Page 2 of 3 FirstFirst 1 2 3 LastLast
Results 21 to 40 of 44

Thread: D52 pad coeff.

  1. #21
    Join Date
    Nov 2012
    Location
    Sacramento, CA
    Posts
    2,338
    Country Flag: United States

    Default

    Woody,

    Before you redid your brake system ... and the pedal was going almost to the floor ... was that with an older, used master cylinder? Also, is the master cylinder in the car now ... new or used?



    I ask, because as a master cylinder wears over time, it produces less pressure, even though there is no leak. The brake fluid is getting past the M/C piston seals, back into the reservoir. This is when & why many people replace worn out M/C's.


  2. #22
    Join Date
    Mar 2005
    Location
    Walton, NY
    Posts
    660

    Default

    Quote Originally Posted by Ron Sutton View Post
    Woody,

    Before you redid your brake system ... and the pedal was going almost to the floor ... was that with an older, used master cylinder? Also, is the master cylinder in the car now ... new or used?

    I ask, because as a master cylinder wears over time, it produces less pressure, even though there is no leak. The brake fluid is getting past the M/C piston seals, back into the reservoir. This is when & why many people replace worn out M/C's.
    The old master cylinder with stock brakes was fine - pedal and stopping power.

    During my brake "upgrade" I changed the stock 11" front rotors to 12" 1LE and changed the drums to 11.6" Blazer disc with a brand new 79 Vette 1.125 disc/disc MC with HPS pads and it felt soft and the stopping power was reduced. Chased my tail to remove air with no results. Converted to manual brakes with a brand new 70 Vette 1" MC and all braided hoses and the pedal was still soft and the travel was almost on the floor. Swapped the stock D52 front calipers for 2.38 Wilwood GMIIIs and it was still soft, but it reduced travel. Tried re-bedding the pads...no change. Tried a used aluminum Mopar MC with no change. That's where I'm at now.

    I know it still sounds like air in the system, but I have bled and bled and bled and even had two different shops bleed it with the same results: no air. And my brake pressure gauge does not read any higher when pumping the brakes than a single step. MC's pass the lock test with the ports plugged. When my car comes out of storage I plan on trying new pads as an easy test. Many people on those Bimmer & Audi forums have complained about pedal feel with the HPS pads and at this point I'm willing to try it. If that fixes the problem I will be overjoyed to chuck them in the dumpster, and at the same time I'll be annoyed they were the cause of all this aggravation...haha I never would have suspected my new "High Performance Street" pads would have been the cause of my brake issues, but I'll be happy regardless if I get it sorted out.

  3. #23
    Join Date
    Nov 2012
    Location
    Sacramento, CA
    Posts
    2,338
    Country Flag: United States

    Default

    Good, detailed info Woody. That helps a little to see where the problem is not, by process of elimination.

    I think trying to compare your car & brakes to the C5 is misleading. Your car originally had Large GM calipers with 2 15/16" front pistons & a 15/16" M/C with 11" rotors and stopped good. (you also the help of a power booster)

    If we use the same CF# we have using for HPS pads, we come up with front braking torque number of 1679#.

    Remember earlier in this thread, I posted the calculated brake torque #s for your current brake set up to be:
    Total 1714#
    Front 1076# 62.8%
    Rear 638# 38.2%

    When you went from Large GM calipers with 2 15/16" front pistons & a 15/16" M/C with 11" rotors ... to the Wilwood calipers with 2.375" pistons & a 1" M/C bore with 12" rotors ... you reduced the braking torque from 1679# to 1076#. That is a 36% decrease in braking torque (assuming same pads) in the front of the car, where the majority of braking is. That's a huge reduction.

    The best solution would be to install brake calipers with larger pistons and/or a master cylinder with slightly smaller bore. Then you could still run a longer wearing street type brake pad and have great performing brakes.

    If you you don't want to replace the Calipers and/or M/C ... and want to fix it with a pad compound change only ... you'll need to step up to a pad compound with a CF# around .54 to .57. These are racing brake pads. They will cost more & wear quicker. Wilwood B or BP-30 compounds would achieve this. Also the Hawk Black compound would too.

    Happy testing !

