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Why no more Coil forks?

Happymtb.fr

Happymtb.fr

Turbo Monkey
Feb 9, 2016
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An honest question here: what aspect of performance is superior with a coil fork?
Initial sensitivity on air fork is quite impressive now with all the efforts made to lower friction and the bigger negative chambers make for a very close to linear spring rate. Then you can adjust how progressive the fork is with tokens.
A coil spring would be more consistent over a wide range of temperature and altitude but I am not sure if it is a real problem or a theoretical one...
 
Udi

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
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Happymtb.fr said:
An honest question here: what aspect of performance is superior with a coil fork?
Initial sensitivity on air fork is quite impressive now with all the efforts made to lower friction and the bigger negative chambers make for a very close to linear spring rate. Then you can adjust how progressive the fork is with tokens.
A coil spring would be more consistent over a wide range of temperature and altitude but I am not sure if it is a real problem or a theoretical one...
Click to expand...
If you have to ask, then you haven't experienced an apples-for-apples comparison between them.

There is nothing theoretical about it, air springs have thus far all been noticeably less-than-linear (this is evidenced by anyone who has provided real calculated data for their air springs, eg. Vorsprung), and air springs ALWAYS have more friction than a coil spring. They also have other problems like varying friction profile over service life and air migration issues. Finally there's other issues like a restriction of lower volume limiting the amount of lubrication able to be used. None of the things you mention eliminate the problems, and things like lowering seal friction for example comes at the cost of greater air migration issues. If you haven't done back-to-back testing between spring types where all other factors are kept constant then of course it would be difficult to understand.

On the other hand, chassis build consistency has improved substantially in the two main brands over the last few years, so this has masked the pitfalls of air springs to some extent - but in a heavy-use environment, air forks always start feeling like rubbish much sooner than coil forks, even with current developments, adding to the fact that they are inferior to begin with.

If modern chassis technology was combined with coil spring technology that has existed for years, we'd actually have a step forward in suspension (at very competitive weights) - instead we're still scrabbing to achieve performance that was enjoyed 10 years ago by anyone who knew what they were doing.
 
Happymtb.fr

Happymtb.fr

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Feb 9, 2016
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Thank you @Udi for putting some light on my ignorance! I was kind of hoping for an answer from you since you seem to have great experience on the topic.

I have some experience with coil forks, I had a 36 Van R and stil own a 36 Van RC2. But is is true that I never had the opportunity to swap the spring from air to coil on the same chassis...

I did also make some air spring calculations but I don't have data / knowledge to tell how far the air spring curve can go before being considered non-linear or non coil like enough.

What about the lack of progressivity of coil forks? Dual spring rate would be a nice solution but I have only seen prototype for mtb.
 
Mo(n)arch

Mo(n)arch

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Dec 27, 2010
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Happymtb.fr said:
What about the lack of progressivity of coil forks? Dual spring rate would be a nice solution but I have only seen prototype for mtb.
Click to expand...
There is a tuning kit called AWK from a german guy for Rockshox forks. Seems to work quite well as it flattens out the spring curve to mimik a coilspring.



http://chickadeehill.de/
Seems to be only available in europe, though.

Edit: I didn't read your post well... SAR does progressive coil setups, but they seem not available to the public right now...
http://www.vitalmtb.com/photos/features/EUROBIKE-2017-Mountain-Bike-Components,10434/SAR-PSP-Spring-Tuning-Kit-for-BoXXer-Lyrik-Pike-and-FOX-36,109309/sspomer,2
 
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Nick

Nick

My name is Nick
Sep 21, 2001
24,036
14,650
where the trails are
Happymtb.fr said:
What about the lack of progressivity of coil forks? Dual spring rate would be a nice solution but I have only seen prototype for mtb.
Click to expand...
Some old Bombers, and even the Fox 40 coil/float hybrid, had a similar air chamber for end stroke tuning.

