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Okay, brake rotors are weighed. I used a handy kitchen scale by OXO, from Bed, Bath & Beyond. About $50, before any kind of coupon. It works very nicely, and has a detachable panel so that you can read it with larger items sitting on the scale (like brake rotors), but maxes out at eleven pounds.
First, a size comparison. New 13" rotor is on the bottom, HD 11.5" rotor on the top, centered:
Another comparison, this time aligned on one edge:
Left side HD rotor:
Right side HD rotor (note the half once difference):
Left side BrakeTech rotor:
Right side BrakeTech... EXACTLY the same weight:
Here are both HD rotors:
And both BrakeTech rotors:
So, here are the results: A combined total of three additional inches of rotor diameter, and an unsprung weight reduction 2.3 ounces shy of two pounds.
And a quick side-by-side, sitting on the front wheel:
Now I really need to figure out where on earth I put the ARP rotor hardware I got from Alloy Boltz last year... It's unbelievable how good at losing things I am.
You may need to get new caliper bolts. With the larger rotors the calipers need to be moved out further. I had to buy longer bolts to make this happen safely. Rotors do look good. I'm excited to see how mine work.
You may need to get new caliper bolts. With the larger rotors the calipers need to be moved out further. I had to buy longer bolts to make this happen safely. Rotors do look good. I'm excited to see how mine work.
I actually ordered a set of Speed Merchant 13" brackets (they should arrive later this week). I didn't really want to run spacers that long on my 11.5" brackets. SM confirmed that my existing hardware will work with the 13" brackets which is nice, since I have show-polished stainless ARP bolts from AlloyBoltz for both bracket to fork and caliper to bracket.
Interesting. I bet the moment of inertia went WAY down. Can't wait to hear how this all comes together in the first ride.
You and me both, Chris! Big box from Howard is supposed to arrive tomorrow...
With regard to the "moment of inertia," here's BrakeTech's literature on these rotors, discussing the "fulcrum" which would be the same line of thinking:
"Regarding the size difference (11.5"/292mm, 320mm vs 330mm), it all comes down to the mechanical advantage produced by moving the fulcrum point further out for more leverage on the wheel. There is also the proportional advantage of greater thermal capacity created by more mass and surface area of the larger unit. The additional advantage inherent in all the AXIS series floaters is that they are indeed genuine full-floaters free to move on their carriers. This reduces brake drag along with all the endemic benefits associated with that including brakes that run cooler than their semi-floating brethren. The newest of the trio is the 330mm x 6mm race rotors, added to provide more flexibility in size for Pro-level race teams."
Bolted the new rotors onto the front wheel today. I ran a thread restorer through each hole (a bunch of old Loctite came out), cleaned and waxed the wheel while everything was accessible, and torqued them on using new polished ARP hardware. I called Jeff at BrakeTech with a quick install question first... Since there are six bobbins on each rotor but only five bolts, I had several options in terms of left to right alignment between the two rotors. I wasn't sure whether the "waves" should be offset or line up with each other. He explained that the "pockets" are shallow enough (5mm) that the rotors behave like a round disk. They're really just pocketed for weight reduction. Totally up to me how I line them up. I decided to line them up with each other, assuming it would bug me if they were asymmetrical for no functional reason.
In case anyone out there is obsessed with minor weight details, I put the old Harley chrome bolts on the scale, and the new ARP stainless set... With all ten bolts on the scale, the HD set was actually .4 oz lighter than the new ones. Oh well, can't win every time!
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