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BoXXer RC to WC conversion

jnooth

Monkey
Sep 19, 2008
384
1
Vermont Country
Is it as simple as just swapping internals? Someone had mentioned that RC lowers are different than RC2C and WC lowers?

long story short. I've always rode WC Boxxers and I am going to get a complete demo I that comes stock with an RC and my plan is to just convert it to a world cup. Hopefully this is possible.

thanks monkeys
 

William42

fork ways
Jul 31, 2007
3,908
634
should be fine. The RC lowers are different from the R2C2/WC in that the rebound shaft that presses into the bottom is smaller, so they inserted a plug in the lowers. You have to tap the little press fit piece out of the lowers on the damper side with a mallet, but once you've done that, the lowers are identical. The WC stantions are honed on the inside to make them slightly smoother, I dont know how much of a difference you'll notice with proper lubrication though.
 

Freeridin'

Monkey
Oct 23, 2006
316
2
Colorado
The WC stantions are honed on the inside to make them slightly smoother, I dont know how much of a difference you'll notice with proper lubrication though.
Where did you hear that?

Its an easy conversion, but expensive for what its worth.
You'll need the Solo air assembly, solo air top cap, mission control damper, and the rebound damper.

Or you could try an aftermarket cartridge for damping.
 

jnooth

Monkey
Sep 19, 2008
384
1
Vermont Country
thanks guys. I dont have any interest with aftermarket dampers. dont really mind spending the money for it. I have ridden world cups for a while and love them. I know how i like them set up, I know what I can expect from the fork, I know how to service it, and most importantly I love the way it feels. Also Srams customer service is second to none. They have proved to me in the past that if something goes wrong they will make it right and they will do it fast.

anybody else hear of the stancions being different?
 

baca262

Monkey
Aug 16, 2011
392
0
i believe you only need your air sprung stanchion to be without scratches on the inside so the air spring piston can seal. if the spring rubbed it bad, you could swap it for the damping side stanchion which shouldn't have any scratches or buy a new one.
 

ridiculous

Turbo Monkey
Jan 18, 2005
2,907
1
MD / NoVA
This.
I did this to my 2010 boxxer race and installed an avy cartridge. I did it when then stanchions were pretty new and made sure there were no scrapes internally. I've had zero issues with it thus far, just a bit of stiction.
 

Sonic Reducer

Monkey
Mar 19, 2006
500
0
seattle worshington
would it be cost effective to buy a used RC and convert it to air with new parts, rather than buying the same year WC? assuming reasonable fair market value and good condition. interesting thread, I am sort of in the market for a new fork. got a broken '07 888 WC Ti that the stanchions are not quite good enough condition to go avy cartridge and a 09 boxxer team that works good still but has tweaked lowers(plus it's flexy). I'm thinking to have that as a ready to go spare fork and go to a 35mm boxxer but was unsure of which one to go for. can definitely afford a RC now, and probably a r2c2, but can anyone give cliff's notes on a comparison between the 3 35mm boxxers?
 

William42

fork ways
Jul 31, 2007
3,908
634
Sure. Its not cost effective to go used RC and convert it to air. You will probably have seal and stiction problems. Here's the rundown:

Once you use a spring in a fork, its a bad idea to convert it to an airspring. It could be just fine, and you might never be able to tell the difference, and it also might lead to nothing but headaches. I know that for the older boxxer WC's (pre 2010) they used honed stantions to make them smoother, but even if they're not doing that now, the scoring a coil can cause (and frequently does) on the inside of a stantion isn't going to make things real smooth. If you're going the conversion route, your best bet is to buy new and switch to air before the fork has had a chance to be cycled.