  4. #24
    Join Date
    Mar 2005
    Location
    Walton, NY
    Posts
    660

    Default

    Thanks for the continued interest in the topic, Ron. I've been fighting to get to the bottom of this for a couple years! Originally I hadn't even considered larger calipers...and I'm still a little sketchy on that due to my mushy pedal. The pedal is not on the floor now, but with bigger piston calipers it might be. It'd would be nice to borrow a pair of D52s for the front to try. (Mine ended up on my dad's 63 Impala and that car has since been sold.)

    Here are a couple of things that make me doubt that changing the calipers would remedy the problem, though. The stock master was 1.125, same bore as the Corvette disc/disc unit I installed. And even with the stock booster, stock bore size master cylinder, stock front calipers, and 1" larger front rotors...the pedal was still soft and braking power was reduced. It was after this that I converted to manual brakes with a smaller bore master cylinder. So the only real changes from adequate stock brakes to poor "upgraded" brakes was the larger front rotor, Hawk pads and rear disc conversion.

    When I finally do get the situation sorted out I will post back with the cause and remedy.

  5. #25
    Join Date
    Nov 2012
    Location
    Sacramento, CA
    Posts
    2,338
    Country Flag: United States

    Default

    Ok. Best wishes !

  6. #26
    Join Date
    Sep 2008
    Location
    JACKSONVILLE, FLORIDA
    Posts
    568
    Country Flag: United States

    Default

    Thanks Ron. You are a brake knowledge guru!

    Would you mind if I ran my brake setup by you and see if you agree with what I have?
    Craig Scholl
    CJD Automotive, LLC
    Jacksonville, Florida
    904-400-1802
    www.cjdautomotive.com

    "I own a Mopar, I already know it won't be in stock, won't ship tomorrow, and won't fit without modification."

  7. #27
    Join Date
    Nov 2012
    Location
    Sacramento, CA
    Posts
    2,338
    Country Flag: United States

    Default

    Hi Craig,

    Thanks for the kudos. I'm not necessarily a "brake guy" ... but more a complete race car designer/builder with years of experience at winning races. I wouldn't mind helping you at all. Please include the following info for the front & rear brakes ...

    1. Caliper model, with # & diameter of pistons per caliper
    2. Bore/piston size in master cylinder
    3. Rotor diameter (true #, not advertised) * Most 12" rotors are 11.75 or 11.875. Most 13" are 12.88"
    4. Brake pad you have planned to use

    This will give us a place to start out conversation.
    ** Knowing the pedal ratio is important in completely custom built applications. But if you are swapping brakes in a car & keeping the same pedal, we can just use a constant #.

  8. #28
    Join Date
    Sep 2008
    Location
    JACKSONVILLE, FLORIDA
    Posts
    568
    Country Flag: United States

    Default

    Quote Originally Posted by Ron Sutton View Post
    Hi Craig,

    Thanks for the kudos. I'm not necessarily a "brake guy" ... but more a complete race car designer/builder with years of experience at winning races. I wouldn't mind helping you at all. Please include the following info for the front & rear brakes ...

    1. Caliper model, with # & diameter of pistons per caliper
    2. Bore/piston size in master cylinder
    3. Rotor diameter (true #, not advertised) * Most 12" rotors are 11.75 or 11.875. Most 13" are 12.88"
    4. Brake pad you have planned to use

    This will give us a place to start out conversation.
    ** Knowing the pedal ratio is important in completely custom built applications. But if you are swapping brakes in a car & keeping the same pedal, we can just use a constant #.
    Thanks Ron,

    I'm using Wilwood SL6 calipers in the front. 4.04 piston area w/ 1.62, 1.12, and 1.12. The rotors are a true 14". SL4 in rear. 1.96 piston area w/ dual 1.12. The rotors are a true 13". I'm using a Wilwood pedal assy with a 6.25:1 w/ no assist. My M/C are 3/4", 13/16", and 7/8" for clutch and MC. I wanted to see what bore you thought would be appropriate for what (and to see how far i'm off!). I'm looking at A, B, or BP-30 pads.
    Craig Scholl
    CJD Automotive, LLC
    Jacksonville, Florida
    904-400-1802
    www.cjdautomotive.com

    "I own a Mopar, I already know it won't be in stock, won't ship tomorrow, and won't fit without modification."

