Steve91Z28 L98

I was looking through Steve Spohn's site and came across Wilwood's front brake kit for 4th gen F-Bodies. The kit has 6 piston billet calipers and 12.90" diameter rotors. The rotors are cross drilled and slotted and have the curved cooling vanes like LS1 rotors. The rotors are 2 piece with a black anodized hat. The kit also says it comes with new hubs and bearings and all the mounting brackets and hardware (probably of no use to us). Here is the link for them: http://www.spohn.net/product.cfm?productid=1413

My question is this: Since many people are already putting 4th gen brakes on our cars with only modified spindles, custom caliper bracket, and hub (turned 1LE rotor), couldn't this Wilwood setup be installed just as easily?? The only difference I can see between installing this and the LS1 brakes would be a different caliper bracket. The best part of this is that it only costs $1310. When you compare this to the price of the 4-piston Wilwood kit for our cars ($1595 - $1695), it seems like a steal. It seems odd that a kit with 6-piston calipers and 2-piece curved vane rotors costs less than a 4-piston/standard rotor kit. Does anyone have anymore info on this kit? I think there was a guy on this board that was involved in designing the 4-piston Wilwood kit for our cars. alloy is his name I believe. Maybe he can shed some more light on this subject.

Dewey316

i'm not alloy, but hopefully i can shed some light.

1) Alloy (Dan) looking into both the 4 and 6 piston wilwood calipers, the 4 piston caliper actualy has a larger piston area, he also made many many calls to wilwood, for help choosing the correct caliper. now if you are REALLY stuck on have the 6 pistons, wilwood makes a 6 piston caliper that has the same mounting points, and deminsions as the ones in that kit, you could buy the calipers on you own, and sell the calipers in steve's kit. (or try to work something with steve, i guess)

2) i beleive part of the cost diffrence, is in the need for some specialty parts to pull this off. the thirdgen brakes had a combo hub/rotor, it was all one peice, part of the kit you are getitng is a machined down rotor, to work as a hub, along with bearings for it, and wheel studs. basicly for the 4thgens, it is a much easier upgrade, you toss larger rotors on, make a mounting bracket for the caliper, and you are golden, this is not the case on our cars, there is more work inlvoved.

i hope that helps shed some light, i am sure when Dan see's this, he will respond, probably correct me a little, and answer your question better than i can.

Steve91Z28 L98

If what you say about the piston area being larger with the 4-piston caliper is true, I guess that could justify his choice. It does seem to me though, that the 6-piston caliper would provide more evenly distributed clamping of the pads which seems like a good thing to me. DO you know if the same pads are used for the different calipers? If both calipers have the same mounting bolt pattern like you say, I think it would be a great option for the kit that Steve offers. I wonder what the price difference is.

As for the price difference in the kits, it seems like the 2-piece curved vane rotors would be much more expensive than the standard rotors in the other kit. By the way, does anyone know if the rotors in the 4 piston kit are just C4 Vette HD rotors? They sure look like they are. I'm sure alloy will be able to tell me. Back to the price....the 4th gen kit says it comes with new hubs and bearings so that should offset the cost of the hubs and bearings for our cars (I know they are different but I can't see how one is more expensive than the other....maybe the 3rd gen ones are such low volume that they cost more).

My final question is if the 4-piston calipers are better, can they be used with the 2-piece curved vane rotor? These rotors would offer much better heat dissipation than the standard rotors (they seem a good bit wider....is this true?).

So I guess the main points I'm trying to find out are:

1) which caliper is better (4 or 6-piston)
and
2) can we use the 2-piece curved vane rotors instead of the standard ones.

Dewey316

4 Piston Caliper --
http://www.wilwood.com/products/calipers/fsl/index.asp


with the 1.75" piston option, that gives you about 4.8"^2 of piston area

6 Piston Caliper --
http://www.wilwood.com/products/calipers/bsc6/index.asp

uses 1 1.62" piston and 2 1.12" pistons, which gives you about 3.87"^2 of piston area.

but do note that they use the same pads, and are both on the sam 3.5" mounting pattern.


also, the rotors are not C4 HD rotors, i beleive the offset of them is incorrect.