Boxxer RC: pretty much the same damper as the older 2005-2009 moco boxxers. I think you get more clicks in the compression range, and its useable if not the best in the world. The rebound is slightly more problematic if ride really hard, since its ported and not totally consistent through the travel. It can be hard to find that sweet spot between good tracking and not packing up,, and not feeling like its bucking you or overly harsh or anything. Still, a decent chassis and reasonably light weight. As previously mentioned, the chassis is slightly different in that it has a little plug that you have to tap out if you decide you want to go avy or to r2c2.

Boxxer R2C2: same damper as the WC. Much more sophisticated, can be a butthole to tune if you have trouble tuning your suspension. I think of it as pretty straightforward, but it did take me a little while to figure out what the adjustments did, and given the number of them I've ridden that feel like absolute piss, I'm inclined to think that rockshox needs to come up with a better tuning guide to help people who don't know how to set them up. If you set it up well though, and make sure its had a good rebuild (I do my fork once a year, but QC out of the factory seems to be hit and miss, and occasionally you'll get one that is super sticky from the box. Better to just rebuild and get lube in the proper places if that's the case. Most of them don't need to be rebuilt right away though). I see no reason whatsoever to get custom tuning done if you can set up your fork decently, the damper is plenty capable. Also worth mentioning is the bottom out bumper that you can run (or remove if you want a more linear feeling, or cut it down to whatever size you like).

Boxxer WC is the same as the r2c2, but with air instead of coil. It has a sweet volume adjust knob that makes a pretty whopping difference. I haven't had mine long enough to know whether or not it will need more love/maint to keep it feeling as smooth as my old 2010 boxxer team, but so far its pretty ridiculously stiction free. Also worth mentioning that as long as you have the right tools, even if you're a hack mechanic, it should take max an hour if you're drinking heavily and not paying attention to it in order to rebuild. I have heard more people claiming that its stickier then the team etc, but I haven't personally noticed that on mine, neither of them (2010 boxxer team, 2012 boxxer WC) really has substantial or problematic stiction.
 

jnooth

Monkey
Sep 19, 2008
384
1
Vermont Country
very helpful! thanks. I plan to do the switch befor its ever used so I should avoid the problem of the coil doing damage to the incide of the stancion.
 

William42

fork ways
Jul 31, 2007
3,908
634
I should add: I haven't actually done a coil to air conversion, I was assured it would work in 2010 when I bought my 2010 team by SRAM, but I don't know if it is the same now. I was happy enough with the coil to not bother switching, and the only reason I'm on a WC now is because I got a good deal on it.
 

Sugar_brad

Monkey
Jun 20, 2009
328
6
I used my 2010 Boxxer team for a year and gutted everything and am now running a solo cartridge with an Elka damper and have had zero issues. I might call sram on Monday and see if they still hone the wc spring side stanchions and swap mine out because it us a little sticky in between rebuilds. I usually at least drop my lowers once a month for re-greasing.
 

oldskoolbiker

Monkey
Aug 19, 2005
357
0
Alexandria, VA
slightly off topic, but anyone have experience w/ the RC and the air cart?
I just set this up. Ran it last weekend. The setup passed my test performance wise. We'll see how it goes the rest of the season. I'm sort of a weight weenie and this setup is the lightest Boxxer setup. I had a friend who didn't want his air cart anymore because he wanted a spring. So I ended up doing some trading, and traded him the Boxxer Team spring setup for his Boxxer WC air setup. We traded stanchions and all so there would be no issues.
 

drastic.

Monkey
May 16, 2011
145
0
pleasanton, ca
I just set this up. Ran it last weekend. The setup passed my test performance wise. We'll see how it goes the rest of the season. I'm sort of a weight weenie and this setup is the lightest Boxxer setup. I had a friend who didn't want his air cart anymore because he wanted a spring. So I ended up doing some trading, and traded him the Boxxer Team spring setup for his Boxxer WC air setup. We traded stanchions and all so there would be no issues.

please keep this thread or me (thru pms) updated on how it ends up working out for ya w/ the RC damper in place. Feel any different vs. that of the coil in place (like maybe more progressive in the last part of the stroke, etc).

