2011 Demo 8 Setup + Bos!

Deano · Apr 21, 2011

the idylle should be ready to rock outta the box.

all you should have to do is put in the lighter spring.

Supa8 · Apr 21, 2011

150lbs and I had to move up to a 350 spring. 300 should be spot on at 133lbs. You are going to have a tough time dialing in the rear shock with out the proper spring rate.

tuumbaq · Apr 21, 2011

what do you mean exactly by dialing the shock anyways ? A dialed shock is mostly a matter of preferences for each riders and you need to tell us exactly what it is thaa you dont like and what you are trying to achieve ...

marshalolson · Apr 21, 2011

how is the shock setup now?

# of clicks on HSC
# of clicks on LSC
air pressure
# of turns on bottom out

what does it ride like? what do you want it to do better?

tuumbaq · Apr 21, 2011

You still not giving us a lot of info on your setup . . . Kinda hard to help you my friend

Unfortunately I'd say you went from quite possibly the best custom tuned rear shock to quite possibly the WORST, stock shock on the market ...I really dont understand why Specialized wont step up to the plate and offer a bike with a decent shock like other manifacturers have already been doing for a while ...they have a great platform with a horrible rear shock IMO...You may want consider having the shock valved.

That said the Demo is a great plow bike and shines in the rough stuff , it shouldnt be that hard to make it super plush but harder to make it lively.The stock valving has hardly any top and very little mid-stroke support making things rather interesting when trying to dial it.

So to get you close to your older bike(what you are use to ride)I would run the shock with quite a bit of air pressure.It should give you some "pop"/ mid stroke compression and I 'd probably run a fair amount of LSC as well.Assuming you are running the right spring, the bike should have decent small bumps compliance and will sit high-iiish in its travel...

The stock RC4 has a tendency to dive in its travel very quickly making it harder to have the bike stay up.You could go up spring rates but you'll loose small bumps, the back end will bounce everywhere and make things even worst IMO (again assuming you have the correct sag )The bike already ramps up like crazy toward the end of its stroke so I would play with HSC a bit until you dont get too many harsh bottom outs but @ your weight, I wouldnt even bother trying to adjust the air chamber as it will ramp up even more and give you a harsher ride.

Everyone seems to love the Demo on this forum so Im sure you'll get some good info...I cant help you with the fork but once the rear is dialed, it should be easier to adjust your fork
Good luck !

Steve M · Apr 21, 2011

tuumbaq said:
You still not giving us a lot of info on your setup . . . Kinda hard to help you my friend

Unfortunately I'd say you went from quite possibly the best custom tuned rear shock to quite possibly the WORST, stock shock on the market ...I really dont understand why Specialized wont step up to the plate and offer a bike with a decent shock like other manifacturers have already been doing for a while ...they have a great platform with a horrible rear shock IMO...You may want consider having the shock valved.

That said the Demo is a great plow bike and shines in the rough stuff , it shouldnt be that hard to make it super plush but harder to make it lively.The stock valving has hardly any top and very little mid-stroke support making things rather interesting when trying to dial it.

So to get you close to your older bike(what you are use to ride)I would run the shock with quite a bit of air pressure.It should give you some "pop"/ mid stroke compression and I 'd probably run a fair amount of LSC as well.Assuming you are running the right spring, the bike should have decent small bumps compliance and will sit high-iiish in its travel...

The stock RC4 has a tendency to dive in its travel very quickly making it harder to have the bike stay up.You could go up spring rates but you'll loose small bumps, the back end will bounce everywhere and make things even worst IMO (again assuming you have the correct sag )The bike already ramps up like crazy toward the end of its stroke so I would play with HSC a bit until you dont get too many harsh bottom outs but @ your weight, I wouldnt even bother trying to adjust the air chamber as it will ramp up even more and give you a harsher ride.

Everyone seems to love the Demo on this forum so Im sure you'll get some good info...I cant help you with the fork but once the rear is dialed, it should be easier to adjust your fork
Good luck !

