When it comes to climbing shoe rubber, everyone talks about stickiness, edging, and durability — and Evolv’s Trax SAS HF 4mm rubber is a compound that delivers on all three fronts. If you’re thinking about resoling your Evolv shoes or just curious how this rubber performs, this post breaks it down clearly.

Whether you’re bouldering indoors, projecting sport routes, or just want reliable friction underfoot, here’s what you need to know about Trax SAS HF.

What Is Evolv Trax SAS HF?

Trax SAS HF stands for "Superior Adhesion System – High Friction", and it’s Evolv’s softest and stickiest rubber compound currently in production. It was developed to offer maximum grip on all surfaces, especially in steep, technical, or competition-style climbing.

At 4mm thickness, it balances sensitivity with enough rubber to give your shoes a reasonable lifespan — especially when used on softer surfaces like gym holds.

Trax SAS HF Rubber: Performance Breakdown

Friction

• This rubber’s top selling point is friction.
• It performs incredibly well on indoor volumes, slick feet, polished rock, and slopers.
• On steep terrain, the softness helps the rubber conform to features and give you a more secure feel.

Sensitivity

• Because it’s a soft compound, you get excellent sensitivity underfoot.
• That makes it easier to feel small features and adjust your foot placement mid-move.

Support & Edging

• Compared to firmer rubbers (like Vibram XS Edge or Unparallel RH), Trax SAS HF is less supportive.
• It’s not designed for standing on tiny edges for long periods — but that’s the tradeoff for max grip.

Durability

• As a softer compound, it wears faster than stiffer rubbers, especially on rough outdoor rock.
• That said, it's ideal for indoor climbers and those looking for performance over longevity.

Best Uses for Trax SAS HF

Trax SAS HF is a performance-focused rubber — it's not for every shoe or every climber, but if you value grip and feel over edge support or long-term durability, it’s a solid choice.

Best for:

• Indoor bouldering and sport climbing
• Steep terrain and dynamic movement
• Shoes used for comps or high-friction needs
• Smearing, scumming, toe-hooks, and technical footwork

Not ideal for:

• Long trad routes
• Granite edging
• Climbers looking for maximum durability

Should You Resole With Trax SAS HF?

If you’ve worn out a pair of Evolv shoes that originally came with Trax SAS, resoling with the HF 4mm compound keeps the feel consistent. It’s a great option if your shoes were designed for friction-based climbing or you’re mainly using them indoors.

Want to get your shoes back in action with Trax SAS HF? I’ve got access to this rubber in 4mm sheets, perfect for a fresh resole with max stick.