Icebug Acceleritas 5 RB9X Review

Icebug Acceleritas 5 RB9X

Icebug is a small independent Swedish company with one primary goal – to create shoes with outstanding traction for running and walking in any kind of weather. And when they say outstanding traction, they mean the best in the world. If you think that the company offers only a few types of shoes, then you are in a big lack of knowledge. Icebug currently sales more than 40 models from everyday and working shoes to ultra light trail racing shoes.

Icebug Acceleritas 5 RB9X is a minimalistic and light, low drop racer for trails, swimrun or obstacle races. Maybe you will ask yourself about the name of the shoe. OK – probably Acceleritas comes from acceleration, it is cool, I like it, creates feeling of fast speed but what is RB9X? To leave the most interesting stuff for the end of the review, let’s start with the upper first. It uses woven nylon and protective polyurethane for soft, light and durable coverage. The interior lining utilizes a quick drying mesh to keep the foot dry at all times – the water pickup is minimal, the drainage is excellent and hence the wet weight is almost as low as when it’s dry.

The midsole is very flexible and it’s made of compression molded lightweight EVA material. Icebug have developed their own system for categorization and comparison of their shoes. 3 levels of torsion are available – Easy Flex, Medium Flex and Stability Flex. Acceleritas 5 is with least torsion which means that the foot has less support and has to work more on its own. The natural movement builds strength but is also demanding. More torsion (medium flex or stability flex) offers more support which is an advantage for feet that don’t have sufficient strength or during long sessions when feet get tired. The purpose of Acceleritas 5 is for short and fast races, where the weight is very important, not long and more relaxed ultramarathons so the choice of Easy Flex is understandable.

The drop of the Acceleritas is 4mm, most shoes have a drop between 4 and 10mm, some special models are with 0 drop which equals as standing barefoot on the floor. More drop is for most perceived as more comfortable. Less drop is more like the natural position of the foot, but it also puts more strain on the muscles and tendons of the foot. Again, Acceleritas is a racing shoe where less drop is recommended.

The cushioning is thin but responsive – it has better contact with the ground, but also demands more from the runner.

Icebug Acceleritas 5 RB9X

The biggest plus of the shoe and and in general all products from Icebug is the outsole and the grip. The outsole is designed with a pattern that is optimized to grip on hard and soft surface, with an aggressive pattern where dirt is steered away to the sides in diagonal channels. The outsole is made of RB9X, short for Rubber 9 Extreme – innovative rubber compound that provides incredible traction on both wet and dry surfaces, without compromising the durability. Icebug are very proud with the Rubber 9 Extreme for a good reason.  Grip is phenomenal both on ascends and descends, on almost vertical rocks. In general the shoe is Ideal for technical ascends and less ideal for technical descends, because lack of cushioning and some loose foot movement in the shoe (if feet are skinny). The fit is narrow, but the mesh is flexible enough so the foot does not feel constrained too much. The end of the tongue can cause some rubbing when shoe is tested in store or walked around with, but the feeling disappears while running. Lugs are spaced perfectly so that no mud is retained. Some debris can get into the shoe, there are some holes at the bottom of the tongue, probably made for the water to drain.

The Acceleritas5 RB9X from Icebug is a neutral trail running shoe that’s great for fast trail races.

Icebug Acceleritas 5 RB9X













  • Great grip
  • Perfect shoe for for technical ascends
  • Fast and nimble


  • Lack of cushioning
  • Narrow fit