There is a whole generation of riders who have only been on air forks. The feel is the best they know. The changes to air were made to save weight and increase tunability. Chassis and CSUs are now much lighter and stronger, and though air forks work much better these days from the performance aspect there is nothing like a coil spring.
 
iRider

iRider

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Apr 5, 2008
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Udi said:
If modern chassis technology was combined with coil spring technology that has existed for years, we'd actually have a step forward in suspension (at very competitive weights) - instead we're still scrabbing to achieve performance that was enjoyed 10 years ago by anyone who knew what they were doing.
Click to expand...
Although I agree with what you say, I found myself in between spring rates in the good 'ol days of coil forks quite often. So it would be a necessity if coils make a comeback to not only offer 3 spring rates. I can see that shops don't like the idea of stocking endless amounts of springs to swap for the consumer because the OE forks come with one spring only. I guess that was also the death of coil rear shocks in the OE market. A suspension pump an some rubber bands or plastic pieces to stuff into your suspension and voila, even a mediocre shop can set up a bike w/o additional costs.
 
djjohnr

djjohnr

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Apr 21, 2002
3,013
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Happymtb.fr said:
Thank you @Udi for putting some light on my ignorance! I was kind of hoping for an answer from you since you seem to have great experience on the topic.

I have some experience with coil forks, I had a 36 Van R and stil own a 36 Van RC2. But is is true that I never had the opportunity to swap the spring from air to coil on the same chassis...

I did also make some air spring calculations but I don't have data / knowledge to tell how far the air spring curve can go before being considered non-linear or non coil like enough.

What about the lack of progressivity of coil forks? Dual spring rate would be a nice solution but I have only seen prototype for mtb.
Click to expand...
Yeah, some spring progressivity would be welcome, especially in shorter travel coil forks.
 
William42

William42

fork ways
Jul 31, 2007
3,916
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I've owned several forks of the same chassis that were air and or coil.

The only advantage that I ever found to air forks was that the spingrate was perfect for my weight and could be tuned based on the trail and how fast/hard I was riding.

Finding a coil fork that hit that correct balance was a breath of fresh air.
 
kidwoo

kidwoo

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Aug 25, 2003
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Mo(n)arch said:
There is a tuning kit called AWK from a german guy for Rockshox forks. Seems to work quite well as it flattens out the spring curve to mimik a coilspring.



http://chickadeehill.de/
Seems to be only available in europe, though.

Edit: I didn't read your post well... SAR does progressive coil setups, but they seem not available to the public right now...
http://www.vitalmtb.com/photos/features/EUROBIKE-2017-Mountain-Bike-Components,10434/SAR-PSP-Spring-Tuning-Kit-for-BoXXer-Lyrik-Pike-and-FOX-36,109309/sspomer,2
Click to expand...
That awk system is just a dual chamber added. I had an 888 with a similar setup. It kinda sucked. Definitely felt like a two-stage stroke. I took it out.

It just adds progressivity up to a point late in the midstroke and then gives way. And that's exactly what it feels like.
 
toodles

toodles

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Aug 24, 2004
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Remember when the big manufacturers all went from super expensive titanium springs in their top of the line forks to much cheaper air springs and how they passed on the material cost savings to us? And now you all want to pay extra to go back to coil? :clapping:

Actually, I'd like to see the real cost difference between a well made, ti sprung fork and a good air-sprung fork. As well as a realistic weight difference. I know on the 40s half the weight difference they promoted on the Float changeover was actually in the lowers, crowns and other bits, not the spring.
 
kidwoo

kidwoo

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toodles said:
Actually, I'd like to see the real cost difference between a well made, ti sprung fork and a good air-sprung fork.
Click to expand...
It's all the ti spring cuz you ain't gotta do shit for tolerances with a coil compared to a fiddly little air tight thing.

I've been pretty pleased with the RS air forks I've ridden as far as what usually makes air forks suck. I really really wish fox would figure that stuff out because you know.......actual damping adjustments are nice. I've ridden a few of the bad 36s now.......holy christ I swear I rode marzocchi and sid forks in 1999 that worked better than those things.

