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Cervélo LinkLock Lockout Turns ZFS-5 XC Bike into a Hardtail for XCC Short Track Racing

Cervelo ZFS-5 LinkLock prototype lockout gadget, XCO full-suspension to XCC hardtail conversion
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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?

Cervélo LinkLock converts XCO ZFS fully into an XCC hardtail

Cervelo ZFS-5 LinkLock prototype lockout gadget, XCO full-suspension to XCC hardtail conversion, Milan Vader racing
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.

Cervelo ZFS-5 LinkLock prototype lockout gadget, XCO full-suspension to XCC hardtail conversion, with or without rear suspension

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

Cervelo ZFS-5 LinkLock prototype lockout gadget, XCO full-suspension to XCC hardtail conversion, short-track race-ready

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.

Cervelo ZFS-5 LinkLock prototype lockout gadget, XCO full-suspension to XCC hardtail conversion, with shock

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.

Cervelo ZFS-5 LinkLock prototype lockout gadget, XCO full-suspension to XCC hardtail conversion, without shock, with geometry flip-chip

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.

Cervelo ZFS-5 LinkLock prototype lockout gadget, XCO full-suspension to XCC hardtail conversion, short-track tuning

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?

Cervelo ZFS-5 LinkLock prototype lockout gadget, XCO full-suspension to XCC hardtail conversion, Milan Vader Jumbo-Visma

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.

Cervelo ZFS-5 LinkLock prototype lockout gadget, XCO full-suspension to XCC hardtail conversion, 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.

Cervelo.com

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Jaap
Jaap
11 months ago

Somehow they got me, this is really cool stuff.

myke
myke
11 months ago

Not really impressed. It could also be problematic as the frame design may not be optimized for this kind of mounting adapter. IE, the frame may not be able to handle that kind of stress.

BikesIGuess
BikesIGuess
11 months ago
Reply to  myke

Yeah, I can’t imagine it would be any higher forces than a hard bottom out however, which I’d assume would be within tolerances, but maybe not at the frequency this might subject it to.
I’m sure in a professional space where the bike is assumed to be cared for and inspected frequently, they’re able to keep closer eye

TypeVertigo
11 months ago
Reply to  myke

That would be a concern if this was an aftermarket product, but this is the same company that makes the frame we’re talking about. If anyone would know about “the frame not being able to handle that kind of stress” it would be THEM.

myke
myke
11 months ago
Reply to  TypeVertigo

That has no bearing if R&D is done. This is a pro team and thus are the beta testers. So long-term results are non-existent.

WhateverBikes
11 months ago
Reply to  myke

You are way overthinking this. Fullies have had lockouts for their suspension for ages, and in all that time that has not proved a problem.
Also about the pro riders being beta testers, that too has been true for as long as racing exists.

Fake Namerton
Fake Namerton
11 months ago
Reply to  myke

I’m sure that Ten Tech the manufacturer of these frames has a handle on what kind of stresses these frames can take and where.

Brad Comis
Brad Comis
11 months ago
Reply to  myke

Generally frame stress and fatigue tests are performed with a steel bar in place of a shock, so this isn’t massively different. It is also possible that Cervelo has run this link through the appropriate testing to ensure that this holds up.

Lino
Lino
11 months ago
Reply to  myke

full suspension frames are tested with solid steel false shocks. This is exactly how it would be tested in fatigue during development.

Harold Solomon
Harold Solomon
11 months ago

LinkLock looks like the answer to a bikepacker who wants full-suspension except for the occasional bike packing trip.

OzRen
OzRen
11 months ago
Reply to  Harold Solomon

Or someone who rides various trails and doesn’t always need full suspension. Plus, if it was relatively inexpensive ($100 or so), I think it would be worthwhile to have as a way to ride your bike if the suspension needs to be serviced/sent out/warrantied.

Luiggi
Luiggi
11 months ago

Tell me you’re a road brand without telling me you’re a road brand…

WhateverBikes
11 months ago
Reply to  Luiggi

Did you even read why they do it?
If anything, this road brand is more experimental here than the established mtb brands.

Luiggi
Luiggi
11 months ago
Reply to  WhateverBikes

There’s “experimental” and there’s stupid. And I’m telling you, this isn’t experimental.

WhateverBikes
11 months ago
Reply to  Luiggi

You can ‘tell’ all you want, but what authority exactly do you have, Luiggi? On what basis do you get to decide about this?

Marcel
Marcel
11 months ago
Reply to  Luiggi

Tell me you’re a 90’s mountainbiker who still loves his roadie vs. mountainbiker talk without telling me you’re a 90’s mountainbiker….

Shafty
Shafty
11 months ago

This is absolutely stupid. Inflate the shocks to max pressure and save yourself the time and “R&D”. Maybe they forgot that was an option. What, was there one guy on the team that kept screaming “…but it’s not a hardtail!”?

Chirrsss
Chirrsss
11 months ago
Reply to  Shafty

Ever set up a full suspension? Heard of sag? Think about that and how it affects geometry.

WhateverBikes
11 months ago
Reply to  Shafty

LOL, why are you so mad? This thing is lighter, and it’s quite easy to make, and it will not have taken a huge amount of R&D. Plus you can dial in the desired geometry (emulating the sag that it has with the normal suspension setup, for example), something you can not do when inflating the suspension to the max. Maybe, just maybe, they didn’t ‘forget that was an option’ but considered this a better option.

Wildfyhf
Wildfyhf
6 months ago

They do make a hard tail xc bike. Why not just ride that?

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