Last year, Mavic held a press conference about its latest 26in wheels. Despite being full of new technology and the latest racer feedback, nevertheless the meeting was prefaced with ‘Yes, we’re working on 29er wheels, but no, we don’t have any to show you yet’.
In truth, Mavic did have some 29er wheels nearly ready to go, but wasn’t ready to release it last summer. With another winter of testing, it’s now ready to release the details to the public. But only after letting us know that 29in wheels aren’t as easy to design as just making a 26in wheel bigger…
According to Mavic’s engineers, there’s a cubic relationship between an increase in diameter and a loss in stiffness, so a 29in wheel is 39% less stiff for the same materials. The same wheel will also weigh 10% more. A 29in will also have around 40% more inertia with the same materials due to the extra mass of the rim and spokes. Basically, what they want to get over is ‘Hey, it’s not as easy as it looks OK?’
This particularly seems to affect lightweight wheels, where even on the 26in version, everything is as pared down as possible. Mavic’s SLR wheel is already a good example of making things as light as you can (without going all carbon), with the spoke bed and sidewalls machined out, aluminium spokes and a light hub.
In order to get the lightest wheel they could, the engineer first tried just scaling everything up. This led to spokes breaking and a weaker wheel. They added more spokes, which stiffened the wheels and they tried fewer, stronger spokes. In both cases, the rim started cracking.
Mavic then tried making the rim a tiny bit (0.5mm) thicker for the same spoke bed width, this seemed to cure the rim issue, but then spokes started breaking on the rear wheel drive side. The answer to that was to shot-peen the drive side spokes for increased surface strength. Finally, it seemed that the issue was solved. So here is the new Mavic SLR 29er. Phew!
The front wheel will take 9mm QR or 15mm axles. There will be a Lefty version too. Using Mavic’s FORE technology, the spoke bed is undrilled and will take UST (and other) tubeless tyres. Weight for a pair of Mavic Crossmax SLR 29ers will be 1620g
Interestingly Mavic’s rufty tufty 26in wheel, the Crossmax ST wasn’t as hard to enlarge. In fact, Mavic did just increase the diameter, test the wheel and proclaim it to be completely suitable for all your 29in all-mountain needs. Does this suggest that the regular ST is a little overbuilt perhaps?
Weight for the29er Crossmax ST is 1710g. It’s still FORE drilled and UST tubeless, and still uses Mavic’s ITS-4 (super clicky, quick pickup) hub. The hubs really will take all the standards, with 9/15 and 20mm covered on the front and 9QR/12×135/142 at the back. Weight is 1710g.
And finally the CrossRide, Mavic’s entry level wheel also gets a big wheel cousin. The Crossride isn’t tubeless and doesn’t have the super quick pickup hub, but it does still offer 9/15mm at the front and 9/12×135 and 142 (options) at the back. There’s also a stronger rear axle and the new 29er specific rim. Weight will be 2020g
Mavic’s new 29ers will start appearing from July. Probably with the SLR wheels first – just in time for the Olympics eh?
Posted on: May 3, 2012