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fox 40 coil

madpharma

Chimp
Oct 16, 2018
19
0
I have the option to convert my 2018 float40 to coil, but last minute doubting made me think if anyone knows if its possible to mount the spring in the damper stanction and the damper in the spring stanction?

to be able to revert back to air if needed so you dont lose resale value or if I just want to go back

Thanks!
 

HAB

Chelsea from Seattle
Apr 28, 2007
10,493
848
Seattle
I have the option to convert my 2018 float40 to coil, but last minute doubting made me think if anyone knows if its possible to mount the spring in the damper stanction and the damper in the spring stanction?

to be able to revert back to air if needed so you dont lose resale value or if I just want to go back

Thanks!
The damper side foot nut is much larger diameter than the spring side one, so you can't swap sides in the lowers, but the stanchions are the same so you can swap those side to side.
 

madpharma

Chimp
Oct 16, 2018
19
0
The damper side foot nut is much larger diameter than the spring side one, so you can't swap sides in the lowers, but the stanchions are the same so you can swap those side to side.
So it could be done ?

As fas as I know the problem when going coil is damaging the dimple that conects the positive and the negative chambes+ scratching the inside of the tube, thats why I ask if I can swap them when installing them.
 

madpharma

Chimp
Oct 16, 2018
19
0
And a related question

Anyone knows the weight difference between complete coil spring sistem (coil included)and the air spring sistem
 

csermonet

Monkey
Mar 5, 2010
940
122
Don't know the weight difference, but it is certainly going to be quite a bit. Also, good luck finding parts to do the conversion. Fox doesn't make a coil version of the 40 at all anymore, even in OE, thus they don't have parts to service it/do a conversion.
 

jonKranked

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Nov 10, 2005
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Don't know the weight difference, but it is certainly going to be quite a bit. Also, good luck finding parts to do the conversion. Fox doesn't make a coil version of the 40 at all anymore, even in OE, thus they don't have parts to service it/do a conversion.
would it possibly work to just retrofit the entire spring side (stanchion + internals) from an older coil version of the fork? or are the lowers different enough that the stanchion and foot bolt assembly wouldn't be compatible?
 

madpharma

Chimp
Oct 16, 2018
19
0
I already got the parts needed to retrofit it, I weighted the spring and got 480grs aprox, Im going to fit it tomorrow and try it this weekend.

Thanks!!
 

madpharma

Chimp
Oct 16, 2018
19
0
By the way, Im around 74 kg naked, aroung 77 or 78 with helmet and all the gear, do I need the green spring or the blue that I got would be enough??
 

jonKranked

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Nov 10, 2005
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By the way, Im around 74 kg naked, aroung 77 or 78 with helmet and all the gear, do I need the green spring or the blue that I got would be enough??
at 78kg (170lbs) you would want the blue. per fox:


40 COIL SPRING SETTINGS
FOX Part #​
Spring Rate​
Color Code​
Rider Weight (lbs.)​
039-05-070​
30 lb/in​
Black​
< 90 – 120​
039-05-071​
35 lb/in​
Purple​
120 – 150​
039-05-072​
40 lb/in​
Blue​
150 –180​
039-05-063​
45 lb/in​
Green​
180 – 210​
039-05-074​
50 lb/in​
Yellow​
210 – > 240​
 

englertracing

Monkey
Mar 5, 2012
160
31
La Verne
I found tall with a short bike, you need to size up 1 spring to green even back when I was 170lbs, and with the new gonzo front end crop of dh bikes you I have to size down to blue at 185lbs
 

csermonet

Monkey
Mar 5, 2010
940
122
would it possibly work to just retrofit the entire spring side (stanchion + internals) from an older coil version of the fork? or are the lowers different enough that the stanchion and foot bolt assembly wouldn't be compatible?
That is possible, the diameter of the tubes hasnt changed(you can swap the new crowns vs old crowns) and the foot nut should be the same. (no sense in having to develop a new fastener when you can use the same one and not spend money for tooling, manufacturing, etc etc). the problem is buying the parts to convert an air to coil, but if youre just going to buy a complete old 40 and harvest the spring/tube, that is a different story.
 

csermonet

Monkey
Mar 5, 2010
940
122
I found tall with a short bike, you need to size up 1 spring to green even back when I was 170lbs, and with the new gonzo front end crop of dh bikes you I have to size down to blue at 185lbs
to translate, newer bikes tend to need a lower spring rate in the fork than previously because of the extreme head angles(comparatively to the olden days)
 

lobsterCT

Monkey
Jun 23, 2015
154
162
at 78kg (170lbs) you would want the blue. per fox:


40 COIL SPRING SETTINGS
FOX Part #​
Spring Rate​
Color Code​
Rider Weight (lbs.)​
039-05-070​
30 lb/in​
Black​
< 90 – 120​
039-05-071​
35 lb/in​
Purple​
120 – 150​
039-05-072​
40 lb/in​
Blue​
150 –180​
039-05-063​
45 lb/in​
Green​
180 – 210​
039-05-074​
50 lb/in​
Yellow​
210 – > 240​
to add to the Monkey knowledge bank- There is also an orange spring heavier than those. Avalanche put a damper in my float and also converted it to coil. He speculated the orange was developed for E-bike 40's.

