Crux + RockShox Rudy?

[ccie6872]

(hopefully w/o getting into a debate of suspension on a gravel/cross bike) Curious if anyone has ventured into trying the RockShox Rudy on their Crux? All reviews seams to be really good on the Rudy and considering to try it on my Sworks Crux for some of the rougher single tracks in my area. Fairly easy to install/remove with the exception of cutting the brake line and re-bleeding.

[yinzerniner]

Seems like a bad idea
-Rockshox Rudy is 425-435mm length vs 401 crux fork length
-Crux headtube junction isn't reinforced for extra loading that suspension fork requires

For the 30-40mm of suspension provided you're porbably better off just using a very large front tire with lower pressure and MTB inserts, which will improve handing and comfort as much if not more that the fork for much less money and won't screw with the geometry or invalidate your warranty

[FreeZ]

I was thinking that same setup or with Lauf Grit SL. Looking for some extra softness for next winter and very rough ice roads.

Anybody found the limits with Crux tyre sizing?

[Discodan]

Seems like a bad idea
-Rockshox Rudy is 425-435mm length vs 401 crux fork length
-Crux headtube junction isn't reinforced for extra loading that suspension fork requires

For the 30-40mm of suspension provided you're porbably better off just using a very large front tire with lower pressure and MTB inserts, which will improve handing and comfort as much if not more that the fork for much less money and won't screw with the geometry or invalidate your warranty

I agree with the fork length issue but not so sure about the need for a stronger headtube. If anything the suspension would reduce the impacts the HT receives on a daily basis and would be the same for a big hit that bottoms out the suspension. What do you think drives the need for a stronger HT, assuming the geo was the same?

[yinzerniner]

I agree with the fork length issue but not so sure about the need for a stronger headtube. If anything the suspension would reduce the impacts the HT receives on a daily basis and would be the same for a big hit that bottoms out the suspension. What do you think drives the need for a stronger HT, assuming the geo was the same?

I'm not a frame design expert, but I do know that carbon fiber is an anisotropic material ie orientation is key to delivering strength. With that knowledge carbon fiber head tubes are made to match up with carbon fiber forks which flex differently than suspension forks. While suspension forks obviously provide up and down force reduction, the fore/aft and left/right force reduction is probably more than carbon forks since the suspension fork has to be super stiff/rigid to account for the suspension system.

In other words, carbon fiber forks have flex/movement designed into them through multiple axes, while suspension forks mostly have movement in a single direction. If the head tube isn't reinforced to deal with the extra forces from a stiffer fork then it could cause premature failure and would defintely invalidate any warranty.

Also the longer lever of a larger A-C will require a stronger head tube since the forces will be greater. An A-C difference of 24-34mm vs a 401mm fork will result in 5.9-8.4% greater force felt at the head tube. While that might seem like little, again the Crux is already a somewhat slight build and who knows what the margin for error is when it comes to Specialized and Carbon (see: SL7, Alpinist/Rapide tubeless).

That is just a guess, but seems to bear fruit in something like the Cannondale Topstone. It's designed for both a rigid carbon fork and the Lefty Oliver, but with the rigid fork it's been noted to be just too chattery and stiff at the front end, and really needs the Oliver to feel whole.

[ghostinthemachine]

...

[rjich]

Personally I wouldn't mess around with adding suspension to my crux, But only down to the lack of compatibility shared above and my fear of breaking parts by running out of spec. Such a pain to replace that frame for a punt.
50mm tires make things pretty squishy for a stop gap. Maybe a redshift shockstop stem would be better and lighter ?

[tonytourist]

Hop on IG and ask this guy whether he's had any issues:
https://www.instagram.com/p/CUvAfFXJ1zU/