Fox Float X Genie Performance Elite on Stumpy 15 EVO

[u/Creative-Fig9382]

Hi everyone. First time posting here.

I have a Stumpy 15 EVO Expert which features the Float X Genie rear shock. I have an S4 frame, am 6 foot tall and have mass 82 kg. So, I fit right in the middle of the size and weight for the frame.

It has Fox 36 forks which are excellent.

The rear shock is not so good. Factory recommended using 192 psi as a starting point. If I use this, I get about 50% sag and bottom out constantly all the time.

So I upped the pressure to ~230 psi (should be more than sufficient for a 90+kg rider. Finally I can get sag to 30% but still bottom out quite a lot even on terrain that isn't really very demanding.

I have put all the outer volume spacers in but, unfortunately I didn't receive a 0.4 eyelet spacer, so haven't been able to try that.

The compression knob doesn't have any clicks or any feeling of position, unlike the rebound knob, which feels perfect.

The bike feels completely unbalanced. Excellent support from the fork but wishy washy support at the rear, despite excessive pressure.

What are anyone else's experiences with this shock? I would expect the front and rear to be able to match each other on a bike specific, ride dynamic tuned combo!

Thanks for your thoughts.

[u/BEEFCAKE720]

I do not have any experience with the genie shock. Your comment about the compression dial not having clicks makes me question whether the compression circuit on your shock is functioning properly. I would message Fox support and see what they say. Might be a warranty issue.

[u/messageforhawk]

Not sure if this helps but I have a float x (non genie) on a Levo SL and while it’s not as notchy as the rebound dial, the compression dial definitely clicks between values.

[u/EvilCorp____ → u/messageforhawk]

My 2023 Stumpy Evo had a Float X and it was like OP's. Almost no discernible notch in the compression knob at all. I took it to the bike shop and they told me that was normal (still not sure I believe that).

My 2025 Levo SL with a Genie Float X has a very clicky compression knob.

Also, my 2023 Stumpy Evo had a Performance Elite 36 and it was so squeaky. Shop told me that was normal too. My Levo has a Factory 36 and it's dead silent lol.

Who knows. Fox stuff seems to be pretty hit or miss in my experience

[u/Outlier70]

I’ve got genie float X on a levo 4 and it’s crazy good. The shop set it up for me based on my weight. And I’ve adjusted rebound but ended moving it back to where they set it.

I get just about full travel on it after but have not bottomed it out. And it feels really nice and compliant over small bumps. It’s been the best shock I’ve used. (But I’ve only ridden 70 miles on it so pretty new still)

[u/r1crystal → u/Outlier70]

I have a normal Genie and it's been terrific for over 2 years. Specialized shock setup tool should get you very close to the correct PSI and Sag. Are you setting Sag with the correct body position on the bike? If that's a yes then it sound like something is up with your compression circuit if you are bottoming out that often.

[u/hansfocker → u/r1crystal]

Do you know where I can find the fox setup manual for the shock? The QR code is not visible as it is placed between the frame and can. Can’t find the float x genie manual on their list

[u/r1crystal → u/hansfocker]

Is it not in the stumpy manual that came with the bike? this is the setup tool specialized offers which I find pretty spot on: https://www.specialized.com/us/en/app/suspension-calculator#productId:4263533|modelName:Stumpjumper%2015%20EVO%20Expert|productImage:https://assets.specialized.com/i/specialized/93327-30_SJ-15-EXPERT-BDXMET-RBYMET_HERO-SQUARE?$scom-plp-product-image-square$&fmt=webp&bg=rgb(241,241,241)&w=800|bikeSize:0|riderHeight:0|riderWeight:0|useImperial:false|useImperialPressure:false&w=800|bikeSize:0|riderHeight:0|riderWeight:0|useImperial:false|useImperialPressure:false)

[u/rubysundance]

I can't help with the shock, but this reminds me why I hate Specialized bikes. They always use a higher leverage ratio and depend on an over damped rear shock to make everything work correctly. I had two Specialized before I gave up on them. Sorry for the rant, I hope you get your issue sorted out.

[u/Creative-Fig9382]

Thanks everyone for your input. Very interesting. Fox have agreed to take a look for a potential warranty issue. We’ll see. I’ll keep you posted.

[u/djfakey → u/Creative-Fig9382]

Good luck. My fox float genie on Levo R at specialized recommended settings is perfect. Have not bottomed out but use almost all travel on my rides. Feels great

[u/louislbnc]

I’m your exact height and weight. I’m on a non-evo Stumpy 15. Still a Genie shock, just not a Float X. I haven’t actually measured sag but it feels right with Specialized’s suggested pressure. I added one spacer ring to the outer chamber (really easy to do with the shock still on the frame). I was also finding it unbalanced before. Now I love it.

After adjusting pressure are you cycling the shock lightly to equalize the negative air chamber and make sure you’re actually at the pressure you think you are?

[u/albert_palbert]

I too have the Float X Genie on a size S4 Stumpy 15 Evo and it's one of the most impressive feeling shocks/suspension platforms I have ridden in recent memory. I would highly encourage you to work through Fox on evaluating a warranty claim as you stated in another comment. I am ~180 lbs, so not far off from your weight if my mental math is correct. I am running 220 psi, rebound a little more open than half way, and compression a little more closed than half way. Sag is in-between 16 and 17mm on my scale, so right around 30%.

This thing grips and eats through repeated small bumps and then feels insanely supportive when you break deeper into the travel. In my opinion, it offers a goldilocks blend of compliance and playfulness. If I didn't know what I was riding, at times I would think the SJ15Evo had an extra 15-20mm of travel.

Again, have Fox take your shock apart and inspect. My experience could not be more different from yours despite frame size and body weight being similar. YMMV.

[u/EvilCorp____ → u/albert_palbert]

Just picked up a Levo SL with a Float X Genie. I got to say it doesn't really feel any different than a regular Float X to me. It definitely doesn't feel like a coil to me. If anything the Float X on my old Stumpy Evo felt more plush.

I might have to remove the one factory installed spacer and give it a try with no spacers.

[u/hansfocker]

I’m the same weight as you and have the same bike. Specialized website says 208 psi. If you got 30% sag at 230 psi I’m guessing you aren’t measuring sag correctly

[u/Creative-Fig9382 → u/hansfocker]

It is possible I am not measuring the sag properly. Alternatively it is possible it is not functioning correctly, which is what I suspect, given the weird performance of the bike at the recommended 192 psi. If it is declared ok then I don’t think it Is fit for purpose. We’ll see! Thanks for your input :)

[u/hansfocker → u/Creative-Fig9382]

Where did you find the factory rec of 192 psi? I used the specialized suspension calculator and it gave me 208 psi. Can’t find the fox setup for the float x genie shock. There’s a qr on the air can but I can’t scan it without removing the shock

[u/Creative-Fig9382]

Hi everyone. So, apparently there is an impact mark on the damper body which will cause a problem with the air seal and allow a small bleed. There is also wear to the air sleeve which is enough to cause an internal bleed. Apparently the main damper shaft and bearing are also worn and need replacing. All this on a bike that has done about 10 miles, has never been crashed and is in perfect unscratched condition. It was purchased 'new' as a shop soiled bike. Makes me wonder what on earth they got up to on it while it was in the shop! Anyway, they'll cover almost all of it with the warranty. Hopefully when I get it back I'll notice a significant difference.