Anyone have any Brake Questions?

[mlogdog]

I did check with him and they don't make any for that setup. Also I asked if they had plans to and he said no. So back to square one without spending 4k

[OG_Racing]

well your going to have a LSA motor. i would think twice about that brake budget. i almost could fit my hand into the intake port of a LSA motor.

[mlogdog]

Yeah true but but I'm only gonna have 6k in the entire motor I was trying to keep it as low as I could. Not trying to go cheap just use what's available new take offs and such.

[minendrews68]

OK, my turn.. On my '68 Camaro, I changed over to four wheel disc brakes. Nothing fancy just the generic setup. I thought I had my problem solved but changed something (I'll explain) and I've got my problems back. Here goes. When I first set my brakes up I had the brake pedal up even with the clutch pedal. all was good until I drove it around the block and after everything warmed up, my brakes locked up. Easy enough fix to get me back home was to relieve pressure at the master cylinder. After I got back home, I adjusted the clevis (which ties the brake pedal to the shaft coming out of the brake booster. This alleviated the problem but my pedal was about 1 1/2" below the clutch pedal. What was happening is as the brake fluid started to warm up it expanded causing the shaft in the booster to travel outward thus the pedal eventually hit the stop under the dash. At this point the expanding fluid could only cause the brakes to engage. How can I get the pedal up where it belongs, and have enough adjustment to allow for expansion? There is probably 3/8" between where the pedal sits at idle and where the brakes start engaging (no adjustment at all really) I could drop the pedal back down and wouldn't have any problems. Just looks crappy. Any ideas?
Thanks,
Carl

[OG_Racing]

OK, my turn.. On my '68 Camaro, I changed over to four wheel disc brakes. Nothing fancy just the generic setup. I thought I had my problem solved but changed something (I'll explain) and I've got my problems back. Here goes. When I first set my brakes up I had the brake pedal up even with the clutch pedal. all was good until I drove it around the block and after everything warmed up, my brakes locked up. Easy enough fix to get me back home was to relieve pressure at the master cylinder. After I got back home, I adjusted the clevis (which ties the brake pedal to the shaft coming out of the brake booster. This alleviated the problem but my pedal was about 1 1/2" below the clutch pedal. What was happening is as the brake fluid started to warm up it expanded causing the shaft in the booster to travel outward thus the pedal eventually hit the stop under the dash. At this point the expanding fluid could only cause the brakes to engage. How can I get the pedal up where it belongs, and have enough adjustment to allow for expansion? There is probably 3/8" between where the pedal sits at idle and where the brakes start engaging (no adjustment at all really) I could drop the pedal back down and wouldn't have any problems. Just looks crappy. Any ideas?
Thanks,
Carl

Carl,
This is a good example of putting the horse before the rider. The main problem I see is not your pedal location. It’s that your brakes are locking up. One thing I need to make clear is the “expansion” of the brake fluid. I’ve worked with some of the top teams in motorsports, my colleagues literally encompasses every form of Professional motor racing (NASCAR,WRC, Indy car, V8 supercars, ect..). I can tell you this with 100% certainty DOT 3 & 4 the fluid cannot expand to the point that it will engage your brakes. If you had a ton of drag in your system if the fluid will get hot, lose compressibility, boil, and fail. The outcome would be opposite of what we have here. So let’s move on from that.

It sounds as if your master cylinder is not releasing the pressure in your system. When you release the brakes some residual pressure is being trapped in the lines. Proof of this is the “cracking of the line” method you used to fix the locked up brakes. My recommendation is to replace the master cylinder. FYI I Have seen brand new master cylinders fail in this way. When adjusting your pedal make sure the cleveite that attaches the booster to the pedal has zero tension at rest. If you tap it, It should almost dance on the pedal assembly.

I hope this helps,
Johnny C

[minendrews68]

I see what your saying. Although, when the pedal was adjusted downward to where it was about 2" from the stop under the dash, I never had this problem, brakes never locked up. Right now, when I drive for a short period, the brake pedal moves against the stop. This in turn makes the fluid find another less resistant path. As it is there isn't enough travel in my pedal and booster rod. When adjusting the rod to the clevis, the rod turns. Does this rod just turn free in the booster or is it actually threaded inside the booster? I need more play in the rod adjustment I think. The only reason I'm in question is that when the pedal is lower (away from the stop under the dash) I don't have this problem. Also as I have it now, the pedal travels about 3/8 of an inch before the brakes start working. I hope I haven't made this as clear as mud for you..
Thanks for the help so far ...

