High HP brake advice please

[1sikride]

Hey guys..
71 Chevelle. Built ls3 supercharged.
700hp...

I have “right stuff” 4 wheel disc brakes
on it now.

City driving they stop fine.

took the car to a drag strip.
I could barley brake in time
afted I passed the finish line
before I would hit the wall.
I over shot the turn off/back lane
every time...brake fade was bad.
Pretty much ruined my night as I
was afraid to drag as hard as I know the car can

question being..

is a 6 piston caliper needed?
or is it the big disc I need ?
13” with a 4 piston?

12” with a 6 piston ?

i see a guy with a wilwood kit
4 piston 12” forsale on here...
is that a huge upgrade or meh

thanks so much.

[andrewb70]

How fast were you running? Fancy breaks are not needed for the drag strip. I've seen 9 second cars using stock breaks.

I suspect what you have now is not working well. Start diagnosing the problem.

Andrew

[Shawn0331]

How much material is still left on your brake pads? Common brake fade is caused by not having enough material for heat to dissipate or gas if over heated. Wouldn't hurt to try a really good set of track pads before investing in a whole new setup. You will be surprised at what just upgraded brake pads can do. With that being said though if you had plans on upgrading you whole setup anyway then i would get the 4 pot willwod setup you mentioned.

[andrewb70]

From what he described, I seriously doubt that the problem is break fade. I've done a lot of drag racing and fade is not a problem, because using the brakes once just doesn't heat them up that much!

Andrew

[Shawn0331]

yea i was replying with the idea he had decent initial bite then faded away as he passed the exit due to low material left on the pads (really easy to check for start of diagnosis). but you are right about them overheating that fast. Most likely is due to malfunction somewhere else with the setup not creating enough force.

[1sikride]

The whole brake system has
Only a couple thousand km on them.
So it’s not a low worn pad.

And I just simply couldn’t brake fast enough.
I had my foot into the floor
And each additional pass it was harder and harder
And I waited 10m per pass.

I did 118mph.

[andrewb70]

I still stand by my original assessment that there is something wrong with your current setup.

Andrew

[raustinss]

Drew does the chevelle have new rubber caliper hoses or are they crazy ass old hoses , my suggestion is make sure the caliper hoses are new and a braided steel hose . Also flush out all the old fluid and replace with new

[dhutton]

Power brakes? If yes, where did you connect the vacuum line? Is the check valve working? What size is the booster? Post up a pic.

Don

[eville]

Having brake problems and we get more details about engine than brakes.
What right stuff kit. What master. Power or manual. What pads.
Tell us the important stuff and we can do more than guess.

[TheJDMan]

Agreed, you need to provide a lot more specific detail on the brake setup.

[raustinss]

I have his number ... sent him a message , hes probably too busy playing with guns .

[1sikride]

158012


I didn’t install the kit.
It’s about 3yrs old
With 6/7xxx km on it.
Steel lines.
4 wheel disc.
Power.

The master came in the kit too.

And like I said... in town I’m fine.
It was after a drag run when I had
To get on them hard coming down
From 120mph I kept over shooting
The turn back lane and I washed out
20 ft from the barrier lol.
Just made me think...hmmm...
Bigger brakes.


I don’t remember the kit. Pads. Name. Etc.
I paid about 2k cdn for it all.

[dhutton]

Check your booster check valve....

[Peter Mc Mahon]

What if you got on the brakes hard on the highway? You said it’s fine in town (going slow) but it’s not fine going fast ( drag strip )

[1sikride]

I haven’t needed to ram on them
Hard on the highway.

I’m just a little cheesed bc the strip
That’s closest, they have a small
Cool down lane...and I don’t want to keep scaring myself when I go there

[andrewb70]

Dude...time for some testing. Next time you're on an open highway and no one is around, lay on the brakes as if it was a panic stop... Report back.

Andrew

[jetmech442]

1sikride,
I started out with the same generic kit, but from CPP. The most common kit provides you with a 1 1/8th Master cylinder, Front D52 Iron calipers with 11' rotors , D154 GM "Metric" rear calipers and an 11'' booster. Stock form actually provides pretty decent numbers even with street pads.

