Burning Question: Why Have Some Pro Riders Downsized to a 27.5" Rear Wheel?

[weeksy]

Racers can be quick to set trends through the trialing of various components, geometries, and suspension settings, however, once they find a groove, changing their habits can be next to impossible. When 29" wheels first came along, there was some hesitancy from shorter riders, and rightfully so. Even though they are scientifically faster in theory, each rider has their own unique setup quirks which can feel unnatural to others, including wheel sizes.

Front wheels can articulate, but the rear cannot. Could the centripetal force of the larger rear wheel be too much for shorter riders to leverage quickly into a turn? Is this why the 27.5" rear wheel has regained a position on World Cup and EWS podiums? How does the plowability of the 29" front wheel count for all of that confidence to motor through the bomb holes? What makes more of difference for straight-line stability - big wheels or the distance between them? What about head angle?

The level of physics needed to unravel the movements on a bike is mind boggling. Before you throw a floating center of mass like a human pilot, you need to understand that they all handle the bike with their own style, too.

In-house Pinkbike statistician, Seb Stott, broke down the timed results and weighed in with his impressions on back to back runs using both rear wheel sizes. The take away: lots of data and no clear answer.

With looming pressure to deliver the best result, many racers under six foot simply dealt with a full 29" wheeled bike, but their hunger for minimizing seconds on the clock eventually got the better of them. That led to a wave of downhill and enduro athletes taking a step back to a 27.5" rear wheel, whether that was an equipment choice mandated by the team or their own decision.

One thing is for certain, when it comes to these two gravity fed disciplines, all of the top guns are opting for the larger front wheel diameter. As the interviewees will allude to, the ability that the 29" wheel has to silence rough terrain is unrivaled.

We caught up with a few riders that have recently reverted to, or are at the very least, toying with the smaller of the two wheel sizes.

The rest as they say, is in the article.

I did read it and think "ooooh maybe i should mullet the FuelEX" but then reading the results of tests on other articles, the 29/29 combo was faster anyway, only 1 time did the mullet win and it was by something like 0.2s....

But reading the article on Pinkbike it's more about the fact it 'feels' nicer/better rather than it actually being quicker.

I do have a rear in the Status that would go straight in though.

[Mr Moofo]

27.5 wheels are for short people and girls ….

[Horse]

Are all other aspects kept the same? In particular, is the rider sitting lower (to the road)? That will influence how quickly the bike & rider can change direction and braking (perhaps only slightly in both cases - I really have no idea but am just noting it).

[weeksy]

Are all other aspects kept the same? In particular, is the rider sitting lower (to the road)? That will influence how quickly the bike & rider can change direction and braking (perhaps only slightly in both cases - I really have no idea but am just noting it).

Bikes these days often come with 'flip-chips'

2022-03-01_04-42-19 by Steve Weeks, on Flickr

This means you can remove/negate the drop in the bottom bracket/geometry and for example, mullet (27.5) the rear wheel but use the flip-chip to offset the lowering of the bottom bracket and keep the geometry correct.

It's a good point though Horse... good thinking.

[irie]

Mulletting a bike will (among other things) change ...

- fork rake and trail
- wheelbase
- CoG
- rear wheel gyroscopic effect

... so performing tests while trying to change only one thing at a time is impossible. Even if a flip-chip/minolink is used this itself changes a lot more than only rear height.

[Mr Moofo]

Mulletting a bike will (among other things) change ...

- fork rake and trail
- wheelbase
- CoG
- rear wheel gyroscopic effect

... so performing tests while trying to change only one thing at a time is impossible. Even if a flip-chip/minolink is used this itself changes a lot more than only rear height.

I run my Bfe 29er as a mullet - because I only had a free 27.5 wheel - it is run with a 2.6 tyre on it so it is not extreme . I have only ever run it as a mullet - but my rebuilt 29 rear wheel arrives next week - so I will let you know what rides better.
I tried mullet in my FlareMax and hated it - mainly because the BB height / pedal strikes became obvious.