I disagree with pretty much every single thing you've said there. How is a DHX5 in any way a better shock than the RC4? And if you reckon the RC4 is the "worst stock shock on the market" then I'd suggest that you haven't actually ridden many if any of its direct competitors, it's an incredibly capable shock in stock guise, and far more versatile than anything else I've ridden. Also, Demos don't "ramp up like crazy", in fact they're fairly linear bikes. 951s ramp up like crazy, Demos are very slightly progressive.

DHmatt - I suggest backing LSC and HSC all the way out, running bottom out resistance all the way in, 170psi in the chamber, rebound set to your preference (start 6 clicks out from full in and adjust from there if you want it faster or slower). This will give you the most plush ride (bump up the air pressure if you want even more progression) but you may find it blows through the mid stroke a bit easily or even kicks a bit off lips; if you start noticing that the rear end is blowing through travel or kicking you around then increase the compression levels to suit.

tuumbaq · Apr 21, 2011

Socket said:
I disagree with pretty much every single thing you've said there. How is a DHX5 in any way a better shock than the RC4? And if you reckon the RC4 is the "worst stock shock on the market" then I'd suggest that you haven't actually ridden many if any of its direct competitors, it's an incredibly capable shock in stock guise, and far more versatile than anything else I've ridden. Also, Demos don't "ramp up like crazy", in fact they're fairly linear bikes. 951s ramp up like crazy, Demos are very slightly progressive.

DHmatt - I suggest backing LSC and HSC all the way out, running bottom out resistance all the way in, 170psi in the chamber, rebound set to your preference (start 6 clicks out from full in and adjust from there if you want it faster or slower). This will give you the most plush ride (bump up the air pressure if you want even more progression) but you may find it blows through the mid stroke a bit easily or even kicks a bit off lips; if you start noticing that the rear end is blowing through travel or kicking you around then increase the compression levels to suit.

What I meant to say was that a custom valved shock ( Session 88 ) is > than a stock one ... never sad the RC4 was the worst shock, the Demo has one of the worst shock/frame match Ive ridden period...Slap a properly valved shock on that bike it becomes alive . . .

As for not ramping up I have to disagree with you

...The bike does dive a lot in its first part of its travel compare to most other bikes Ive ridden and by necessity ramps up towards the end...no LSC will make the bike feels very lazy and will most likely sag a whole bunch under load . . .Beside, running a fancy shock with no compression at all is pretty much like running a fancy pogo stick IMO ...doesnt it ?

Bottom out all the way in with 170 psi @ 130 pounds?...that seems a bit excessive , does not make sense to me but I've only ridden a couple of friends Demos.I've never spent any time playing with suspensions and I recon I may be completely off the track on this...again like I said earlier, setup is really a matter of personal preferences to each riders, and withouth knowing what the OP hopes to achieve its hard to make a good guess I'd say

IH8Rice · Apr 21, 2011

tuumbaq said:
Unfortunately I'd say you went from quite possibly the best custom tuned rear shock to quite possibly the WORST, stock shock on the market

tuumbaq said:
never sad the RC4 was the worst shock

i was going to comment on all the wrongness in your first statement, but couldnt be bothered

tuumbaq · Apr 21, 2011

IH8Rice said:
i was going to comment on all the wrongness in your first statement, but couldnt be bothered

lol pretty confusing am i ? All this time I was trying to the stock RC4 on the Demo is poorly valved . . .Hope I made myself look a little less crazy with my second explanation :banghead:

Tiago79 · Apr 21, 2011

DhMatt1 said:
Hey guys, a quick google didn't turn up any results.

I've got a 2011 Demo with RC4 and am really struggling to get the RC4 dialled in. I'm 133lbs (60kg) running a 350lb spring.

Also with a Idylle Rare fork, has anyone got there's sorted? Whats the trick?

