The idea of mixing wheel sizes is not new in mountain biking, and beyond a few unicorn bikes, there is a reason it never caught on. However, as bike technology (and geometry) has progressed, we’ve learned more about the characteristics of 29in and 27.5in wheels and how to capitalise on the advantages in either size.
Now, the 'business up front, party out back' approach to wheel sizing is making a comeback, pitched as the golden ticket solution 650b wheels were originally said to offer and has become an increasingly common sight on the Enduro World Series podium.
With that, Colorado-based Alchemy Bikes has announced the new mixed wheel size Nine7Five, that comes stock with a 29er on the front and 27.5in wheel on the back. The frame is based around the Arktos 29 front triangle but gets a specially designed rear link to accommodate the smaller wheel — which will be available for current Arktos 29 owners.
How it works
The idea is with a 29er on the front you benefit from the added roll over and compliance of the larger wheel and the smaller rear wheel is stiffer, lighter and allows for a shorter rear end for quicker handling and better acceleration. On paper, it makes sense, but in practice, it doesn't work on every bike.
The Nine7Five sees 160mm of front travel and 140mm of squish at the rear using Alchemy’s dual linkage platform; Sine Suspension. Designed by David Earle, the name comes from the shock rate, which on a graph looks like a sine wave. According to Alchemy, the regression through the beginning of the travel allows for small bump sensitivity and climbing traction, while progression through the middle stroke prevents wallowing and the regression at the end allows for the full travel to be used.
With a smaller rear wheel and different link at the back, the effective top tube length and reach are shorter by 1mm, the head angle is slacker by a degree (65 degrees), the seat angle by half a degree, (74.5 degrees) and the BB is 8mm lower in each size. The chainstays are the same length and combine with the 44mm offset fork make for a 1178mm wheelbase in a size medium.
Currently, live on Alchemy’s website, the Arktos Nine7Five is offered in a GX, XT and X01 build, with prices starting at $5399 and framesets including a Fox DPX2 Factory Kashima EVOL shock going for $2,999. International pricing is to be announced.