Adding an insole raises your foot inside the shoe. Your heel sits higher than the shoe was designed for, so it no longer seats fully into the heel counter and lifts away as you walk.
The short version: check that you removed the factory insole first, then re-lace using a heel lock. Between them, those two fixes resolve most cases. If the slip persists, a heel grip or a lower-volume insole is the next step.
Why Insoles Cause Heel Slip
Heel slip after adding an insole is a height problem, not a length problem. The shoe has not changed size. Your foot has moved upward inside it.
The heel counter is the stiff cup at the back of a shoe. It is shaped to wrap the heel at a specific height, and it holds the foot in place by gripping around and just above the heel bone. When an insole lifts your foot by even a few millimetres, the heel rides toward the top edge of that counter, where there is less material to hold it. The grip weakens, and the heel starts to lift on each step.
This is why heel slip often appears immediately after fitting new insoles in shoes that fit fine the day before. It also explains why thicker, more cushioned insoles cause it more often than thin ones.
How to Stop Heel Slipping: Five Fixes in Order
Work through these in sequence. The first two are free and solve the majority of cases, so there is no reason to buy anything before trying them.
Fix 1: Check that you removed the factory insole
Most shoes ship with a thin insole already inside. If you added a new insole on top without taking the original out, you have stacked two insoles and roughly doubled the height you added.
Take the shoe, reach in at the heel, and lift. Most factory insoles are loose or lightly tacked and will come out with a firm pull. Some shoes have footbeds glued down or stitched in, and those cannot be removed.
This is the single most common cause of heel slip after fitting insoles, and it takes ten seconds to check.
Fix 2: Re-lace using a heel lock
A heel lock, also called a runner’s loop, uses the top eyelet pair to pull your ankle back and down into the heel counter. It is the most effective free fix available, and most people have never been shown it.
Full instructions are in the next section.
Fix 3: Add a heel grip or tongue pad
A heel grip is an adhesive foam or suede pad that sticks inside the back of the shoe and adds friction against your heel. A tongue pad sits under the tongue and pushes your foot backward into the heel counter.
Tongue pads are the more useful of the two and the less commonly used. If your foot is sliding forward slightly, pushing it back seats the heel properly, which a heel grip alone will not do.
Fit these after the insole is already in the shoe, so you are positioning them against the real geometry rather than the empty shoe.
Fix 4: Switch to a lower-volume or three-quarter insole
If the slip persists, the insole is too thick for that shoe. Volume, not size, is what you need to reduce.
A three-quarter-length insole ends behind the ball of the foot and adds no height at all under the heel, which removes the cause entirely while keeping arch support. A thinner full-length insole is the other option.
Neither is a compromise on quality. It is a fit decision, in the same way that a shoe that fits one foot shape well may not fit another.
Fix 5: Reassess the shoe itself
Sometimes the honest answer is that the shoe is slightly too large, and the factory insole was quietly compensating for it. Removing it exposed the real fit.
If lock-lacing, a tongue pad, and a thinner insole have all failed, the shoe is likely half a size too big for you. No insole will correct that.
How to Tie a Heel Lock, Step by Step
The heel lock uses the two top eyelets, the ones most people never thread. It takes about thirty seconds once you have done it twice.
- Lace normally up to the second-from-top eyelet. Stop there, with a lace end on each side.
- Thread each lace up into the top eyelet on the same side, going from outside to inside. Do not cross over. This creates a small vertical loop on each side of the shoe.
- Pass each lace end through the opposite loop. The left lace goes through the right loop, the right lace goes through the left loop.
- Pull both ends down and outward. You should feel the loops cinch and your ankle pull backward into the heel of the shoe.
- Tie normally. The tension should feel firm around the ankle without pressure across the top of the foot.
If your foot goes numb or the ankle feels pinched, the lock is too tight. Loosen the lower eyelets rather than the lock itself. The lock is meant to hold the ankle while the forefoot stays relaxed.
Not every shoe has the extra eyelet. If yours does not, a tongue pad is the closest equivalent.
Why Heel Slip Is Worth Fixing
Heel movement causes friction, and friction on skin over a few kilometres produces blisters. That is the immediate reason to fix it.
There is a second reason. A heel that lifts on each step means the shoe is no longer moving with your foot, so some of the effort you put into each stride goes into moving the shoe rather than moving you. Over a long walk or run, that is wasted energy and a less stable footing on uneven ground.
Neither of these makes heel slip an injury risk in itself. It is an uncomfortable and inefficient fit problem, and it is almost always fixable in a few minutes.
When the Insole Is Not the Problem
Rule these out before spending money on a different insole.
- The shoe is worn out. Heel counters soften with age. A shoe that has done several hundred kilometres may no longer grip regardless of what is inside it.
- The laces are not actually tight. Many people lace the forefoot firmly and leave the top two eyelets slack, which is precisely where heel hold comes from.
- Sock choice. Thin, slippery synthetic socks reduce friction against the heel. A slightly thicker sock with some texture can resolve mild slip on its own.
- It only happens in one shoe. That usually points to the shoe rather than the insole. Feet are commonly different sizes, and the larger foot’s shoe often fits the smaller foot loosely.
Frequently Asked Questions (FAQs)
Q1. How much heel movement is normal?
A small amount of movement when you first put the shoe on is normal and usually disappears once laced properly.
Q2. Will heel grips work with insoles already in the shoe?
Yes, and you should fit them in that order. Put the insole in first, then position the heel grip against the actual space that remains. Fitting the grip to an empty shoe usually puts it in the wrong place.
Q3. Should I go down a shoe size instead?
Not as a first step. Sizing down reduces toe room as well as heel volume, and you can end up trading heel slip for a cramped forefoot. Try lock-lacing and a lower-volume insole first. If both fail, the shoe may genuinely be too large.
Q4. Why does it only happen in one shoe?
Most people have one foot slightly larger than the other, and shoes are sold in matched pairs sized for the larger one. The smaller foot sits in marginally more space, so adding an insole tips that shoe into heel slip while the other stays fine.
Q5. Do thicker socks fix heel slip?
They can help with mild cases by adding friction and taking up a little volume. They are a reasonable stopgap but not a solution. A thick sock also adds volume at the forefoot, which can create a new problem while masking the original one.