Anyone have any Brake Questions?

[cdrod]

Johnny:
Thank you for starting this thread and for your willingness to share your knowledge and experience with the rest of us. I'm building an Olds 442 convertible as a daily driver. I don’t plan to autox this car or race it, but I do want to upgrade to 4-wheel disc brakes and get rid of the 42-year-old drum brakes. I've chosen a rear disc set-up from an '01 Chevy Blazer running the stock 295mm rotors (which are 20mm thick) and the caliper has a single 48mm piston. I want to use C5 Vette parts for the front brakes, which use a 325mm rotor and the caliper has two 40.5mm pistons.

Using some aluminum parts (heads, radiator, AC compressor, etc.) I am removing 300 lbs of sprung weight in the front and the C5 brake parts along with aluminum rims will reduce the front un-sprung weight by 14 lbs per side. I think the overall weight of the car will be around 3500-3600 lbs (without driver) but I don’t know the F-R weight distribution or the weight transfer rate. Since I’m removing 300+ lbs of weight in the front, I should be moving the F-R weight distribution closer to the ideal 50-50 balance.

I’ve built a spreadsheet to allow me to quickly change brake parameters to evaluate the performance of my brake combination and gauge the performance relative to the stock Olds 11” disc w/rear drum system. I have attached a pdf version for your reference – numbers in blue are data inputs, numbers in yellow are important results. My goals are to modernize the brakes (need to be able to stop when those damn Mini Coopers cut you off and slam on the brakes-lol) using readily available OEM parts that can be purchase at any auto parts store. Here are my questions:



1. Do you see any errors in my spreadsheet? I've included a “notes” column to show the formulas used to calculate the results.

2. What is an ideal target for front to rear bias? I plan to run a 285-40R17 tire on the rear so I think the braking could be increased to match the increased traction. My spreadsheet shows a 65-35 balance front to rear. I plan to test drive the car to dial in the prop valve under real-world conditions, but I want to make sure my system bias is close so I don’t have to reduce the rear pressure too much. Does this look OK?

3. What is a good pad CoF for a daily driver? I used a 0.3 CoF in my spreadsheet, should I use a higher value? I don’t want to be too aggressive with the pad CoF to the point I’m changing the pads and/or rotors every 20k miles, but I want the car to stop well.

4. What would be a good master cylinder/booster combination for this car? The booster size shown in my spreadsheet is the stock Olds size and the master cylinder is a 15/16” bore from a Monte Carlo SS. I could use the C5 booster/master cylinder, just not sure how this would work out with the larger 48mm Blazer calipers in the rear. Also, I think the C5 Vette had a quick take-up style master cylinder and the rear brakes had a 45mm caliper.

I’m looking forward to your comments, and anyone else's with more knowledge and experience than me.

[OG_Racing]

Johnny:
Thank you for starting this thread and for your willingness to share your knowledge and experience with the rest of us. I'm building an Olds 442 convertible as a daily driver. I don’t plan to autox this car or race it, but I do want to upgrade to 4-wheel disc brakes and get rid of the 42-year-old drum brakes. I've chosen a rear disc set-up from an '01 Chevy Blazer running the stock 295mm rotors (which are 20mm thick) and the caliper has a single 48mm piston. I want to use C5 Vette parts for the front brakes, which use a 325mm rotor and the caliper has two 40.5mm pistons.

Using some aluminum parts (heads, radiator, AC compressor, etc.) I am removing 300 lbs of sprung weight in the front and the C5 brake parts along with aluminum rims will reduce the front un-sprung weight by 14 lbs per side. I think the overall weight of the car will be around 3500-3600 lbs (without driver) but I don’t know the F-R weight distribution or the weight transfer rate. Since I’m removing 300+ lbs of weight in the front, I should be moving the F-R weight distribution closer to the ideal 50-50 balance.

I’ve built a spreadsheet to allow me to quickly change brake parameters to evaluate the performance of my brake combination and gauge the performance relative to the stock Olds 11” disc w/rear drum system. I have attached a pdf version for your reference – numbers in blue are data inputs, numbers in yellow are important results. My goals are to modernize the brakes (need to be able to stop when those damn Mini Coopers cut you off and slam on the brakes-lol) using readily available OEM parts that can be purchase at any auto parts store. Here are my questions:

1. Do you see any errors in my spreadsheet? I've included a “notes” column to show the formulas used to calculate the results.

