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  1. #1
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    Jun 2012
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    Are my brakes going to make it? 69 Olds on the track

    I came away from my first track day(Blackhawk Farms) with the impression my brakes we’re up to the task, but it was a bit misleading after I thought about it. It was 40 F all day, I was(am) a novice, wicked wheel hop led to much earlier and gentler braking, and I also had a soft-ish pedal from improper setup of GM metric calipers in the rear. So I’m trying to figure out if next spring is going to be filled with great 20 minute sessions or me lifting before the brake markers even start cause I have brake fade.

    My goal is to get to at least 6 HPDE sessions per year, eventually in the Intermediate class, and not be the fastest, but not dealing with squishy pedals near the end of the 20 minute sessions. I’ve come to respect the opinions here on PT over the past 7 years and would like advice, lessons earned, anectdotal…whatever.


    Here are what I see as my current options:

    1. My setup finally works after 7 years. Solid pedal, adjustable prop valve, and the pedal travel is about 2 inches (perfect for heal toe the way mine are setup), it’s definitely firm, but I’m a big dude so its oookay. Perhaps getting some cooling routed into the rotors will help me achieve my goals. There isn’t a lot of space at all and the opening to the rotor itself is small, so it’s definitely not ideal, but…maybe? Maybe also swap out to non drilled rotors to get some thermal mass back? This would let me spend significant money elsewhere and keep down the rotational mass of 13-14’’ brakes. I dunno.
    2. Or….everyone laughs at my current setup and tells me I need more juice. K, I’m open to this, but my head is fogged with all the options(C6, Z51, Wilwood Aero 6, Stoptech(I wish). I would need my pedal travel to stay roughly the same(Mc change), probably need ATS spindles, and would HOPE that I could keep my rear setup and just utilize more of the prop valve.


    I’m so happy to answer anything I’ve left out, just let me know and I’ll get the info. I think a lot of A body guys start out in my position because a good majority of us use the “disc brake conversion kit” from MPB or CPP or whoever just to get rid of the drums, but then we find this site and actually want to turn and stop harder than we ever thought possible.

    My Current Setup:
    2005 Corvette 9’’ dual diaphragm power booster.
    2005 Silverado MC: 1.33’’ bore Front
    Drop spindle from CPP(yeah I know….), upper/lower tall ball joints.
    11’’ cross drilled/slotted rotor from CPP.
    Wilwood D52 Aluminum 2 piston caliper. Piston Area per caliper:6.28in2
    Wilwood BP-20 pads

    Rear:
    Ford 9 with big Torino Ends.
    11.13’’ vented rotor
    Wilwood D154 caliper-no parking brake. Piston Area per caliper: 4.14 in2
    Wilwood BP-20 Pads

    Assumed/calculated performance:

    • 100 lbs input to 4:1 pedal ratio.
    • .45 coeff on the fronts and .4 on the back.
    • Front Tire: Nitto NT05 25.9’’ tall. (285/35R18)
    • Rear Tire: Hankook RS4 27.3’’ tall. (295/40R18)



    I come up with a total bake force at the road of 3619 lbs. I can share the excel sheet how I got here if it helps.

    Feel free to rip into me if my setup has no chance of surviving or if the stopping performance isn't even that good.

    1969 442 6.0L LQ9 T56
    Fab9 w/ custom 3 Link conversion
    FAYS2 Watts link
    Thanks to Mark at SC&C for his honesty and passion for the sport, and Ron Sutton for the wealth of knowledge that has helped shape so many of the cars on this site.

  2. #2
    Join Date
    Oct 2018
    Location
    San Jose, CA
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    460
    What size wheels ? You can run a 12” rotor with the D52 I believe. Probably takes a 16” wheel. Start there. As thick as possible. Ducts are great too. Do that. Make sure the fluid is good Motul 600 or something like that.

    1971 Camaro - 406 / T56
    2016 Camaro SS convertible
    2018 Colorado 4x4


  3. #3
    Join Date
    Jun 2012
    Location
    Chicago burbs
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    Quote Originally Posted by c4racer2 View Post
    What size wheels ? You can run a 12” rotor with the D52 I believe. Probably takes a 16” wheel. Start there. As thick as possible. Ducts are great too. Do that. Make sure the fluid is good Motul 600 or something like that.
    18 inch C6 Z06 rims. I wonder if a 12 inch rotor would be enough though? Not discounting it, just wondering if anyone has successful sessions with 12". That would save a lot of money for sure.

