V8R Stoptech 11.75" BBK
 

Posting this in Race Prep because this is exactly where it's most relevant. New release from V8Roadsters that we're very excited about.

The back-story...
By now everyone's seen the Stoptech 11" brake kit for the NA/NB. Some very cool elements in that kit, great calipers. But, someone over there missed the memo that the collective Miata performance community figured out how to fit 11.75" rotors under the car about a decade ago. For many of us running 11.75" kits now, downgrading on rotor size for less braking torque and thermal capacity as a trade-off to get a more rigid caliper isn't a great recipe.

We weren't the only ones wishing ST had done their kit in 11.75". V8R designed a new bracket to fit the ST42 and STR42 calipers over the super popular 11.75" rotor, then they worked with ST to refine the outer shape of those calipers to improve wheel clearance.

http://www.mazdatalkforum.com/downlo...hp?id=4460&t=1
** STR42 caliper pictured**

The ST42 caliper is a forged/machined caliper with bridge bolt that is super rigid. The STR42 is a badass true motorsport-grade billet version of the ST42. Both take ST's DR-22 pad shape which is the same as Wilwood's 7816 pad so there are lots of pad options.

You can get these direct from V8R and they're already in stock. We will be offering these kits complete with AP Racing rotor option and will have Porterfield and PFC pad options shortly. I have some PFC pads on the way to verify fitment.
All of the 11.75"" kits use the 36/38mm piston size (3.34 in³ piston area) which balances very well with a Sport package rear brake setup or similar.

Perhaps the best part... The price on these kits is competitive with the standard ST 11" kits.

http://www.mazdatalkforum.com/downlo...hp?id=4461&t=1
Pictured above: 15x8 Black RPF1 +28mm

Wheel fitment

If you're considering running this glorious kit, you're on 15x10" wheels right? Riiiight? That said, we'll be getting lots of inquiries about which wheels fit so here's what we've tested so far:

15x10 6UL and 15x10 Jongbloed have tons of clearance

15x9 6UL (gen 1): tight but OK
15x9 6UL (gen 2 & 3): Spins but clearance is too tight. Needs 5mm spacer to get minimum acceptable clearance
15x9 6UL (gen 4): Contacts the barrel. Needs 10mm spacer to get minimum acceptable clearance
15x9 Storm S1: OK

15x8 RPF1 +28mm: tight but OK (surprisingly)

http://www.mazdatalkforum.com/downlo...hp?id=4462&t=1
Pictured above: 15x10 Tungsten 6UL

Update - fits 15x8 Storm S1 and S2 without spacers.

That does look amazing. Can't wait for some track testimonials!

Both the ST42 and STR42 are available with either 38/36mm or 36/30mm pistons. The larger ones work best with sport rears and the smaller one better with stock 1.8 rears.

I really look forward to this upgrade!

Welp... now I'm never going to sell my v8r wilwood bbk... I guess I'll just install them

Do you have a picture with pads installed? Curious what the rotor / pad coverage is.

While the ST42 and STR42 come in both piston variants, AFAIK V8R is only ordering the 36/38's from Stoptech. Unlike the standard ST kits which can be ordered with either piston size, the 11.75" kits are 36/38 by default. Might be possible to special request for the smaller piston sizes, I'm not sure.

One not-so-small reason for this is the 36/38's are the right match for the existing rear Powerlite/10.9" kit, and it just may also be the right match for some new rear stuff that is brewing ;)

Pads are on the way, can shoot a pic when they arrive. But, not sure what you're trying to see. Swept height?

Any chance of testing these with +0 wheels ? I bought the 11.75" radial wilwood kit last black friday that didn't fit. :(

I just re crunched the bias numbers. The larger ST calipers look borderline with a sport rear rotor and 1.8 calipers. Not really great though. MC to caliper volume takes a hit too and will have a longer pedal with stock 1.8 master. With Aero you're gonna want more bite from larger sport calipers or V8R rears to balance it out. 15/16" or 1" master is a must have IMHO.

If I had stock 1.8 rears with smaller rotors and stock 7/8" master I would go for the smaller piston ST calipers. That would be a better pedal and balance front to rear. Even with the larger 10.90 rotors I like that combo better than the bigger calipers.

One of the things that got me the most excited is the larger V8R ST Front/Sport rear combo looks to be the perfect foundation for a manual brake conversion. The extra piston area helps increase wheel torque. Move the MC mounting point down and play with MC sizes and I think you'll get there. Not gonna be something I try right out of the gate though. I got a 1" master all plumbed in place with Sport booster. I suspect that with the V8R ST Front/Sport rear combo will keep me happy for a while.

Pads are thinner than the superlite calipers but they have a bigger area so they should grab better but last slightly less. The calipers are pretty spiffy looking, I like the appearance. Need a beta tester? :P

How's the pad change on these? Looks like a couple of allen bolts to pull the caliper apart?

