redtopz

Sounds like you have air in the system. One thing's for sure, it's not the Castrol SRF. That's the best stuff you can get.

Try Hawk 70 front and 60 rear. There are many other pads, but Oli, Chuck, Jim and I have run those with no issues for years so they should work for you too. One thing about the Hawks, they can handle a lot of heat. Do you have good cooling ducts forcing air through the center of the rotors? My pads are lasting half a season.

We used PFC-08's on our 25 hour of Thunderhill bmw and one set lasted the entire race. I thought they were excellent pads, very progressive and easy to modulate. We were on hankook C51 tires. Maybe you guys have a separate brake issue?

johnny c

my guess is the tires. alot of the 200 qutg tires can last a long time. the compound (friction) could of given up the ghost, but it has plenty of tread left.

tmtraylor

Thanks for the input. Additional brake issue(s) is certainly a possibility. The car is a previous chump racer that is new to us. We are constantly learning and "uncovering" surprises in every system.

2Laidback

I planned on swapping pads but I wasn't sure about swapping rotors once I upgrade those. Are the Hawk pads going to be as long lasting (in the same situations) as the AP or PFC types. I don't know if they have racing only or have both street and track?

Do you think it is worth the time to install the "Z51 disc cooling rings" or will it be fine if I have proper pads on it?

SBC_and_a_stick

Super. Thanks!

Soloontario

New question. I had heard numerous times that a brand new cheap one piece rotor will last longer if you "condition" it by some street driving and running through a few heat cycles. If this is true does the same apply to better floating 2 piece rotors?

JRitt@essex

You should always 'condition' new discs when you install them. That applies to any disc...OEM-style, 2-piece racing style, and even CCM. Conditioning is called burnishing or bedding-in. Our engineering director designed and built a machine that we use to do this for professional race teams all over the world. Both the machine and process are now patented. You can see details here. We offer this service to anyone buying our 2-piece AP Racing discs or our AP Racing Competition Brake Kits. The nice thing about having bedding done on a machine is consistency. We can achieve the perfect results every time, whereas when you try to do it yourself, it can be a hit or miss, particularly your first time.

Regardless, I created a video on bedding in discs several years ago in my C5Z06: How to Bed-in / Burnish Brake Discs and Pads

Any disc is going to last longer and perform more consistently if it is prepared properly prior to heavy track use. All of our pro racing discs go out the door burnished. Teams don't have the time mess around with this sort of thing at the track, and drivers certainly don't want to do it. Time is money to them, and they want to hop in and go!

JRitt@essex

Hawk DTC-70 and DTC-60 race pads are decent, but not the top of the heap in terms pad choice (I have nothing against them, and we actually sell them). On our dyno we've seen that they tend to fall off in terms of mu at around 1300 degrees F, and they can also cause grooving when run hot. In NASCAR Sprint Cup, they aren't even a consideration, since they can't handle the abuse dished out by those cars.

The Z51 cooling rings are a waste of time. IMO, they were an afterthought, and aren't particularly effective. I did an analysis of the OEM C7 Z51 brake system when we first bought our C7 test mule. The brakes really aren't a great match for the capability of the platform. The OEM discs don't flow enough air to be effective at their size, and the cooling rings are an ineffective band-aid.

If you plan to track your car for the next few years, I'd suggest investing in our AP 2-piece J Hooks. You will save a lot of time, money, and headaches vs. OEM-style discs. They will run much cooler, last far longer, and even shave a few pounds unsprung weight. Your pads will also last far longer while running them, and you'll be less likely to boil brake fluid. IMO, they're one of the biggest 'no-brainer' products we sell for Corvettes.

Also of note...legendary Corvette engineer, racer, and guru John Heinricy just gave us some really nice feedback on our 2-piece AP Racing discs for the C7 Z51.

Soloontario

I understand the pad bedding in and transfer layer but was asking about the heating of the rotor alone i.e does the metal itself become tougher if it runs through a few mild heat cycles or maybe even the old style cryo treatments. I have tended to put any new rotor through a couple of months of street driving before bedding in race pads and using it at the track and yes I think I am pretty good at removing the old street pad transfer layer first.

FarmerSid

Need new flex lines front and rear for C4 IFS and IRS I have under my 51 chev pickup frame. Need some help on selection.

Cheers!

johnny c

hit up kns brakes or essex parts they should have some braided stainless lines.

daleong

Hi Jeff - appreciate all the insight you have provided in this thread. Any downsides (apart from the cost) of running the AP J-hooks exclusively on the street? Just overkill?

FarmerSid

Been searching for new flex lines for my project. I don't have flex lines on my 2 front and 2 rear stock C4 calipers. I think I see that stock all 4 have banjo ends on them and some are bent. Looking to go with SS braided and not stock replacements. Can the banjo ends be straight or do I need bent ones?

Should I be going with a different type? No brake lines have been ran so the hard line to flex line brackets can be welded where needed.

Any insight?

johnny c

i can't tell you exactly what needs to be done on a c4 with stock calipers. but braided lines are never a bad idea. they flex a heck of a lot less then the rubber ones that come stock. you should notice a firmer pedal with a good set of braided.

as far as what brand I've always used goodrige with good result. that's the same lines PFC sends out with all brake kits. we only had one failure and that was on a prototype army special forces suburban. it had mid boggling line pressure. thousands of race cars never had an issue.

johnny c

street use, a good set of Motorsports rotors with excellent metallurgy might outlast the vehicle.

jaa1992

Goodridge(or goodrich - can't remember which is the right name) has stainless braided lines for c4 stock brakes.
I went with Earls, but I don't think they sell them anymore

I tried the goordridge before I went with the earls, and had a hard time keeping them from rubbing on the wheels. The earls were almost an exact fit. The goodridge would be a solution for you since you probably move things around to avoid the issues I had.

johnny c

the season is uppon us. anyone have any issues?

SBC_and_a_stick

Which is a better system for bringing air to the rotor through a flexible hose:
a) front inlet mounted in the bumper fascia
b) wishbone mounted inlet drawing air from the bottom of the car

2Laidback

LOL, I found out after changing out brake lines to SS and fluid that there are 2 bleeders on each piston, not just the outside one, lol. Never saw that mentioned anywhere until I looked into my mushy pedal!! Good Times! Lol

johnny c

front inlet is going to move more air, but have more overall drag.

bottom inlet will move less cfm of air, but removing air from under the car will have less drag, and might increase front down force.