In any case he was able to order it from the parts department at fox, and it works good for Clydesdale use except for being a little short in the tube. He stacked the 3 black spacers shown in photo at the top of the spring. The fork felt great, but made a lot of noise with the spring rattling in the tube. I designed a simple white plastic piece to try to hold the top of the spring centered in the tube to use instead of the 3 black spacers. The bottom of the spring is already centered by a fox piece. The new part is fabricated out of recycled PVFE for chemical/oil resistance and very easy machining qualities. spring1.jpgspring2.jpgspring3.jpg

Going to take the bike out after work today, just at local trails, and see if the fork is quieter now.
 

jonKranked

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Nov 10, 2005
54,752
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to add to the Monkey knowledge bank- There is also an orange spring heavier than those. Avalanche put a damper in my float and also converted it to coil. He speculated the orange was developed for E-bike 40's.

In any case he was able to order it from the parts department at fox, and it works good for Clydesdale use except for being a little short in the tube. He stacked the 3 black spacers shown in photo at the top of the spring. The fork felt great, but made a lot of noise with the spring rattling in the tube. I designed a simple white plastic piece to try to hold the top of the spring centered in the tube to use instead of the 3 black spacers. The bottom of the spring is already centered by a fox piece. The new part is fabricated out of recycled PVFE for chemical/oil resistance and very easy machining qualities. View attachment 136492View attachment 136493View attachment 136494

Going to take the bike out after work today, just at local trails, and see if the fork is quieter now.
the spring rattling noise was a common issue. the solution is some manner of sleeve / tubing in the center of the coil.
 

ebarker9

Monkey
Oct 2, 2007
453
2
Only thing that worked for me with the spring noise was going to a section of heat shrink so thick and long (ha ha) that it added significant friction to the functioning of the fork. 3D printed a top centering cap but didn't notice any significant change. Currently running air mostly because of the noise but would like to go back if someone ever solves that problem.
 

kidwoo

Celebrating No-Pants Day
Aug 25, 2003
22,017
1,697
In my pants
I'm totally hijacking this bitch

Anybody ever ovalize their lowers? I'm going through seals way too fast. It's about the only thing I can think is going on.

I've been riding this fork for like 5 years so not out of the question I guess.
 

jonKranked

Press Button, Receive Stupid
Nov 10, 2005
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I'm totally hijacking this bitch

Anybody ever ovalize their lowers? I'm going through seals way too fast. It's about the only thing I can think is going on.

I've been riding this fork for like 5 years so not out of the question I guess.
define "too fast"

unless it's super localized your fork would probably be eating bushings too. use some calipers and measure several points around the radius.
 

kidwoo

Celebrating No-Pants Day
Aug 25, 2003
22,017
1,697
In my pants
Too fast = a fast that is excessively high in magnitude

Gotta change the seals, might as well measure.






But that wasn't my question now was it.........................

Hmmm?


HMMM????
 
Last edited:

HardtailHack

used an iron once
Jan 20, 2009
2,272
163
to translate, newer bikes tend to need a lower spring rate in the fork than previously because of the extreme head angles(comparatively to the olden days)
I wondered about this so with a slacker HA you can run a lower spring rate? For hucking it should be the opposite as the spring is acting less directly but I don't know how frontal impacts would dictate the spring rate needed.

Also, there is PTFE heatshrink if people are looking for slippery chemical resistant heatshrink, it's not cheap though.
 

lobsterCT

Monkey
Jun 23, 2015
154
162
I missed the glory days of coiled 40's, so I'm just starting to get familiar with them.

Just heat shrink didn't do much for mine, but it sounds like Sandwich is onto a simple solution.


Recycled PTFE was $21.66 for a 12" long 1.5" OD rod. I ended up with the spring end center drilled for 3/8" instead of 1/2" as shown in the drawing. Preload end is center drilled for 1/2" . Everything is probably a little bit different with other fork/spring combos. My set up is a 17 float 27.5 and orange spring.




PVFE.jpg
 

ebarker9

Monkey
Oct 2, 2007
453
2
Considering replacing the center heat shrink with some neoprene or silicone tubing. McMaster sells 1.375 OD tubing that might work as a press fit into the Fox 40 stanchion or require a little bit of material removal. ID could be drilled out to fit the spring. Figuring a short length to minimize any kind of binding issues. Wondering if the areas of the spring above/below might still make contact with the inside of the stanchion.
 

jonKranked

Press Button, Receive Stupid
Nov 10, 2005
54,752
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Considering replacing the center heat shrink with some neoprene or silicone tubing. McMaster sells 1.375 OD tubing that might work as a press fit into the Fox 40 stanchion or require a little bit of material removal. ID could be drilled out to fit the spring. Figuring a short length to minimize any kind of binding issues. Wondering if the areas of the spring above/below might still make contact with the inside of the stanchion.
i don't think either of those materials would hold up for a long enough time for it to be worthwhile
 

lobsterCT

Monkey
Jun 23, 2015
154
162
The preload mechanism has an od of 1.400" below the rubber o-ring seal. Assuming it is the same part for kashima/black stations, it seems 1.375 would be a slip fit.

At McMaster if you choose raw materials/rubber/rubber/about rubber, there is a chart that suggests silicone would not do well with the fork oil.

No data on neoprene, but it seems like that would get chewed up into particulate by the spring.
 

ebarker9

Monkey
Oct 2, 2007
453
2
i don't think either of those materials would hold up for a long enough time for it to be worthwhile
That was a concern as well, although if it disintegrates at least it's in the spring side and wouldn't be too much of a nightmare to clean.

Alternately, building multiple layers of shrink wrap could help. The factory supplied wrap isn't thick enough to really deaden the sound.