The long road to dual-purpose knobbies

When Ted King recently won the Epic 150 gravel race in Missouri on our Rene Herse Steilacoom tires, many were surprised that he ran knobbies on a fast course. But there were a few muddy corners where the knobs would provide valuable grip, and Ted knew that on the smooth portions of the course, he wouldn’t give up performance, thanks to our innovative tread pattern.

When we developed our ‘dual-purpose’ knobbies, I wanted tires that roll and corner as well on pavement as they grip in mud. I can see you shaking your head: “Impossible!” For grip in mud, you need knobs. On pavement, knobs flex as the tire rolls, consuming energy and slowing the bike. And when leaning the bike into a paved turn, knobs squirm, which reduces grip and makes cornering unpredictable.

That is why for most of the history of cycling, there were knobby tires for cyclocross, and smooth tires for the road. Nobody thought of riding knobbies on the road…

When mountain bikes became popular in the 1980s, knobby tires were part of their rugged appeal, but most entry-level mtbs were ridden around town. Tire makers started to think about making knobbies that perform better on pavement. The solution was obvious: Make them less ‘knobby’ by spacing the knobs more closely. In the center of the tire, the knobs often were linked to form a continuous ‘center ridge.’ This distributed the rider’s weight over more knobs and reduced the squirm. On pavement, this worked to a degree – these tires squirmed less, but they were still no high-performance tires.

There was a drawback: When you really need knobs to dig into soft soil, mud or snow, the closely spaced knobs clog up. You spin as you would on a slick tire. These days, you don’t find many tires with center ridges and densely spaced knobs any longer, because they are worse than road tires on pavement, and just as bad in mud.

The next idea was to remove the knobs in the center of the tread. That way, you roll mostly on smooth rubber when going straight, which reduces the tire’s resistance. As long as you go straight, this works OK. When you corner on pavement, the tire grips fine at first. Then you climb onto the knobs and suddenly lose traction. It’s not exactly what you want from a high-performance tire…

If these tires had excellent performance in mud, it might be worth the trade-off. But when grip is reduced,  you can’t lean the bike far enough to use the corner knobs. Even if the tire sinks deep into the mud, there are too few knobs to really make a difference – you don’t get much extra traction. Once more, you end up with a tire that corners like a knobby on pavement, but slides like a slick tire in mud.

How can you get around this problem? On the face of it, the answer is simple: Make the knobs large enough that they don’t squirm, yet space them far enough that the mud clears from in between. The knob shape itself doesn’t make much of a difference – the engineers of several tire makers have acknowledged privately that the different knob shapes are “mostly for style.”

Coming up with the idea was easy, but the devil is always in the details. Can a knob be large enough not to squirm, yet small enough to dig into the mud? Our testing indicated that this was possible. How much open space do you need to clear mud? Fortunately, decades of racing cyclocross on various tires had given us a good idea of where to start with our testing.

How to make a knobby tire that corners predictably? You arrange the knobs so that there always is the same amount of rubber on the road, no matter how hard you lean the bike. That way, the traction is always the same, rather than suddenly breaking away as you lean and get on the edge of a line of knobs. It’s logical, and yet I haven’t seen any other knobby tire that follows that principle.

The hardest part was combining all these parameters into a single tread pattern. It took a lot of experimentation, but the result has surprised everybody. On a fast paved group ride, these tires perform as well as many racing tires. I know this sounds like hyperbole, but riders who’ve tried these tires agree. Gravel racer Ted King wrote to us: “On pavement, they’re incredibly smooth. The tread pattern is awesome  it’s really cool how deceptively simple the Steilacoom tread is, yet how well the tires work.” On independent reviewer even set Strava KOMs on his Steilacooms.

The cornering is easier to show. I can’t think of any other knobby tire that I’d dare to lean over that far on pavement. And I wasn’t even pushing the limits…

How about the performance in mud? After three seasons of cyclocross on Steilacooms, everybody agrees: They grip as well as the best cyclocross tires developed specifically for muddy courses.

Surely, there must be some drawbacks – otherwise, we should all be riding these knobbies all the time!

On the straights, the knobs have less ‘pneumatic trail,’ because there isn’t a continuous surface of rubber on the road. That means they don’t have quite the same straight-line stability as smooth-treaded tires in the same width. You may not even notice this, because the effect is small.

