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2018 Harley-Davidson Softail Slim Overview
The 2018 Harley-Davidson Softail Slim is a custom / cruiser motorcycle built around 1746 cc of displacement. Under the tank sits a Four stroke, V-Twin, Milwaukee-Eight 107, Pushrod-operated, overhead valves with hydraulic, self-adjusting lifters, 4 valves per cylinder engine, a compression ratio of 10.0:1. 2018 Harley-Davidson Softail Slim delivers 145 Nm @ 3250 rpm of torque. From a practical standpoint, the 2018 Softail Slim tips the scales at 304 kg, carries an 18.9-litre fuel tank, offers a seat height of 660 mm and spans a 1630 mm wheelbase. That's roughly 23.1 kg heavier than the average custom / cruiser motorcycle in our database. Scroll down for the complete 2018 Harley-Davidson Softail Slim spec sheet covering every technical detail from suspension travel to tyre sizes.
2018 Harley-Davidson Softail Slim compared with other bikes in the Custom / cruiser category
Here is how the 2018 Harley-Davidson Softail Slim stacks up against other bikes in the Custom / cruiser category in our database. Each model counts once, using the model year closest to this one, and the comparison covers up to 1569 models.
- Seat height of 660 mm is lower than that of 1075 of the other 1315 bikes in the Custom / cruiser category.
- Only 258 of the other 1568 bikes in the Custom / cruiser category have a larger engine displacement than the 1746 cc of the Softail Slim.
- With 145 Nm, the Softail Slim has the joint 262nd highest torque of 1053 bikes in the Custom / cruiser category, 40% above the category average of 103.5 Nm.
- Narrowing the field to the 519 models within five model years of it, the seat height of 660 mm is lower than that of 419 of the other 518.
2018 Softail Slim - Pros & Cons
Strengths
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Fuel injection: The Electronic Sequential Port Fuel Injection (ESPFI) system delivers crisp throttle response and reliable cold starts regardless of altitude or temperature.
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Strong front braking: The disc front brake gives excellent stopping power and responds well to aftermarket braided lines.
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Accessible seat height: At 660 mm, the seat height is approachable for a wide range of rider heights and builds confidence in low-speed manoeuvring.
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Large fuel range: The 18.9-litre tank is generously sized, translating to extended range between stops - ideal for touring or longer commutes.
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Low-maintenance final drive: Belt final drive means no chain to clean, lube or adjust - meaningfully less routine maintenance than a chain-driven equivalent.
Considerations
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Age-related wear: As with any used Softail Slim, a thorough pre-purchase inspection covering consumables, service history and tyres is always recommended.
Wear Points & Servicing Notes
Heat management in traffic
Softail Slim's air-cooled design means engine-bay temperatures build up more in stop-start traffic than on a liquid-cooled equivalent - a function of the cooling method itself, not a defect. Mesh riding gear and avoiding prolonged idling help in hot climates.
Fuelling & injector care
Fuelling comes from Electronic Sequential Port Fuel Injection (ESPFI). Systems like this are largely maintenance-free beyond keeping fuel quality decent and injectors clear - a fuel-system cleaner every service interval is cheap insurance.
Brake disc and pad wear
The disc front brake gives strong, progressive stopping power. Disc thickness and pad depth are worth checking at every tyre change, since worn pads can score the disc surface.
Suspension condition on used examples
Up front, the Softail Slim runs Showa Inverted forks and Mono Shock adjustable at the rear. On a used example, check fork seals for weeping oil and test the rear linkage for play - seals are a relatively cheap fix but useful when negotiating price.
Final drive maintenance
Final drive is by belt - lower maintenance than chain with no lubrication needed, but tension and tooth wear should still be checked at service intervals.
Handling the weight at a standstill
At 304 kg, the Softail Slim is a substantial machine - low-speed manoeuvring in car parks takes more physical effort than on a lighter bike, though the weight disappears once rolling.
Softail Slim - Buying & Maintenance Guide
What to check before buying
When inspecting a used 2018 Harley-Davidson Softail Slim with its 1746 cc custom / cruiser, start with the basics: check the service book for oil change frequency, inspect the drivetrain for wear, and look for oil seepage around the engine casings and rocker covers. This model runs belt final drive, so check belt tension and tooth wear - a cracked or glazed belt is a clear sign of neglect. Now 8 years old, this custom / cruiser is as likely to show age-related wear (perished rubber, seized fasteners, degraded seals) as mileage-related wear. A cold start test is invaluable - a well-maintained Softail Slim should fire up cleanly and settle to a smooth idle within a few seconds.
Oil and filter changes
Regular oil changes are the single most important maintenance task for the Softail Slim's 1746 cc four stroke, v-twin, milwaukee-eight 107, pushrod-operated, overhead valves with hydraulic, self-adjusting lifters, 4 valves per cylinder. Stick to the manufacturer's interval - typically every 6,000 km or once a year, whichever comes first. With a 10.0:1 compression ratio, running the octane grade specified in the manual matters more than on a lower-compression engine. Always use the correct viscosity grade as specified in the owner's manual.
Fuel system care
The Softail Slim's fuel injection system is durable but benefits from quality fuel and the occasional use of a fuel-system cleaner additive. If the bike has been stored for more than three months, drain and replace the fuel to prevent varnish deposits in the injectors.
2018 Harley-Davidson Softail Slim - Frequently Asked Questions
What engine does the 2018 Harley-Davidson Softail Slim have?
