ANATOLY IVANOV / PROSE / 2012-04-11

16 INCH SLICK TIRES: SCHWALBE KOJAK REVIEW (STELVIO REPLACEMENT)

by Anatoly IVANOV

CYCLING / TRANSPORTATION / TRAVEL / REVIEWS

Do you like compact, 16-inch folding bikes? A Brompton? A Tikit? Maybe a bent? Great!

Do you like speed? Overtaking busses and cars? Riding above the speed limit? Then you’d probably choose a slick tire, the king of the asphalt: nothing rolls as fast.

But the 16-inch size is a problem: try finding a slick this small! For years, Schwalbe has been making the racing Stelvio in all sizes imaginable, including the Brompton’s and Tikit’s ETRTO 349. And now, the Stelvio’s dead. Discontinued.

KOJAK: THE STELVIO REPLACEMENT

For 2009, Schwalbe has improved the Stelvio’s rubber compound (better grip and durability), redesigned the side micro-tread pattern and renamed the essentially new product “Durano”. But, while it does come in quite a few unconventional sizes, the 16 inch is not one of them. To compensate, the fatter Kojak slicks introduced in 2007 were downsized to include an ETRTO 349 version in 2009.

 

Photo: Schwalbe Kojak on a Brompton front 16 inch wheel

I’ve been riding the Stelvios of various sizes for years. The Stelvios have been the default tires on my Brompton. How does this Kojak compare to the old faithful?

FEATURES

// Shape

// Pressures

// Surface

The Kojak is a completely bald, pure slick. The Stelvio featured a micro-tread pattern on the sides, mainly to indicate the location of the softer, grippier rubber band optimized for cornering.

// Rubber compound

The Kojak uses a vastly improved rubber compound for better grip, especially on wet surfaces.

// Puncture protection

Both the Kojak and the Stelvio use a nylon fabric protection belt called RaceGuard. Although not as puncture-proof as a Kevlar tape or a layer of densely woven Vectran, RaceGuard is still better than no protection at all. And it adds little weight and rolling resistance to the tire.

// Manufacturer weights

// My measured weights

Measured on electronic scales with 1 gram precision. Average of 2 tires per model.

PERFORMANCE IN THE REAL WORLD

I’ve changed the Stelvios on my Brompton to the Kojaks in November 2008 and have ridden about 700 km (435 mi) in different weather and road conditions (see below for details).

// Pressures

I weigh 65 kg (143 lb) on average (clothing and helmet included), but often carry stuff in my backpack, sometimes over 10 kg (22 lb).

// Ride and handling

The Kojak is fast, smooth and silent. Accelerating from 0 km/h to 35 km/h (22 mi/h) in seconds? No problem. Riding downhill at 55 km/h (34 mi/h)? Every day.

However, something is lost… barely noticeable. At times, the Stelvios were giving those magical sensations, especially on smooth, dry asphalt – it felt just so buttery smooth and… well, super racy, crazy fast. Again, a very subtle difference, but it’s there. I’d say a -5% decrease in speed on the Kojaks. But my bike computer can’t tell the difference.

Also, cornering on Kojaks is not exactly as good as on Stelvios. Steering feels a bit bizarre, as if the Kojaks deform / shift horizontally just a little bit. The Stelvios cornered as if on rails. The Kojaks ask for less lean and more prudence.

But the Kojak is way, way more stable overall. More cushioning, less jitter. Riding on the 16" Stelvios on the Brompton was super-reactive but sometimes erratic. The Kojaks just ride straight. Well, in a Brompton sense, that is…

// Grip

The Stelvios would glue to new, clean Swiss asphalt. Amazing feeling.

But add some sand… or, worse, some rain and riding the Stelvios becomes a skating game.

The Kojak grips the wet asphalt as if it was dry, incomparable to the Stelvio. The Kojak stays on the road under pouring rain: hit the brakes and the bike stops.

The Stelvios were simply scary in the rain. The rear wheel would just skid and I had to use the front brake almost exclusively. 2 of my serious crashes on the Brompton – one involving a bus, and another a car – happened on rainy evenings riding the Stelvios. So, a huge improvement here.

The Kojak is a lot more versatile. It works on cobblestones, a frequent road “feature” in Paris. Oh so romantic… I’ve ridden the Kojaks at about 35 km/h (22 mi/h) on cobblestones, an impossible feat on the Stelvios.

Polished wet sandstone slabs? Yes, a wonderful surface material for Paris’ bike lanes. Stelvios: change route. Kojaks: ride on.

Moreover, the Kojak “works” a lot better with road-parallel irregularities, such as cracks, asphalt edges and so on. It has happened to me to sort of ease on these “features”, at 0° angle, at speed. Something that had sent me to the ground on Stelvios in the past: I do experiment to the limits.

