Why bigger brakes?

[Lambo Nut Junior Member Find all posts View Profile Close Lambo Nut]

Hoping I can be enlightened. ???
Why do some people think you need bigger brake systems on a Fiero, when you put in 350, or 3800, or whatever? I hear higher "horse power, need bigger brakes". Why? The first thing I do before applying the brakes, is let off the gas pedal. So why would the brakes care, if the engine is 100, or 1000 hp? I'm thinking, as long as the weight of the car stays near the same, what difference would it make? The fiero being all wheel disc brakes, seems like a good system. Also, how big of brake system, could there be on a factory Countach, that only had 15 inch wheels to start with? I plan on completely redoing the brakes on my Lambo build, with new, replacement parts, nothing bigger. I don't see the point.
So any good reasons for the bigger brakes, other then "I want bigger brakes"?
I'm not trying to stir up anything, just looking for an honest, real reason/answer.

Kevin

[Corson008 Junior Member Find all posts View Profile Close Corson008]

Re: Why bigger brakes?

if you're asking a question like this, you SHOULD NOT be building a car .....

[murcie-me Senior Member Find all posts View Profile Close murcie-me]

Re: Why bigger brakes?

Lambo nut,
You are 100% correct in your assesment of needing bigger brakes. As long as the vehicle is not much heavier than it was to begin with, the brakes that came with your car (stock) should be just fine.
Ther is one thing to consider though, and plays a major role in how well those stock brakes will work on your new re-bodied car. Although the body weight may be close to the same, most people usually change thier wheel/tire combination, which has a dramatic effect on braking effiecency. The disk/rotor size that came stock on your car was engineered to stop the size wheel/tire combo that also came on your car. Changing up to an 18" rim from a 15" rim could double the amount of stress the disc has to endure to stop the car, depending on the size of the tire mounted to that wheel. Another problem that most people dont consider is the hub/spindle that the rotor is mounted on. Simply increasing the rotor size doesn't give you more braking power. The hub and spindle must also be rated to handle the additional torque applied to them during braking. If you were to take a stock Fiero brake system, and simply replace the stock rotors with 12" rotors, upgrade the wheel/tire combo to something that would be used on that specific kit car ( lets say the Murcielago, for example), and not make any change to the spindles or hubs of the vehicle, the result under heavy braking could/would be catastrophic.

[LarryG Junior Member Find all posts View Profile Close LarryG]

Re: Why bigger brakes?

Lambo Nut, I totally agree with you.

If a car has an excellent braking system, I don't see why you would upgrade it.
Braking has to do with stopping a mass going at a given speed.
Wether the mass is propelled by a 100 or 500 hp engine doesn't matter. 3000 pounds going 80 MPH is 3000 pounds going 80 MPH no matter
how many hp proppeled it there.

Maybe it could be considered if you intend to change your driving habits and always drive hard and at the edge rather than driving normally!

Just my .02 c.

LarryG

[LarryG Junior Member Find all posts View Profile Close LarryG]

Re: Why bigger brakes?

WOOPPPSSS..... MURCIE_ME, That's an intelligent answer! ;D

LarryG

[cyanides Junior Member Find all posts View Profile Close cyanides]

Re: Why bigger brakes?

They are prettier than stock. Also, I believe that for the Beretta and the LeBaron upgrade, the parts are actually cheaper than the stock fiero. Brackets for the LeBaron upgrade ran $130 for the whole set. A pair of LeBaron rotors off ebay ran $30 a pair if I remember right. If you have an automatic and don't need your hand brake you can use 4 front 85 seville calipers. They run $25 from autozone. (part #C134 and C135)

Fiero front rotor $44 each, rear rotor $30 each, front calipers $58 each, rear calipers $102 each.

Not sure what all you want to replace.

The 12" and 13" Corvette conversion will run way over what fiero stock will run.

Quick note. Beretta rotors are the same diameter as Fiero except they are vented. LeBaron rotors are 11.25" in diameter.

[Mr Ferrari Senior Member Find all posts View Profile Close Mr Ferrari]

Re: Why bigger brakes?


Durring normal driving the stock brakes work okay.. But if you are going 150mph and lay on the stock brakes your asking for trouble.. Vented rotors displace heat better and will not "fade' as quickly as solid rotors.. In racing conditions the stock brakes on the Fiero would be so hot after a few times of hard braking that you would lose almost all braking power.. Vented rotors would help and be good enough for the street, but if you want or need reliable and consistant high speed braking for a track capable car then you would definatley want to upgrade..

[rockcrawl Junior Member Find all posts View Profile Close rockcrawl]

Re: Why bigger brakes?

