You found what looks like a great deal on boots. But how do you know if the plastic shell is still good?
A boot can look perfect on the outside while being dangerously brittle inside. Here’s how to test the shell and figure out what you’re actually getting when comparing options at any ski boots sale.
The Flex Test You Need to Know
This test takes about 30 seconds and tells you more than any visual inspection ever could.
Grab the boot with both hands. Place one hand on the lower shell near the toe and the other on the upper cuff. Now try to flex the boot forward, like your shin would when skiing. Pay attention to how it feels.
Fresh plastic will have smooth, consistent resistance. It should flex progressively and spring back to its original position quickly. You’ll feel some give, but it should feel controlled and elastic.
Degraded plastic feels completely different. It might be too stiff and barely move at all. Or it could feel weirdly soft and collapse too easily without much resistance. Sometimes you’ll hear small creaking or cracking sounds. These noises are the molecular structure breaking down.
The test works because plastic fatigue shows up in how the material responds to stress. When polymer chains break apart from age, the plastic loses its ability to flex and recover properly.
What the Shell Should Feel Like at Different Ages?
Here’s what you can expect based on boot age:
| Boot Age | Flex Feel | What It Means |
| 0-3 years | Smooth, elastic return | Shell is in prime condition |
| 4-6 years | Slightly stiffer, slower return | Usable but aging |
| 7-9 years | Very stiff or too soft | Approaching end of life |
| 10+ years | Brittle, unresponsive | Replace immediately |
When you’re checking boots at a sale, do this test before you even think about price. A $200 boot that’s 8 years old is a worse deal than a $400 boot that’s 2 years old. The newer boot will last you several more seasons.
The Thumb Press Method for Shell Walls
After the flex test, check the shell walls themselves.
Press your thumb firmly into the plastic on the lower shell, especially around the ankle area and near the toe box. Press hard enough that you’re really testing the material, not just touching it.
Good plastic will give slightly under pressure but push back. It feels firm and resilient. Bad plastic either won’t give at all (too brittle) or will feel chalky and weak. You might even leave a small indentation that doesn’t fully recover.
This happens because aged polyurethane loses plasticizers over time. The material becomes more rigid and prone to stress fractures. Once you know what to feel for, you can spot degraded boots in seconds.
Temperature Test for Advanced Checking
If you really want to know the shell condition, temperature tells you a lot.
Take the boots from a room-temperature environment and hold them for a few minutes. Fresh plastic warms up slightly from your body heat and feels more responsive. Degraded plastic stays cold and rigid.
You can also check how the boots react to cold. If possible, leave them in a cold car for an hour (around 0-10°F works well). Then bring them inside and try the flex test immediately.
Boots with good plastic will be stiff when cold but quickly become more pliable as they warm up. Boots with advanced degradation stay rigid much longer or crack under cold stress. Some boots will develop visible stress marks around buckle mounting points when flexed cold.
This temperature sensitivity happens because plastic degradation reduces the material’s ability to handle thermal changes. The polymer chains can’t move and adjust like they should.
How to Spot Hidden Damage During a Ski Boots Sale?
Sellers don’t always know (or tell you) the real condition of used boots. You need to check yourself.
Look closely at stress points. These are areas that take the most force: where buckles attach, the ankle pivot point, and the front of the toe box. Run your finger along these areas feeling for small cracks or rough spots. Sometimes you can feel damage before you can see it.
Check the color too. Plastic that’s been heavily UV exposed will look faded or slightly yellowed compared to areas that were protected. This discoloration means the material has been breaking down faster.
And here’s something most people miss: smell the inside of the boot near the shell. Seriously.
Degrading polyurethane sometimes gives off a slightly chemical or musty smell that’s different from normal boot funk. It’s subtle but noticeable once you know what to detect.
New Boots on Sale Can Be Old Too
Just because boots are “new” doesn’t mean they’re actually new. Shops sometimes sell old stock that’s been sitting in a warehouse for years.
Remember that plastic ages from the manufacturing date, not the purchase date. A pair of boots made in 2018 and sold “new” in 2024 is already 6 years old. You’re buying boots with 4-5 years of safe life left at most.
Always check the manufacture date. It’s usually stamped or molded somewhere on the shell.
Common spots include near the heel, on the back of the cuff, or on the inner shell wall. The date might be obvious like “2022” or coded as a production number you’ll need to research.
When you see deep discounts on “new” boots, this is often why. The shop needs to move old inventory. That 50% off deal might not be such a bargain if the boots only have a few seasons left.
Should You Buy Used or New?
It depends entirely on the age, not the condition.
A used boot from 2022 with 20 days of skiing is a better buy than a new boot from 2017 that’s never been worn. The 2022 boot has years of safe use ahead. The 2017 boot is already at the edge of its lifespan.
For used boots, you want something no more than 3-4 years old. This gives you at least 3-4 more seasons of reliable performance. Anything older than that is risky unless you’re getting it extremely cheap for occasional use.
For new boots on sale, check that manufacture date carefully. If they’re more than 2 years old, factor that into your decision. You’re not getting a full 8-10 year lifespan from those boots.
The plastic fatigue test gives you real information that pricing and appearance can’t. A boot that fails the flex test or thumb press isn’t worth buying at any price. Your safety depends on boots that can handle the forces of skiing without failing.
Frequently Asked Questions
How can I tell if a ski boot’s plastic shell is still good?
Answer: Perform the flex test: bend the boot forward and feel the resistance. Good plastic flexes smoothly and springs back; degraded plastic feels too stiff, too soft, or makes creaking/cracking noises.
What is the thumb press method and why is it useful?
Answer: Press firmly on the lower shell with your thumb. Healthy plastic gives slightly under pressure and springs back. Brittle or chalky plastic indicates aging or degradation.
Does temperature affect how I test ski boot plastic?
Answer: Yes. Fresh plastic warms up and becomes more pliable, while degraded plastic stays rigid and may crack under cold stress. Testing at different temperatures helps reveal hidden weaknesses.
Can “new” boots still be old?
Answer: Yes. Manufacturing date matters more than purchase date. Boots made years ago and sold as new may already have 4–6 years of use life lost due to plastic aging.
Should I buy used or new boots on sale?
Answer: Focus on age, not appearance. A lightly used boot under 3–4 years old is safer than a new boot that’s over 5 years old. Always check manufacture date and perform the flex and thumb press tests.
