Fox springs have two measurements, and for this example we will use 2.8" x 500 lbs.
- “2.8"” refers to the maximum free stroke of the spring. Free stroke is the maximum amount a spring can be compressed until the coils touch and create “coil bind” which is very bad. This example spring can be compressed 2.8" before coil bind occurs.
- “500 lbs” refers to the spring rate, which is how stiff or soft the spring is.
- Springs also have a "TLG" length which just means Total Length. This is physically how long the spring is when uncompressed.
The following must apply for proper spring fitment: - Each shock has a minimum and maximum TLG that fits, which is shown in the first set of charts below. - The goal is to find a spring with your desired spring rate and with a TLG that falls within the range of TLG for your shock’s model and size. - The stroke length of the spring MUST be larger than the stroke length of your shock. If it is not, coil bind will occur and parts will explode.
HOW TO FIND WHICH FOX SPRING FITS YOUR SHOCK
STEP 1 - Find your shock’s model and size in the first group of charts. - Write down the shortest and longest TLG lengths shown in the chart.
STEP 2 - Scroll down to the model of Fox spring you want. - Refer to the right side “Commonly Used With” to quickly locate which length most likely applies. Still double check that this size fits your shock!
STEP 3 - Look for the spring rate you want in the chart. Some sizes have the same spring rate twice, so note that. - Look at that spring’s TLG to see if it fits within the range of your shock that you wrote down. - If your desired spring rate is listed twice, check each TLG to see which will fit.
STEP 4 - Make sure the spring’s stroke length is larger than your shock’s stroke length. - For example: If you have a 65mm stroke, convert that to inches which is 2.6”. If a 2.8” spring’s TLG fits, then you are set since 2.8” is larger than 2.6”. - If you find a TLG that fits, but the shock’s stroke is longer than the spring’s stroke, you may not be able to use a coil shock or need to find a different spring.
STEP 5 - If multiple springs show to fit, choose which one you'd like to use. - A slightly shorter spring will sit farther down on the preload threads, while the longer option will sit higher on the threads. - There is no performance advantage either way, and this is just personal preference. A shorter spring will be slightly lighter, but that is all.
STEP 6 - Order the spring that meets all criteria and ride!
Commonly used with: - 7.875" x 2.25" - 185mm(T) x 50mm - 185mm(T) x 52.5mm - 185mm(T) x 55mm - 210mm x 50mm - 210mm x 52.5mm - 210mm x 55mm
Still double check that the spring fits if your shock size is listed here!
2.8"/71mm Travel (1.385in ID)
Part #
Description
(Old Part #)
803-04-142
2.8" x 250 lb - 4.924" TLG
039-03-022
803-04-143
2.8" x 350 lb - 5.799" TLG
039-03-001
803-04-144
2.8" x 400 lb - 5.459" TLG
039-03-002
803-04-145
2.8" x 450 lb - 5.409" TLG
039-03-003
803-04-146
2.8" x 500 lb - 5.728" TLG
039-03-004
803-04-147
2.8" x 550 lb - 5.949" TLG
039-03-005
803-04-148
2.8" x 550 lb - 5.750" TLG
039-00-600
803-04-149
2.8" x 600 lb - 6.382" TLG
039-03-007
803-04-150
2.8" x 600 lb - 5.750" TLG
039-00-601
803-04-151
2.8" x 650 lb - 6.150" TLG
039-03-008
803-04-152
2.8" x 700 lb - 6.402" TLG
039-03-010
Commonly used with: - 8.5" x 2.5" - 205mm(T) x 60mm - 205mm(T) x 62.5mm - 205mm(T) x 65mm - 230mm x 57.5mm - 230mm x 60mm - 230mm x 62.5mm - 230mm x 65mm
Still double check that the spring fits if your shock size is listed here!
3.19"/81mm-3.25"/83mm Travel (1.385in ID)
Part #
Description
(Old Part #)
803-04-153
3.25" x 250 lb - 6.468" TLG
039-09-010
803-04-154
3.24" x 300 lb - 6.126" TLG
039-03-000
803-04-155
3.25" x 300 lb - 6.476" TLG
039-09-000
803-04-156
3.25" x 350 lb - 6.689" TLG
039-09-001
803-04-157
3.25" x 400 lb - 6.634" TLG
039-09-002
803-04-158
3.25" x 450 lb - 6.760" TLG
03909-003
803-04-159
3.15" x 500 lb - 6.600" TLG
039-00-603
803-04-160
3.25" x 500 lb - 6.909" TLG
039-09-004
803-04-161
3.15" x 550 lb - 6.400" TLG
039-00-604
803-04-162
3.25" x 550 lb - 6.929" TLG
039-09-005
803-04-163
3.25" x 600 lb - 7.114" TLG
039-09-006
803-04-164
3.19" x 650 lb - 6.815" TLG
039-09-007
803-04-165
3.19" x 700 lb - 7.130" TLG
039-09-008
Commonly used with: - 8.75" x 2.75" - 9.5" x 3.0" - 225mm(T) x 70mm - 225mm(T) x 72.5mm - 225mm(T) x 75mm - 250mm x 70mm - 250mm x 72.5mm - 250mm x 75mm
Still double check that the spring fits if your shock size is listed here!
3.64"/92mm-3.85"/98mm Travel (1.385in ID)
Part #
Description
(Old Part #)
803-04-166
3.85" x 150 lb - 6.800" TLG
039-12-000
803-04-167
3.80" x 200 lb - 7.000" TLG
039-12-001
803-04-168
3.80" x 225 lb - 7.000" TLG
039-12-008
803-04-169
3.75" x 250 lb - 7.200" TLG
039-12-002
803-04-170
3.75" x 275 lb - 7.500" TLG
039-12-009
803-04-171
3.70" x 300 lb - 7.750" TLG
039-12-003
803-04-172
3.70" x 325 lb - 7.755" TLG
039-12-010
803-04-173
3.70" x 350 lb - 7.750" TLG
039-12-004
803-04-174
3.65" x 400 lb - 7.750" TLG
039-12-005
803-04-175
3.65" x 450 lb - 8.100" TLG
039-12-006
803-04-176
3.64" x 500 lb - 8.250" TLG
039-12-007
Commonly used with: - 10.5" x 3.5"
Still double check that the spring fits if your shock size is listed here!
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