  9. #29
    Join Date
    Nov 2012
    Location
    Sacramento, CA
    Posts
    2,338
    Country Flag: United States

    Default

    Nice Craig ! This hot rod is going to have a lot of braking. Here are the #'s

    If you use the BP-30 pads (more on pads later) and put the 7/8" M/C on front & the 13/16" M/C on the rear:

    Total 3566#
    Front 2347# 65.8%
    Rear 1219# 34.2%

    That's looking sweet for a baseline. Most stock street car brake systems have 2200-2800# braking force. You are at 3566#, now into race brake system territory (3000-5500#). This layout of M/C sizes provides you with a good baseline ... near 65/35 brake balance front to rear. (use the 3/4" M/C for your clutch.)

    Now that you have a good baseline, you will want to work out some other factors. For this, I need to know total car weight (estimate) & front to rear weight balance (estimate) ... tire type & sizes front & rear ... and the driving environments you plan for this car. Then we'll dial it in better.

    While I'm waiting on your response, I'm going to add some posts for "Reference Material" to be used later in our conversation.

  10. #30
    Join Date
    Nov 2012
    Location
    Sacramento, CA
    Posts
    2,338
    Country Flag: United States

    Default

    Reference Post #1

    Craig, let's talk brake pads, so you have a better feel of how critical a role this plays on the braking force.

    We use the "A" pad a lot in racing. I have racers that "love" the A pad in oval & road racing, and I have racers that feel it is too "mean" (too aggressive) in their race car. It has a steep ramp up ... and down. It changes too much from cold to be an optimum Autocross pad. It has a narrow "sweet spot" it needs to run in for optimum braking, then LOSES braking force if over heated. Not a good pad for an inexperienced race driver. I feel most people would not enjoy it as a street pad ... especially the high wear rate & cost.

    The "B" pad is the most common race pad Wilwood sells. It has a safe feeling, because it brakes better all the way up to 700 degrees ... then stays pretty consistent to 1050 degrees ... then fades slightly. (Boiling the brake fluid will be the bigger problem if the car continues to see those temps in the run/race.) I recommend the B pad for most rookie racers in oval & road racing, until they get enough experience & skills to know if they want something different. For Autocross, if the driver wasn't getting the brakes hotter than 500 degrees on a run ... the "B" pad would be "ok". From 100 degrees to 500 degrees, it changes from CF# of .49 to .55. This is a good multi-purpose brake pad for autocross & track days. It would make a good "street fighter" pad, but wear & cost are kind of high.

    The BP-30 pad has similar characteristics to the "B" Pad, but with higher initial "bite" when the rotors are cold ... then a steeper ramp ... going from .52 to .62 at 500 degrees. That is not the characteristics we want in an Autocross pad. This pad compound does provide a lot of confidence for rookie race drivers because, even when cold, the brakes grab "right now" & just gets better as the driver stays on them ... and then flattens out. Braking force trails off when the driver over uses & over heats them, but it is gradual. This is a good race pad for rookie race drivers on road courses and even a good "mean" street pad. Cost is lower than then the B pad.

  11. #31
    Join Date
    Mar 2005
    Location
    Just North of NYC
    Posts
    295

    Default

    Ron, great insights on this thread. I run Wilwood SL6 on 13" and Wilwood 4 piston rears on 12" rears with Hyrdoboost. I landed on the E pads myself for my 3100lb Mustang on the street and autocross after some trial error. However, they didn't hold up on a track day at NJMP... Fronts overheated and left deposits on my rotors that created an impressive pedal chatter from "warped rotors". I don't have cooling ducts yet.
    I should mention that a set of A compound pads driven around on the street cleaned up the deposits and the brakes don't pulsate anymore. I now run the A in the front and E in back for track days, and E all around for street.
    My only complaint with the brakes is no travel. Hydratech booster requires big toe only braking or they're locked up.

  12. #32
    Join Date
    Nov 2012
    Location
    Sacramento, CA
    Posts
    2,338
    Country Flag: United States

    Default

    Reference Post #2

    Craig, I misspoke earlier. The original #'s I gave you were with the "B PADS" ... Not the BP-30 Pads.

    Now, let's play with some #s utilizing different brake pads & you can see your system with different pads. Don't jump to any conclusions yet ... because there is more to consider than just brake torque numbers.

    Here is your baseline with B pads, operating at 500 degrees. Let's use the 500 degree temp throughout our comparisons.

    Total 3566#
    Front 2347# 65.8%
    Rear 1219# 34.2%


    Here it is with BP-30 Pads

    Total 3948#
    Front 2598# 65.8%
    Rear 1350# 34.2%


    Here it is with A Pads

    Total 4330#
    Front 2849# 65.8%
    Rear 1481# 34.2%


    Ok, now lets go the other way on pad selection ...


