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.

When selecting tires, mountain bikers often fixate on rubber compounds, tread patterns and weights, sometimes overlooking the construction of the casing and the additional layers applied to it. Not to dismiss the external features, but the hidden elements in a tire are equally important.

Although the bike tire market is rife with buzzwords and proprietary sounding technologies, basic tire construction is largely the same across the board. Casings are made of parallel nylon fibers coated with rubber to create the fabric’s desired thickness. The fibers are aligned at a 45º angle to the tire bead, often in multiple layers in alternating directions. Atop that foundation additional materials may be used to increase stiffness and defend against punctures and cuts. All of this before any tread is applied.

By carefully selecting materials and how they’re layered, product developers can create a tire with specific attributes. They can engineer tires with optimal rolling efficiency, lighter weight, beefed up durability, or built to charge hard on challenging surfaces. For this post, we asked Tim Krueger of Terrene Tires to walk us through the various layers and what they do.

Thread Counts & Plies

terrene tires are available with or without added protection layers in the casing.

Most tire buyers are familiar with the concept of thread count, but may not understand how it plays into durability and overall performance. Thread count refers to the number of individual fibers per inch in the casing’s base fabric. Typically grouped into two categories, low-count tires generally have 60 threads-per-inch whereas high-count tires have somewhere around 120. Some tires go as high as 170tpi or more, but those are usually reserved for professional racers on race day only.

mountain bike tire casing thread count examples shows what do mtb casings look like
Left to right are 27tpi, 60tpi, 120tpi and 170tpi casings.
how do mountain bike tire casing thread counts compare
A 120tpi casing (left) compared to a 170tpi casing. Both are very good, but note the reduced light showing through tighter spacing on the finer 170tpi fabric.

Lower thread counts use thicker threads with larger gaps between them. Higher thread counts pack more fibers per inch because those fibers are thinner, and more tightly packed.

As such, Krueger says higher thread counts require less rubber to coat the fine and tightly spaced threads. This yields a fabric with thinner rubber laminates and a lighter, more supple casing that’s able to flex more easily. The creates a tire that conforms to the trail better, and that compliance improves rolling efficiency, comfort, grip, and overall ride quality.

A 60tpi tire requires thicker applications of rubber resulting in more weight and a less pliable material. But there are advantages to low-count casings. The fibers in a 60tpi tire are more coarse and inherently more cut-resistant. Although not always the case, lower count tires, by virtue of their added rubber, are stiffer and a better choice for use in demanding terrain.

The Casing’s Contribution to Ride Quality

Terrene Tires Light casing cutaway to show minimal layers inside a mountain bike tire sidewall
Terrene’s Light tire casing eschews armored layers and uses a higher thread count nylon weave to save weight.

With the thread count chosen, tire designers then determine how many layers of casing material are required to achieve the desired results. A single-ply tire will usually offer the lowest rolling resistance at the expense of durability. The more plies that are added the more the cut and puncture resistance increases—at the sacrifice of rolling efficiency. The extra plies also stiffen the carcass. It gets more complex than just the layering of fabric. Although they’re technically not casing material, most tires include extra laminated layers to boost durability and stiffness as desired.

Krueger is quick to point out how thread count alone does not determine a tire’s performance characteristics. The additional layers and rubber laminates atop the casing impart as much if not more influence. This is a concept regularly measured and discussed in the findings of Jarno Bierman at bicyclerollingresistance.com.

If you cap a high-quality 120tpi casing with thick layers of rubber and stiff armored laminates, they will negate the advantages of the fabric. As such, it is possible to produce a 60tpi tire with better ride quality than one with twice the threads. For this reason, Krueger says they don’t add reinforcements to their 120tpi tires. Protective layers require extra rubber to incorporate into the tire and the added weight negates the benefits of the expensive high-count material.

Terrene Tires tough casing cutaway to show armor layers inside a mountain bike tire sidewall
Terrene Tires tough casing cutaway to show armor layers inside a mountain bike tire sidewall

As Krueger puts it, “This is the magic mix that sets manufacturers apart. Some use one-ply casings with protection layers. Others use two-ply with protection layers. At Terrene, we actually do all of those on different tires. We custom tune each tire for the type of riding it is intended for by using all methods of reinforcements.”

