Am I expecting too much? [Archive]

67gtonut

02-26-2012, 02:46 PM

67 GTO manual brakes

Stock style Single piston calipers up front
Stock rear drums
Wilwood 7/8" tandem master
Adjustable prop valve

Should I be able to lock up the wheels under heaving braking?

Just installed the Wilwood master.... bled the crap out of it... took a bit, some air was trapped in the master. I have a decent pedal, little mushy, but not bad. I cant get front or rear brakes to lock...... Really never could.....

Am I heading for at least a small 7 or 8" booster to get enough clamping force to lock wheels? OR am I missing something in this manual set-up?

Thanks

Troy

SLO_Z28

02-26-2012, 02:53 PM

What condition are the stock drums and rotors/pads in, and what pads are you using? I can easily lock up my tires, or the tires of almost any car, with the stock setup.

BonzoHansen

02-26-2012, 05:05 PM

what kind/size of tires?

67gtonut

02-26-2012, 06:53 PM

Raybestos pads and Rotors.... all with less them 1000 miles on em.....

235/60's on front
245/60's on rear
15" rims.....

Apogee

02-26-2012, 09:44 PM

Considering the factory manual disc/drum setup used a 1" bore master cylinder and could typically achieve lockup when functioning properly, I would say you have an issue somewhere. The 7/8" bore MC should be providing 25% more caliper pressure as the 1" bore unit did for the same input force at the pedal, albeit with 25% more pedal travel as well. Your OE front calipers have a lot more piston area than a C5/C6 caliper (6.7 sq-in versus 4.0 sq-in), and we can typically achieve lockup with reasonably moderate pedal effort depending on the pad compound.

When you bench bleed the master cylinder, did you plug both outlet ports and confirm that the piston hydraulically locked when you attempted to stroke it? If not, then it's possilbe you still have air in your MC which could very easily be causing the symptoms you're describing. Also, you're running a disc/disc master cylinder, so you should probably be running a 10 psi residual pressure valve in the rear circuit (if you're not) to maintain pressure on the rear wheel cylinder seals so they don't leak fluid out or air into the system.

Tobin
KORE3

67gtonut

02-27-2012, 02:08 AM

Thanks for the replies......

I did bench bleed the master the best I could...... I think I need to bleed the system even further.....

I bought speed bleeders for the rear and it did seem to get better. I have speed bleeders for the front now..... I will install them and go at it, and see if I can get it better.

I am not running the residual valve in the rear...... too many conflicting opinions if it is actually needed..... not ruling it out.....

67gtonut

02-27-2012, 02:41 AM

On a possible related note...... I noticed when I was bleeding the rear yesterday, I did have to add small amounts of fluid to the front res. of the master, not alot, but I did notice the fluid level would drop. I did not expect that, and do not know if this is normal.

I have been over the lines.... no leaks anywhere.

Pedal does not sink when system is closed up...... just a lousy pedal in my opinion.

Apogee

02-27-2012, 07:38 AM

67gtonut

02-27-2012, 07:46 AM

The Wilwood master cylinder has a hole through the divider between the reservoirs about 2/3 of the way up from the bottom, so you will see some fluid crossover when the level is above that point. Is it possible that's where your fluid is going?

I would expect a very low, somewhat squishy pedal with your brake setup.

Tobin
KORE3

Whew..... ok, that makes me feel better on that point....

OK.... what do I need to change to eliminate the squishy pedal?

Tobin.... I really appeciate your input.....

Apogee

02-27-2012, 08:39 AM

Happy to help in any way I can. Assuming everything is bleed within an inch of its life and there is no air in the system, the best way to firm up the pedal feel and reduce pedal travel would be to move to a larger bore master cylinder. The OE manual master cylinder for your application was a 1" bore unit, although I think you may be happier splitting the difference with a 15/16" bore unit, a 12% step versus ~25%.

If you go to a larger bore MC and like the pedal feel, but still can't achieve lockup with a reasonable pedal effort, the next step would be to look at your pads. Raybestos offers multiple compounds ranging from low CoF/noise/rotor wear ceramic options up to fleet-duty semi-metallics in their OE replacement options, so I don't really know what you're running now. Low brake torques can be a symptom of low CoF pads, glazed pads and/or improperly bedded pad/rotor combinations among other things, so pads can and will make a big difference in the performance of the system.

Tobin
KORE3

67gtonut

02-27-2012, 09:07 AM

Thanks Tobin,

I also just got off the phone with Wilwood.... That guy does agree with you as far as the 10lb residual valve would help greatly.... and he does also agree that the 7/8" bore wont ever give me a rock hard pedal..... it should give enough clamping force to lock the wheels.....