2. What is an ideal target for front to rear bias? I plan to run a 285-40R17 tire on the rear so I think the braking could be increased to match the increased traction. My spreadsheet shows a 65-35 balance front to rear. I plan to test drive the car to dial in the prop valve under real-world conditions, but I want to make sure my system bias is close so I don’t have to reduce the rear pressure too much. Does this look OK?

3. What is a good pad CoF for a daily driver? I used a 0.3 CoF in my spreadsheet, should I use a higher value? I don’t want to be too aggressive with the pad CoF to the point I’m changing the pads and/or rotors every 20k miles, but I want the car to stop well.

4. What would be a good master cylinder/booster combination for this car? The booster size shown in my spreadsheet is the stock Olds size and the master cylinder is a 15/16” bore from a Monte Carlo SS. I could use the C5 booster/master cylinder, just not sure how this would work out with the larger 48mm Blazer calipers in the rear. Also, I think the C5 Vette had a quick take-up style master cylinder and the rear brakes had a 45mm caliper.

I’m looking forward to your comments, and anyone else's with more knowledge and experience than me.

I do see some errors. The spreadsheet your using doesn't allow for rotor sizes to be entered. that does Play a huge role into brake TQ and balance.

2 brake bias before using a proportioning valve should be closer to 40-50%. if you where to remove a prop vales the car should be undriveable. that's why a balance bar or a Proportion valve are so important.

3. COF or Mu for a standard street pad is anywhere from .3 - .4... .5-.7 for race pads.

4. As far as the master cylinders go. the 15/16" seams too large for the corvette calipers. The corvette calipers size in with an area of 4^2" the old GM metric calipers where a 4.92^2". a difference of 20% larger to the old single pistons. It would be highly advisable to scale down the Master cylinder size too, or the pedal would fell like a rock. the C5 corvette uses a 13/16" master cylinder size. i am unaware of how much assist the booster provides or the pedal ratio.


My recommendation for your set up is to run an C5 master cylinder for you braking system. the K5 rear brake master cylinder is larger then the C5 rear calipers by 7%, but you have a 7% smaller rotor. so things will be quite even. one thing that allot of people over look when building a DIY brake kit is pad choices. Most mopar guys run into this issue. the selection of pads for the corvette is much larger then pad selections for a C5 blazer. You would be very lucky to find matching compounds front and rear.

[cdrod]

I do see some errors. The spreadsheet your using doesn't allow for rotor sizes to be entered. that does Play a huge role into brake TQ and balance.

2 brake bias before using a proportioning valve should be closer to 40-50%. if you where to remove a prop vales the car should be undriveable. that's why a balance bar or a Proportion valve are so important.

3. COF or Mu for a standard street pad is anywhere from .3 - .4... .5-.7 for race pads.

4. As far as the master cylinders go. the 15/16" seams too large for the corvette calipers. The corvette calipers size in with an area of 4^2" the old GM metric calipers where a 4.92^2". a difference of 20% larger to the old single pistons. It would be highly advisable to scale down the Master cylinder size too, or the pedal would fell like a rock. the C5 corvette uses a 13/16" master cylinder size. i am unaware of how much assist the booster provides or the pedal ratio.


My recommendation for your set up is to run an C5 master cylinder for you braking system. the K5 rear brake master cylinder is larger then the C5 rear calipers by 7%, but you have a 7% smaller rotor. so things will be quite even. one thing that allot of people over look when building a DIY brake kit is pad choices. Most mopar guys run into this issue. the selection of pads for the corvette is much larger then pad selections for a C5 blazer. You would be very lucky to find matching compounds front and rear.

Johnny:
Thanks for your reply. Actually, the second row of my spreadsheet has the rotor sizes. Not being defensive, just pointing out the data is there.

#2. What's a good brake bias balance after the proportioning valve? It seems to me that if I start out with a 50-50 front to rear balance before the proportioning valve I would be at the limits of the proportioning valve to reduce the line pressure to the rear calipers. Don't most valves max out at around 50% reduction?

