Centre Lock/Six-Bolt Fixing

[Valbrona]

The rotors for Six-Bolt are thin and bendy allowing their use with calipers which feature one fixed pad - rotors are able to bend so they can contact both pads.

Not so the rotors for Centre Lock - thicker, not meant to bend, only suitable for calipers where both pads move.

Agree?

The assumption here is that if I want to run Centre Lock wheels in my bike which has calipers where only one pad moves I will need to use Centre Lock > Six Bolt adapters. And I am not going to bother with that faff so will just buy Six Bolt wheels.

Thanks.

[[XAP]Bob]

They’ll both move enough.

[Gattonero]

Depends a lot on the rotor you're going to use.

A rotor like this can flex enough


one like this maybe less

[Valbrona]

Thanks.

[Brucey]

note that some popular mechanical disc calipers (eg BB7) have parts that protrude towards the ID and run close to a 'normal' (i.e. flat) disc. These may interfere with the rivets/spider arms on discs like SM-RT98 (which have a big spider) and ICE-tech 'freeza' rotors (like the SM-RT99 model with the wibbly centre layer to the sandwich) may interfere where the wibbly layer is.

Thus the lateral flexibility of such rotors is moot; they may not even run through the calipers you intend to use.

This photo


shows the RH (inside) face of the disc rotor; you can see that the wibbly 'freeza' bit is likely to touch something first, with the spider close behind.


Note also that some of the centre lock discs with a smaller spider are labelled 'resin pads only' so you don't want those if you are intending to use sintered pads on them. The ICE tech discs run a bit cooler under most conditions (but suffer worse if they do ever get very hot) and one-piece (six-bolt) discs are cheap and readily available. They work fine with a centrelock adaptor BTW.

cheers

[gregoryoftours]

On a related topic, does anyone know why avid bb7 are supposed to be set up with a larger gap on the fixed pad side? It seems counter intuitive because the rotor has to flex more when the brake is applied. It can't be to do with rubbing clearance surely as it would rub on the outboard side just as readily.

[Brucey]

On a related topic, does anyone know why avid bb7 are supposed to be set up with a larger gap on the fixed pad side? It seems counter intuitive because the rotor has to flex more when the brake is applied. It can't be to do with rubbing clearance surely as it would rub on the outboard side just as readily.

the 'larger gap' is w.r.t. the gap in the caliper body, not w.r.t. the pads, like this;



The clearance to the pads themselves is equal each side. This setup ensures that, when the brake is on, the disc is deflected towards the middle of the slot in the caliper body, and keeps clear of the RH side of the caliper body for a fair while, even if the pads are not adjusted regularly.

BTW if you want to strip a BB7 caliper there are some useful instructions (which cover the non-obvious parts) here
http://forums.mtbr.com/attachments/brake-time/917036d1408545933-my-avid-bb7-brake-broke-untitled.jpg

also, this photo shows how the 'fingers' on BB7 pads might clout the ICE-tech discs



cheers

[gregoryoftours]

Ah, that totally makes sense! I've always wondered about that. Good to know about those stripdown instructions too, I'll use them at some point.