Less is more: why the 27.5 Plus standard is doomed

http://ad.doubleclick.net/N4817/ad/Sport_BikeRadar/rss;sz=300x250;ord=1478727902

If there’s one thing that’s certain in the world of mountain biking it’s change. In particular, there has been a proliferation of standards to do with wheel size and most recently, tyre size.

• Are 27.5+ bikes faster than 29ers?
• Exploring 27.5+ video

Plus tyres have been the latest introduction. They use a mid-sized 650b diameter rim that’s around 35-50mm wide with a much higher volume tyre in the 2.8”–3.25” range. The promise is greater grip and comfort and we’ve proven them to be faster in back-to-back tests. It sounds like a done deal for the future of mountain biking — so why are there signs that the days of Plus sized tyres might well be limited?

Plus and minus

The big benefit of the Plus tyre is that it gives you more grip, as Jason Chamberlain from Specialized explains: “Wide tires provide unmatched traction with a negligible loss in rolling resistance. In many situations they climb better because they conform to the terrain more easily and don’t dissipate momentum trying to climb over every little bump and rock. Meanwhile on the descents, some have declared 3.0” tires to be the best suspension upgrade in 20 years.”

ADVERTISEMENT

Indeed, it was manufacturers trying to offer the soft terrain ‘float’ and grip of a fat bike’s huge rubber footprint in a more wieldy package that led to the category developing. Our testing has also shown a definite speed advantage over 29ers when it comes to roll-down tests as well as timed descents. However, it’s not as open and shut as that.

Even with standard casing tyres, the extra rolling weight can dull handling feel

The downside of a very big tyre is that there’s much more sidewall flex and squirm as well as undamped rebound, as Chamberlain details: “Some riders have discovered mild drawbacks to 3.0". One is that the sidewalls can squirm under hard cornering. Secondly, the sidewalls may not be as durable in some circumstances without adding additional weight. The 2.8" tires seem to be the sweet spot between lightweight, durable casing and sidewall support.”

Save for a short lived Plus specific fork from Fox, any bike using a Plus tyre uses a 29er suspension fork, which means longer, heavier and more flexible legs and a knock on effect in terms of the front end height

Minus Plus?

You can read more at BikeRadar.com

via BikeRadar All the latest from BikeRadar.com http://www.bikeradar.com/mtb/gear/article/why-the-275-plus-standard-is-doomed-48551/