Simply increasing the rotor size doesn't give you more braking power.

A larger diameter rotor will generate more torque given the same amount of pressure on the pads.

If you were to take a stock Fiero brake system, and simply replace the stock rotors with 12" rotors, upgrade the wheel/tire combo to something that would be used on that specific kit car ( lets say the Murcielago, for example), and not make any change to the spindles or hubs of the vehicle, the result under heavy braking could/would be catastrophic.

There is surely a point where the front spindles will twist in half and the rear struts will bend over, but I don't think there is a brake/wheel/tire combo on the planet that will make it happen. OK, at least not for a Fiero.

LarryG hit the nail on the head when he mentioned driving habits. The type of person who generally does an engine swap for more power is also going to drive the car harder. The faster it accelerates, the more braking needed to slow it down. Here in PA where it is very hilly, I can run a Fiero with stock brakes for 15 minutes and have the brakes so hot that they barely stop the car, it's not much fun when you're approching a T intersection at the bottom of a steep hill. The stock Fiero rotors (pre-88) are non-vented. Rotor diameter aside, there are still gains to be had from switching to a vented rotor. A vented rotor has more mass to absorb heat that is generated during braking, and more surface area to dissipate the heat as well as the vanes that act as an air pump to move air over the surface of the rotor. A larger diameter rotor adds more torque and more mass. The added mass does have a negative affect on braking (and acceleration) because it is rotating mass that also needs to be stopped, but this negative is outwheighed by the extra torque it provides, and that's why big rotors work. The only disadvantage to a larger rotor is weight, thats why you now see rotors made of other materials like composites and the Murcielago 15" ceramic rotors.

I've noticed great improvements on the stock brakes by just replacing the hoses and fluid. I personally don't want to look behind my Murcie wheels and see stock 9" Fiero brakes. I'm spending all this time and money to replicate a supercar, I want it to look like it has supercar brakes. And no, those fake stainless steel discs without calipers won't do. I have 13" rotors and four-piston calipers on my car. I also upgraded the front spindles, rear knuckles, and hubs, though I don't really feel it was necessary for strength.

[FerrariXXXman Senior Member Find all posts View Profile Close FerrariXXXman]

Re: Why bigger brakes?

I was thinking the same thing too long ago, before I put all the turbo goodies for the quad in my TR. Whilst I don't drive my car hard all the time, it is nice to open it up once in while and you need good brakes to slow all that down. Larger diameter brakes will allow more leverage as the gripping point on the rotor is farther from the center of rotation. I own an 85 and an DD 88 GT stock fiero. Ever try to lock up the wheels in a stock fiero on dry pavement? Can't happen. The front suspension/brakes of our beloved donor car comes from a 'vette..... not corvette, but chevette. The rear spindles/brakes are from an 80's chev citation. GM used these stampings to keep costs of the fiero down, and are more than adequate if you have a 2.5L 4, or even the 135HP 6. Driving my TR on some back country roads, the brakes were nearly worthless, especially after they suffered from the heat issue others have commented about and this is darn right scary. So, you gonna stick with that good 'ol iron duke then it's ok. You want a car that will perform and going to install a high HP engine, be safe and do it right, it's not for appearances at all. Eric

[drew355 Junior Member Find all posts View Profile Close drew355]

Re: Why bigger brakes?

I know what you are getting at, but if you increase the engine size can you honestly say you wont drive the car any different? If you dont drive it any different why would you bother putting the larger engine in? I dont mean driving like an idiot, but bigger engine = better acceleration therefore when you reach your favourite corner the extra acceleration is much more likely to result in a higher speed approaching the corner, hence the preference for larger OR more efficient brakes.

[Lambo Nut Junior Member Find all posts View Profile Close Lambo Nut]

Re: Why bigger brakes?

Thanks for all the answers guys, (well, all but one anyway) :P

I do under stand, if you are going road racing, you need something better, but I was just figuring, if the stock V6 could get the car to 120 mph, (which I doubt I would exceed too many times, as I don't want the ticket, or lose the car, wife and three kids yada, yada, yada), and stop it, it would do the same with any motor. I plan on driving it normally, with the occasion romp on the highway, heading to shows and such, but it will not be my "daily driver" by no means. Speed limit is only 70 in the highways here, I just want to get to that speed, a little quicker then with a four cylinder. I turn 42 next week, so I no longer have anything to prove to the "I think I got more horsepower" crowd on the streets.