I see talk of the 1.8 MC, what bout the 1.6 MC? Are they different, and if so by how much?

I currently have a 1.6 car with sport brakes and feel like pedal travel is a bit long.

That's the word for it, basically how much of the rotor is in contact with the pad. We had to have custom pads made for the original 11.75" Wilwood setup to get proper coverage or swept height

Get a wilwood 1" master kit.

The Superlight/11.75" kit by TSE is the top choice for an endurance car looking to maximize pad life. Larger pads (thus larger caliper) comes with a trade-off... The STR42 caliper is ~2lbs lighter than a Superlight.

Pad change: no disassembling of the caliper, you just pull the single bridge bolt on the top and the pads pull out/drop in from the top. The ST calipers have a shelf that the bottom of the pad rests on, unlike the wilwoods that require cotter pins to keep the pads from dropping through the bottom of the caliper.

Fun fact (I was digging through wilwood info this morning), on the dynapro wilwood claims the removal of the shelf was an improvement. This info is of no real use. Just funny.

Wilwood High Performance Disc Brakes - Caliper Product Number: 120-9703-SI

Perhaps it did help them slim the caliper down in some case where they had limited swept height available and needed to shave the base of the caliper down. IDK. I'm not saying one is better than the other, shelf vs. cotter pin, just pointing out the difference in the features.

Shelf = Abutment plate

The ST42 can use different abutment plates to carry different pad shapes; both the DR22 and the DR20 will fit in the ST/STR42 depending on the caliper config (part number). The abutment plate can be lower than the bottom of the caliper so that the edge of the pad can be placed as close to the center of the friction ring as possible, or higher if needed.

Abutment plates don't impact caliper width since the width is custom based on the rotor. The STR42 Miata application comes in 20.6mm wide with an existing option for 22mm wide.

The StopTech differential piston bores and stiffer caliper both combat pad taper so pads tend to last longer in these calipers.

Any idea what the cost of replacement rings is?
ST is generally very expensive in that area.

For the 11" Stoptech rotor, roughly $66 for a bare rotor ring or $90 with fresh hardware. Looks like the 11.75 AP is $134 per ring from Good-win, hardware not included.

They aren't stoptech rings on this kit. So buy whatever you want for the v8r hats. AP racing, wilwood, coleman. whatever.

When will these be on the website?

It's all about the gram.

This ^

Same 11.75" rotor ring flexibility as other 11.75" kits. So you can run <$40 wilwood rings, baller AP rings at $134, etc. Even on cars that usually run the good rotors, we really like having the flexibility to be able to swap in the cheap rings for testing new pad compounds.

^^^
speaking of good rotors...

can you tell a difference?

Yes, the wilwood blank econo rotors serve their purpose, but don't count on them for more than 14hrs of track life. That's less than my pads last

You can't tell a difference from the driver's seat in a single braking zone, but the differences are big and still very tangible.

For a while I ran IR sensors on the rotors. Initial temp rise in the first few opening laps is similar for budget rotors vs. good stuff, with differences showing up in the rate of cooling while the brakes aren't in use. After a couple laps the differences become more pronounced. A few laps in, the good rotor's temperature begins to slow their trend upwards and the budget stuff is still rising at a fast rate with each braking zone and not cooling as effectively during each gap between braking zones. After several laps the good rotors level off where the graph of each lap looks more or less like a repeat of the one before. The cheap rotors (hopefully) reach a similar leveling off point eventually but when they do it's at a higher average temperature.

Ultimately the good rotors are running significantly cooler over the course of many laps than the budget stuff - and that directly translates to much longer life, less warping, less heat in the rest of the system so less likely to boil fluid, overheat pads, etc. therefore more consistency, etc. etc.

This is exactly the kind of information I am/was after.

Thanks for not being a fucking dickhead like a lot of other people on this forum!

+cat

Makes use of every bit of swept height available:

https://photos.smugmug.com/20152017-...3ig1sma-XL.jpg

https://photos.smugmug.com/20152017-...kzzousf-XL.jpg

So much win in brakes and wheel stud fail. Any info on the upper ball joint?

Great to see more options out there to respond to the assortment of needs and preoccupations.

Having pad dimensions is really nice as I find most qualitative comparisons in pad size are done relative to a non-sport stock pad.

It would be really nice to also know the usable pad volume on each of these shapes to help everyone make the right trade-off for them.

As someone else asked, when will these StopTech kits, ST42 and STR42, be listed on websites for sale?

Not really. Those are good studs that came pre-installed in the fresh Centric hubs. I don't run spacers and thus have plenty of thread engagement with the 949Racing lugs. No need to change it. With as much as I've cut the car apart and rebuilt it, this may sound like a contradiction, but I am still a proponent of not f*cking with something if there isn't a good reason to.

The upper ball joint is V8R's rebuildable unit. Just installed so will be testing it soon.