Thanks,
Matt

You should be on the red spring for your fork and I would suggest starting out with the base settings that are in the manual and adjusting from there.

http://www.bosmtb.com/pdf/RaRenoticeEN.pdf

As for the shock dilema I would just call up BOS and get one of those new Stoy RaRe's to match your fork. :rofl:

Problem solved.

jnooth · Apr 21, 2011

I had this issue with my 2010 demo. I HATED the rc4 and never got it to feel right. switched to a vivi air and problem solved.

Tuumbaq: i disagree with the part where you said "the demo is a plow bike and is going to be hard to get it to feel lively"

I think it is one of the more lively bikes i've ridden. so easy to get off the ground.

Mo(n)arch · Apr 22, 2011

For your fork:
Attention with the collision between frame and the forkcrown. Like mentioned in
another thread, 40's and Bos won't fit without some special pieces like spacers under the headset or special bumpers...
If you haven't installed your fork yet, check it!

buckoW · Apr 22, 2011

DhMatt1 said:
Thanks for all the input people.
I'm going to source a 300lb spring, but it sounds like the best solution is a proper custom tune up. The shock is nowhere near as smooth as the session was. Do they have a ridiculously long bed in time?

Try what Socket said first. The shock has a big range of tuning.

It sounds to me like you need to run the shock as progressive as possible to get the beginning stroke "plush" and "good bottom out resistance." Therefore, close the bottom out chamber all the way and run a lighter spring with 170psi. and 7 clicks from closed on both compression dials. Unwind the LSC until you have the comfort you are looking for.

norbar · Apr 22, 2011

tuumbaq said:
.

As for not ramping up I have to disagree with you ...The bike does dive a lot in its first part of its travel compare to most other bikes Ive ridden and by necessity ramps up towards the end...no LSC will make the bike feels very lazy and will most likely sag a whole bunch under load . . .Beside, running a fancy shock with no compression at all is pretty much like running a fancy pogo stick IMO ...doesnt it ?

LSC has no influence on sag. Yes it will dive more and I think what demo's actually need is a fair bit of LSC but it all depends on what one needs (and weights in this case). BTW. LSC on the minimum is not no compression damping. From what you write about your demo experience it sounds like you've never ridden a very progressive bike or have had your shock setup off.
The RC4 is good shock and from my experiance if you set it up right it's more than most riders need.

Udi · Apr 22, 2011

DhMatt1 said:
The shock is nowhere near as smooth as the session was. Do they have a ridiculously long bed in time?

They actually do take some break in time!
A friend of mine got a brand new RC4, and it felt pretty sticky. A whistler trip later, it felt amazing!

So my advice is, just give it some time - and try the softer spring and softer settings (as per Socket and buckoW's posts) in the meantime.

worship_mud · Apr 22, 2011

Mo(n)arch said:
Attention with the collision between frame and the crown. Like mentioned in another thread, 40's and Bos won't fit without some special pieces like spacers under the headset or special bumpers...
If you haven't installed your fork yet, check it!

this is a part of a PM conversation between me and Tiago79, i hope he won't mind me putting it into public...

i have a BOS Idylle (non RaRe) on a 2011 Demo 8 II. initially the lower crown hit the frame right the weld behind the headtube.

these are the contact points, where the lower crown hit the frame, right into the welds between the headtube and the downtube.

this is the shim i turned from stainless steel ( i had nothing else in the workshop, haha..) it's ca 6mm high with chamfers for the bearings and the race and i fitted a rubber seal from a old headset.

you could get away with less height, i guess 3mm would be ok, i'll try to turn several ones with different heights, as soon as i find the time (and win over my lazyness)

you add ATC height, but that's no actual problem, because the headtube is extremely short with 112mm length, so a complete length of 118mm (with the 6mm shim added) is still short enough to get the cockpit low. the top of my grips is at 1065 mm which is even a bit too low for my taste, i'll probably raise it a bit, well, i'll maybe think about it..

here is the complete gallery of the bike and the fork

if you have any more questions, you're welcome!

