Forged sl4s or Billet sl4s? On corvette engineerings website they are the talladegas and the daytonas. http://www.store.corvettengineering....ewCat&catId=14
Give me a hand in deciding!

 

I got the cheaper Daytonas as i want to be able to fit the stock wheels on the odd occasion. Real nice set up and easy to deal with people.

 

I think you mean the dynalites? The daytonas are the billet superlight 4s which are the step down from sl6.

 

I have Wilwood calipers (least expensive model) and they work great. My car has manual brakes and stops just fine. However, I mainly drive below 80 mph. I have not had to try to stop the car from excessive speeds.

 

Their "Laguna" front kit would be the Dyanlite and fit your smaller wheel. The BSL/FSL products are nearly identical in size and share the same pad. The DL is much smaller and of course uses much smaller pads as well. If you're serious about your track day use I'd personally suggest the larger offerings be used.

 

Which caliper offers more? The D8 or the superlight 4 series? Besides the d8 being an exact upgraded stock replacement is it a better caliper than the superlight 4?

 

With a stock master cylinder the Superlight 4 is the biggest you can use.

I also went with larger two piece 13 inch rotors.

The Daytona uses the Superlite 4 which has a larger, pad and bigger pistons in the exit side of the caliper to reduce pad taper. Differential pistons also give the caliper more clamping power.

 

Depends on your def of "more".

The D8 is actually the largest displacement at 4 x 1.875 so for a given line pressure it produces the most clamping force.

The BSL4 and FSL are both available in differential bore 1.75/1.875 to control pad taper. With less total area they will produce lower clamping for the same line pressure input.

I really would not get to worked up on the pressure deal and forces and master cylinders etc. All of them will produce near identical feel and necessary clamping of the stock iron caliper and work as stated with the stock mc. When fit with larger rotors it customary to reduce piston area and use more leverage in the brake formula over clamping which is why full BBKs have a "firmer pedal" than stock.

The biggest concerns you need to think about are wheel fit and pads. The D8 will clear any wheel that you currently run. The other two may require a wheel spacer either for total body size or the body shape. The pads on the D8 are quite thin for track day use if that's important to you. They oe stock size. The BSL/FSL offers a much thicker pad which will last much longer and keep more heat out of the caliper body.

Having had experience with all three I cannot say one is "better" than another simply by design or type. They are in essence the same product packaged in a slightly different manner.

 

I agree,
The difference between the calipers is pretty small. The brake torque values are all nearly identical as the 1/16" difference in 1 piston is pretty minor.

The D8 is probably a bit better than the Narrow dynalite used in the Laguna, but a lot more $$. The biggest difference would be pad area.

Pad area does not affect brake torque, only pad lifetime, and maybe brake fade under extreme conditions as there is more pad for cooling.

It suprises people that pad area doesn't affect brake torque but The formula for brake torque on a disk brake system is
Torque = (Brake Pressure) X (Piston Area) X (Effective Rotor Radius) X (Pad
Coefficient of friction) X 2
Notice there is no mention of pad area. And the coefficient of friction is the same for the pads for both calipers.

Wilwood does tell me that the Billet SL4 is the best caliper of the three ( D8 wasn't discussed at that time) then the Forged SL4, but the forged Sl4 is by far the best bang for the buck.

Keith

 

I have 17" centerline wheels so I should be ok. Im gonna take some measurements tonight and make sure. Im not one for bling factor but those billet sl4s look very nice. Im gonna go with stock diameter rotors all around. If I feel I need more, I will upgrade to a 13" rotor.

 

Keep in mind a couple of more things;

1. Depending upon your final choice you may find moving to 13" rotors more problem and cost than it's worth.
2. You can purchase complete Wilwood 13" kits in "final form" from the get go.
3. Using such larger rotors on the larger piston area calipers will (properly) require you make a similar change to the rear brakes as well to keep brake biasing issues in check.

You can always use the following tool for your quick calculations as well.
Brake Bias Calculator

 

Couldnt I make appropriate adjustments with a proportioning valve?

 

You mean if you were to install an overly front biased system and make no changes to the rear to counter this? No. Prop valves are rear application only and are intended to reduce line pressure. They have no place in the front brake system. In essence the harder you push on the pedal the less braking you have with such an item- not what one wants for a front brake system.

I'm willing to toss out whatever factual info I can on the topic but without understanding exactly what you want and expect from a purchase some of that info my be good, some not. First you have to define what your intent is. Stock wheels ever again or not. Track day use or not. Aftermarket wheels that are BBK friendly or not. etc.

 

I have 17inch wheels and plan on going larger. Occasional autox and maybe a track day or two with a few trips to the dragstrip thrown in. Mainly for street use. What would you recommend for the rear if I upgraded to 13" rotors up front?

 

I actually ran all last year with front 13 inch with aluminum hats. the rear I did not touch. So it still had stock rear calipers with carbon metalic pads. 600 degree fluid.

I never noticed a brake bias problem, so I did not install the rear bias valve.

i drive all over with my street tires and do the late braking and I have not noticed a problem other than cold performance is erratic with my choice of racing brake pad compounds.

 

The D8 would still be in the running if you were inclined. With proper pad the set up would be acceptable for the enthusiast level.

Your other options would be the Wilwood 13/14" front kit and the 13/14" rear kits. Clearly you can run the 13s now and with the proper mount spacers you could move to 14s if you wanted (with new rotors of course)

I would discourage doing only the front or mixing a 13" front with a D8 rear for a number of reasons however.

