Bikes and riding styles have changed dramatically in the recent decade. Tires? Not so much. Look no further than the Maxxis Minion DHF and DHR II for proof of that. Minions have remained relatively unchanged since many riders were riding plastic tricycles. Today, improved geometry and enduro-ready suspension have bestowed super powers upon average trail riders, who now can straight-line chunder, survive jumps and maintain speeds that were once unimaginable. Tire technology, however, has fallen behind. This article explores the cost and weight penalties that modern riders shoulder in order to keep air inside their tires and their rims in one piece. It also suggests that there may be a better solution.
Why Mess With Success? What If?
Foam tire inserts, two-ply downhill tire casings, inner tubes that look like alien reproductive organs, and shock-absorbing rim liners all offer some level of additional protection and performance - which begs the question: What if you gave tire makers a performance improvement budget that included the equivalent weight and price increases of all those extras, could one of them produce the next super tire?
Shouldn't be too much of a task. Lightweight bullet-proof vests, slice-proof Kevlar gloves and chainsaw-proof pants are common items. A puncture proof tire seems like small potatoes by contrast. Cush Core
inserts weigh 250 grams each. That's a lot of material to work with for a designer who was actually serious about ending pinch flats and protecting rims. Then there's the extra padding to cover the costs of those improvements. Inserts cost around $75 USD each, and the up-charge from a trail bike tire to the DH version is another 20 bucks. You can see where I'm going with this.Apparently, Tire Brands Don't Think There's a Problem
Could tires be significantly improved? Two years ago, I initiated conversations
with the major tire makers about the possibility of any new technologies, materials or construction techniques that could solve fundamental shortcomings that mountain bike riders have accepted as necessary evils. Sidewall slashes, pinch-flat shearing, bead separations, burping, bent rim flanges, and the litany of minor punctures that so often derail a ride or race. The answer then was a short-list of excuses. along with the assurance that tires are way better now than they were then. I'll paraphrase a few of them for you:
In Support of Tire Makers...
I've visited a few tire factories and can tell you that the steps required to make a good bicycle tire are many. The process is a mixture of steampunk and rocket science. Some of the machines are automated. Others are iron monstrosities from another era.
Experience is the gold standard in a rubber factory, where chemists in white lab coats share equal status with sage factory workers in dirty overalls. "No pictures, please." Secrecy is the code, because the key ingredient of a perfect tire could be anything from a modified chain of molecules, to finely ground walnut shells, or an eight-degree angle in the casing fabric.
Welcome to heavy industry. Aromatic and hot, when the assembly line is in is full swing, wads of hot sticky stuff pop and bubble between massive rollers in the mixer; rubber and fabric are being sliced, squeezed and mated together; ribbons of tread roll overhead on pulleys towards the fabrication drums, where workers join the beads, casings and tread rubber in to a circle; then somehow, those featureless flat rolls emerge from pressurized, steaming-hot vulcanizing molds as finished tires, bristling with knobs, with all the hot patches neatly in place.
I marvel that this process can produce such tight tolerances - tires that weight within ten grams of each other and bead diameters that must be held to a millimeter. It's clear that today's tires represent an accumulation of knowledge eked from 150 years of incremental evolution. Images from Matt Wragg's Continental factory story.
At least for now, all three of the above statements ring true. If every tire maker (actual manufacturers, like Kenda, Maxxis, Schwalbe, Conti, Vittoria & Hutchinson) shares the same construction methods and materials, if the most popular tread patterns mirror the Minion's DNA, if they're winning races, and if riders and OEM customers are buying them up as delivered, then who's going to jump at the opportunity and risk seven figures to re-invent the mountain bike tire? Given that the sport's most influential riders grew up on a diet of Minion clones, there's also a good chance that, regardless of merit, any
challenge to the status quo would be summarily dismissed. So, why bother?Three Good Reasons to Redesign Tires 1 - Keeping air inside the tire:
Tubeless has been the only significant leap in tire technology since the birth of the mountain bike. To make tubeless work, however, the tire casing must be air-tight, abrasion resistant and tear proof. Strange then, that only a handful of DH-rated dual-ply tires could earn better than a C plus in any of those categories. We expect punctures, slashed casings and abrasion tears. The tube and CO2 device taped to our frames broadcast our complacency.
