does anyone know how the brake bias is controlled on the C6? I would guess it's electronic, since traction and stability control use differential braking. BUT, when the nannies are turned off, as I always do on track, is there a change in how the brakes are biased? My rear brakes are hardly even used, even as the fronts become toast

TIA,

Terry

 

Hi Terry

The front/rear brake bias works by PFM (Pure Friggin' Magic)!!!

I don't know how it works, but it works great!!!

I have never heard or seen any info that the bias programming is changed when different modes of the AH are engaged.

It's described in the Service Manual as an operation of the software in the EBCM.

The C6 up through model year 2008 has an ABS with components from Delphi. The Service Manual refers to the bias control system in the Delphi ABS as DRP (Dynamic Rear Proportioning).

Starting with the 2009 model year the ABS components are made by Bosch, and the newer Service Manuals call the bias system EBD (Electronic Brake Distribution).

I run with AH full on when street driving, and in Comp mode on the track. I drive track events for fun, and I gratefully accept any assistance the AH might give me so I can drive my car home. Actually, you can spin the car with AH on - I can tell you that from personal experience of several spins in Comp mode!! So I don't expect the AH to keep anything bad from ever happening, but it reacts 1,000 times faster than I can, and it can make corrections 1,000 times per second - something I could never do. If you're smooth when in Comp mode it will never be intrusive, and it might just help to save your butt.

If you're a pro driver doing W2W racing and drive 100%, and somebody else will fix the car when you wreck, then you need run with the nannies off so you can get every last 1/10th of a second out of every lap so you can get better podium finishes, a better driving contract, a better ride in a better series, and better sponsorship.

I do HPDE's for fun in my own car, so I see no need at all to run 100% all the time (but I drive the car hard!!!), and I'm happy to get help from the AH if I screw up - but again, you'll never feel it if you're smooth, and it will never make you lose an HPDE!!

As far as the rear brakes not wearing as much as the fronts - that's just the way it works!!!

When you brake hard the weight shifts forward, loading the front tires, and making the front brakes work harder. The rear lightens and the load is decreased on the rear tire contact patches, and the rear brake pressure needs to be reduced in order to keep the rears from locking up and causing bad handling problems.

if you're trail braking or maintenance braking, or even left foot braking to balance the car, the bias system will keep the proper amount of rear wheel braking so that the front/rear bias is just right for all conditions - it's PFM!!!

But when threshold braking, the front brakes are going to work MUCH harder than the rears. Take a look at the pics below from the Rolex 24 earlier this year - you can see the front rotors glowing, but the rears are much cooler:














.


You can light up the rears as well:




But, for most of your braking, the fronts are doing a much higher percentage of braking than the rears!!!



So....the front/rear bias is controlled by the EBCM software through DRP or EBD - and it's PFM and it works great!!!

I see no reason to turn the nannies off completely because AH is just not going to activate unless you're really rough or the car is doing something where you could really use the help of the AH.

And the front brakes do most of the braking, so your rear brakes are probably not going to wear nearly as fast as the fronts.

Bob

 

Hi Bob,

Thnaks for the very complete and informative answer. PFM--I should have known!

I'm a PCA/BMW driving instructor (15 years and still alive!), and I drive with all the nannies off, not because I'm rough, but because even in Competition mode, they will not permit me to put the power down as fast as I want to while exiting tight slow speed turns.

I DO tend to drive all-out. Even though Roger Penske has not called yet, I run with a bunch of buddies in Porsche GT3's in the instructor group, and we have a blast running nose to tail. I'm new to the Corvette this year--my full race Porsche 944/968 hybrid unfortunately had a fatal electrical fire last year--so I'm still learning the peculiarities of the Corvette. I can tell you this much-even with the Z51 package, the brakes are totally inadequate for the speeds we run. Porsche's Brembos spoiled me. But I do love that big V8 power!

Check out this video from a few years ago at VIR to see us having fun. http://www.youtube.com/watch?v=0hNPNNJdVQg

thanks

Terry

 

Ahaaaa - excellent video!!!

Did you make the National Corvette Museum event at VIR this year?

The end of June every year we have a couple hundred Vettes at VIR - I think it's usually right after a couple day P-car event. I make sure I get up there every year - its an event not to be missed!!!

If you didn't make it this year, you need to make sure you get there next June. It's all Vettes, and you'll run into a whole bunch of other forum junkies.

Hope to c'ya at VIR next year!!

BTW, you should come down to Daytona this fall and run one of the events on the Rolex 24 course at the Speedway. You can really turn the V8 beast loose on that track!!!

Bob

 

Thanks Bob,

Since that video was taken, I have moved back to Seattle. Here, we have some great tracks--Pacific Raceways, The Ridge, and Spokane, but VIR is still my favorite of all. I would love to run the Corvette there.

Here's a video from a few years ago of my Lotus Exige S at Spokane. http://www.youtube.com/watch?v=FwVVkw2eMv4. The Lotus handled great, but sort of hit an aerodynamic wall at 125 mph, which was just not fast enough. (Yes, I am an adrenaline junkie).

I'll post some Corvette videos once I get the brake problems sorted out. A couple weeks ago, the car boiled the fluid (brand new Motul pushing brand new Hawk pads) and I had to deliberately spin the car at 135 mph at the end of the straight. No warning--just foot to the floor. This was the second time the Z51 brakes have failed me, and on a relatively low speed track to boot (my 4-banger Porsche used to hit 160 at Spokane). No damage, but since both my 18-yo son and 25-yo daughter (she has 60+ track days) will drive the car next year, this type of failure is not acceptable. To put it bluntly, Corvette brakes suck for a 170+ mph sports car.

Today I wrote a very big check and next week I'll install a set of 6-piston monobloc Brembos and two-piece rotors on the front of the Corvette. My track priorities are always seats/harnesses first, then brakes, then shocks, and, lastly, more horsepower. Moton shocks and HP are on next year's list, funds permitting.

My bucket list includes joining the 200 mph club at Bonneville. I think the Corvette can do it.

See you at the track,

Terry