The knobs add a little weight, too, but once again, the effect is really small, because the tread between the knobs is thinner – that part of the tire doesn’t wear, so we don’t need extra rubber there. Our knobbies weigh between 45 and 60 g more than their smooth-treaded cousins in the Rene Herse tire program. Thanks to our lightweight casings, they’re still lighter than almost any other tire with the same width.

As to the rolling resistance, the difference is so small that you won’t notice on the road even on a spirited ride with a group of well-matched friends. That said, like Ted King at the Epic 150, you’ll have people wonder why you ride “so much tire” on rides that include significant pavement…

I’m excited about the Rene Herse dual-purpose knobbies, because they make rides possible that were difficult to imagine before: rides that combine paved roads with muddy trails and even snow. We no longer have to choose between on-road performance and off-pavement grip. Once again, we’re pushing the limits of what our all-road bikes can do.

Our dual-purpose knobbies are available in three models:

  • 700C x 38 mm Steilacoom
  • 650B x 42 mm Pumpkin Ridge
  • 650B x 48 mm Juniper Ridge

Click here for more information about Rene Herse tires.

Photo credit: Dustin Michelson (Photo 1).

About Jan Heine

Spirited rides that zig-zag across mountain ranges. Bicycle Quarterly magazine and its sister company, Rene Herse Cycles, that turns our research into the high-performance components we need for our adventures.
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46 Responses to The long road to dual-purpose knobbies

  1. Gary A Cziko says:

    What model Cannondale does Ted King have in the photo. And did he run his Steilacoom tires tubed or tubeless in the Epic 150 race?

    • Jan Heine says:

      Ted Cannondale is a Super X, I believe. He did run his Steilacooms tubeless. When riding on gravel in a paceline, you can’t see where you are going, and you’ll hit some big rocks. To avoid pinch flats, you either run really wide tires (which the Super X doesn’t fit), or you run your tires tubeless.

  2. SteveP says:

    knobby Snoqualmie please!

    • Jan Heine says:

      We’ve been thinking about a 700C x 44 mm knobby. Many current gravel bikes have clearance for 44 mm tires, and the extra width translates into 34% more air volume, which makes quite a difference on rough surfaces.

      • jambee says:

        Yes!!!

        Two sizes are needed:
        1. 650B x 2.2 inches. This is a market that requires such an option.
        2. 700x 44mm.

    • Karl says:

      I really would like to find a 700c Steilacoom in a 28c or 30-32c width. I ride all kinds of road surfaces on conventional steel road bikes and have been doing so for about 40 years. My 1981 custom Mercian (69cm) has room for up to 32c— there is no way I can get the 38c Steilacoom tire into that frame. More’s the pity because I will never succumb to the gravel bike mania, but I really would be very well served by a Steilacoom tire. But I know that I represent a probable minority of one (Jobst Brandt, were he still with us, might have made us two— or not?).

    • Matt S. says:

      Yes please! A 700 x 44 or 48 would be very welcome indeed! I currently run some Kendas with a very similar tread pattern in 29 x 1.9 that are wonderful in the dirt, but are slow on the pavement due to their weight and stiffness. I would absolutely buy and ride the crap out of a Rene Herse knobby in a larger 700c size. 38mm is just not enough for the trails where I live.

    • BigSchill says:

      I’ll 2nd that… 700 x 44 would be perfect.

  3. jimmy says:

    any plans for a 26″ version?

    • Conrad says:

      Lots of people, myself included, really want a rat trap with those treads. Please make it the next tire in the lineup! They will sell out in a day!

      • Daniel M says:

        I would pre-order, crowdfund, whatever, to get a pair of 26″ knobbies with the RTP casing. Find a lighweight, full-rigid mountain bike from the 80’s or 90’s, convert to drop bars and add these tires, and you have a bike that is way more capable off-road than most cyclocross bikes and can cover more ground in a day, paved or unpaved, than would be remotely comfortable on a modern mountain bike. Even as it is, the slick RTPs are astoundingly good off-pavement on both bikes I have them on.

