Footwear

Choosing Grip Strength In Ultra Running Shoes

I face-planted spectacularly during a training run three years ago. Wet roots, moderate downhill, moving maybe 8-minute-mile pace – not even pushing hard. My shoes slipped completely and I hit the ground before my brain registered what happened.

Turned out, the road-oriented trail shoes I was wearing had shallow lugs designed for groomed paths, not technical single-track. They looked rugged with their aggressive styling, but the actual traction was garbage on anything slippery.

That crash taught me to actually understand lug patterns, rubber compounds, and how different grip designs work across varied terrain. Traction matters way more than I’d appreciated – you can’t run fast if you’re tentative about footing, and you definitely can’t finish ultras if you’re sliding around constantly.

Lug Depth And Pattern Design

Lug depth determines how well shoes bite into soft or loose surfaces. Deeper lugs penetrate further, gripping terrain that shallow lugs just skim across.

Road trail shoes use 2-3mm lugs suitable for maintained paths and light trails. These work fine on hardpack but offer minimal traction in mud, loose dirt, or wet conditions.

True trail and ultra shoes feature 4-6mm lugs that grip effectively across varied terrain. This depth handles most conditions ultra runners encounter without being overly specialized.

Extreme muddy condition shoes like Salomon Speedcross have 7-8mm lugs that absolutely dominate wet, sloppy terrain. But they wear fast on rock and feel awkward on hardpack.

I run in Pacific Northwest forests where mud is constant half the year. Shoes with 4-5mm lugs work perfectly – enough bite for slippery conditions without being mud-specific. The 6mm lugs I tried felt like overkill and wore down quickly on occasional dry sections.

Lug pattern affects how well shoes shed mud versus pack solid. Wide-spaced lugs clear mud better but provide less total grip. Tightly-spaced lugs maximize traction but fill with mud and become useless.

Rubber Compound Hardness

Softer rubber grips better but wears faster. Harder rubber lasts longer but provides less traction. Every shoe balances these tradeoffs differently.

Sticky rubber compounds used in approach and climbing shoes offer incredible grip on rock and wet surfaces. Some ultra shoes use similar compounds for maximum traction at the cost of quick wear.

I tested shoes with super-soft rubber that gripped amazingly well on wet rock and roots. They wore completely smooth after 250 miles – terrible lifespan for ultra training. The grip was fantastic while it lasted though.

Standard trail shoe rubber offers balanced durability and traction. You get 400-500 miles of lifespan with adequate grip for most conditions. Not the absolute best traction, but good enough while lasting reasonably.

Carbon rubber – extremely hard compounds – lasts forever but feels slippery on wet or smooth surfaces. Road shoes use carbon rubber for 500+ mile lifespans. Trail conditions demand softer, grippier compounds.

When comparing grip options, consider your typical terrain and how quickly you burn through shoes. Wet, technical trails justify softer rubber despite faster wear. Dry, rocky trails work fine with harder, more durable compounds.

Lug Geometry And Shape

Multidirectional lugs provide traction during climbing, descending, and lateral movement. Directional lugs optimize for specific movements but sacrifice versatility.

Brake lugs – deeper, more aggressive patterns on the forefoot – enhance downhill control by preventing forward sliding. Climbing lugs on the heel and arch engage during uphill.

I prefer shoes with multidirectional lug patterns for varied terrain. Some courses have technical descents, steep climbs, and everything between. Specialized patterns work great in specific conditions but feel compromised elsewhere.

Pointed versus rounded lug tips affect bite and durability differently. Sharper points penetrate surfaces better initially but wear round quickly. Blunt lugs last longer but don’t bite as aggressively.

Wide flat lugs provide stability on rock and hardpack. Narrow lugs penetrate loose soil better. Some shoes combine different lug shapes strategically – flat lugs on the outsides for stability, pointed lugs in the center for bite.

Surface-Specific Traction Needs

Rocky terrain requires different traction than mud, sand, or roots. Matching lug design to your primary surface improves safety and efficiency.

Rock and hardpack benefit from multidirectional, moderate-depth lugs with sticky rubber. Deep lugs don’t help much on solid surfaces – it’s about rubber compound and contact area.

I ran Utah desert ultras where the terrain was slickrock, sand, and hardpack. Aggressive mud shoes would’ve been terrible – the deep lugs wear fast on rock and fill with sand. Moderate lugs with sticky rubber worked perfectly.

Mud demands deep lugs with wide spacing to shed buildup. Tightly-packed lugs become useless skating rinks when they pack solid with mud.

Loose dirt and trail need deeper lugs that penetrate and grab. Shallow lugs just slide across loose surfaces without biting.

Wet roots and rocks require sticky rubber compounds more than lug depth. The softer rubber conforms to irregular surfaces and grips through surface moisture.

Wet Versus Dry Performance

Many shoes that grip excellently in dry conditions become skating rinks when wet. Others maintain traction across conditions.

Hydrophobic rubber coatings help shed water and maintain grip when wet. Without these treatments, some rubbers become slippery once saturated.

I’ve run shoes that worked great on dry trails but were terrifyingly slick on wet roots. The compound just didn’t grip through moisture. Switching to shoes with better wet traction transformed confidence on rainy runs.

Drainage features affect wet performance too. Shoes that hold water become heavy and the saturated materials lose grip. Mesh that drains quickly maintains performance in wet conditions.

Lug edges matter in wet conditions – sharper edges cut through water and mud to grip the surface beneath. Rounded, worn lugs skate across moisture without penetrating.

Traction Versus Weight Tradeoffs

Maximum traction requires deep lugs, lots of rubber, and heavy construction. Lightweight shoes sacrifice some grip for reduced weight.

Racing flats with minimal outsoles feel fast but sketchy on technical terrain. The weight savings aren’t worth the traction compromise for ultra distances with significant vertical.

I tried racing an ultra in lightweight shoes to save ounces. Felt great on smooth sections but I had to slow dramatically on technical descents because the traction wasn’t confidence-inspiring. Lost more time being cautious than the weight saved.

Most ultra runners benefit more from confidence-inspiring traction than minimal weight. The mental energy spent worrying about footing outweighs the fatigue from a few extra ounces.

Balance exists around 9-11 ounces with adequate traction for most terrain. Lighter than that usually means traction compromises. Heavier often means excessive outsole that doesn’t add proportional benefit.