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Problems with my 2010 Boxxers

Banshee Rider

Turbo Monkey
Jul 31, 2003
1,452
10
My question is - WHY are RS/Sram making and shipping these new forks without oil or lube in them?? WHY WHY WHY?? :wacko: Anyone 'in the business' care to offer an explaination?

It seems pretty unacceptable to me yet everyone seems to accept it...
RS/SRAM isn't assembling these forks in Chicago, they're done in massive production runs overseas. It would make financial sense that the QC checkpoint is in the same location as manufacturering, meaning the last set of hands to touch your fork were probably in Asia. Once the shipment hit the US, it was likely just pushed down the distribution channel to consumers. I'm confident that RS/SRAM is now well aware of the shortage of oil in production, and has/will take it up with the foreign partner(s) they work with. I'm also confident that it'll be quite a while before the changes make their way all the way back down the same channel in the form of a fingertip of grease and 10 more cc's of oil to you and I. So in the mean time, to point out of the elephant in the room (again), it makes the most sense to do the half hour job yourself.
 
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Andrei

Chimp
May 15, 2009
19
0
Back on my Race. I've solved (half of the) knocking issue by adding a few thin plastic spacers between the bottom out spring unit and the C-clip that was holding it. The is no more knocking from the left (coil) side of the fork and I've returned to the proposed height (16-14mm left) for the spring+spacers (currently yellow spring+2 preload spacers). I've lubed it all up and it's pretty smooth but I keep hearing some noise from the damper unit (that I haven't open so far). Will the R'N'R Super Slick grease will be any better than my Weldtite TF2? The fork is still a bit sticky and I can't get 30% of preload, although I use all the travel when riding.
 
May 30, 2005
323
0
A$$pen
RS/SRAM isn't assembling these forks in Chicago, they're done in massive production runs overseas. It would make financial sense that the QC checkpoint is in the same location as manufacturering, meaning the last set of hands to touch your fork were probably in Asia. Once the shipment hit the US, it was likely just pushed down the distribution channel to consumers. I'm confident that RS/SRAM is now well aware of the shortage of oil in production, and has/will take it up with the foreign partner(s) they work with. I'm also confident that it'll be quite a while before the changes make their way all the way back down the same channel in the form of a fingertip of grease and 10 more cc's of oil to you and I. So in the mean time, to point out of the elephant in the room (again), it makes the most sense to do the half hour job yourself.
That said, I sent my 08 Team in for warranty a couple months ago and it came back with no oil in the damper side. I'm pretty sure mine wasn't sent overseas for warranty.
 
Dec 11, 2007
140
0
Lawn Dart Training Center
Just picked up a 2010 World Cup. Pulled the lowers off before install to check for proper grease/oil. Everything was good in my particular fork.
Bushings are very tight, compared to my 09. Have to run the rebound wide open at least until it breaks in. Reminds me of the break in period on a manitou dorado, really tight out of the box. We'll see.

Only real complaint is how hard the adjusters are to turn. Chewed up my fingers getting the initial settings dialed in!!
 

Supa8

Monkey
May 3, 2002
493
0
Middle of MA
Got around to taking my 2010 WC down to give it a look see as my bike is now done as of last night. The fork had oil and very little running grease. gave it a full lube job and it is very plush and smooth.

ISIS crank bolt threaded in is the way to go to to remove the dampening side lowers. Adjusters do their thing and loosen up quickly.

With where this thread at now it would be nice to start seeing some fork set ups listed maybe in a new thread to start take a more positive turn.

I am running the below. Just under 160 in gear

48 PSI
1 turn bottom out

13 clicks LSC
3-4 Clicks HSC
1.5 turns LSR from full fast
9 clicks HSR from full fast

Will see how this setup works out at Windham this weekend. Will be sporting a new Ghost white Corsair Maelstrom so give a shout if anyone is at the hill this weekend. We will have Wachusett brews at the tent if anyone gets thirsty...
 

madzappa

Chimp
May 20, 2009
14
0
Deep Cove
Any suggestions for me, I'm wondering if the bushing are damaged?

The fork(10 Team) unknowingly at the time, shipped bone dry. After abusing them for 2 days in the bike park, they went stiff and there was burnt black rubber on the coil side stanchion.