    I flushed the entire system with motul 600 prior to the track event, my buddy educated me well on track prep.

    1969 442 6.0L LQ9 T56
    Fab9 w/ custom 3 Link conversion
    FAYS2 Watts link
    Thanks to Mark at SC&C for his honesty and passion for the sport, and Ron Sutton for the wealth of knowledge that has helped shape so many of the cars on this site.

  4. #4
    Join Date
    May 2015
    Location
    Island Lake, IL
    Posts
    665
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    I would play with different brake pads. I see you have BP-20 but have you looked at the others that Wilwood offers? BP-30 and BP-40 are a step up in race type pads. You probably want something like that if you’re going to be doing road course like at Blackhawk.

    Wilwood D52 selection...
    https://www.wilwood.com/BrakePads/Br...st?padtype=D52

    Wilwood D154 selection...
    https://www.wilwood.com/BrakePads/Br...st?padtype=D52

  5. #5
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    Oct 2018
    Location
    San Jose, CA
    Posts
    460
    Yes agree. Try bigger rotors and more aggressive pads first. 1” more in rotor diameter makes a lot of difference.
    Rotors and pads are cheap.

    Plus once you start changing calipers it likely also means a MC change. Can of worms.

    Don’t worry about the rears for now. Fronts do 70% of the work.

    D52 are plenty capable of track work.

    I ran a 83 Camaro in a race class with NASA and our spec brakes were 1LE which is a PBR 2 piston caliper and 12” rotors and race pads and ducts and they worked great for a
    3400lb car w driver and fuel.

    My take is you are pretty close to a race capable setup. A few tweaks and it will be solid and not cost you an arm and a leg.

    Yes I have StopTech brakes on my PT car now because I can and not tied to a class spec. But if I had your car with that setup I would bump up the rotor size and get race pads throw on some ducts and see where you are at.
    1971 Camaro - 406 / T56
    2016 Camaro SS convertible
    2018 Colorado 4x4

  6. #6
    Join Date
    Sep 2010
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    Beach Park IL
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    My only concern is the ability of the relatively small rotor to shed the heat fast enough. I don't think 12" rotors will have a huge effect but if it is minimal effort to get them, there is no down side.

    In your position I would be religious about keeping fresh, high quality brake fluid in the car and get some temperature stickers and some rotor paint https://alconkits.com/support/instal...perature-paint

    At that point you have actual data for your car and can make decisions from there. If you want a winter project, cooling ducts to the front hubs won't hurt and you can always block them off.
    Donny

    Support your local hot rod shop!

  7. #7
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    What spindle do these cars need for upgrading to a 12” rotor?

    c4racer2, I assume you’re comparing to the F-Body 1LE upgrade.

  8. #8
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    Jun 2012
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    Quote Originally Posted by F-Body International View Post
    I would play with different brake pads. I see you have BP-20 but have you looked at the others that Wilwood offers? BP-30 and BP-40 are a step up in race type pads. You probably want something like that if you’re going to be doing road course like at Blackhawk.

    Wilwood D52 selection...
    https://www.wilwood.com/BrakePads/Br...st?padtype=D52

    Wilwood D154 selection...
    https://www.wilwood.com/BrakePads/Br...st?padtype=D52
    Good call. I thought the Bp20's I picked would be hellacious, but my buddy was making fun of me cause my "race pads" didn't even squeak on the drive up. For more stopping power I'll definitely check out the 30's or 40's but man-they are twice as expensive as the 20's.

    - - - Updated - - -

    Quote Originally Posted by c4racer2 View Post
    Yes agree. Try bigger rotors and more aggressive pads first. 1” more in rotor diameter makes a lot of difference.
    Rotors and pads are cheap.

    Plus once you start changing calipers it likely also means a MC change. Can of worms.

    Don’t worry about the rears for now. Fronts do 70% of the work.

    D52 are plenty capable of track work.

    I ran a 83 Camaro in a race class with NASA and our spec brakes were 1LE which is a PBR 2 piston caliper and 12” rotors and race pads and ducts and they worked great for a
    3400lb car w driver and fuel.

    My take is you are pretty close to a race capable setup. A few tweaks and it will be solid and not cost you an arm and a leg.

