Bigger rear rotor for underslung Brembos - Honda RC51 Forum : RC51 Motorcycle Forums
 
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post #1 of 3 (permalink) Old 01-26-2017, 07:56 PM Thread Starter
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Bigger rear rotor for underslung Brembos

I don't know if anyone has followed my Facebook post, but after installing an underslung Brembo I noticed an issue with the pads not really matching up to the rotor when using the billet Brembo calipers. I don't think this issue is specific to just my bike and bracket, as other bikes that are using other underslung brackets LOOK to my eye to have the same issue. Sooo...I reached out to Jeff at Braketech about cooking me up a custom rotor to resolve the issue. Turns out it would be cost prohibitive to do a one-off, but if I can put together a group buy of at least 10 he can do them for $350 a piece. Not terrible since he has to run new tooling to pull it off. Throwing this up here to gauge interest and see if we can make it happen!

The nuts and bolts...

From what I can tell with my (mitutoyo) calipers, the pads extend past the rotor about 4.2mm. Likely closer to 4mm because of the angle that I had to take the measurement. Brembo recommends that the rotor sits .5mm proud of the pads. So if we have a rotor that is 10mm more in diameter and 5mm more in radius, by my estimate we would end up with the new rotor sitting between 0.8mm and 1.0mm proud of the pad. I would rather error slightly too big than too small. On the inside of the swept area it appears that I'm missing the previously used part of the rotor by a similar 5mm amount. It's impossible to get my caliper in there to measure for sure but I held up 5 mm and "eyeballed it" and it looked pretty much dead on. There is a bit over 8mm between the rotor and the bridge, so even after removing 5mm we are still safe with Brembo's 2mm minimum recommendation.

Assuming that is consistent across the board for everyone, we just need a measurement of a stock rotor diameter to work from. I know its supposed to be 220mm, but its worth double checking. Does anyone have one off the bike already that they can measure? I can pull my wheel if need be...

What do you guys think?

Added some pics:




Last edited by Denver_larry; 01-26-2017 at 08:11 PM.
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post #2 of 3 (permalink) Old 01-27-2017, 10:24 AM Thread Starter
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Bigger rear rotor for underslung Brembos

Jeff was kind enough to pass along his preliminary CAD drawing to me:


The finished product will look pretty close to this:


Link the the Braketech Rear Floater page: LINK

I've started getting some responses with guys on FB who are in on the group buy so I'm starting a list here. As soon as I have 10 committed and paid I'll get the ball rolling for real with Braketech to get these made. This apparently effects any of the brackets that Andy Goetz produced, as well as the Scotts bracket that he took the design dimensions from. Word from Andy is that the Ladybird brackets suffer the same issue, so that should affect just about everyone with an underslung caliper!

Those who have paid are in bold
1. Me
2. M Jay Mounteney
3. Andy Goetz
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Last edited by Denver_larry; 01-29-2017 at 02:50 PM.
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post #3 of 3 (permalink) Old 01-31-2017, 01:52 PM Thread Starter
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Given the lack of interest, I'm looking into another solution. There seems to be just enough room to have a different bracket made that will still work with a stock wheel. Stay tuned...
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