yessamgerg

This will be an ongoing post as I've got a lot of documentation to share but I wanted to at least get started.

After getting fed up replacing rear bearings, rotors and pads I figured it was time to make a proper vented rotor setup to match my front Urge/Essex front brakes.

After searching for an off the shelf solution I never really found anything that I liked that had a good pad selection and didn't require modifying pads due to trying to reuse the stock caliper. This eliminated the Urge rear rotor (modifying stock size pads), racing brake (same), J's racing (stupidly expensive) and basically required me to go custom.

After some searching I found the AP racing stock car catalog which is where the Essex front kit sources their rotors.

The rotor I'm using is a 11.75x0.81" vented J-hook rotor (matches the front rotor). Rotor rings are always stocked and only $132 each which is extremely reasonable. I'm expecting the rings to last basically forever as they are likely a bit overkill for my need.



COMING SOON

Hat & current fixed mount hardware:

Caliper & mounting bracket:

Pad selection:

Bais calculations:

yessamgerg

Reserved

Bullwings

awesomeness. Where did you source your RX-7 caliper? And for how much? PM if you don't want to share publicly.

Thanks!

yessamgerg

It's an RX-8 caliper and I just bought remanufactured calipers from fleebay, I'm planning to post a list of parts but the calipers were ~$120 each. Total cost was about $800 all said and done including pads but I did all the machining myself so it would probably have been about $1200 if you don't have access to a machine shop. For the fixed rotors everything can be machined manually.

If I had to do it again I would have just bought the sake bomb kit but it wasn't released at the time I started...

SakeBomb Garage

Thanks and we do like your solution! We just couldn't get the fitment we needed without grinding the caliper so we went to a larger disc. BTW Dave says he thinks he was able to calculate your e-brake angle change and we think we've got brackets for ya! Shoot me a text message (and again) nice work buddy!! Love to see innovation. Great minds think alike

ckowalc

Any update on this? I see Wilwood 'Ultralight' 11.75" x 0.81" rotors can be had for $30-35 a piece.

Curious to see how the caliper is mounted.

yessamgerg

Sorry i've been really busy and haven't had any time to update. I've done 4 track days with these at various tracks and they have been rock solid, perfectly consistent with no fade or issues at all. I looked at the Wilwood rotors and although they are cheap they are inferior to the AP rings. They are straight vane and not as high quality metallurgy as the AP. The rear rotors I used are likely a bit overkill for the application but they should be pretty much bulletproof. The stock rears historically are just about shot after 4 or so days and these barely look used. They have no cracks of any sort and just have very light surface wear, they should last for several years I think in which case I dont think its worth trying so go to a cheaper Wilwood rotor as these rotors should end up costing like $50/year. Plus they match my front rotors...

Attached are some more pictures of the setup, Ill try to remember to take some at there current state tomorrow to show the state they are now at. Again, if I were to do it again I would totally do the new Sakebomb kit as its bolt on, includes parking brake adapters and has basically the same disk (~314x20 vs my 299x20). My total cost cheaper than theirs (all told I spent about $700, 20 hours of design and about 10 hours of machining) for my entire setup but I have access to a full machine shop. Also mine doesn't currently include parking brake brackets. If Sakebomb had announced their kit when I started on mine I would have totally waited and gone with theirs. Based on my experience with my setup and how similar it is to theirs I would think that theirs should be able to perform flawlessly on a track or street cars for many years with worries.

ckowalc

Thanks for the pictures. I assume the caliper and rotor surface is sitting farther outboard than the OEM?

The Wilwood UL32 rotor has been used on a UUC E30 front big brake kit. I think it'd easily hold up to rear braking capabilities of an NA S2000. Plus, you could always upgrade to one of their higher quality (more expensive) rotors if it was desired.

It's a shame the Sakebomb rear brake kit doesn't use these off-the-shelf 300mm x 20mm (11.75" x 0.81") rotors, Wilwood, AP Racing or otherwise. I think it would appeal to a much wider customer base as it would make their kit cheaper and bring the brake bias closer to stock for people with OEM or StopTech ST-40 front brakes. Most people are running a square tire setup (more front grip than OEM) and would probably want to avoid running more rear bias than necessary.

I guess if I find I need a rear brake solution, I'll have to stick with the URGE vented rear rotor option for now or dedicate some time to mock up my own.

On a side note, if Sakebomb could figure out how to use an FD RX7 rear caliper (not sure on pad annulus but I'll assume 38.5mm like S2000 and RX8):

yessamgerg

I think the reason they didn't want to use a smaller rotor is that you have to grind the caliper brake a good bit to make it fit on this small of a rotor, the extra diameter only causes about 2% more rear bias than my setup so it shouldn't be a huge concern. Keep in mind that you can get a pretty massive change in bias with pads. I'm running DTC-30 front and HP+ rear, this moves the bias enough to keep it well within the desired range. It's also helpful to run the pad split as this rear rotor runs a good bit cooler than the front so it helps to keep the pads in a good temp range. Also this setup doesn't require sanding a new set of pads to allow it to work as sanding pads is difficult and very bad for your health...

ckowalc

Ahh, I didn't realize grinding of the caliper bracket was required. That makes more sense.

I'm aware that the extra 14mm on the rotor diameter causes ~2.5% bias shift rearward. Also, with the Hawk DTC compounds at least, there is ~0.1 difference in friction coefficient between each compound in there intended temp. operating range. This translates to ~3% bias shift with each compound which I personally wouldn't call "pretty massive". Seeing as a lot of people with OEM brake bias already run a more aggressive front pad compound due to their square tire setup or grippier tires, it also limits your your brake pad selection. Having to run a high friction front pad to account for brake bias may not be to everyone's liking, certainly not mine.

Not everyone will agree but sanding brake pads/backing plates or rotating used pads seems like less of a compromise than trying to account for a 9% shift in brake bias with pad compounds.