    Yes I have StopTech brakes on my PT car now because I can and not tied to a class spec. But if I had your car with that setup I would bump up the rotor size and get race pads throw on some ducts and see where you are at.
    Thanks C4, I did a lot of googling over on Chevelles.com and here, it looks like I can't just toss on the 12'' rotor without modifying the spindle and bracket(not a deal breaker), but it's definitely some effort. I have the ducting ready to go, but plumbing it into the rotor center seems near impossible with the big sway bar, spindle, brackets and 285's up front. Maybe this is an area where something is better than nothing...

    Oh great-I just checked out your Camaro thread. Those StopTechs...man oh man. I am one conflicted dude. Car looks like a great driver though and the changes you made seem to have paid off, congrats man.

    FYI I've been trying to "reply with multi-quote" all day long to avoid multiple posts, but it just won't do it properly.

    - - - Updated - - -

    Quote Originally Posted by dontlifttoshift View Post
    My only concern is the ability of the relatively small rotor to shed the heat fast enough. I don't think 12" rotors will have a huge effect but if it is minimal effort to get them, there is no down side.

    In your position I would be religious about keeping fresh, high quality brake fluid in the car and get some temperature stickers and some rotor paint https://alconkits.com/support/instal...perature-paint

    At that point you have actual data for your car and can make decisions from there. If you want a winter project, cooling ducts to the front hubs won't hurt and you can always block them off.
    you hit my main concern, shedding heat out of the 11''(or 12 if I can make it work). Well, I guess my main concern is that heat getting into the fluid and boiling, but yeah I think the rotor is a majority of that equation. If I put aside the obvious appeal of 14'' Stoptechs, it sounds like you guys don't think it's out of the realm that with cooling and constant fresh fluid that it be able to last for a 20 minute session. I hadn't thought of(or knew about) the rotor paint, thanks for the link, I'm definitely gonna grab some.

    soooo I'm thinking:
    1) get rid of the cross drilled rotors cause from what I read from Ron Sutton was the thermal mass makes more of a difference than whatever cooling effect they provide. See if I can get a thicker rotor that will bolt on, as well as check the possibility of a 12''.
    2) Route ducting to the center rotor.
    3) maybe fab up a caliper cooler that scoops air from under the lower control arm (I think I saw a Porsche that had something like this).

    I'm still certainly open to more thoughts/opinions or others' experience. I have about two months before I pick a direction. There's a possibility of a holiday bonus the company is rumoring which might just cover big brakes or airconditioning and projector headlights.

    1969 442 6.0L LQ9 T56
    Fab9 w/ custom 3 Link conversion
    FAYS2 Watts link
    Thanks to Mark at SC&C for his honesty and passion for the sport, and Ron Sutton for the wealth of knowledge that has helped shape so many of the cars on this site.

  9. #9
    Join Date
    Oct 2018
    Location
    San Jose, CA
    Posts
    460
    Thicker rotor not cross drilled for sure.
    Even if it’s 11” would help.

    Anyway 12” rotors with similar calipers and good ducting I know works well even for full on race sessions 20-30min with a similar weight car.

    But it’s also technique. You have to be hard hard hard on the brakes for as short a time as possible. It’s mostly a full threshold brake then off the brakes as soon as possible and carry as much momentum as the car will tolerate through a turn.

    A driver still learning will spend way too much time into the brakes because they are braking too early too often for too long and not hard enough. Small adjustments there can make a bigger impact than the equipment. Just sayin
    1971 Camaro - 406 / T56
    2016 Camaro SS convertible
    2018 Colorado 4x4

  10. #10
    Join Date
    Jun 2012
    Location
    Chicago burbs
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    I really appreciate the conversation guys, I'm usually just a lurker/commenter, but it's real nice to know that good help/advice is just a post away. C4, you make a good point, and as I described earlier, I'm very much a novice(there was some fresh SOD in my wheel wells from heading into Turn 6 a little hot to prove it), and my tendency to ride the brakes too long is probably going to be an issue until I get more seat time and learn to trust the car.

    I rear a paper published by Arne Lindgren, who as part of his thesis worked with Koenigsegg and performed brake cooling simulations on the Ragera. Theres some really cool ideas there, but several of the main takeaways were how easy it is for a tried and true idea to have no effect or sometimes even hurt cooling performance. It makes me doubt that I would be able to get a cooling system right through iteration and not leave more grass tracks in the process. Also a little curious that a company hasn't come up with a proven(or unproved) solution for brake cooling with the stock GM Short Spindle/11'' rotor combo.