Are those air 40s really that bad? I've only ridden two but they were light years better than the 36s.
 
toodles

toodles

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kidwoo said:
Are those air 40s really that bad? I've only ridden two but they were light years better than the 36s.
Click to expand...
I've only ridden two Float 40s, but they felt crappy compared to my old coil 40. RS seems to do the airsprings better. I'm not terribly unhappy with either of Pikes, even before I chucked in the Luftkappes they were pretty good realistically.
 
kidwoo

kidwoo

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The two I've ridden were pretty late model (last year). I know there were some gripes with the first gen. I will say this though...I generally prefer really progressive frames but kind of linear forks. The air 40s did ramp up a little much IMO. But they weren't mine and I didn't really know the deets on how they were setup.

Either way, the bad 36s are horrendous. If so much of the 'new generation' of riders knew what they were missing, I think a coil conversion for those would do pretty well. But obviously fox wasn't selling any because they quit making them.
 
Jm_

Jm_

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It seems like it's been an impossible trifecta over the years to get a good cool fork with good damping, lubrication and chassis. When it was old bombers, it was piss poor crude damping, when it was manitou damping, it was piss poor internals and lubrication, to get a good low/high adjustable coil fork that won't need the semi bath changed every week is a unicorn.

Itd be nice if there was a modular way to set up a fork for coil or air. The lizards would never have it.
 
Udi

Udi

RM Chief Ornithologist
Mar 14, 2005
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Happymtb.fr said:
What about the lack of progressivity of coil forks? Dual spring rate would be a nice solution but I have only seen prototype for mtb.
Click to expand...
I don't think this is actually a significant concern, most people who think it is have not picked the right coil rate.

Some facts:
  • Air springs always have a higher initial rate, so the average spring rate (total force to bottom out) needs to be lower than a coil fork to get even close to the same sensitivity
  • Air springs have a lower spring rate in the middle of the curve if the average spring rate is matched to a coil spring, and the rate in the middle gets even lower if you make any compensation for sensitivity effects
  • Compression damping must be increased to get the same level of support or resistance to bottoming on an air spring, unless you make large sacrifices in sensitivity. This is the most apparent effect if you swap a coil spring and air spring out of an IDENTICAL chassis (including state of wear and thus sliding performance - I doubt many have actually made a properly objective comparison in this regard).
  • The clearance between stanchions and bushings has been increased in modern times to compensate for the extra friction of air springs, this reduces chassis longevity - but thankfully the consistency of tolerances has been improved so things haven't gone backwards completely. It should be clear that dropping a coil in a modern chassis is often different to the coil fork from 4-8 years ago though, because seal technology and chassis friction has improved a lot.
The end result of all this?
You can run a WAY firmer coil spring than most people think, and still have:
  • Significantly lower breakaway force than an air spring, thus better small bump absorption
  • Significantly better mid-stroke support (or rather, a complete removal of the lack of mid-stroke support that air springs generate), thus better chassis stability and geometric consistency
  • An ability to run less compression damping for a given level of support, which means more sensitivity / improved bump absorption - especially on direction changes, which directly translates to improved traction
Long story short, with a coil sprung fork (correctly sprung) you can actually have better traction / sensitivity and MORE (not less) bottom out resistance. Again, the reason most people don't realise this because they haven't CORRECTLY optimised each spring setup.

The only final point to add is, while the fact certainly stands that air springs are easier to tune to different rider weights, the linearity of a coil spring (in more ways than one due to compounding effects) mean that you can get away with a spring rate that isn't exactly right and still have good performance - whereas the inherent problems with an air spring means that you are often trying to tune within a very tight psi range to maintain sensitivity and support simultaneously.

Edit -
I meant to add, most people who make "dual spring rates" don't understand basic concepts of physics. If you pile a firm rate spring and a soft rate spring on top of each other as a replacement for a single rate spring, the resultant spring force curve is not progressive - it's actually just a linear average of the two spring rates UNLESS and UNTIL one of the springs physically coil binds. Even at that point, the average rate will only be increased as the result of however many individual coils bind (and thus become disabled) - so in reality all this "solution" does is give you an idea of the level of engineering competence many "industry people" possess. :)
 
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norbar

norbar

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@Udi your post makes me kinda angry (even though I think we've talked about it some time ago) it reawakens the inner tinkerer in me and now I have a strange urge to order a bunch of different springs and spend a weekend playing with damping and spring setup on my boxxer since I have that a feeling I could set it up better.

