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Tire Tech: Why you should measure tire wear with a tread depth gauge

Bontrager's new tread depth gauge can help determine when to replace a tire.
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Welcome to Tire Tech, Bikerumor’s mostly-weekly series on bicycle tires. Like our Suspension Tech and AASQ series, we take your questions about tires, whether it’s road, cyclocross, fat, plus, gravel, or mountain bike, and get answers from the brands and people behind them.

In the last few editions of our Tire Tech series, we discussed knob patterns and how much engineering goes into the perfect tread design. Part of the process includes complex rubber compound formulas created to produce the grip and speed riders demand. The durability of that compound determines how much fun you get to have before buying your next set of treads.

Every rider has at some point burned into a turn only to realize their tires are—worn out. A cooked tire brakes poorly, feels sketchy in a hard lean, and spins wildly when grinding up steep climbs. You might be able to get away with thin rubber when conditions are tacky, but once the trail gets dry and loose, it’s obvious when you have ridden past your tires’ expiration date.

How & why to measure mountain tire tread depth

Bontrager's new tread depth gauge can help determine when to replace a tire.

For most riders, the only way to gauge tread wear is to eyeball the knobs and try to remember what they looked like on day one. A more accurate way is to use something like the new Bontrager Tire Tread Depth Gauge. It’s a simple tool offering an instant assessment of tire life.

By placing the gauge on the tread adjacent to the lug and lowering the unit to plunge the needle, users can instantly determine how much tread remains. A corresponding chart lists all of the tires in the Bontrager catalog for consistent reference…but, obviously, the gauge works on any brand of tire.

For performance pedants, the Bontrager gauge provides repeatable readings so riders can assess the precise moment when their favorite tire is about to fade beyond an acceptable range. As a shop tool, it helps bike mechanics convey the need to replace a worn tire beyond the typical, “Dude, your tires are shot. Gimme another $150.

Bontrager's new tread depth gauge can help determine when to replace a tire.

The real advantage of the gauge to the consumer is having the ability to measure the tire’s life cycle as it wears down. Although it’s seldom designed into the product, the degredation in a tire’s performance as it wears is not always linear. Some tires begin to struggle shortly after the first 10-15% of the tread is worn down. Others soldier on until the bitter end when the last of the rubber gives up the ghost. Which means if you always run the same tires on your bike, taking routine measurements and performance notes in a journal will help you learn when your favorite tires should be replaced.

The Bontrager gauge retails for $24.99 and is one of few designed specifically for mountain bikes…but you’ll have to ask your Trek dealer to order you one because, for now, it’s sold as a shop tool for dealers. But there are a number of options on Amazon ranging from cheap $5 plastic sticks to more expensive digital options. Whichever you choose, the gauge helps riders know when their favorite tire has given up its best miles, and certainly their last. It can not only save riders from un-fun days squirming around on the trail, but it could also prevent catastrophic tire damage. Or, you could always go with the shop guy’s assessment, “Dude, you need new tires.


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18 Comments
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boom
boom
6 years ago

It’s sold on their website: https://www.trekbikes.com/us/en_US/equipment/cycling-accessories/bike-tools-maintenance/bontrager-tire-tread-depth-gauge/p/14627/?colorCode=black
Also, those cheap ones on Amazon don’t appear to be near as accurate as that Bontrager one. We use it in our shop and it’s an easy story to tell with customers for tires (except road ones obviously)

i
i
6 years ago
Reply to  boom

I’m sure the Trek-branded one is a lot more accurate because it’s totally not a $6 harborfrieght item with a Bontrager sticker on it. It’s way more accurate than the shop guy saying ‘dude, your tires are totally worn, gimme $150.’ Now it’s ‘I measured your tires with a tool from the tire company and it totally says you need to give me $150.’
Right. So your LBS gets a little more like a shady auto tire store. Just what I’ve been hoping for.

Now, serious question: who replaces tires because the center knobs are worn? Vs the side knobs getting torn?

mattmcculley
6 years ago

Needs audible readout, because you clearly would only need this if blind.

boom
boom
6 years ago
Reply to  mattmcculley

Right, and I’m sure you can also tell how worn your chain is by looking at it too /s

Fred Gravelly
Fred Gravelly
6 years ago
Reply to  boom

Hope they make a grip wear indicator too… It’s virtually impossible to tell when they are worn out

Erv Spanks
Erv Spanks
6 years ago
Reply to  Fred Gravelly

That WAS going to be a Sea Otter exclusive.

Kyle Riedel
6 years ago
Reply to  mattmcculley

The blind can read braille just fine.

elvis
elvis
6 years ago

Heeelarryus and +1 Matt

james horton
james horton
6 years ago

mot fail on tyres under 1.6mm

Tom
Tom
6 years ago

a caliper would achieve the same thing, and offer other capabilities, at a lower price.
As an indicator of functionality, depth certainly has some bearing, but the age of the compound and the sharpness of the knobs is also very important, though harder to measure.

B
B
6 years ago

Next up a frame wear indicator.

Longbeard
Longbeard
6 years ago

We need it because the industry says so. How dare you question that!

caliente
caliente
6 years ago

only 24.99??! I’ll take two!

Billy Thompkins
Billy Thompkins
6 years ago

Why you should measure tire wear with a tread depth gauge? (deleted)

Bmx
Bmx
6 years ago

Compare front that has no wear with rear that has done.

Imagine the embarrassment of somebody finding your tyre wear journal . Jesus

JBikes
JBikes
6 years ago

Finally! Now I just need a tool to tell me my water bottles are empty and I’m gold

Chris
Chris
6 years ago

With knobbly tyres, it’s easy to see when they’re worn. Really cannot fathom why anyone would need to use anything other than Mk1 eyeballs to measure that.
Slick tyres present more of a problem – a gauge to measure tread thinning would be much more useful!

George p burdell
George p burdell
2 years ago

Glad I found this article. Feeling a bit guilty about replacing a bontrager se4 rear tire. It has rounded center knobs at 1.9mm. Last ride it was slipping on steep loose over hard. Visually the tire looks like it has life but it’s grip is less than mediocre. Judging from bontrager chart above, they are done. I notice the sipeing is probably at the 2.5mm depth on chart because they are gone on the center knows too.

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