Steve91Z28 L98

The 6-piston would give 4.03"^2 of piston area just to correct your math. Still a good bit behind the 1.75" 4-piston though. The option of two different diameters for the pistons brings up this point: Which ones come with the kit from Spohn? I also noticed that there are options depending on the rotor thickness you are using. I'm guessing the ones in the kit are 1.10" thick. That would make the curved vane rotors in the 4th gen kit be 1.25" thick. I still say using these rotors would be the way to go. Is there any reason they wouldn't work as long as you got the matching calipers? Maybe this has already been explored and determined not to work because of the wrong offset. It seems like the offset could be compensated for by changing the thickness of the caliper bracket or putting a spacer between the rotor and hub. There may also be different offset hats that are available for the two piece rotors. Thanks alot Dewey for your help.

Dewey316

to tell you the truth, i can't remeber if the kit uses 1.10" or 1.25"

hopefully alloy will pop in here soon.

either way, if you determined the proper offset, you could get rotors from wilwood directly, or other custom 2 peice rotors from someone like coleman racing.

Matt87GTA

Well of course this kit looks like a steal.... Until you build your own caliper brackets, hats, and hubs that make it fit your application, pay for the raw materials, and bill yourself for the time you spend on it! That is assuming you have access to the machinery to do it properly.

The bottom line is, assuming no clearance issues, any rotor and any caliper can be made to work if you build your own hats and caliper brackets and are running a stand alone hub or a turned down stock rotor...

alloy

iTrader: (16)

Thanks Matt87GTA for putting it into perspective. I couldn't have said it better. You hit the nail right on the head. But for the sake of argument I'll expand on what you said and to go into detail.

There are several misconceptions here I can see here that need to be cleared up. And, they are all covered in the original Pro series 13" brake post that Steve put up. It's a long read, but go back and read it carefully and then ask questions. You will be much better informed after reading through it.

https://www.thirdgen.org/techbb2/sho...5&pagenumber=1


First of all, the 4th gen kit does apparently come with hubs and bearings, but they are not for a 3rd gen. 4th gen hubs will not fit a 3rd gen. Second the rotors are not the proper offset to fit the Wilwood caliper under a stock 16" IROC wheel. 4th gen wheels have different offsets than a 3rd gen wheel does, and the calipers won't clear our wheels with these rotors and hats. Also, the 4th gen kit doesn't have the special brake hoses I have made up to fit a 3rd gen. Not to mention the caliper mounting hardware from the 4th gen kit will not work on a 3rd gen. You will have to design and make your own brackets. And, my kit from Spohn also includes andyz28's 1LE Cd. Other than the standard spindle mods, this is a bolt on kit. No fabrication necessary. All the leg work has been done for you. And believe me, there is a lot of leg work involved in sourcing out all the correct parts for this kit.

And, concerning the difference in 4 verses 6 piston calipers, yes they do use the same pads, and yes the 6 piston has less piston area which results in more pedal force needed over the 4 piston calipers. And, consider this, you have a brake pad that is a certain size. Take the 2 largest circles and fit them into a rectangle (the brake pad shape). You can fit 2 fairly large circles in the rectangle. Now take the same size rectangle and fit 3 circles in it in an almost straight line. To do this you have much smaller pistons, and they are all in one slightly curved line. So you have the 3 smaller pistons pressing on the center of the pad and not the edges. With a 4 piston caliper the circles (pistons) are larger and cover more pad backing plate area, and therefore have more surface area and spread this pressure out more evenly on the back of the pad resulting in better braking, easier braking control, and more even pad pressure and wear.

And in all my many conversations with wilwood, they tell me the 6 piston would do no more (actually less performance) in this application that a 4 piston would due to the limitations on piston size. They would just cost more and say 6 piston.

Steve91Z28 L98

Ok after reading the other post, I can see how the 4-piston calipers would perform just as well, if not better, than the 6-piston calipers. Am I wrong though in assuming that the 6-piston caliper would work with the same bracket the 4-piston uses? Both calipers have the same mounting bolt pattern. It seems that the two different calipers should have the same offset as well (assuming they are both for the same rotor thickness).

As for the rotors, I would still like to see a 1.25" thick rotor option for the kit. It may require a spacer to get the rotors in the correct position or a thicker caliper bracket to get the caliper centered over the rotor but those are minor details. Matt87GTA...what makes you think that you can't use the same hubs from the other kit? Also, the hats that come with the rotors should be fine. As for the brackets, I'm trying to find out if the same one will work for both. Alloy...I realize the hubs in the 4th gen kit are useless to us. I was just stating the fact that they are included in the kit and it still costs less. The only additional item I see in your kit is the brake lines (which truly makes this a bolt-on kit). It just seems that the extra price of the 6-piston calipers and 2-piece rotors in the 4th gen kit would cost a good bit more than the brake lines.