[OG_Racing]

I see what your saying. Although, when the pedal was adjusted downward to where it was about 2" from the stop under the dash, I never had this problem, brakes never locked up. Right now, when I drive for a short period, the brake pedal moves against the stop. This in turn makes the fluid find another less resistant path. As it is there isn't enough travel in my pedal and booster rod. When adjusting the rod to the clevis, the rod turns. Does this rod just turn free in the booster or is it actually threaded inside the booster? I need more play in the rod adjustment I think. The only reason I'm in question is that when the pedal is lower (away from the stop under the dash) I don't have this problem. Also as I have it now, the pedal travels about 3/8 of an inch before the brakes start working. I hope I haven't made this as clear as mud for you..
Thanks for the help so far ...

I got ya Carl,
Without the car in my hands i cannot diagnose it 100%. i can tell you something funky going on if the pedal travels towards threw-out the drive. it's something inside the Master cylinder/booster. normally at rest the pedal assembly will be held to the stop by a spring, the booster's Push-rod needs to be at Zero tension. it is normal for their to be slack in the pedal with a Booster. so that information isn't setting off red flags for me, you are more familiar with the system then i am. If there is more play then normal that could be a sign of a failing booster. if i was going to bet $20 it would be on the master cylinder is not releasing pressure like it should. i would pop it off the booster and see if it is leaking.

[minendrews68]

ok I'll try to do that this weekend. Yeah, it's got me stumped. with the clevis loose from the pedal, I would think there should be some play there. It doesn't move maybe 1/4" in and out. Now I'm wondering if maybe the pin may not be situated in the booster correctly.

[Gil]

Hi Johnny, thanks to share your knowleges...

I have a firebird 69 with stock front rotors & calipers & stock master cylinder. For the rear, previous owner built an home made discs setup with French car Citroën XM calipers & BMW 525 touring front rotors. I drive it as a street car only.

What can I do to brake better without spending too much money as it's a tight budget build ?

Proportioning Valve ?

Rotor swap ? What can I use to replace the special 69 rotor with the "outside" hub ?



with this kind of rotor, I'll have to re-instal the hub on top of the rotor ? http://www.summitracing.com/int/part...model/firebird

with this kind, is it a direct swap without mods, as thickest from rotor to wheel face they have the hub inside ? http://www.summitracing.com/int/part...model/firebird


C5/C6 front rotors & calipers if I can find local used parts ? Is it an easy bolt in swap ? But must go 17" wheels...

Sorry for these noobs questions but I'm a bit lost with the front setup

Thanks a lot
Gil

[OG_Racing]

Hi Johnny, thanks to share your knowleges...

I have a firebird 69 with stock front rotors & calipers & stock master cylinder. For the rear, previous owner built an home made discs setup with French car Citroën XM calipers & BMW 525 touring front rotors. I drive it as a street car only.

What can I do to brake better without spending too much money as it's a tight budget build ?

Proportioning Valve ?

Rotor swap ? What can I use to replace the special 69 rotor with the "outside" hub ?



with this kind of rotor, I'll have to re-instal the hub on top of the rotor ? http://www.summitracing.com/int/part...model/firebird

with this kind, is it a direct swap without mods, as thickest from rotor to wheel face they have the hub inside ? http://www.summitracing.com/int/part...model/firebird


C5/C6 front rotors & calipers if I can find local used parts ? Is it an easy bolt in swap ? But must go 17" wheels...

Sorry for these noobs questions but I'm a bit lost with the front setup

Thanks a lot
Gil

Morning Gil,
let me start off with a question. when you say "brake Better" what aspect of the brakes are you looking to improve. Braking aspects of pedal fee, changing pedal pressure required to stop, stopping distance, and/or longevity. i could start you down a path or shortening your 60-0, but if your looking for an effortless stop, then we are barking up the wrong tree.
for the record the french brakes thing in the rear is scary. could you imagine the looks you'll get at the auto parts store when you say you need brakes for a Citroën XM.

[Gil]

Thanks for the quick answer !
"brake better" should be : Add bite & quicker stops.
(I have also original brake booster).

I know sound scary, but looks also... as one of the caliper is upside down... I'll post pics later when back home so you can see the rear brakes... Also it's not braking bad...

Did you Google a Citroën XM ? ugly as hell...

Don't really know what to do but change the rear full brakes...
But they did some molds & weldings to addapt these stuff.
Will cost a kidney to have a nice US made setup...

BRB
Gil

[OG_Racing]

Thanks for the quick answer !
"brake better" should be : Add bite & quicker stops.
(I have also original brake booster).

I know sound scary, but looks also... as one of the caliper is upside down... I'll post pics later when back home so you can see the rear brakes... Also it's not braking bad...

Did you Google a Citroën XM ? ugly as hell...

Don't really know what to do but change the rear full brakes...
But they did some molds & weldings to addapt these stuff.
Will cost a kidney to have a nice US made setup...

BRB
Gil

Gil,
Alright gill we have a goal of finding more bite and shorter stops.

Bite is a characteristic of the Pad fist coming in contact with the rotor.
There are two ways to influence Bite.
1, the pad compound itself.
2, the slots style on the rotor.

Generally in racing I want to see a “low initial bite” as this aids in keeping tire cohesion. For your application being on the street and not taken to the limit then a high bite wouldn’t hurt the performance much. The Pad I would recommend is the hawk HP+ pad. Hawk has a very high initial bite and should get you to your goal. The slots on the rotor can effect bite Slightly. It’s results are far less noticeable then bite produce from a pad compound. NOTE I said Slots and not holes. Never use drilled rotors. They have been proven time and time again to decrease performance.

Out of the rotors you provided I would go with the speed stop. Avoid the ssbc Drilled rotors. I find it amazing they can make a rotor for the same price, include a hub and bearing, and have it be similar quality as the speed stop.
If you were looking to spend a bit more I would recommend a Frozen rotors slotted application, they retail for 185 each. I Have the pads and rotors, shoot me a pm if you want me to get you a set.


To make the stops quicker .
Shorter stops come from a balanced system. Having the correct amount of Tq where you need it. The problem here will be with the old school European calipers. I know almost nothing about them. Also finding a performance pad to match the front will be difficult, if not impossible. I found some rear disc options from right stuff @ summit. http://www.summitracing.com/parts/rs...a/instructions. These kits use the older GM calipers. Those I do have pads for if you were looking to make a change.

I do have an American made PFC brake kit for your chassis. It’s the “little” Zr34 kit and it retails around 4k F and rear if you were looking to make the investment. They will need a 15” steel wheel, or a 17” aluminum wheel.



Johnny C.

South East Field Representative
Office: 1-800-934-9112 ext 124
Direct: (770)-880-7579

[Gil]

Thanks for all Johnny,

I think I have another problem with the rear end...
Seems previous owner cut the flanges & weld another one to adapt the calipers...
Why doing that instead of buying a bolt-in kit ??







I'll have to change the housing when ready to change the brake kit...
Wasn't difficult enough...

Gil

[OG_Racing]

welding the brake caliper flanges is fairly normal operation and often a cheap option.

i did find this with my searching a 9" housing with floating axles for under $1000 .
http://www.colemanracing.com/9-Float...t-7-P4646.aspx

[Gil]

May be still possible to cut and weld the right rear axle housing ends and rebuild this one with new bearings, or find locally another 8.5" 10 bolt housing to transplant all in ?
Gil

[OG_Racing]

May be still possible to cut and weld the right rear axle housing ends and rebuild this one with new bearings, or find locally another 8.5" 10 bolt housing to transplant all in ?
Gil

my guess, sourcing a new axle would be the easier. heck... see if you can find one that came with the factory rotors.

[Gil]

Thanks a lot for all your answers,
I think i'll find one, seems easier, I don't see me cutting & welding the housing...

one last question...

with the speed stop front slotted rotors, I'll have to mount the hub back on it ? hub is bolted on the factory rotor ?

Thanks
Gil

[OG_Racing]

Thanks a lot for all your answers,
I think i'll find one, seems easier, I don't see me cutting & welding the housing...

one last question...

with the speed stop front slotted rotors, I'll have to mount the hub back on it ? hub is bolted on the factory rotor ?

Thanks
Gil

I have no idea. i haven't worked with speed stop before. I used speed stop on the rear of my nissan Z car and they have held up for quite some time.

[jaybee]

Carl,

I don't have the expertise of OG, but I have a thought on your issue. With your pedal adjusted high, does the piston in the M/C travel back enough to uncover the holes between the cylinder bore and reservoirs? If not you'll certainly carry some residual pressure and drag the brakes.

[JustJohn]

I am converting my 69 Impala over to rear disc brakes this winter. I have the factory 12 bolt rear end but have been told it is identical to the truck rear end rather than the car version. Are there bolt-on options that let me retain a parking brake?

Front brakes will be C6 Corvette calipers/rotors.