting speeds of up to 18+mph on single track. (That's not big down hills, flat or small inclines.)
Closure rate on regular bikes, joggers, especially those that think it's ok to have the dogs on the trail off leash is about as high as i'm going to go.

I understand what you're saying but it should be realistic to be able to take a fork with 170mm of travel and adjust it. Or if you're saying an air shock just in the tool for this job, I'm starting to agree but holding out hope now I have a fork where travel is enough long enough to handle we ride.

Next plan
YT SUpport and verify settings and shims and discuss the grease.
Also, if a spring is needed to get supple
Possibly contacting Fox.
Adjust more rebound instead of anything else right now.

One other note, I forgot to mention last night, to the travel ring on the rear shox was pretty maxed out on my last ride and I'm going to air it up and adjust the compression just a touch to make sure the stance is a little more even during the ride.

Thanks for the replies, I'll try to keep this posted.

 

[Dirtnvert]

For reference, I went back and found my settings when i had my 38 elite(i think it was "elite"/same as factory without kashima and bleeder valves).on my decoy. I had it at 180mm travel. After experimenting i end up at 90psi with one volume spacer and i wouldve weighed 80kg. Jumps, drops, whatever but nothing huge and no harsh bottom outs with the fork. Looks like i went from 84psi w 2 volume spacers to 87psi w one spacer and then settled on 90 with one spacer for the last year. My 38 was off my enduro bike do it had the regular/ non E damper

 

[Efrosty]

Good luck in setting them up. I've had mine for over 2 years and still adjusting them .
A few things I thought I'd mention is. Fox recommend 20% sag and on the 170 that's 34mm.
With my 2021 factory 38s that's around 110psi after a factory tune. Way to harsh without tokens so currently trying 90 psi.
Also you have to fully strip the air shaft out as the excessive grease is underneath what you have shown in the picture. You need to get some special tools for that job, like a tube clamp and a blow torch to remove the bottom stud.

Called YT, and no help on suspension, directed me to Fox.

Got a Fox rep, helpful and pleasant to speak with and think the issue may be trying to air up and equalize the negative chamber.

The way they describe it, air down slow until the fork does it's drop, approx. 10 to 20 mm. Set the indicator there and make sure it doesn't drop any lower when letting the air all the way out.

Air up to 50 psi and start equalizing the negative chamber. Compress forks down to the ring and should hear a hiss and then the shock releases a little there. (Kind of like a brake pedal bleeding the brakes.)

That doesn't appear to be happening, I never hear a hiss or feel the fork go down per their instructions. Assume that's because of grease potentially in there.

Listen to them talk it should be supple on the top. They indicated I could fill out a service request and they would go through it.

One odd thing, yesterday, while riding, I started out just opening the rebound setting 3 clicks at a time. I never really noticed a difference and I got to about 12 clicks on the rebound damping. When there started softening the LSC but neve really noticed anything until I got the compress all the way open on clicks as well as the rebound and it was like the fork lost air. Set them back to factory recommendations the rest of the ride and just dealt with them.

I'll look at the tools to get the air shaft apart or wait till bad weather and just send it to them. They indicated they had a new piston or something they are testing that is supposed to be good.

Thanks for the responses. I'll keep the thread updated as I go along.

 

[Chrysaor]

Grease cannot block an equalization port there is just too much pressure there.
How do you find the friction with all the air out and the damper setting fully open? A possibility could be tight bushing, I don't know how often it happens on the fox38 but I had the case on another brand, had the bushing burnished for 30€ and the sensitivity was much better (but annoyed to have to do it on a brand new expensive fork).

 

[Efrosty]

Grease cannot block an equalization port there is just too much pressure there.
How do you find the friction with all the air out and the damper setting fully open? A possibility could be tight bushing, I don't know how often it happens on the fox38 but I had the case on another brand, had the bushing burnished for 30€ and the sensitivity was much better (but annoyed to have to do it on a brand new expensive fork).

Wasn't great then or either. (In my opinion but no experience with the fork.) I took some Teflon lube and put around the dust seals and moved the forks up and down and that help on that front.

As for the equalization then, not sure what's going on, I just don't hear the hiss nor feel the give on the fork initially while the air is supposed to be passing. I may just try to utilize the warranty and send it to Fox and have them go through it when weather gets a little colder.

 

[Chrysaor]

As it's brand new it makes sense to use the warranty, you can maybe agree with Fox on a date where the turn over will be fast for you.
In the mean time you can let the bike upside down overnight and see if the sensibility is better just after and then slowly fades. This can be a hint that the bushings are too tight, preventing the oil to freely migrate along the stanchions during normal functioning.

 

[Chrysaor]

I don't have a 38 but I think there is a floating axle on it to prevent the lower binding. Maybe worth trying to reinstall the front well?

 

[Efrosty]

As it's brand new it makes sense to use the warranty, you can maybe agree with Fox on a date where the turn over will be fast for you.
In the mean time you can let the bike upside down overnight and see if the sensibility is better just after and then slowly fades. This can be a hint that the bushings are too tight, preventing the oil to freely migrate along the stanchions during normal functioning.

Thanks, will try that, they mentioned that as well. Also, didn't quite have my rear shock adjusted and going to just put some laps on it and see if that frees anything up.

Curious, is there any scenario you test on a trail for rebound? Today I'm going to ride and just adjust rebound out again and see if I ever get to the point to where I feel it pogo or snapping back. Yesterday I couldn't tell the different between 4 clicks out and all the way out, they indicated there may be a damper problem as well. Almost need a concrete surface and a row of 2x4's to hit and video or something similar.

 

[Efrosty]

I don't have a 38 but I think there is a floating axle on it to prevent the lower binding. Maybe worth trying to reinstall the front well?

I've loosed the bolt and axle and compressed several times for that.

 

[Chrysaor]

Thanks, will try that, they mentioned that as well. Also, didn't quite have my rear shock adjusted and going to just put some laps on it and see if that frees anything up.

Curious, is there any scenario you test on a trail for rebound? Today I'm going to ride and just adjust rebound out again and see if I ever get to the point to where I feel it pogo or snapping back. Yesterday I couldn't tell the different between 4 clicks out and all the way out, they indicated there may be a damper problem as well. Almost need a concrete surface and a row of 2x4's to hit and video or something similar.

I had the fox36 grip2 when I got my decoy in 2020 and I have found it difficult to setup. For my small level having high speed and low speed compression was more confusing than anything. In the end I just ran the recommended rebound setting for my pressure and it was working great.
On other forks, when I have only the low speed rebound it's the same strategy as you mentioned really, I try to have it as open as possible without being bounced back on small flat drops.
I found that this video from the Lost Co is a good starting point to help you understand the Grip 2 damper.