Anyone have any brake questions?
#802
AP Racing's prop valve datasheets actually illustrate the hysteresis, especially on their sheet for the **** type one. It looks very much like if you tune the thing to get the rear forces right at threshold braking, as you ease off, the rears are going to stay at higher pressure until you get to the knee point. Further, they say it gets worse the further down the pressure curve you put the knee, so even worse for non-boosted masters. All of this sounds not-great to me. Now, it may be that Wilwood and Tilton have better prop valves than AP, but somehow I doubt it.
#803
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I definitely overlooked the fact that dual masters split the pedal force in half at each master. I only validated brake bias with my spreadsheet, and forgot to look at overall pedal force. Dual 5/8" may be doable with a pedal ratio change, but I think I may look at a single master booster delete.
#804
Other than the small weight savings, I'm not sure what the current fascination with booster deletes is. Set up properly, you can get a rock solid and consistent pedal using an OEM booster. My guess is there are owners out there that haven't been able to do that and decide to throw the baby out with the bathwater. What I often hear/read is owners wanting to save money by using some inappropriate parts and trying to tune around it. To me, that's like setting up a chassis on worn out tires. Waste of time. Do the homework to figure out what the right setup will be and start saving. Last time I checked, brakes are kinda important on a race car.
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I hate to be that guy, but part of my motivation is cleaning up the bay and freeing up space. My V8 build is leaning towards track car, but it's also a daily driver that's taken to countless meets/shows and I enjoy having a nicely tucked bay.
So if it's between getting a 1" master, and getting a 3/4" master and deleting the booster, I'll choose the booster delete. Cost is relatively the same, and I have the manufacturing ability to make it reliable. Plus I'm not too sure how the booster will like the moderate cam I have planned.
So if it's between getting a 1" master, and getting a 3/4" master and deleting the booster, I'll choose the booster delete. Cost is relatively the same, and I have the manufacturing ability to make it reliable. Plus I'm not too sure how the booster will like the moderate cam I have planned.
#807
Other than the small weight savings, I'm not sure what the current fascination with booster deletes is. Set up properly, you can get a rock solid and consistent pedal using an OEM booster. My guess is there are owners out there that haven't been able to do that and decide to throw the baby out with the bathwater. What I often hear/read is owners wanting to save money by using some inappropriate parts and trying to tune around it. To me, that's like setting up a chassis on worn out tires. Waste of time. Do the homework to figure out what the right setup will be and start saving. Last time I checked, brakes are kinda important on a race car.
#809
140 pounds of leg force is ******* steep. Thats 1950's no power booster full sized car on 4 wheel drums **** right there. Pull up on the steering wheel and give her all she's got in every braking zone doesnt sound fun.
killjoy, the balance bar and prop valve do different things. The balance bar changes the brake balance at all amounts of braking force while the prop valve only changes it at high forces. You need to tune for both unless you want to suck at trail braking.
killjoy, the balance bar and prop valve do different things. The balance bar changes the brake balance at all amounts of braking force while the prop valve only changes it at high forces. You need to tune for both unless you want to suck at trail braking.
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#810
ok i need to clear some stuff up. at PFC we spent 2 months learning about pedal boxes before we where allowed to talk to any customers. my boss was a former tiltion rep.
1 OK manual brakes. we can get manual done. it's not that hard. Yes you want different sized MC's, why? because you want less line pressure to the rear. you want to use the balance bar only to adjust bias while the car is in motion. we do not want to have the biar bar to get maxed out. if it maxxes out you'll need to buy a larger rear mc anyway. so we need to set up the Bias as close to perfect as we can.
1.5 i have yet to pop my head into any race car on any professional level and find the balance bar adjusted correctly. we always find something. so be careful who you take advice from.
2 yes you want more then 4:1 pedal ratio. in the industry we call it cheating to increase the pedal ratio. mostly because it has little to no trade off. you just get extra pedal distance. so when you weld in your willwood balance bar thing. move it up closer to mounting point.
3 i wouldn't do manual brakes with stock sized pistons. the factory miata brakes rely on a ton of vacuum assist. in my car i did the 1.75 Fronts and 1.375 pistons out back all on 11.75" rotors we did 3/4" and 13/16 rear mc. the tilton pedal box has a 5.75;1 ratio. i have 100lbs press @45ish mm to achieve a 1.5g stop.
1 OK manual brakes. we can get manual done. it's not that hard. Yes you want different sized MC's, why? because you want less line pressure to the rear. you want to use the balance bar only to adjust bias while the car is in motion. we do not want to have the biar bar to get maxed out. if it maxxes out you'll need to buy a larger rear mc anyway. so we need to set up the Bias as close to perfect as we can.
1.5 i have yet to pop my head into any race car on any professional level and find the balance bar adjusted correctly. we always find something. so be careful who you take advice from.