So...... it looks like a 10lb residual valve is in my future..... also thinking of picking up one of their adjustable prop valves...... since I have to open up the system again... ugh.....

it never ends.....

67gtonut

02-27-2012, 05:56 PM

OK..... installed Speedbleeders in front...... bled the crap outa them..... Pedal does feel better. But I am not gonna mess around.... I ordered the 10lb Residual valve, so I am not putting the wheels back on until its installed..... Oh how I loath cutting and double flaring brake lines....... lol

67gtonut

03-11-2012, 11:33 AM

Well, I installed the 10lb residual valve and just for the heck of it, swapped out my generic adjutable prop valve to a Wilwood one.....

Pedal is nice...... no complaints there....

But still cant lock the wheels..... new rear shoes and drums are still breaking in..... But cant lock the fronts..... Rayobestos Ceramic pads with a generic slotted/drilled rotor.....

Think I am down to a "friction" issue?

Apogee

03-12-2012, 07:12 AM

Troy, pads can a will make a huge difference, so it's definitely a possibility. If the pads you have now are "EE" rated pads with a CoF in the middle of the .25-.35 range at .3, then by changing to a "FF" pad in the middle of it's range (.35-.45) at .4 will give you a 33% increase in brake torque without any other changes.

67gtonut

03-12-2012, 04:59 PM

So......

EBC Yellow's

or

Hawk HPS's

any other suggestions....?

RSX302

03-12-2012, 08:27 PM

I've dealt with the "not being able to lock up" issue a few years back. Ultimately found that manual brakes do not work well on heavy street cars (>3500lbs) unless you do one or more of the following:
Disclaimer; I also have big sticky Toyo’s on a 3800lb car. Lighter car, set-up and smaller less sticky tires will lock-up sooner.

Yes pad Cf is a huge factor but...if the extra pad Cf doen't do it for ya here is more info. Ceramic pads are only for show because of no dusting. Not too good at stopping.

*Higher Caliper pressure (1000psi min..1500+ ideal based on 4sq in caliper) required for pad Cf below .4 (street pads)
I used Willwood’s BP30's (.5-.6Cf) on 13" rotors, SL6's and 3/4 master. That locked them up! Stopped the car perfect, (to my liking) but at the expense of major dusting, squealing and rotor degradation. Needless to say I removed them. Oh yea. pad knockback started on the rear rotors with the Ford 9” due to the small master. Now I'm using power assist with large 1 3/16 master and Wilwood BP10’s. (.4Cf) Will put you through the glass..and lock up if I so choose.

*Increase Pedal Ratio Currently running 4:1 power assist and have run up to 6:1 and 8:1 for the previous manual system to try and get more caliper pressure.

*Larger Diameter Rotors (i.e. 13 to 14" nets approx +10% rotor braking torque)

*Power brake assist Just a hunch, but if you don’t like the higher pad Cf’s to get your desired braking, you’ll be switching over.

Good Web Calc:
http://www.jakelatham.com/radical/info/brake_calculators.shtml

67gtonut

03-13-2012, 01:20 AM

Thanks for the reply....

Most of that I admit is over my head.....

Need to learn more about the pedal ratio thing.... But yeah, if better pads dont do it..... It may be time for at least a small booster.

a67

03-13-2012, 05:30 AM

Be careful with the pedal ratio, too high and there isn't enough stroke on the M/C.

As for pads, I was going to mention the StopTech Street Performance brake pads. Have them on two cars, the one with the vacuum booster and y-body standard C4 brakes they are great. Much better then the PBR pads that were on there.

On the car with the manual brakes and a 7/8" M/C, these pads are OK. Stop the car they do, but not quite good enough for me.

I am considering EBC Blue pads and the CarboTech AX6 pads. Although friction wise, the AX6 is closer to the EBC yellows.

Bob.

Skip Fix

03-13-2012, 07:01 AM

FWIW for comparison I looked at some old Bendix pads I have and the more street/organic are FFs and the semi metallics(rotor eating suckers) are EEs.

I thought '67 had a 4 piston front caliper on their disc systems,went to single in 68?

RSX302

03-13-2012, 07:43 AM

Be careful with the pedal ratio, too high and there isn't enough stroke on the M/C.

Bob.

Bore size to caliper volume will determine overall pedal stroke. Pedal ratio will add a little more pedal stroke just because you will be able to push the M/C harder with the same leg input. If you have a nice solid pedal on a 7/8 master with a 5:1 pr. Then going to 6:1 or 7:1 will be minimal stroke difference.

