Is Plus more?

Plus bike tyres are more grippy, more comfortable, but have more drag too… so should you get 27.5in Plus or 29in bike?

What is it with the bike industry? No sooner have they introduced one new wheel size, they have to go ahead and put together a Plus version of it. We reckon innovation is a good thing, but it sure makes it tough for us to pick which wheeled bandwagon is going to stick, and which isn’t.

Should you buy a Plus bike? What about bikes that can use both 27.5in Plus and 29er wheels, like the Orbea Occam and Whyte S-150?

Here’s what we know about Plus tyres, to help you decide.

The basics

Bear with us here if you know this already: you can get Plus versions of 29in or 27.5in (or even 26in) tyres, they have the same internal diameter but they’re wider.

How much wider? 2.7-3.0in about covers it.

They usually sit on wider rims too, 40-50mm internal width to allow the wider tyre to spread out properly and form the optimal shape. Those 27.5in Plus tyres near enough match up in external diameter to 29in tyres, which means some bike companies let you switch between the two wheel sizes.

The data

Schwalbe says a 2.8in Nobby Nic has a contact patch that’s 21 per cent bigger than the traditional 2.35in version. (1.7bar at 2.35in, 1.0 bar with 2.8in). That gives “significantly better traction” they say.

There’s also a 5.2watt rolling resistance increase per tyre but we don’t really need to worry about that because you’re not going fast enough on a mountain bike for that to be anything more than negligible.

What is significant is the 134g weight penalty per tyre that we’ve measured, which will slow you down and affect your suspension, particularly as it’s part of the unsprung mass, the wheels.

WTB agrees that Plus tyres increase traction through a larger contact patch, but they’ve got no data. What they do know is that Plus tyres let you run lower tyre pressures because there’s more volume in the tyre to provide support and stop you dinging your rims or the tyre rolling around too much.

Lower pressures are a good thing because they increase the compliance of a tyre — it deforms round roots and rocks and gives you grip, where a smaller harder tyre would bounce you off.

mbr’s take

Early Plus tyres proved to have incredible grip levels in the dry and unmatched comfort on rocky fast terrain, but they skated around on proper mud and the sidewalls were flimsy and puncture prone.

Now the next generation of tyres has arrived — like the 2.8in High Roller II from Maxxis, the 2.8in Nobby Nic from Schwalbe and the 3.0in Trail Boss from WTB — with improved grip, but the sidewalls remain just as fragile.

So 27.5 Plus or 29er?

As with so many aspects of mountain biking, it depends where you ride — if rocky, fast or trail centre trails are your stomping ground then Plus could be more. Muddy, picky and slippery? 29er would be our choice.