My first thought is that you may have bled the brakes not exactly right. If you don't have that pin installed in the combination valve, then when you "pump" the pedal, it moves it forward and seals off either the front or rear brakes forever until that pin is reset. I can't quit tell from the pic if your brake warning switch is wired up or not, that would be an indicator the combination valve needs to have the pin re-centered. You can google "Combination valve metering pin reset" and there are several youtubes to help.

If that is fine, tell us what your idle vacuum is, ensure the check valve is working on the booster, also make sure the booster rod is attached at the lowest hole on your brake pedal arm. It sounds to me like a force issue, so if you don't have enough vacuum, you'r not multiplying your leg force enough. If the check valve is dysfunctional, same thing. If the pedal is in the "Manual" brake hole(top) instead of the bottom, less force again.

I just took my Cutlass to Blackhawk Farms Raceway last month with essentially the same setup but with Wilwood track pads for heat. Pulling down from 107mph on turn 1 for 20 laps at a time(plus other turns), and the car never flinched. Like Andrew B said, you've got a troubleshooting issue---unless your trying to justify to the wife that you need some 13'' Bremebos, in which case...I can back you up on that lol!

Let us know what you find, good luck man.

[jetmech442]

Hey guys..
71 Chevelle. Built ls3 supercharged.
700hp...

I have “right stuff” 4 wheel disc brakes
on it now.

City driving they stop fine.

took the car to a drag strip.
I could barley brake in time
afted I passed the finish line
before I would hit the wall.
I over shot the turn off/back lane
every time...brake fade was bad.
Pretty much ruined my night as I
was afraid to drag as hard as I know the car can

question being..

is a 6 piston caliper needed? All of the 6 piston Wilwoods that I just looked through actually reduce piston area by nearly half, so without altering the whole system, those would hurt your performance significantly.

or is it the big disc I need ?going up 1'' in diameter roughly increases braking torque at that tire by about 125lbs. Rotor diameter is not your issue, big rotors look waaay cooler,
trust me if I could afford them I would put on the biggest 13'' rotors I could find knowing the performance gain would be minimal.

13” with a 4 piston? Currently, with Wilwood BP pads(.45), 1 1/8th MC, D52/D154 calipers the front braking torque is 2616lb-ft. Moving from an 11'' to a 13'' only increases it to 3091lb-ft. This difference is not going to all the sudden put you through the windshield. Plus, the 4 piston that i found also reduces piston area from 6.3sq in to 5.18 sq in, so again, it would not help without changing the whole system. FYI, my calcs are from my excel spreadsheet that I think is suitable for A to B comparisons. For someone that needs dead nuts accurate tire force numbers, I would suggest Ron Suttons company, 50 bucks and you get a system that eliminates all doubt and errors from some random internet guy(me!).

12” with a 6 piston ? same story

i see a guy with a wilwood kit
4 piston 12” forsale on here...
is that a huge upgrade or meh

thanks so much.

I forgot to mention a few things, sorry for the double post...
The rear D154 calipers are the biggest PITA to properly setup with the integrated parking brake. There is a dude on youtube with a 20 minute video, who takes it all apart and properly shows you everything you need to do to get it to setup right. I can't stress enough how important this is for an immediate, firm pedal, otherwise you will bleed and bleed to no avail. ALSO-I saw you post below about setting up the parking brake. The rear calipers ONLY adjust if you use the parking brake, so after several thousand km, the pads have worn and now that distance must be taken up by pedal travel EACH time. But they will only adjust when you use the ebrake IF they are properly adjusted before mounting them. The calipers are good and cheap and have just a little too much piston size for the rears(proportioning valve needed IMO), but getting the adjustment right is key.

I hope this helps. and if anyone finds my opinion/suggestions to be incorrect-please do the right thing and correct me so we can save another dude from spending big money on the wrong system.

[NOT A TA]

As I was reading through the posts I was thinking rear brake not set up with parking brake functioning and properly adjusted, then jetmech442 covered it. So I'm in agreement that the rear brake adjustment and parking brake set up should be looked at. The brakes will not work properly unless the rears are adjusted and park brake cables adjusted properly then used occasionally. I've seen the same symptoms on other cars. Those brakes should haul the car down from 120.

[1sikride]

Wow - fantastic info...

Car is put away for now...
I will start there first and then report back in a
Bit!
And from what I remember there’s been
Issues installing the brakes initially...
And after the upgrades....
Thx guys