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 most recent edition of our Tire Tech series, we talked with a few experts about tread designs for mountain bike tires and how they’re developed. While there are similarities in the process from one brand to the next, there are a few differences as well. This week we push the discussion further down the trail with Bontrager’s tire guru, Frank Stacy.

Throughout my interviews with various tire engineers, I started each session with the same basic question: What is the first phase of tire design? The answers vary, but usually the need to create a fresh tire involves a gap in product offerings, a need to replace stale models, or other changes in the market like new wheel formats and evolutions in consumer expectations or riding styles. Most people agree, today’s riders are pushing tires harder than they were ten years ago. If there is one major catalyst, it’s the widening of rims and tires in general, but we’ll dive down that rabbit hole another day.

We talk to Frank Stacy of Bontrager about tread designs.

When asked the opening question about new tire designs, Stacy said they often initiate a new tire project by using an existing model as a starting point.  He said, “We determine the pros and cons of a current tire, and/or a competitor’s tire. We evaluate performance through a rigorous, worst-case testing program that in most cases includes professional athletes and weekend riders of different levels. We focus on several areas including climbing, braking, handling, rolling, traction, deflection, sidewall roll, absorption, puncture resistance, etc.”

Although not every tire engineer and product manager I’ve talked to said it so clearly, I deduce all new tires have their roots in an existing product. As is the case for most things in cycling, new tires are usually incremental improvements over a previously successful tire.

Once the Bontrager tire team has fully evaluated an existing model, they use that information to advance their project. The tests help determine which elements to retain and which to adjust. In Stacy’s words, “Once we’ve determined the performance goals, we design the tread. Initially, all treads are designed in 2D. The focus is on function first; biting edges, tread spacing, tread self-cleaning, minimizing rolling resistance, tread depth, knob support, weight, etc. It can take several revisions to finalize the 2D design. Once the 2D drawing is ready we create a 3D drawing. If all looks good we create the 3D rapid prototype model for a final approval before mold making.”

We talk to Frank Stacy of Bontrager about tread designs.

The process of designing the tread pattern itself is driven by the specificity of the tire’s intended purpose. If you read our primer on knob types and how they’re used to create a particular ride quality, you know this is a blend of craft and science. It is also greatly influenced by experience. A good tire designer understands how to apply various tread features to achieve a particular objective. And they know how to factor in the nuance of wheel diameter and rim width. According to Stacy, designing a tread pattern for a plus-size tire demands a different approach than creating patterns for a thinner 29er tire. “For larger wheel diameter tires, due to the longer footprint, in some cases we’ve reduced the number of pitch (section of the tread that repeats) and/or reduced tread depth. This also helps reduce weight.”

With the 3D rapid prototype in the process of being made, Bontrager’s team then begins completing the tire recipe with close evaluations of the casing construction and rubber compounds required to maximize the design. To that end, Stacy said, “We use a combination of lab tests and field tests, studying puncture resistance, TLR air retention, pinch flat resistance, rolling resistance, etc. When the first prototype samples are ready, we test again to make sure we hit our goals. The new product is always benchmarked against an existing Bontrager tire and several competitors. If it’s a race purpose tire, we’ll prove the product performance at the World Cup level. If all goes well, the tire is released to production. If not, it’s back to the drawing board.”

And with that last bit, a reoccurring theme enters the discussion once again. As we learned from talking to tire designers with Continental, Schwalbe, Terrene, and Specialized, time on the dirt is the most telling. Long after the 3D concepts are developed, the rapid prototypes made, and the lab tests concluded, it is the evaluations on the trail that matter most. It is the feedback from professionals, recreational riders, and engineers which eventually guides the final product. It’s not a quick process, either. From start to finish Stacy said a new tire can take up to two years to complete.

In our next installment of Tire Tech, we’ll take a look at tread effectiveness as it degrades with use. We will look at a new tool for measuring tread life, and how wear is factored into tire life.


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

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14 COMMENTS

    • That’s a good question and it might vary depending on the manufacturer. In some cases, I’ve been told it somewhat mirrors the actual production process, but instead of ramping up multiple lines of production, they’ll just make a small test batch. Some manufacturers have made it sound somewhat easy. I suppose that all depends on their manufacturing resources.

  1. Stacy, please, do something with Chupacabra, because the grip on wet and on snow does not exist. By far the most dangerous tire I’ve had in my life.

    • The chupacabra is an all round tire that is better in dry and hard pack terrain. What tire pressure are you running? What size? My experience with the 27.5×2.8 Chupacabra has been surprisingly positive on packed snow. If you’re not having luck with the Chupacabra (Now known as the XR2) you should probably try the XR4 or the SE4.

  2. Where’s the beef in this article? I suppose that the title is accurate in that this does tell “how” the treads are designed, but previous articles led me to believe this would also include the “why” a tread is designed a particular way. The above article basically just describes a regular old generic product development process.