    Here it is with E Pads

    Total 2993#
    Front 1969# 65.8%
    Rear 1023# 34.2%


    Here it is with BP-10 Pads

    Total 2674#
    Front 1760# 65.8%
    Rear 914# 34.2%


    Here it is with Hawk HPS Pads

    Total 2420#
    Front 1592# 65.8%
    Rear 827# 34.2%

    What most people learn from this exercise, is that brake pads play a bigger role than they thought. In many situations (many ... not all) A brake compound change, can be a bigger change to the car's braking force than going to a bigger rotor or different calipers.

    I urge you not to get lost by just looking at static CF#'s. That's like looking at cam lift numbers. Two cams can have the same maximum lift, yet have very different characteristics in the engine. Same with picking brake pads. You will want to look at the whole big picture, to get the optimum performance. (With cams, brake pads & most other performance items.)

  13. #33
    Join Date
    Nov 2012
    Location
    Sacramento, CA
    Posts
    2,338
    Country Flag: United States

    Default

    Hi Ken ...

    Thanks for chiming in. As a race car designer & builder, I don't have any experience with boosted brakes, hydroboost or otherwise. That may be why your brake pedal is an on/off switch. It may not be too. I simply don't know.

    You didn't list your pedal ratio or master cylinder sizes, which all play a role. But I am absolutely sure that having the brakes act "on or off" ... with very little pressure control ... is not optimum for performance driving.

    If running autocross and/or track days were a one time thing ... you may not care. If you plan on continuing, or increasing your participation, in performance competition events, I would address it for sure. Having more precise brake control will make you a better driver, you'll perform better, be safer & have more fun.

    As far as the E pad goes, it is a GOOD Autocross pad. I would NOT run it on ANY track events longer than 1 lap. Because as this pad heats up past 600 degrees, braking force goes away. That is when the pad is getting eaten up. When you ran that track day at NJMP, the brakes were probably fine for the first lap (maybe). But as they heated up ... you "probably" had to apply more pressure to "whoa the car down" on corner entries ... and that shot the temperatures even higher, making the pads fail.

    Go look at the brake graph on page 6 of the Wilwood brake pad catalog here:
    http://wilwood.com/Pdf/Catalogs/BrakePadCatalog.pdf

    Pay special attention to when a brake pad compound CF graph GOES DOWN as brake temps rise. That is when the pad is being used outside it's "Happy Window" and all kinds of bad stuff happens ... pads fail, rotors glaze up, brakes fade, etc. etc. You usually find out what it costs to repair crashed cars at that point. :-(

    Look at the graph ... the E pads falls off rapidly past 600 degrees. Which means ... don't use this pad in applications above 600 degrees. Autocross ... if the car handles well ... should not see above 600, so it is a good Autocross pad. But a "scary" pad for oval or road course racing, where on long runs the possibility of temps getting above 600 is there in the rear ... and more than possible ... it is probable in the front.

    I, personally, wouldn't run the E pad "long term" on the street ... maybe in the rear ... maybe. I would have a set of E pads that I put on the car for Autocross events ... drive to the event ... run them ... and take them off when you get home & put your street pads back in.

    Let me know if you need any help.

  14. #34
    Join Date
    Sep 2008
    Location
    JACKSONVILLE, FLORIDA
    Posts
    568
    Country Flag: United States

    Default

    Quote Originally Posted by Ron Sutton View Post
    Nice Craig ! This hot rod is going to have a lot of braking. Here are the #'s

    If you use the BP-30 pads (more on pads later) and put the 7/8" M/C on front & the 13/16" M/C on the rear:

    Total 3566#
    Front 2347# 65.8%
    Rear 1219# 34.2%

    That's looking sweet for a baseline. Most stock street car brake systems have 2200-2800# braking force. You are at 3566#, now into race brake system territory (3000-5500#). This layout of M/C sizes provides you with a good baseline ... near 65/35 brake balance front to rear. (use the 3/4" M/C for your clutch.)

    Now that you have a good baseline, you will want to work out some other factors. For this, I need to know total car weight (estimate) & front to rear weight balance (estimate) ... tire type & sizes front & rear ... and the driving environments you plan for this car. Then we'll dial it in better.