Nagaredama · Apr 22, 2011

How do you like those Rain King tires?

ustemuf · Apr 22, 2011

i'm 170 lbs and i have my rc4 setup with 175psi, bottom out a little more than halfway max, very little HSC, and 3-4 clicks out from max on LSC. running a 350lb TI spring..

rebound is fast but thats all rider preference.

Tiago79 · Apr 22, 2011

worship_mud said:
this is a part of a PM conversation between me and Tiago79, i hope he won't mind me putting it into public...

Nope, glad you were nice enough to take photos of what you had come up with. Since then I have seen one with a external cup headset which would also be a good fix.

worship_mud · Apr 23, 2011

Nagaredama said:
How do you like those Rain King tires?

a bit slow rolling, incredible grip! i use them all year round, except for really rocky terrain, where the tyres suffer hard and the extremely soft rubber compound gets eaten alive.

worship_mud · Apr 23, 2011

Tiago79 said:
Nope, glad you were nice enough to take photos of what you had come up with. Since then I have seen one with a external cup headset which would also be a good fix.

yeah, i've seen that solution, too. seems to work fine.

sethimus · Apr 23, 2011

worship_mud said:
this is a part of a PM conversation between me and Tiago79, i hope he won't mind me putting it into public...

i have a BOS Idylle (non RaRe) on a 2011 Demo 8 II. initially the lower crown hit the frame right the weld behind the headtube.

these are the contact points, where the lower crown hit the frame, right into the welds between the headtube and the downtube.

this is the shim i turned from stainless steel ( i had nothing else in the workshop, haha..) it's ca 6mm high with chamfers for the bearings and the race and i fitted a rubber seal from a old headset.

you could get away with less height, i guess 3mm would be ok, i'll try to turn several ones with different heights, as soon as i find the time (and win over my lazyness)

you add ATC height, but that's no actual problem, because the headtube is extremely short with 112mm length, so a complete length of 118mm (with the 6mm shim added) is still short enough to get the cockpit low. the top of my grips is at 1065 mm which is even a bit too low for my taste, i'll probably raise it a bit, well, i'll maybe think about it..

here is the complete gallery of the bike and the fork

if you have any more questions, you're welcome!

acros is making special spacers you can put between the lower cup and the frame:

(the black one)

http://www.downhill-board.com/58886-specialized-demo-2011-dh.html?p=751282&viewfull=1#post751282

Steve M · Apr 25, 2011

tuumbaq said:
What I meant to say was that a custom valved shock ( Session 88 ) is > than a stock one ... never sad the RC4 was the worst shock, the Demo has one of the worst shock/frame match Ive ridden period...Slap a properly valved shock on that bike it becomes alive . . .

As for not ramping up I have to disagree with you ...The bike does dive a lot in its first part of its travel compare to most other bikes Ive ridden and by necessity ramps up towards the end...no LSC will make the bike feels very lazy and will most likely sag a whole bunch under load . . .Beside, running a fancy shock with no compression at all is pretty much like running a fancy pogo stick IMO ...doesnt it ?

Bottom out all the way in with 170 psi @ 130 pounds?...that seems a bit excessive , does not make sense to me but I've only ridden a couple of friends Demos.I've never spent any time playing with suspensions and I recon I may be completely off the track on this...again like I said earlier, setup is really a matter of personal preferences to each riders, and withouth knowing what the OP hopes to achieve its hard to make a good guess I'd say

The current Demos are very mildly progressive, the older ones were about the most linear non-singlepivot bikes on the market. The ramp up you may be feeling with an RC4 is the shock rather than the frame. Bottom out all the way in isn't excessive at all actually, it isn't THAT progressive that it's unusable. A quick synopsis of how the bottom out/air pressure adjustments work:

- Bottom out (air volume) adjustments affect the shape of the compression curve, in other words, the RATIO of the amount of damping late in the travel to the amount of damping early in the travel. This means that at a certain shaft speed 20% of the way into the stroke, the boost valve (alone) might be generating say X lbs of damping force, whereas at the same shaft speed at 80% of the way into the stroke, it might be generating say 3.5X lbs of damping force.

