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Cortex Floating Axle and Rear Brakes

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cholmes1

400lb Gorilla
350
216
Denver, CO
First I need to thank Paul @PAEracing for all of his assistance in April 2020 in discussing Brembo brake options with me. Paul's knowledge and customer service are outstanding and I would highly recommend him and his team to anyone looking for honest advice. I had originally approached Paul about the XB105 system utilized in the 302S and current Grand-Am touring cars for my '13 302LS. Regrettably, my knowledge of these systems was (and remains) limited and I was unaware of the noise dedicated race calipers generate (no anti-rattle clips, floating rotors, etc). Since my car only sees the track for the occasional solo sprint events (~ 1 / year) and is 99% street/show the rattle would have driven me nuts. This upgrade is purely to push my car forward in terms of potential capability, which I will never approach

I was originally going to stay FRPP with the GT350 setup but having Paul explain the significant weight difference between OEM and Brembo GT-S/Race while also following Full Tilt Boogie's testing the GT350 rears on the S197 platform and finding out they were incompatible in all situations, the GT350 calipers were a non-starter. Following these exchanges with Paul, I decided to go with the Brembo GT-S M6 setup upfront. So now that I plan on using the Brembo GT-S M6 upfront the search begins to find a suitable match in the rear.

* This is where I may lose the interest of some TMO members *

Being this brake swap is far less for need and more for 'potential' and aesthetics I feel I am hitting a bit of a wall. In speaking with Filip at Cortex and others I am aware the rear brakes really do not require modification beyond the disc and the pad for success on the track. To support, he stated that in GT4 testing Cortex found that anything beyond a 328x28 system was overkill and just adding weight. Hence why they offer the Brembo XA3 calipers on a 313x25 rotor to pair with their floating axle. That said, the Brembo XA3 is similar to the XB105 in that it is a true race caliper and would not only have similar noise issues but would be far beyond my need and not aesthetically match the GT-S M6 caliper. While my planned system may not be OEM at any level, finding a rear Brembo caliper that can match the M6 should allow me to have the improved braking I am looking for while also having the appearance of a matched system like you would find in higher-end OEM setups.

In research, it appears the GT-S M4 caliper is the perfect mate and has a broad variety of rear brake system options. The challenge now becomes determining how such a system could be installed in the rear. With the '13 302 having a solid rear axle nearly all aftermarket options are not compatible. After FTB's GT350 testing, they recommended I reach out to Cortex to inquire about their floating axle as it allows for a larger variety of rear brake options to be applicable while also allowing camber to be applied. Another issue encountered is that because my car is primarily road driven and for car shows, few of the Brembo GT-S options allow for a parking brake. Fortunately, Wilwood appears to offer a standalone electric parking brake kit that can be mounted anywhere on the caliper.

My questions for the TMO family are...

1) Does anyone know if the M4 caliper with 345 - 380mm disc can mount to the Cortex floating axle in the S197? I am unable to find the depth of the rotor hat. I would assume yes if the XA3 can, but my knowledge is limited

2) Has anyone used the Wilwood electric brake kit? I did find one M4 option that does include a mechanical brake (from the 2020 Mustang GT) but I am not certain how easily or if it could be connected to the existing handbrake.

3) Given my limited knowledge, does it appear I am missing anything with this potential setup (F: M6 w Ferodo FM1000 pads on a TY3 disc - R: Cortex Floating Axle using the Brembo M4 w Ferodo FM1000 pads on a TY3 disc and Wilwood EPB or Brembo mechanical PB)

I look forward to learning more from the collective knowledge of our group
 
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The street rod guys around me use a brake that mounts on the driveshaft, unfortunately, that would mean fabricating your own drive shaft, most competition cars don't use a parking brake, or they use the stock brake as I do_ in order to assist in loading the car on the trailer.. You might try something called a Hurst Line Lock which is used in drag racing for staging the car, it keeps pressure in the line, however, it should not be used full time as a parking brake. You are still stuck just dropping the car in gear to hold it steady.
 

cholmes1

400lb Gorilla
350
216
Denver, CO
Thank you. I am familiar with line locks and would not see that as a viable alternative. While it does not happen often, I do sometimes have to park on inclines and relying solely on the transmission would not be ideal or safe, and maintaing max static pressure in the lines would also likely have unpleasant consequences. I will continue searching until a solution is found (more research on Wilwoods kit is needed and if the 2020 GT system would work). The F/R setup will be purchased as a whole so if any component is missing then I will simply have to wait until the technology catches up.
 