        Meanwhile, the search for supple 26×3.0″ slicks for my desert touring tank goes on…

    • Conrad says:

      That’s what I do too. People practically give away 26 inch bikes. Find the right one, put some drop bars and good tires on and you have a truly awesome bike on the cheap

      • Pawl Bearer says:

        I am waiting patiently for the knobby Rat Trap Pass. Letting all the old knobby tires get worn to bald and not worrying about finding replacements. Jan’s lack of comment on the 26″ knobby tire in the article and in the comments is hopefully an indication that the mold tooling has been designed and is already being built. The Firefly 26″ wheel Allroad from BQ#56, 58, 66, & 67 needs a pair of knobby tires!

      • Jan Heine says:

        We are definitely committed to 26″.

    • teamdarb says:

      I’d prefer to see a more touring specific RTP with maybe more tread thickness improving life span. Everyone focuses on the racing guys when it comes to this brand, despite it trying to separate from the term. I live on my bike and travel with 25-ish pounds give or take the consumable items. I have been through two sets in a short span. This whole wide tire spreads the load is bs…. The tire is wider so you wear out a wider area. The time frame is the same or faster depending on environmental factors and overall weight to pressure ratio. Give me double the center thickness Jan!

      • Jan Heine says:

        I am surprised by your comment. It’s simple physics: The same force is removing the rubber, so you remove the same amount of rubber. Whether you remove 1 mm over a 15 mm-wide band on a narrow tire or 0.5 mm over a 30 mm-wide band on a wider tire comes out to the same.

        If you are running very high pressures, you may wear only the very center of the tire – you want a Rene Herse tire to wear so that all the longitudinal lines disappear – see this post for more info.

      • teamdarb says:

        Jan, your response does not reflect my experience of these tires. I very familiar and receptive to advice about tire pressures when it it comes to 26″. I’m only 5’4″. Math and science is great as numbers don’t lie, but cannot be justified by heart and soul. Be a friend and make a touring specific tread mixture or add on more tread thickness for is “living the effin dream” in the real world, not just on instagram. Like the tandem rider comment, I cannot justify riding something less than. The continual roll down hills is unreal.

  4. mattmolitor says:

    Could you comment on running knobbies with full coverage fenders?

    • Jan Heine says:

      You need ample clearance. In photo 6 above, you see Ryan Francesconi running Juniper Ridges on his bike with fenders. He’s got thousands of miles on that setup, no problems. We recommend 20 mm clearance above the fenders with smooth tires, 25 or more with knobbies.

  5. Phillip Cowan says:

    How long before WTB copies these? (full snark intended)

    • Jan Heine says:

      I think it’s unfair to say that WTB copied our tires. They took our ideas and brought them down to an OEM price point, something that we aren’t equipped to do. When you can get a $ 1600 bike from the factory with tires that are at least decent, that is great for everybody. And when the OEM tires wear out, riders can always upgrade to a set of our Rene Herse tires.

  6. ascpgh says:

    What a great development process. As someone who repeatedly wiped out riding HardPack 2.2” in the Colorado San Juan’s, I appreciate your recognition and elimination of higher shoulder knobs making a flat contact patch with deeper tread. What’s cosmetic sellout and total compromise.

  7. Hi, I just put antelope hills on my new salsa timber jack ti build. It’s a brevet style bike with aeros. Would the knobbed tyres be beneficial and would you look at making them in that sort of size? Thanks, Stephen.

    • Jan Heine says:

      The knobbies help in mud, snow and other surfaces where the tire makes an imprint. On loose ground like gravel, it’s the rocks sliding on each other, rather than the tire sliding on the top rock layer, that causes slip, so knobs make no difference.

      • Come to New Zealand….I’ll give you rides with all those in one day! And you dodged the real question beautifully…Lol.

      • Jan Heine says:

        I’d love to try some of your routes! Regarding a dual-purpose knobby in a wide 700C size, we’re considering it. There are many tires we’d like to make, but the R&D is quite involved. With the dual-purpose knobbies, it’s not a simple matter of scaling up the tread pattern, because the knobs can’t get bigger, otherwise, they no longer dig into the mud, and the spaces in between the knobs also are optimized so they don’t clog up with mud, but still put as much rubber as possible on the road. That makes each dual-purpose knobby a completely new tire that requires quite a bit of development.

      • Thanks Jan, I will wait patiently. Check the Tour Aotearoa Brevet ride out. Did it 2016(got injured) and 2018(all good). Seriously, if you ever come out this way get in touch. timings@xtra.co.nz

      • mtbvfr says:

        Hi Jan,

        What type of tread pattern would you recommend for loose ground like gravel?