One thing that makes me wonder - going coil over air (as I did in 2016) would mean the ability to run less damping everywhere or only LSC damping for example? Since my AVA Boxx WC didn't work how I wanted I used to run a heavily overdamper and a bit oversprung setup.


@troy - you are just angry because now you have to remake your owlbike for 29'' wheels and find a place for an ebike motor since now only Old Germans and Gary will buy a 27.5'' idler bike.
 
slyfink

slyfink

Turbo Monkey
Sep 16, 2008
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Udi said:
I don't think this is actually a significant concern, most people who think it is have not picked the right coil rate.

Some facts:
  • Air springs always have a higher initial rate, so the average spring rate (total force to bottom out) needs to be lower than a coil fork to get even close to the same sensitivity
  • Air springs have a lower spring rate in the middle of the curve if the average spring rate is matched to a coil spring, and the rate in the middle gets even lower if you make any compensation for sensitivity effects
  • Compression damping must be increased to get the same level of support or resistance to bottoming on an air spring, unless you make large sacrifices in sensitivity. This is the most apparent effect if you swap a coil spring and air spring out of an IDENTICAL chassis (including state of wear and thus sliding performance - I doubt many have actually made a properly objective comparison in this regard).
  • The clearance between stanchions and bushings has been increased in modern times to compensate for the extra friction of air springs, this reduces chassis longevity - but thankfully the consistency of tolerances has been improved so things haven't gone backwards completely. It should be clear that dropping a coil in a modern chassis is often different to the coil fork from 4-8 years ago though, because seal technology and chassis friction has improved a lot.
The end result of all this?
You can run a WAY firmer coil spring than most people think, and still have:
  • Significantly lower breakaway force than an air spring, thus better small bump absorption
  • Significantly better mid-stroke support (or rather, a complete removal of the lack of mid-stroke support that air springs generate), thus better chassis stability and geometric consistency
  • An ability to run less compression damping for a given level of support, which means more sensitivity / improved bump absorption - especially on direction changes, which directly translates to improved traction
Long story short, with a coil sprung fork (correctly sprung) you can actually have better traction / sensitivity and MORE (not less) bottom out resistance. Again, the reason most people don't realise this because they haven't CORRECTLY optimised each spring setup.

The only final point to add is, while the fact certainly stands that air springs are easier to tune to different rider weights, the linearity of a coil spring (in more ways than one due to compounding effects) mean that you can get away with a spring rate that isn't exactly right and still have good performance - whereas the inherent problems with an air spring means that you are often trying to tune within a very tight psi range to maintain sensitivity and support simultaneously.

Edit -
I meant to add, most people who make "dual spring rates" don't understand basic concepts of physics. If you pile a firm rate spring and a soft rate spring on top of each other as a replacement for a single rate spring, the resultant spring force curve is not progressive - it's actually just a linear average of the two spring rates UNLESS and UNTIL one of the springs physically coil binds. Even at that point, the average rate will only be increased as the result of however many individual coils bind (and thus become disabled) - so in reality all this "solution" does is give you an idea of the level of engineering competence many "industry people" possess. :)
Click to expand...
OK, you've convinced me. where can I get a coil-spring retrofit kit for my Pike?
 
Mo(n)arch

Mo(n)arch

Turbo Monkey
Dec 27, 2010
4,441
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Udi said:
I don't think this is actually a significant concern, most people who think it is have not picked the right coil rate.