While I am certainly not an authority on any subject that pertains to S197 mechanicals, I was pursuing the same rear brake upgrade that you are after purchasing an AP 6-piston race set-up. Then I spoke with Rick at Cortex and he set me straight.
As Rick explained it, the solid axle of the S197 has so much flex/movement that when they tried mounting a larger, fixed multi-piston caliper, the rotor kept making contact with the caliper/pads from flex and destroyed things. So a sliding caliper was the only option. Rick said that's part of the reason they moved to a floating, cambered rear....so they could now fit a proper fixed caliper. So you need to spend 8-10K on a cambered rear to get the rear caliper upgrade. Way above my pay grade.
 

cholmes1

400lb Gorilla
350
216
Denver, CO
Thank you, @docs302. Yes, the Cortex Floating Axle is required and will be purchased. I apologize if that was unclear in the original posting. I will be buying the Cortex piece not just for the brake mounting (which is great) but also the other benefits it offers.
 
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AJ wrote a piece on this axle, it's not a world beater all by itself, but it does allow you to make other beneficial changes to the car, that overall, will improve things. Don't think you can just bolt it on and you will magically drop 2 seconds per lap.
 
6,363
8,190
Found it..

No rules on suspension sounds like it will be a very expensive path.

1. No experience with the SLA. Never allowed to use it.
2. The cambered rear axle. Another magic 2 seconds a lap... This was going to be the end all-be all. Again we were told it was worth so much in back to back testing. When we first used it, it wasn't. More like a couple hundredths of a second slower. But it showed promise as we were sent the wrong hubs a week before the next race, and couldn't get the proper degree hubs in time. After we got it properly setup with the correct camber, I'd say on certain tracks its probably worth a half of a second on a car that works well already. On cars that don't work well it may fix some things or it may screw things up further.

The real benefit was running fixed calipers on the rear. Much better and consistent brake pedal.
 

Fabman

Dances with Racecars
6,519
8,156
Exp. Type
W2W Racing
Exp. Level
20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
I ordered the rear end with the stock caliper setup. I kept hearing how the stock caliper was all that was needed and it saved me a couple grand….I hope I don’t regret this.
 

cholmes1

400lb Gorilla
350
216
Denver, CO
Thank you both for the feedback. Given how seldom I track the car I view the Cortex axle in the same way I look at my ‘beyond my skill’ golf clubs. I can never blame the equipment

Given his connection, I am curious if @ArizonaBOSS has any feedback on the Cortex axle and the brake options it allows

@Fabman how long have you been running the Cortex axle. Any insights thoughts of upgrading your rear brake setup?
 

Fabman

Dances with Racecars
6,519
8,156
Exp. Type
W2W Racing
Exp. Level
20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
Thank you both for the feedback. Given how seldom I track the car I view the Cortex axle in the same way I look at my ‘beyond my skill’ golf clubs. I can never blame the equipment

Given his connection, I am curious if @ArizonaBOSS has any feedback on the Cortex axle and the brake options it allows

@Fabman how long have you been running the Cortex axle. Any insights thoughts of upgrading your rear brake setup?
Mine is still on order, I have been running the stock axel.
 

Ron McCall

Pantera1889
I would not run anything on a competition road race car that said
" Wilwood"
Would you mine elaborating on that statement? I know that most of their products are geared towards the street car crowd and have caused issues when used in a competition setting but I believe that they make better stuff as well.
Any experience with their "better" stuff?
I would think that something like this would be comparable to some of the "lower end " AP ,Brenbo or StopTech offerings? I know that the higher end Brembo, AP, PFC etc.. are much better but what about the more budget friendly offerings?

Ron
 
You guys are making me think evil thoughts about hitting buy now on the cortex site on one of these. I fight brake issues and my car kills the outside of the rear tires.

DaveW
 
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Would you mine elaborating on that statement? I know that most of their products are geared towards the street car crowd and have caused issues when used in a competition setting but I believe that they make better stuff as well.
Any experience with their "better" stuff?
I would think that something like this would be comparable to some of the "lower end " AP ,Brenbo or StopTech offerings? I know that the higher end Brembo, AP, PFC etc.. are much better but what about the more budget friendly offerings?

