Sensitivity and Stiffness in Climbing Shoes

The subject of sensitivity in climbing shoes is a nerdy one. When climbers start talking about how a hold feels, or how much feedback they get from one shoe over another, it is safe to say things are pretty far in the weeds. But you don’t have to be a super geek to know that not every shoe is going to provide the same feeling on every surface or style of climbing. In this post we’ll dive into why these differences exist, and the key things to keep an eye on when you’re comparing shoe models.

What Affects Stiffness & Sensitivity

There are a handful of factors at play in how sensitive our shoes are and it helps to know how climbing shoes are constructed. We’ve covered all the details of shoe construction here: how shoes are made but the need to know, now, is:

• Upper – what wraps around your foot (also where the lacing/velcro/slipper closure is located).
• Sole / Outsole – the rubber bottom of the shoe that is in contact with the rock or climbing wall.
• Midsole – the material(s) that sit between the upper and outsole. This is hidden from the eye and is the area where a shoe designer adds support or creates flexibility (across the entire foot, the middle of the foot, or only the toe area).

These basic areas of construction are all at play when discussing sensitivity, as they can all influence the overall feel and performance of the shoe when we wear it. How our foot interacts with the shoe greatly dictates how our shoe provides feedback from the wall.

Upper Fit

A loose upper can mean that the shoe is able to move around the foot, making the climbing ‘feel’ soupy or less precise. A shoe can’t provide feedback if it isn’t touching as much of our foot as possible. An overly tight upper can also constrict blood flow and lead to pain and even numbness in the toes, also not ideal. The job of the upper in this case is to keep your foot in contact with as much of the midsole as possible, without being too tight.

Situations like this are the main reason it is so important to find a shoe that fits properly in size and length and width and volume. If you want to be able to dial in how sensitive your shoes feel, it is essential that they fit correctly first.

Outsole Thickness

One major component in how much you can feel what you’re standing on is how much rubber there is between you and the wall. Most brands mention sole thickness in the specs of their shoes which can range from as thin as 2.5 mm (very rare) to 5mm of rubber underfoot. As a rule of thumb, when the amount of rubber in a sole increases, the amount of feedback or ability to feel tiny changes in holds decreases. Many climbers who seek maximum feedback and sensitivity in a shoe start by looking for the thinnest soles.

Across all the climbing brands, you’ll notice these rubber thicknesses trends:

• Shoes designed for newer climbers (like the La Sportiva Tarantula or SCARPA Origin) prioritize longevity, durability, and comfort so they have the most rubber, often with a 5mm outsole. When the shoe inevitably scrapes/drags against the climbing wall, the rubber doesn’t wear out / get a hole in them as fast as thinner soled models.
• Shoes designed to prioritize stiffness over flexibility/sensitivity, like many crack climbing shoes or even stiff performance shoes meant for the smallest edges are usually in the 4mm range.
• Performance sport and bouldering shoes that prioritize softness/flexibility/sensitivity will be most commonly be in the 3 – 3.5mm range.

Some manufacturers use multiple pieces of rubber to create the outsole (versus one piece) have a variable thickness. Shoes could also have thinner rubber at the back of the shoe and thicker rubber in the front of the shoe, to give the toes additional support to stand on small holds.

Midsole Thickness and Flexibility

The job of the midsole is to add support to specific areas of your foot as you climb. This added support comes at a cost of less sensitivity, simply by adding more material under your foot. Because of this tradeoff, the thickness of the midsole is also something that shoe brands can (should!) mention in their tech specs. Most shoe designers try to keep their midsoles as thin as possible while still providing the stiffness and support the shoe is designed for.

Similar to rubber thickness, a thinner midsole generally means more feeling is transferred from the climbing holds to you, and a thicker more supportive midsole reduces sensitivity.

In order to accomplish this balance of support vs feel there are a ton of different materials used in midsoles, from thin, flexible polyesters, rubbers, and plastic impregnated fabrics to super stiff carbon and polycarbonate plastics (the same stuff that is used to make climbing helmets).

Climbing Rubber Differences

Rubber can range from highly flexible and squishy to very stiff and resistant to deformation. Generally, climbing on small, delicate holds like edges and crystals is made much easier when the sole of your shoe is stiffer and more supportive. Rubbers on the stiffer side will still generally provide less sensitivity to holds than softer rubbers, however.

On the other hand, maximizing rubber softness means maximizing the amount of subtle changes in shape and texture you can sense with your feet, increasing sensitivity and making delicate and balancey climbing more stable. Climbing in this high friction style, you want as much rubber contacting the wall as possible, so softer rubber is ideal because it deforms and conforms so easily.

It is important to note that not every rubber is the same. Shoe brands spend a huge amount of time and effort either sourcing specific rubber or developing their own proprietary secret sauce. Because of this variety and secrecy, it is difficult to directly compare one rubber type to another, which has created much opinion and argument between climbers over the years. For the purposes of sensitivity, it is thankfully only necessary to know that they vary in stiffness, which is possible discern:

• Check out the shoe charts and marketing for the brand of shoe you are comparing and look for their comparison between their versions of rubber. Usually these charts share which rubbers are softer/stickier and which ones are made to be durable or stiff.
• Try on and handle as many shoes as possible. With your hand, squish the rubber edge at the toe of the shoe, or push your fingernail into the rubber – you can feel which rubber is softer and bends/deforms more easily than another.
• Squeeze and bend and fold shoes side by side. Note the deformation and how resistant the shoe is to return to shape. (This is complicated by the construction of the midsole and how thick / how many pieces the sole is)

Overall, there aren’t that many different rubber types, and they’re all similar enough that there is no agreement of which rubbers are best or worse – an added impossibility because the temperature and type of rock (or hold compound) change how the rubber reacts significantly.

Basically, if you find a rubber to be particularly sticky or that edges well for you, keep with it. Just don’t be afraid to try out all the other rubber types at the next shoe demo.

Balancing Stiffness & Flexibility

When we look at the overall construction of a shoe as a stack of really specific choices made by shoe designers, we can start to see why there is such a wide range of shoes available.

When looking for a more sensitive shoe, check the specs!

• Thinner/softer midsoles transmit the most feeling
• Thinner rubber outsoles will leave you closer to the wall
• Look for soft rubber – some brands will note this feature specifically. Be aware that soft rubber deforms better, but wears faster.

Protip: Stiffer midsole materials like plastic can sometimes be used to compensate for the softness in rubber and provide more support, often resulting in a less sensitive shoe. If the brand doesn’t mention midsole materials or thickness, the only way to know how soft and sensitive a shoe will be is to hold it, bend it, and try it on.

If you want a more supportive shoe, still check the specs!

• Thicker midsoles made of plastics offer more stiffness than fabric or rubber midsole tech.
• Stiff shoes wear longer thanks to all the support, making them better for long climbing days and taller routes.
• The more support you get from a shoe, the less you should expect to feel tiny holds and changes in friction.
• Rubber on the stiffer end of the spectrum will help your shoe hold your weight better.

Remember: More supportive shoes are about balancing key areas of stiffness as thin as possible to help shoes retain some sensitivity. Each brand approaches this in their own way, so it is most helpful to actually handle a shoe and squeeze it in your hand to feel for flexibility when you twist and fold the shoe side to side and front to back.