[BillG2A]

I have experienced very high front brake temperatures using stock 340mm rotors Moutol 660
And Hawk DTC 70 pads at longer tracks like Road Atlanta. Calipers discolored and piston dust seals appeared compromised.

I installed Porsche Gt3 open ducts on front thrust arms to direct air. That helped some but am looking for more.

A little research I took measurements and mocked up a few different configurations with cardboard and paper then ordered from Pegasus and summit . I am now doing final fitting using CF duct tape and the parts: 3" double walled hose , partial backing plate/spindle flange with 3" Outlet and 3" ring and clamps.

The goal was get air from front bumper /inner wheel well duct to the inside rotor hat. There is not much room but enough. I am close to having it fit with 235/40/18 front tires with a 20" length of 3" hose. It is a good fit but I am getting rubbing at full lock right (picture #5 upper left hand corner) I believe if I swap out the round flange I have on the inner wheel well to a NACA angled duct I can clear the tire at full lock wish me luck

Also I recently installed 380mm F8x m2/m3 rotors using brackets and stock rotors That should give me more gear sink a larger center hub and better inner rotor vane design to pump air through rotors.

[ggggbmw]

A valiant effort and I wish you luck. Is there any way to get the hose outlet closer to the inside of the hub? The 3rd picture looks like the outlet is facing the inside brake surface, and not the center of the brake hub. Also looks like a fair amount of flange on the hub side of the outlet that could be trimmed if there is any inside clearance.

Also curious what wheel studs those are. They don't look like anything else I've seen.

[BillG2A]

Appreciate your comment - the hose is currently positioned toward inside rotor surface which is undesirable. , I can trim about 1.5 " from the bottom of the spindle duct and otherwise position it lower on the hub for better alignment with air to hat. See pictures below for final targeted placement. These spacers have ~ 3" inner diameter. Also note I just installed SPL mono balls (last picture- not easy)


Looks like About 60% of air would be directed to rotor hat I may also weld a metal or insert a plastic diverter inside hose spindle bracket to direct 100% of air to hat. Removing the backing plate completely is preferable to have a cooling hose to the rotor surface, which would likely lead to crackled rotors

The stud conversion kit is by TPI These are Grade 12.9 carbon steel race studs. I found them at Tirerack last year for $39. I should have bought 4 sets. TireRack said they overbought quantities for their test fleet of BMW's And had them on clearance TPI shut down during COVID and while open now does not make these
I just bought backup stud set Grade 10.9 for $150 from Turner

Bill

[ggggbmw]

Originally Posted by BillG2A

The stud conversion kit is by TPI These are Grade 12.9 carbon steel race studs. I found them at Tirerack last year for $39. I should have bought 4 sets.

Dang. That would have been nice. I especially like how they have flats you can use instead of relying on double-nutting. I have the Bimmerworld studs, and they are nice, but very pricey. I'll have to make a note to look for the TPI studs the next time I need them.

[BillG2A]

Almost done - Got clear NASA ducts which move hose inboard a few inches. Cut spindle bracket to feed air more towards rotor hat.

[BillG2A]

Final remaining issue is that at full lock 235/40/18 front tires is making contact with duct. (See last picture below) It looks like I only need 0.5 - 1.0" more clearance. I can get that by moving the duct a little more inboard or by using a heat gun and reshaping the back of ducts

Final fitment coming soon

Bill

[jb-slow]

Have any pictures of the Porsche ducts? Where did you get the caliper brackets?

[BillG2A]

Here are pictures of open Porsche Gt3 brake ducts , brackets were from Kearn from Ohio he has a YouTube channel. Search my posts I posted his email address in a brake comment

Bill

[BillG2A]

Tested the M2/3/4. 380mm front rotors at Road Atlanta this weekend. Did not use full brake ducts and hoses. But did test fit/clearance of driver side duct - it was a fail , at full lock the tires tore up the duct. Picture below.

I refit using a heat gun to reshape the ducts for more clearance Front clearance is now fine but side clearance between tire and sway bar is not enough .
I reshaped the 3" duct / hose outlet to ~ 2.25 x 3.25
But have to thin it to under 2"

The good news was there was no brake fade with the larger rotors on the m240. I may not need the brake ducts

[LanceM26]

I discolored my brakes, what symptoms did you get from compromised piston seals

[BillG2A]

Hi I just edited my post to be more precise . The piston dust seal boot gasket looked compromised.
See picture below. The actual seals are inside the caliper look like flat "o" rings. Their job is to seal in brake fluid. It was the visual inspection of the dust boot gasket that had concerned me. The functionality of brakes was fine / not compromised
In fact the seals when I finally removed them were in very good condition.

I had read other member's track experiences which in the extreme included leaking calipers and a brake fire.