Terrene Tires light and tough casing cutaway to show armor layers inside a mountain bike tire sidewall comparison
Terrene Tires light and tough casing cutaway to show armor layers inside a mountain bike tire sidewall comparison

He went on to explain how the protective elements within tires are changing with the times. With advancements in suspension, wheel designs, and perhaps just due to the evolving skills of today’s riders, tires are being pushed to new limits. Sidewalls are now as likely, if not more so, to see damage as the tread surface. But they can also be used to support really aggressive riding while still allowing lower tire pressure.

Krueger offers this advice regarding the nuances of tire selection: Some people advise putting a more durable tire, often a reinforced 60tpi tire, on the back wheel with a lighter 120tpi skin up front. However, the front wheel can take as much abuse as the rear. Knowing how you ride and honestly assessing the demands you place on your tires will guide you to the appropriate product.

In a future installment of Tire Tech we’ll take a much closer look at tire reinforcements, how they’re integrated into the casings and why.


This Episode is presented by Terrene Tires. At Terrene, we put riding at the center of the experience. We understand what matters most—be it an afternoon on your favorite stretch of singletrack, a long day on an unending dirt road, or a worldwide tour. We took what we have learned through decades in the bicycle industry to bring you tires that are designed to ride how you do. From the very beginning of the process until the tread hits the dirt, we bring together our experience in product development and a passion for riding to create tires that are ready to ride for people that live to.

Pumped on this? Got a question you want answered? Email us. Want your brand or product featured? We can do that, too.

16 COMMENTS

  1. Nice write up, on a side note Continental measure their casing TPI different than the rest of the industry, they count each layer. So their “180 TPI” casings are 3x 90TPI, otherwise known as “90TPI” using the rest of the industry measurement.

  2. So, which tire should I use on the Chupacabra trail in Santa Cruz? What about Airborne, which is in the next canyon over? I usually switch tires mid-ride so that I am dialed. But near the bottom of Airborne, it get rocky, so I need to switch to a thicker casing tire. But when I get on the road to get back to my car, I then switch to a 1.9 fast-rolling tire.

    (Yes, I am making fun of people who ask which tire to use on a given trail on internet forums, not realizing that the 60 people with 60 different replies are going to make their decision that much more difficult.)

  3. Flatbiller – next month we will be releasing our wifi-enabled rubber with durometer changing nanoparticles, which will allow you to change your compound makeup right from your smartphone. That should help.

  4. Hardly surprising sidewalls are more likely to be damaged than in the old days. Wider rims means the profile is less rounded, so the sidewall is less protected by the tread. Lower pressures mean the tyre is more likely to get pinched between the rim and a rock. Running tubeless also means we’re more likely to care about a tiny nick in the sidewall.

    • Thats an interesting one. So, sidewalls leak because of small gaps in the casing fabric that were not filled with laminate rubber. Higher tpi fabrics can be laminated thinner and lighter, and when you use less rubber overall, you have a higher likelihood of this happening. Of course, more laminate rubber can be applied to the sidewalls to ensure that this doesn’t happen, but then that adds weight to the tire.

      So, the honest answer to your question? The heavier ones.

  5. Why are sidewalls damaged more often than in the past when we ran tubes? It seems like the tube would not do anything to improve durability, vs. tubeless. Pre-tubeless, I ran much lighter tires without sidewall protection and they seem to hold up. But now I have to run thicker and protected casing tires to prevent cuts. The other variables are lower pressure, wider rims, and perhaps more speed?

  6. Mr. P – as you guessed, correlation does not mean causation. The tube does do a bit to stiffen the tire, which is why people say tubeless “rides better” – the tire is more compliant. However, that is probably little to do with the phenomenon that you and a lot of other people notice. We think the change in demand for Tougher tires, and people abusing tires more than before is more due to the increase in bike technology – we can put a lot more abuse into a tire now that we have bombproof carbon rims strapped to 170mm travel wonderbikes than we did when we had 21mm wide aluminum rims and 80mm travel bikes.

  7. What a great series of articles. I would have liked more detail on thread count as mentioned in other comments. 3×60 is 180 with some brands. In the drawings above there are two plys in the sidewalls and three under the tread is that considered a 2ply or 3ply? Please write up a follow on to this chapter..

What do you think?