Some facts:
  • Air springs always have a higher initial rate, so the average spring rate (total force to bottom out) needs to be lower than a coil fork to get even close to the same sensitivity
  • Air springs have a lower spring rate in the middle of the curve if the average spring rate is matched to a coil spring, and the rate in the middle gets even lower if you make any compensation for sensitivity effects
  • Compression damping must be increased to get the same level of support or resistance to bottoming on an air spring, unless you make large sacrifices in sensitivity. This is the most apparent effect if you swap a coil spring and air spring out of an IDENTICAL chassis (including state of wear and thus sliding performance - I doubt many have actually made a properly objective comparison in this regard).
  • The clearance between stanchions and bushings has been increased in modern times to compensate for the extra friction of air springs, this reduces chassis longevity - but thankfully the consistency of tolerances has been improved so things haven't gone backwards completely. It should be clear that dropping a coil in a modern chassis is often different to the coil fork from 4-8 years ago though, because seal technology and chassis friction has improved a lot.
The end result of all this?
You can run a WAY firmer coil spring than most people think, and still have:
  • Significantly lower breakaway force than an air spring, thus better small bump absorption
  • Significantly better mid-stroke support (or rather, a complete removal of the lack of mid-stroke support that air springs generate), thus better chassis stability and geometric consistency
  • An ability to run less compression damping for a given level of support, which means more sensitivity / improved bump absorption - especially on direction changes, which directly translates to improved traction
Long story short, with a coil sprung fork (correctly sprung) you can actually have better traction / sensitivity and MORE (not less) bottom out resistance. Again, the reason most people don't realise this because they haven't CORRECTLY optimised each spring setup.

The only final point to add is, while the fact certainly stands that air springs are easier to tune to different rider weights, the linearity of a coil spring (in more ways than one due to compounding effects) mean that you can get away with a spring rate that isn't exactly right and still have good performance - whereas the inherent problems with an air spring means that you are often trying to tune within a very tight psi range to maintain sensitivity and support simultaneously.

Edit -
I meant to add, most people who make "dual spring rates" don't understand basic concepts of physics. If you pile a firm rate spring and a soft rate spring on top of each other as a replacement for a single rate spring, the resultant spring force curve is not progressive - it's actually just a linear average of the two spring rates UNLESS and UNTIL one of the springs physically coil binds. Even at that point, the average rate will only be increased as the result of however many individual coils bind (and thus become disabled) - so in reality all this "solution" does is give you an idea of the level of engineering competence many "industry people" possess. :)
Click to expand...

Damn you Udi, you always make me realize what I forgot over the years not using the stuff that I learned during school...
Thanks for the post above.
 
Happymtb.fr

Happymtb.fr

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Feb 9, 2016
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Thanks again @Udi for your answer!
I guess that I will have to give a coil a fair try in order to know how big the difference in performance is.

Edit: CRconception does not make the coil conversion kit any more...
 
Last edited:
Happymtb.fr

Happymtb.fr

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Some numbers calculated by Steve M from an interview on Nsmb:
https://nsmb.com/articles/steve-mathews-suspension-guru/
"However, to give some figures for a 160mm Pike.

Stock Pike: 70psi, 2 tokens. Initial spring rate 88lbs/in, dropping to 25lbs/in (lowest point) by about 1/3 stroke.

Luftkappe: 77psi, 0 tokens. Initial spring rate 59lbs/in, dropping to 30lbs/in (lowest point, also around 1/3 stroke)

(all forces/rates rounded to the nearest integer)

Both bottom out at the same force (270lbs). "

270lbs over 160mm yields 43 lbs/in as equivalent coil spring.
 
gemini2k

gemini2k

Turbo Monkey
Jul 31, 2005
3,526
117
San Francisco
What are your thoughts on the RV-1?

Udi said:
Some facts:Long story short, with a coil sprung fork (correctly sprung) you can actually have better traction / sensitivity and MORE (not less) bottom out resistance. Again, the reason most people don't realise this because they haven't CORRECTLY optimised each spring setup.
Click to expand...
 
Udi

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
knax said:
Does anyone know if these are the right parts for a coil spring conversion of a 2014/2015 650B Fox 40 Float?
https://www.ridefox.com/img/help/page744-U9SE/2016-40-VAN-203mm-Coil-Spring-Assembly.jpg
Fox does list these parts for a 2016 40 VAN, but they don`t mention wheel size anywhere...
Click to expand...
From memory that should work fine - the actual length of that rod *should* be the same for both 26 and 650 lowers, I believe the height difference is actually controlled by where the dropout is positioned on the lower leg. The length of that rod is related to the travel (203mm in both cases), it should not be related to the wheel size.

