In case you haven't heard, apparently 26" is dead, 27.5" is sweet but 29" is really fast and the 'mullet' 27.5" and 29" combo could be faster in the right conditions but we're not sure yet. Wait... what? After many years of 26" being the wheel size for mountain bikes things have had a serious shake up over the past few years.
From 26" we made the jump all the way up to 29"! These big wheels were great for XC riding but for DH's it seemed a little extreme, many manufacturers and riders went to 27.5". But, with advancements in geometry and a better understanding of the 29" wheels DH and other gravity related disciplines have now adopted the 29" wheels. The benefit now maximised with their modern geometry to suit. Then, quietly along came the 'mixed wheel' mullet option. 27.5" rear and 29" front but... why?
Mixed Wheel MTB Benefits
So why are manufacturers experimenting with mixed wheel designs for their race teams and others even making production mixed wheel models? The theory is that a 29" wheel up front being bigger will roll over rough terrain with greater ease and hold momentum more efficiently. When turning the bike having that bigger front wheel means there is actually more tyre touching the ground, providing increased grip and control. On the rear that smaller wheel will be nimble and light to ride, turning should be snappy and ultimately very fast. Changing lines or picking up the back of the bike to get over obstacles will also be easier with the smaller rear end.
Mixed Wheel Challenges
The grass always looks greener on the other side but, are there aspects you should consider before jumping onto a mixed wheel size? For sure, there is always a bit of give and take. Just like the fact that the big 29" front wheel rolls over rough terrain easier the smaller rear is going to find this more difficult. The good news is that since your front is already over the obstacle you've already got that forward momentum to carry you through. However, it's still going to be a little rougher than a full 29" setup. You're also going to loose out a little on the rolling efficiency that comes with a full 29" bike.
Current Mullet Bikes
So who's made the jump already? The famous Santacruz Syndicate DH race team tested a mullet V10 and the bike rapidly made it's way into production which is a great sign! Forbidden Bike Co. also released the 'Ziggy Link' which enables riders to convert their 29" Druid or Dreadnought into a mixed wheel beast! Instead of being subject to the geometry sacrifices of just throwing a different size wheel in there the 'Ziggy Link' accounts for the smaller rear wheel and makes sure the benefit of the mixed wheel setup is maximised with the geometry to suit.
Will The Mullet MTB Take Over?
29" took a long time to catch on as bike companies had to make significant adjustments to their understanding of geometry etc. to get the feeling right. Companies have learned from this and as a result are already making some seriously dialled mixed wheel bikes already. But... the current generation of 29" bikes are the best we've seen to date and have some serious appeal with their handling and speed for the mixed wheel to match, a big ask. Ultimately, time will tell but we predict you'll be seeing a few more mullet bikes in the next few years!