    While I'm waiting on your response, I'm going to add some posts for "Reference Material" to be used later in our conversation.
    Thanks Ron,

    Seriously appreciate you looking over my shoulder on this setup.

    Weight. It's a pig. 3650 guesstimate. Balance is all wrong as well. Probably 60/40, but I have lots of nose weight (turbos, a/c, intercoolers and assorted heat exchangers). I built this car as a compromise. Never going to be a good auto crosser, but a street/trackday/land speed car.

    Tires are 295 rear and 275 front Falken Azenis on 18" rims. 200 tread wear.
    Craig Scholl
    CJD Automotive, LLC
    Jacksonville, Florida
    904-400-1802
    www.cjdautomotive.com

    "I own a Mopar, I already know it won't be in stock, won't ship tomorrow, and won't fit without modification."

  15. #35
    Join Date
    Nov 2012
    Location
    Sacramento, CA
    Posts
    2,338
    Country Flag: United States

    Default

    Reference Post #3

    Craig, let's talk brake bias. When you run this car at track, optimum lap times will only be achieved with optimum braking. In racing, many factors come into play with brakes. Consistency, warm up, fade, along with total braking force and brake bias (front vs rear). For this portion of the conversation, let's talk brake bias.

    First, let's define optimum brake bias. It is when the driver can brake hard into the corner ... and I mean HARD, threshold braking ... without one end of the car locking up the tires prematurely. If the front tires lock up under threshold ... the car will push/understeer on corner entry. If the rear tires lock up under threshold ... the car will be loose/oversteer on corner entry. Neither is optimum for car control or lap times.

    * You know the difference between push & loose ... right? Push is when you hit the barrier with the front end. Loose is when you hit the barrier with the rear end. :-)

    Ultimately, you will want to get the brakes balanced front to rear ... meaning that neither end locks up the tires ... or, if you have too much total brake force ... the brakes lock up at the same time, putting the car into a 4-wheel drift. (More on total brake force later).

    People can tell you that you absolutely need XX% front & xx% rear ... but no one really knows what a car needs "exactly" unless they have ran that car that day. There are too many factors that determine the correct front/rear percentage for that car. Heck, it even varies throughout the day as the track changes ... or if you make suspension tuning changes.

    Softer front springs, softer compression valving on the front shocks or softer rebound valving on the rear shocks (amongst other tuning changes) all make the car transfer more weight onto the front tires under braking ... giving the front tires more grip ... and the rear tires less grip ... requiring a slight adjustment to the front/rear brake bias. (There are many, many more tuning situations that affect tire grip. Anything that affects tire grip, affect braking capabilities.)

    THANK GOODNESS ... you have the Wilwood pedal assembly that is adjustable for bias. :-) It won't change your total braking force, like proportioning valves do. It will allow you to easily & quickly adjust the brake bias either direction. It has a lot of range, so as long as you start in the middle, and have both master cylinder rods even, you'll have a lot of adjustability. You can do it by hand, right at the bias bar, or you can add a cable with a knob, and do it by hand from just about anywhere in the cockpit, including the drivers seat, which is how most race cars are set up.

    I suggest the cable, in a spot easily reachable from the driver's seat. After you have run enough corners to get comfortable ... and start to brake harder ... when you find one of the car's brakes locking up ... simply dial brake bias away from that end. Do this on straights ... when you have time. This is also why I suggest putting the brake bias knob in a comfortable spot, that you can put your hand on easily, without even looking.

    Continue sneaking up on the braking force into corners ... and continue to adjust the bias on straights until the car is "happy" ... with neither end of the car locking up, under hard, threshold braking. Not only does this make the car produce quicker lap times, but it also inspires confidence in the driver.

    As the day goes on, and track conditions change, you will notice the brake bias needs to be adjusted slightly to be optimum for the track conditions. Again, if you make a suspension tuning change, the brake bias may need to be adjusted to stay optimum.

    Somewhere in the 65/35 to 70/30 front/rear brake bias is a good starting point. But you'll need to tune from there. If you find, and many racers do when building a new car or new set-up, that you run out of bias adjustment and still need more bias correction, this can be handled easily with a master cylinder change. It is relatively low cost & VERY predictable.

    Bias can also be corrected with a caliper change (more expensive) and by mixing pads front & rear. I have done it all of these ways, in different situations.

