The Bilstein B6 4600 and B8 5100 are close relatives: both are 46mm monotube gas-pressure shocks with digressive valving, both bolt in where the factory shock was, and both are tuned by Bilstein for one specific vehicle. The difference is ride height. Bilstein builds the 4600 for trucks and SUVs at stock height and the 5100 for trucks that have been leveled or lifted. Pick the series by how high your truck sits, then pick the part number by vehicle, drive type and options.
What Bilstein says each one is for
On its own US off-road site, Bilstein describes the B6 4600 as a "performance upgrade for stock ride-height applications" and the B8 5100 as a "performance upgrade for lifted applications." That one line is the whole decision for most buyers.
- B6 4600: a stock-height replacement with a Bilstein tune. Bilstein notes that no spring change is required and the factory spring can be reused, and it calls out longer service life when pulling trailers or driving off-road.
- B8 5100: the same 46mm monotube, digressive-valve design, but made in different lengths for different lift heights. Bilstein says each 5100 is valved for the specific year, make and model and considers use factors such as loaded or unloaded, towing and tire pressure. Bilstein lists them as made in the USA or Germany, with a zinc-plated body.
Bilstein does not publish a "softer vs firmer" ranking between the two, so be wary of anyone who tells you one always rides stiffer. Each part number has its own valving for its vehicle.
Side by side
| B6 4600 | B8 5100 | |
|---|---|---|
| Built for | Stock ride height | Leveled or lifted trucks and SUVs |
| Body | 46mm monotube, gas pressure | 46mm monotube, gas pressure |
| Valving | Digressive, tuned per vehicle | Digressive, tuned per vehicle |
| Springs | Factory springs | Factory springs or lift springs, depending on the part |
| Lengths | One length per position for the stock truck | Several lengths, each for a stated lift range |
| Front leveling option | No | Yes: the 5100 (Ride Height Adjustable) and 5112 kits |
Why length matters more than the name
A shock has a fixed collapsed and extended length. Lift a truck and the distance between the shock mounts grows, so a stock-length shock runs short of travel and can top out. That is why Bilstein makes the 5100 in steps and prints the lift range in each part's application notes. Two examples from Bilstein's own catalog:
- Ford F-250 / F-350 Super Duty 4WD 2005-2016: front 5100 24-186018 is listed for a 2 in front lift and 24-186681 for a 6 in front lift. At the rear, 24-186025 is for 0 to 1 in of rear lift and 24-062466 for 2 to 4 in.
- Toyota Tundra 2007-2021: the stock-height pair is 4600 front 24-186230 and rear 24-186247. For a lifted rear, Bilstein lists 5100 rears 24-321150 (0 to 1 in), 24-286244 (2 in) and 24-286251 (4 in).
So "4600 or 5100" is really "how much lift, at which axle?" Measure the front and rear separately (see how to choose Bilstein shocks by lift height). A leveled truck is often raised at the front only, which means the front needs a 5100 and the rear may still be at stock height.
The leveled truck: 5100 front, low-lift rear
On many mid-size and half-ton trucks with a front coilover, Bilstein's answer to leveling is the 5100 (Ride Height Adjustable). Bilstein describes it as an alternative to coil spring spacers: it reuses the factory front spring and has snap-ring grooves for the spring seat, giving 0 to 2.75 in of lift depending on the application. Pair it with a rear shock made for the rear height you actually run.
That is how our 5100 four-shock sets are built. The Tundra 2007-2021 5100 set combines the adjustable front 24-232173 (Bilstein lists 0.875 to 2.3 in of front lift) with rear 24-321150 for 0 to 1 in of rear lift. The Tacoma 4WD 2016-2023 5100 set pairs front 24-263108 (0 to 2 in) with rear 24-186728 (0 to 1 in).
Heavy-duty trucks use a different approach: their front leveling kits are the 5112, which Bilstein describes as two 5100 shocks combined with two matched coil springs. See 5100 vs 6112 for leveling for how those compare.
Towing a camper or trailer
Both series are built with towing in mind. Bilstein's 4600 page mentions service life when pulling trailers, and its 5100 page lists towing among the use factors it tunes for. The deciding point is still height:
- Truck at factory height, towing a travel trailer or fifth wheel: the 4600 is the part Bilstein lists for it.
- Truck leveled or lifted, towing: the 5100 for the lift you run, front and rear checked separately.
Watch the option notes. On the Ram 2500 2014-2026, for example, 4600 rear 24-269439 is listed for 2WD trucks without air leveling suspension, while on the Ram 3500 2019-2026 Bilstein lists a separate rear, 24-302302, for 4WD trucks with rear air leveling. Our answer page Bilstein 4600 or 5100 for a Ram 2500 that tows a fifth wheel? walks through the drive-type split on that truck.
Quick way to decide
- Is the truck at factory height at both ends? Choose the 4600.
- Is the front leveled or lifted? Choose a 5100 whose notes cover your front lift. On coilover-front trucks, the 5100 (Ride Height Adjustable) can do the leveling for you.
- Check the rear separately. Stock or within 0 to 1 in: a stock-height or 0 to 1 in rear. More lift: the 5100 rear for that height.
- Check drive type (2WD or 4WD), cab and air-leveling notes on the product page.
- Confirm in the Bilstein Shock Fitment Finder, which lists every Bilstein part we carry by make, model and year.
Browse all of them in our Bilstein shocks collection. Found it cheaper? We'll beat it.
FAQ
Can I run a 5100 on a stock-height truck?
Some 5100 parts are listed for 0 to 1 in of lift, which covers a stock truck at that axle. Others are made for 2, 4 or 6 in and are too long for a stock truck. Go by the lift range in the part's notes, not the series name.
Can I mix a 5100 front with a 4600 rear?
Bilstein sells them as separate parts for each position, so a leveled truck can run a front built for its front height and a rear built for its rear height. What matters is that each shock suits the height at its own axle.
Do the 4600 and 5100 need new springs?
The 4600 uses the factory springs. Most 5100 shocks do too; lifts that use new springs or blocks need a 5100 for the resulting height. The 5112 kits include matched springs.
Is the 5100 a reservoir shock?
No. The reservoir version is the B8 5160, which Bilstein describes as the 5100's monotube design with a remote reservoir for more oil capacity and heat dissipation.