    The paper is here for anyone interested:. http://www.diva-portal.se/smash/get/ diva2:938489/FULLTEXT01.pdf

    In the meantime, I'm going to go crawl around under the car and see if I can find a way to duct some legit cooling. I'm still open to more thoughts and advice, hope everyone has a nice turkey day.

    1969 442 6.0L LQ9 T56
    Fab9 w/ custom 3 Link conversion
    FAYS2 Watts link
    Thanks to Mark at SC&C for his honesty and passion for the sport, and Ron Sutton for the wealth of knowledge that has helped shape so many of the cars on this site.

  11. #11
    Join Date
    Oct 2018
    Location
    San Jose, CA
    Posts
    460
    I’ve always said spending time fixing the driver has double or triple the impact of upgrading the car.

    Even if you can’t get ducting get non cross drilled rotors - whatever size will work - and actual race pads - try the 30 next - and work on your driving technique. There is no substitute for seat time.
    1971 Camaro - 406 / T56
    2016 Camaro SS convertible
    2018 Colorado 4x4

  12. #12
    Join Date
    Mar 2007
    Location
    Florida
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    2,348
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    I made cooling for mine, pic below might give you ideas. Even just a duct aimed at the caliper would help.


  13. #13
    Join Date
    Nov 2014
    Location
    Alcoa, TN
    Posts
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    Quote Originally Posted by jetmech442 View Post
    I came away from my first track day(Blackhawk Farms) with the impression my brakes we’re up to the task, but it was a bit misleading after I thought about it. It was 40 F all day, I was(am) a novice, wicked wheel hop led to much earlier and gentler braking, and I also had a soft-ish pedal from improper setup of GM metric calipers in the rear. So I’m trying to figure out if next spring is going to be filled with great 20 minute sessions or me lifting before the brake markers even start cause I have brake fade.

    My goal is to get to at least 6 HPDE sessions per year, eventually in the Intermediate class, and not be the fastest, but not dealing with squishy pedals near the end of the 20 minute sessions. I’ve come to respect the opinions here on PT over the past 7 years and would like advice, lessons earned, anectdotal…whatever.


    Here are what I see as my current options:

    1. My setup finally works after 7 years. Solid pedal, adjustable prop valve, and the pedal travel is about 2 inches (perfect for heal toe the way mine are setup), it’s definitely firm, but I’m a big dude so its oookay. Perhaps getting some cooling routed into the rotors will help me achieve my goals. There isn’t a lot of space at all and the opening to the rotor itself is small, so it’s definitely not ideal, but…maybe? Maybe also swap out to non drilled rotors to get some thermal mass back? This would let me spend significant money elsewhere and keep down the rotational mass of 13-14’’ brakes. I dunno.
    2. Or….everyone laughs at my current setup and tells me I need more juice. K, I’m open to this, but my head is fogged with all the options(C6, Z51, Wilwood Aero 6, Stoptech(I wish). I would need my pedal travel to stay roughly the same(Mc change), probably need ATS spindles, and would HOPE that I could keep my rear setup and just utilize more of the prop valve.


    I’m so happy to answer anything I’ve left out, just let me know and I’ll get the info. I think a lot of A body guys start out in my position because a good majority of us use the “disc brake conversion kit” from MPB or CPP or whoever just to get rid of the drums, but then we find this site and actually want to turn and stop harder than we ever thought possible.

    My Current Setup:
    2005 Corvette 9’’ dual diaphragm power booster.
    2005 Silverado MC: 1.33’’ bore Front
    Drop spindle from CPP(yeah I know….), upper/lower tall ball joints.
    11’’ cross drilled/slotted rotor from CPP.
    Wilwood D52 Aluminum 2 piston caliper. Piston Area per caliper:6.28in2
    Wilwood BP-20 pads

    Rear:
    Ford 9 with big Torino Ends.
    11.13’’ vented rotor
    Wilwood D154 caliper-no parking brake. Piston Area per caliper: 4.14 in2
    Wilwood BP-20 Pads

    Assumed/calculated performance:

    • 100 lbs input to 4:1 pedal ratio.
    • .45 coeff on the fronts and .4 on the back.
    • Front Tire: Nitto NT05 25.9’’ tall. (285/35R18)
    • Rear Tire: Hankook RS4 27.3’’ tall. (295/40R18)



    I come up with a total bake force at the road of 3619 lbs. I can share the excel sheet how I got here if it helps.

