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Fork Upgrade DIY

How To: Convert your Fox 36 to Coil with Push ACS3

Words Cam McRae
Photos Cam McRae
Date Oct 19, 2017

I thought about taking this to a real mechanic for the install. Swapping a fork from an air system to coil sounded non-trivial to me, and I figured I could justify it by saying I needed my hands free to take photos. In the end I decided DIY was the way to go - despite not having a few of the required special tools on hand. What's worse than getting most of the way through a job only to find you are missing some essential proprietary tool? I looked at the comprehensive list of requirements Push provided and decided to throw my hat over the fence.


Push ACS3 Conversion

Is this before or after? I hadn't worked on a fork clamped into a work stand before. What a revelation. It works great to adjust the angle and height for the task at hand, to keep fluid in or let it flow out for example. 

Push provided a video of the process and, including swapping seals and doing a bit of an overhaul, the process took just over 14 minutes, while Darren Murphy from Push explained every step. How hard could it be? I did work as a mechanic in a bike shop, back in the age of V-brakes and full rigid bikes, so I'm not completely hopeless. I enjoy tinkering and building when things are going well and I'm not rushed so what the hell!

Push ACS3 Conversion

DO NOT DO THIS! I do own a 32mm socket but a friend grabbed it to have the chamfer machined down for me - about 8 months ago. You can really eff up your fork with an adjustable wrench. The top cap is aluminum and easily damaged and it's also easy to drive the wrench into your crown, scraping off black finish in the process. I was careful and it worked out but I will wait for the correct chamferless socket to tighten things down to the 200 lb torque rating. Please get the right tool for this task unless you are a jackass like me.

After releasing air and pulling the top cap it's time to undo the lower leg assemblies and remove the lower legs entirely. An oil pan would have been nice but I needed to improvise. 

Push ACS3 Conversion

I did have a few of the correct tools. A tap with a mallet releases the lower leg assemblies. 

Push ACS3 Conversion

And I was prepared to Mickey Mouse anything that was missing.

175 gram oilpan

This is a regulation 175-gram oil pan. It's the ultimate oilpan really. Since the fork (a 2016 Fox Fork 36 Float FIT4) was unused I wanted to preserve the fluid.

Once the lower leg assembly was off it was time to remove everything from the air spring side of the fork. The first step was to remove the spring retaining clip that keeps the air assembly in place. Darren recommends using a dental pick but I have a sharpened spoke with the end curled for a handle. This works for most jobs requiring a pick but in this case it was a trying task. Every time I got the edge of the clip peeled away from the inner stanchion wall it would snap back into place. I fought with it for at least 15 minutes before finally getting it out. A better tool, or maybe even a knife from the kitchen, would have made this task easy.

Push ACS3 Conversion

All the original components have been removed at this point and they sit to the right of the 2018 adapter. They aren't used again with the exception of the red rebound dial. 

Push ACS3

The correct assembly for a Fox 36 160mm fork. 

After draining all the fluid into the frisbee, I was a little worried I wouldn't have enough to replace it. I found a syringe that had never been used and to my surprise there was even more than the 80 mls recommended by Push. 

Push ACS3 Conversion

Every last drop. This was an uncontaminated syringe.  Photo - Luca McRae

After replacing the unused fluid all I had to do was strap everything back together.

Push ACS3 Conversion

An important step to remember. Push makes 7 springs for the ACS3 kit to accommodate rider weights from 120 to 230 lbs for a 160mm travel Fox 36.

Spring guide

I chose a blue spring but at 165lbs I'm on the light side of the range. I better pack lots of water. 

Push ACS3 Conversion

At the end you should have these parts left over. These could be reused but if you decide to go back to air you'll need a new CSU. (Crown Steerer Uppertube assembly) because the coil can scratch the inside of the upper tube. 

Push ACS3 Conversion

This is actually the completed fork. The only giveaway in this photo is the bottom out O Ring from Push that is grey rather than black. 

