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fox 40 coil

ebarker9

Monkey
Oct 2, 2007
456
6
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.
Thanks. I had a measurement for the top spacers of 1.35" and they're definitely a loose fit so that makes sense. And you're right about the silicone and neoprene. Maybe some of the alternative materials (EPDM, polyurethane, nitrile) would be better suited.

Your PTFE guide is making a noticeable difference?
 

kidwoo

Celebrating No-Pants Day
Aug 25, 2003
22,522
2,201
In my pants
Have you tried thicker oil?
I've used all kinds of shit over the life of the thing. I haven't specifically tried "thicker than what I used last time" since I noticed they leak too soon after replacing.

The world fanny pack party is at northstar this weekend so I'll be home doing bike stuff. I'll figure out what's up.
 

jonKranked

Press Button, Receive Stupid
Nov 10, 2005
58,100
6,208
media blackout
I've used all kinds of shit over the life of the thing. I haven't specifically tried "thicker than what I used last time" since I noticed they leak too soon after replacing.

The world fanny pack party is at northstar this weekend so I'll be home doing bike stuff. I'll figure out what's up.
do you pack them with slick honey before you install the lowers?
 

lobsterCT

Monkey
Jun 23, 2015
173
203
Thanks. I had a measurement for the top spacers of 1.35" and they're definitely a loose fit so that makes sense. And you're right about the silicone and neoprene. Maybe some of the alternative materials (EPDM, polyurethane, nitrile) would be better suited.

Your PTFE guide is making a noticeable difference?
It helped very significantly in reducing noise for my fork. I only have a bit of use one afternoon on the part though, so long term durability is still being determined.

The "about plastics" link at McMaster after you select "raw materials" has a good breakdown of properties for a pretty broad assortment of plastics. Tensile strength, compression strength, machinability, heat tolerance, oil/chemical tolerance, etc.
 
Dec 5, 2019
1
0
HELPPPPPP !! I have a 2015 specialized demo 8 with some pretty old fox 40 rc2 forks (the spring ones) and I wasn’t getting any travel, turned out someone put an innertube on the spring instead of shrink wrap and it got stuck, so I sorted that with proper heat shrink after spending hours getting the spring out,



So...

I now have travel but nowhere near the full 200mm about half of that at max,

I thought it was from having a spring what is too stiff however after trying my friends bike with a yellow spring which is stiffer than my green I can still get full travel on his with ease, mine seems real firm in comparison,



I since noticed I should have 3 air volume spacers yet I have two and then it’s as though someone has just put two headset spacers in there Instead of the 3rd spacer, could this be the cause to my issue of not getting full travel maybe !?
 

mykel

Turbo Monkey
Apr 19, 2013
2,036
686
sw ontario canada
If you remove the spring, do you get full travel?
That would be the first thing I would check - whether the fork compresses fully nice and smooth like.
 

kidwoo

Celebrating No-Pants Day
Aug 25, 2003
22,522
2,201
In my pants
Probably got too much air in your coil fork air chamber coil spacer coil negative chamber coil coil air spring.
 

englertracing

Monkey
Mar 5, 2012
254
98
La Verne
So,
Those arent volume spacers but travel spacers, they are made so you can clip them on below the negative spring, its possible that one is down there but it wouldnt be why your not getting half travel.

Does it have an rc2 pre fit cartridge?
If so it could be overfilled and be preventing full travel. However if its just the open bath then this is not a possibility.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
16,352
1,192
01776
If your damper's dumped, I do have a dumpy damper- an open bath 40R damper sitting in a box somewhere. You can have it for shipping if your fancy cartridge is toast.
 

Matty112

Chimp
Jan 22, 2020
5
2
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!!
Hi! I am very curios if you managed the conversion and how it is compared to before?
I had a Fox 40 coil before, that I loved, and now I have a fox 40 Float that doesnt feel as good as the coil one. So I am planning to do the same as you if you can recommend it?
Thanks!
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,776
929
Hi! I am very curios if you managed the conversion and how it is compared to before?
I had a Fox 40 coil before, that I loved, and now I have a fox 40 Float that doesnt feel as good as the coil one. So I am planning to do the same as you if you can recommend it?
Thanks!
Been running the 40 float chassis converted to coil for many years now, feels great as you'd expect (for very long intervals consistently), and feels substantially better than every air 40 including current. Like you I went from the coil to the air and it was a huge downgrade, converted and never looked back. Fox ruined a great fork by putting an air spring in it.

I did use the later spring rod (with the brown dildo which goes through the spring) and it seems to keep things quieter. I also use the same heatshrink in the same place as Fox used it (center) but I use a piece around 40% longer. I used a float topcap (lighter) with self-made preload spacing, but you can just used the factory preload adjustable coil topcap if you wish also.
 

Matty112

Chimp
Jan 22, 2020
5
2
Been running the 40 float chassis converted to coil for many years now, feels great as you'd expect (for very long intervals consistently), and feels substantially better than every air 40 including current. Like you I went from the coil to the air and it was a huge downgrade, converted and never looked back. Fox ruined a great fork by putting an air spring in it.

I did use the later spring rod (with the brown dildo which goes through the spring) and it seems to keep things quieter. I also use the same heatshrink in the same place as Fox used it (center) but I use a piece around 40% longer. I used a float topcap (lighter) with self-made preload spacing, but you can just used the factory preload adjustable coil topcap if you wish also.
Thanks Udi!
I will go for this conversion, I will look up all the parts that I need to do this, including the brown "dildo" :-) This later spring rod is from the standard Fox 40 coil from around 2013?
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,776
929
Yes the 2013 (and also late 2012) 40 spring rod are correct. The long brown part is integrated with the spring rod/piston assembly itself (non-removeable), so it will be obvious immediately if you have the right one or not.