    Mixing pads requires a thorough knowledge of pad compound characteristics. If all pads were linear in their friction gain ... this would be easier. But they are not. Each brake pad has its own unique "curve" ... just look at the compound graph ... so mixing the pads causes the front & rear brakes to behave differently. Throw in the fact the rear brakes should be operating at cooler temps than the front brakes ... and you have a complex scenario.

    Mixing brake pads can be done ... and has been done successfully for years. But it requires knowledge, experience and/or testing. I don't recommend it for racing rookies or anyone if they don't have much time at the track to test & sort out a combination. (Unless you have a veteran racer/brake guy advising you). Pick your path.

  16. #36
    Join Date
    Nov 2012
    Location
    Sacramento, CA
    Posts
    2,338
    Country Flag: United States

    Default

    Hi Craig, just got your info ....

    3650# is a typical heavy street car. It will need more than normal braking force to be optimum, and I'd say you have a good start with the system you laid out.

    The 60/40 balance is going to hurt it for Autocross & hinder it for road racing track days too ... but it can still be made into a decent handling performer. Let's make sure you get the brakes dialed in, so you're not chasing brake issues at the track & have time to focus on tuning your suspension set-up at the track.

    The Falken Azenis (200 tread wear) is a good tire. Running 295 rear and 275 fronts will compound the problem of your 60/40 weight balance. Remember, heavier cars need more tire. Heavier ends of the car, can benefit from more tire too. Running smaller tires on the heavy end = not optimum. If you have ANY WAY to run bigger tires in the front, to match the rear, I would.

    A key theory to understand in handling is = force applied to tires creates grip. Tires with softer or better compounds, or more contact patch, that provide increased adhesion ... increase grip. After you have selected the tires ... it's now up to the suspension setup (and aerodynamic aids if they are on the car) to determine the actual force put on each tire during transition stages (braking, turning & acceleration). Actual weight, weight transfer & aerodynamic lift and/or downforce all play a role in determining the total force on each tire. Steady state, straight line driving is less complex than what happens … and what needs to happen for optimum handling … during the transition stages of braking, turning & acceleration.

    This next part gets a little complex.

    You need weight on the tires. With no weight, there is no grip. More weight (whether actual weight, weight transfer or down force) provides more grip from that tire. Engineers use the term “force” instead of weight, which is correct. It doesn’t matter which term you & I use, as long as we both understand each other.

    For sake of simplifying this conversation, let’s take aerodynamics out … and that leaves us focusing on weight (actual) & weight transfer … which added together creates the force #.

    On corner entry … too little weight transfer to the front tires will cause them to break traction, making the car push/understeer. Too much weight transfer will cause the rear tires to lose grip, making the car loose/oversteer on corner entry.

    As a Racer, Tuner, Race Engineer or Crew Chief (just titles) the goal is to utilize the tunable parts of the race car’s suspension to control the amount of weight transfer … to achieve the maximum amount of force on the front tires for optimum turn in … without transferring too much from the rear tires … as to create a loose condition.

    Follow me closely here, because this is where you get a curve ball. The more weight (force) applied to the front tires … the more grip the front tires will have … and therefore the car’s turning ability will be improved ... up to a point.

    As a car goes faster & faster into & through the corners ... the g forces pushing the mass of the car towards the outside of that corner ... are going to overcome the grip the tires have. This is what determines the corning limits of a given car’s set-up.

    Here is where your 60/40 weight bias car has its issue.

    When a car with balanced handling (from tuning) reaches its cornering limits … the end of the car with the greatest weight is the end that breaks free (loses grip).

    I have been involved with many types of race cars that have F/R weight balances of 58/42, 55/42, 53/47, 51/49, 50/50, 48/52, 46/54 & 42/58. You can make any of these cars handle “neutral” up to their limits. (You can also make any of these cars push/understeer or loose/oversteer with tuning.)

    But when they exceed their limits … the heavier end will lose grip first … and go towards the outside of the corner.

    So inherently, front heavy cars will push/understeer when driven past their limits. You can improve the handling of your car and make it a "pretty good" handling machine … up to a point. But … so you are prepared for what is going to happen ... with that much front weight ... the front tires are going to have more grip ... until they don't … and then the front end is going to push/understeer towards the outside of the corner, barrier, wall, etc.

    Anytime you can achieve … or get closer to … a 50/50 weight balance, that car is going to handle better. And when it does reach its limits … the result will not be as dramatic.

    The further a car is away from the optimum 50/50 balance … the more the heavy end is going to limit the car’s overall performance capabilities. And when it breaks traction, the more abruptly it will do so.