The 2018 Harley-Davidson Softail Slim uses a Four stroke, V-Twin, Milwaukee-Eight 107, Pushrod-operated, overhead valves with hydraulic, self-adjusting lifters, 4 valves per cylinder engine with 1746 cc of displacement. It is air cooled.
How much does the 2018 Harley-Davidson Softail Slim weigh?
The 2018 Harley-Davidson Softail Slim weighs 304 kg. This is the manufacturer's wet figure.
How much torque does the 2018 Harley-Davidson Softail Slim produce?
The 2018 Harley-Davidson Softail Slim produces 145 Nm @ 3250 rpm of torque.
What is the fuel tank capacity of the 2018 Harley-Davidson Softail Slim?
The 2018 Harley-Davidson Softail Slim has an 18.9-litre fuel tank. At around 5-6 litres per 100 km, that is roughly 315-377 km between stops.
Is the 2018 Harley-Davidson Softail Slim suitable for shorter riders?
The 2018 Harley-Davidson Softail Slim has a seat height of 660 mm. This is a comfortable, accessible height for most riders.
What brakes does the 2018 Harley-Davidson Softail Slim have?
The 2018 Harley-Davidson Softail Slim uses single 292 mm discs, 4 piston caliper at the front and single 292 mm disc, 2 piston caliper at the rear.
What tyre sizes does the 2018 Harley-Davidson Softail Slim use?
The 2018 Harley-Davidson Softail Slim runs 130/90B16,53H,BW front and 150/80B1677H,BW rear tyres. A good selection of sport, touring and all-weather rubber is available in these sizes.
What gearbox does the 2018 Harley-Davidson Softail Slim have?
The 2018 Harley-Davidson Softail Slim is fitted with a 6 Speed transmission.
Harley-Davidson Softail Slim Spec Evolution
The Harley-Davidson Softail Slim was produced across 2 model years (2019-2021). The table below highlights the key specifications that changed across the production run - useful whether you are comparing years or tracking down a specific variant.
| Specification |
2019 |
2021 |
| Seat Height |
660 mm / 26 in |
Laden: 648 mm / 25.5 in Unladen: 660 mm / 26 in |
| Displacement |
1746 cc / 107 cub in |
1746 cc / 107 cu-in |
| Brakes - Front |
Single 292 mm discs, 4 piston caliper |
Single 300 mm discs, 4 piston fixed caliper |
| Brakes - Rear |
Single 292 mm disc, 2 piston caliper |
Single 292 mm disc, 2 piston floating caliper |
| Suspension - Front |
Showa Inverted forks |
Dual-bending valve 49 mm telescopic with aluminum fork triple clamps, dual rate spring, "beer can" covers |
| Suspension - Rear |
Mono Shock adjustable |
Hidden, free piston, coil-over monoshock, 43mm stroke; cam-style pre-load adjustment |
| Clutch |
Multi-plate, wet |
Mechanical, 10 plate wet, assist & conventional |
| Final Drive |
Belt |
Belt, 32/66 ratio |
Key Specifications
Engine
Four stroke, V-Twin, Milwaukee-Eight 107, Pushrod-operated, overhead valves with hydraulic, self-adjusting lifters, 4 valves per cylinder
Torque
145 Nm / 107 ft-lb @ 3250 rpm
Fuel Capacity
18.9 Litres / 5.0 US gal
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Full 2018 Harley-Davidson Softail Slim Specifications
Year
2018 - 19
Make Model
Harley Davidson Softail Slim
Seat Height
660 mm / 26 in
Wheelbase
1630 mm / 64.2 in
Ground Clearance
120 mm / 4.7 in
Length
2310 mm / 90.9 in
Dry Weight
291 kg / 642 lbs
Fuel Capacity
18.9 Litres / 5.0 US gal
Oil Capacity
4.7 Litres / 5 US qt
Wet Weight
304 kg / 671 lbs
Displacement
1746 cc / 107 cub in
Engine Detail
Four stroke, V-Twin, Milwaukee-Eight 107, Pushrod-operated, overhead valves with hydraulic, self-adjusting lifters, 4 valves per cylinder
Bore x Stroke
100 x 111 mm
Compression Ratio
10.0:1
Cooling System
Air cooled
Exhaust
2-into-1-into-2 dual side, catalyst in muffler
Fuel Induction
Electronic Sequential Port Fuel Injection (ESPFI)
Ignition
Single-fire, non-wasted, map-controlled spark ignition
Lubrication
Pressurized, dry-sump with oil cooler
Starter
Electric
Clutch
Multi-plate, wet
Final Drive
Belt
Gear Ratios
1st 9.311 / 2nd 6.454 / 3rd 4.793 / 4th 3.882 / 5th 3.307 / 6th 2.79:1
Primary Drive
Chain, 34/46 ratio
Transmission / Drive
6 Speed
Suspension - Front
Showa Inverted forks
Suspension - Rear
Mono Shock adjustable
Lean Angle
27.4°
Rake
30°
Trail
147 mm / 5.8 in
Brakes - Front
Single 292 mm discs, 4 piston caliper
Brakes - Rear
Single 292 mm disc, 2 piston caliper
Tyres - Front
130/90B16,53H,BW
Tyres - Rear
150/80B1677H,BW
Wheels
Gloss Black, Steel Laced
Specifications are compiled from manufacturer documentation and cross-referenced
technical sources, and corrected on an ongoing basis.
Spot an error? Let us know.
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