You should probably double check with your Fox distributor, but I'm pretty sure.
Open to correction as it's been a while since I switched.

slyfink said:
OK, you've convinced me. where can I get a coil-spring retrofit kit for my Pike?
Click to expand...
Sorry not something I know about (looks like a few options exist, and I remember a thread where someone fitted the coil guts from the old coil Lyrik successfully), just make sure whatever you get has considered spring isolation so you don't have to deal with noise.

gemini2k said:
What are your thoughts on the RV-1?
Click to expand...
I prefer bigger stanchions (probably have more to compensate for) but I think that thing looks real cool. Coil spring, decent weight, and though it's not on the website (still, which is kinda dumb), sounds like with the newer roughcut damper it could make for a pretty cool fork. I think Mr. Hacktastic knows more about it.

I'm not a fan of open bath or semi bath dampers though (aeration sucks), so in my book the damper upgrade would be compulsory. With that in, I'd definitely like to ride one.

norbar said:
I have a strange urge to order a bunch of different springs and spend a weekend playing with damping and spring setup on my boxxer since I have that a feeling I could set it up better.

One thing that makes me wonder - going coil over air (as I did in 2016) would mean the ability to run less damping everywhere or only LSC damping for example? Since my AVA Boxx WC didn't work how I wanted I used to run a heavily overdamper and a bit oversprung setup.
Click to expand...
I always found the AVA dampers on the soft side in terms of comp damping, not a lot of experience though. Which boxxer chassis are you on? The new chassis seems to slide much better regardless of spring (I think it might be mostly due to seals), so that might be a good upgrade - even just the seals if you are still running the older style.

I'd say less damping everywhere, keeping in mind even LSC has a lot of overlap anyway (it's just a name given to a dial that affects *some* part of the global curve). Varies from product to product so it's hard to make direct commentary, but in general I found right coil spring = can get away with less comp damping for same support vs. air.
 
norbar

norbar

KESSLER PROBLEM. Just cause
Jun 7, 2007
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Udi said:
I always found the AVA dampers on the soft side in terms of comp damping, not a lot of experience though. Which boxxer chassis are you on? The new chassis seems to slide much better regardless of spring (I think it might be mostly due to seals), so that might be a good upgrade - even just the seals if you are still running the older style.

I'd say less damping everywhere, keeping in mind even LSC has a lot of overlap anyway (it's just a name given to a dial that affects *some* part of the global curve). Varies from product to product so it's hard to make direct commentary, but in general I found right coil spring = can get away with less comp damping for same support vs. air.
Click to expand...
I'm on the 2010 boxxer though I must have been lucky since I didn't have some of the issues other people have when mounting avy dampers where the cardridge doesn't fit exactly and is a bit off center etc etc. The current tune is still same as it was with the air spring. I also have that thing in my boxxer that you put to prevent spring flexing (Not my idea, this happens every time I leave any of my bikes at my father's house (I have a small flat, don't judge). He's an old car mechanic and he gets bored easily. No idea it this gives me anything besides making my father happy.).

When ordering I told Craig I wanted a more heavily damped tune but I was 70kg not 76kg. I also have the mid valve version. Overall I'd like to keep ava only because I'm lazy and this not only means not frequent service but also easy service and if I bottom hard it's easier to machine broken damper parts instead of waiting months for our local RS dealer.
 
-BB-

-BB-

I broke all the rules, but somehow still became mo
Sep 6, 2001
4,254
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Livin it up in the O.C.
Udi said:
I don't think this is actually a significant concern, most people who think it is have not picked the right coil rate.

Some facts:
  • Air springs always have a higher initial rate, so the average spring rate (total force to bottom out) needs to be lower than a coil fork to get even close to the same sensitivity
  • Air springs have a lower spring rate in the middle of the curve if the average spring rate is matched to a coil spring, and the rate in the middle gets even lower if you make any compensation for sensitivity effects
  • Compression damping must be increased to get the same level of support or resistance to bottoming on an air spring, unless you make large sacrifices in sensitivity. This is the most apparent effect if you swap a coil spring and air spring out of an IDENTICAL chassis (including state of wear and thus sliding performance - I doubt many have actually made a properly objective comparison in this regard).
  • The clearance between stanchions and bushings has been increased in modern times to compensate for the extra friction of air springs, this reduces chassis longevity - but thankfully the consistency of tolerances has been improved so things haven't gone backwards completely. It should be clear that dropping a coil in a modern chassis is often different to the coil fork from 4-8 years ago though, because seal technology and chassis friction has improved a lot.
The end result of all this?
You can run a WAY firmer coil spring than most people think, and still have:
  • Significantly lower breakaway force than an air spring, thus better small bump absorption
  • Significantly better mid-stroke support (or rather, a complete removal of the lack of mid-stroke support that air springs generate), thus better chassis stability and geometric consistency
  • An ability to run less compression damping for a given level of support, which means more sensitivity / improved bump absorption - especially on direction changes, which directly translates to improved traction
Long story short, with a coil sprung fork (correctly sprung) you can actually have better traction / sensitivity and MORE (not less) bottom out resistance. Again, the reason most people don't realise this because they haven't CORRECTLY optimised each spring setup.