    Theoretical example:
    If we had two similar cars ... both set-up & tuned to their optimum & balanced handling … except one had weight balance of 60/40 and other was 55/45 … the 60/40 car is going to lose traction with the front tires at a lower speed than the car with 55/45. So when building cars, ideally, we want to control the weight placement as much as is practical for you, and get as close to the 50/50 balance as you can. Just because your car is estimated at 60/40 … don’t stop working on ways to make it better. 59/41 is better. 58/42 better yet, etc.

    Now, back to brakes … :-)

    The optimum F/R brake bias is ultimately going to be decided based on how much weight transfer you build into the suspension. If you run a "conventional setup" with stiffer front springs, shock valving, etc … to reduce weight transfer to the front … you’ll end up needing more rear braking force. If go the opposite route and run what is known as a “high travel” front with softer springs & a big sway bar … you’ll end up with more front brake bias.

    Regardless, I think you’re on the right track with your current set-up … and you’ll need to adjust & tune it at the track.

    From what I see so far, I would add the brake bias cable adjuster, start with the BP-30 Pads & make sure the pedal ratio is close to 6-1.

  17. #37
    Join Date
    Sep 2008
    Location
    JACKSONVILLE, FLORIDA
    Posts
    568
    Country Flag: United States

    Default

    Thank you for the details!!

    I've had race cars and finally got to the point where I wanted one I could drive all the time without sacrificing too much comfort. I'm building this car to do everything pretty good, but not one thing exceptional. With comfort comes weight. My crutch was more power and big brakes (and I already have the remote cable knob adjuster). I am very much a "high travel" guy. I set it up with a splined swaybar setup from the Cup teams (bought a huge lot of different diameter sway bars cheap), and have good anti-dive designed in the front. Also have double adjustable front and rear shocks. The rear is a decoupled 3-link with torque arm (a tuning nightmare!) but another crutch for the heavy car. I can get some crazy IC's with this. When I get a little closer to putting the car on scales, I'd like to pick your brain a little more.

    Sorry for the thread hijack!

    Really appreciate all your information.
    Craig Scholl
    CJD Automotive, LLC
    Jacksonville, Florida
    904-400-1802
    www.cjdautomotive.com

    "I own a Mopar, I already know it won't be in stock, won't ship tomorrow, and won't fit without modification."

  18. #38
    Join Date
    Nov 2012
    Location
    Sacramento, CA
    Posts
    2,338
    Country Flag: United States

    Default

    Your project sounds awesome & fun.

    If you go with the high travel front end set-up, I have a little secret weapon to allow you to run more brake on corner entry without locking up the rear brakes.

    I am intrigued by your project. Can you tell me/us more about the engine. What model engine? How big? How much power do you estimate?

    Thanks !

  19. #39
    Join Date
    Sep 2008
    Location
    JACKSONVILLE, FLORIDA
    Posts
    568
    Country Flag: United States

    Default

    Quote Originally Posted by Ron Sutton View Post
    Your project sounds awesome & fun.

    If you go with the high travel front end set-up, I have a little secret weapon to allow you to run more brake on corner entry without locking up the rear brakes.

    I am intrigued by your project. Can you tell me/us more about the engine. What model engine? How big? How much power do you estimate?

    Thanks !
    I have a build thread: http://www.pro-touring.com/showthrea...rbo-Cuda-build

    The engine is a 422 c.i. twin turbo dry sump R3 SB Mopar. 16 injector Holley Dominator EFI with traction and boost control. Still setting up the EFI, but should make 750-ish on pump gas and shooting for 1700 HP on race gas for Bonneville and Monster Mile. The 750 number is where the engine will spend 99% of its life.
    Craig Scholl
    CJD Automotive, LLC
    Jacksonville, Florida
    904-400-1802
    www.cjdautomotive.com

    "I own a Mopar, I already know it won't be in stock, won't ship tomorrow, and won't fit without modification."

  20. #40
    Join Date
    Nov 2012
    Location
    Sacramento, CA
    Posts
    2,338
    Country Flag: United States

    Default

    Craig, I went to your build thread & caught on your project. Holy cow. That is awesome.

    I see lots of stock car influences, quality parts through out & a lot of care! This is going to be a really fun hot rod.

Page 2 of 3 FirstFirst 1 2 3 LastLast


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •