Cervélo only officially revealed their new carbon ZFS-5 full-suspension cross-country race mountain bike a few days ago, and they’ve already shown how the Jumbo-Visma team used a rigid LinkLock to convert it back to a hardtail! Unbolt the short link, remove the standard RockShox SIDLuxe Ultimate shock & its remote, then bolt in a peculiar wishbone strut in its place.
But why?
all photos by Cory Benson, copyright Bikerumor.com
The “why” is “because UCI“.
The governing body of pro mountain bike racing, the UCI MTB World Cup rules require that cross-country racers must compete in the XCC short track race on the same bike as they ride in the main event Olympic-distance XCO cross-country race. But a closer look at the rules actually only specifies that it must be the same frame.
Individual components – like those that can be removed or replaced on the frame… for example wheels, tires, and gearing – are allowed to be swapped out to adapt the bike to the shorter, faster, and less technical nature of the short-track circuit racing. So while some racers would simply lock out their rear shock for the duration of the half hour XCC race – why not take it to the next level.
So, Cervélo engineers worked with the Jumbo-Visma team to devise a rigid shock replacement for their new ZFS-5 fully… a link to lock out the frame… a LinkLock.
Tech Detail
The Cervélo ZFS LinkLock is a relatively simple piece of CNC-machined 7000-series aluminum, engineered to accommodate the specific loads exerted on the frame while off-road racing with effectively no movement or loss of rider energy input.
Just bolt it into the same mounts as the shock & short link. It’s meant to be stiff and unmoving, leaving any flex or bump absorption to the carbon frame.
Interestingly, this one functional alloy prototype was made with what amounts to a flip-chip insert at its attachment point to the end of the seatstays. This allowed the team to experiment a bit with the geometry of the ‘locked-out’ full-suspension hardtail. Did they want to replicate the position of the fully-extended unloaded shock.
Instead, Milan Vader raced the Nové Město na Moravě World Cup XCC short-track race in the forward flip-chip position that more accurately preserves the geometry of the bike as it would be at proper suspension sag.
What’s Next?
Neither Jumbo-Visma nor Cervélo see the LinkLock as a realistic consumer product, but that doesn’t mean they’ll stop development work on it. I spoke with both Cervélo’s XC product manager and Milan himself today, and both seem passionate & willing to try out new ideas on the path to innovating cross-country race bikes.
And there will be another generation of the LinkLock. Next up will probably be a 3D-printed version, topology-optimized to shave weight off this aluminum version. The team will likely keep playing with the idea as long as World Cup courses necessitate a full-suspension XC bike for the longer XCO racing while a theoretical hardtail could be a better fit for the XCO short track.
