Persistent spongy brake pedal feel - 996/Megane/DB9 calipers

[Nate047]

Okay guys, I am struggling with a spongy brake pedal and I don't know where to go from here.

I have bled the system very thoroughly, several times over a period of weeks or months, including doing the ABS module service bleed procedure with three different Foxwell/Schwaben tools.

The car is an early MK20 car with DB9 front calipers and 996 rear calipers. I've heard of this issue happening with these and also Megane calipers.

There are no leaks or drips present anywhere. Calipers are all freshly rebuilt with new seals and hard pipes. Fluid is Liqui Moly race fluid. Pads are Hawk DTC60 (I know I know)

The pads bite and the car brakes fine, but the travel is a lot further than stock and the feel of the pedal is dog shit.

Where do I go from here? No joke, I have bled the everliving FUCK out of the car and this is as good as I can get it. Is this just how it is?

[jayjaya29]

Pads may not be bedded in yet.

Are you using a power bleeder or 2 person setup?

[Bimma360]

No that's weird, if anything it should be the other way around. I have the front and rear total piston area for half the caliper at:

Factory E46 M3 ZCP Front - 2826 mm^2
Megane RS275 Front - 2521 mm^2
DB9 Front - 2776 mm^2

Factory E46 M3 ZCP Rear - 1661 mm^2 (I understand the non ZCP is smaller but I don't have that measurement at the moment)
996 Rear - 1322 mm^2

DB9 front / 996 rear combo, should be pushing slightly less volume than stock non ZCP. Aren't Hawk pads supposed to have a spongy pedal feel? I could be wrong but I feel like I have that in the memory bank somewhere haha.

[digger]

to me the pistons sizes seem normal for a 1" master, it isnt going to have a hard pedal but should be essentially same as stock. i would test the master or investigate if getting pad knock back

[maupineda]

I just went through this and took me a lot of effort to fix it.

besides the calipers you need good pads, what are you using?

[maupineda]

Never mind, just read it all.

the calipers you are using displace less volume so your pedal travel is reduced over stock, however, you traded clamping force for… I guess looks, stiffer caliper construction, ease of pad swap, better thermal management, etc.

the stock brakes do bite A LOT, and most parts bin BBK actually loose on the power department relative to stock.

the key is to maintain the same relative change front and rear, not so much for bias, but for feel also as the whole piping is calculated as a system.

the most important thing will be the pad themselves, some pads just don’t offer good feel particularly ceramics, and if you chose some of those low dust pads, good luck with feel.

The best is semi metallic compounds, or just OE.

the 996 rear calipers are just not the right option, they are designed for a lighter vehicle, and 300mm discs, they are a whopping 22% down on clamping force versus stock. You will be better off keeping your stock calipers on the rear with the front DB9’s and use a good pad, even OE textars will be better than any ceramic crap.

i went with 135i calipers front and rear and they have a super nice feel, firm pedal, and easy to modulate. A very nice upgrade from the 996 calipers I was running.

As others said, bleed it using a pressure bleeder first, then follow with an INPA ABS bleed routine, but seems you have checked this one in.

[Tbonem3]

I bled mine a lot and opened ABS ports. Bought the best lines. The DS2500 pads bite really hard once they're at least a little warm. Mine feel great, though the cold bite is no where near stock, and as mentioned, technically, there's less clamping force with boxster brakes versus stock.

[heinzboehmer]

Pads are Hawk DTC60 (I know I know)

Start here. I hated the pedal feel of these back when I used them for track stuff. Felt like there was a lubricant between the rotor and the pad when they were cold.

OE pads will give you much better feel when cold. I quite like the textars on my 996 setup for the street.

[powerbait]

I feel ya, I'm going through the same thing on my e92 at the moment, I switched from PFC 08 to the 331/332 compound and dead cold pads are sketchy, where as I 08 bit enough after one stop I'd just keep them in all the time. With some heat the 331/332 bite harder but I still have a longer pedal than desired. I get a little air out every time, very frustrating. I've tried pressure, two-man, one-man kits, everything, has me thinking possible MC, but it's only got 64k on it.

[Nate047]

Thanks for the feedback guys, here's some follow up info.

Pads may not be bedded in yet.

Are you using a power bleeder or 2 person setup?

I have done the bedding procedure outlined by Hawk, so as far as I know they are ready from that perspective.

I'm using a Motive power bleeder.

[Nate047]

No that's weird, if anything it should be the other way around. I have the front and rear total piston area for half the caliper at:

Factory E46 M3 ZCP Front - 2826 mm^2
Megane RS275 Front - 2521 mm^2
DB9 Front - 2776 mm^2

Factory E46 M3 ZCP Rear - 1661 mm^2 (I understand the non ZCP is smaller but I don't have that measurement at the moment)
996 Rear - 1322 mm^2

DB9 front / 996 rear combo, should be pushing slightly less volume than stock non ZCP. Aren't Hawk pads supposed to have a spongy pedal feel? I could be wrong but I feel like I have that in the memory bank somewhere haha.

I don't know if the pads are supposed to just feel this way, I wouldn't be surprised. I'm going to get rid of them, I have some Textar pads I can swap in when I have time to tinker.

[Bimma360]

I don't know if the pads are supposed to just feel this way, I wouldn't be surprised. I'm going to get rid of them, I have some Textar pads I can swap in when I have time to tinker.

Well that at least would eliminate that variable if it doesn’t solve it.

[Nate047]

to me the pistons sizes seem normal for a 1" master, it isnt going to have a hard pedal but should be essentially same as stock. i would test the master or investigate if getting pad knock back

I don't know how I would go about testing the master cyl, LMK how one would do that.

Pad knock back, I don't know but I believe no.

[Nate047]

Never mind, just read it all.

the calipers you are using displace less volume so your pedal travel is reduced over stock, however, you traded clamping force for… I guess looks, stiffer caliper construction, ease of pad swap, better thermal management, etc.

the stock brakes do bite A LOT, and most parts bin BBK actually loose on the power department relative to stock.

the key is to maintain the same relative change front and rear, not so much for bias, but for feel also as the whole piping is calculated as a system.

the most important thing will be the pad themselves, some pads just don’t offer good feel particularly ceramics, and if you chose some of those low dust pads, good luck with feel.

The best is semi metallic compounds, or just OE.

the 996 rear calipers are just not the right option, they are designed for a lighter vehicle, and 300mm discs, they are a whopping 22% down on clamping force versus stock. You will be better off keeping your stock calipers on the rear with the front DB9’s and use a good pad, even OE textars will be better than any ceramic crap.

i went with 135i calipers front and rear and they have a super nice feel, firm pedal, and easy to modulate. A very nice upgrade from the 996 calipers I was running.

As others said, bleed it using a pressure bleeder first, then follow with an INPA ABS bleed routine, but seems you have checked this one in.

I think at this point I need to try a pad swap before I ditch the caliper setup, but I get your points here. I may end up going back to stock or with something else.

[Nate047]

Start here. I hated the pedal feel of these back when I used them for track stuff. Felt like there was a lubricant between the rotor and the pad when they were cold.

OE pads will give you much better feel when cold. I quite like the textars on my 996 setup for the street.

I'm going to throw on these stock Textar pads I have, and if that resolves the feeling on street driving, I will go with something like a PFC 08 for track. I have those in my E36 and the feel is great, and I can deal with the noise and dust tradeoffs.