    Feel free to rip into me if my setup has no chance of surviving or if the stopping performance isn't even that good.
    There's alot of info here. First, the setup seems great for a streetcar. If this is truly a racecar (be honest with yourself) a much more aggressive and heat tolerant pad, up front especially, is required as well as more static brake torque bias and rotor mass. I add this caveat because all too often many tend to mis-classify streetcars as racecars and vice versa. I drive to a race about once to twice per month for a couple hours and still, in regard to seat time, the car is 99.5%+ a streetcar. If this is similar to your use, BP30s or BP40s have no place on your car except for on track, they take too long to heat up and are garbage in the rain. Just put switch out the BP20s for race pads when you do a track day. Additionally, there are much better race pads than the BP series from Wilwood (polymatrix), and even other companies such as EBC blues and oranges.

    The coefficient of friction for the front and rear pads should be the same since they're the same compound. The pad area will be different. Also, using different tires front/rear is a little odd. I would try the next time you get tires to run the same compound. Takes out the guessing game regarding heat up and peakiness on track.

    As I'm sure you know, the front brakes do the majority of the work on our cars (~72% front bias @1.05G for my car). Using that knowledge we can clearly see that the brake torque bias should be largely on the front end. However, I see that you are using the same pad and rotor size for the front and rear. Even though the front/rear piston area ratio is decent, I can tell you're going to have to drop the rear pressure significantly compared to the front to obtain a 70-80% torque bias. You can use less pedal effort and thus pressure for the same brake torque by either increasing front rotor diameter or pad friction coefficient, or both.

    Are the rotors you are using cast as one piece with the hubs? This can really hurt the ability to get air inside the hub area of rotor. Moving to a separate hub and rotor assembly with a larger diameter can help in packaging a cooling plate and duct. A rotor with more mass can store more thermal energy as well as reject more thermal energy due to more surface area. Directionally vaned or vented rotors help this significantly due to the natural "fan" action as the rotor turns at track speeds. Cross drilled holes in rotors are there to prevent the buildup a gasses between the rotor and pad faces, same goes for slots. This gas is actually a fluid in these situations and creates a hydrodynamic wedge just like oil film in an engine crankshaft bearing. This significantly reduces friction, which is the opposite of what we want. Slots and holes also help with pad glazing. I don't like cross drilled holes because they tend to cause stress fractures in the rotor. Slotted is better.

    I run a 13" J55 C4 corvette rotor with a stock Camaro drum brake hub and D52 calipers. I also run a 7/8" bore Wilwood MC @ 6:1 pedal ratio and no booster, D154 Wilwoods out back on a 12.2" rotor. I made my own caliper mounts that utilize a factory GM short spindle like you have. It can be done quite easily. This all fits under a cast 17" wheel. I have attached pictures. I may be able to make you some of these brackets, email me.

    Ryan
    Attached Images Attached Images            
    Electrical/Mechanical Engineer
    1968 Camaro RS - Flat Black

  14. #14
    Join Date
    Jun 2012
    Location
    Chicago burbs
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    Quote Originally Posted by Sleeper68 View Post
    There's alot of info here. First, the setup seems great for a streetcar. If this is truly a racecar (be honest with yourself) a much more aggressive and heat tolerant pad, up front especially, is required as well as more static brake torque bias and rotor mass. I add this caveat because all too often many tend to mis-classify streetcars as racecars and vice versa. I drive to a race about once to twice per month for a couple hours and still, in regard to seat time, the car is 99.5%+ a streetcar. If this is similar to your use, BP30s or BP40s have no place on your car except for on track, they take too long to heat up and are garbage in the rain. Just put switch out the BP20s for race pads when you do a track day. Additionally, there are much better race pads than the BP series from Wilwood (polymatrix), and even other companies such as EBC blues and oranges.

    The coefficient of friction for the front and rear pads should be the same since they're the same compound. The pad area will be different. Also, using different tires front/rear is a little odd. I would try the next time you get tires to run the same compound. Takes out the guessing game regarding heat up and peakiness on track.

    As I'm sure you know, the front brakes do the majority of the work on our cars (~72% front bias @1.05G for my car). Using that knowledge we can clearly see that the brake torque bias should be largely on the front end. However, I see that you are using the same pad and rotor size for the front and rear. Even though the front/rear piston area ratio is decent, I can tell you're going to have to drop the rear pressure significantly compared to the front to obtain a 70-80% torque bias. You can use less pedal effort and thus pressure for the same brake torque by either increasing front rotor diameter or pad friction coefficient, or both.