I bought rebuild kit from bimmer world and replaced the seals and gadgets

[pikcachu]

Did you have to remove the calipers to do the cylinder seal?

I did one of the dust boots in mine cause when i was swapping pads I noticed one had a puncture.... It was a pain in the ass to put the dust boot in.... seems like the caliper needs to be pushed out a bit and you need to use a couple of pick tools at the same time to prevent one side from coming off while seating

[BillG2A]

I did remove them from car and used compressed air to push out pistons. The seals were tough to remove. Hardest part was pushing out pistons at same time to a position I could remove them. They were very tight.

[edycol]

Titanium shims on pads?

[BillG2A]

Have not tried that

[edycol]

Originally Posted by BillG2A

Have not tried that

Try it. Titanium is worst heat conductor.

[aerobod]

Although for a metal Titanium has low thermal conductivity (25 W/mK compared with steel alloys in the range of 30 to 60 and aluminium alloys in the range of 150 to 250), brake pads are typically around 4 W/mK.

With 10mm of pad thickness, a 5mm steel backing plate and a 0.5mm shim, assuming steel conductivity of 45 W/mK, then a 0.5mm titanium shim would only reduce thermal conductivity by 0.34% compared with a steel shim of the same thickness.

[edycol]

Originally Posted by aerobod

Although for a metal Titanium has low thermal conductivity (25 W/mK compared with steel alloys in the range of 30 to 60 and aluminium alloys in the range of 150 to 250), brake pads are typically around 4 W/mK.

With 10mm of pad thickness, a 5mm steel backing plate and a 0.5mm shim, assuming steel conductivity of 45 W/mK, then a 0.5mm titanium shim would only reduce thermal conductivity by 0.34% compared with a steel shim of the same thickness.

ISK, I know a lot of guys on M2 are using it. Worth trying.

[aerobod]

Originally Posted by edycol

ISK, I know a lot of guys on M2 are using it. Worth trying.

Inconel would be better with a thermal conductivity 60% that of titanium and a similar raw material cost, but will also have fairly minimal effect in a thin shim.

[CSBM5]

It's not just the thermal conductivity of Ti that's useful (especially since the thickness of the typical plates/shims is very small to begin with, hence not a huge help in reducing thermal conduction)...the main thermal resistance added to the path from the backing plate to the piston(s) is from the two added thermal interfaces that the introduction of the Ti plate in the heat path creates. Additionally, the Ti plate shields the dust covers from "seeing", from a radiation heat transfer point of view, the hot backing plate surface. That Ti plate sort of floats 95+% of the time (until the transient brake application) with convection off it and runs at a much lower surface temperature than the backing plate; hence it is a nice benefit to protecting the piston dust covers in more ways than one.

[aerobod]

Originally Posted by CSBM5

It's not just the thermal conductivity of Ti that's useful (especially since the thickness of the typical plates/shims is very small to begin with, hence not a huge help in reducing thermal conduction)...the main thermal resistance added to the path from the backing plate to the piston(s) is from the two added thermal interfaces that the introduction of the Ti plate in the heat path creates. Additionally, the Ti plate shields the dust covers from "seeing", from a radiation heat transfer point of view, the hot backing plate surface. That Ti plate sort of floats 95+% of the time (until the transient brake application) with convection off it and runs at a much lower surface temperature than the backing plate; hence it is a nice benefit to protecting the piston dust covers in more ways than one.

Sounds like a lot of theory there, that would require controlled testing with thermocouples at each interface. The most important time for thermal conductivity is when the brakes are applied and any gap will be minimized under brake pressure. The rotors cool very quickly after that in the air flow. If they are up to cherry red at 900C or so, as soon as brake pressure is removed they go back to dull, dropping 500C or so in a few seconds, so any gap between the pad, shim and piston isn’t particularly meaningful when the brakes aren’t being used, the thermal capacity and conduction under brake pressure is much more important.

Fully blind testing with thermocouples on brakes either side with different shims fitted either side would be needed. I would be surprised if there is more than 5C drop on the back of a titanium shim 0.5mm thick compared with a steel one.

I’m sure manufacturers of them will claim otherwise as they have an expensive product to sell (even though the material cost by weight is only a couple of $), but they would need to provided properly conducted experimental results to show any meaningful improvement. Nothing to lose if they were $5 a set, though.

[dradernh]

Originally Posted by edycol

ISK, I know a lot of guys on M2 are using it. Worth trying.

If you'd like to try them, I have an unused set I got from another forum member. lmk

Originally Posted by CSBM5

...the main thermal resistance added to the path from the backing plate to the piston(s) is from the two added thermal interfaces that the introduction of the Ti plate in the heat path creates.

If I wanted to get the most out of a shim made from any material, I'd first have Swaintech's White Lightning applied to the pads' backing plate or to the backing plate side of the shims: https://swaintech.com/race-coatings/...aust-coatings/.