Repurposed running shoes: how to make your own “rock plate”

A good trail running shoe needs two essential characteristics: stability and traction. Obviously there are other features that you may throw out there like cushioning, durable and/or water proof exterior, and protection. However, what I typically find in trail shoes are over built, clunky heavy weights that all but nullify trail feel; my first pair of Saucony shoes were like blocks of wood.

Part of the problem, in my opinion, is the overemphasis on the rock plate, that rigid mystery layer that often adds significant weight and results in the loss of a significant amount of proprioception. For pure trail races, we often have to compromise based on what’s available, because most road shoes provide too little traction on loose trails. But what about mixed trails and hard pack surfaces? Many XTerra Tri runs are “trail light” courses, so a light weight road race shoe can be a good choice with a little added protection. Here’s how I addressed this problem using a pair of Saucony Grid Type 4a racers.

Lightweight = Light protection

The Saucony Grid Type 4a is a very lightweight (under 6 oz) 4 mm drop racing shoe. I’ve run 1/2 marathons in these, but in general they’re best for shorter races. Earlier this year I needed a fast shoe for those XTerra’s that were lighter on trails and stability needs, and this shoe fit the bill. However, like most lightweight shoes, the mid-sole is relatively thin and provides little protection against sharp rocks. To make matters worse, this shoe has drainage hole that easily catch small rocks than can push into the shoe interior (see below). So with that in mind, and the Richmond XTerra coming up, I made use of materials from my recycling bin to add a little protection.

Those drainage holes are a problem.

Those drainage holes are a problem.

Clear evidence of rock infiltration.

Clear evidence of rock infiltration.

Have recycling, will reuse

I don’t really know what difference companies use for a rock plate, but what I do know, is the more protection it offers the heavier it is and the less feedback your feet get. For truly gnarly trails, I’ll go with a trail shoe, but for this retro fit I needed a material that was highly puncture resistance and flexible, but easy to work with. The obvious solution was plastic from a milk jug. However, as I dug through my bin, I spotted a giant Arizona Tea jug in my neighbors bin. PERFECT!

I wanted puncture resistant and I got it, because even my utility knife required some effort to cut it. After cutting two large pieces out, I then trimmed them to match the insole shape; subsequent testing indicated that I go narrower to avoid any overflow and contact with my barefoot (bad!). I also realized that I would have enough plastic to cover the length of the shoe, so I opted for more forefoot protection, which turned out to not be enough; more on that later.

Cut to fit.

Cut to fit.

Once cut to fit, I put them in the shoe and heated them with a hairdryer, replace the insole and wore the shoes for 10 min to “customize” the fit; probably not necessary. I then removed them, wet the inside of the shoe as indicated on the Gorilla Glue bottle, applied the glue to the bottom of the insert, and then slid them into place. I again replaced the insole and wore the shoes for about 20 min to allow the glue set under compression (Gorilla Glue expands). That’s it, the shoes were ready to race.

Apply Gorilla Glue (follow the directions).

Apply Gorilla Glue (follow the directions).

Insert the in the shoe.

Insert the in the shoe.

The Verdict?

Overall, the plate worked as expected. I know this, because the heel had no protection, and despite the added cushioning, I had a rock puncture the inside and cause me some minor grief in my race. It was enough to make me want to added some protection there too. The only other issue I had was that I need to fasten the insole too, because it slid forward and bunched up at the front. Lessons learned, but in opinion this project was so effective, I might modify some NB Minimus trail shoes as a more trail specific alternative.

Give it try and let me know how it works!

Next time, I’ll discuss how I modified a pair of INOV-8 X-talon’s to perform better across terrain.

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