LocostUSA.com

Is their a rule of thumb about sizing brakes ?
How big? Weight?

The car is 1000 lbs.
130 Hp.+-

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American 7 5.0 T5
Lotus 15 ish?
914/H6

I'm new to the se7en world, but years ago I had a 1979 VW Rabbit, weighed more than twice your target weight and 60% the HP, it used solid rotors, probably ~8", plenty of stopping power.

I think it depends on your goals and your wheel size... I've seen a lot of comments praising 13" wheels and tires, so tiny brakes would be a plus... If you're aiming larger wheels you've for a lot more options... My Rotus came with Wilwood Dynalite calipers, one caliper weighs about the same as the box of new brake pads. I don't know that a vented rotor is even necessary on a car this light, unless you're planning on track duty.

2¢

Since the energy of a moving object is equal to mass*speed^2, any modern car's brakes capable of stopping from 80 MPH safely will be capable of a stopping a 1000# Locost moving at 115MPH safely. Racing has its own set of demands not addressed by this formula. There are a lot of UK clubmans running 13 inch brakes though.

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

As big as will allow the caliper to clear the inside of the wheel plus 1/4 inch no matter what condition the pads are in.
As much swept area as possible.
As much thermal mass as needed for the type of racing. A road racer needs more than a drag car.

One way to compare is swept area in square inches/ton.

Basically a typical 3000+lb performance car rotor and caliper that will fit your rim, drilled to reduce weight and thermal mass that you will never need to prevent rotor warpage. Will probably aide cooling and pad cleaning too. Besides curb weight, the faster it is, the more thermal mass you will likely need.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

At 1000 pounds and 140 bhp. If you donor vehicle has disk brakes your good. I have Miata uprights and upgraded Wilwood calipers and rotors. More than overkill, plenty of brakes for 130mph max braking events. Pads last for years:)

Graham

Once you have some chassis and brake configurations in mind you can plug them into the Brake Components Calculator and run different combinations. Even plugging in some approximate numbers can provide some useful info. You can find the calculator here:

viewtopic.php?f=5&t=14424&p=262842&hilit=brake+calculator#p262842

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Cheers, Tom

My Car9 build: viewtopic.php?f=35&t=14613
"It's the construction of the car-the sheer lunacy and joy of making diverse parts come together and work as one-that counts."
Ultima Spyder, Northstar 4.0, Porsche G50/52

Thanks, everyone ! Big help.

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American 7 5.0 T5
Lotus 15 ish?
914/H6