Apogee

03-13-2012, 10:04 AM

...Yes pad Cf is a huge factor but...if the extra pad Cf doen't do it for ya here is more info. Ceramic pads are only for show because of no dusting. Not too good at stopping....

True, in a way, however "Ceramic" in an of itself means very little. I can say that we hear numerous incorrect assumptions on a daily basis regarding pads, specifically "Ceramic" pads, and it's tough to separate hype and marketing from fact without either technical date, personal experience, or preferably both to back it up. For the most part, "Ceramic" pads are being marketed currently as the low-dust, low-noise, low-rotor wear option within most friction manufacturer product lines, optimally suited towards power-assist applications where those characteristics are preferred over initial bite and higher coefficients of friction and therefore brake torques.

Food for thought...every pad compound offered by Carbotech is technically "Ceramic", from their street compounds all the way up to their full race compounds. Similarly, Satisfied (http://www.satisfied.ca/), a Canadian friction manufacturer is the same way. Many friction compounds have upwards of 30 or 40 individual components and there is no regulating body that determines what you can or cannot call any given brake pad, so buyer beware.

Tobin
KORE3

a67

03-13-2012, 12:07 PM

Bore size to caliper volume will determine overall pedal stroke. Pedal ratio will add a little more pedal stroke just because you will be able to push the M/C harder with the same leg input. If you have a nice solid pedal on a 7/8 master with a 5:1 pr. Then going to 6:1 or 7:1 will be minimal stroke difference.

There is more to it then this. The issue is, will there be enough stroke to activate the brakes on one end of the car when the other end has a leak. IOW, you need to bottom out the piston on the leaking circuit before the good circuit will operate.

Had that issue with the car with the manual brakes on it. Previous owner had too high of a pedal ratio. Which in turn did not allow any braking with one of the circuits leaking.

Bob.

RSX302

03-13-2012, 12:18 PM

True, in a way, however "Ceramic" in an of itself means very little. I can say that we hear numerous incorrect assumptions on a daily basis regarding pads, specifically "Ceramic" pads, and it's tough to separate hype and marketing from fact without either technical date, personal experience, or preferably both to back it up. For the most part, "Ceramic" pads are being marketed currently as the low-dust, low-noise, low-rotor wear option within most friction manufacturer product lines, optimally suited towards power-assist applications where those characteristics are preferred over initial bite and higher coefficients of friction and therefore brake torques.

Food for thought...every pad compound offered by Carbotech is technically "Ceramic", from their street compounds all the way up to their full race compounds. Similarly, Satisfied (http://www.satisfied.ca/), a Canadian friction manufacturer is the same way. Many friction compounds have upwards of 30 or 40 individual components and there is no regulating body that determines what you can or cannot call any given brake pad, so buyer beware.

Tobin
KORE3

True..I'm sure over the years as like anything else, advancements have been made. I can only speak of past ceramics I've deal with. One in particular was rated only to 500deg with a .3-.35cf. (I no longer see in there lineup, so that may tell you somthing)

So in response, it would be best to state, make sure you pick the right pad for your application. Hard part for people is, what is the right application? For the most part, trial and error. Which is where you try and give the most info to help choose--Or confuse sometimes in my case..lol

67gtonut

03-13-2012, 04:41 PM

I thought '67 had a 4 piston front caliper on their disc systems,went to single in 68?

Originally a Drum brake car...... installed a 69+ Single piston style.....

I dont think I can mess with my pedal ratio.....

So I am going to search for a good pad to install

RSX302

03-13-2012, 09:09 PM

Originally a Drum brake car...... installed a 69+ Single piston style.....

I dont think I can mess with my pedal ratio.....

So I am going to search for a good pad to install

You can always modify pedal ratios..:naughty: but you should definitely try the pads first as they are the easiest and go from there. You will find out what you like or dislike.

67gtonut

03-14-2012, 01:25 AM

Yeah...... I know but I will leave pedal ratio alone right now..... seeing as the car is was a manual brake car, and I dont have an exotic setup at the moment.... cant see it being too far off.

The pedal feel is nice now, the car noses over pretty hard under severe braking................ it just feels like the car glides to a stop, so I look for a better/grippier set of front pads....

So for just a cruise night / around town muscle car....... do the Hawk HPS pads serve the purpose?

Skip Fix

03-14-2012, 08:50 AM

FWIW if you saw the other thread on friction for pads old Bendix organic pads FF and their semi metallics EE. But from what I remember when I used them the semi metallics were tough on that first morning stop and left ALOT of dust-ie rotor metal, on the wheels.

67gtonut

03-14-2012, 11:31 AM

I ordered a set of Hawk HPS pads....