#4. The stock Olds calipers on the front of the 442 were a single piston design with a diameter of 2.93" and a piston area of 6.7 sqin. In comparison, the C5 caliper piston area is approximately 4 sqin, which is 40% smaller than the Olds, but the C5 rotor diameter is 16% larger than the Olds 11' rotor. The stock Olds used a 1-1/8" MC (lots of volume to fill those huge calipers) but the C5 calipers should need 40% less volume for the same amount of piston travel. I came up with the 15/16" MC size by reducing the sotck Olds MC size by 40% (1.125 * .60) which falls between 7/8" and 15/16". I was also concerned about too much pedal travel with a smaller MC bore, and not sure how the MC size will affect pedal modulation.

I didn't think about pad availability for the Blazer rears, but couldn't this be fine tuned with the rear proportioning valve? i.e. a grippy pad in front, not so grippy pad in back, needs little more brake bias to the rear. And wouldn't I be able to find a good pad, If I stay with a less aggressive street pad (CoF .30 - .35)? Like a semi-metallic AC Delco pad? Remember, I'm not looking for autox or racing level performance, just good daily driver performance on par with a modern vehicle.

Thanks!

Rodney

[OG_Racing]

http://youtu.be/-bm5aW_tga4

Found this nice video from Stop Tech on how flexy Factory calipers are. before you start knocking the results remember that this test is at room temperature, with a hand pump. Normal Brake system will see 1200-1500psi. at a race a calipers can see >600*
__________________

[Hugger67RSSS]

I have a set of Baer 6S front calipers with 14" rotors that I want to use on my 68 Camaro. I have a 9" rear that has the new style ford ends. (Non floater obviously) and have been looking for a floating rear caliper. Will the wilwood D154 setup with a piston area of 4.12 work for the rear with my front brakes?
My front calipers have 1.62,1.37, and 1.18 Pistons. My car has a 7/8 manual wilwood master on it now.

http://www.wilwood.com/Calipers/Cali...ston%20Floater

Thanks!

[OG_Racing]

I have a set of Baer 6S front calipers with 14" rotors that I want to use on my 68 Camaro. I have a 9" rear that has the new style ford ends. (Non floater obviously) and have been looking for a floating rear caliper. Will the wilwood D154 setup with a piston area of 4.12 work for the rear with my front brakes?
My front calipers have 1.62,1.37, and 1.18 Pistons. My car has a 7/8 manual wilwood master on it now.

http://www.wilwood.com/Calipers/Cali...ston%20Floater

Thanks!

Hello Hugger,
What size rear rotors are you planning on running?

[Hugger67RSSS]

12.19" rear rotors

[OG_Racing]

hugger,
What pedal ratio are you using? i'm having a hard time reccomending master cylinders for you. looks like the 7/8's is not going to work.

[Hugger67RSSS]

Stock pedals with the master bolted to the top hole, I've always thought that made it 6:1 but I could be wrong. Is there another rear brake kit you would recommend with the fronts that is a floating caliper that would help alleviate my pad knock back instead of the wilwood kit? Baer does not make a floating caliper that I'm aware of.

Thanks again

[OG_Racing]

Stock pedals with the master bolted to the top hole, I've always thought that made it 6:1 but I could be wrong. Is there another rear brake kit you would recommend with the fronts that is a floating caliper that would help alleviate my pad knock back instead of the wilwood kit? Baer does not make a floating caliper that I'm aware of.

Thanks again

here is the problem i'm having. in order for you to keep your Pedal pressure under 100lbs with those calipers you'll need 1/2" master cylinder. the smaller the MC the more you'll need to travel. with a .5" mc you'll need 70" of pedal travel or with the current MC you'll need to press 250lbs of force to get your system to 1200psi. i think your going to need a booster to get there. I haven't even started on brake balance of the braking system yet, but the front pistons are so small and the rotors are huge. i'm not sure if i can find a floating system that can match it off the shelf.


your going to want to run a booster with that set up.
can you do this?