After a complete tune everything was awesome again, but turned to crap in about 4hrs. The problem... is the coil side(left) does not hold the 40ml of bath oil, and the Judy Butter I pack into the seals smears away quickly. Basically the oil is leaking to the bottom, then pushing up into the coil cartridge... and staying there. I know this because when I drop the lowers, only a smidgen of thick goo drips out. The stanchion does not wiggle to suggest worn bushings, but instead feels overly tight, so I don't know??

BTW, the right leg is good and stays buttery smooth, just note the damper cartridge shipped very low in oil, I had to add about 40mm.

Should I try to warranty these? They are un ridable after 4 hrs, no exaggeration. I've had them for two months and tune the left leg twice a week, it's becoming rather brutal.
 
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argent81

Chimp
Jun 25, 2009
1
0
Yesterday arrive my wc 2010 I wanted to ask if the differences from fully open to fully closed in HSR are many.... because in car park i don't feel any diferences.... the lsr work fine and i feel the difference....
 

RUFUS

e-douche of the year
Dec 1, 2006
3,480
1
Denver, CO
Yesterday arrive my wc 2010 I wanted to ask if the differences from fully open to fully closed in HSR are many.... because in car park i don't feel any diferences.... the lsr work fine and i feel the difference....
High speed is called high speed for a reason meaning you can't really feel it by bouncing around in the parking lot.

Take the fork on a proper trail and get back to us.
 

go-ride.com

Monkey
Oct 23, 2001
548
6
Salt Lake City, UT
Any suggestions for me, I'm wondering if the bushing are damaged?

The fork(10 Team) unknowingly at the time, shipped bone dry. After abusing them for 2 days in the bike park, they went stiff and there was burnt black rubber on the coil side stanchion.

After a complete tune everything was awesome again, but turned to crap in about 4hrs. The problem... is the coil side(left) does not hold the 40ml of bath oil, and the Judy Butter I pack into the seals smears away quickly. Basically the oil is leaking to the bottom, then pushing up into the coil cartridge... and staying there. I know this because when I drop the lowers, only a smidgen of thick goo drips out. The stanchion does not wiggle to suggest worn bushings, but instead feels overly tight, so I don't know??

BTW, the right leg is good and stays buttery smooth, just note the damper cartridge shipped very low in oil, I had to add about 40mm.

Should I try to warranty these? They are un ridable after 4 hrs, no exaggeration. I've had them for two months and tune the left leg twice a week, it's becoming rather brutal.
A few things that might help.

1. These forks that are getting the black smears on the legs probably have damaged seals. If the seal has heated up enough to melt onto the leg then it needs to be replaced.

2. Judy Butter is too thick IMO. I've been using Slick Honey and it works better. Keep in mind that in addition to lubing the seal and wiper you have to completely fill the gap between them. If you don't the lube on the seal and wiper will get moved into the gap very quickly.

3. IMO if you have a 2010 Team you should not leave that fork upside down. When upside down it allows the lubricating oil to drain into the spring chamber and mix with the spring grease creating a big mess and not allowing the oil to lube the seal and wiper.

4. Use a maximum of 15cc for oil bath in both legs whether it is a WC or Team.
 

Gridds

Monkey
Dec 18, 2008
266
0
Great Britain
Is it just me that thinks that the ability of the oil to mix with and become absorbed by the grease (wether turned upside down or not) and thus rendering the performance of both useless is a bit of a design fault?

Surely there must be a better way of doing things in the fork internals?
 

General Lee

Turbo Monkey
Oct 16, 2003
2,860
0
The 802
Is it just me that thinks that the ability of the oil to mix with and become absorbed by the grease (wether turned upside down or not) and thus rendering the performance of both useless is a bit of a design fault?

Surely there must be a better way of doing things in the fork internals?
oddly enough, if you put the lube oil where it belongs (higher up in the legs where the bushings are, and not sitting in a puddle at the bottom where it does no good) then it doesn't seem to get absorbed. I'm not having any problems and my fork is about 6 weeks out from its lat real service.
 

William42

fork ways
Jul 31, 2007
3,915
651
oddly enough, if you put the lube oil where it belongs (higher up in the legs where the bushings are, and not sitting in a puddle at the bottom where it does no good) then it doesn't seem to get absorbed. I'm not having any problems and my fork is about 6 weeks out from its lat real service.
That is odd. I suspect spies and terrorists.
 