    Examples of the type of info that would be informative to include are:

    – When they were designing their G4 Team Issue, pictured above, which was heavily “inspired” by the Maxxis Minion DHF, why did Bontrager decide to reverse the orientation of the “L” shaped side lugs vs. the Maxxis design?

    – What traits does an “L” knob leading with the corner have vs. an identical knob leading with the end?

    – What made them use an “L” knob at all, vs. another G4 iteration they offered with all side knobs more ore less straight?

    – When Bontrager was designing the SE5, which seems heavily inspired by the Minion DHF, why did they decide to keep the Maxxis style orientation of the knobs?

    And all those questions are just inspired by the single tire pictured above! If you have a tire guru like Frank Stacy on the line, I’d also want to ask him what his take is on the Schwalbe style side knobs, that appear to be angled in the reverse direction from nearly all tires that have come before them (a knob orientation that WTB has now copied). Since Stacy also has motorcycle tire experience, I’d want to ask him about motocross treads vs. bike treads, and why motos seem to still use square blocks, whereas you see all sorts of crazy shaped knobs on bikes, supposedly to benefit from more “working edges”. Why would bikes need more “working edges”, but motos don’t, or is it just a marketing and tradition thing?

    • Fair point, but this is a multi-part series, and more information is coming. I would also add, sometimes these product developers are a bit coy about why they do, exactly what they do. Trade secrets and all that. And for a few, it’s not all science, but experience. Maybe the orientation of a knob is borrowed from a previous tire they liked, or influenced by trends with competitor’s tires. If I dove down the rabbit hole of each knob they ever designed, I’d put you to sleep, and they might not even be inclined to tell me. But, more info is coming and from some pretty cool sources.

      But, the process is interesting as well.

    • I would also like to know the answer to those questions! As for the moto vs bike tread patterns I think rolling resistance will be the main factor. Without and engine transfering moto tread patterns to bike tires would make them slow. Just look at Schwalbe Dirty Dan as an example. It is a mud/soft conditions tire and is very moto inspired. It is a hell of a tire with a ton of grip but of course it is slow rolling unless you are going downhill. I would love to see more moto inspired tires myself because I want maximum grip and don’t mind losing some rolling resistance.

  3. “In our next installment of Tire Tech, we’ll take a look at tread effectiveness as it degrades with use. We will look at a new tool for measuring tread life, and how wear is factored into tire life.”

    I look forward to this.

  4. What did I just not read? Nothing here at all. Tire companies first need to research what width rim is going on which bike for what kind of riding. Once that is determined then tire casing and width can be hammered out along with profile. “Then” tire tread. This is simple tire economics. Not very hard at all. So why do they get it wrong or produce mediocre tires.
    Trying to please too many people at the same time. More specializing needs to happen and let us choose what product to buy. A xc/touring/enduro/road tire is just not possible. Stop trying to combine tires. It’s a bad idea.

    • That deserves a reply as you are correct. All of the tire designers I spoke to address rim width and tire volume first. That’s the foundation on which the tread sits and it determines where the side knobs sit, etc. That was more clearly outlined in my Part One tread piece.

      I can’t speak to your comments about the lack of specificity as it seems to me there is quite a bit of that depending on the brand you assess. I would argue there might be too many tires on the scene. But, thanks for the comment.

  5. Boring and uninformative. I too would like to know why the L knobs are reversed on the SE5. Most tires have L or asymmetric side knobs pointing toward the centerline and front of the bike on the top of the tire – Morsa, Goma, DHF, XR4, Citius, etc… The one time the design was reversed with Schwalbes Pre 2015 Nobby Nic, it was terrible. I reversed the NN and it cornered much better.

    • I’ve asked many of these types of questions and the common answer may not satisfy you. In some cases, maybe most, the placement of knobs is not generated by a computer design, or fancy algorythym, but by the experience of the designer. In a couple weeks I have an interview with Tom Ritchey and he says his tread blocks were largley shaped years ago and now that family of knobs is modified slighly based on the intended purpose. Even with that, the orientation is influenced by his experience as to what works, and what doesn’t. That too was echoed by WTB, Schwalbe, Conti and others. It’s not a satisfying answer, but I bet they positioned your L know such because they assessed the edge orientation and assumed it would either aid cornering or braking, or both. Not to say it is just an educated guess, but, that’s somewhat what it is. Sorry I couldn’t get a better answer for you. I too expected something more meaty.

  6. Thank you for the reply, Christophe. What would be helpful is if these companies described what terrain they were riding and what performance criteria they used when they settled on their design. For instance, Schwalbe seems to be made for soft terrain exclusively and limestone and granite sand them down in only a few hours. But no one new to buying tires would know that. They would just spend a lot of money and then be on the market again for a replacement in 30 days.

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