Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In

Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In


Gear Guy

Optimal Temperature for Sticky Rubber?

Lock Icon

Become a member to unlock this story and receive other great perks.

Already have an Outside Account? Sign in

Outside+ Logo

Intro Offer
$3.99 / month*

  • A $500 value with 25+ benefits including:
  • Access to all member-only content on all 17 publications in the Outside network like Rock and Ice, Climbing, Outside, Backpacker, Trail Runner and more
  • Annual subscription to Climbing magazine.
  • Annual gear guides for climbing, camping, skiing, cycling, and more
  • Gaia GPS Premium with hundreds of maps and global trail recommendations, a $39.99 value
  • Outside Learn, our new online education hub loaded with more than 2,000 videos across 450 lessons including 6 Weeks to Stronger Fingers and Strength Training for Injury Prevention
  • Premium access to Outside TV and 1,000+ hours of exclusive shows
  • Annual subscription to Outside magazine
Join Outside+

*Outside memberships are billed annually. Print subscriptions available to U.S. residents only. You may cancel your membership at anytime, but no refunds will be issued for payments already made. Upon cancellation, you will have access to your membership through the end of your paid year. More Details

A friend warms his climbing shoes in his armpits. I said that sticky rubber works best at low temps and that he shouldn’t heat up the soles. We agreed to settle the argument by Googling. Most articles say the optimal range for rubber stickiness is 32 to 40 degrees. At what temperature is friction the highest?


Google? Little more than glorified spyware that tracks your every move and records it forever. Heating the rubber could make it stickier and probably does, but a blanket statement won’t tell the entire story. Different shoes use different rubbers cooked differently. Always, there’s a tradeoff between making rubber more elastic, or softer, and keeping it firm enough to hold on edges. This is why edging shoes can have harder rubber, and slippers tend to have gummy rubber. Making rubber, any vulcanizer will tell you, is an art. Glassy holds are best attacked with stickiness, but granite chips succumb most favorably to a firm rubber.

Your buddy might be on to something, or he could be a weirdo. They say that sniffing your armpit can instantly if briefly boost your energy. Perhaps that is his secret. Warming rock shoes under your arms will soften the rubber, though fleetingly if the rock is cold. In the days of old when it was brisk outside we’d flip our E.B.s sole side up like basking rattlesnakes and let the sun warm them. Didn’t help but we kept trying.

The optimal temperature for shoe rubber is anecdotal. Determining what works best for you is as scientific as it gets. The range you found, 32 to 40 degrees, seems cold to me, especially for the appendages not encased in shoes.

My shoes feel best when the air temp is 50 to 60 degrees, but it’s not like I carry a thermometer or can always control the weather. When my shoes feel icy and boardy I might tuck them under a jacket and sometimes I rub the soles together until they stick to one another.

If your buddy believes that warming his shoes in his armpits is helping, no need to say otherwise. Just keep in mind that the holds he steps on will soon be your handholds. Think about that before you head out for Ethiopian food. Gear Guy has spoken!

This Gear Guy question appeared in Rock and Ice issue 251 (July 2018).

Got a question? Email:

Feature image: Tommy Lisbin.

Also Read

Gear Guy: Should I Resole My Rock Shoes?

Gear Guy: Is a Flat Rope Safe?

Gear Guy: Will Dog Urine Harm My Rope?