There are not many parts needed from memory, just the spring rod, spring, and optionally the topcap / preload spacers if you desire them. As I said I just used the Float topcap and self-made preload spacers.

As a bonus the entire fork is much lighter than the older coil models (and pretty close to the inferior performing air) since a lot of the weight saving is in the new chassis: lowers / crowns / stanchions.
 

Matty112

Chimp
Jan 22, 2020
5
2
Yes the 2013 (and also late 2012) 40 spring rod are correct. The long brown part is integrated with the spring rod/piston assembly itself (non-removeable), so it will be obvious immediately if you have the right one or not.

There are not many parts needed from memory, just the spring rod, spring, and optionally the topcap / preload spacers if you desire them. As I said I just used the Float topcap and self-made preload spacers.

As a bonus the entire fork is much lighter than the older coil models (and pretty close to the inferior performing air) since a lot of the weight saving is in the new chassis: lowers / crowns / stanchions.
Yes finally I have ordered all the needed things.

One thing I am thinking about is that the coil version had a hydraulic bottom out system which mine will not have. Have you, or anyone else, added more oil to the coil (or damper) side to get more ramp up towards the end of the stroke?
Thanks
 

buckoW

Turbo Monkey
Mar 1, 2007
1,599
374
Champery, Switzerland
Yes finally I have ordered all the needed things.

One thing I am thinking about is that the coil version had a hydraulic bottom out system which mine will not have. Have you, or anyone else, added more oil to the coil (or damper) side to get more ramp up towards the end of the stroke?
Thanks
I ran mine without the hydraulic bottom out cone. I just ran a stock cartridge from an air 40.
I wouldn’t add more oil for ramp up since it’s a closed cartridge.
 

Matty112

Chimp
Jan 22, 2020
5
2
I ran mine without the hydraulic bottom out cone. I just ran a stock cartridge from an air 40.
I wouldn’t add more oil for ramp up since it’s a closed cartridge.
Thanks for the info!
Then it sound like it will be fine as it is. It really doesn´t matter if its a closed cartridge or not, you can still add oil to the spring side to get more ramp up, we do this all the time on our motocross bikes. But would be good the hear if someone has tried it on the Fox 40 with good results or not :-)
 

buckoW

Turbo Monkey
Mar 1, 2007
1,599
374
Champery, Switzerland
A progressive spring or a hydraulic bottom out cone would be better solutions, in my opinion if you wanted more ramp up. I went back to air for the ramp up and I size the bushings more often now to keep the fork supple. @Udi would be a good info source for this. His coil 40 sounds pretty dialed.
 

englertracing

Monkey
Mar 5, 2012
254
98
La Verne
Thanks for the info!
Then it sound like it will be fine as it is. It really doesn´t matter if its a closed cartridge or not, you can still add oil to the spring side to get more ramp up, we do this all the time on our motocross bikes. But would be good the hear if someone has tried it on the Fox 40 with good results or not :-)
Iv used 50 or 75cc just for the sake of having more oil, and i didnt notice a difference you may need 100+cc

I know some people were into removing the standard fox bottom system as it is quite "effective" maybe too "effective"
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,776
929
You can use the older HBO RC2 cartridge from 2011-2013 coil sprung 40 (as sold from factory) if you need more bottom out resistance. It's roughly the same in terms of function compared to the 2014+ RC2 cartridge apart from that.

It really doesn´t matter if its a closed cartridge or not, you can still add oil to the spring side to get more ramp up, we do this all the time on our motocross bikes. But would be good the hear if someone has tried it on the Fox 40 with good results or not :-)
You can't treat it like a moto fork and put 1L of oil in there because modern MTB forks don't use circlip-retained separate oil seals, it'll just blow the seals out.

I do run 60-75mL for better lubrication and longer service intervals (safe on coil due to large volume in both legs), but as englert says, you'd easily need over 100mL+ to do what you suggest and I wouldn't recommend it. Make sure you run the right spring rate for your weight and you shouldn't really have to worry about this. Unlike an air fork you can easily go up a spring rate without things getting harsh since the behavior is more linear and friction is very low.
 

englertracing

Monkey
Mar 5, 2012
254
98
La Verne
The newer cartridge has a different mv piston with moar/thinner rebound shims, and ive had the shit laying around for a few years and havent gotten to trying the new mid piston yet, ive got one in my newest fork but currently my collar bone is only held togeather by tec screws and water heater strap so i wont get to try it out for a while.
 

englertracing

Monkey
Mar 5, 2012
254
98
La Verne
Yes finally I have ordered all the needed things.

One thing I am thinking about is that the coil version had a hydraulic bottom out system which mine will not have. Have you, or anyone else, added more oil to the coil (or damper) side to get more ramp up towards the end of the stroke?
Thanks
Whaddaya weigh matty?
 

Matty112

Chimp
Jan 22, 2020
5
2
Whaddaya weigh matty?
I am pretty light weight at 70 kg (154 pounds) so I might not need more oil or a bottom out system (I hope) I previosly run a purple spring on a 2013 Fox 40 which felt perfect and I have the purple spring left so I will use that one. About adding oil I thought that because it is a converted Float I hoped that the seals where made for higher pressures. On 888 and 380 Marzocchis they have used about 100 to 125 ml of oil in the coil leg to achieve more ramp up, but Marzocchis have quiet a bit softer spring so I can see why its needed there. I will start with 75 ml and see how it works.
Nice to hear your ideas! Thanks
(I will probably not grind down my spring though :-) )