Big J

Monkey
Jul 18, 2005
421
0
Chicago
No offense taken. The manual does show the correct way to do it. However if you look at the HSR knob there are two gaps that will line up with the adjuster unit flats. If you like the knob up you can put a 24mm wrench on without removing the knobs. If you do this you will over-loosen the HSR assembly and damage it. I'm guessing some who have had "non functioning adjusters" have done this and damaged the fork.

Unfortunately, I do not have replacement parts yet, but I do have spare forks. What parts are damaged on your fork? Maybe I can work something out with RS.

The changes I am making are "race prepping" the forks to be properly lubricated and changing the compression valving to function better and allow for a larger range of adjustment. This is something we offer to anyone that purchases a 2010 Boxxer Team or WC from Go-ride for a small fee, and will do for anyone else for $50 + shipping.
I serviced my Team and found it tough to guess'tmate 65 inch pounds when installing the rebound side to the lowers so I ordered one of these to 'Snap On' to the torque wrench..... http://buy1.snapon.com/catalog/item.asp?P65=&tool=all&item_ID=2343&group_ID=272&store=snapon-store&dir=catalog

I know most of you have your tool kit dialed but a lot of this is new to me so I thought I'd share. I also ordred a 6 point 24mm socket for the top end since it's something you don't think about until it comes time to torque that down and 12 point just doesn't cut it.

J
 
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RUFUS

e-douche of the year
Dec 1, 2006
3,480
1
Denver, CO
I serviced my Team and found it tough to guess'tmate 65 inch pounds when installing the rebound side to the lowers so I ordered one of these to 'Snap On' to the torque wrench..... http://buy1.snapon.com/catalog/item.asp?P65=&tool=all&item_ID=2343&group_ID=272&store=snapon-store&dir=catalog

I know most of you have your tool kit dialed but a lot of this is new to me so I thought I'd share. Also, I went ahead and ordred a 6 point 24mm socket for the top end since it's something you don't think about until it comes time to torque that down and 12 point just doesn't cut it.

J
Looks like you ordered a 24mm crows foot instead.
 

Big J

Monkey
Jul 18, 2005
421
0
Chicago
Looks like you ordered a 24mm crows foot instead.
That was my intent........I have a 24mm open & closed end wrench but my hand lacks a proper torque meter.

Point taken.....so I did edit the orig.

J
 
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RUFUS

e-douche of the year
Dec 1, 2006
3,480
1
Denver, CO
That was my intent........I have a 24mm open & closed end wrench but my hand lacks a proper torque meter.

J
Disregard, misread your post. Sounded like you said that you had ordered a snap on torque wrench, not one to snap onto the torque wrench.
 

Big J

Monkey
Jul 18, 2005
421
0
Chicago
No worries, I appreciate everyone's input on this subject since I would have been f'd if wasn't for the rm Boxxer threads......keep the good info flowing.

J
 

selebrin

Chimp
Nov 23, 2007
30
0
Seattle
Back on my Race. I've solved (half of the) knocking issue by adding a few thin plastic spacers between the bottom out spring unit and the C-clip that was holding it. The is no more knocking from the left (coil) side of the fork and I've returned to the proposed height (16-14mm left) for the spring+spacers (currently yellow spring+2 preload spacers). I've lubed it all up and it's pretty smooth but I keep hearing some noise from the damper unit (that I haven't open so far). Will the R'N'R Super Slick grease will be any better than my Weldtite TF2? The fork is still a bit sticky and I can't get 30% of preload, although I use all the travel when riding.
good job man! so the solution i've proposed actually worked out for you! ;)
haven't tried it with mine yet - just being lazy and waiting for my Team...
try the same on the damper side... you just need to take the rebound shaft off no need to drain the damper oil...

post some photos man!!! and yes call Sram and try to get a free Team!!!

cheers!!
 

go-ride.com

Monkey
Oct 23, 2001
548
6
Salt Lake City, UT
Why? Theres plenty of room for more, expecially in the spring side.
You can put more in the spring side of a Team, but it just ends up mixed with the spring grease and creates a big mess. I've found that the slick honey on the seals, wipers and bushings is the real key to a smooth boxxer. Those that are having serious stiction issues I believe to be coming from the damper seal between the upper and lower legs. I'm working on a fix for that.
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
I agree with TomBigmac.