Punctures in the tread area are uncommon, but lighter, faster-rolling single-ply tires are prone to fatal sidewall injuries. Adding a 250-gram insert can ward off pinch flat shearing, but can't guard against rips and abrasion damage. The popular fix is to take the 300-gram weight penalty and use dual-ply (DH) tires. Four layers of rubber and nylon side-wall fabric are better than two. The downside isn't just extra weight, it's the unwanted stiffness. Conventional dual-ply construction results in six layers of fabric under the tread, which creates a harsh ride and increases the tire's rolling resistance.
The Fix: Red Bull TV offers proof enough that adding more layers of nylon and rubber has not produced tires that can hold up to today's riders. Let's ditch all the layers and the fancy breaker strips completely, then resolve the durability and puncture
issue with a truly slash and puncture proof casing material - good enough to carry a one year guarantee. Some hybrid of Kevlar and nylon comes to mind, but there are a handful of super-fiber options to choose from. I anticipate that such a fabric would be heavier and less supple than the existing nylon material, but the sum game would be to split the difference; gaining some extra lateral support in the casing sides, while maintaining the more flexible and faster rolling aspects of the single-ply tire in the crown area. 2 - System integration:
Grab some popcorn, because we'll be watching videos to clarify the importance of the next two improvements. Let's begin with the Cush Core effect. Arguably the most effective of the present crop of foam inserts, Adam Krefting's winged insert squeezes between the walls of the tire casing at full compression, which prevents the folds from contacting each other and causing the shearing damage we call pinch flats. Another benefit is that the insert cushions impacts that would normally damage the rim.
Cush Core's video duplicates Jo Klieber's slo-mo experiments, which suggest that suspension's action could be improved by altering the compression rate of the tire.
Cush Core's most dynamic contribution, however may be its influence on the suspension's action - an effect first identified by Syntace founder Jo Klieber, who also co-designed the Schwalbe ProCore system. Watch the Cush Core video and you'll see that, upon impact, the tire nearly compresses to the rim before the suspension begins to activate. Inserts assist the process by ramping up the tire's natural spring rate as the tire fully compresses, which kicks the suspension into gear a fraction of a second sooner, providing a more seamless transition. The penalty of all that goodness is 250 grams per wheel in a place where every gram of rotating weight can be felt. Could there be a way to integrate the benefits of an insert into the design of the tire itself?The Fix:
Changing the shape of the tire where it interfaces with the rim and incorporating a slow-memory cushion could integrate some of the benefits of closed cell foam inserts while eliminating most of their weight and complexity. The concept is not a new one. A number of mountain bike tires feature cushioned bead areas, but not to the extent I am suggesting here. Look to motocross racing tires. Their designers have incorporated a shelf-type bead cushion which could serve as a starting point to explore the concept.
Unlike Cush Core, a cushion molded into the tire's bead interface could not prevent the casing folds from direct contact. That said, the presumption that the tire maker will have used a tear-proof casing fabric would negate any pinch flat issues. The built-in cushion would buffer and disperse the energy of bottom-out and near-bottoming impacts across a larger portion of the rim, increasing its survivability, and to some degree, would also function to ramp up the compression rate of the tire to activate the suspension earlier and in a more controlled manner. 3 - Address the new school riding style:
Beyond speed and amplitude, fundamental changes in geometry and riding technique have placed greater demands upon the tire's edging tread. Slack head tube angles force the rear wheel to follow the front. Add that to rider-forward cockpits and suddenly we're steering much more aggressively and loading up the front tire to the degree where riders are using the handlebars to force the rear wheel to comply.
