Gravel Cyclist's Tire Dilemma: Knobbies or Slicks? 7/8
Read this, if you are a critical thinking gravel or allroad cyclist
In my opinion, tire's puncture resistance is one of the most important tire's characteristics. Why? Simply because cycling is the one and only activity the cycling tire was made for, and once a tire is flat, cycling is near to impossible.
During my gravel rides I suffered from all three puncture types generally known in cycling:
1 Tread cuts which are caused by penetration of sharp objects (sharp stones, sharp metal, or glass) through a tire tread (and an inner tube, in case of a non-tubeless system),
2 Sidewall cuts which occure when a sharp object (stone) tears tire's sidewall (and punctures an inner tube, in case of a non-tubeless system),
3 Pinch cuts or »snakebites« which occure when an inner tube gets pinched in between a tire and a rim. This happens when a rim bottoms out on bumpy surface such as chunky gravel road. Needless to say, a tubeless tire can not pinch flat, since it has no inner tube to get pinched.
Good puncture resistance keeps a smile on your face.
Now, how does tire tread influence tire's puncture resistance? It is my impression that many cyclists associate knobbies with better puncture resistance, and slicks with poorer puncture resistance. However, a look at the three puncture types shows that knobby tire tread can eventually only be beneficial to avoid the first puncture type (tread cuts), while being absolutely powerless against the other two (sidewall cuts and pinch flats). This often is forgotten when addressing knobbies' puncture resistance.
Thus, as far as the tire tread ALONE is concerned, knobbies' advantage over slicks is obvious. Knobbs make tire tread thicker, thus making it difficult for sharp objects to penetrate through the tire. Grooves in between knobbs, on the other hand, expose thiner tread which is just as puncture prone as that of slicks.
But even this very limited knobbies' advantage over slicks is further diminished in practice. Namely, many tire producers use solutions which considerably improve puncture protection (of slicks). The most well known solutions are (1) bead-to-bead kevlar breaker, (2) puncture protection belt placed only under tire's tread, and (3) super-thin extra strong casing used in modern tubeless tires.
Thus, to provide maximal puncture protection for slicks, one should look for all three solutions in one tire at the same time. An example of this is the tubeless Maxxis Re-Fuse. I put continuous and serious efforts into trying to puncture this sturdy tire. However, the tire didn't just persistently re-fuse to get punctured, it absolutely loved my fierce abuse. I believe this tire is more puncture resistant than a majority of knobby tires on the market.
The Maxxis Re-Fuse is ready to abuse. This 40 mm tire not only is unpuncturable in practice, but after 3.500 km of gravel abuse, the front wheel tire's semi slick pattern is almost like new.
Unfortunatelly, using all three puncture protection solutions in one tire affects its riding feel and increases its rolling resistance beyond what one might find acceptable. I found that for a tubed tire, a brilliant compromise between rolling resistance and puncture protection is a light kevlar puncture protection belt only placed under tire's tread, and a latex inner tube. It just seemed impossible to pinch flat with a latex inner tube. This combination proved to be unpuncturable in practice while still offering a very good rolling (Vittoria Voyager Hyper, 8.000 km without a single puncture).
The brilliant compromise between puncture and rolling resistance: slicks Vittoria Voyager Hyper, 40 mm, ran with latex inner tubes. Unfortunately, the tires are not produced any more.
On the other hand, using even thiner, very supple, super fast slicks (Compass Snoqualmie Pass) with ordinary (butyl) inner tubes resulted in catastrophic 8 punctures (5 pinch cuts aka snakebites, 2 tread cuts due to pieces of glass, and 1 not very bad sidewall cut) in just 2000 km of gravel cycling. Based on my very positive experience with latex inner tubes in Hypers, I assume Snoqualmies would have performed less disastrous with latex inner tubes. The reason I didn't run Snoqualmies with latex inner tubes was a banal one. At that time, wide latex inner tubes run out of stock in all European webshops. After 8 punctures in less than 2 months, my disappointment in Snoqualmies was so deep that they simply didn't seem worth a try with latex inner tubes, or even with tubeless setup which they also were supposed to had been designed for.
The Snoqualmies' aesthetic appeal and riding suppleness are top class. Their puncture resistance, on the other hand, could hardly be worse, at least in my case.
To sum up, knobbies' advantage over slicks in puncture resistance is smaller as it is generally believed. With proper puncture protection system (tubeless setup, puncture protection belt, latex inner tube), slicks' puncture protection can be on pair with, if not better than, that of knobbies'.
THE END OF PART 7/8
Credibility of the Article
The author of the article is Matej Goršič [Matey Gorshich], 41, male, PhD, who has been an active sportive cyclist for 28 years. In his youth, he trained, and competed in, road cycling and athletics. Once finally out of the competitive waters, he started consciously re-defining his understanding and practice of cycling. Today, he feels most at home in a creative mixture of non-competitive, electronic-devices-free, self-exploring, adventurous allroad cycling. During last 3 years, he spent over 25.000 km mostly on tiny gravel roads of South Estonia.
The tires tested for the article were bought by its author at normal market prices from different cycling shops in Europe. There have been no sponsors or donations for writing the article nor for mentioning brands and items in the article and showing them in its photos.