You DEFINITELY want to run more than 15cc in the spring side of the race/team fork, that NOT being done at factory is part of what causes them to become dry quite quickly.

The spring side of the race/team fork has much more volume, therefore won't suffer from excessive ramp up like the solo air or damping legs will given more oil. Also, given that the spring grease will absorb some oil, it's good to have extra in there. I'd recommend 40cc, I believe the official figure from sram is about that (someone can confirm I'm sure).

If you are anal, I'd also suggest wiping some of the excess spring grease from the spring, which should help reduce how much oil is absorbed, leaving more to do what it should be doing (lubing the bushings).

Everything else go-ride said is spot on though, packing the seals with slick honey or RNR super slick is important.
 

davep

Turbo Monkey
Jan 7, 2005
3,276
0
seattle
...If you are anal, I'd also suggest wiping some of the excess spring grease from the spring, which should help reduce how much oil is absorbed, leaving more to do what it should be doing (lubing the bushings)...
Agree 100%. There is usually enough grease on the spring to last 10 years and several spring swaps. Any more than a thin film just ends up sitting in clumps on the spring coils doing nothing good...
 

madzappa

Chimp
May 20, 2009
14
0
Deep Cove
I'm still not sold on the 40ml. You want the bath oil to float in between the upper and lower bushings. The space is the same size on each leg. Problem is, on the coil side it drips out to the bottom somehow and then gets pushed up into the coil cartridge. Whether it's 15ml or 40ml, it doesn't stay where it supposed to.
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
I'm still not sold on the 40ml. You want the bath oil to float in between the upper and lower bushings. The space is the same size on each leg. Problem is, on the coil side it drips out to the bottom somehow and then gets pushed up into the coil cartridge. Whether it's 15ml or 40ml, it doesn't stay where it supposed to.
You're not sold because you don't understand how it works. The bath oil doesn't float between the upper and lower bushings, it floats wherever it wants to. Gravity will force it to sit at the bottom of the lowers, and whatever gets to the bushings is whatever gets splashed up by the stanchions moving down into the lowers.

Therefore, the more the merrier. The issue on the damper and solo air legs is that there is less volume in the lowers, therefore if you run too much oil, you will get excessive ramp up from volume reduction. No such issue on the coil side, plus the issue of the spring grease absorbing some oil equates to more oil only being a good thing.
 

Yukonrider

Chimp
Jun 21, 2007
38
0
Marquette MI
So I hate to jump on the band wagon here, but my Boxer is kaput as of now.

I did not pull it apart out of the box, it felt fine, I just rode it. it has maybe 12 days on in, that's probably less than 60 runs at an average of probably a minute 30 seconds a run.

So anyways at a race this weekend i started to notice some oil on the stanchions on the spring side. No big deal seals aren't that much. Then oil turned into a more greasy substance that I had to rub off, and I did after every run. Then race day it was running fine, with the greasy stuff, then a few runs into practice it started to get REAL sticky. Think new seals without grease plus a little. My friends kept asking if my lockout was on.

That's where I'm at now. I called RS and left a message, and hope to get a response tomorrow. Its just a bummer, I leave on Thursday night to go on a trip to New York, so it will be hard to get any packages..

Take that as you will. I like the fork, this is just a bummer..
 
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DHperu

Monkey
Apr 14, 2005
240
0
Hey Guys, i live in south america so its really hard to get my hands on Judy Butter/Slick Honey grease etc..

is there any other type of grease that i can use inside the boxxer? what type of grease should i look out for?

thanks!
 

madzappa

Chimp
May 20, 2009
14
0
Deep Cove
You're not sold because you don't understand how it works. The bath oil doesn't float between the upper and lower bushings, it floats wherever it wants to. Gravity will force it to sit at the bottom of the lowers, and whatever gets to the bushings is whatever gets splashed up by the stanchions moving down into the lowers.

Therefore, the more the merrier. The issue on the damper and solo air legs is that there is less volume in the lowers, therefore if you run too much oil, you will get excessive ramp up from volume reduction. No such issue on the coil side, plus the issue of the spring grease absorbing some oil equates to more oil only being a good thing.

Ok that is what one would think, but the common problem is that oil gets pushed into the cartridge and stays there = no lube for either bushing.

