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Presume you are taking about the D8-6 versus the D-8-4 direct replacement calipers.
No, I have the D8-6 calipers on front. They actually have 5.51 sq in of piston area compared to 5.56 for the 4 piston version. So 0.9% less piston area (not really noticeable). The biggest difference is the fact that the D8-6 uses 3 different piston sizes to help with pad wear.
Even the Dynapro 6 position caliper only has 5.06 sq in of piston area so it is 10% less than stock.
I’ve also read in a couple places that the brake lines that come with the rear D8-4s are too short. This is not a deal breaker for me because I know a pretty good shop around here that builds custom lines. I was just wondering if they ever corrected this problem.
This topic of the Wilwood 4 piston versus 6 piston caliper has come up before and makes no sense to me why Wilwood would offer a 6 piston caliper with Less area than the 4 piston caliper. I looked at the diagrams provided by SteveG75 and cannot believe that the 6 pot Caliper has 3 different size pistons. Why would Wilwood design the caliper that way? I would assume that since the caliper needed to be the same size dimensions as the OEM GM 4 piston caliper AND was going to use the same OEM brake pad size, wilwood had design constraints that limited the size of the 6 pistons fitted into the space. From a brake performance point, the reduced piston area of the 6 piston versus the 4 piston caliper makes little sense.
I have 2 cars that have a 6 piston front calipers and the calipers in both cars have 6 pistons all the SAME size. These cars also have VERY big brake pads to take advantage of the enormous brake force exerted on the rotor by the 6 piston caliper. Wilwood offering a 6 piston caliper with reduced piston area, with the same size brake pad as the OEM brake pad size, and using the same 11.75 inch rotor will show no brake performance improvement using the 6 piston versus the 4 piston Wilwood caliper AND will not show any brake performance advantage versus the OEM C3 corvette brake performance using the stock 4 piston fixed cast iron caliper. The only heat advantage to the wilwood aluminum calipers is better heat rejection under hard racing use. A forum member years back published brake results using the wilwood 4 and 6 piston calipers versus the OEM system and the brake performance was the same, no difference. I would image the 6 piston wilwood caliper might have better brake pedal feel and better modulation than the 4 piston caliper, maybe.
The only way to improve the C3 terrific stock 4 piston fixed/racing style caliper brake system, Front and Rear, 12 inch vented rotors, front AND rear, is to use a better brake pad material, braided stainless steel brake hoses, sticker softer ultra high performance 17/18 tires or a larger brake rotor with the stock system (more brake torque). I am not aware of anyone who offers a kit to use the stock calipers with larger brake rotors (13/14 inch).
Using the Wilwood brake caliper system with their 13/14 inch rotors will improve brake performance but I certainly would only use the 4 piston caliper since the 6 piston one does not seem to offer any advantage. Has anyone spoken to wilwood about the supposed performance advantage of using their 6 piston caliper versus the wilwood 4 piston caliper?
Some of this information comes from my brake upgrades on a few cars over the years. Just changing the 11 inch front caliper to the impala 12 inch caliper on my 01 Grand Prix with the same caliper/brake pad (no other changes), noticeably increased the brake force and brake performance of the car on the street. I also installed Cobra front brakes on my 94 mustang GT, 13 inch dual piston rotor versus the 11 inch single piston rotor, which completely upgraded the car's brake performance. Same result going 12 inch front vented rotor, single piston caliper to a MUCH bigger dual piston caliper, bigger brake pad, 14 inch rotor on my Chrysler 300. Holy smokes, the big 300 stops NOW!
Last edited by jb78L-82; May 16, 2020 at 07:53 AM.
