IRS Brake & Other Options

[chrisarella]

So I ordered the IRS because of obvious reasons, but what I didn't understand was how limited the brake options were. From what I understand I can complete the IRS with an 8.8 center, Torsen diff, and upgraded axles from a company like DiscBrakesRUs. Optionally I've read I can get the Cobra Roadster R hubs and rotors as long as I get a special bracket for the clippers (right?). Is this the best option?

So far I found these options for IRS brakes (reading FAQs and searching):

10.5" T-Bird Rotors and calipers (cross-drilled and slotted optional)
http://www.discbrakesrus.com/make/fo...rdrearkits.htm

11.65 Cobra Rotors and Calipers (cross-drilled and slotted optional)
http://www.discbrakesrus.com/make/fo...brarearkit.htm

13 inch Big Brake Rotors & Cobra Calipers (cross-drilled and slotted optional)
http://www.discbrakesrus.com/make/fo...sforirs8.8.htm

So what if I want to run the car on the track? Sadly, I cannot find a 2-pot rear caliper anywhere. I didn't see any brembo or wilwood options. Are better calipers even necessary for such a light car? I would think so knowing when you run more power you increase the speed and produce more brake heat, and need to consider brake upgrades to counter-balance this. This car will be getting a Coyote aluminator 5.0 and may see upwards of 430hp/400tq with intake/boss-manifold/tune. I know many of you run more power than that so wondering what your experiences were on the track and street.

Also, what else do I need to be thinking about with the IRS setup? All feedback welcome.

And no offense to the other vendors. DBRU was just one source that had options. I'd love to see what you have too.

[Jacob McCrea]

Chris,
I would check out Gordon Levy's website, Levy Racing. He has a 4-piston Wilwood kit for the rear, with 12.2" rotors. I will probably install that on my Type 65, which will be a full-on track car. Whether that is too much, to little or just right for your needs, I am not sure, but I would check it out. I am not aware of any other higher-end options for IRS, but if they are out there, I'd also be interested in hearing about them. Also, there is a very informative thread on the other forum, under the Coupe subforum, titled "Better Brakes on a Budget," or something very close to that. It contains a lot of interesting discussion re: making the Coupes stop really well. I'd guess that much of the discussion also applies to the Roadster. I honestly don't have enough experience to give advice about what brake components will and won't work together, and I'd defer to those who have actually figured that all out.

[Bob Cowan]

Yes, options are kind of limited. The Cobra brakes have a bigger rotor. But the caliper is smaller, so it's kind of a wash.

I'm using Gordon's Wilwood kit, front and rear. Good balance, and high quality parts. The car will almost stand on it's nose. On the track, I can outbrake almost anyone.

Slots are good on the track. They act kind of like a cheese slicer, and remove a small amount of pad material with each pass. That keeps them from glazing. It also reduces their life span, and increases dust production. Life's full of trade offs.

Holes are for bling only. They do not increase performance, and Wilwod does not recommend them for racing.

Rear




Front

[chrisarella]

I agree 100% on your comment regarding cross-drilling. Truth is there are different quality cross-drilled rotors and the cheaper ones are dangerous. I for one have always chosen slotted-only.

Looking at those pics I am really shocked at how wilwood designed this setup though. In addition to the clamping force, the purpose of increasing the number of pistons is really to allow a larger contact area on the rotor to facilitate more friction. Looks like the willwood calipers barely increase the amount of surface area (if at all). Moreso, while the Wilwood rotors increase in diameter they actually have a shorter contact patch. So the 1-piston cobra pads cover almost the same surface area. If you look at the brakes on higher-end track and super cars the entire surface area is taller and wider. WTH Wilwood would design these this way is beyond me? I'm sure they are better, and I am merely speculating off of pictures (not real world testing), but thinking about this from an engineering perspective there seems to be a level of inefficiency in the design. Perhaps the amount of heat produced was too much to disipate so reducing the surface area was a compromise.

As for what I am looking for, I'd prefer calipers with 4 pistons in the fronts and 2 pistons in the rears, plus 12-13" rotors all around. I'm not looking to compete, track days will always be HPDE and club days, and 99% of the milage will be street. No need ot have the best money can buy. Perhaps Alcon, Baer, or Brembo has a nicer design but it sounds like beggers can't be choosers here. I'll ask Gordon what my options are.

Thanks all.

[Bob Cowan]

Interestingly enough, a larger pad area does not always improve braking performance. The purpose of the additional pistons is to increase the pressure applied to the pad, and then to the rotor. Increasing the pad size spreads that pressure out over a larger area, decreasing the PSI at that critical juncture. I found that interesting, and didn't believe it at first.

The Wilwood pad is clearly larger than the stock T-bird pad. Not by a whole lot, but it is larger.

Wilwood makes an excellent 4 piston caliper, but I have not seen 2 pistons.

Originally, I built the car with no thoughts of racing. I started out with stock T-bird brakes in the rear, 73mm single piston Ford calipers in the front, and Hawk HP+ pads all around. I think the brakes were excellent then. If you're not carefull, you can easily lock them up at speeds less than 40mph or so. If I was building a street car, I'd stick to the stock brakes and not look back. The only reason to upgrade is for serious road course use.