and can anyone confirm if the left leg stanchion DOES in fact have a honed out insides for less friction? Maybe I'll just swap my stanchions around, like someone suggested. Like you, I'm sort of a weight weenie (and this would put my DH bike down to around 35lb or right under), so for the cost, and adjustability in springrate, it makes it worth it to me.
 

oldskoolbiker

Monkey
Aug 19, 2005
357
0
Alexandria, VA
please keep this thread or me (thru pms) updated on how it ends up working out for ya w/ the RC damper in place. Feel any different vs. that of the coil in place (like maybe more progressive in the last part of the stroke, etc).

and can anyone confirm if the left leg stanchion DOES in fact have a honed out insides for less friction? Maybe I'll just swap my stanchions around, like someone suggested. Like you, I'm sort of a weight weenie (and this would put my DH bike down to around 35lb or right under), so for the cost, and adjustability in springrate, it makes it worth it to me.
It does feel different. If anything it feels more linear than the spring, I know it's strange to say. it seems to blow through the travel faster than than with the metal spring. So I bumped up a couple of clicks of compression. I did use the full travel of the fork, but I didn't feel any hard bottom outs, and I did a couple of 4ft drops to flat, and several big gap jumps. I also went through some pretty nasty rock gardens at a decent clip.

I did take the air cart apart and service it before I installed it. I couldn't tell that it was "honed" any anyway. But not sure how to tell just by looking at it. But I certainly would never put the air cart in a stanchion that had seen use by a metal spring.

I just got a 2011 Intense Uzzi setup for DH. The bike weighs 34.5 pounds with no compromised parts. All legit DH worthy parts (even full dual ply tires).
 

baca262

Monkey
Aug 16, 2011
392
0
It does feel different. If anything it feels more linear than the spring, I know it's strange to say.
not strange at all to me, i always found it weird that people say air springs are more progressive when they are more linear than the coils through the first 2/3 of the stroke...

p4pb3993110.jpg
 

baca262

Monkey
Aug 16, 2011
392
0
you're right, i expressed myself wrong here, i lack a better term to describe the feel. not being a native english speaker sucks sometimes. :(

the exerted spring force will have less rise in the first 2/3 of the stroke, this feels "more linear" to me.
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
not strange at all to me, i always found it weird that people say air springs are more progressive when they are more linear than the coils through the first 2/3 of the stroke...

View attachment 110293
That graph is not correct to my knowledge - I'm surprised no one questioned it on the PB article. The reason is that the air spring will always have a harder rate at the very start because you always have to break past a small amount of air preload on an air spring, and I think if they actually measured the rate, the air spring force (red line) would be higher than the coil spring for a little way after 0mm, before dropping below it.

This air preload and thus harshness at the start is unavoidable at least with current air spring designs - the negative air pressure will always have slightly less surface area to press against (the shaft takes up some surface area on the bottom of the air piston vs. the top) and this is needed to actually push the piston up towards topout - otherwise it wouldn't work as a spring.

Thus the air spring curve will usually be regressive-linear-progressive. A coil spring will always work and feel better, because it will:

a) Move more easily at the start of the stroke, allows for a true zero-preload setup
b) Provide more support in the middle of the stroke, making damper setup easier and be far less dependent on compression damping to hold the fork up
c) Allow use of all travel - yes the ramp up at the end on an air spring is nice, but because you generally need to run a little extra pressure to deal with point b), a correctly setup air spring in the mid stroke will often prevent you from using full travel. A more ideal setup is a linear coil spring with some form of bottom out cone or internal volume restriction towards bottom out.

I rode the 32 and 35mm air Boxxer for a long time and honestly didn't feel like it slowed me down or caused any issues, but after switching to a coil spring fork those are the things I noticed - and would probably stick with them in the future for those reasons.
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
I had a quick search to see if I could find a better graph, this one isn't perfect (everything is grossly exaggerated - for example the yellow air spring force barely increasing at all through the mid stroke haha) but it should help a bit more than that other graph.