[71RS/SS396]

Stock pedals with the master bolted to the top hole, I've always thought that made it 6:1 but I could be wrong. Is there another rear brake kit you would recommend with the fronts that is a floating caliper that would help alleviate my pad knock back instead of the wilwood kit? Baer does not make a floating caliper that I'm aware of.

Thanks again

I believe Baer is now making a floating caliper to match your front brakes. I'm pretty sure Tom Farrington (tommycomfort) has them on his 66 Chevelle.

[Hugger67RSSS]

My motor doesn't produce a ton of vacuum, haven't checked it but I'm sure it's pretty low. I'm curious as to why you say the Pistons are so small? Baer recommends a 7/8 master but that is with their setup on the rear also. Glad I asked the question now.
Would I be better if keeping the C6 Z06 brakes on the car? They work good but having knock back issues.
Thanks

[OG_Racing]

My motor doesn't produce a ton of vacuum, haven't checked it but I'm sure it's pretty low. I'm curious as to why you say the Pistons are so small? Baer recommends a 7/8 master but that is with their setup on the rear also. Glad I asked the question now.
Would I be better if keeping the C6 Z06 brakes on the car? They work good but having knock back issues.
Thanks

tell me about what your car is doing. the answer might be better then a whole new kit. try to include all the details.

[Hugger67RSSS]

The car has about 700 miles on it now, normal street driving the brakes work perfect. I can achieve lockup with enough pedal pressure.
I took the car to a couple local scca autocross days and will lose about half of the pedal after hard corners. If I pump it once or twice quickly they are instantly back to normal. It is bad enough that I didn't want to take it to the indianapolis good guys and not feel comfortable with it. They have been bled a couple times since installed and haven't gotten out anymore air.
All of this with 7/8 wilwood master and front and rear C6 Z06 brakes. Non floating rear axle.

Thanks!

[OG_Racing]

The car has about 700 miles on it now, normal street driving the brakes work perfect. I can achieve lockup with enough pedal pressure.
I took the car to a couple local scca autocross days and will lose about half of the pedal after hard corners. If I pump it once or twice quickly they are instantly back to normal. It is bad enough that I didn't want to take it to the indianapolis good guys and not feel comfortable with it. They have been bled a couple times since installed and haven't gotten out anymore air.
All of this with 7/8 wilwood master and front and rear C6 Z06 brakes. Non floating rear axle.

Thanks!

sounds like your right it is pad knock back. i would install the z51 brakes in the rear. use a kore 3 kit, or convert your axle to a full floating axle.

[Hugger67RSSS]

Stock pedals with the master bolted to the top hole, I've always thought that made it 6:1 but I could be wrong. Is there another rear brake kit you would recommend with the fronts that is a floating caliper that would help alleviate my pad knock back instead of the wilwood kit? Baer does not make a floating caliper that I'm aware of.

Thanks again

I believe Baer is now making a floating caliper to match your front brakes. I'm pretty sure Tom Farrington (tommycomfort) has them on his 66 Chevelle.

Thanks Tim,
I will call Baer or PM Tom since he is local to me.

[Hugger67RSSS]

The car has about 700 miles on it now, normal street driving the brakes work perfect. I can achieve lockup with enough pedal pressure.
I took the car to a couple local scca autocross days and will lose about half of the pedal after hard corners. If I pump it once or twice quickly they are instantly back to normal. It is bad enough that I didn't want to take it to the indianapolis good guys and not feel comfortable with it. They have been bled a couple times since installed and haven't gotten out anymore air.
All of this with 7/8 wilwood master and front and rear C6 Z06 brakes. Non floating rear axle.

Thanks!

sounds like your right it is pad knock back. i would install the z51 brakes in the rear. use a kore 3 kit, or convert your axle to a full floating axle.

I already have the set of 6S Baer front brakes, nothing will work with those in the rear so I can sell my Z06 brakes as a set of 4?
Thanks

[OG_Racing]

any other questions?

[andrewb70]

any other questions?

What do I do with a car that will be drag strip oriented and has skinny front tires and larger rear tires?

Andrew

[OG_Racing]

What do I do with a car that will be drag strip oriented and has skinny front tires and larger rear tires?

Andrew

haha get more front tire :P

you don't need brakes for drag racing