// Puncture resistance

Amazing. I don’t know if it’s pure luck or if the wider road contact surface leads to lower point pressure… But I haven’t had a single puncture yet! 700 km (435 mi) and counting (and praying).

I stopped counting when I hit a 5 cm nail going downhill at 50 km/h on my Brompton on March 30, 2012! First puncture since November 5, 2008.

However, the front tire now has 7 small cuts, with the largest about 4 mm in length. The rear tire has 11 such cuts. Some of them are filled with a micro particle of gravel. Should I worry about sudden cabin decompression? From my 4 years of experience, the answer is no.

With the Stelvios… I too got the cuts. But I also got the punctures. Quite often. Lots of quality time dreaming of wheel quick releases, under rain, at night.

VERDICT

While the Kojak has lost just a tiny bit of something “racy” compared to the Stelvio, it’s a much, much more versatile slick tire for fast, urban and intercity asphalt use. Especially on a winter rainy day in Paris.

Get those slicks, they’re very good.

ALTERNATIVES

A narrow, high-pressure, 16-inch slick? Maybe a Primo Comet, but it’s 37 mm (1.46 in) wide, rated at 85 psi and has a micro-tread all over…

WHAT ABOUT THE FUTURE OF 16" SLICK TIRES?

The end of Stelvio has brought up uneasy feelings and reminded a few things:

Will Schwalbe continue to manufacture boutique tires for folding bikes and recumbents?

In part, it depends on the number of users of such bikes. If everything goes as planned with Peak Oil, Global Warming and Growth Economy Collapse, more people will ride bicycles. Maybe even folding bicycles: a smarter way to implement intermodal transportation, avoid bike theft and keep away from vandalism.

And in part, the people at Schwalbe themselves are the guarantee: bike tires products’ manager, Carsten ZAHN, rides a Bike Friday Pocket Llama with “enough clearance to test all our 20" tires”.

 

Photo: Schwalbe’s Carsten ZAHN on his Bike Friday Pocket Llama equipped with 20" knobbies

I guess as long as Schwalbe guys like Carsten ride a folder, we’ll continue to benefit from their unique products.

 

Photo: Schwalbe’s Carsten ZAHN’s Bike Friday Pocket Llama with 20" Schwalbe Marathon Supreme

REVIEW CONDITIONS

ACKNOWLEDGMENTS

Special thanks to Carsten ZAHN, Schwalbe Germany and Caroline VIVIER, Schwalbe France for their extensive help with this review.

CHANGE LOG

2012-04-11 Added a paragraph about my first puncture in March 2012 by a 5 cm nail.
2009-06-01 Improved the “FEATURES / Surface” paragraph after discussion with Sean LUKE (see coments).
2009-04-14 First publication.

11 COMMENTS

Sean Luke / 2009-04-15 07:00

1. Sheldon Brown was quite insistant that tread, and particularly microtread, was entirely cosmetic; and in no way did it contribute to better grip on a road. Quite to the contrary, tread lowered the total amount of rubber hitting the road and thus made the tire *less* grippy.

2. The Kojak has a slick competitor in 349: the Greenspeed Scorcher. Which is comfier? Which has lower rolling resistance?

3. Sad that the Kojak appears not to have reflective sidewalls.

ANATOLY IVANOV / 2009-04-16 17:14

Hi Sean,

Thanks for the comment.

1. Sheldon Brown was quite insistant that tread, and particularly microtread, was entirely cosmetic; and in no way did it contribute to better grip on a road. Quite to the contrary, tread lowered the total amount of rubber hitting the road and thus made the tire *less* grippy.

I agree with Sheldon. I do prefer slick, bald tires. Have been riding slicks (sometimes semi-slicks for off-asphalt) all my life, since childhood, with a few knobby exceptions.

Should I improve some parts of my article?

I thought I was clear I preferred the classic slick, when saying “Maybe a Primo Comet, but it’s 37 mm (1.46 in) wide, rated at 85 psi and has a micro-tread all over“.

The Stelvios were perfectly slick on the rolling side. The micro-tread, or, to be precise, not a micro-tread, but some kind of rectangular pattern, was on the sides, coming in contact with the road only when leaning the bike while cornering.

I’m unsure whether this pattern is purely cosmetic or not, all I can say is that it worked really great.

2. The Kojak has a slick competitor in 349: the Greenspeed Scorcher. Which is comfier? Which has lower rolling resistance?