Ron
The teams I've run with have competed with misc cars using the Wilwood brand, in almost every case braking seemed to be better on the vehicles that I've crewed for, which used Brembos predominately. After spending a year on a Gt cup car a few years ago, (and an older Mustang Gt that I ran in NASA) I can tell you that PFC aren't exactly on my "favored brake list" either. Basically, Brembos are the gold standard, so why even entertain anything else?
With regards to the local stock car guys, they have to use either over the counter stock type brakes or, the Outlaw brand, although it does seem that Wilwoods have more of a market share on the short tracks.
 

ArizonaBOSS

Because racecar.
Moderator
8,730
2,734
Arizona, USA
Thank you both for the feedback. Given how seldom I track the car I view the Cortex axle in the same way I look at my ‘beyond my skill’ golf clubs. I can never blame the equipment

Given his connection, I am curious if @ArizonaBOSS has any feedback on the Cortex axle and the brake options it allows

@Fabman how long have you been running the Cortex axle. Any insights thoughts of upgrading your rear brake setup?
I am running the Ford OEM brake calipers on the cambered rear. That is the "default" config for the Cambered Axle, it does come with larger, two-piece Girodisc rotors (required because of the offset location of the caliper w/ the new axle), absolutely no problem running this setup in competition.

IMO I would probably only get the fixed calipers if you were planning on doing endurance racing--for more/thicker pad options, as well as for survivability (no dust boots etc like factory calipers). I don't think the extra cost for the fixed setup is justified, otherwise.

FWIW the Cambered Axle was worth about 1.5s on a short track, for me. I have a write up on it buried in my build thread, with data. AJ and Phoenix are pushing these cars harder than I am, so Blacksheep's comments above are valid. But once you get the car set up correctly, and can adapt your driving style to take advantage of your new mechanical goodies, they will pay dividends.
 

Fabman

Dances with Racecars
6,519
8,156
Exp. Type
W2W Racing
Exp. Level
20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
I am running the Ford OEM brake calipers on the cambered rear. That is the "default" config for the Cambered Axle, it does come with larger, two-piece Girodisc rotors (required because of the offset location of the caliper w/ the new axle), absolutely no problem running this setup in competition.

IMO I would probably only get the fixed calipers if you were planning on doing endurance racing--for more/thicker pad options, as well as for survivability (no dust boots etc like factory calipers). I don't think the extra cost for the fixed setup is justified, otherwise.

FWIW the Cambered Axle was worth about 1.5s on a short track, for me. I have a write up on it buried in my build thread, with data. AJ and Phoenix are pushing these cars harder than I am, so Blacksheep's comments above are valid. But once you get the car set up correctly, and can adapt your driving style to take advantage of your new mechanical goodies, they will pay dividends.
Good to hear. I could use a second or two....and that the stock brakes are fine.
 

cholmes1

400lb Gorilla
350
216
Denver, CO
I am running the Ford OEM brake calipers on the cambered rear. That is the "default" config for the Cambered Axle, it does come with larger, two-piece Girodisc rotors (required because of the offset location of the caliper w/ the new axle), absolutely no problem running this setup in competition.

IMO I would probably only get the fixed calipers if you were planning on doing endurance racing--for more/thicker pad options, as well as for survivability (no dust boots etc like factory calipers). I don't think the extra cost for the fixed setup is justified, otherwise.

Thank you for your feedback. FWIW my interest in the rear Brembo set up noted above is for aesthetics and potential. My car only sees the track maybe once a year for a solo sprint event around a dedicated track. To date the car still has less than 4500 mi and has been on a track once at Pikes Peak.

My question with the rear @cortexracing axle is if it would accept the Brembo M4 caliper w mechanical parking brake from the 2020 GT or if a different kit all together is needed? The endurance guys are likely running the Brembo XA3 caliper as allows for larger pads and is a dedicated race unit to dissipate heat rapidly.
 
As mentioned above, a fixed caliper will not work on a stock axle. I have measured 3/16" displacement of the rotor due to axle shaft flex. I know this because my rotor has "clearanced" it's self into my caliper bracket. Larger diameter rotors just exacerbate the issue. This amount of flex would cause massive pad knock-back and ultimately caliper failure as a result. A Cortex axle would be beneficial for both allowing an endurance caliper/pad set-up as well as correcting tire wear. My rear tires, regardless if they are Pirelli or Michelin slicks, wear much faster on the outside shoulders. It's easy to see why, I have track photos from corners where it shows the tires 2 degrees positive camber due to axle flex. That being said, at $7K+, I'll continue putting up with these issues...
 

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