sijray21

hello,

i'm not sure what to do and what my options are, but i'm having trouble installing my front brake caliper onto my fork. the fork is a cannondale carbon fork with carbon steerer for a '10 CAAD9-5 and the brake caliper is a SRAM Rival.

the problem is that the 'bolt' that screws to the back of the caliper has a head that is too thick for the hole. the skinny part of the 'nut' fits fine, but the head is too wide, but the 'nut' is not long enough to catch enough threads. i also have a specialized tarmac and the hole on that fork is large enough.

there are only two options from what i can tell:

1) have a shop drill out the hole to be a little larger. this seems like it's not a good option; i don't want to ruin the integrity of the fork.

2) find another 'nut' that will be compatible for the caliper; perhaps a longer 'nut'. i'm not sure if they make them or where i could find them.

i thought i'd ask you all since i'm a n00b. i've posted some pictures for reference.

thanks,
Jason

Bianchigirll 

it looks to me like the 'head' is not intended to go in the hole. if you look at your other fork you may find the hole is stepped so the nut fits flush to the surface. maybe a more Cdale experienced person will know better but it looks right to me. I might even consider a small washer.

Jeff Wills

Recessed nuts for installing calipers come in many different lengths. If the one you have is too short, get a longer one.

https://harriscyclery.net/product/pro...o1500-qc49.htm
https://harriscyclery.net/product/pro...o1502-qc49.htm

reptilezs

longer nuts are available. some forks don't have a recessed area for the nut. i think some madone forks, dont remember and the nut has a bigger head that the traditional recessed nut. im not familiar with cannondale forks.

sijray21

thanks for the quick reply guys and thanks for the links. my current mounting nut is 20mm, so i think the 30mm nut will work well.

should i worry about thread pitch or other thread characteristics? or are all newer brake caliper bolts pretty much standardized?

i'm also researching torque specs, but if anyone wants to chime in that would be helpful :-)

thanks again!

FBinNY 

They all have the same 6mm thread and shank OD. The heads do vary, but if it doesn't have to pocket into a counter-bore (recess) head diameter doesn't matter. Buy the right length - long enough to engage 7 or more threads without bottoming - and don't sweat it over other details, but since it'll show you might look for a nice finish.

furballi

You only need 3 threads engaged to achieve optimum clamping force.

FBinNY 

Yes and no. Full strength is achieved at just over 3 threads of full thread engagement, and 3 is plenty adequate, but the key here is full threads

However, the nut has a chamfer at the end, so it's first thread doesn't count, likewise with the screw where often the 1st 1-1/2 threads are partial, so we're now closer to 6 threads, and I added a few threads because I know folks tend to pinch at the margins when they feel they need to. That's how I came up with 7-10. But yes 3 full threads would do the trick.

furballi

The small amount of "chamfer" at the end is irrelevant because the clamping force required to secure the brake to the frame is much lower than the maximum load carrying capability of the bolt! Add a few star washers between the bolt and the frame if the user is super paranoid. If this is a matter of life-and-death, then I would take the time to mount a bolt into the tensile meter with only 3 thread engaged and post a load graph for educational purpose.

HillRider

"Recessed nut" brake mounts come in at least three configurations. 1)Some have the nut head sitting exposed at the back of the fork crown as shown in the OP's picture. 2)Some have a shallow counterbored pocket so the nut head sits flush with the rear of fork crown. 3)Some, like my Easton EC90s, have a deep recess as large as the nut head drilled in the back of the fork crown and a shoulder inside the recess for the head to butt up against so the nut is completely out of sight.

All of these work if you have the proper length nut.