    Are the rotors you are using cast as one piece with the hubs? This can really hurt the ability to get air inside the hub area of rotor. Moving to a separate hub and rotor assembly with a larger diameter can help in packaging a cooling plate and duct. A rotor with more mass can store more thermal energy as well as reject more thermal energy due to more surface area. Directionally vaned or vented rotors help this significantly due to the natural "fan" action as the rotor turns at track speeds. Cross drilled holes in rotors are there to prevent the buildup a gasses between the rotor and pad faces, same goes for slots. This gas is actually a fluid in these situations and creates a hydrodynamic wedge just like oil film in an engine crankshaft bearing. This significantly reduces friction, which is the opposite of what we want. Slots and holes also help with pad glazing. I don't like cross drilled holes because they tend to cause stress fractures in the rotor. Slotted is better.

    I run a 13" J55 C4 corvette rotor with a stock Camaro drum brake hub and D52 calipers. I also run a 7/8" bore Wilwood MC @ 6:1 pedal ratio and no booster, D154 Wilwoods out back on a 12.2" rotor. I made my own caliper mounts that utilize a factory GM short spindle like you have. It can be done quite easily. This all fits under a cast 17" wheel. I have attached pictures. I may be able to make you some of these brackets, email me.

    Ryan
    Thanks Ryan-I've been digesting the post over the holiday. I had half a response typed up before break and then finished it up this morning (mondays after vacay are sloooow).

    Definitely street car, but when I get on track I want the car to be confident in the braking zones-not the fastest, but predictable. HPDE events, 20 minute sessions, nothing crazy. It's a big deal for me to take a Saturday or full weekend away from the family/responsibilities, and since it's really the only time I get to open up the car and explore limits I want it be dependable.

    I thought the BP-20's were race pad lol, I swapped them in only for the track and use my EBC red stuffs for the street. I'll definitely look at the polymatrix line for track duty. After looking at the wildwood CoF charts, I can see there is much to be gained from a legit race pad.
    I had used a smaller CoF value in the rear(for calculations) because I figured the rears would run less hot due to the bias. I had also seen some posts by Ron Sutton that confirmed this strategy. Although, looking at the BP-30’s, there is very little change in CoF across the temp range so I can see that the same CoF is appropriate.

    Yes, the bias is all out of whack. I had some wicked wheel hop (also a combination of excessive anti-squat I think). I now have a prop valve to fine tune, but I see your point in just shifting the forces to the front with better pads or more torque from larger diameter rotors.
    My current setup is the cast CPP spindle(steering arms and brake bracket cast in place) and uses the one piece hubs. So I ‘d definitely need a new spindle.

    You just opened up an awesome pathway though with the J55 brakes. I’ve spent a few hours now looking into it, what a great way to get the thermal mass I’m looking for but keep my Wilwood D52 calipers. This would save a lot of time and especially money since the only wildwood calipers I can find with similar piston area(TC6 calipers) are over 1k for the pair. I’m going to look into this deeper, thanks for the suggestion. I'm sure I'll have more questions, but want to read up and develop a plan.

    1969 442 6.0L LQ9 T56
    Fab9 w/ custom 3 Link conversion
    FAYS2 Watts link
    Thanks to Mark at SC&C for his honesty and passion for the sport, and Ron Sutton for the wealth of knowledge that has helped shape so many of the cars on this site.

  15. #15
    Join Date
    Oct 2018
    Location
    San Jose, CA
    Posts
    460
    Not exactly a bolt on. What are your fab skills like?

    A Kore3 hub would fit your existing spindles and accept a C5/6 13” rotor but would also require a custom bracket to mount the D52 calipers. Talk to Tobin about that option maybe he could help put something together to leverage existing spindles and calipers.
    1971 Camaro - 406 / T56
    2016 Camaro SS convertible
    2018 Colorado 4x4

  16. #16
    Join Date
    Nov 2014
    Location
    Alcoa, TN
    Posts
    51
    Country Flag: United States
    Quote Originally Posted by jetmech442 View Post
    Thanks Ryan-I've been digesting the post over the holiday. I had half a response typed up before break and then finished it up this morning (mondays after vacay are sloooow).

