Eunorau SPECTER-S 4.0 Full-Suspension Mid-Drive Fat eBike (Hunter X9)

A 1,000 W Bafang mid-drive that pulls through an 11-speed, on a full-suspension frame with 4-inch tires.

• 1,000 WRated, mid-drive
• 140 mmFork travel
• 40 miRated range
• 300 lbMax payload
• 83.7 lbBike weight

What you get with the SPECTER-S 4.0

Mid-drive

The motor works your gears

Eunorau fits a Bafang G510 rated at 1,000 W, 48 V, at the cranks. Power goes through the chain and the 11-speed cassette, so on a steep climb you shift down and the motor gets the same mechanical advantage your legs do. The weight sits low and in the middle of the bike, between the wheels.

Full suspension

140 mm up front, a shock at the back

An EXPLORER fork with 36 mm stanchions gives 140 mm of travel, and an AO-38RC rear shock, 190 mm eye to eye, adds 50 mm at the back. With 26 × 4.0 inch Kenda K-1151 tires on 150 mm and 197 mm hubs, you have grip and give on gravel roads, sand, snow and rutted two-track.

11-speed

SRAM NX, 11–42T

A SRAM NX trigger shifter and long-cage derailleur run an 11–42T PG-1130 cassette off a 40T chainring on 170 mm cranks. A shift sensor cuts the motor for an instant as you change gear, which spares the chain and cassette under a 1,000 W load.

Stopping

Four-piston hydraulic brakes

HD-E620 four-piston hydraulic calipers on 180 mm rotors, front and rear. Four pistons per caliper give you a firmer, more controllable bite for long descents on a loaded fat bike.

Battery

48 V 17.5 Ah of LG cells, removable

The pack is 13S5P of LG 3,500 mAh cells behind a 30 A BMS, in a lockable, removable down-tube case, and Eunorau rates it to 40 miles. It comes standard with the rack, full aluminum fenders, front and rear lights, an adjustable kickstand and platform pedals, so it is ready for the trailhead as it ships.

Pick your color and frame

Moon Black, 16-inch frame · Moon Black, 18-inch frame · Army Green, 16-inch frame · Army Green, 18-inch frame

All four are $3,799, in stock, and ships the week of October 5, 2026. In Eunorau's own photographs Moon Black reads as a slate blue-grey, and Army Green as an olive green.

Why buy the SPECTER-S 4.0 from Redtail

Who the SPECTER-S 4.0 is for

Choose the SPECTER-S 4.0 if your riding leaves the pavement: fire roads, sand, snow, hunting ground or rough two-track, where full suspension and a motor that climbs through its gears pay off every ride.

Two things to check before you order

1. Your height, against the frame. Eunorau recommends the 16" frame for riders 5'3"–6'3" (160–190 cm). It publishes saddle height for both frames, 19.3–24 in (490–610 mm) on the 16" and 21.3–26 in (540–660 mm) on the 18", and leaves the 18" rider-height cell blank. If you are at the tall end of that range, send us your height and inseam and we will match you to a frame before you order.
2. How far you ride. Eunorau rates the 4.0 at up to 40 miles, or 52 miles combined with its optional 48 V 5 Ah second pack. If you want more from the box, the SPECTER-ST 2.0 is rated to 80 miles with a second battery, on the same 1,000 W mid-drive platform, at $2,999.

What changed from the SPECTER-S 3.0

The 4.0 replaced the SPECTER-S 3.0 on Eunorau's own page in September 2026. The motor carries over: Eunorau's 3.0 page named it the "Bafang G510(M620)", and the 4.0 runs the G510. So do the 48 V 17.5 Ah main battery and the 190 mm rear shock with 50 mm of travel. What is new, in Eunorau's published figures:

3.0 figures: Eunorau's product page for the SPECTER-S 3.0 as archived by the Internet Archive on September 4, 2026. 4.0 figures: the same address, read on September 30, 2026.

How it compares with what else we sell

Every figure in this table is Eunorau's own, each read on that bike's product page on September 30, 2026; prices are ours, read the same day. Where another of our bikes is ahead on a row, the row says so and links to it.

Owning the SPECTER-S 4.0 in your state

Federal law defines a low-speed electric bicycle at 15 U.S.C. § 2085(b): a two- or three-wheeled vehicle with fully operable pedals and "an electric motor of less than 750 watts (1 h.p.)", whose top speed on motor power alone, on a paved level surface with a 170-pound rider, is less than 20 mph.

