shock pressure

[usaoze]

Can anyone tell me a 'simple' rule of thumb to adjust for rear shock for the air pressure?....ie: weight per rebound (or something like that!)

Also, is there an adjustment for my specialized fox front shocks (adjust from the top left fork cap and how much psi?)

thanx

[05stumpy]

Pressures can vary depending on your actual model of shock and fork. Assuming you have some kind of fox rear shock on your stumpjumper, a good starting point is to pump it up to your body weight (ie weigh 170 lbs, air it up to 170 psi).

The best way to set pressure is to measure static sag using the o-ring slider or a zip tie...you set the pressure, then sit on the bike without bouncing and see how much it sags from your weight. Typically you want it to sag 25% or so of total travel, a little more for a plush ride, a little less for a firmer ride.

If you have an air/oil fork (like a TALAS or a FLOAT) there is also an air pressure adjustment. The forks run lower pressure than the rear shock.

Ther are some good tuning guides at http://www.foxracingshox.com/fox_tech_center/index.htm

Find the manual for your specific shock and fork and take it from there.

[05stumpy]

FOX 32mm Fork Tuning tables

SAG SETUP
Fork Travel XC/Race FIRM Freeride PLUSH
90mm (3.5") 12mm (1/2") 20mm (13/16")
110mm (4") 15mm (9/16") 25mm (1")
130mm (5") 20mm (13/16") 33mm (1 5/16")

TALAS AIR SPRING SETTINGS
Rider Weight Air Pressure
< 125 lbs. 50 psi
125 – 135 lbs. 55 psi
135 – 145 lbs. 60 psi
145 – 155 lbs. 65 psi
155 – 170 lbs. 70 psi
170 – 185 lbs. 80 psi
185 – 200 lbs. 90 psi
200 – 215 lbs. 100 psi
215 – 230 lbs. 115 psi
230 - 250 lbs 125 psi

FLOAT AIR SPRING SETTINGS
Rider Weight Air Pressure
< 125 lbs. 45 psi
125 – 135 lbs. 50 psi
135 – 145 lbs. 55 psi
145 – 155 lbs. 65 psi
155 – 170 lbs. 75 psi
170 – 185 lbs. 85 psi
185 – 200 lbs. 95 psi
200 – 215 lbs. 105 psi
215 – 230 lbs. 115 psi
230 - 250 lbs 125 psi

F-series/FX AIR SPRING SETTINGS
Rider Weight Air Pressure
< 125 lbs. 45 psi
125 – 135 lbs. 50 psi
135 – 145 lbs. 55 psi
145 – 155 lbs. 65 psi
155 – 170 lbs. 75 psi
170 – 185 lbs. 85 psi
185 – 200 lbs. 95 psi
200 – 215 lbs. 105 psi
215 – 230 lbs. 115 psi
230 - 250 lbs 125 psi

VANILLA SETTING SAG
To get the best performance from your VANILLA fork, it is necessary to set and adjust sag. Generally, sag should be set to 15 – 25% of total fork travel.
1. Install a zip tie with light friction on the upper tube and push it down until it contacts the fork seal. Carefully sit on the
bike and assume a normal riding position. The fork should compress slightly. Being careful not to further compress
the fork, dismount the bicycle. Measure the distance between the seal and the zip tie. This distance is sag.
2. Compare your sag measurement to the SAG SETUP table below.
IF SAG IS LOWER THAN ON THE TABLE, turn the preload knob counter-clockwise one (1) full turn. Measure sag again
and repeat adjustment if necessary.
IF SAG IS HIGHER THAN ON THE TABLE, turn the preload knob clockwise one (1) full turn. Measure sag again and repeat
adjustment if necessary. If correct sag cannot be achieved by adjusting the preload knob, see the COIL SPRING SETTINGS
table below. You may need to obtain a coil with a different spring rate.
SETTING UP YOUR FORK
ADJUSTING REBOUND, COMPRESSION, LOCKOUT AND THRESHOLD
Depending on your fork model, some controls may or may not be available on your fork. To see which controls depending on model are available
on your VANILLA fork, see page 20. Then see pages 6-8 to adjust them.
Make sure that your sag doesn’t change after making an adjustment. See the SAG TROUBLESHOOTING table on the next page to troubleshoot common
fork performance problems, which can usually be fixed by checking and adjusting the sag setting.
COIL SPRING SETTINGS
FOX Part # Spring Rate Color Code Travel Range
Rider Weight
Lbs. / Travel
Notes
039-05-010 10 lb/in Black 100 – 130
<90–115 / 130
<90–110 / 100
039-05-011 18 lb/in Purple 100 – 130
115–155 / 130
110–130 / 100
039-05-012 25 lb/in Blue 100 – 130
150–180 / 130
130–150 / 100
Standard on
Vanilla 130
039-05-013 35 lb/in Green 100 – 130
175–210 / 130
150–180 / 100
Standard on
Vanilla 100
039-05-014 45 lb/in Yellow 100
205–240+/ 130
175–200 / 100
039-05-015 60 lb/in Orange 100 195–225 / 100 100mm max
039-05-016 75 lb/in Red 100 220–245 / 100 100mm max

[usaoze]

THANX 05 STUMPY!
Do you have one as well?
In order to add/check the pressure on the front fork, is the left/right cap the area to unscrew and add psi to?

[skunkty14]

Keep in mind you will need a shock pump to adjust this; a regular tire pump will not work for adjusting your suspension. If you don't have one, I would think your LBS will adjust it for you or you could purchase one, they're realitively inexpensive. Or borrow one from a riding buddy.

If you have a Fox fork, I believe it's the left hand cap that has the air valve underneath. Wait for someone else to verify this for your, I can't remember 100%

[05stumpy]

yes the left (blue) cap (when sitting on the bike) has the air valve. Please post which model you have, it will help alot to know what your setup is. There is a cap within a cap that unthreads to expose the schraeder air valve. You def. need a shock-specific pump to adjust it.

The right side controls damping, depending on your fork you'll have rebound, lockout, compression, and lockout threshold. That's what the R-L-C stands for, some forks are just R, some are R-L. The tuning guide will help you set these.

I ride an '05 Stumpjumper Expert 120. It has a '06 Fox TALAS RLC fork and a Float-Septune on the rear. I run 70 psi front (set at 115 mm travel), 185 psi rear, and weigh about 165-170 with gear. I can play around with the lockouts and pro-pedal settings to dial in the ride on the fly.

A very flexible setup and bike IMO.