Fits: 3.5 up, 4.4 down; 12.1 of flex.
estimate 14 inputs are estimates, so these travel numbers are approximate.
Show
Wheel travel 7.9 in total · P passenger · D driver
-4.4 in down · shock tops out ride +3.5 in up · shock bottoms
Shock length shock stroke travel needs P passenger · D driver · dashed: ride
15.8 incollapsed 23.6 inextended
- Driver now
- 19.2 in
- Passenger now
- 19.2 in
- At ride
- 19.2 in
- Room left
- 3.5 in to bottom · 4.4 in to top
Travel needs 15.8 in to 23.6 in: 7.9 in of stroke. 0.0 in longer than the shock extends.
What would it take?
Pick a goal to preview what has to change. This setup's inputs stay as they are; apply a preview only if you want to.
in
Yours: 3.5 in
in
Yours: 4.4 in
Keeps your up travel, so you compare the shocks fairly.
Point the pinion at the transfer case
The pinion angle that leaves the smallest joint angle at ride height.
Example trucks
Every shock at these mounts
The travel each shock gives with the upper mount where it is now, and where to put the mount to keep your 3.5 in of up travel. Click a row to preview that shock.
| Shock | Length | Travel here (up / down) | Upper mount for 3.5 in up | Above the rail |
|---|---|---|---|---|
| 2.5 x 8 | 16.00 to 24.00 | 3.2 / 4.8 | 10.5 in | 4.5 in |
| 2.5 x 10 | 18.38 to 28.38 | 0.9 / 9.1 | 12.8 in | 6.8 in |
| 2.5 x 12 | 20.65 to 32.65 | won't fit here | 15.1 in | 9.1 in |
| 2.5 x 14 short body | 21.75 to 35.75 | won't fit here | 16.2 in | 10.2 in |
| 2.5 x 14 | 23.25 to 37.25 | won't fit here | 17.7 in | 11.7 in |
| 2.5 x 16 | 26.00 to 42.00 | won't fit here | 20.5 in | 14.5 in |
| 2.5 x 18 | 28.00 to 46.00 | won't fit here | 22.5 in | 16.5 in |
| 2.5 x 20* | 30.50 to 50.50 | won't fit here | 25.0 in | 19.0 in |
* Estimated length; no listing found.
This shock at other ride heights
The mounts stay put, so a lift moves the axle down the shock stroke: more up travel, less droop, the same total.
| Ride height | Up | Down | Up ends at | Down ends at | Compressed at ride | |
|---|---|---|---|---|---|---|
| -3 in | 0.5 | 7.4 | shock bottoms | shock tops out | 94% | Most of the travel is droop: 0.5 in up, 7.4 in down |
| -2 in | 1.5 | 6.4 | shock bottoms | shock tops out | 81% | Most of the travel is droop: 1.5 in up, 6.4 in down |
| -1 in | 2.5 | 5.4 | shock bottoms | shock tops out | 68% | Fits |
| design | 3.5 | 4.4 | shock bottoms | shock tops out | 56% | Fits |
| +1 in | 4.5 | 3.4 | shock bottoms | shock tops out | 43% | Fits |
| +2 in | 5.5 | 2.4 | shock bottoms | shock tops out | 30% | Fits |
| +3 in | 6.5 | 1.4 | shock bottoms | shock tops out | 18% | Most of the travel is bump: 6.5 in up, 1.4 in down |
| +4 in | 7.5 | 0.4 | shock bottoms | shock tops out | 5% | Most of the travel is bump: 7.5 in up, 0.4 in down |
How this works
- Front view, with the camera fixed to the frame, so the axle and the ground move. Lengths are in inches, eye to eye.
- Travel is measured at the wheel center from ride height. By default the shock sets it: up travel ends where the shock bottoms, down travel where it tops out. Raising the upper mount moves the split toward up travel; the total stays about the shock's stroke. Bump stops, straps and the frame can end travel sooner.
- Switch to "Bump stops and straps set the travel" when the travel is fixed by other parts and you want to know whether a shock survives it.
- A post-mount shock's length runs from the stem shoulder, not the plate: the lower bushing and washer hold the shoulder below the plate. Enter that stack and measure the upper mount to the underside of the plate.
- The diff marker shows how far the diff moves from ride height. In flex it rises or falls with the side it is offset toward. The pinion moves with it; what matters for the driveshaft is the pinion angle, shown in the side view.
- The side view looks at the driver side, front of the truck on the left. Both views come from one 3D model, so a shock leaning fore or aft has its true length everywhere. For now the axle moves straight up and down with no fore-aft shift or pinion rotation; suspension links will change that.
- The front driveshaft runs from the pinion U-joint to the transfer case front output, whose shaft points straight forward. Its length range is the slip it needs; the joint angles are the full 3D operating angles.
- Wheel position comes from the axle width at the mounting surfaces, the wheel width (about an inch more overall) and the backspacing.
- Flex puts one wheel at full bump and the other at full droop, through ride height. Real flex may stop sooner, at a tire, a link or a driveshaft.
- A shock inboard of the wheel moves less than the wheel. Leaning it moves it less again, and the ratio changes through travel.
- Bump stop compression, bushing deflection and fore-aft mount offset are not modeled. Leave margin at both ends.
- Nothing you enter is sent to or stored on our servers. Saved setups live in your browser's storage, and the setup in the address bar sits after the #, which browsers never send to a server. The site is static files on GitHub Pages; like any web host, GitHub sees ordinary request details such as your IP address.
- Shock lengths for 8 to 18 in come from reseller listings for the King 2.5 smooth body remote reservoir. The 20 in is an estimate. Stock shocks for the vehicle starting points come from stock-height replacement listings for each fitment. For any other shock, press Edit these lengths and enter the maker's eye-to-eye figures.