If you follow the yellow line, you can see the three problems I pointed out. As I said it's grossly exaggerated, and hardly accurate, but gives you a better idea than what Manitou / PB posted.

I think the reason the yellow line is so exaggerated is to make the red line look better (one of Specialized's marketing curves by the looks :)) but the interesting thing is, if you ignore any comparison to the yellow line and just compare the red to the blue (coil), it helps illustrate what I said in point c) - if you increase air pressure to get closer to a coil in mid stroke support, you'll restrict your travel use at the end and also increase harshness at the start a little which I didn't mention.
 

baca262

Monkey
Aug 16, 2011
392
0
i know it's incorrect, i only thought of it as a rough approximation that shows why air springs tend to feel more linear.

on the preload and harshness off the top - i ran a heavily preloaded coil spring (somewhere around 35-40% sag without preload) and low air volume in my 888 for a while and never felt that harshness, i believe it is more due to stiction (felt it in the same fork with only air in it, not really only off the top because of the insane air preload since there was no negative spring but anywhere in the travel - i've been experimenting a bit). on the second thought, this might be because of the topout springs cancelled the preload force in the very beginning of the stroke.

anyhow, just wanted to say that a heavily preloaded spring/low volume setup emulates the air spring behavior pretty closely but it's messier to dampen. i really liked how it plowed and floated through everything but the linear firmer spring feels much more stable.

EDIT - that other graph is still incorrect since it starts with zero spring force for the air springs too but i'm nitpicking here :D

it's good that it's exaggerated since it's easier to understand the air spring's behavior.
 
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Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
Air springs don't feel more linear! I'm not sure where you're getting that.

Also if you're running a 'heavily preloaded' coil spring, you're completely missing the point of running a coil spring, and it's not a useful comparison. Obviously the solution is a harder spring which I'm sure you already know.

Air preload / air assist isn't the same as an air sprung fork either. Everything you talked about sounds like a total mess - apart from getting the right spring! :D
 

baca262

Monkey
Aug 16, 2011
392
0
i know, i know. i was only messing around with different possible setups to find out how stuff behaves, there were many messy moments :D

there is more ramp up in the coil spring and than in the air (in the midstroke), that's why i am saying air "feels more linear", the expression is technically wrong but i don't know how else to describe the feel. i'll just have to always write that in quotes to avoid liability :weee:

i have seen the light after my experiments and am now on an almost zero preload coil setup and it really works the best, everything else had a few nice traits but also had unresolvable issues. i was trying to get that stability motorcycles have where chassis almost doesn't move on the smaller bumps and the suspension does all the work but it seems you either need a heavier vehicle or awesome damping or both, none of which i have available atm.
 
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William42

fork ways
Jul 31, 2007
3,908
634
I can' disagree with most of what you said, but I can disagree with the "coil springs always feel better" statement. I like a little big of progression at the end of the stroke, and the ability to finely tune the springrate and change it depending on the trail and how I'm riding on a particular day definitely makes my WC feel better then my team.

But yeah, small bump isn't as good because there is a bit of air preload, and it does ramp up more, and it does have a flatter midstroke. But imo the midstroke is close enough that it is not a huge detriment, and the pluses outweigh the minuses
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
Fair call, different strokes for different folks.
The ability to adjust spring rate is definitely cool, and was something I really liked when I was a bit lighter (being between springs and such). Obviously the weight is another advantage for air, and the other nice thing is you never have to worry about coil rub / clang / isolators.

I rode air forks for many years and personally I still think for DH the coil wins out - even in terms of progression, there's many ways to get adequate damping or volume-based progression out of them towards end of stroke. The benefit in a coil fork is it's not linked directly to the spring, whereas on the air fork I found if I ran enough pressure for decent mid-stroke support, the ramp up would be too great at the end.