There are plenty of hooning shredits on PB to illustrate that. The more interesting change to suggest we need a tire redesign is illustrated by this video from the Les Gets World Cup DH. Watch how Amaury Pierron races most of the course point to point. He waits to pressurize each turn until he's right at the apex, boom! and then almost skims the surface to the next corner. The Fix:
No secret. Tire designs that edge extremely well are quickly rising to prominence. Schwalbe's Magic Mary ruled supreme until competitors caught on. Maxxis' Assegai was heckled when it arrived, but nobody is laughing at it now. Take it to the next level. The unicorn that we need to progress now is a tire with crazy edging grip, but rolls fast and pedals efficiently when you stand it up. One suggestion is to ditch the six-layer crown casing for a more flexible crown tread. Another idea is to abandon the present light-bulb tire profile (which does not flex uniformly and requires a lot of reinforcement to stabilize it laterally) and try a lower profile with a more hemispherical shape.
It's not a stretch. MX front tires (front tires are always coasting, so the technology applies) are nearly hemispherical, assisted by the wider stance of their shouldered bead profiles. Back to cycling, road racing clinchers mounted to wider rims also create a near-hemispherical arc and roll significantly faster over rough pavement - and with more stability in high-pressure turns. May be worth a look. How Much Will this Thing Cost?
Expensive, but not out of reach for enthusiast and elite-level riders. If such a tire debuted on PB today, it's doubtful that you'd be able to buy a pair for one or two years at any price. High development costs and lengthy timeframes are the norm for truly innovative tire concepts. Rubber is picky about the materials it will bond with, so selecting and proving a suitable super-fabric would require much laboratory time. Any type of stepped and cushioned bead would need to integrate with existing tubeless rims, or possibly require a modified rim with a locking bead. Sussing out the finer details of a high performance tire like this would be a racers-only work in progress until the patents were secured and the tire was earning podiums.
Regardless of the cost to develop such a tire, its MSRP, weight and wear would have to reflect those of its conventional competitors. My guess is that number would hover close to $125 USD initially for the halo racing version, with more affordable models filling in later as OEMs put pressure on the manufacturer. That said, I'd still expect at least a 25-percent upcharge from existing premium tires.
The real value, beyond the promise of next-level cornering and survivability, would be additional cost and weight offsets due to the fact that you would not need to purchase inserts, nor bear the burden of riding a quarter inch thick rubber donut emblazoned with a DH hot patch to ensure you'll make it to the bottom of your next gravity run. And there's also the assurance that you'd be able to ride them until the fabric was showing. Realistically, I'd estimate the weight to split the difference between a sturdy trail-rated single-ply tire and a DH-rated dual-ply model. So, the target would be a DH/enduro race-winning tire that costs $125 USD and weighs 1000 grams.
Where Do We Go From Here?
I don't pretend to be a tire designer, but like you, I ride, so I feel I have a stake in the game. I also believe that it doesn't help to complain about the status quo unless you can suggest a different option. That's what this story was about - starting a dialogue that, hopefully, will inspire meaningful improvements.
This rekindling of the tire debate was inspired while riding, where I was pondering the recent leap in trail bike performance. Trail bikes evolved from cross-country, so it took 30 years of reluctant incremental evolution to get to 150 millimeters of travel and a head angle slacker than 69 degrees. Somewhere around that point, probably inspired by rudimentary enduro racing, downhillers started riding trail bikes en-masse.
It was gravity riders who wrestled the trail bike away from the stodgy XC mindset and magnetized its development to DH. Why not kick the head angle out to 65 degrees? Why not add 100mm to the reach? Why not pedal around with a coil shock? Why not ride a 180mm fork? Why not put dropper posts on everything that has knobby tires?
For a while, everything seemed possible. An average trail bike today is mental compared to a decade ago. Even pro XC racing benefitted from the influx of brash ideas. How then, did tire design miss that boat? Perhaps downhillers couldn't imagine a better tire could possibly exist. Bottom line: we'll never know how much faster or how much more fun a break-through tire design could be until someone makes one. So, the question is: "Why not?"
What it costs to keep air in your tires: Maxxis Minion DHF
Cecile Ravanel repairs a mid-race puncture.
3C Maxx Grip 27.5 x 2.5
Weight: 1160gMaxxis Minion DHR
3C Maxx Grip 27.5 x 2.5
Weight: 1190gCush Core Pro inserts
Weight: 250gStan's NoTubes Kit
Weight: apx.150gTotal MSRP: $393 USD
Total weight: 2750g