Crazy Brake Idea

[Lance Cheney]

Hello everyone,

I am looking at potentially upgrading my 11.6" brakes for track use. I have two sets of 16x7.5" wheels -- one with race rubber and one for street use. Not wanting to buy another set of wheels leaves me with only a few options, namely $1525 for a ShoStopper kit, or $1450 for a 12.5" Baer kit from Sho Shop. A third option that was open was to get the 2-*** PBR calipers and modify a bracket for the 13" kit so that it would work with the existing 11.6" rotors. Evidently this has been done with good success, but doesn't change the effective heatsink size at all.

Or, the fourth option -- which is why I'm posting. I downloaded the 13" SHO track brake kit template from Baer's web site. This template is designed to allow you to check clearance with your wheels prior to ordering the kit. My idea was that I would see if it were possible to 'trim' the setup down -- machine the rotors to 12.2-12.5", and modify the bracket to match. This would give me the advantage of a cheaper kit (eg. Midwest SHO - $599 for the 13" kit) with some advantage in the rotor size area vs. the 11.6" kit I have now. Evidently this kit uses the low-offset redrilled Cobra rotors, rather than the Corvette ones used by the SS/Baer 12.5" kit.

The template seems to indicate that if I took off 0.35" radius, everything would fit fine, making the rotor ~12.3" dia. It's an improvement over the '96 upgrade, and I get the bonus of being able to order the 412-sized Cobra pads, which are cheaper than the 598 size for the SHO. Although it's not nearly as good a solution as the Wilwood kit, I believe I could also still get 2-piece (Eradispeed) rotors so long as the hats were redrilled for the SHO bolt pattern.

Other than a rather major concern with the structural integrity of the bracket with the redrill, is there a good reason why this would not work?

Realistically I'm going to do some brake ducting first, and the installation of coilovers should help the rear to do more of the braking, but I'm exploring my options now and I haven't ever seen this brought up, so I thought it would be interesting to see what people thought.

-Lance

 

[Todd TCE]

Lance,

That change nets only .350" radius. The change is hardly worth the expense in my opinion. Slotting the brackets is iffy at best given the torque.

If you want to improve it as best you can with this type of set up then do up some same size rotors on two piece hats which are as wide as you can put in the caliper you use and make then directionally vaned too.

In the instance of heat, width is the issue much more than diameter. You might be on track to a modest change and it can prove worth it, but think it through.

 

[Lance Cheney]

Thanks for the comments Todd. My dad was a bit worried about it as well; even though the 'slotting' would take place axially and not radially, and therefore wouldn't have a ton of force on it in that direction, if there were any slop at all it would eventually fatigue. The braking force would try to rotate the bracket. I suspect -- given the importance of having the brakes actually work after coming down the front straight at Laguna Seca -- that maybe this isn't the best idea.

I'm a bit surprised that the 12.5" kit is so popular (or, I guess, even offered) given that one could make something like this with a custom machined bracket, 12"+ rotors, etc., for a significantly lower cost. Incremental cost over a normal 11.6" upgrade wouldn't be all that much. Though wheel fitment might not be as good as the existing kit.

-Lance

<small>[ January 15, 2004, 12:40 AM: Message edited by: Lance Cheney ]</small>

 

[cyanmauve]

The only concern that I would have with the modification of the caliper bracket is the amount of material that would exist between the stock bolt holes and the new, redrilled bolt holes. I used the PBR dual piston calipers with a bracket designed for a 13 inch disc and modified it to fit the 11.6 inch rotor. I drilled the new bolt holes 0.7 inch above where the origional holes were driled. Honestly, I was concerned with the lack of material that was between the old and new holes. For this reason, I wouldn't feel too safe drilling a new hole even closer to the old hole in the caliper bracket. Slotting/elongating the stock holes does not seem like a very safe option.

If you are not ready to buy the SHO Stopper package right now, and do not have the 17 inch wheels to clear 13 inch discs, I would encourage you to buy a set of high performance pads and stainless steel lines and retain the 11.6 inch discs. The stainless steel lines can be retained for future use with a larger brake package.

I cannot advise that you complete a potentially unsafe modification on such an important part of your car.

 

[Shoaz]

Lance,

Baer also makes a 12" kit (or at least used to make), which I think is just the 13" kit with 1" less diameter, i.e., same rotor configuration, offset, mounting, etc. This might get you where you want to go with the possibility of moving up to the 13" kit with just a bracket and rotor change. Todd has similar modularity with some of his kits.

I'll vouch for Todd's two-piece rotors, I have a set on my 12.5" Baer system, and they're holding up great. Just got back from a track event with them and no problems. Using Todd's hat system makes it reasonably easy to size offset, etc., and then get the rest of the rotor dimensions right (e.g., diameter) by sizing the rotor itself.

The 12.5" kit was one of the first out for the SHO, so it's been on some cars for a long time. It's also the most wheel friendly, since it has a deep offset and clears most 16" wheels. It's essentially the biggest kit that fits under a 16" wheel.

I'll also opine that it might be worthwhile to get your ducts in and then just see what you can do with the 96 brakes. The biggest step I made in brake performance was installing the ducts, and I did that after putting the Baers in. I've been wondering how much more I could've gotten out of the 96 brakes had I put ducts in while they were still installed. To be honest I miss the ease of maintenance, pad changes, etc., that you get with the 96 brakes. I've learned to hate the PBRs when it comes to pad changes.

 

[RStalveyARFF]

Look around on ebay. I just bought a brand new 11" PBR kit for $250 shipped. I too can't use 17's on Pearl due to my 16" slicks. It's a takeoff from one of the mustangs, so do a little research and you'll be able to find em! And could one of you go into detail with this "brake ducting"?

<small>[ January 19, 2004, 03:22 PM: Message edited by: SHO91MTX ]</small>

 

[Yamaha V6]

IIRC, the Baer 12" kit was actually 12.5", and cleared 16" wheels. They are indeed 13" rotors turned down, per Baer late last fall. As of that point, they would still make rotors that way, but would NOT make Eradispeeds in 12.5"

 

[Shoaz]

SHO91MTX:
And could one of you go into detail with this "brake ducting"?

I have duct work that goes from the fog lamp openings via 3" aluminum dryer vent to a 45 degree elbow that sits against the subframe just in front of the tire. Air coming in through the fog lamp opening is directed to the general area of the caliper.

Many systems go further than this and route duct work much closer to blow either directly on the caliper, the center opening of the rotor, or both. On the SHO it takes some creative engineering and expensive (i.e., heat resistant) duct work to get air directly on the caliper or rotor eye, so I opted for the simpler route, which seems to be working fine.

I've had heat related brake problems at the track with my SHO since it first started seeing track duty, and the ducts were the final step to curing the problem, which they've done quite nicely. And it's not quite totally cured yet, but the ducts have made a huge difference. Just removing the fog lamps helped, but the ducts have been great.

 

[Lance Cheney]

Ok, ducting sounds like the first order of business. I haven't boiled the fluid in the brakes yet in any track event (though the dust boot didn't last past the first, so it's definitely getting warm), so they probably have some margin left.

Thanks for all the inputs-

-Lance