CFMP RAblue

Does the ebrake still work?

Drew314

iTrader: (2)

Yes sir. E-brake still works exactly the same. The two drums in the rear rotors are the same diameter.

NFSLancerRA

iTrader: (8)

I know that I have been out of the game for awhile, but I just wanted to make one minor observation. While this modification definitely does work, the size of the X rear Brembo is somewhat less than ideal when used in conjunction with the CTS-V front (awkward fluid split). You will find that the AP-Racing kit for the X (which in turn uses stock X rear rotors) is just what the doctor ordered for Drew's front kit. Unfortunately, the same modification will need to be made to the supplied bracket, but in the end you are hacking up a 7075 Aluminum bracket (super strong) as opposed to an actual caliper.

I know that this modification is MUCH cheaper, and I certainly appreciate the simplicity. However, if I still had a Ralliart and did intend to race the car, I would use the AP-Racing rear (4-pots, BTW). It will perform the way you want it to, and it doesn't require hunting for X rear Brembos. For reference, the Brembo calipers that I will be putting on my X are identical (in fluid volume, at least) to the CTS-V 6-piston fronts. I will be using the AP-Racing rear. The price isn't bad as far as BBK's go, as well (sub-$2k).

Anyways, carry on. I like what is going on with RA's nowadays.

Drew314

iTrader: (2)

ERIC!
Welcome back, captain. Hope all is well on your end. Can you please double check your numbers on suggesting the AP racing rears are a better kit for the RA over the OEM X, even with my 6 pot kit? Those things are HUGE (only 10% smaller than OEM X FRONT Brembos). My front kit with rear X brembos causes about a 15% fluid shift to the rear. That is a pretty small number, and that is why it works so well together. The AP racing rears would cause a HUGE shift to the rear, over 50%! That would literally be like bolting up X front calipers to the rear of a RalliArt, and I would highly advise against doing so. Maybe the error is mine, so let me know if you come up with the same numbers the second time around. But as far as awkward fluid splits, the CTS-V front-OEM RA rear and the CTS-V front-OEM X rear are VERY close to OEM RA fluid distribution, not awkward at all. But putting that AP Racing kit in the rear would be the sheer definition of awkward fluid split, unless I have made an error.

NFSLancerRA

iTrader: (8)

Assuming that the X rear has 40mm pistons, that leads to a total fluid volume per caliper of 2513 sq. mm (20x20XPiX2). The AP-Racing calipers (confirmed by an engineer at AP-Racing) have four 27mm pistons. That constitutes an overall fluid volume per caliper of 2290 sq. mm (same method of calculation). Also note that they are designed to work with front calipers that are significantly smaller in fluid volume than the X stockers, which is nice, because the CTS-V calipers are a bit smaller, as well (5836 sq. mm => 5497 sq. mm).

Now, GM rear calipers go the other way (are significantly larger than X rears). The Z06 calipers that I used to use had 4 30mm pistons for a total volume of 2827 sq. mm. Take that for what it is worth, but on my car, I will be running the AP-Racing calipers.

NFSLancerRA

iTrader: (8)

Now, my math might be off, and what I am looking for out of my brakes is very specific to me.

Drew314

iTrader: (2)

Volume is cubic, so let's just use area, which is directly proportional to volume, since it falls out of the equation. You can't express volume in square mm. You have to be careful comparing fixed to floating calipers. Fixed have pistons on both sides of the rotors, but each piston moves half as much as a floating piston does. So calculating piston area for fixed calipers, you only use ONE side if you are using that to correlate to volume, as 4 pistons moving 1mm is the same volumetric displacement as 2 pistons moving 2mm.

Evo X is 40mm, so it is 20x20xpi=1256mm² (one side)

The AP Racing ones here?

http://www.apracing.com/product_deta...15-1003bk.aspx

Use the CP7615 (CP7600 series) caliper here?

http://www.apracing.com/product_deta...24mm_disc.aspx

that have four 38.1mm pistons, with a piston area of 2280mm² (one side), almost twice the size of the X rears. Click on the specification tab in the above link to see the piston size. If someone at AP racing told you that the pistons are actually 27mm, then I completely agree with you 100%. But every 4 piston caliper I saw on their website had 38mm or larger pistons.

NFSLancerRA

iTrader: (8)

Lol, I didn't catch that misuse of volume (I meant area). It has been a long week, almost Friday though, so no complaints.

The X-specific caliper in the X kit is actually an X-specific caliper (I couldn't find it on their website either) with confirmed 27mm pistons. You can independently verify that number at your leisure. That is why I called. I was shooting for something in the 2500 sq. mm range (approximately the same size as the X rear). My choice of front caliper hinged on the piston sizes in the rear, so I checked and double checked.

NFSLancerRA

iTrader: (8)

Edit: Sorry, I didn't catch that you stated that that calculation was for one bank, only. My bad.

Drew314

iTrader: (2)

Then I agree with you, whole-heartedly. They sure are pricey, though. I just don't have time on my hands to design a rear kit. Since the X rear and the RA rear are only a few mm difference in caliper offset, you should design a rear kit for both cars

NFSLancerRA

iTrader: (8)

You should have seen the final bill for my new block. Sleeving and everything was insanely expensive. Plus, the sleeves were completely custom, so the $'s started adding up really quickly; but I am confident that it was done right and will hold.

We are in the same boat time-wise. Between school and work, I just don't have the time to try and put something together for the rear. The front is always the easy part as far as kits go (and nothing is ever easy).

robyn402

iTrader: (3)

i suggest picking up 4 - 7/16" washers, i used ones that were 0.075" thick to get the bolts to clear the rotor

robyn402

iTrader: (3)

as i've recently discovered the thickness of the pads is extremely important

due to the custom nature of this kit you will need to ensure your brake pad is less then 13.2mm thick, this is total thickness including any shims

i'm going to be picking up a set of raybestos pads ... part number PGD 1368M, these measure 12.97 mm thick and will hopefully prevent fitment problems that i have experienced

the more expensive way is to machine approx 0.050" - 0.075" from the mating surface from where the of the caliper mates to the spindle, doing this will enable you to use a wider selection of pads including the ones i decided to use that were 13.97mm (much too big) and still have up to 0.030" of room between the rotor and pad when the piston is fully compressed


also small note to eliminate the need to grind down your mounting bolts (i used OEM evo x bolts), pick up 4 - 7/16" washers, ones i used were 0.075" thick

Japboi

Cant we just use the rear hub and caliper bracket from evo X and swap it to the ralliart?

Ralliart99

I am going through this mod myself right now. I have a complete set of front and rear hubs rotors and brembo calipers to do the swap. The evo has a different rear suspension all together.
to swap the hubs you would have to do an entire suspension swap including sub frame I believe. You can swap the front hubs btw.