Shock Travel

Front view · camera fixed to the frame 2.5 x 20 smooth body

Show

0.0 in · ride height

Wheel travel 20.1 in total · P passenger · D driver

-16.1 in down · shock tops out ride +4.0 in up · shock bottoms

Shock length shock stroke travel needs P passenger · D driver · dashed: ride

30.5 incollapsed 50.5 inextended

Driver now: 34.5 in
Passenger now: 34.5 in
At ride: 34.5 in
Room left: 4.0 in to bottom · 16.0 in to top

Travel needs 30.5 in to 50.5 in: 20.0 in of stroke.

Verdict

Works: 4.0 up, 16.1 down. 1 thing to check.

Pins what you have now as Before, so every change after shows the difference.

Or compare with

Travel: 4.0 in up · 16.1 in down
Ends at: shock bottoms · shock tops out
Stroke used: 20.0 in of 20.0 in
At ride height: 34.5 in · 80% compressed
Diff center moves: -16.1 in to +4.0 in
Driveshaft joints, worst: pinion 32° · t-case 39°
Shock per inch of wheel: 1.00
Angle from vertical: 3° in droop · 5° in ride · 6° in bump

Driveshaft joints reach 39° Pinion joint up to 32°, transfer case joint up to 39°. That is steep; check it against your joints' rating, and consider where the pinion points.

Notes (5)

Up travel ends where the shock bottoms out The shock's internal bump takes every full-compression hit. A bump stop that engages a little sooner protects it: turn on Bump stops.
Down travel ends where the shock tops out The shock takes every top-out hit. A limit strap set a little shorter protects it: turn on Limit straps.
Upper mount sits 27.9 in above the frame bottom That is 20.9 in above the top of the rail: shock hoop or through-the-hood territory on most trucks. Check hood, fender and engine clearance.
Lower eye swings 18° through travel That is the angle change between the shock and the axle bracket. Check it against the eye bearing's misalignment rating.
Front driveshaft changes length by 6.6 in It runs 23.1 in to 29.7 in joint to joint through bump, droop and flex (23.2 in at ride). The slip yoke or spline needs at least that much travel, plus margin at both ends.

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.

Up travel

Yours: 4.0 in

Down travel

Yours: 16.1 in

A different shock

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 4.0 in of up travel. Click a row to preview that shock.

Shock	Length	Travel here (up / down)	Upper mount for 4.0 in up	Above the rail
2.5 x 8	16.00 to 24.00	won't fit here	13.2	6.2
2.5 x 10	18.38 to 28.38	won't fit here	15.6	8.6
2.5 x 12	20.65 to 32.65	won't fit here	17.9	10.9
2.5 x 14 short body	21.75 to 35.75	7.1 / 1.3	19.0	12.0
2.5 x 14	23.25 to 37.25	7.1 / 2.8	20.6	13.6
2.5 x 16	26.00 to 42.00	7.1 / 7.5	23.3	16.3
2.5 x 18	28.00 to 46.00	6.5 / 11.6	25.3	18.3
2.5 x 20*	30.50 to 50.50	4.0 / 16.1	27.9	20.9

* 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	1.0	19.1	shock bottoms	shock tops out	95%	Check
-2 in	2.0	18.1	shock bottoms	shock tops out	90%	Check
-1 in	3.0	17.1	shock bottoms	shock tops out	85%	Check
design	4.0	16.1	shock bottoms	shock tops out	80%	Check
+1 in	5.0	15.1	shock bottoms	shock tops out	75%	Check
+2 in	6.0	14.1	shock bottoms	shock tops out	70%	Check
+3 in	7.0	13.1	shock bottoms	shock tops out	65%	Check
+4 in	8.0	12.1	shock bottoms	shock tops out	60%	Check

Your setups

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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. For any other shock, press Edit these lengths and enter the maker's eye-to-eye figures.