Je reproduis ici une interview de JHK (Jeremy Horgan-Kobelski), un top rider professionnel de cross country roulant actuellement pour la marque Gary Fisher qui donne son avis sur l’utilisation d’un 29"er pour la pratique du XC de compétition à haut niveau (coupe du monde).

L’interview est en anglais, j’en ai fait un résumé en français en bas de page.

L’interview de JHK en Anglais

Will JHK Ride a Two Niner in 2006 ? 1/9/2006

Soon after I joined the Subaru-Gary Fisher team in 2005, I was asked, “Would you be interested in racing a Two Niner ?”

Throughout my career I’ve always been willing to experiment with any equipment technology that could potentially improve my racing. Ever since my junior days I’ve enjoyed trying different setups and dialing in my race bikes. Having never ridden a 29” wheel bike before, I admit that I was initially pretty skeptical of the whole concept. I had seen few Two Niners at races, and I couldn’t see how the increased wheel diameter could possibly offer any improvement over a 26” bike.

I agreed to give it a try though, and I got my first taste of the Two Niner when I started riding a Fisher Rig single speed during my rehabilitation from a bad crash I had at Sea Otter last year. I rode this bike a lot during my recovery and I loved the bike the moment I threw a leg over it.

The difference between riding a Two Niner and a 26” wheel bike over rough terrain is night and day. It’s not an exaggeration to say that in many situations a Two Niner hardtail smoothes the terrain as well as a properly set up full suspension bike. On top of that, the cornering traction is far better than a 26” wheeled bike. The contact patch between the tire and the ground is greatly increased with the larger diameter wheel and this theoretical difference is immediately noticeable riding.

Although my initial impression of the bike was great, it’s hard to compare the experience of a single speed to that of a top-end race bike. After my positive experience with the Rig, I looked forward to trying a Two Niner version of my racing hardtail.

I got such a bike halfway through the 2005 season and I’ve been doing my best to compare it objectively to my 26” racing machine. I’ve been doing some back-to-back testing with Travis Brown — both of us riding different diameter wheeled bikes — and the results have been surprising. There are many situations, especially twisty loose singletrack and rough pedaling sections (either flat or fast climbing) where the person on the 26” bike can barely keep up with whoever is riding the Two Niner. Interestingly, much of the time whoever is on the Two Niner feels like the bike is slower, but is actually schooling the person on the 26” bike. After half a year of riding the larger wheeled bikes, I’m definitely convinced of their merits.

However, after all that praise, it’s natural to wonder why there are virtually no Two Niners in the pro XC field. There are several reasons, and they are the ones that kept me from racing my Paragon at the big events in 2005. First, there is the perception I mentioned that the Two Niner sometimes feels slower even though you’re not working as hard as someone on a smaller wheel bike. This is something that can only be overcome by racing on it, to see if it really is faster at the absolute limit of hard effort. Overcoming that perception is nearly impossible to accomplish in training, since even the highest training intensities don’t compare with a long race effort.

Another issue is simply weight. With identical parts, other than the fork and wheelset, my race Two Niner is about 2 1/2 pounds heavier than my racing 26” hardtail. I don’t believe that weight is the only factor in a bike’s performance, but it does make a huge difference. Additionally, a big portion of that weight is in the wheels and tires, which is the absolute most important place not to be carrying around heavier equipment.

However, each of these problems are surmountable, and big strides are being made in overcoming them. The biggest reason that the parts for Two Niner are heavier is that it’s a new technology that is only just beginning to be embraced by the industry as a whole. It’s not impossible to develop light and reliable wheels, tires, and forks for a Two Niner. As more people recognize the benefits to riding the bigger wheel bikes, there will be a much better selection of top end components. Gary Fisher and Bontrager have made a big commitment to this segment, and it’s looking like there are some great innovations which I will hopefully be able to take advantage of in 2006.

About a month ago I got a very light set of Bontrager wheels and tires which is getting close to the weight of a good 26” set. We’re also working with SRAM/Rock Shox toward a lighter fork for racing on the Two Niner platform. A Two Niner may never be as light as a comparably equipped 26” bike, due simply to the larger amount of material in many of the parts. But if the weight penalty is small then it will be worth it for a pro XC racer to move to Two Niner on courses where big wheels offer a performance advantage.

Working with Gary Fisher on this project has been fun, and I’m really looking forward to continuing throughout 2006. I can see the potential for the bikes, and I’m excited to see what I can do on the race course on one. As I said before, there aren’t many Two Niners in the pro races yet, but I’ll jump in now with the prediction that this will change over the next year or two.

Speaking for myself, I’m sure that you’ll see me on one here and there in 2006.

JHK

Résumé en Français

JHK a toujours aimé essayer du nouveau matériel, mais était sceptique au sujet les 29"ers.

Il a essayé et pas mal roulé sur un Rig (singlespeed 29"er) pour se remettre en forme après une blessure.

Il a noté une grosse différence avec le 26, le 29"er est nettement plus confortable, presque comme s’il avait une suspension, et l’adhérence en virage est bien meilleure.

Aussi il a décidé d’essayer un vrai vélo de XC en 29"er pour faire une vraie comparaison.

Il a fait de nombreux tests a l’aide de Travis Brown en échangeant les vélos en 26" et 29", qui ont montré un avantage au 29, en particulier dans les singletracks virevoltants et techniques, et dans les passages défoncés (autant en monté qu’en descente). Par contre on a toujours l’impression d’être plus lent sur le 29"er.

Alors pourquoi ne voit-on pas de 29"er en coupe du monde ? Il pense que cela vient d’abord de la perception que le 29"er est plus lent, et que la seule solution serait de vraiment le tester lors d’un effort maximal, comme ceux que l’on ne rencontre qu’en ... compétition !

L’autre problème est la masse, car son 29"er équipé identiquement pèse 2,5 pounds (1,13kg) que son 26, ce qui est d’autant plus pénalisant que cette masse supplémentaire est logée dans les roues, là où elle a le plus d’influence sur l’inertie du vélo.

Néanmoins il pense que ces 2 problèmes sont surmontables, et qu’ils sont du à une technologie encore jeune.

I a reçu de Bontrager le mois dernier un jeu de roues dont la masse se rapproche très sensiblement de celui d’un jeu en 26, et travaille avec Rock Shox pour avoir une fourche plus légère. Si la masse supplémentaire du 29"er devient plus contenue par rapport à un 26, elle sera compensée par les autres qualités du vélo aux yeux d’un pilote de XC international.

Il finit en prédisant que l’on devrait voir un nombre grandissant de 29"er en XC cette année, et qu’il en essayera un sur certaines courses.