So I'm basically asking this: Is it possible to upgrade to the 1.25" thick rotors with matching 4-piston calipers and have everything bolt up? I know you stated that they won't fit under stock 16" wheels but that isn't a problem for me. I have 17" SS wheels that should allow plenty of clearance. Thanks for all your input. I really appreciate it.

alloy

iTrader: (16)

The 6 piston caliper do have the same mounting arrangements, but have more offset to the outside causing them to interfere with 16" IROC wheels. And yes I do realize you have 17" 4th gen offset wheels. So do I. But this kit was made for people with stock 16" IROC wheels so they would not have to invest in 17" wheels and tires like the Baer kit that costs $700 more.

Now, let me ask you a question. What makes you think that a 1.25 thick rotor is better than a 1.100 thick rotor? Better cooling maybe? Well if that's your line of thinking it's incorrect. The 1.25 rotors are only .15 thicker, so .075 per side. Now this in itself does give more surface cooling area on the edge of the rotor than a 1.100 wide rotor, except that the rotors I supply with my kit are a full 13" in diameter. So, they have the same, or slightly more cooling area than the 1.25" wide 12.9" diameter rotors do. Surface area is the key to cooling. Again, SURFACE AREA is the KEY TO COOLING. Not rotor thickness.

The caliper bracket thickness in my kit is 1/2". This is the minimum thickness I would consider safe to use with such a powerful set of front brakes. To make the caliper line up with rotor hats that have less offset, you would need to make the bracket thinner. Much thinner. And, no one makes a off the shelf rotor hat that is hub centric, and has the right offset and wheel bolt pattern. You can buy raw blank rotor hats and fully machine them to fit, but as Matt said, do you have the machinery, (machining center-VMC) CAD/CAM system, and know how to do this? If not you will pay $$$$ to have it done on a one off basis.

Can you make this kit work on a 3rd gen, maybe so. But what will the cost end up being. My guess is considerably more than $1595. Time is money, and my kit saves time by including everything you need in one complete package. Bolt it on and go. (or stop in this case)

Steve91Z28 L98

The extra thickness and curved vanes of the 2-piece rotors would make up for that small difference in diameter. That's a difference of only 0.3" circumferentially (is that a word?). Not to mention the weight savings of the 2-piece rotor. I know they will cost more but it would be a nice option. To use these rotors would require a different caliper (part #120-7429 R/L) . The only difference is that this caliper is slightly wider to accommodate the thicker rotor. I guess this is where the interference with stock 16" wheels comes into play.

Would it be possible to put a spacer between the hub and rotor hat to move it to the correct position with respect to the caliper? I know this would push the wheel out even more but that's nothing that can't be fixed by turning down my wheel adapters on the lathe. The spacers would be extremely easy to make as well. Alloy, would you let me know if you think anything else would prevent me from using these rotors? Do you think the caliper would still sit correctly on the rotor with the same caliper bracket? Thanks again for your time and patience.

Matt87GTA

FWIW, I have always been told the same thing as alloy regarding more pistons... Going to 6 versus 4 piston (and so on) is to combat pad taper and not to gain in clamping force. By spreading the force out more evenly on the pad backing plate, the pad is kept in proper alignment with the rotor better.

As for spacers, slip on spacers should be avoided if at all possible. That being said, I wouldn't be all that afraid of running them as long as they were used in conjunction with good wheel studs/lug nuts and lug nut torque was closely monitored - and they were as thin as possible to get the job done (no more than 1/4" IMO).

Now, (assuming the problem is with the clearance between the caliper and the spokes of the wheel) if you put a spacer in between the hub and the rotor/hat, you just pushed the caliper out into the wheel even more as you would also have to space out the caliper to keep it inline with the rotor. If you put a spacer between the wheel and the hat (or wheel adapter), you would gain clearance for the caliper that you need. But going back and machining your wheel adapter down would again bring the wheel in and erase the clearance between the caliper and the wheel.

Steve91Z28 L98

The purpose of the spacer would not be to gain caliper clearance. The caliper would stay where is it but the backspacing of the rotor hat would cause the rotor to be positioned too far in (towards the spring). The spacer would correct this by moving the rotor out the correct distance to line it up with the caliper. I'm guessing that it would be no more than 3/8" max. A slip on spacer this size should be fine. Turning my wheel adapters down would move the wheel back in the same distance as the spacer. There should be no clearance issues with the spokes of my SS wheels. I can see how there could definitely be some problems with this clearing the IROC wheels though.

