heinzboehmer's 2002 Topaz 6MT Coupe

[Obioban]

Every time I go off stock drivetrain mounts, of any sort, I regret it.

[heinzboehmer]

Those VT mounts are crap

Yeah they really weren't great

[maupineda]

Oh! Forgot to comment on control arms and engine mounts. There is a noticeable difference in steering feel with the lemforder control arms. Very happy with that.

Also hard to believe I put up with the vibratechnics engine mounts for so long. It's so nice to be able to sit at a light without the car trying to shake itself apart whenever the AC compressor comes on.

Those VT mounts are crap

[heinzboehmer]

Nice update! Yeah, the bleeder thing happens on other calipers as well.

Yeah makes a lot of sense. I'm surprised it hasn't happened to me before on other calipers.


Also, quick pic dump of what the car looks like now:








I'm really enjoying how stealthy the calipers look, glad I went with black.

[Slideways]

Nice update! Yeah, the bleeder thing happens on other calipers as well.

[heinzboehmer]

So this is what I saw when I took a quick look at the calipers yesterday morning:



As mentioned before, not super alarming, but still wanted to figure out why some bleeders appeared to be leaking.

Decided to remove all the bleeders and reclean the taper that they seal against. Calipers were fully dry when installed, so there was a possibility that some dirt/debris I hadn't been able to clean out had accumulated around the taper and was making the bleeders not seal well.

After doing that, I pressure tested them by pushing on the brake pedal as hard as I could for ~30s. Found no leaks on any of them

At the same time, I also decided to cut the dust caps in half, as I don't really like the design of them. Having the retaining ring sandwiched between the bleeder and caliper makes it hard to feel the torque on the bleeder and also means that the dust cap gets caught and spins around.



Left a little tab of material to make it easy to pull them off.

When I went to reinstall them, I realized why I had seen brake fluid pooled around the base of the bleeder. Here's what happens when you install them:

As you can see, installing the dust cap forces any brake fluid left in the bleeder past the threads. Makes sense since these things seal at the bottom taper and not on the threads. Something like this is what's happening:



This was super easy to see with the dust caps cut in half, but much harder when they're installed unmodified. So leading theory is that when I initially bled the calipers, there were no leaks, but there was some brake fluid left in the bleeders that was pushed out by the dust caps. This must have pooled under the dust cap retaining ring —making it hard to see when cleaning up— and eventually dripped out when I took the car out for a drive.

Anyway, mystery solved and fortunately there aren't any leaks on my calipers!

Also, for completeness, here are the weights I got for all this brake stuff. Weight are per corner and things labeled "caliper" include everything (pads, spring clips, brackets, brake lines, etc.).

Front 996 Caliper	9.4 lbs
Front ZCP Rotor	18.9 lbs
Front Stock Caliper	14.5 lbs
Front Stock Rotor	17.5 lbs
Rear 996 caliper	7.9 lbs
Rear ZCP Rotor	15.1 lbs
Rear Stock Caliper	8.7 lbs
Rear Stock Rotor	16.2 lbs

So 3.7 lbs saving per side up front and 1.9 lbs saving per side in the rear. Not bad.


I did have another thought as well. Like any good scientist, I changed only the bare minimum between measurements (track days) in order to be able to attribute any tangible differences to a single variable. This is what will have changed on the car from last track day to the one I have booked in ~2 weeks:

• Replaced front control arms
• Replaced engine mounts
• Installed slon rear wall
• Swapped stock rotors for ZCP rotors
• Swapped stock calipers for 996 calipers
• Bought new track pads I haven't tried before (PFC08)
• Bought new wheels I haven't tried before (more on that later)
• Bought new track tires I haven't tried before (more on that later)

Sooo it's basically like I'm bringing another car out. Great.

[heinzboehmer]

Oh! Forgot to comment on control arms and engine mounts. There is a noticeable difference in steering feel with the lemforder control arms. Very happy with that.

Also hard to believe I put up with the vibratechnics engine mounts for so long. It's so nice to be able to sit at a light without the car trying to shake itself apart whenever the AC compressor comes on.

[heinzboehmer]

Finished up the install yesterday and took the car out to bed the brakes.

Decided to connect the power bleeder and pressurize it to ~3 psi when swapping brake lines. Worked great to keep air out of the lines, but man was it messy. Anyway, the install went pretty smoothly, not a lot to report from it.

Brakes feel pretty great. Reminds me of the brake feel of a 981s that I drove around for a few days recently. I think there's still a bit of air in the system, so I'll drive the car around some more (to knock any stubborn air bubbles loose) and rebleed this weekend. Should give me the super solid pedal I'm looking for.

I did also test fit my front track wheel to see if I have enough space for brake ducts v2. Looks like there's tons of room:






I'll be alright if I just mostly follow the caliper radius, as shown in that last picture. Will start on the design work for these things soon.

I did unfortunately find the rear caliper bleeders slightly wet this morning. Didn't have time to investigate, but I guess wheels are coming off tonight to inspect all of them. Hoping it was just inadequate clean up after bleeding (I was running out of brake cleaner and was trying to use it sparingly) and not an actual leak.

[heinzboehmer]

Any reason you left the dust shields on in the first place? I know Essex recommends deleting them as a first step before trying brake ducts. Been meaning to get rid of mine for a while but the car is seeing less and less track use.

Mostly to keep dust under control. I also do like that they offer some heat shielding for the suspension components.