But the other thing I did say was I don't feel the air forks really slowed me down as such either, you can make them work just fine. I doubt there would be any significant time difference, for example between a similarly setup coil vs. air Boxxer - would be cool to see someone test it I suppose!
 

Sugar_brad

Monkey
Jun 20, 2009
328
6
Talked to Sram today. Tech confirmed that the 2010+ world cup stanchions are not honed like pre 2010.
 

descente

Monkey
Jul 30, 2010
430
0
Sandy Eggo
confirmed via BTI, they list a left and right stanchion but no air and coil specific stanchion. the damper side is tapered so whoever mentioned they were going to switch left and right stanchions: that won't work.
 

jnooth

Monkey
Sep 19, 2008
384
1
Vermont Country
so my plan was to swap them out before I ever ride the coil. but the sram tech said that even if its been cycled a few tmies you run the chance of the air not sealing properly due to micro scratches on the inside. I think my new plan is to grab a second set of stanchions (possibly fast suspension black ones) and start fresh and sell of the other ones.
 

Sugar_brad

Monkey
Jun 20, 2009
328
6
jnooth I am in the same situation. I have an extra coil seal head and coils and complete damper guts along with top caps so I might just pick up a set of lowers and crowns and have an extra fork.
 

William42

fork ways
Jul 31, 2007
3,908
634
to be fair, a sram tech would absolutely tell you that it wouldn't work and you have to buy new stantions - they want to sell you stuff, and they want you to buy a boxxer WC instead of their boxxer race. The more high end products they sell, the more they make. I have heard of many instances of people converting a used boxxer team to a boxxer WC, at least with the pre-2010 forks, and I see no reason why it wouldn't work on the 2010+ forks. Might as well try it before you order a new stantion.
 

baca262

Monkey
Aug 16, 2011
392
0
+1, i think it's bs you need a new stanchion for the air spring, if the spring gouged the stanchion so bad that the air piston won't seal, something was seriously wrong with your fork. i have an '05. 888rc that was used for all these years and there isn't a single visible scratch inside the stanchions, the springs got rubbed off a bit but the stanchions look flawless on the inside, they're a bit worn on the outside (the coating got thinner, looks kinda greenish).
 

FCLinder

Turbo Monkey
Mar 6, 2002
4,402
0
Greenville, South Carolina
So does anyone have all the RS part #s to convert the R2C2 to a WC? I am seeing the Solo Air Assembly part # as 114015385000. This is just all the internal parts.

Anyone else know what else is needed? I need to convert 2 forks.

Cecil
 

jnooth

Monkey
Sep 19, 2008
384
1
Vermont Country
as far as i can tell (although i have yet to do this but will be doing it soon) you need the solo air assembly as well as a new top cap with the air valve. I dont know the part # but the top cap is not very expensive.
 

Sugar_brad

Monkey
Jun 20, 2009
328
6
Cecil you also need the top cap assembly. The air spring assembly just comes with the pos/neg assembly and the seal head. Also just because you can't always see scratches with the naked eye you might not be able to get an optimum seal.
 

FBHO

Chimp
Mar 16, 2013
46
0
I realize this is a year old thread...but for the people who changed to air have you had any problems after having used the spring prior. As you can see from my other thread regarding the spring shaft in my R2C2 I am thinking for $20 more I can go air.
 
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FBHO

Chimp
Mar 16, 2013
46
0
Also, is there a major difference between the 2010 solo air assembly and a 11-13? I can't seem to find anything other then 010 solo airs..
 
Yeah the 2010 air assembly is larger and was changed to a slimmer compact air piston design for 2011+.
SRAM had a video out a while ago and basically the 2010 would possibly bind up at the lower crown clamps at full travel so the newer one does not. This was an issue if the consumer overtightened the crown bolts.
I also believe a foam ring was deleted from the 2011+ units so yeah the 2011+ is the way to go.