RF Chatter While Braking

[Norm Peterson]

Short tires could be fooling the ABS into thinking you were decelerating somewhat more rapidly than was actually the case. More tire revs per mile = faster dropping of tone ring teeth/second on deceleration even before considering the better grip that the Toyos probably have (once warm, at least). If there's an upper threshhold on decel in the ABS programming, you could be tripping it. Perhaps JusticePete knows more.


Norm

[mpsgolf]

RF seat chatter maybe???

[Lonewolf583]

Bahaha I needed that!

[JusticePete]

This occurs with the wheel straight or turned or both?

[Lonewolf583]

Originally Posted by JusticePete

This occurs with the wheel straight or turned or both?

Straight primarily...sometimes while trail braking in.

[JusticePete]

Do you ever see ICE Mode?

[Lonewolf583]

I hit up one of my "inside sources" at our favorite manufacturer and confirmed the ABS settings are proprietary and owned by Bosch. No way to change/tune the ABS. There is no decel limitation difference between Competitive Mode and Purist Mode. I suggested the settings/firmware might be different between the SS/1LE/ZL1/Z28 and how we might be able to swap them out; he confirmed the Z28 module should work and allow more aggressive decel rates.

Paraphrasing here: [When you change diameter you change the inertia. The ABS is tuned to ensure you don't lock the tire too fast and that you leave enough inertia for it to turn again when it releases. When you change tire grip or diameter you mess with the "tables" stored based on stock values. With CCM brakes, they have 50% more torque output than the stock brakes. They bite so quick the module says holy crap he WILL lock up soon and cuts me off at 0.6gs by activating the isolation valves. The only remedy for this is pumping the brakes to apply more pressure.

In all honesty your only way is what race car guys do.... pull module go full no nannies and install a proportioning valve. I know that's not what you wanna hear, me neither but not much left to do aside of deal with the bad abs miscalibration. Other thing is go z/28 module calibration and tire/brakes.]

[Lonewolf583]

Originally Posted by JusticePete

Do you ever see ICE Mode?

Based on what others have described I don't think this is ICE mode. The braking distance wasn't overly exaggerated and there was some serious rubber being laid down.

[Lonewolf583]

Originally Posted by Lonewolf583

Based on what others have described I don't think this is ICE mode. The braking distance wasn't overly exaggerated and there was some serious rubber being laid down.

I stand corrected...he seems to think this is ICE mode.

[Norm Peterson]

Originally Posted by Lonewolf583

I hit up one of my "inside sources" at our favorite manufacturer and confirmed the ABS settings are proprietary and owned by Bosch. No way to change/tune the ABS. There is no decel limitation difference between Competitive Mode and Purist Mode. I suggested the settings/firmware might be different between the SS/1LE/ZL1/Z28 and how we might be able to swap them out; he confirmed the Z28 module should work and allow more aggressive decel rates.

Paraphrasing here: [When you change diameter you change the inertia. The ABS is tuned to ensure you don't lock the tire too fast and that you leave enough inertia for it to turn again when it releases. When you change tire grip or diameter you mess with the "tables" stored based on stock values. With CCM brakes, they have 50% more torque output than the stock brakes. They bite so quick the module says holy crap he WILL lock up soon and cuts me off at 0.6gs by activating the isolation valves. The only remedy for this is pumping the brakes to apply more pressure.

In all honesty your only way is what race car guys do.... pull module go full no nannies and install a proportioning valve. I know that's not what you wanna hear, me neither but not much left to do aside of deal with the bad abs miscalibration. Other thing is go z/28 module calibration and tire/brakes.]

Thanks for finding and posting the above explanation. It's not just the Camaro that has a second ABS calibration intended for higher performance versions, so I think I've learned something here I can take with me elsewhere. Makes today a good day


Norm

[Lonewolf583]

Ha, happy to spread the knowledge. Now to be clear it'll still look to check if the module expected is what you have...you'll likely have a red ABS light on the dash but in theory it will work.

My buddy at work has an S197 mustang and said the Boss module is a hi-perf unit for him. Not sure how applicable that is for your 195, but still.

[Norm Peterson]

Mine is an S197 (albeit one of the early pre-Coyote 4.6L cars), and I think the more performance-oriented unit was intended for the Boss 302S (built specifically for World Challenge GTS, NASA® ST2, American Iron, don't think they come with a VIN). I'd expect a warning light; there's a different EPAS unit that supposedly lights the dash up like it was a Christmas tree on the morning of December 25.

Again, thanks.


Norm

[Lonewolf583]

Lol pardon me, that does sound right

[Norm Peterson]

Had to track that Boss unit down in the 'whole cars' section of one of the FRPP catalogs. I'd only been vaguely aware of its availability and that it was supposed to work better at truly extreme levels of braking. Which I take to mean R-comps such as what the Z/28 ran and what you'd run in ESP . . . or higher. At 1.0g braking and under (MPSS tires) and my individual braking technique (such as it is) I haven't had any need to chase better ABS behavior so I didn't know what was different other than what I could guess at.


Norm