And if you check the other side, the oil does in fact stay between the bushings.
 

davep

Turbo Monkey
Jan 7, 2005
3,276
0
seattle
Ok that is what one would think, but the common problem is that oil gets pushed into the cartridge and stays there = no lube for either bushing.

And if you check the other side, the oil does in fact stay between the bushings.
There is no cartrage on the spring side..nowhere for the oil to go and get 'stuck', other than the excess grease mixing with the very small amount of bath oil.

The oil does not 'stay' between the bushings. Bushings do not seal against the stanchions. If they did, you would have WAY too much friction in the system for the fork to function correctly. Oil is constantly draining away from the bushing area due to gravity. It gets replenished when the fork is compressed and the stanchion displaces oil up, around itself in the void between the stanchion and casting....where the bushings are. Every fork compression splashes/sloshes and pushes oil up the outside of the stanchion, coating the stanchion (that will then rebound up through the bushings) and toward the bushings themselves.

On the spring (coil) side there are several things going on that do not exist on the damper side primarily due to the open stanchion. 1) The displaced oil can be forced to either the inside or outside of the stanchion (there is a larger volume to the inside and thus lower pressure and the oil will tend to go this route). 2) The displacement volume (of the stanchion) is going to be 0.1 of the displacement on the damper side. 3) The surface area in contact with (needed to be lubed by) the oil is ~4X as much as on the damper side (inner and outer stanchion, 'seal' head, spring plunger shaft/assembly, and of course the spring and its pound and a half of grease).

Once you realize the differences in the two sides of the fork, it becomes quite obvious why the same oil volume does not work as well on the coil-spring side of the fork.

Removing the masses of excess grease should help some by allowing the oil to stay at a low enough viscosity to flow/splash as it was designed. Of course this will require an occasional check/relube.

Adding more oil to the spring side is also an extremely obvious choice. This at least partially counteracts the other differences in the two sides of the fork, with ZERO downsides.

With some very off the head numbers, extended to compressed volume ratio in the Damper side is on the order of 9 : 1. On the spring side, it is closer to 1.6 : 1. You would need to massively increase the volume of oil (0.5 liters maybe) in the spring side to see anywhere near the pressures that the damper side sees every day.

Doubling or trippling the oil volume in the spring side should have no ill effects on the new Boxxer. This has been done/used on the last Boxxer version by many people for a loong time. I have yet to hear of anyone having any issues with too much oil in the coil spring side leg....
 

go-ride.com

Monkey
Oct 23, 2001
548
6
Salt Lake City, UT
You're not sold because you don't understand how it works. The bath oil doesn't float between the upper and lower bushings, it floats wherever it wants to. Gravity will force it to sit at the bottom of the lowers, and whatever gets to the bushings is whatever gets splashed up by the stanchions moving down into the lowers.

Therefore, the more the merrier. The issue on the damper and solo air legs is that there is less volume in the lowers, therefore if you run too much oil, you will get excessive ramp up from volume reduction. No such issue on the coil side, plus the issue of the spring grease absorbing some oil equates to more oil only being a good thing.
There's two ways to look at the spring leg in the Team. One is that yes you can put more than 10 or 15cc of oil in it without it hydraulically locking. So you there is a theory that more oil is better. The other way to look at it is that any amount over 15cc will get forced into the spring chamber when the fork gets deep into its travel. When this happens it mixes with the spring lube and creates a big mess that fills the bottom of your fork. I know this because I’ve serviced at least a dozen of the 2010 boxxers. I also have one Team and WC as test forks. IMO it’s the slick honey on the wiper, seal, and upper bushing that does most of the lubricating.
 

go-ride.com

Monkey
Oct 23, 2001
548
6
Salt Lake City, UT
Does anyone had problems with the HSC?
Mine just went blank. No damping at either max or min compression..