2 yes you want more then 4:1 pedal ratio. in the industry we call it cheating to increase the pedal ratio. mostly because it has little to no trade off. you just get extra pedal distance. so when you weld in your willwood balance bar thing. move it up closer to mounting point.
3 i wouldn't do manual brakes with stock sized pistons. the factory miata brakes rely on a ton of vacuum assist. in my car i did the 1.75 Fronts and 1.375 pistons out back all on 11.75" rotors we did 3/4" and 13/16 rear mc. the tilton pedal box has a 5.75;1 ratio. i have 100lbs press @45ish mm to achieve a 1.5g stop.
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#811
NEVER EVER RUN A PROP VALVE AND A BALANCE BAR. no stop dont do that, nope stop.
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#812
i'll post the spread sheets we use tomorrow. night yall!
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#814
I can't share too much of this. It has some serious Proprietary information but it demonstrates the effort you'll need to run manual brake with stock Piston sizes and pedal ratio.
it says we will need a Pad of .44mu i cannot express how much Hawk Carbo tech and Padgid Skew their Mu for marketing reasons. a very very high torq pad will be in the .56mu range.
As we can see with a 3/4 - 7/8's combo the balance of the car comes out great, the mu requirement is equal. this will allow us to set the balance bar in the center for maximum adjust-ability. this also gives us adjust-ability for compound choices.
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#815
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#816
ninja edit. I found the thread. lol man that guy is just spewing false information. let's dig shall we.
Yes, we maximized clearance inside of a 6UL and left 3mm between the caliper and wheel barrel. That is our minimum clearance requirement.
Does this difference matter? No, not compared to the StopTech BBK. The 11.75' rotor is 298.45mm. The difference in diameter is 298-280 = 18mm, which means the difference in radius is 9mm. This gives the competitive rotor a slight advantage in brake torque IF both brake pads were identical but in this case they are not.
The contact area of the brake pad on the rotor is larger in the StopTech kit, effectively increasing brake torque compared to the competitor. This increase completely offsets any disadvantage in the 9mm rotor radius difference. This also makes the StopTech rotor lighter by a fraction.
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Last edited by OGRacing; 07-01-2016 at 02:00 PM.
#817
Two more questions. Given a basic caliper layout (call it 2 piece bolted Dynalite size with one bridge bolt) how much scope for stiffer calipers is there *really*? I mean yeah, the STR-42 is going to be more nicely machined than Wilwood's stuff, but it seems like there's limits here. Oh yeah and ******* LOL at the guy claiming the pad size is going to affect things when it's literally using a Dynapro pad.
Secondly, what's a decent back-of-the-envelope friction coefficient to use for something like PF01/11/14? Not asking for the keys to the bank or anything, but if Wilwood and stuff are saying 0.65-0.7ish is a high friction pad, you're saying 0.56 is a high friction pad, what's a value to use for sizing things for a medium friction pad?
Secondly, what's a decent back-of-the-envelope friction coefficient to use for something like PF01/11/14? Not asking for the keys to the bank or anything, but if Wilwood and stuff are saying 0.65-0.7ish is a high friction pad, you're saying 0.56 is a high friction pad, what's a value to use for sizing things for a medium friction pad?
#818
Two more questions. Given a basic caliper layout (call it 2 piece bolted Dynalite size with one bridge bolt) how much scope for stiffer calipers is there *really*? I mean yeah, the STR-42 is going to be more nicely machined than Wilwood's stuff, but it seems like there's limits here. Oh yeah and ******* LOL at the guy claiming the pad size is going to affect things when it's literally using a Dynapro pad.
Secondly, what's a decent back-of-the-envelope friction coefficient to use for something like PF01/11/14? Not asking for the keys to the bank or anything, but if Wilwood and stuff are saying 0.65-0.7ish is a high friction pad, you're saying 0.56 is a high friction pad, what's a value to use for sizing things for a medium friction pad?
Secondly, what's a decent back-of-the-envelope friction coefficient to use for something like PF01/11/14? Not asking for the keys to the bank or anything, but if Wilwood and stuff are saying 0.65-0.7ish is a high friction pad, you're saying 0.56 is a high friction pad, what's a value to use for sizing things for a medium friction pad?
i like to show this video of a standard stoptech st-60 caliper vs a similar sized OEM manufactured Brembo. Both have good names one is just built for mass production and costs are low. the other is built for Motorsports.