I disagree. The Greenspeed Scorcher is 16 x 1.5 in / ETRTO 40-349, that is, it’s 40 mm wide! Which, at least on the Brompton, is starting to be a bit tight, clearance-wise. It’s even wider than the burly Schwalbe Marathon Plus. I’d say it’s more of a ballon-bike tire than a narrow-slick-racing tire. So I wasn’t thinking about testing it.

I can only guess that it works good for Greenspeed’s trikes, because they don’t lean when cornering. Nothing substantiated by my experience, though.

What do you think?

Sean Luke / 2009-05-19 06:24

Well, the reason I quoted Sheldon was when you said, “The Stelvio featured a micro-tread pattern on the sides for better grip when cornering.”. Sheldon would seem to argue that the micro-tread would have no effect on the grip.

As to “racing tires”: if we’re talking rolling resistance, I wonder if going narrower and higher pressure will really help or hurt. It appears that the Scorcher, while a good 40mm wide, also has quite low rolling resistance (see http://www.greenspeed.com.au/scorcher.html ). At 280 grams it’s obviously heavier than the Kojak, but…

My interest in the Scorcher is really because I’m looking for a comfier tire: but if it’s more efficient too, that sounds good to me.

ANATOLY IVANOV / 2009-05-30 02:23

Regarding micro-treads on slicks, Carsten ZAHN, tires product manager at Schwalbe Germany, says:

Microknobs: to be honest, the effect is rather small. The compound is far, far more important. That is also the reason that our top performance tires like Ultremo are pure slicks.

Sean, I guess I’ll rewrite that paragraph you were referring to (“The Stelvio featured a micro-tread pattern on the sides for better grip when cornering.”)

As your reaction confirms, the sentence is ambiguous and can be interpreted as undue emphasis on tire texture, while it’s the rubber that counts. Stelvio had 2 different rubber mixtures: a hard wearing compound at the center, a grippier silica mix at the sides.

As to “racing tires”: if we’re talking rolling resistance, I wonder if going narrower and higher pressure will really help or hurt. It appears that the Scorcher, while a good 40mm wide, also has quite low rolling resistance (see http://www.greenspeed.com.au/scorcher.html ).

I’m not talking exclusively rolling resistance. Yes, rolling resistance is an important factor, but another one is the size of the inflated tire. As I feel it, the lower the volume of the flexible tire, the more direct is the contact with the road. The rim moves less relative to the tire road contact area when cornering or accelerating. More precision and system feedback, but less shock absorption.

At 280 grams it’s obviously heavier than the Kojak, but… My interest in the Scorcher is really because I’m looking for a comfier tire: but if it’s more efficient too, that sounds good to me.

Ah! Well, if comfort is a priority, then I guess the Scorcher might be good.

Personally, I’m not looking for comfort. I mean, for me, a road / racing bike is pretty comfy these days, when built with a nice stiffness / resiliency ratio, fitted properly, including a corresponding saddle (Fizik Aliante Gamma / Vitesse for my sitbones).

So, I can’t share in-depth information on how comfortable a tire is. Kojak is more comfy than Stelvio, underinflated is comfier, but that’s about it. Just not something I’ve looked for and tested myself.

Andrew Page / 2010-04-06 19:14

Nice post / comparison.

Brompton are now supplying their own Schwalbe Kojak tyre – with a reflective sidewall for added visibility to cars.

- Andrew

ANATOLY IVANOV / 2010-05-04 16:17

Thanks Andrew! Yes, Schwalbe now adds reflective coating to the 32-349 ETRTO Kojak sidewalls. Exclusively for Brompton.

Troy / 2012-06-06 00:25

Thanks for a great review. My Hammerhead is getting scary in Melbourne winter on the Stelvios, and I was looking for a suitable replacement without losing to much ‘raciness’ – I will definitely order the Kojaks now.

Petia / 2012-07-19 09:05

Awesome review, gave me more confidence riding my bike with 20″ Kojaks in wet and sandy conditions :)

Lee / 2012-09-26 02:38

Hi everyone.

Great read.

I have one 16 Stelvio (Brand New) for sale if anyone wants. $20 and you pay for shipping.

Dan

budieryanto / 2013-02-20 13:34

kojak is amazing , with 100 psi rear and front and tried to rode with a bad condition surface that the result is zero defect, no puncture and very quite, fast and lighter.

Vincent / 2017-05-22 13:30

Packing one or two Kojaks with soft (kevlar) beads are a must when touring in areas where you aren’t likely to find a Brompton dealership in case you need a new tire.

For some reason, Kojaks in 349 with soft beads seem unavailable outside the UK/US.

http://brilliantbikes.co.uk/-brompton-tyres-and-tubes/233-schwalbe-kojak-32-349-brompton.html

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