yessamgerg

Do you already have the calipers? if you are set on those calipers and with the front rotor you have you should probably go with the 11.75" (299mm) rotor with a 8x7" bolt pattern. That will put you in the bias range you need to be in while having a huge selection of rings from AP/PFC/Wilwood and many others.

DavidNJ

The 299mm 8-bolt x 7"rotors are the stock car rotors. The reason to use the stock car calipers is price. On ebay PFC ZR33's are over $2000/pair vs. ZR34's being less than $1000/pair. The APs about $700.

What bias range typically works for tracked S2ks? Is that with a square tire setup, lowering, and/or aero?

My calcs show the AP stock car setup has about 11.5% more forward bias than the stock setup. The PFCs a bit over 28%. The AP BBK from Urge with the stock rears is about 7%.

IMHO, for a stock/near stock HP car without aero on TW200 255-17 or 265-18 square tires this is probably overkill. Maybe Stoptech or Girodisc floating fronts with cooling ducts and Urge vented rear, both front and rear with stock calipers and appropriate operating temp race pads. The stock car brakes are on a 500hp similar weight car running the equivalent of 325mm square setup with racing slicks that have heavy braking every 7-8 seconds continuously plus run fender-to-fender in often heavy traffic.

R-Poizon

yes I already have the calipers with the pistons I give to you. i have the front rotors too. i just need the size of the rear to make the proper bias.

I did some reserch on the web and found some formulas to calculate the bias. so in my calculations and with same pad coumpound in 4 corners it would give to me 309mmm for the rear, assuming that i will use 323 rotor on the front.

Also the pad swipe oem is: front- 49mm and rear 38mm
and mine will be 47mm front and 40mm rear

can anyone confirm this if this is correct?

the is lowered on tein src 16kg springs all around. i will add aero later so it is wise to upgrade the brakes now because they will fade

yessamgerg

Another thing to consider is it would be very difficult (maybe impossible) to package anything smaller than the 11.75" rotor on the rear. You likely won't be able to have room for rotor mounting hardware on anything smaller. A bigger rotor would definitely be overkill (I run a 11.75" x 0.81" stock car rotor for my rear and it is plenty big for cooling and thermal mass. IMO it is the best balance of easy availability and size. You could go slightly bigger but that makes everything more expensive and heavy. If you PM me you email I can send you the bias calculator I wrote for my setup.

DavidNJ

For OEM I used in the front a 46mm high pad, 300mm diameter rotor, and 54mm piston. In the rear a 39mm high pad, 282mm diameter rotor, and 40.4mm diameter piston.

With the calipers you specified, with 323mm rotors front and rear, and a 51mm high pad, the combination has 7% more front bias. A 345mm rear rotor would return them to the OEM ratio.

Gregrocks, you seem to be familiar with late model stock car parts, have you raced them?

yessamgerg

I have not personally but I have a few friends that do. Keep in mind that most people will run 1-2 steps higher front friction material on the stock setup to tune the bias. This will shift the bias forward 2-4% depending on the pad manufacturer. Also the rear rotors tend to run very hot which will usually lower their output a fair bit, again the extent is depending on the manufacturer.

R-Poizon

Keep in mind that rear piston area are less than oem. Are you sure that is 345 rear rotor?

DavidNJ

What matters is the ratio of piston area and the moment arm (diameter of the disk and to a lesser extent, height of the pad. A larger area simply means less line pressure is required for a specific clamping force.

If you wanted the same ratio as OEM. But is OEM too heavily biased to the rear for your application? People with S2k track experience may have a better handle on the desired ratio.

Are you running in a highly competitive class or just track days? Why are you running a small front tire? Are you running race tires or near race tires (e.g. Trofeo R, RE71r)? Are you near stock power or is this a turbo motor making 400hp? Are you running a splitter, wing, hardtop or stock?

Andrew Wojteczko, who was a leading driver in the Canadian Touring Car Championship, build an extreme, turbocharged S2k a few years back. He used the same caliper piston sizes you specified using PFC ZR22 and ZR24 calipers he purchased used and rebuilt. He machined his own rotor hats to use the PFC Direct Drive floating rotor system (the precursor to the newer V3). His rotor sizes were 323mm in the front and a near OEM 284mm in the rear giving 23% more braking in the front, assuming equal line pressures. He replaced the pedals with a high-end

I believe he built the car to CTCC spec than sold it before using it. This was the article on the brakes. Is for sale ads are probably still on the forum. http://www.superstreetonline.com/how...0-honda-s2000/ In this second article, he discusses the selection and mounting of the pedals: http://www.superstreetonline.com/how...0-honda-s2000/

StopTech has(had?) a 2-piston rear kit. I don't know the piston size, but the rotor was 323mm x 22mm. The rotor with its hat may be a simple way to get rear rotor mounted.

R-Poizon

I'm just making trackdays. I had seen his project.my idea is based on his post. but he put the ap pedal box and some other extreme things to regulate the bias. plus he liked a bit of front bias because of slicks.

In my case i will be using oem abs and master cilinder brake. i would change my tires to wider ones in the future, maybe 255 front 295 rear. I have no class, its unlimited class. lol

so i know s2000 is a bit front bias based. that's why i need to know the size of the rear rotor to make the bias untouched.

I'm just pursuing the best stopping power with this setup.

I'm running with yokohama ad08r

DavidNJ

As I said, for track days I would just change the rotors, StopTech or Girodisc stock replacement 2-piece, and the Urge 2-piece rear. Stock calipers. OEM diameters. Add front brake ducting and race pads (a fairly big selection for Honda calipers, but not Hawk DTC 50 yet).

If it is a track dedicated car you will need offset ball joints on either the top or bottom to gain enough front and maybe enough rear camber. If you do that, 255/40-17 or 265/35-18 front's should fit with a wheel offset in the 60mm range. Wheels are available from several sources, and 17x9 is a standard for the STR autocross class. The TSW wheels look nice. The people into serious track day miles can tell you which ones have issues and which ones don't.

Which gets us back to brake bias. Ask what others who track and race cars similar to yours have found works best. For the most part they seem to shift a bit more to the front. A quick calculation would indicate that if you are hitting 1.3+gs in braking, you probably want a bit more to the front. Maybe quite a bit more. The limiting factor should be the tires.