Sole Fitness ST90
The Sole ST90 is a residential treadmill that bridges the gap to commercial grade with its defining feature: a slat belt design powered by a 2.0 HP AC motor. Unlike traditional belts, the slat surface reduces friction and wear while providing a distinct, firm road-feel. It features a 15.6" touchscreen with native apps and screen mirroring, aiming to offer a high-end experience without the mandatory subscription fees of competitors.
Community Intel
“Mixed. Users universally praise the durability and running feel of the slat belt, often comparing it favorably to Woodway in terms of stability. However, there is significant frustration regarding the electronics; users complain about 'horrible' speakers, a laggy Android interface, and a 'useless' fan. The AC motor noise (a hum/pulsing sound) catches some residential users off guard. General consensus: Buy it for the hardware/deck, not the smart features.”
Positives
- Slat belt design offers superior durability and a realistic road-feel
- AC Motor (Alternating Current) is designed for higher longevity than standard DC motors
- Heavy-duty 'tank-like' build quality with a 400 lb weight capacity
- No mandatory monthly subscription required for screen usage (Netflix/YouTube included)
Negatives
- High price point ($3,999) compared to other Sole models
- AC motor is louder and produces more vibration than comparable DC motors
- Touchscreen interface is reported as laggy with sub-par speaker quality
- Warranty is significantly shorter than Sole's standard lifetime coverage (5yr motor/frame)
- Very heavy (376 lbs) and difficult to move/assemble
Technical Data
01 // Unique Features
The headline feature of the ST90 is undoubtedly the slat belt. Unlike a standard continuous belt that drags over a deck, the ST90 uses individual rubber slats that roll on bearings. This design—typically reserved for $10,000+ commercial machines like Woodway—reduces friction, increases belt life, and creates a firmer, more 'outdoor' running feel. Additionally, the machine offers a 'Free Mode' where the motor disengages, allowing the user to power the belt manually, turning it into a sled-push trainer.
02 // Performance
The running experience is where the ST90 shines and justifies its existence. The 2.0 HP AC motor (don't let the low HP number fool you; AC motors deliver continuous torque far more efficiently than the DC motors found in most home treadmills) powers the slats smoothly up to 12.5 mph. Runners will notice the surface feels harder than a cushion-flex deck but absorbs shock effectively through mechanical structure rather than soft elastomers. However, users should be aware that AC motors are inherently louder, producing a distinct hum that might be intrusive in a small room.
03 // Technology
This is the ST90's Achilles' heel. While it boasts a 15.6" touchscreen with preloaded apps like Netflix and YouTube, and screen mirroring capabilities, the execution falls short of the price tag. The interface is often described as sluggish, and the lack of Apple Health/Google Fit integration is a miss for data nerds. Unlike Peloton, you aren't locked into a subscription, which is a major value add, but don't expect the software polish of a dedicated tech company. The built-in speakers are widely criticized as tinny, so plan on using Bluetooth headphones.
04 // Build Quality & Reliability
Weighing in at nearly 380 lbs, the ST90 is an absolute tank. It does not fold, and moving it requires a team, but that mass translates to zero wobble even during maximum exertion. The use of an AC motor suggests a lifespan that should far exceed typical residential units. However, Sole's warranty on this unit is surprisingly short—5 years on the motor/frame compared to the 'Lifetime' warranty found on their cheaper F80/F85 models. This likely reflects the higher cost of slat belt components but is a disappointment at the $4,000 price point.
05 // The Verdict
The Sole ST90 is a specialized tool for a specific runner. If you are a high-mileage athlete looking for the specific feel and durability of a slat belt without paying Woodway prices, this is one of the few viable options in the residential market. It is a runner's machine first and a smart device second. If you prioritize a polished software experience, silent operation, or need to move the machine often, you are better off with a high-end DC treadmill like the Sole F89 or a NordicTrack. But for pure biomechanical performance and hardware durability, the ST90 is a heavy-hitting contender.