 

For front calipers, the D8-4 or one of the Superlites is the only caliper I would use on a track day or auto-cross car. The pad in the Dynalite is just too small and will not last very long. I'd only use a Dynalite kit on a drag car or for very mild street driving. Good pad compounds are available for the Superlites and the D8-4.
The Forged Superlite 4's s are a great bang-for-the-buck, but they are not a direct mount caliper. They will require the purchase or fabrication of an additional bracket, so money savings over the D8-4 may not actually be there.
The D8-4 does use the thinner stock pad, but using a race compound pad for track events will compensate with a lower wear rate and a better tempoerature range. If I were going to stay with the stock size rotors, I'd bolt on the D8-4's and use BP-10 pads for street/strip. For track days and autocross, stepping up to the PolyMatrix "E" pads will most likely be necessary. They may be a little noisy or dusty for the street, but they have better temperature range and a little more bite than the BP-10's. For all out road racing, the PolyMatrix A pad is superior to anything I have tested. But, I'd never drive A's on the street.
With 17" wheels, I'd use the 13" rotor kit on the front. The SL6 calipers in Wilwood's bolt-on Big Brake kits actually have a little less overall piston area than the big four piston calipers, so the static bias difference is not severely changed if the stock size rotors are maintained in the rear. The 13" rotors give more brake leverage, and far better cooling capacity than the OE size rotors, and will keep you on the track longer. If you run the big Brake kit with 6 piston calipers on a manual brake car, I'd highly recommend a 7/8" master cylinder. On a power brake car, the OE MC should work just fine.
As for a proportioning valve, any car that is being modified from stock with brakes, or tire size, gear ratio, engine compression and/or suspension mods, should convert to an adjustable proportioning for fine tuning. All of those factors affect the "dynamic" bias and what the rear tires feel when the car is in hard deceleration.
As for using the 13" front rotors with OE size rear rotors, I can't 100% agree with Todd's reluctance to mix front and rear brake sizes. I am not surprised that gkull didn't have any biasing issues. A different choice of pad compound though, to one with a a flatter friction curve, could get rid of some of the erratic cold stopping issues. The HD brake option that Chevy offered on the C4's, only consisted of a bigger 13" front rotor with a bracket that remounted the same caliper in the correct radial proportion. The rear brakes on the standard C4 and the HD brake option C4's are the same, with no biasing issues.
There is also something to be said for keeping the rotating inertia/weight on the rear axle as light as possible for a track-only car. Plus, a race car in hard deceleration will lose more rear weight percentage with dynamic weight transfer, so it is all kind of a wash anyway if the car has a little less rear static brake bias...
And one final note on master cylinder size, regardless of the brake combination, I can't foresee any situation where a larger than stock bore size master cylinder would be necessary uinless the pedal is also being modified to a longer ratio. There aren't many calipers with more piston area than the stock front calipers, so more MC volume should not ever really be a need.

 

WWEAST Have you ever tried the "H" wilwood compound?

 

Not sure who originally asked all this but you should consider yourself well rounded when we wrap up this discussion as we're covering about everything up one side and down the other for you. (!)

As for H pads, they are track only as are A pads. Both are high torque, high temp applications only. A pads will destroy a rotor in a week if run as a street pad. You've been warned! lol

My thoughts on the combining of 13 or 14" front kits with a D8 rear caliper only fall along this line:

First, the two calipers are visually quite different. So too will be the rotor finish. While not a functional thing this I've found can be a peeve to some folks so it should be clear up front if you intend to go this way.

The main reason is how it may effect the cars bias. The D8 remains as stock with whopping 5.5sq" of area. The BSL6 set ups will reduce this to about 4.1sq". Despite the added rotor diameter (using 13 for 17 wheels) the rotor diameter the fit of this alone to the front would add quite a bit of rear brake bias. When paired with the Wilwood rear kit this should not pose much of an issue because of the small pistons in the BSL4 rear caliper.

Where my warning light comes on is that the D8 retains stock 3.0sq" of area which when combined with the rearward shift with the front kit may prove a bit too much. For me the kicker is less about static bias on this one than dynamic. The front kit will require additional leg input to achieve the same rotor torque value (what we love about the 'feel' of a bbk) but this means more pressure is directed to the rear brakes as well given a single mc system. Without knowing how the older cars control proportioning issues this added pressure combined with greater piston area and a rear shift in the combining of kits....seems all a bit iffy to me.

You could tune around all this somewhat with pad Cf variables (if you can handle the noise, dust or wear) or maybe fit an adjustable valve to the rear...or maybe something more but in the end it all seems much easier (and cleaner appearing) to use a combo that is much closer in matching the needs.

 

You can get a bracket pretty cheap for the superlites according to the link at the top of the page

As someone who has spent way too much time trying to get the SL6 to work, the SL6 is a horrible choice for the C3. the piston area is tiny and will make the car unstable ( massive rear bias ) and just plain not stop. everyone wants 6 piston, cause they sound cool.

It's way more complicated than that, believe me. But then I'm pretty picky. The SL4 with manula brakes is awesome, the SL6 with power sucks even with a manual MC and changing pedal ratios


The C3 is actually to rearward biased, the front should lock up just before the rear and in stock form it doesn't. Putting 13" rotors on a otherwise stock c3 with superlites is probably benificial to the brake bias.

I run billet Superlight 4 in front and 1.75" dynalites in back with a prop valve turned way down so the front's lock up just before the rear