# RockShox Recommended Disc Brake Rotor Sizes (xpost brakes)



## RED5 (Jan 4, 2004)

***Just off PinkBike, thanks Acadian for the info**
http://www.pinkbike.com/modules/news/?op=articleview&id=1870

SRAM has received a number of inquiries lately regarding RockShox fork and disc brake rotor sizes. Following is a list of all RockShox fork platforms and the maximum recommended disc brake rotor size.

Fork Platform Maximum Recommended Rotor Size 
GPS 165mm 
Judy 165mm 
Pilot 165mm 
SID 165mm 
Duke 210mm 
Psylo 210mm 
Boxxer 210mm

SRAM tests the structural integrity of all RockShox forks to that of the 210mm disc brake rotor size. However, other factors, including fork stiffness, bushing design, and intended use are considered when determining maximum rotor size

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
For additional information please contact Michael Zellmann
PR & Media Manage
SRAM Corporatio
Tel: 312 664 3546
Email: [email protected]


----------



## zedro (Jan 12, 2004)

another blow to the 'no 8" rotors on qr forks' police.


----------



## RED5 (Jan 4, 2004)

*How do you figure*

the Duke and Psylo can both run a 210mm ( 8") rotor and they're QR forks. Am I confused?? If so please explain.


----------



## BalleRacing (Jan 17, 2004)

*Psylo also has 20mm Tulio thru-axle*



red5 said:


> ***Just off PinkBike, thanks Acadian for the info**
> http://www.pinkbike.com/modules/news/?op=articleview&id=1870
> 
> SRAM has received a number of inquiries lately regarding RockShox fork and disc brake rotor sizes. Following is a list of all RockShox fork platforms and the maximum recommended disc brake rotor size.
> ...


The Psylo also has 20mm Tulio thru-axle version, but it is different than most 20mm thru-axle forks because the caliper mount tabs are at the same distance from the rotor as a QR fork so it uses a different Hayes adapter 98-15604 "IS" 8" QR not a 98-15069 "IS" 8" 20mm like most 20mm thru-axle forks. http://www.hayesdiscbrake.com/MountBracketChart2004.htm
The Duke looks like it only comes in QR. My take on the 8" rotor on a QR fork is on some forks the caliper mount tabs are not made as strong on some fork manufacturers so when you put a 8" rotor on a fork that is designed light for XC and a 6" rotor, you will need to put a adapter to move the caliper farther away from the axle center line. By adding a longer adapter on the caliper mount tabs you increase the cantilever load that the caliper will put on the caliper mount tabs. If you ride in rough trails the caliper is excelerating rapidly as you hit large bumps creating high G forces on the caliper mount tabs. The rider doesn't feel all the loads the bike is absorbing that is why the freewheels in rear hubs tend to fail sooner in downhill bikes than XC bikes because the long travel suspension allows you to go over rocky sections at high speeds but the hubs and the fork lowers are seeing high G forces. I think the problems some fork makers have had with using a 8" rotor on a 6" QR fork is the caliper mount tabs were fatigue cracking not the QR being pushed out of the drop outs. I think the bike that had the QR come out while using a 8" rotor was a improperly modified bike. The bike was a tandem two seater that had the drop out retention bosses filed off. A tandem bike requires double the braking force to stop it as a regular moutain bike. Also on a regular mountain bike you can only put so much braking force on the front brake before you flip over, but on a tandem bike you can put way more front braking force because it is much longer and you have the weight of another person in the back to keep it from fliping forward. If the tandem bike had a 6" rotor on it I think the QR would come out even sooner because you will have to apply more pad pressure to get the same stopping power.
Erik,


----------