Like iv'e said before I've sold calipers that at full speed wouldn't flex more then 0.1mm. those are going to have incredibly low drag, but cost more then 120 bucks.
back of the envelope I cannot tell you what the Mu's are. the reason they are not published is because the numbers can be manipulated easily. Lets look at tires. A tire's mu changes with the surface it interacts with. a tires mu will increase on tarmac, concrete and rubber. in that order. rubber on rubber mu can be over 1.1mu (notice when two tires touch and one car gets flung into orbit), as tarmac it can be as low as .5. we can also manipulate brake Mu with temperature, rotor size. rotor iron consistency. hell we could put a dyno in the arctic circle, a gigantic rotor made from other pads, under vacuum and get .7mu out of a set of xp10. i know PFC's mu numbers and i use PFC charts to pick out pad compounds. both the charts and the pads have the same testing variables. so i know what i'm grabbing off the shelf. sharing that chart is dangerous because everyone thinks "oh i need a .45mu pad", they go over to carbos, buy a pad that says.45 mu, they crash because carbotech inflates their numbers. hawk says the dtc70 get's .9mu. that's enough friction to rip the suspension pick up points out of a car. on an average GT car .45 mu is perfect. it gives us the right about of bight, good modulation and not too much tq that your going to be flatspotting tires.
The short list is PFC doesn't post Mu number because everyone else distorts their Mu numbers. We would either need to be dishonest or just avoid the whole situation altogether.
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#819
i've seen as low as 0.1mm and that was from he spokes. i guess airing on the side of caution is good.
11.75" rotors are 299mm if we want to nit-pick. 299-280 that's a 6.35% difference. that is enough to be noticeable in torque.
pad area dictates longevity, not friction. And this Kit uses the 7752 pad. same as all the Dynalite kits so the pad is exactly the same as almost all of the competitors.
6.35% difference in rotor diameter does not necessarily equate to a torque difference (but it could) if the center lines of the pads on the rotor annulus are different, especially with different pad areas.
The 7752 pad is not used in the StopTech BBK. It is using the FMSI# 8567 (DR22) pad shape. The difference in area between the two is 10mm in pad height for the width of the pad or 5633.6mm^2 as compared to 4646mm^2 so the 8567 pad has 17.5% larger contact area.
http://www.stoptech.com/images/defau...e-pads/d22.jpg
7752 | PFC Brakes - Performance Friction
Totally agree that pad volume speaks to longevity - no argument there. Add to that higher caliper stiffness and differential bores - all contribute to pad life.
Great video of caliper flex - that demo unit is sitting in our engineering offices.
Last edited by Jumbosrule; 07-01-2016 at 04:18 PM.
#820
Im on here too - no bad blood though, this is all good discussion. Did not think there was any amount of spewing - just trying to turn the engineering concepts into common language for people that are not embedded in the business. We run in house testing systems on a Link brake dyno and can confirm temperature, torque output, line pressures and deceleration times based on preset vehicle speeds before we go to dynamic, on-car testing. I don't have to tell you how poorly understood braking is to the average enthusiast. Simple concepts are very often tempered by quite a few other factors in the system.
6.35% difference in rotor diameter does not necessarily equate to a torque difference (but it could) if the center lines of the pads on the rotor annulus are different, especially with different pad areas.
The 7752 pad is not used in the StopTech BBK. It is using the FMSI# 8567 (DR22) pad shape. The difference in area between the two is 10mm in pad height for the width of the pad or 5633.6mm^2 as compared to 4646mm^2 so the 8567 pad has 17.5% larger contact area.
http://www.stoptech.com/images/defau...e-pads/d22.jpg
7752 | PFC Brakes - Performance Friction
Totally agree that pad volume speaks to longevity - no argument there.
Same here. We test all friction relative to each other so numbers are comparative but find the same industry inflation everywhere.
Great video of caliper flex - that demo unit is sitting in our engineering offices.
6.35% difference in rotor diameter does not necessarily equate to a torque difference (but it could) if the center lines of the pads on the rotor annulus are different, especially with different pad areas.
The 7752 pad is not used in the StopTech BBK. It is using the FMSI# 8567 (DR22) pad shape. The difference in area between the two is 10mm in pad height for the width of the pad or 5633.6mm^2 as compared to 4646mm^2 so the 8567 pad has 17.5% larger contact area.
http://www.stoptech.com/images/defau...e-pads/d22.jpg
7752 | PFC Brakes - Performance Friction
Totally agree that pad volume speaks to longevity - no argument there.
Same here. We test all friction relative to each other so numbers are comparative but find the same industry inflation everywhere.
Great video of caliper flex - that demo unit is sitting in our engineering offices.
my mistake. when i talked with stop tech two years ago they mentioned that it would take the same pad as the dynalight. the 7752 shape. the difference in swept area between the dr22 and the 7752 is actually less pad volume going towards the dr22 pad shape.
I would need to disagree that this kit wouldn't "outbreak" a Dynalight 11.75" but what you do have over everyone else is a miles better caliper. Stoptechs claim to fame is bad *** calipers. I would guess that it should have substantially less drag in the system. less drag = longer life, better performance. but with miracle stop #1 i would be surprised to see higher Tq output.
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