This topic of the Wilwood 4 piston versus 6 piston caliper has come up before and makes no sense to me why Wilwood would offer a 6 piston caliper with Less area than the 4 piston caliper. I looked at the diagrams provided by SteveG75 and cannot believe that the 6 pot Caliper has 3 different size pistons. Why would Wilwood design the caliper that way? I would assume that since the caliper needed to be the same size dimensions as the OEM GM 4 piston caliper AND was going to use the same OEM brake pad size, wilwood had design constraints that limited the size of the 6 pistons fitted into the space. From a brake performance point, the reduced piston area of the 6 piston versus the 4 piston caliper makes little sense.
.....
While I agree that the smaller piston area on the 6 pistons is a poor design by Wilwood, the 3 different piston sizes is commonplace with performance calipers. If you notice, the pistons are arranged big to small, this helps with leading(maybe trailing? I forget) edge pad taper. Even some 4 piston calipers have multiple piston sizes.
They actually have 5.51 sq in of piston area compared to 5.56 for the 4 piston version. So 0.9% less piston area (not really noticeable).
Originally Posted by jb78L-82
This topic of the Wilwood 4 piston versus 6 piston caliper has come up before ..... From a brake performance point, the reduced piston area of the 6 piston versus the 4 piston caliper makes little sense.
As SteveG says, there ain't no perceptible difference.
What I found in experimenting with my 6 piston conversion was that the stock Corvette piston areas made it impossible to lock up the rears (manual brakes). Just not enough braking authority in my 3000# car. Yes, one does not want the rears to lock up first but no matter how hard I stomped I couldn't make it happen. What I ended up doing was adapting a set of 4 piston fronts to the rear and installing a proportioning valve to ensure I didn't overwhelm the fronts. Works great and I can now dial in all four wheels..
I had intended to measure my 70 MPH distance to get some quantitative measure, but couldn't figure out an accurate means to make that measurement so I lost interest. Had an Arduino setup with accelerometers in mind.
Had a problem with a stuck piston which Wilwood fixed gratis, hence this picture. You can just see the different piston areas here. As I remember the bigger guy goes to the trailing edge which makes sense. There is an orientation notation on the flip side of the caliper in any event.
You want the bigger pistons to the trailing edge.
Another way to accomplish the same thing with equal sized pistons is to offset the pistons to the trailing side of the caliper.
If this is not done, the pads tend to wear in a taper.
While I agree that the smaller piston area on the 6 pistons is a poor design by Wilwood, the 3 different piston sizes is commonplace with performance calipers. If you notice, the pistons are arranged big to small, this helps with leading(maybe trailing? I forget) edge pad taper. Even some 4 piston calipers have multiple piston sizes.
Not on my 2 cars, both with 6 piston front calipers:
C6Z06-All 6 pistons are the same size
MB AMG - All 6 pistons in the Brembo Caliper are the same size.
Just a couple thoughts as I understand it- piston area is not the end all be all-
I'm guessing Wilwood had the 6 piston design CLOSE to the 4 piston design as far as piston area- so you can use the same master cylinder whether manual or power. So bigger would not be better if you wanted the brakes to work with the original master cylinder and feel the same.
Match the percentage increase/decrease in caliper piston area to the master cylinder piston area increase/decrease to achieve a similar pedal response to the original calipers.
Theoretically more pistons- the brakes will be easier to modulate.
Clamping force at the rotor will not change at lockup -more piston area greater clamping force- number of pistons doesn't matter-
It's like tightening a bolt with a short ratchet or a long ratchet. You can break the bolt with either tool but you'll have better feel for the torque with the long ratchet.
I went with bigger rotors- yet smaller piston area w/ 6 pistons ( & smaller master cylinder), Larger diameter rotors allow easier pedal modulation and have better control over the brakes.
This is a test by forum member Jim-AKA "427Hotrod"
Wilwood vs Originals
Here's the article- http://www.carsandparts.com/Articles...e-braking-test
************Link is no good any more***************
It's a very good read.....here's the numbers- not perfectly scientific
STOCK Calipers-
•151 ft., 2 in. - Nice quick stop to get an idea of how hard I could push it on that surface.
•123 ft., 7 in. - Worked it much harder. No brake lockup or drama.