The only final point to add is, while the fact certainly stands that air springs are easier to tune to different rider weights, the linearity of a coil spring (in more ways than one due to compounding effects) mean that you can get away with a spring rate that isn't exactly right and still have good performance - whereas the inherent problems with an air spring means that you are often trying to tune within a very tight psi range to maintain sensitivity and support simultaneously.

Edit -
I meant to add, most people who make "dual spring rates" don't understand basic concepts of physics. If you pile a firm rate spring and a soft rate spring on top of each other as a replacement for a single rate spring, the resultant spring force curve is not progressive - it's actually just a linear average of the two spring rates UNLESS and UNTIL one of the springs physically coil binds. Even at that point, the average rate will only be increased as the result of however many individual coils bind (and thus become disabled) - so in reality all this "solution" does is give you an idea of the level of engineering competence many "industry people" possess. :)
Click to expand...

Thanks for the great explanation in words of what I've always just "felt".
Luckily, I've never owned my own Air fork (my "newest" fork is a '12 x-fusion Vengeance Coil) but I'm about to pull the switch on a new bike in the 170mm range (call it whatever style of bike you want ;) ) and I'm not too keen on going to an air spring based on the small amount of time I've had on friends air forks.
 
Happymtb.fr

Happymtb.fr

Turbo Monkey
Feb 9, 2016
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SWE
In an attempt to find out how much coil like my air springed forks are, I run into a bewilderment of disappointment so far...

My original intention was to convert a Yari (kitted with a real damper, if you wonder) but CRConception is not offering their kit any longer and the pricey kit from TFtuned fits Pikes only since RS decided to use a different threads on the top caps...

The next option is to convert a 36 Float from 2016. But Fox lists different models of CSUs for the 2015 models (which is the last year were 36s could be had in Van or Float versions) so that retaining ring and spring plate from a coil spring assy might not fit on a Float's CSU... further the Van plunger shaft assy is not available for sale any longer!

Are there any other options that I might consider based upon the 2 forks I have?
 
Udi

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
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@Happymtb.fr
Do you already own a 2016 Float? Spring rod should fit fine, from memory the plate and retaining ring sizes are the same. I don't have the time to double check, but I'd rather use factory parts if possible over the SAR kit - the Fox spring rod is very nice with its beautiful brown dildo attachment, and I'd rather skip the "progressive" spring for reasons explained above.

Another option could be checking if the old coil Lyrik internals will fit the Yari. I have a feeling with a little bit of ingenuity you could come up with coil conversions using original factory parts for either of your forks.
 
Udi

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
As I said, I'd rather use factory parts as a first option if they're going to work.
 
kidwoo

kidwoo

Artisanal Tweet Curator
Aug 25, 2003
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Udi said:
@Happymtb.fr
the Fox spring rod is very nice with its beautiful brown dildo attachment,
Click to expand...
Hey my dildo was white!

Probably a by product of british imperialism, like everything else.



here's the long dong version parts list if anyone wants them for a 36. I really really think the stanchion bottom cap is a different size on the floats nowadays..... Unfortunately I don't have an old van to check. There's no reason you couldn't bore out the one in the float though.

EDIT: this is NOT for a 160mm version. The spring rod will be way too long.

http://www.ridefox.com/img/help/page463-OP4rIB/2015-36-VAN-170-180mm-Coil-Spring-Assemblies.jpg
 
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