Adidas SL20 review
The SL20 is a competent tempo running shoe for distances less than 10km, but it suffers from a very narrow fitting upper and manufacturing defects where the upper separates from the midsole.
Lightstrike was supposed to be Adidas' next big thing, but it falls short. It feels stiff and too firm to be a super foam that competes with the ZoomX and Floatride foams of the world.
Adidas SL20 and the emergence of Lightstrike foam
Seven years ago, when Adidas introduced their Boost foam, it was a marvel. There was nothing on the market that was as bouncy and responsive.
Since then, Boost has been overtaken by other technologies that are lighter and even more responsive such as Nike's ZoomX, Reebok's Floatride, and Saucony's Pwrrun+ foams.
Adidas fell asleep and didn't innovate for many years, so now they have to play catch up. 2020 is the year of Lightstrike. Lightstrike is the new TPU foam from Adidas designed to compete with the modern super foams of today.
Lightstrike was first used by Adidas in their basketball shoes and has been filtered through to the running sector.
The SL in SL20 stands for super light, and while not much lighter than other tempo running shoes, it is much lighter than Adidas Boost shoes which is a step in the right direction.
The SL20 is a fast, tempo running shoe, so it competes with the Nike Zoom Rival Fly, the New Balance 1400, Skechers Razor 3 and even Adidas' own Boston Boost.
This is confusing because the Boston Boost has got Lightstrike in its midsole combined with Boost. So, which is the superior Adidas shoe, and how does the SL20 fit in the Adidas running shoe range?
SL20 upper: a few things went off
The SL20's upper is made from a breathable mesh. It has a thin tongue which is not gusseted, but it is attached at the bottom half of the tongue, so it doesn't move around at all.
When putting the shoe on, the tongue feels like it's a centimetre too short but you forget about it during the run. The heel counter is traditional and doesn't flare out like other Adidas shoes such as the Ultraboost and Solar Boost.
The heel counter is not very secure, so I had to do a lacing heel lock to stop my heel from slipping out during workouts.
The fit of the SL20 is very narrow. It may be the most narrow shoe I've ever tried on. It was tricky getting the lacing right without it feeling uncomfortable.
If I loosened it too much, the crease in the forefoot poked into my foot, so I had to adjust it just right so that it was tight but not unbearably tight. You definitely need to go up a half size.
The designers of the SL20 said that they wanted the shoe to look like a laser beam, and I think they did a great job because it's an amazing looking shoe. The colours and the silhouette are just screaming fast.
One thing I have zero tolerance for is manufacturing defects because returning shoes back is a chore. The SL20 has one big problem: the midsole separates from the upper on both sides.
This happened having run less than 100km, which should not happen with a company as big as Adidas to a shoe they have spent millions marketing.
Some shoes such as the Adios Boost and the Boston Boost have a combination of Boost foam and Lightstrike foam but the SL20 and its sister shoe, the RC2.0 have a full Lightstrike midsole.
The Lightstrike midsole is firm. It feels like a traditional EVA midsole but with some slight rebound. It's a snappy midsole and suited for tempo runs under 10km. Anything longer and the firm midsole is too harsh on the feet.
I went for tempo runs, long runs and daily runs in the SL20 and the shoe felt best for those 5km speed workouts which last less than 30 minutes.
Boost was revolutionary, but Lightstrike just doesn't have that sparkle or wow factor. For a technology that has just come out, it feels like an old foam from 6 years ago in the pre-Boost era.
Outsole performance: 50/50
The forefoot is made from durable Continental rubber which grips well and has a soft underfoot feel. The rearfoot is made from Adiwear, which is softer and not as durable as the forefoot. The midfoot around the Torsion shank is exposed.
The Torsion shank provides midfoot stability and helps the forefoot snap back into its original position when it flexes.
The Continental rubber in the forefoot is showing no signs of wear. Still, the outsole durability is let down by the Adiwear rubber in the rearfoot which is wearing down extremely fast.
The midsole is made from TPU so it shouldn't lose much cushioning over the lifespan of the shoe.
The shank keeps it stable
The midsole is firm, so the SL20 is a stable shoe. It is also low to the ground, so you feel planted when running in them. There is no lean bias.
The torsion shank helps to keep the shoe rigid through the midfoot and provides structure.
The SL20 has a snappy forefoot, which flexes up in the front of the shoe.
The insole is flat and doesn't add much cushioning. It has the wording "Lightstrike" on it just in case you forget that the midsole is made from it. It has a soft fabric material glued on top of it that gathers sock material after a while.
Adidas SL20 vs Nike Zoom Rival Fly 2
The Nike shoe has a better, more accommodating upper. The Adidas midsole is thicker and has more protection for longer runs.
Both shoes are great value for money, but the Rival Fly 2 is more comfortable and has a more robust build. I choose the Zoom Rival Fly 2.
Adidas SL20 vs Skechers Razor 3
The Skechers shoe has a better upper and a softer midsole. The Razor 3 is better for long runs, but the SL20 is better for short runs.
The Adidas shoe is cheaper than the Skechers, but I'd still choose the Razor 3 for the bouncy, smoother ride.
Adidas SL20 vs Adidas Boston Boost 9
The Boston 9 has a more accommodating, better upper and has a softer midsole due to the Boost. The Boston has a more durable outsole due to having more Continental rubber.
The Boston beats the SL20 in every department and is the far superior shoe.
So, where does the SL20 fit into the Adidas running shoe lineup? It doesn't. There isn't a single reason to choose the SL20 over the Boston Boost. Yes, the SL20 is firmer and faster, but then the Adios Boost is the better choice.
The SL20 is not a shoe worth getting excited about and not a shoe that I look forward to running in with so many better options out there to choose from in the tempo running shoe category.
Adidas will have to keep on searching for their new Boost.
Tip: see the best running shoes.