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10 Aug 2010

Durano vs Kojak

My Sinner Mango Sport Red Edition, or 'Jenease' to keep it short, first had Durano tyres on the front. They're fast, quite reliable and offer plenty of grip in the dry. But they are only 28mm wide and at a pressure of 8 bar, they're not as comfortable as I'd like tyres to be. So I became interested in Kojaks. They have a maximum allowed pressure of 6.5 bar and are much bigger. The nice thing is that they only weigh a bit more than Durano's. There was however, on big downside, rolling resistance.

Various test had shown that Kojaks are a lot slower than the very racy Duranos. But I liked the idea of more rubber. Fatter tyres would make riding on rough roads a better experience. The thing is that most of the roll out tests I've seen are done on perfectly smooth surfaces. And our cycle paths may be very good, they're not perfectly smooth. Some asphalt has an open structure and on small rural roads the quality can be, 'just over acceptable'.

So I wanted to do my own testing. Now, we don't have any hills followed by a nice long flat piece of road around here. That means that I have no idea how to do a roll out test. You'd need a 300 metre stretch of road for that. We do have small tunnels. My idea was to roll down and measure how many seconds it takes to cover a certain distance. I used tar lines in the road surface as a mark. Problem is that my tests weren't any longer than 25 or so seconds. But the results did say something. Especially because I tested on smooth and rough asphalt.

First tyre tested was the Durano, at the pressure I use them on, not the highest possible (9.5 bar). There's not much weight on Jenease's wheels and I prefer to have grip. And the higher the pressure, the less grip you have.

Second tyre was a set of rubbed in Marathon plus. They came of David H.'s Mango and he was curious how they'd do in a test. I'd never use such heavy and difficult to mount tyres. But since he is a fellow velonaut, I included them in the test. I used the pressure he rides them on, 6 bar.

Third tyre was my desired Kojak, at 6.5 bar.

The table below explains most of the results. Kojaks will, according to my test, make Jenease roll 0,7% slower on smooth asphalt. During the tests I didn't go much faster than 13kph or so. The total weight of Jenease and I was about 91kg.

Interesting to see is that on rough roads, the racy Durano increases it's lead over the other two tyres. In the end, I did stick with the Kojaks. Simply because they ride better. I did 90km on them last Sunday, and they do indeed feel a little bit slower.

Was this a very good test? No. It needed longer rolling. That would make the times less of an error factor. But the result, especially the difference the road surface makes, is interesting.

3 comments:

  1. And... look how fast those Marathon+ tyres are. In your test they are at worst just 2% slower.

    I avoided them for years on the grounds that they had an appearance which made me think they'd be like cycling with wellies on, but they're not really that bad in reality.

    If you want to do it again with a hill, I have thought of a "hill" you can use locally. You then just need some chalk to make marks so it can be done repeatedly.

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  2. @David Hembrow:
    I wonder what happens if one uses Marathon at the highest air pressure.

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  3. zet je het ook op de lml ?

    gr

    Wim

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