    Definitely street car, but when I get on track I want the car to be confident in the braking zones-not the fastest, but predictable. HPDE events, 20 minute sessions, nothing crazy. It's a big deal for me to take a Saturday or full weekend away from the family/responsibilities, and since it's really the only time I get to open up the car and explore limits I want it be dependable.

    I thought the BP-20's were race pad lol, I swapped them in only for the track and use my EBC red stuffs for the street. I'll definitely look at the polymatrix line for track duty. After looking at the wildwood CoF charts, I can see there is much to be gained from a legit race pad.
    I had used a smaller CoF value in the rear(for calculations) because I figured the rears would run less hot due to the bias. I had also seen some posts by Ron Sutton that confirmed this strategy. Although, looking at the BP-30’s, there is very little change in CoF across the temp range so I can see that the same CoF is appropriate.

    Yes, the bias is all out of whack. I had some wicked wheel hop (also a combination of excessive anti-squat I think). I now have a prop valve to fine tune, but I see your point in just shifting the forces to the front with better pads or more torque from larger diameter rotors.
    My current setup is the cast CPP spindle(steering arms and brake bracket cast in place) and uses the one piece hubs. So I ‘d definitely need a new spindle.

    You just opened up an awesome pathway though with the J55 brakes. I’ve spent a few hours now looking into it, what a great way to get the thermal mass I’m looking for but keep my Wilwood D52 calipers. This would save a lot of time and especially money since the only wildwood calipers I can find with similar piston area(TC6 calipers) are over 1k for the pair. I’m going to look into this deeper, thanks for the suggestion. I'm sure I'll have more questions, but want to read up and develop a plan.
    Do you have your old GM short spindles? The brackets I made will work with them if you use a Camaro/Nova drum hub. The a body drum hubs may be the same as the Camaro/Nova hubs. If so, all you would need is the J55 rotors, old spindles, old drum hubs, new hardware, and a ~0.470" spacer/thick washer.

    I don't think Tobin's stuff will work with his current spindles since the brake brackets are cast in. It is likely the GM spindles are stronger than the cpp spindles since the GM spindles are forged steel and employed a differential heat treating to allow them to flex instead of breaking.
    Electrical/Mechanical Engineer
    1968 Camaro RS - Flat Black

  17. #17
    Join Date
    Oct 2018
    Location
    San Jose, CA
    Posts
    460
    Oh ya. Missed that. Thought he had stock spindles. Does the drum hub need any modifications ? Other than removing the brake guts ? I haven’t heard of doing this. What are the drawbacks ? Does it use conventional bearings ? Are they big enough to be strong ?
    1971 Camaro - 406 / T56
    2016 Camaro SS convertible
    2018 Colorado 4x4

  18. #18
    Join Date
    Nov 2014
    Location
    Alcoa, TN
    Posts
    51
    Country Flag: United States
    Quote Originally Posted by c4racer2 View Post
    Oh ya. Missed that. Thought he had stock spindles. Does the drum hub need any modifications ? Other than removing the brake guts ? I haven’t heard of doing this. What are the drawbacks ? Does it use conventional bearings ? Are they big enough to be strong ?
    I had to turn down the OD of the hub about 0.200" so that the hub would fit inside the rotor hat. I also pressed out the old 7/16" wheel studs, tapped the stud holes in 1/2"-20, and installed ARP 3" wheel studs. I also replaced the wheel bearings and races. Other than that, they are factory.

    This is what the hubs look like: https://www.heartbeatcitycamaro.com/...%26-Dust-Caps/

    The hubs use the same bearings and races as the OEM disk brake hubs. Factory bearings are not the strongest but they are decent. If you're pushing the car hard every weekend on race rubber I would inspect the bearings every 3-6 months are re-grease. They probably should be replaced every 1-2 seasons. The main "strength" issue is the cantilevered, GM spindle. It is made of forged steel, but it leaves a lot to be desired in terms of strength.

    That's why I went to the Chassisworks short spindle. It is a 1.5" taller version of the GM short spindle, the cantilevered spindle is made on 4130 chromoly, and the main body "upright" is made of 7075-T651 aluminum. Very nice units, and cost less than the ATS AFX spindles. Chassisworks also makes 7075-T651 "Z/28" style steering arms for 1st gen F/X bodies.

