jeffp1167

My 1990 has the 12" brakes and I was curious at what point of braking they start to fail. This will be more of a daily driver with probably not that much hard braking. I know the factory wheels limit a lot of preferred large brake swaps and I am undecided if I want to keep my stock rims or upgrade them as well on this project car.

Would the factory large brake upgrade be a better choice for my project or should I wait till I decide on what rims I want?

How do J55 brakes compare to C5 upgrade? If cost is not substantially more maybe I will just hold off till I decide on rims.

oldalaskaman

for daily driving, I think they are more than capable

Bronze85

ex-x-fire

Its not just the diameter, its the rotor thickness. This helps dissipate heat because the fins are bigger.

QCVette

The standard brakes on our cars already offers better performance than most cars on the road.

The upgrades to the J55 or C5 brakes make for a better system, but to me it seems like it costs quite a bit for the return. If you are planning some track days, or autocross, etc. the brake upgrades are needed for better stopping and fade resistance.

On my street cars I did not make the upgrades.

jeffp1167

By daily car ...

Grocery getting
commuting to work
occasional everyday hard braking

it might see something to do with track racing maybe 5 times in the rest of its life.

frenchyoliver

for hard fast stops, you get 10% less distance with the 13 compared to the 12.
Means, at 70 mph, it s about 3 cars lenght...

UNCLEBILL

I found with my 1990 Vert that the standard 12" were okay so to speak. I went with the Baer 13" 2 piston upgrade. I found a big difference in that the ABS works too easily now. The Baer rotors were drilled and slotted but what I found interesting was the standard rotors were about .840" thick while the Baer were 1.102" thick. Just like the above comment of heat dispersion; I agree. I went with this Baer system as it fit my Original rims.Im very happy with the results. You have to remember in my case as Im retired; when I was younger I just wanted to go faster but now I want to STOP faster

c4cruiser

For street use, the factory brakes will work fine. Pad selection plays a huge part in braking performance too. For track days, lots of C4 owners go with different pads for that day alone and change back to a street pad after the event.

When you change rotor diameter in the front, you may have to install the Doug Rippie Motorsports brake bias spring to change the bias (line pressure) between the front and rear brakes. I did that when I upgraded the front brakes on my 87 to C5 brakes.

Before swapping in the spring, I could get the ABS to activate with only medium brake pedal pressure, which was something like a medium hard stop from 35 to 0.

As far as the C5 upgrade, you will need a custom adapter to be able to bolt the C5 caliper mounting bracket to the C4 knuckle. The J55 brakes can be added to 88 and later cars with 12" front brakes using all GM parts.

0Brakemotive

The stock C4 12" rotors, as stated, are plenty capable of generating enough torque to lock the wheels up. One advantage to the larger 13" J55 and 12.8" C5 rotors that hasn't been mentioned is the internal vane design. They both feature a curved vane design which is much more efficient at pumping air through the rotor than the standard straight vane 12" rotor.

Simply installing a move out kit without correcting the brake bias (via line pressure or master cyl orifice size) on the front end will result in reduced pedal sensitivity. That may or may not be desirable depending on your driving style, but regardless the bias should be corrected to get the most out of the upgrade.

It was also mentioned above, pad compound has the most to do with how your brakes behave. If you running a no name parts store compound simply swapping to a better pad will give you the best bang for the buck.

dlmeyers

My 90 also has the stock brake system. I read some article about how that system was engineered so the driver could easily modulate the brake pressure. For street driving, I'd stick with original.

As a side note, bought my 90 with 34K on the meter. Today, 96K and I haven't changed pads, yet. Just checked them two day ago and they looked good.

I drive it like a stolen rental car.

Enjoy your ride.

dlmeyers
90 Coupe
zf6 3speed shocks
aftermarket floor mats

kenv

I have no problem with the stock brakes on either of my Vettes.

l98tpi

IMO, the 12" are fine for daily driver, autox low speed and high speed. Your over all brake efficiency will depend on brake pads, good brake fluid, proper system flush/bleeding, and tires. One other thing, if you are going to do anything more than street driving, stay away from the drilled rotors, they'll crack around the holes.

Toy90

I found the 12" rotors to be fine even for road course use as long as I had cooling ducts installed. For street driving the only way I found 12" brakes to suck was because the previous owner used some cheap pads. Once I added some Hawk HP+ pads it was like I added a big brake kit compared to the crappy pads that were on it before. The limitation to really fast stopping became my tires locking up, not the brakes. I could get the abs to activate on dry pavement with good pads and even good tires. There is a reason stock pads are not that cheap and it's not all the corvette tax. Put some $100 Wagners, Hawk, Carbotech or another quality pad and you will not be let down by your brakes with 12" rotors.

navy_vette

Honestly, the brakes can take a LOT of abuse. Unless you want to track it, the most i would to is have them slotted. There are a lot of places that can slot them, just be careful. If the end up cracking the rotor, you are going to end up buying a lot more that just new rotors.

jeffp1167

My friend has abutment plates and calipers from a J55 1990 vette. So converting would cost me very little actually. I was just wondering if it would be even worthwhile considering what my cars intended use will be.

Plus right now I have very little braking on this project car and the pedal for the most part goes to the floor. So figured since calipers and master cylinder and soft lines are most like shot now is the time to set the car up for long term braking.

But with wheel choice not made at this time is a J55 setup my best choice and C5 overkill? I also forgot to add I enjoy going up into the mountains a lot when I have the time and this will be the car of choice for that.

What other ideas do you guys have for making my braking nice as it can be without spending a 1,000.00 for after market stuff?

jaa1992

My experience with the small brakes was confined to an 88 that when I got it had the original brake fluid in it.
After flushing the fluid and getting rid of the crap pads, I replaced them with PFZ
Autocross speeds - it worked fine
Short road course (max speed for the 88 was around 100) - lots of fade as they got hot
Street driving - it was fine

anciano

OK, now I need an explanation of why a car stops faster with larger brakes, assuming the OEM rotor/caliper combo has sufficient grab to activate the ABS -- as mine do.

Since ABS modulates the braking power to stop just short of lock-up, the only variables are tires and the road surface. (Or do some C4s come without ABS? If so, I was unaware of that.)

Remember, the OP was asking about street driving, not track use. Nobody is going to be banging on their brakes repeatedly to the point of fade on the way to Safeway.

dizwiz24

I upgraded to j55 front brakes, stainless steel lines, BAER Eradispeed 13" slotted front rotors, a DRM brake bias spring, and EBC Greenstuff pads.

Even with this combination, they couldnt handle a single 90 to 0 stop, at the road course when I would slow down and turn into the pits. they would be completely faded out and worthless by the time the car would get down to about 15 to 10 MPH.

Can you guess what my weak link was?

Yes, the EBC Greenstuff pads.

I replaced them with Hawk HP+ and noticed a tremendous improvement in performance / fade resistance. Now, there is more dust and some squeaking when cold, but thats a separate issue.

I also noticed that the Eradispeed rotors were tremendously thick compared to what I imagine stock 13" rotors would be. My guess is they put more 'mass' in there for fade resistance.

One day, Id love to upgrade to C6 Z06 brakes. However, Id have to get rid of my 1996 grandsport rims and Id hate to do that.....

Tom400CFI

Less than 5 laps on Miller Motorsports park's full course.

On the street, they're more than sufficient.