Haven't had time to open it out yet but anyone heard of this before?
If you are doing "parking lot" tests then HSC is tough to feel. If you are actually riding a rough trail then it should be pretty obvious if it is adjusting or not. It is possible that the nut that holds the HSC circuit has started to come loose and is not allowing the adjuster to pre-load the HSC spring.
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
There's two ways to look at the spring leg in the Team. One is that yes you can put more than 10 or 15cc of oil in it without it hydraulically locking. So you there is a theory that more oil is better. The other way to look at it is that any amount over 15cc will get forced into the spring chamber when the fork gets deep into its travel. When this happens it mixes with the spring lube and creates a big mess that fills the bottom of your fork. I know this because I’ve serviced at least a dozen of the 2010 boxxers. I also have one Team and WC as test forks. IMO it’s the slick honey on the wiper, seal, and upper bushing that does most of the lubricating.
I think the mistake you're making is assuming the oil has some set behaviour, it doesn't; as the fork goes up and down the oil is being splashed around all over the place (hence - splash lube / semi bath). So even if there's a small amount in there, it's going to end up in the stanchion at some point. With my suggestion (of using more oil - again SRAM themselves recommend 40cc for the spring leg!) and perhaps wiping some excess grease off the spring, you'll be far more likely to have a properly lubed fork.
 

CountryBoy

Monkey
Nov 10, 2008
163
0
Reno, NV
I am thinking of getting either a 2010 Race or Team, but can't quite decide. I just like to set my suspension up and ride and not mess with the adjustments, so I am not sure if I will ever really use all the knobs on a team. Any opinions or suggestions are welcome.
 

nugget

Monkey
Jul 4, 2006
187
0
somewhere near a town
If you are doing "parking lot" tests then HSC is tough to feel. If you are actually riding a rough trail then it should be pretty obvious if it is adjusting or not. It is possible that the nut that holds the HSC circuit has started to come loose and is not allowing the adjuster to pre-load the HSC spring.
Yep, the test was done on the trails. Tried full in and full out no difference. What should i look for when i remove the damper?
 

madzappa

Chimp
May 20, 2009
14
0
Deep Cove
There is no cartrage on the spring side..nowhere for the oil to go and get 'stuck', other than the excess grease mixing with the very small amount of bath oil.
I understand there is no cartridge, it just sounded better than 'semi-sealed stanchion with a spring in it' :)

None the less, that stanchion with a spring in it, is gobbling up every bit of oil put in there. I've had this fork apart at least 8 times just to add oil and drain teh goo out of the stanchion. Gorides advice is a good idea, bare minimal grease on the spring and I'm going to try 40CC of 7 weight. Hopefully some of that oil will drain back into the lower. Also found some the recommended Slick Honey, it definitely runs smoother than Judy Butter.
 

go-ride.com

Monkey
Oct 23, 2001
548
6
Salt Lake City, UT
Yep, the test was done on the trails. Tried full in and full out no difference. What should i look for when i remove the damper?
The easiest way to remove the comp damper and service the HSC unit is to:
1. Loosen the upper crown pinch bolt on the damper side
2. Remove both LSC & HSC adjuster knobs. The LSC is a 4mm allen, and the HSC has two very small set screws that are accessed from the outter rim of the adjuster.
3. Use a 24mm socket or wrench to unthread the damper.
4. Slowly pull it out of the leg allowing the oil to drain back into the leg.

At the bottome of the damper is a black nut (10mm I believe), I'm guessing this nut may be loose. If this nut is loose then the HSC adjuster will not be properly preloading the shim stack. If it is loose tighten it to snug, not crazy tight as it is aluminum and so is the shaft it threads onto. If it is not loose then something was mostly likely mis-assembled.
 

go-ride.com

Monkey
Oct 23, 2001
548
6
Salt Lake City, UT
I think the mistake you're making is assuming the oil has some set behaviour, it doesn't; as the fork goes up and down the oil is being splashed around all over the place (hence - splash lube / semi bath). So even if there's a small amount in there, it's going to end up in the stanchion at some point. With my suggestion (of using more oil - again SRAM themselves recommend 40cc for the spring leg!) and perhaps wiping some excess grease off the spring, you'll be far more likely to have a properly lubed fork.
I'm not trying to argue with you, we just have differing opinions on this small detail. There's nothing wrong with 40cc in the spring leg of a Team, I just don't find that the benefit outweighs the mess. If you remove the c-clip on the spring leg you will find that there is a large spacer that blocks most of the upper leg. It has two flat areas that would allow a small amount of oil to get past. IMO 15cc will have a difficult time getting past because there is room for 15cc between the upper and lower assemblies when the fork is fully bottomed. However, if you use 40cc of oil the only option for the extra oil to fit in the fork at full bottom out is to be squeezed into the upper leg where it will mix with the spring grease.