When are brakes too big?

[Huzzah!]

I've been bugging the crap out of a few vendors while trying to decide of what brakes are right for my car. I have a 74 Nova that currently has drum/drums on it and stopping apparently wasn't an idea when they made this car because it doesn't. I'm looking to make the car an everyday driver if I choose but also be able to stop well enough. To take it through the twisties or autox it. I had a soft spot for 14" brakes but my wallet is in love with the smaller sizes. What would suit my needs for a front and rear kit? I don't have a set of wheels picked out currently as I will be determining that later. Thanks!

Ben

[MuscleRodz]

when they won't fit in the wheels!

realistically, 11" 4 wheel stock disc will handle everyday driving fine. Larger sizes are required when your plan is to abuse them, or you just want to look at them. I actually like to do both. 14" brakes also require 18" wheels and tires, so cost of change is compounded.

[68sixspeed]

depends on what you are doing... for drag racing most of our brakes are way too big. I've seen a few z06's where the 14" brakes were swapped out for the base c6 vettes 13" brakes for drag racing, dropping a couple tenths in quarter mile time. For auto-x a 14" is overkill too. For road course, I'd consider 12" a minimum. 13-14" seem to be in the sweet spot. 15" require some pretty big rims and the rim and rotor inertia starts getting high. Even in the 14"... watch the weight. stock z06 rotors are 28 pounds each for the front, wicked heavy. 2pc rotors can save 10lbs per side on the front.

[Huzzah!]

depends on what you are doing... for drag racing most of our brakes are way too big. I've seen a few z06's where the 14" brakes were swapped out for the base c6 vettes 13" brakes for drag racing, dropping a couple tenths in quarter mile time. For auto-x a 14" is overkill too. For road course, I'd consider 12" a minimum. 13-14" seem to be in the sweet spot. 15" require some pretty big rims and the rim and rotor inertia starts getting high. Even in the 14"... watch the weight. stock z06 rotors are 28 pounds each for the front, wicked heavy. 2pc rotors can save 10lbs per side on the front.

Drag racing would only be done for fun; nothing serious. I guess I'm just afraid of going to small and regretting it. I've spent too much money in the last ten years and its still a pos. So I'm just trying to get this project done right this time. Lol

[79-TA]

Bigger brakes do a couple of things better or differently than smaller brakes.

Bigger brakes:
- weigh more
- have a greater acting radius, increasing braking torque for the same amount of pedal/pad pressure
- have a greater amount of surface area to dissipate heat, so they can operate at slightly cooler temperatures while dumping the same amount of heat
- last longer because of the lower temperatures, lower amount of force required by the brake pad, and more material sharing friction duty
- fill the wheel with a nice backdrop to look at while preventing you from running whichever smaller wheel sizes

On my own car, I run stock sized brakes, though they are slotted rotors with good Hawk HPS brake pads. The car does not lack for braking power nor does it have fade issues, at least not for the short track sessions at RTT type events. It actually managed an 11th place overall finish in the speed stop last year at RTTC2 and at the Hotchkis NMRA/NMCA speed stop, it beat every single late model muscle car (this excludes Bruce Cambern's Ford GT.)

No matter what brake system you choose, pads, steel braided lines, and fluid that won't boil will make a huge difference. A bit bigger than stock wouldn't be a bad place to be, especially if they still fit in a nice set of 17" wheels. In your case switching from drums all around, it'll be huge. You'll have to deal with brake proportioning and such too, but I guess whatever kit you get will have provisions for that.

[John Wright]

You can probably find some 11 or 12" stuff that still fits behind a 15" wheel if you are locked in to that, however stepping up to a 17" you can use the C5/C6 stuff and really seems to be an economical way to go for better all around brakes, except for having to purchase new rims and tires. I swapped over to the C5 stuff a few years ago and bought the 17" Cragar Steel truck rims at $60/rim with a Sumitomo Z rated tire to get me by until I can do better. I think the prices may have gone up a few dollars since then, but they are heavy, not as pretty and a heck of a lot cheaper than shelling out 3 to 4 grand on rims and tires.

[silver69camaro]

Personally I would like to see more people run a 12 to 13" brake rather than 14", even on track-day vehicles. Our cars aren't as heavy as OEM cars that run 14" brakes, and keeping overly-large rotor hot enough for HP pads is tough with big rotors during street use. I'd rather have a smaller rotor with ducting. IMO a 13" rotor with a 17" wheel makes good sense for 98% of us.

[Bryce]

I am currently building a spreadsheet that will calculate brake torque due to rotor size and calipers (piston area and pad area) and moment of inertia and total weight. This way people can make an educated desicion.

[ace_xp2]

Instead of having trouble running a hotter pad, couldn't you just run a colder one? Then you'd keep the response up and save those bigger rotors even longer. There's actually a post over on Corner Carvers where someone with a classic mustang with 14" rotors couldn't get the track pads up to temp. It didn't occur to me that that was a problem though, I just figured you could then get away with a less aggressive compound.

