routing brake cooling ducts for A Bodies-need help!

[jetmech442]

Hey Team! I have the 11'' rotors and 2'' drop spindles from CPP, wilwood D52 calipers(wilwood BP-20 pads), stock lower arm , SPC adjustable upper, and the big hollow Hellwig SwayBar. Front tires are 285/35/R18. I went to the track for the first time in October, brakes did well-BUT thats mostly becuase I couldn't get more than ~80% bakes before the rear would hop Hard(installing bias valve next week). It was also 45F the whole day, so I'm attributing my brakes not fading to those two things.

I've read dozens of posts about cooling the fronts, what I've gathered so far
1) need to feed it into the center of the rotor
2) nice to have an extra duct pointing at the caliper
3) should feed from the center of the front air dam if possible
4) obviously try to reduce bends in the ducting as much as possible-the standard seems to be 3'' high temp ducting.


Great. Cool. So I slide under the car to start planning the routing path and I am just NOT seeing anyway to route the tubing into the center of the rotor. The tires juuust kiss the inner rail at full lock, so I can't hug the inner rail like the C6 vettes seem to do. I feel like SOMEONE has to have done this before....google images comes up with nuthin. I would sincerely love any hints or advice. I'm willing to get a little crazy with it if need be, I don't think it'll make it through the upcoming 100 degree track days without cooling.

[jetmech442]

Got some pics last night. I'm thinking maybe try not get a longer skinny duct to route upwards and come from the top of the frame rail and upper arm? There's 2.25 inch clearance at full lock,so not much at all.

[raustinss]

I'd say hop is more than likely suspension set up related , as for front brake cooling yep good luck unfortunately it's one of those easier said than done things. Lol if you and your wallet are on talking terms , upgrade to larger brakes ...13 ".

[jetmech442]

I'd say hop is more than likely suspension set up related , as for front brake cooling yep good luck unfortunately it's one of those easier said than done things. Lol if you and your wallet are on talking terms , upgrade to larger brakes ...13 ".

Hey raustin, good to hear from you again. I looked at 13'' brakes, but the multi piston calipers all have nearly 1/2 the area I have now, which would be a downgrade in total force that I would then have to make up in very aggressive (rotor eating) compounds. Plus, the lesson learned from the Nismo 370Z is that without cooling, the largest rotors will still overheat and fade.

Your comments about suspension got me thinking. so I had my Instant center set on 100%(plus or minus you know), but the car launches really level(no squat or rise), so I think it's about 100%. With Wilwood D52 calipers, and GM Metrics in back, I get 63/37 bias front to rear.

My ASSumption was that the rears got too much force, locked up and caused the bad hop. but maybe its a combination of too much rear, AND too much AS? I can drop the AS in ~30% increments. you think dropping to 70% might help?

[raustinss]

It definitely wouldn't hurt to try it . You definitely want the rear to squat. As for the brakes I see what you're saying about piston "contact" area . I was kinda going off the basic idea of bigger rotors will dissipate the same thermal input better . Maybe my suggestion of 13s wasnt quite right but , I believe you follow my logic

[raustinss]

Oh ... one kinda crazy ass idea you could look into , I forgot I jammed this one into my brain yrs ago lmao. Mark Stielow took a Detroit speed subframe and welded a "divider " inside the frame rail then cut a hole in the side of the rail , used the front frame opening as the intake and used the frame rail as the brake cooling duct . I'd suggest google ... maybe someone here can recall . I swear it was on here I saw it but I could be wrong

[jetmech442]

It definitely wouldn't hurt to try it . You definitely want the rear to squat. As for the brakes I see what you're saying about piston "contact" area . I was kinda going off the basic idea of bigger rotors will dissipate the same thermal input better . Maybe my suggestion of 13s wasnt quite right but , I believe you follow my logic

Oh, I definitely follow your logic. I hope I didn't come off as snippy. A racer friend from work just had me read the Motor Trend article about the 370Z and how even going to 13 inch rotors it couldn't last more than two sessions cuz there was no Cooling. And I figure since my car is even heavier than the Nissan and only 11-inch rotors, that I should focus on air flow first.

[raustinss]

Definitely didnt come across as snippy nor was it even remotely considered to be... so you settle down over there lmao . I've never heard anyone over hearing Z06 brakes on a A body unless they're tracking the ever living snot outta the car ,I'm doing ZR1 brakes on my car which is insanely overkill .

