Mountain Bike Reviews Forum banner
1 - 20 of 37 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter · #3 ·
thanks for that link.. I am still open for some input on what other people are running there rear shock at. The guys at the lbs still ride rmx and switch so no real rides on a flatline.
thanks
 

·
1946:2006:2066
Joined
·
1,457 Posts
damn: I wrote that thing

rockyuphill said:
If your LBS can't give you any pointers, Fox has spring calculators on their website

http://service.foxracingshox.com/consumers/Content/mtbspringratecalculator.htm
It's been massaged a bit, but it's definitely my original work.

It is an early version of this which has a bug (must be viewed in IE, not Firefox)
http://forums.mtbr.com/showthread.php?t=47726

And here's a final version as a zip file for downloading and running locally:
http://forums.mtbr.com/attachment.php?attachmentid=310993&d=1195054697

cheers
 

·
ups and downs
Joined
·
15,321 Posts
The DHX 3.0 coil on the Flatline 2 gets the spring rate from the coil spring not an air spring, so the typical air shock approach of body weight plus 10 isn't a good guide.

The air is used in the reservoir for bottom out resistance and tweaking the transition between ProPedal and square edge bump absorption. The reservoir has to be set between 125-200PSI. What you might want to do is start in the middle around 160PSI and go up or down from there by 10-15PSI at a time based on the way it feels.

The DHX 3.0 is an 8.75" x 2.75" stroke shock and the Flatline 2 is a 200mm (8") travel frame when you're punching numbers into the Fox spring calculator.



The Flatline has a shock leverage ratio that helps the suspension ramp up as you get further into the travel to prevent bottoming out so the shock's bottom out resistance isn't as critical to making it ridable.

Blue Text Colorfulness Slope White
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #7 ·
so air in the canister does not affect the sag at all? I think there is too much sag I am 210-230 with gear so I feel the 450 lb spring is to weak. I dont know if I should get 550 of 600 or something else. There are many more adjustments then the rp3 shocks im used to. This is my first downhill bike. I was using my slayer for 2 years till I snaped that.
Thanks
Dave
 

·
ups and downs
Joined
·
15,321 Posts
The air in the reservoir just tinkers with bottom out characteristics and transition between ProPedal to big bump compliance, no sag.

That Fox spring calculator spit out 450 pounds as a spring rate for a 165 pound rider, that must be the default Fox assumption of rider weight, so a 550-600 pound spring should give you 25% sag at 230 pounds for rider and gear (assuming 60-65% rear wheel weight bias).
 

·
ups and downs
Joined
·
15,321 Posts
It depends on how much plush you want. 25-30% is the normal sort of range. You'll likely end up with more pressure in the reservoir to control bottoming on the shock if you're in that 210-230 pound range. Your LBS should be helping you with spring selection as part of the bike fit process, that's as critical to dialing in a bike like this as stem length and saddle choice.

The LBS guys should be able to help with some guidance on the amount of sag they run on those RMX and Switch bikes.
 

·
Living Ghetto Fabulous!
Joined
·
3,747 Posts
What I've found with my Flatline is it tends to sag 30% regardless of spring rate. I have the Flatline 3 that comes with a 9.5 X 3 size shock and I'm running a 550 spring. (I weigh around 195-210)

As an example, if you plug your numbers into the calculator, it actually tells me you should have a 450 which doesn't really hold true for what you're after...

BTW, with a 2.75 stroke shock like the one you're running, your rear travel is around 7.5 inches and the bike is best with 30% or more sag. 25% isn't an ideal amount for DH/FR IMO. I think 550 is a good starting point for you.
 

·
jones'in
Joined
·
916 Posts
Uncle Cliffy said:
......I have the Flatline 3 that comes with a 9.5 X 3 size shock and I'm running a 550 spring. (I weigh around 195-210)

As an example, if you plug your numbers into the calculator, it actually tells me you should have a 450 which doesn't really hold true for what you're after..
Damnit. I just bought a flatline and put a Vivid 5.1 on it (9.5x3). I weight about 195 and the shock calculators said I should be on a 450....which is what I bought. I noticed in my driveway bounce test (lots of snow on the ground here) that I came really close to bottoming it. Sounds like 500-550 is probably what I should have put on.

....and it's a ***** to get the shock on and off the bike. Any tricks to getting at the rear shock bolt? I had to remove the upper linkage bolt to get at it the first time.....total pain....

--Ben
 

·
Registered
Joined
·
278 Posts
venom600 said:
Damnit. I just bought a flatline and put a Vivid 5.1 on it (9.5x3). I weight about 195 and the shock calculators said I should be on a 450....which is what I bought. I noticed in my driveway bounce test (lots of snow on the ground here) that I came really close to bottoming it. Sounds like 500-550 is probably what I should have put on.

....and it's a ***** to get the shock on and off the bike. Any tricks to getting at the rear shock bolt? I had to remove the upper linkage bolt to get at it the first time.....total pain....

--Ben
There are holes drilled into the frame (linkage) to reach the rear shock bolts. Undo the top bolts of the shock first and then you will be able to raise and lower the rear wheel until you can see through the holes. I have a bike stand that I can raise and lower to the correct position as it almost requires two people without one: one to hold the bike in the right position and one to undo the bolts :thumbsup:
 

·
jones'in
Joined
·
916 Posts
swaussie said:
There are holes drilled into the frame (linkage) to reach the rear shock bolts. Undo the top bolts of the shock first and then you will be able to raise and lower the rear wheel until you can see through the holes. I have a bike stand that I can raise and lower to the correct position as it almost requires two people without one: one to hold the bike in the right position and one to undo the bolts :thumbsup:
I just tried this on mine and there aren't any holes that I can see. Undid the front shock bolt and moved the rear through it's entire travel....didn't see any point at which the rear shock bolts lined up w/ any opening. What year frame is yours? Mine is an '08....maybe they added this for '09?

--Ben
 

·
Living Ghetto Fabulous!
Joined
·
3,747 Posts
venom600 said:
I just tried this on mine and there aren't any holes that I can see. Undid the front shock bolt and moved the rear through it's entire travel....didn't see any point at which the rear shock bolts lined up w/ any opening. What year frame is yours? Mine is an '08....maybe they added this for '09?

--Ben
Swassie has an 08. The hole he's talking about is on the swingarm just below the large upper cartridge bearing. It's a 10mm hole... ;)
 

·
Living Ghetto Fabulous!
Joined
·
3,747 Posts
vwdave said:
I ordered the 600 so ill see how that works out first. Thanks for the advise. How much air are you using in the shock??
Dave
The air measurement comes down to personal preference. I like a moderate ammount of compression and by having more air in the chamber, makes more resiliant. I've got the 5.0, so I'm not sure, but most of the time I like the shock around 150+ psi. ;)

Play with different psi. settings and see what feels best. Don't run it too low though or you'll damage the internals of the canister.
 

·
jones'in
Joined
·
916 Posts
Uncle Cliffy said:
Swassie has an 08. The hole he's talking about is on the swingarm just below the large upper cartridge bearing. It's a 10mm hole... ;)
I do have openings in the swinglink. But, are you really able to fit an allen wrench in between the seatstay and the swinglink to get at the rear shock bolt? Maybe I'll take a video of my swinglink tonight to demonstrate what I'm talking about. Unless one of you has a picture handy of the hole you're referring to.
 
1 - 20 of 37 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top