I guess, I was thinking, people were saying bigger brakes, based solely on the motor hp, but it seems to be linked more to driving a little too hard. Maybe I'll still be all right, as I'm not so much a cornering kind of guy, more a straight line acceleration kind of guy. My first car was a 70 Charger with a 383 magnum, and four-wheel DRUM brakes. Now if you want to talk about a brake system that was not adequate for the car!

Thanks,
Kevin

[Brastic Junior Member Find all posts View Profile Close Brastic]

Re: Why bigger brakes?

On a Fiero, I care more about the brakes being vented than bigger. Talking to the guys who autocross, they like the 88s for the suspension upgrade and mainly the vented brakes. The 84-87 Fieros are known to get brake fade. One aspect of bigger brakes is less fade.

[rockcrawl Junior Member Find all posts View Profile Close rockcrawl]

Re: Why bigger brakes?

I was just figuring, if the stock V6 could get the car to 120 mph, and stop it, it would do the same with any motor.

Kevin, it's not so much a matter of how fast the car goes, it's more of a duty cycle issue. Take for example a stock Fiero going from 0-60-0. Lets say it takes 1 mile of road to do it. A modified car with a more powerful engine might be able to do 0-60-0 twice in one mile because it can accelerate faster. Both cars did the same top speed and traveled the same distance, but the second car did twice as much braking. Not because it had to, but becauase it could and the driver wanted to. You don't need to break the speed limit to overheat the brakes. The stock brakes will stop the car from 120, but how much distance will it take, and how many times can you do it before they get so hot that they just don't work anymore? I can tell you that if you take a Fiero to 120 and stop it in the shortest distance possible, you'd better give yourself some extra room for the next stop!

If your stock brakes don't fade and you don't change your driving habits, then there is no need to upgrade unless you add a lot of weight to the car.

Jon

[Lambo Nut Junior Member Find all posts View Profile Close Lambo Nut]

Re: Why bigger brakes?

I was just figuring, if the stock V6 could get the car to 120 mph, and stop it, it would do the same with any motor.

Kevin, it's not so much a matter of how fast the car goes, it's more of a duty cycle issue. Take for example a stock Fiero going from 0-60-0. Lets say it takes 1 mile of road to do it. A modified car with a more powerful engine might be able to do 0-60-0 twice in one mile because it can accelerate faster. Both cars did the same top speed and traveled the same distance, but the second car did twice as much braking. Not because it had to, but becauase it could and the driver wanted to. You don't need to break the speed limit to overheat the brakes. The stock brakes will stop the car from 120, but how much distance will it take, and how many times can you do it before they get so hot that they just don't work anymore? I can tell you that if you take a Fiero to 120 and stop it in the shortest distance possible, you'd better give yourself some extra room for the next stop!

If your stock brakes don't fade and you don't change your driving habits, then there is no need to upgrade unless you add a lot of weight to the car.

Jon

Thanks for this answer, Jon, as this is pretty much the logic I was thinking. I admit, I did laugh at first, thinking it's going to take a while getting where you want to go, stopping evey mile or so! ;D Also, If I did get the car up to 120 mph, and have to stop in the shortest distance possible, I probably won't be in any hurry, to get it back up to 120.

But seriously, am I correct in still thinking, if I'm going down the road, that the car is going to be just as safe to stop from 70 mph, with a SBC, as it would before?

Another thing that comes to mind, is the talk of the legality of modifying the stock brakes to begin with. I do not know for sure, but have read, if you are in an accident, and the insurance company can prove you modified/altered your brakes, good luck to you. Any truth to that? Then again, if it has to be inspected before getting titled, (as I do with mine) would you be covered, being a specially constructed vehicle, and passing the DMV/ Highway patrol inspection? Many things to check into.

Kevin

[psn497 Junior Member Find all posts View Profile Close psn497]

Re: Why bigger brakes?

OK, I've watched this thread long enough and have to add my 2cents from a former grand prix motorcycle racer. Same principle applies to cars. First, when upgrading your break system it's all about stopping ratio's vs exerted force. The larger the diameter of the rotor the less force needed to be exerted by the caliper onto the pads. Therefore less friction and heat generated to aquire the same or greater stopping power. Originally created for this reason: if you can break later into a corner or turn and still create greater stopping power you can now accelurate out of the turn faster, therefore having greater control and constant relative speed thru the turn or corner with out wasted time on the breaks and with out over heating components. When the same is applied to straight line stopping it's all about getting the vehicle to a complete controlled stop in the shortest distance.

So why do it on a kit car? Because it makes it look more like the original which was produced for performance and even though it's a replica we still want to get some sence of performance. And hell it just looks so much better to have big break rotors filling all the space behind those pretty rims instead of dead air. ;D