Unless you make one off adapters and use a rotor you adapted the caliper to which no one makes, or make a one off rotor, this will not work correctly. There is various safety concerns other than the pads overhanging and than touching once they wear down, leaving you with no front brakes. The pads are the least of your concerns as you can always change them.

The real problem lies with the un-swepted area that holds the rotor together. There is a reason why the pads do not come in contact with the little outside area of a rotor. That part keeps the rotor together on the perimeter. If anyone would experience a brake rotor explode at speed, than you would know first hand that you would not like it. There is no warning, it just happens and if you live through the experience, you will never wish to go through that experience again. There are many different reasons why brake rotors come apart and this serious mistake could be one of them. This is some measurements off of a random caliper. You can see the un-swepted area between the edge of the pads & the perimeter of the rotor.

 

Hmmm I'm still a little confused. Do you think you could dumb that down a little for me please ?

Also does this apply to the pre-06 bikes as well or only to the Fatbob? Im getting ready to do this conversion on my 04 Defender. I know HogPro has done this quite some time ago and he is running 11.8" rotors on his bike.

 

I think I understand what he's saying. If your pads overhang your rotor a couple of bad things could happen: 1) the pads will eventually wear down and touch along the edges causing decreased braking 2) the rotors will wear down on the edges and become thin with no reinforcement. Normally the rotor edge, w/ properly aligned pads, would have a non-worn edge, giving it rigidity. If this edge is worn because the pads overhang the rotor they could weaken and explode. please correct me if I don't get this right. At any rate the edge shouldnt wear down as fast.

 

basically, if you are putting friction to the outer area of the disc that isn't designed to be a friction surface, you can have the rotor explode.

or, brake pad touch perimeter of rotor bad. rotor go boom.

 

So both problems are solved by upgrading to a rotor that provides enough un-swept area on the edge. Why won't upgrading to the 11.8" rotors fix this issue?

 

Nice now I understand

So I still wanna make sure this is ok to do on a 2004 narrow glide if I upgrade to 11.8" rotors. I know others are running this set up but if there's a chance I could die I might want to reconsider.

 

As stated previously, in 2006 HD raised up the caliper mounts to use the same twin cam calipers found on 2000~2005 FXD & 2000~2007 FL models. Your 2004 FXD has the lower mounts and you are using a 11 1/2" rotor. With the Brembo calipers and raised caliper mounting you must use a 300mm rotor which is larger. All of this information is on this great site with multiple pictures. Just use the search function.

Your 2004 caliper mounts are at a different measurement than the 2006 FXD. The HD Brembo caliper has a longer mount to allow the use on a 2008~current Bagger of a 300mm rotor without raising up the caliper mounts. All 2000~Current caliper mounts on FL have never changed.

 

So, either way using fatbob lowers you will have to fabricate a bracket to use HD Brembos or any sportbike take offs; Brembos, Tokicos, Nissins... Seems like the cheapest route would be to find some sportbike calipers and fab a bracket. You see them for cheap on Ebay all day! That seems to be what I'm going to start looking for.

 

fastharley, you seem to know a great deal about this topic. can you answer this question?
to do a duel disc set up on my 2011 street bob. can i use the fat bob lowers (witch have the same part # as mine) and what calliper do you think i should run? what size disc would i need to run on that set up? you did just say that later dyna's have a mount set higher than older models so i would need bigger than 300mm discs ? i haven't found anyone that has done this on a 49mm front end yet. perhaps you know.

 

Thank you sir

And yes I should have searched first ... I can see you've answered this question many times before