•118 ft., 3 in. - Back to back. Now I knew I could work it harder.
•109 ft., 5 in. - Hit it hard and kept it right on the edge of lockup. Never could repeat it.
•135 ft., 1 in. - Real hard and locked up front wheels early and rears near the end.
•111 ft., 4 in. - Very similar to test four.
•113 ft., 2 in. - Another good one!
Wilwood-D8-6 and D8-4 calipers
•130 ft., 9 in. - Good feel but sliding at the end.
•129 ft., 6 in. - Nearly identical.
•115 ft., 5 in. - Finding the “sweet spot”.
•109 ft., 4 in. - Maybe the pads are getting “bedded”?
•107 ft., 8 in. - Bang! Best ever!
•109 ft., 11 in. - Still working great!
•109 ft., 3 in. - Did it again!
I went with w/ the D8-4 on the rears and the Big Brake 14" 6 piston on the front-
AND I stayed with MANUAL brakes but went DOWN in Master Cylinder size 1/8" to 7/8" bore-
I would bet that you could easily beat the numbers for the wilwood and stock system above ^^^^ with your setup with the 6 piston caliper and importantly, those 14 inch rotors...hands down. The difference will be the rate of deceleration will be faster/quicker, SHORT OF LOCKUP and the ability to avoid locking the brakes/tires with more brake torque and much better modulation, everything else being equal.
I experienced this exact phenomenon going to 14 inch rotors, dual piston calpers and using the OEM Chrysler 300 MC for the single piston caliper with 12 inch rotors...same exact tires. What folks do not understand is that Yes, I could slam my foot to the floor with the OEM single caliper and 12 inch rotors and could engage the ABS in a near panic mode stopping procedure (along with heart in the mouth and a feeling of no control) BUT with the bigger brakes the car decelerates faster short of lockup, with much less pedal effort, with perfect control. It is what is happening from initial pedal application to SHORT of lockup that matters most.....and how best to AVOID locking the brakes or engaging ABS
Last edited by jb78L-82; May 16, 2020 at 10:35 PM.
Is there any advantage to using Wilwood 6 piston calipers over their 4 piston design For stock diameter rotors?
As is often the case here, and I am somewhat guilty as well, this post has veered off into exotic territory. The short answer is there is no braking advantage. The pads will wear more evenly with the six piston setup. If there is no cost delta, six is a better choice.
As is often the case here, and I am somewhat guilty as well, this post has veered off into exotic territory. The short answer is there is no braking advantage. The pads will wear more evenly with the six piston setup. If there is no cost delta, six is a better choice.
Ignatz is keeping us on task.
I agree that the short answer is there should be no real braking advantage using the wilwood 6 piston fixed racing style caliper versus their wilwood 4 piston caliper since the piston volume is slightly less for the 6 piston wilwood caliper BUT brake pedal feel and accompanying braking modulation may be enhanced using Wilwood's 6 piston caliper over the 4 piston caliper.
Generally speaking, almost always, a multi-piston caliper, a fixed caliper much preferred over a floating caliper, using a bigger area brake pad with a bigger rotor will provide the best braking performance with the same size/compound tires along with faster deceleration from intitial brake pedal application all the way through threshold lockup/ABS application with better brake pedal feel/modulation, in a more repeatedable brake performance manner......Whew!
As is often the case here, and I am somewhat guilty as well, this post has veered off into exotic territory. The short answer is there is no braking advantage. The pads will wear more evenly with the six piston setup. If there is no cost delta, six is a better choice.
Not always.
To prevent uneven pad wear (taper) requires that the caliper vary the force it applies across the pad.
The leading edge of the pad tends to dig into the rotor (similar to the leading shoe in a drum brake) and wear faster.
The caliper designer has to change piston diameters or locations to address that issue.
A longer six piston caliper can have more flex and less feel than a shorter rigid 4 piston caliper.
This can be cured by bridging the caliper, but that too has trade offs.