        Thanks, MTB.

      • Jan Heine says:

        For loose ground, tread pattern is not important. The rocks slide on top of each other, not the tire on the top layer of rocks. That is why for loose gravel, we use our all-road tires with very little tread. Knobby patterns work when the tire leaves an imprint in the ground – on soft soil, mud, snow, etc.

  8. CLuecker says:

    Is RH planning a 26” version? I perceive there’d be a good market. Might have kept our tandem upright on a muddy farm track two weeks ago. The RTPs were just a bit slippy…. Just can’t bring myself to downgrade.

  9. Ronan Bossard says:

    How long does the knobbies last on pavement compared to one of your slick tire? I am guessing “a lot less”, but I’d like to have an idea if it is ten times less or just a third less.

    • Jan Heine says:

      They don’t last quite as long, because there is less rubber on the road, but reports from people who have been riding their Steilacooms mostly on pavement report that they get at least 4000 km (2500 miles) out of them – not bad for a 38 mm tire. The wider versions obviously will last longer. So your second guess of about 70% of the lifespan of our smooth tires seems about right.

      • Ronan Bossard says:

        So those tires can be interesting for a days or weeks long trip where the road surface and conditions are unknown and the total cost make the high cost of the tires easier to hide.

      • Jan Heine says:

        Wide tires spread the wear over so much rubber that they last a long time, and the cost-per-mile is much lower than with narrower tires. When I was racing on 19 mm tires, I rarely got more than 1000 km (600 miles) out of a set of tires. Now my tires last at least 6x as long…

  10. Jan, would you mind giving me a rough idea of tyre pressures for the Antelopes..I’ve put 20psi in but am not sure. I remember reading you saying higher pressures in the flexible sidewallls?? Thanks, Stephen.

    • Jan Heine says:

      I’d probably run 25 or 30 psi, unless you’re really light. You don’t want so much flex of the tire that the sidewalls start breaking down. However, pressure gauges can vary a lot – up to 25% in our experience. So your 20 psi might be 25 psi on my pressure gauge.

      In the end, the story with tire pressure is really simple: If it works (and doesn’t exceed the maximum pressure of tire or rim), it’s probably fine.

  11. dennischasseurdecols says:

    Completely off-topic, but with all the product suggestions; how about René Herse wool jerseys in the classic downtube script? Exposure for the iconic name, and a tribute to The Man.

  12. Peter Tuft says:

    Yesterday I had a mud experience which makes me question the value of knobs at all. I ride a Cannondale Slate with 42 mm slick tyres but have little experience in mud or very rough conditions. Over 12 km of sticky mud (after 20 mm rain in near-outback South Australia) I found myself doing better than many other riders on standard mountain bikes. When the rain started I was very concerned about my slick tyres, but I had adequate traction and breaking (no heavy breaking or fast turns though), and apparently less mud build-up than others. Knobs offered no advantage in deep sticky mud. Why bother?

    • Jan Heine says:

      Really sticky mud clogs up any tires, even the FMB Super Muds on my ‘cross bike. (The old Alan doesn’t have clearance for our Steilacooms.) On in-between surfaces, where you make clear imprints into the substrate, knobs do make a huge difference.

  13. mike says:

    Love the Juniper.
    I don’t agree, that they are as fast as your slicks on pavement, but the impressive grip in the wild is worth to take the small drawback. It’s fast or faster than a Conti RaceKing with the grip of a much more aggressive tire and a lovely behavior in all situations. A real Allroad-Allsaison-Tire!

    Even you state, that knobbies do not help on loose ground, I feel much more confident in curves on gravel and in the wood. Your slicks are smoother, your knobbies are more versatile (and still fast).

    Thanks for making that wonderful tire,
    mike

    • Jan Heine says:

      Confidence in your tire, whether it’s in its grip or in its speed, is based on more than pure physics. For many riders, knowing that the knobs are there gives them more confidence on gravel, and conversely, makes them feel slower on pavement. As you say, it doesn’t really matter, as long as we enjoy our tires.

      I definitively agree with you, our road tires (they aren’t really slicks) are smoother – we haven’t found a way to get rid of the buzz of the knobs. You’d think that generating that noise must take energy, but making noise doesn’t take much. Just think of a squeak on your bike – super-annoying, but it doesn’t slow you down.

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