    Here's the links:

    https://www.cachassisworks.com/p-291...ck-height.aspx
    https://www.cachassisworks.com/p-295...-aluminum.aspx

    There is no "removing the brake guts" per se. The hub can be removed immediately after removing the drum and spindle nut.
    Electrical/Mechanical Engineer
    1968 Camaro RS - Flat Black

  19. #19
    Join Date
    Jun 2012
    Location
    Chicago burbs
    Posts
    133
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    Quote Originally Posted by c4racer2 View Post
    Not exactly a bolt on. What are your fab skills like?

    A Kore3 hub would fit your existing spindles and accept a C5/6 13” rotor but would also require a custom bracket to mount the D52 calipers. Talk to Tobin about that option maybe he could help put something together to leverage existing spindles and calipers.
    Man, you guys are great!

    I'm good with Fab, anything outside my skill or equipment I'm happy to enlist professionals. But I'm goo designing, waterjetting/CNC online..etc.

    My current setup has tall upper and lower ball joints from Savitske, which I would transfer over to whatever new spindles I get(as Ryan pointed out the cast ones are essentially useless outside of that exact setup from CPP.

    I also have the D52 calipers for a rotor width of 1.1''. I'm not sure if there is anyway to keep those if I end up going to a thicker rotor, I'm open to suggestions here. The D52 has nearly double the piston area of the C6 and most multipiston wilwood calipers, so I'd like to try real hard to keep them, especially since my MC and everything else is working in harmony..ish.

    So far, I see my current options as this:
    J55 C4 setup with D52's
    One Piece Forged Steel 2'' drop spindle, Chassisworks: 336 pr
    Stock steering arms: 68pr
    Drum hubs: 99pr
    Stoptech J55 (1996) Corvette 13’’ rotor(126.62047SR), nominal thickness 1.1: 236pr
    Need to fabricate bracket to mount D52 caliper. 100 bucks?
    Total: 900$

    Kore-3, z51 approach with stock D52
    GM SHORT-SPINDLE, ø340mm C6 Z51
    One Piece Forged Steel 2'' drop spindle, Chassisworks: 336 pr
    Stock steering arms: 68pr
    Kore3 billet Hubs:399 pr
    DBA slotted rotor 13.4 x 1.25: 311 pr
    Need to fabricate bracket to mount D52 calipers.
    Also need D52 calipers for 1.25 rotor thickness. 364pr
    Total:1578$

    I think both routes get me into a 13'' rotor without breaking the bank. given these two routes, do you think the ~700 bucks is worth it for the kore3 setup?

    1969 442 6.0L LQ9 T56
    Fab9 w/ custom 3 Link conversion
    FAYS2 Watts link
    Thanks to Mark at SC&C for his honesty and passion for the sport, and Ron Sutton for the wealth of knowledge that has helped shape so many of the cars on this site.

  20. #20
    Join Date
    Nov 2014
    Location
    Alcoa, TN
    Posts
    51
    Country Flag: United States
    Quote Originally Posted by jetmech442 View Post
    Man, you guys are great!
    So far, I see my current options as this:
    J55 C4 setup with D52's
    One Piece Forged Steel 2'' drop spindle, Chassisworks: 336 pr
    Stock steering arms: 68pr
    Drum hubs: 99pr
    Stoptech J55 (1996) Corvette 13’’ rotor(126.62047SR), nominal thickness 1.1: 236pr
    Need to fabricate bracket to mount D52 caliper. 100 bucks?
    Total: 900$

    Kore-3, z51 approach with stock D52
    GM SHORT-SPINDLE, ø340mm C6 Z51
    One Piece Forged Steel 2'' drop spindle, Chassisworks: 336 pr
    Stock steering arms: 68pr
    Kore3 billet Hubs:399 pr
    DBA slotted rotor 13.4 x 1.25: 311 pr
    Need to fabricate bracket to mount D52 calipers.
    Also need D52 calipers for 1.25 rotor thickness. 364pr
    Total:1578$

    I think both routes get me into a 13'' rotor without breaking the bank. given these two routes, do you think the ~700 bucks is worth it for the kore3 setup?
    You can get C4 J55 Vette rotors from O'Reilly auto parts for $50 each. No need to get stoptech.


    https://www.oreillyauto.com/detail/b...ke+rotor&pos=9

    https://www.oreillyauto.com/detail/b...ke+rotor&pos=8
    Electrical/Mechanical Engineer
    1968 Camaro RS - Flat Black

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