- Air pressure affects the MAGNITUDE of the damping, but the curve will always follow (close to) the same shape, just multiplied or divided by a certain factor. The preload spring does affect the shape of the curve earlier in the travel but in the last third of the travel it's more or less irrelevant. Anyway what this means (ignoring the preload spring) is that if you have X lbs of damping force at a given speed at 20% of the stroke (as mentioned above), and 3.5X lbs of damping force at say 80% of the stroke, that you can change the value of X by changing the air pressure. So for a given shaft speed, you could have say 100lbs of damping at 20% stroke, and 350lbs at 80% stroke, or 200lbs at 20% stroke and 700lbs at 80% stroke (values are entirely arbitrary and not realistic btw).

Because the volume adjustment affects a RATIO rather than a singular number, rider weight is less relevant to where you should set it, than the leverage rate of the frame, in my opinion. I would recommend a certain volume for a certain frame regardless of rider weight, and later scale the air pressure to suit rider weight. 170psi should be a decent starting point IMO, even at that weight - I doubt anyone will find the bike TOO progressive with that setup, esp knowing the leverage ratio of the Demo. If you do, just back it off a bit!

You also have to keep in mind that the boost valve is one of THREE compression damping circuits in the shock (boost valve, resi bridge/adjuster valving, main piston/mid valve). If all three were generating comparable percentages of the overall compression damping force, changing any one of them by 100% would only affect the net amount of compression damping by roughly a third. In other words, each single circuit is not hypersensitive, and you can make relatively large changes to one without the overall change to the shock being all that massive. This is why the boost valve pressure can be varied between 125psi and 200psi with entirely reasonable results - it's not the same as changing a spring from say a 250lbs/in to a 400lbs/in on a given bike in terms of the net effect it has on the ride.

In my opinion, understanding how the boost valve works is the key to making the RC4 work for you, and the reason why it's so versatile. For highly progressive bikes, you don't want or need strong end-stroke ramp up, but for very linear ones you do. What the RC4 lets you do that really makes it versatile is set up bottom out resistance fairly independently of early and mid stroke characteristics. This means you don't need to run the bike oversprung or heavily damped to avoid harsh bottom outs if the leverage rate is linear (or even slightly falling rate), but because its adjusters have a very wide range, you can get plenty of support in the early/mid stroke if you want it too.

edit: as far as running a shock with no compression damping, it actually makes it a lot more lively, because less energy is dissipated as heat and more energy is stored/returned by the spring. It can be a pogo stick if there's absolutely no compression damping and your rebound is fast, but it has to be a seriously extreme setup to achieve that if your rebound is at a reasonable setting (ie anything other than really fast). I have found though, that rebound settings become more critical if you run less compression, and less critical if you run more compression, you just get more room to move.

rider chx · Apr 25, 2011

sethimus said:
acros is making special spacers you can put between the lower cup and the frame:

(the black one)

http://www.downhill-board.com/58886-specialized-demo-2011-dh.html?p=751282&viewfull=1#post751282

Hi,

I have the same frame and I want to mount a BOS Idylle without this problem...

I have a few question about your spacer

Did you change all the headset or is it just a spacer you can buy dispatched ?

Where did you find this Acros Spacer on the net ?

I have searched but I can't find this one....

Thank you a lot !!!

I'm sorry for my bad english...

was? · Apr 25, 2011

Socket said:

+rep added

Intenseman · Apr 25, 2011

rider chx · Apr 25, 2011

I have talked today with the owner of this bike and he also have problems with the crown which touches the frame...

2011 Demo 8 Setup + Bos!

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