I assume I can just scuff up the current rotors to remove any pad residue from the last set..... correct?

Skip Fix

03-14-2012, 06:28 PM

My Hawks do not have any notations on them as to coef.

RSX302

03-14-2012, 09:00 PM

I ordered a set of Hawk HPS pads....

I assume I can just scuff up the current rotors to remove any pad residue from the last set..... correct?

Many diffrent pads out there and the manufacture can tell you, but when in doubt, sanding the rotors will never hurt and always work. Also do proper bedding per manufactures recommendation.

67gtonut

04-20-2012, 03:34 PM

OK.....In my ongoing effort to figure out why I cant seem to get my car to stop like I think it should...... I think I need to invest in a Brake Pressure Gauge.

This one seems to be the best bang for the buck....

http://www.summitracing.com/parts/SSB-A1704/

58417

Anyone else have a kit they recommend?

Skip Fix

04-21-2012, 07:07 PM

So for you guys using these brake gauges-how do you get it bled? Is there not soem air in the adapter? My Longacre gauges coem with a T that has a bleeder at the top.

67gtonut

04-22-2012, 06:22 AM

OK.... think I found part of the problem.............

me.

Adjusted up the rear drums tighter..... switched back the Rayobestos pads ( didnt like the dust from the Hawks). Sanded the rotors and pads.... bed them in last night....

took car out today........ nice pedal....

and this time did a few panic stops.......... and really stood on the pedal. She stops pretty damn good, rears will now lock , fronts not yet, but it is close.

I think from driving cars all week with power brakes........... I am just not used to how much pressure it takes to lock up a manual brake car.....
I know it sounds stupid, but I think that is my issue.....

Has anyone else ever felt this issue? going from power brake cars 99% of the time to your manual brake "fun" ride.......

Ron.in.SoCal

04-22-2012, 08:19 AM

Hey Troy....thx for the early moring chuckle. 33 posts to figure out you're not stomping on the pedal hard enough :lol:

67gtonut

04-22-2012, 08:36 AM

Hey Troy....thx for the early moring chuckle. 33 posts to figure out you're not stomping on the pedal hard enough :lol:

Yeah..... I know...... but I am honest enough to admit it.....

Still cant lock the fronts, but who the hell knows, maybe the pads arent rebedded in enough yet.....

I guess its finally time to admit it............. I just dont like manual brakes..... been trying for years to blame the car, changing things, causing my own issues.....

So now to figure out what kind of power setup to go with.

Thinking a nice slimline 9" booster with a 1 1/8" master. Would like a complete setup, instead of piecing one together.

Glad I could provide the laugh, hopefully other will get a chuckle also...... lol

Ron.in.SoCal

04-22-2012, 09:22 AM

You've got a good attitude about it! Throw a hydroboost on it and don't look back...:cheers:

Fuelie Nova

04-22-2012, 09:55 AM

Troy
I went thru exactly the same thing on my 66 Nova, I mean the part about I just had to admit I didn't like manual brakes :) I installed a hydraboost and love it.
Tom

DarkoNova

04-22-2012, 01:38 PM

Yeah, I haven't driven my car in the last 3 years, so when I finally took it out for a drive I damn near rearended the guy in front of me on the freeway offramp. I haven't tried to see if I can lock the wheels up, probably will in the next few days. I wanted to get some Carbotech AX6's, but hopefully my current pads will be fine.

I never understood how you were supposed to use those brake pressure gauges, either. How are you supposed to bleed the system with the gauge there?

Fuelie Nova

04-22-2012, 02:27 PM

I found bleeding the gauge was the least of my worries, even with a little air I was desperately low on pressure.
Tom

67gtonut

04-22-2012, 02:36 PM

You've got a good attitude about it! Throw a hydroboost on it and don't look back...:cheers:

Read up some on the Hydroboost........... like to keep the engine compartment as clean looking as possible. Hydroboost does seem to lend itself to that, in the pics I have seen....
Will probably do a conventional vacumn booster.

RSX302

04-25-2012, 08:54 PM

Had a hunch you would look at power assist. I wasn't fond of the massive leg pressure either.

OK.... think I found part of the problem.............

me.

Adjusted up the rear drums tighter..... switched back the Rayobestos pads ( didnt like the dust from the Hawks). Sanded the rotors and pads.... bed them in last night....

took car out today........ nice pedal....

and this time did a few panic stops.......... and really stood on the pedal. She stops pretty damn good, rears will now lock , fronts not yet, but it is close.

I think from driving cars all week with power brakes........... I am just not used to how much pressure it takes to lock up a manual brake car.....
I know it sounds stupid, but I think that is my issue.....