Taking an already excellent fork like the Fox 36 and converting it is not for the faint of heart. You'll immediately void your warranty, simply because these aren't Fox's parts, and you can't undo the job without an expensive replacement CSU. It will also cost you $389 US for the parts, without a rebuild kit. The fork I worked on also went from 2,100 grams to 2,360 - a little over half a pound.

If your 36 is on its last legs or there is some incurable problem with the air spring, this might be just the ticket. Or if you are simply looking for the incomparable feel and performance of a coil spring with the added bonus of Push's Air Bump Stop cartridge that allows you to adjust the bottom out between 5 and 50 psi. In theory, this means you should get the excellent small bump performance, traction, and smoothness of a coil with the bottom out resistance of an air spring. Remember that Marzocchi Bomber you used to ride? Let's see if this can feel as buttery! Testing begins now.

For more, including the excellent install video, check out the Push ACS3 here...

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Comments

rnayel
+1 Cam McRae
RNAYEL  - Oct. 19, 2017, 9:13 a.m.

Great write up Cam. I was in the market for a 29er coil 160mm fork with a factory warranty, so I bought an Ohlins RXF 36.

Reply

cam@nsmb.com
+1 RNAYEL
Cam McRae  - Oct. 19, 2017, 9:29 a.m.

Awesome Rachid. How does it deal with bottom out resistance?

Reply

rnayel
0
RNAYEL  - Oct. 19, 2017, 10:18 a.m.

My understanding is that there is an air valve on the bottom of the right leg to control bottom out. Honestly, I haven't made time to play around with it (or mount it for that matter). I picked it up on Saturday and it's been sitting there staring at me every time I get home.

You're welcome to do a teardown for NSMB if you like before I get it mounted, the frame is off getting wrapped and won't be back until next week.

Reply

awesterner
0
awesterner  - Oct. 19, 2017, 9:51 a.m.

Nice to see this kit out there!  Question, can the fork be put back to air successfully?  Back in the day when guys converted Air to Coil (ghetto conversion) the inside of the stanchion stood to get a bit marked up from the spring which could cause issues with the air shaft if one ever wanted to switch back.

Reply

cam@nsmb.com
+1 awesterner
Cam McRae  - Oct. 19, 2017, 10:06 a.m.

Same issue exactly apparently. 

"You'll immediately void your warranty, simply because these aren't Fox's parts, and you can't undo the job without an expensive replacement CSU."

Reply

awesterner
+1 Cam McRae
awesterner  - Oct. 19, 2017, 1:28 p.m.

Cheers, I should have read between the lines haha ;-)

Reply

LoamtoHome
0
Jerry Willows  - Oct. 19, 2017, 10:25 p.m.

Let us know how it rides compared to the air.  I'm quite curious.

Reply

cam@nsmb.com
0
Cam McRae  - Oct. 20, 2017, 12:31 a.m.

Will do Jdub!

Reply

velocipedestrian
0
Velocipedestrian  - Oct. 20, 2017, 1:21 p.m.

If it's anything like my old 26" Lyrik it'll be a winner.

Though I'm sure a modern air spring is superior to the ~2011 jumble of parts I ditched.

Reply

JBV
0
James Vasilyev  - Oct. 20, 2017, 11:44 a.m.

this will be an interesting review what with all the air vs coil shock debates and choices. an Ohlins coil fork review would be welcome too.

Reply

Vincent66
0
Vincent66  - Oct. 21, 2017, 10:05 a.m.

If you want to get rid of the wooden box full of vinyls in the back ground, let me know ...

Reply

cam@nsmb.com
0
Cam McRae  - Oct. 22, 2017, 9:02 a.m.

Thanks Vincent but they still get spun in the dungeon. Or they will again once I get my turntable repaired.

Reply

AlanB
0
AlanB  - July 2, 2018, 2:55 p.m.

Glad to see I'm not the only one that considers a Frisbees® essential to shop work.

Reply

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