DIRT ISSUE 125 – JULY 2012

Words by Ed H. Photo by Steve Jones

When Bos recently released their air sprung Void DH shock it’s fair to say that we were pretty surprised. The reason being that Bos have always been a company with a focus purely on performance, even if it comes with a weight penalty. They have always made it clear that they’d never release an air sprung product for DH use unless they were able to make it match the performance of a coil spring. We thought that might never happen, but the Void marked that turning point, and now hot on its heels comes the new air sprung Idylle RaRe (Race Ready).

It’s interesting that Bos released the rear shock first. I say that because RockShox for example have been making air BoXXers for years, but it took them much longer to produce the Vivid Air due to the different challenges that a rear shock throws up. When I asked Arnaud Jacob (the designer of both these new Bos products) why they’d produced the rear shock first he basically said it was because they found it easier. Part of this is due to the size and different leverage ratios involved, but it also seems like their vast experience in dealing with internal temperature fluctuations in events like the Paris Dakar Rally (Bos also manufacture suspension for rally cars) made things easier for them.

Anyway, enough about the rear, we’re really here to talk about the forks, which apparently have come about quicker than even Bos themselves imagined. They had been working on them for a while and had got to the stage where they were ready to give their sponsored riders prototypes, and basically the feedback was so good that Bos quickly realised that they were much closer to production than they thought they might be. The only real change that the riders requested was for the reintroduction of the hydraulic bump stop. In the Void shock they have managed to do away with this, saving weight without compromising performance, and they thought they might be able to do the same with the fork, but it turns out that they have managed to make the air spring in the fork so linear that they can no longer rely on the usual ramping–up at the end of the travel to cope with bottoming out.

Once this hydraulic bump stop was put back in the feedback from the riders wasn’t that this fork just matched the performance of the coil version, it was that it was even better. The most noticeable improvement was increased sensitivity in the early part of the travel. The reason for this is that the self–adjusting negative pressure means that you always have zero preload at the start of the travel, no matter how hard you run the forks. This is something that is rarely achieved with a coil spring set–up. Put this increased performance together with a weight saving of over 300g and it was clear to Bos that they had hit the nail on the head and it was time to start offering this fork to consumers.

With rebound and high and low speed compression adjustments damping remains the same as the previous coil version, as does the price. Obviously this is still a hell of a lot of money for a fork, but the good news is that it seems that it might not be too long before the standard Idylle gets an air spring. Bos genuinely seem to feel that they have more than matched the performance of a coil spring with these air products, and because of that Arnaud certainly didn’t think it would be unfeasible that in the not too distant future we might not see any coil spring products from Bos.

We’ll have a full test on these forks in a future issue, but in the mean time I can tell you that Dirt’s Steve Jones has just got back from preliminary testing in France and Italy where he was very impressed by them, and when Nico Vouilloz got to try them he had to ask “Are they really air?”. Also, if you search for ‘Bos’ on the Dirt website you’ll find a full interview with Arnaud about both these forks and the Void.

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