Has anyone else ever felt this issue? going from power brake cars 99% of the time to your manual brake "fun" ride.......

I've dealt with the "not being able to lock up" issue a few years back. Ultimately found that manual brakes do not work well on heavy street cars (>3500lbs) unless you do one or more of the following:
Disclaimer; I also have big sticky Toyo’s on a 3800lb car. Lighter car, set-up and smaller less sticky tires will lock-up sooner.

Yes pad Cf is a huge factor but...if the extra pad Cf doen't do it for ya here is more info. Ceramic pads are only for show because of no dusting. Not too good at stopping.

*Higher Caliper pressure (1000psi min..1500+ ideal based on 4sq in caliper) required for pad Cf below .4 (street pads)
I used Willwood’s BP30's (.5-.6Cf) on 13" rotors, SL6's and 3/4 master. That locked them up! Stopped the car perfect, (to my liking) but at the expense of major dusting, squealing and rotor degradation. Needless to say I removed them. Oh yea. pad knockback started on the rear rotors with the Ford 9” due to the small master. Now I'm using power assist with large 1 3/16 master and Wilwood BP10’s. (.4Cf) Will put you through the glass..and lock up if I so choose.

*Increase Pedal Ratio Currently running 4:1 power assist and have run up to 6:1 and 8:1 for the previous manual system to try and get more caliper pressure.

*Larger Diameter Rotors (i.e. 13 to 14" nets approx +10% rotor braking torque)

*Power brake assist Just a hunch, but if you don’t like the higher pad Cf’s to get your desired braking, you’ll be switching over.

Good Web Calc:
http://www.jakelatham.com/radical/info/brake_calculators.shtml

Vegas69

04-25-2012, 09:08 PM

67gtonut

04-26-2012, 01:18 AM

Yeah...... still going back and forth on this now.....

Drove it for a little bit last night.......... by the way, the UMI stuff makes this thing HANDLE!!! ..... I am trying to get past the mental block about the pressure needed to woah this car down.... I love the clean look under the hood of the manual brakes......

Might stick this out for now......... It has a great pedal, but just need to recalibrate my head on pedal pressure.....

gsxrken

04-26-2012, 04:49 PM

Your post sounds familiar. I went from original power brakes to wilwoods all around and couldn't lock them up. Juggled masters, pads, vacuum reservoir, then went manual side by side CNC master cylinders with balance bar, never was happy with the effort or cold bite of the brakes. Did a gauge test and I wasn't getting more than 900psi without serious bend the seat effort. My daily drivers spoiled me too.
Finally bit the hydratech booster bullet... $$$ but I'm not posting about my brakes anymore. ;)

67gtonut

04-26-2012, 05:02 PM

Man, I am glad I am not alone in what I was/am feeling.....

How hard is a Hydroboost install? Can it be made to look neat?

I will do some searches on here.....

RSX302

04-26-2012, 08:16 PM

Manual brakes take some getting used too. It sounds really stupid(Ron) but it's hard to convince yourself to stomp on the pedal when most factory cars require your pinky toe. Manual brakes are a beautiful thing for threshold braking and high speed and road racing. I've grown to like them a lot more. You just can't use them like a daily driver. You really need to put your leg into them. It doesn't feel natural.

I agree..I love manual brakes for racing. I was trying so hard to make my manual system work, but when I was pushing so hard that I seriously thought I was going to break the pedal linkage or something (bending the steering wheel for leverage) I still couldn't get the car to slow let alone lock them up. This is when I started with pedal ratios, smaller MC's and more aggressive pad compounds to do the job. NASCAR style. Although the final result worked very well and to my stopping power liking,(medium-hard pedal pressure to lock) I wasn't going to live with the fact that it was chewing up the rotors, dusting horribly and squealing. I had to throw in the towel.

I drove my buddies GT3 Porsche and I was like, DAMN! this thing stops incredible.. Great pedal feel (easy-medium pedal pressure)and will launch you through the window. Imagine that--power assist with huge brakes. This is when I started looking at power assist. Yes, Porsche GT3's have aggressive pads too. Dusting and squealing.

Since most of our vehicles see 90%+ street use, we need to be comfortable with our brakes on the street. If I build a car for 90% track, it would most definitely have manual along with being 1000lbs lighter.

I have to say I'm very happy with the performance of the ABS Electric Power brake system (no plug intended) it has a very nice pedal feel both on street and on the track. Solid medium-hard press pedal--not touchy at all. Feels like manual brakes with great stopping power with Wilwood's SL6's and BP10's (.45cf pads & 4:1 PR)