[repoman89]

Any reason you left the dust shields on in the first place? I know Essex recommends deleting them as a first step before trying brake ducts. Been meaning to get rid of mine for a while but the car is seeing less and less track use.

[heinzboehmer]

Got a good amount of work done over the last few days.

Started with the front brakes. Before:



After:



I did have to grind both front hubs down a little, but it was no big deal. 30 seconds with an angle grinder was all it took:



Here's why I'm planning for brake ducts v2:



That wavy cast part is the rotor hat that extends inboard and almost entirely blocks airflow to the rotor ring. I'll run these same brake ducts for my next track day (because I won't have time to get the next version done), but yeah these need updating.

Then I did the rears:



I thought these were much more annoying. There's less space everywhere and cutting the heat shield was a tedious job. But all in all also not a super difficult job.


While the car was up in the air, I also did a few other jobs I've been meaning to do for a while.

First, swapped out front control arms and engine mounts. For some unknown reason, I previously used uro control arms when I did my rod bearings. I've been wanting to swap them out for a long time, but had been lazy. Similar deal with engine mounts. Had vibratechnics in there and grew tired of the increased NVH pretty quickly.

Fortunately, only took me a couple hours to do both. Used an engine support bar to suspend the engine and then lowered the subframe a bit. Doing this made the job sooo much easier. Unfortunately no pics, but you can see one of the brand new control arms in some of the pics above. For the engine mounts, you'll have have to believe me. Very excited to have a smooth idle again.

I also added a second exhaust brace like Bry5on suggested:



Another NVH upgrade!

Anyway, only managed to do the hydraulic part for one of the calipers yesterday. Hopefully I can get the rest done today and then take the car out for a spin.

[heinzboehmer]

Air would have to get sucked out of the caliper with this setup

Looks like Range Rover does something similar for the SVR:





However, as far as I can tell, these ducts are designed to push air into the caliper instead of pulling air out.

I guess I could also swap rotors from side to side on my car and do the same. Don't love the idea because the rotors (and entire sprung assembly, really) are designed to pull air in through the center of the rotor and evacuate it along the circumference. Plus, active brake temp monitoring and cooling sounds like a much cooler project


Anyway, track wheels have arrived and I have a friend who just got a 3d scanner, so I think I need to finish up the brake swap and then get the car and wheels over to his place. With the area scanned, I can start doing some CAD work and decide whether this is even feasible under 17s.



Edit: No surprise, some racecars do this too. Pic of the 488 challenge front brake below. Looks like this one also pushes air into the rotor:



This is likely what my design would have to look like. Basically just follow the radius of the caliper so that there's no interference with the wheel. No hump over the caliper like the Mustang and Range Rover solutions. Would likely go for a fully enclosed design though, skipping that opening over the pin that this one has.

[heinzboehmer]

Interested in seeing how the fronts look. Should have them disassembled by tonight.

Alright finished disassembling. Fronts looked much better. Ended up counting a total of four ripped seals.




I also bought some Krytox 205 to use as assembly lube, on recommendation from some friends. Ran a quick experiment to test it out. Popped a piston out and then reinstalled with just brake fluid. Needed to use a good chunk of my body weight to get it in. Then cleaned up piston and bore and coated in Krytox. Was able to get the piston in by just pinching the caliper with my thumb and index. Crazy how much of a difference it made.

Good to know that this was installer error and not an issue with the seals. And as I said before, good lesson to learn.

[heinzboehmer]

Also, I was at laguna seca for car week stuff this past weekend and Ford had a display with parts from that new homologated GT3 mustang thing. This is what the rear brakes looked like:




Given the design of the front CSL rotors, my current brake ducts will be way less effective and this design looks super appealing. I don't know if I'll have enough clearance under 17s to do something similar, but it would be super cool to build something like this. Air would have to get sucked out of the caliper with this setup and I can think of two ways to do this:

1. Build an active system that pulls air out with a fan at the end of the brake duct hose. This is appealing because it can get combined with a temp sensor to make sure that the pads are always in their optimal operating temp range. Can also log individual caliper temps.
2. Build a passive system with a venturi tube or similar that creates a vacuum in the brake duct hose so that air gets pulled out at speed. Simpler than the active system, but no control over caliper temp, some added drag and potential for overheating on lower speed tracks.

Just brainstorming right now, but thought the design was cool and would make for a fun project.

[heinzboehmer]

I thought the seals felt too tight when installing the pistons...

This is the only seal that was obviously bad when pressure tested, but now I don't trust any of the others. I really don't want to find out that another seal is ripped while on track, so I've decided to rebuild all of the calipers again. New seals are on their way.

Fully disassembled the rears. 3 out of 8 seals were ripped, yikes. The other two I found weren't ripped as bad as the one that inflated the dust boot, but still. I'm glad that one failed catastrophically, otherwise I wouldn't have taken these apart.

Interested in seeing how the fronts look. Should have them disassembled by tonight.

Also, found a good way to pop the pistons out:

1. Leave the caliper fully assembled and stuff some wood/cardboard in such that the outboard pistons can't move much and the inboard pistons contact the wood/cardboard right before popping out.
2. Pull inboard pistons out with fingers. Should be easy to do if step 1 was done correctly.
3. Remove crossover pipe and replace with a bleeder in the outboard port.
4. Stuff some more wood/cardboard in such that the outboard pistons contact the wood/cardboard right before popping out.
5. Pull outboard pistons out with fingers. Should be easy to do if step 4 was done correctly.

The above approach was much faster than what I did the first time around and there's no risk of damage to the pistons when prying.