Eunorau's quick specification lists this bike as "Default Class 2" and gives a manufacturer-defined display limit of up to 28 mph. Its rated motor output is 1,000 W, which is above the statute's "less than 750 watts", so plan to ride it where that is not the question: trail, ranch, private land and hunting ground.

States set their own rules on top of the federal definition, and most use a three-class system that decides where you can ride, whether a helmet is required and whether there is a minimum age. Our state-by-state e-bike law guide sets out what each one says.

SPECTER-S 4.0 specifications

Electronics

Performance

Frame & Suspension

Drivetrain

Brakes

Wheels & Tires

Cockpit & Equipment

Geometry and rider fit

Source: Eunorau's published specification for the SPECTER-S 4.0, eunorau-ebike.com/products/specter-s-hunter, read on September 30, 2026 from both the product record and the rendered specification and geometry chart.

Eunorau gives five of these rows in both US and metric units, and the table prints the US figure: Manufacturer-defined display limit is also given as approximately 45 km/h; Range is also given as 64 km; Extended range - optional battery is also given as 83 km combined; Maximum payload is also given as 136 kg, including rider and cargo; Net weight is also given as 38 kg.

Frequently asked questions

What changed from the SPECTER-S 3.0 to the 4.0?

Not the motor: Eunorau's 3.0 page named it the Bafang G510(M620), and the 4.0 runs the G510. The 4.0 brings 16" and 18" frames, an EXPLORER fork with 36 mm stanchions, four-piston HD-E620 brakes, the DP C018.CB display, an optional 5 Ah second pack with a Type-C port, and a lighter bike at 83.7 lb.

Is a mid-drive better than a hub motor?

For climbing, usually yes. A mid-drive turns the cranks, so you can shift down and the motor works through the same gears you do, as Eunorau's own page explains. A hub motor pushes the wheel directly and is simpler. On steep, loose ground, you will feel the mid-drive's advantage.

Is the SPECTER-S 4.0 street legal?

It depends on your state and on what it counts. Federal law (15 U.S.C. § 2085(b)) defines a low-speed electric bicycle as one with a motor of less than 750 watts, and this bike is rated at 1,000 W, although Eunorau lists it as Default Class 2. Our state guide has each state's rule.

How far does the SPECTER-S 4.0 go on a charge?

Eunorau rates it at up to 40 miles on the 48 V 17.5 Ah main pack, and 52 miles combined with the optional 48 V 5 Ah second pack. Expect less into a headwind, on sand or snow, up long climbs and near the 300 lb limit. For more range from the box, the SPECTER-ST 2.0 is rated to 80 miles with a second battery.

Is the second battery included?

No. Eunorau lists the 48 V 5 Ah secondary battery as an optional configuration, sold separately. Ask us before you order and we will tell you what fits your bike.

Which frame size should I order?

Eunorau recommends the 16" frame for riders 5'3"–6'3" (160–190 cm) and publishes saddle height for both frames: 19.3–24 in (490–610 mm) on the 16" and 21.3–26 in (540–660 mm) on the 18". Its chart leaves the 18" rider height blank. Send us your height and inseam, and we will match you.

How much suspension travel does it have?

140 mm at the front from the EXPLORER fork, and 50 mm at the back from the AO-38RC shock, which is 190 mm eye to eye.

Is the battery removable?

Yes. The 48 V 17.5 Ah pack sits in a lockable, removable down-tube case, so you can take it inside to charge or store it.

Is the SPECTER-S 4.0 a good hunting e-bike?

Eunorau builds it for that job and names it the Hunter X9. You get Army Green paint, a rear rack, full fenders, 4-inch tires, full suspension, a 300 lb payload and a mid-drive that climbs through its gears. Check your state's rules for where you can ride it.

Manuals & documentation

What happens after you order

The SPECTER-S 4.0 is in stock and ships the week of October 5, 2026. Most e-bikes arrive within 5–10 business days after dispatch, depending on location. It ships in a freight box, part-assembled. Inspect it at delivery: damage, defects or a wrong item reported with photos within 48 hours are ours to fix, and we file the carrier claim.

Further reading

our Eunorau brand guide · our electric mountain bike guide · our state-by-state e-bike law guide