[novaderrik]

i loved the 12" C4 Corvette front brakes that were on my 71 Nova. i had 2 different sets of 16" wheels on it (IROC, GTA)i could even fit some early 70's Z/28 15" wheels over them with a little room to spare. the stock steel 15" wheels from my 74 Monte Carlo didn't clear and i had to try a few different junkyard mini spares to find one that fit- i think the one that actually fit was from a mid 80's Caprice that had the extra benefit of being made of aluminum.

i had it set up with a manual master cylinder for a 77 Malibu with manual brakes, and used a Wilwood adjustable prop valve for the stock rear drum brakes that i plumbed inline after the stock drum/drum prop valve. the pedal effort was perfect- not too easy, not too hard- and no one ever had any problems driving the car or bitched about the pedal effort.

once i got the prop valve dialed in, the car just flat out stopped without any drama and i could do repeated hard stops without any issues. the car would literally just crouch down and stop while my seatbelts did everything they could to keep me from becoming one with the steering wheel and there was no drama of any kind in heavy rain or even that one late October ice storm i got caught in. i never raced it in any way, but the brakes were at least as good as any later model car i've ever owned and i had about $500 into the swap using all GM replacement Vette parts.

[John Wright]

I am currently building a spreadsheet that will calculate brake torque due to rotor size and calipers (piston area and pad area) and moment of inertia and total weight. This way people can make an educated desicion.

Bryce, I can't wait to see what you come up with. :thumbs up:

[Huzzah!]

I'm leaning towards the baer track 4s or the wilwood 6 piston 12.19. I'm thinking either would be a good choice. Any opinions?

[cheapthrillz]

I am currently building a spreadsheet that will calculate brake torque due to rotor size and calipers (piston area and pad area) and moment of inertia and total weight. This way people can make an educated desicion.

Kind of like this one: http://www.jakelatham.com/radical/info/brake_calculators.shtml

[Bryce]

Yes similar, I want to check his math. But my spread sheet would be designed so as you populate the rows it adds to the data, and everyone can benefit. I will have something in a few weeks.

[Nothingface5384]

I currently run stock 11in rotors with d52 dual piston wilwood calibers and 95 impala d614 pads for front and rear right stuff detailing disc kit qhich consists of 11in rotors and d154 pads.
absbrakes.com 9in dual diaphram power booster and corvetter disc/disc ms/porp valve

works really well! may try slotted/drilled rotors witrh hawk pads next time round
the rears fit my stock 14 sttellers and various 15s i had around..some guys sayyed theirs didnt exaclty clear 14s or 15s but I believe they didnt use the correct caliber shim that came in the kit.

front works with 15s havnt tried it on 14s though ...will if you want to, but I still think they will

[Apogee]

When are brakes too big? That depends...if you're buying brakes for their aesthetic traits, then there is probably no such thing as too big, only to be limited by wheel size. Assuming that most of us want the performance enhancements that should go with the bigger rotor kits, the question of how much is enough versus too much is a valid one, but not particularly easy to answer due to all of the inherent variables involved. Without diving too deeply into those details, I think that pro-touring builds tend to favor slightly larger brakes than necessary such that they can be run on the street and track equally well, all with relatively street friendly pads. For all out track performance, race tires and race pads can do amazing things on remarkably small rotors with high pad/rotor temps, but they're typically no fun to drive at low temps, squeal like a gravel truck coming to a stop, and cut through rotors like my dog chews through rawhide bones.

Tobin
KORE3

[68camotion]

I can't understand the whole bigger is better thing with brakes either. I think with wheels over 15 inches 13 inch six pistons are perfect.

[Huzzah!]

Ended up going with Baer's T4. Got the last kit on the shelf in the country I think. Wish I could have gotten the black calipers but I don't want to wait two months. :(

[CreepinDeth]

When are brakes TOO Big ??

When the rotational mass of the larger and heavier rotors is counterproductive brakes stopping power.

They put 4th gen F-body brakes on a 5th gen Camaro with 17" rims.

The car stopped alot sooner. Weight of the rims obviously played a factor too.

[kawaden]

Can anyone suggest a reason that a lot of PT cars I see are running the same size brakes front and rear? when most all car manufacturers (even exotics like Lamborghini) run smaller on the rear.

[Roadbuster]

Can anyone suggest a reason that a lot of PT cars I see are running the same size brakes front and rear? when most all car manufacturers (even exotics like Lamborghini) run smaller on the rear.

I think it is for looks. They aftermarket systems usually have smaller pistons in the rear to hydraulically balance the system.

I personally have 13 x1.25 up front an looking at 12x1 or 12x1.25 for the rear.

[CreepinDeth]

Can anyone suggest a reason that a lot of PT cars I see are running the same size brakes front and rear?
when most all car manufacturers (even exotics like Lamborghini) run smaller on the rear.

For symmetrical looks has always been my guess when talking about street cars.
Plus they have alot of money to burn. :)

[kawaden]

Thanks for the replies. I ask as a Brake shop wants to sell me a Baer brake system with 6 piston 14 in fronts and the same on the rear for a 3200 pound car, which I think is over kill. I was thinking 6p 13in front and 4p 13in rear. Any opinions welcome.

[Bryce]

my 95 mustang is 3250 and has 11" brakes in the front and 10" in the back with single piston calipers and ceramic pads. It stops great and I can lock up the brakes then the ABS kicks in.

[Twentyover]

When are brakes TOO Big ??

When the rotational mass of the larger and heavier rotors is counterproductive brakes stopping power.

They put 4th gen F-body brakes on a 5th gen Camaro with 17" rims.

The car stopped alot sooner. Weight of the rims obviously played a factor too.

Who is "They"