[jetmech442]

Oh ... one kinda crazy ass idea you could look into , I forgot I jammed this one into my brain yrs ago lmao. Mark Stielow took a Detroit speed subframe and welded a "divider " inside the frame rail then cut a hole in the side of the rail , used the front frame opening as the intake and used the frame rail as the brake cooling duct . I'd suggest google ... maybe someone here can recall . I swear it was on here I saw it but I could be wrong

I searched stielow's 'gram for about half an hour, but the dude has built a ton of cars! I get what you're saying though, maybe sneak the tube inside and have a short ninety pop out inside the safe zone. Lots a factory holes in the frame so I think I'd need the tube. I'll check it out, thanks for the idea.

[raustinss]

Np ... let us know how it works out . When mark did it he just used the frame rail as the tube , if memory serves it was a Detroit speed subframe

[vette427-sbc]

One of the benefits of the SPC upper arms is that you can run a brake duct through the middle of the arm... keeps it away from the tires at full lock, but routing after that can be kind of tricky. I’ll see if I can dig up some pictures of how I ran mine

[c4racer2]

Can you run 1LE 12” rotors ? Should work with the D52. Maybe a different bracket ?

I would put energy into that before ducts

[vette427-sbc]

[jetmech442]

I'm checking out the webs to see if a bracket exists to keep the D52's with the 1LE. I see a lot of stuff for "b body" spindles but those would be a step back from where I'm at now. I don't think the 12'' rotor will make it through a 20 minute session by itself, but I think any increase to thermal mass(especially if I dont get them cross drilled) will help delay overheat. Thanks for the suggestion, I'll post what I find.

[jetmech442]

Hey Chris, thanks for the pic. The 3'' duct I bought is a squeeze at ride height, and crushed at full droop. Not too worried about full droop, but constant small bump rubbing might cause an issue. I'm going to see if I can weaken the internal metal spring so that it's not so much force to run compress it. Thanks for the direction, I'll post some pics in a wee bit.

[c4racer2]

12x1.25 is a decent rotor size. Not ideal. But track worthy. The D52 are decent calipers too.

[vette427-sbc]

The 1LE rotors are the same size (if not the same rotor) as a '65-82 corvette rotor... They hold up pretty well on corvettes as long as the rest of your equipment can handle the heat. I had stock rotors, stock calipers, titanium carbide thermal backing plates, brake ducts fed into the center of the rotor, Hawk HPS pads and ATE Super blue fluid... I could last about 15-20 minutes on road course before the pads faded (no fluid boiling!). My car was ~3100lbs wet with 245/45/17 300TW tires. I switched to a Hawk HP+ pad and wider front tires but never got to really thrash on the car with that setup so no data other than pad bite when warm was far better.
Being that your car is heavier; good fresh fluid and some track worthy pads may get you by for ~20 minute sessions

[jetmech442]

12x1.25 is a decent rotor size. Not ideal. But track worthy. The D52 are decent calipers too.

I spent some time checking into this, I didn't realize that my current caliper bracket would be okay with the extra diameter, but it seems like that's the case. The rotor width being 1.25 instead of the 1'' might cause me trouble though. I'd rather not have to re-buy the D52's for 1.25'' rotors. Any way to get it to work without grinding the pad down,lol?

The 1LE rotors are the same size (if not the same rotor) as a '65-82 corvette rotor... They hold up pretty well on corvettes as long as the rest of your equipment can handle the heat. I had stock rotors, stock calipers, titanium carbide thermal backing plates, brake ducts fed into the center of the rotor, Hawk HPS pads and ATE Super blue fluid... I could last about 15-20 minutes on road course before the pads faded (no fluid boiling!). My car was ~3100lbs wet with 245/45/17 300TW tires. I switched to a Hawk HP+ pad and wider front tires but never got to really thrash on the car with that setup so no data other than pad bite when warm was far better.
Being that your car is heavier; good fresh fluid and some track worthy pads may get you by for ~20 minute sessions

That’s great info thanks! I think I’ll come in around 3800 with driver. ☹ I’m going to try and make it work by routing through the upper arms. I’ll post pics when I make some progress.