That a nice swept height, thanks for the pictures. It might not hurt still to get a custom pad cut to get more pad material on the inner radius of the rotor. Wendy at Porterfield has been awesome to work with on projects like that, and not expensive either.

Interesting too how low the brake line connects, no issues with clearance I assume, but just something to note. The calipers are not universal left/right either it looks like.

Consider that the caliper uses abutment plates to locate the bottom corners of the pads, so you can't change the lower pad shape in the way you're envisioning.

The calipers are staggered piston sizes so definitely left/right specific.

Basic info and pricing uploaded.

Fair enough. I thought the consensus was to replace the studs for added insurance on track-driven cars. Looking forward to seeing results on the ball joints.

Details on IR sensors? Have been kind of looking into the best way to do this; it seems like most of the available IR sensors don't want to deal with brake rotor temperatures or maybe I've been looking in the wrong places.

It was a prototype kit put together by member Cyotani on these forums. Stand-alone data logging system that wrote to a SD card with four IR sensors in 3D printed cases. Mounted the sensors to the brake cooling ducts with a hole drilled in the duct for the sensor eye to point at the inner facing rotor surface. A little buggy since it was a proto but got some great data with it. There are production kits out there, they're just $$$

I am looking at kitbashing together something almost identical so was literally looking for what sensors were in the cases. ;) Is there a thread (nevermind think I found it, I'll just dig that up from the dead)

When I was in college, our FSAE team had a thermal imaging camera laying around that could log, so we taped it inside the nose of the car and did an autocross run. You don't end up with raw data as you would with a thermocouple, but it's another way to visualize it if the equipment is handy. If IB cooperates, you should see a couple autocross runs. This was done in 2009, so it looks like it was taken with the original TI calculator. Interesting bits start at 1:00.

Has anyone tried to fit these under 15x9 +36 TRM C3M?

Needs 5mm spacer and then it's gravy.

http://i425.photobucket.com/albums/p...5.jpg~original

http://i425.photobucket.com/albums/p...c.jpg~original

http://i425.photobucket.com/albums/p...z.jpg~original

That Stoptech caliper looks oh so sexy!

I'll second that.
I just need a car worthy and the spare pocket change.
Is there ever going to be a chance of an e-brake option on the rear?

I ran my first race with the new V8R 11.75 STR42's last month. I finally have the pedal I had always dreamed of in my Miata. I could not be happier with the setup! When combined with a 1" master and sport rears the modulation was perfect. Pad life is looking good too. I got about 5 sessions on the setup and still have a ton of pad left. Pad thickness is similar to Dynapro radial.

The new rears look great!

Oh yeah, I should probably post some pics :)

V8R/Stoptech STR21 rear caliper. Race only setup (no e-brake). Fits over Sport rotor, or in my case, V8R's 2pc rotors that are made to match factory Sport rotor dimensions.
Pads are PFC 11's to match the fronts.

https://photos.smugmug.com/20152017-...u0ygzku-XL.jpg

I've used a 1/4 turn ball valve with pretty good success as a parking brake

All NB Sport rear calipers, straight from the factory:

http://i425.photobucket.com/albums/p...h.jpg~original

oh, that's sexy

Front install completed. Four wheel kit installed, but this one is with the 11" rotor.. Now all I need is to reinstall the motor so I can actually use the brakes.

http://i425.photobucket.com/albums/p...5.jpg~original

http://i425.photobucket.com/albums/p...z.jpg~original

Nice pic of tiny 11" rotors. This is race prepped section where 11.75" rotors have proven to be the best for track usage. Now back to V8R/Stoptech awesome sauce.

Lol. Tough room.

Lmao, I was waiting for it

Some wheels won't fit the 11.75 without spacers so it's good to have the smaller option. And I certainly couldn't say 11.75 are proven over 11" when an optimized system is always the smallest possible setup that will work for the hardest conditions it will see. You want smaller and lighter whenever possible, agree? I know guys that change calipers and/or rotors on all four wheels because of a particular track where a larger rotor/caliper is not needed for thermal management.

9mm larger radial difference is noise level for thermal capacity and brake torque (if ring weights are the same) so it must come down to vane design & cooling efficiency if there is ANY difference between these two options.

Fixed my previous posts' images that had gone down.

Pics of the rear V8R/Stoptech STR21 kit to compliment the front:

https://photos.smugmug.com/20152017-...ztcpjlf-XL.jpg

https://photos.smugmug.com/20152017-...qctdpux-XL.jpg

https://photos.smugmug.com/20152017-...u0ygzku-XL.jpg

Maybe I'm wrong but my math is usually pretty good, wouldn't the difference in radius be closer to 9.5mm

Wouldn't it be more like 9.525mm? :giggle:

You are right - corrected in my post, but still not enough to impact brake torque or thermal mass significantly.

.