355SS

iTrader: (1)

I am pretty sure that you can not turn down a wheel adapter to 3/8 thickness. Rotor thickness does cool the rotor face it acts like a larger heat sink since there is more mass to the rotor. Rotor thickness aids in cooling buy allowing more air to be pumped through the vanes and makes for a more stable rotor.

MrDude_1

and by that logic a 3" rotor becomes ideal, but a 4" is better right?

there comes a point where the diff between two is minimal.

not to mention the added unsprung spinning mass isnt the best thing for handleing.

alloy

iTrader: (16)

FYI: The rotors supplied with my kit are curved vane rotors.

355SS

iTrader: (1)

Mr. I am not understanding what you are saying. Alloy said that rotor thickness has nothing to do with heat dissipation, which is false it is as important as if not more than diameter since you gain surface area by increasing the thickness. You gain leverage with the larger diameter rotor, but heat dissipation is based on surface area and rotor stability on rotor thickness. You can gain surface area by increasing rotor thickness or by increasing the rotor diameter. The rotor dissipates most of its heat through the pumping action of the air through the vanes not from the rotor face. The rotor face is almost a mirror finish so it reflects its heat and does not dissipate much through the face of the rotor also not much fresh air passes over the face. Alloys kit looks fine for what most will use it for. I am not sold on the wilwood calipers for a street car but that is just me. The only production high performance vehicles that come to mind that came with 1.100” rotors were the cobra and ZR1. Baer uses the same-dimensioned rotors for 2 of its kits but when you get into the higher priced kits they switch to 1.25" thick. Production cars with 1.25" rotor that I can think of are Corvette C5, Porsche 911TT, Ferrari, and Lambo. Nascar uses 1.25" and 1.38" rotors. I guess my point is that rotor thickness is very important when you really start pushing your brakes hard. I have seen C5 owners switch out there stock rotors for Porsche 993TT rotors, which are the same diameter and thickness as stock but have more vanes and are seeing improved braking when racing. I am not trying to start a war but just trying to shed a little more light on the subject. When I was looking for brakes for my car I wanted the best I could get and nothing was available that I was happy with so I designed my own. I have done a lot of analysis on my brakes and even run fmea on the brackets and adapters.

Dewey316

i think that you guys are using diffrent terms for what you want to describe.

the rotor thickness does not make it disapate heat any faster, the surface area gained is almost nothing, but what a thicker rotor does do, is give you more material, which allows the rotor to absorb more heat without the surface temp rising as much, the disapation is determined more by the surface area and the material the rotors are made of. of course larger rotors are going to make a diffrence in how long it takes them to get to the temp where the brakes fade, and how fade resistant they are. but that is due to more material to absorb the heat, not the disapation. in actuality i would bet that the 1.10" rotor will in fact cool down faster than the 1.25" rotor, due to less heat being stored in the material, but it will reach a temp where the brakes fade a little faster.

alloy

iTrader: (16)

If you read my post carefully, I'm comparing the difference of a 1.250" thick rotor that's 12.90" in diamter and saying that there is no more surface area for cooling with the 1.25" rotor than my 1.100" wide 13" diamter rotors I supply with the kit.

Take into account the entire paragraph before taking a statement out of context and calling it false.

MrDude_1

*shrug*


is there a point to any of this anyway? the brakes are already overkill enough as it is..... its not like you're going to over heat them enough to notice the diff between thoes two anyway.. even on a good track day.

*shrug*

355SS

iTrader: (1)

Alloy I did read your entire paragraph so let me try to explain what I said better. You only gain 4" of surface area when you go from 12.9” to 13". When you increase the thickness of the rotor from 1.10" to 1.25” you gain more surface area. I am using some dimensions off of the top of my head so this will not be 100% accurate. I am using a rotor with 48 vanes that are 2" long (the face of the rotor is 2" tall so the vanes will be slightly longer since they are curved). You will gain surface area on both sides of the vane so here is a rough calc. 48vanes x 2 sides x 2" long x .15" increase in thickness = 29" more surface area. To cool the brakes it is more important to bring air through the vanes since this is where there is the most surface area.

Steve91Z28 L98

I wasn't talking about turning my adapter down all the way to 3/8". I said the spacer would be about 3/8" thick and I would take that much off of the adapters to compensate.

I didn't realize this, alloy. Do you have anymore pictures of the rotors? A close up look at the back of the rotor and on the vanes would be nice.

AgoodV6

Size of diameter and size of thickness both aid in disapating heat. The larger diameter gives more surface area to distribute heat from the pads. The thickness absorbs the heat inward towards the vents and aids in preventing warpping (overheating)