Dirty Howie

So some of you guys kept mentioning ABS will kick in too easily running DTC70 with Nitto NT05 tires in this thread:

http://forums.corvetteforum.com/auto...hin-is-ok.html

First of all I ran them once already and didn't notice any problems. Maybe I'm too easy .... never hammer them.

BUT WHAT IS WRONG WITH ABS KICKING IN ?????????


DH

MJM

The computer is driving the car not you. You might want to rotate the car into the corner, the computer disagrees and overrides you, and you go straight off instead of making the turn.

I'm generalizing, combining ABS and AH, and over-simplifying but those are the basics.

If you turn all that stuff off you will be smoother, better, and eventually faster. Along the way you might flat spot some tires.

argonaut

On a cool day last fall I was on Shenandoah with CL RC8 pads and worn NT01 tires. All day long I was constantly into the ABS. I hated it, very disruptive. It gave me no confidence in braking and felt like greatly increased stopping distances (don't know if it did or didn't but it felt like it, which affects your driving). It was miserable.

Dirty Howie

I thought ABS keeps them from locking up so there shouldn't be any flat spotting tires .......... what am I missing ??


DH

Dirty Howie

Obviously, ABS is an aid to help control stopping. So why would it slow you down ????



DH

Bill Dearborn

Actually it can help you stop faster than if you lock up the wheels or have one wheel that is locking up and you are trying to threshold brake. No driver can threshold brake a car that has one wheel locking up. If the driver reduces pressure on the brake pedal it releases the pressure at all 4 wheels which may not be the thing to do. ABS allows you to keep the brake pressure high and it takes care of the wheel that is tending to lock up. On pavement you get your best stopping force if the tires are slipping around 17%. That means they aren't locked up but they are turning slower than they would if they were free wheeling. ABS tries to maintain that level of slippage.

As for it engaging prematurely due to the pads that is more of a driver feel type of thing. High torque pads require less brake pedal pressure and the driver has to get used to it. Even then you can still move the car around when ABS is active. That is one of the things it was designed for. To provide steering control under heavy braking. However, if you are into the ABS when braking and trying to turn you will exceed the tire's friction circle capability and the car will understeer. Same thing happens without ABS but the understeer is a lot more.

Bill

flink

ABS may not help much in smooth straight braking, but it really comes into its own over bumps and while turning.

If you brake significantly hard while turning (eg, thunderhill cyclone) without ABS, the inside tires will (must) lock up, because there's little weight on them. The car remains controllable and there's not a lot of flatspotting because the tires are unloaded, but it still isn't very good for them. With ABS, the brakes on the inside wheels are backed off and all is good.

And if there's a bump in the braking zone (eg, Laguna corkscrew, Buttonwillow buttonhook), the tires will lock up as the car departs the bump, when the tires unload. And because a skidding tires generates less traction, the damn things STAY locked up as you land on the other side. You end up in the weeds, covered in flatspots. Without ABS you must manually modulate the braking over that bump, which gets tricky if you want to heel-toe there at the same time! Again, ABS will save you.

And as for driving on a wet track without ABS

From the above comments it sounds like the vette ABS is rather sucky. I found the ABS on the GTO to be really good - it just backs off the line pressure when it needs to and doesn't do anything else, no fuss. Which is strange, because I think it's basically the same (bosch?) system.

jlutherva

My objective for the last several events was to not engage the ABS - to threshold brake well enough to just be on the edge. The ABS just upsets the car way too much going into a turn.

I ran a couple of events last year where the track was hot and greasy and I was in the ABS just about every hard braking zone.

I've finally improved my threshold braking and I'm hoping that carries over to this season.

Jim

Dirty Howie

Bill

I think because I have always braked with a slow but steadily firmer pressure (vs just 100% all at once), I had no problems with them.


DH

Dirty Howie

Sounds like a lot of reasons not to worry if I am into the ABS


DH

Dirty Howie

I think I am the same way but if I brake too hard or there is some track surface reason for the ABS to kick in then thats good not bad.

So I'm still confused as to whats bad about ABS that everyone is referring to with the DTC70/NT05 pad setup.


DH

MJM

If you turn off the ABS and you jam on the brakes, you could flat spot your tires.

mgarfias

My guess is that they're saying there is more brake available than the tire has traction, so they tend to just go into ABS immediately.

You lose some of your ability to modulate the brakes in that respect. I.e.: if you push on the pedal with 50lbs of force and you go into ABS you have 0-50lbs of modulation available. If you switch to a different pad and go into ABS at 100lbs of pedal pressure, then you have 0-100lbs of modulation available.

BEZ06

argonauat said
The contact of the tire with the road surface is what stops the car (or turns it, or accelerates it).

You can have the biggest BBK, the most massive heat sink rotors, the most aggressive pads, and if you're running bicycle tires the ABS will activate with even very light brake pressure because with such a little contact patch the brakes will over power the tires and tend to lock up rotation every time you touch the brakes.

OTOH, you can have the biggest and stickiest tires you can find, and if you're running bicycle brakes you'll blow the brakes out the first time you stomp on them.

I hope on the skidpad they're going to have at the NCM HPDE at VIR that they'll run some ABS exercises. If not, try it yourself on a wet empty parking lot sometime after a rain shower.

Pull the ABS fuse, accelerate to about 30mph, stomp on the brakes as hard as you can, and do a lane change manueuver. The car might rotate a little, but you'll basically just skid straight ahead.

Put the fuse back in and try the same maneuver. You'll be able to easily steer from one lane to the other and come to a quick stop with no drama in complete control of the car.

Like Bill said, the ABS can do things that a driver is completely unable to do (unless you have 4 feet and 4 brake pedals - one for the brake at each wheel). The ABS can release pressure to a single wheel that is starting to lock up due to being lightly loaded, and the driver just cannot do that.

For you highly experienced racers, maybe you've got such a feel for the car that you can do better than the ABS.

For those of us that only get to the track a few times a year, the ABS is a good thing.

The tires and brakes work together. If your brakes are too big and tires aren't sticky enough, you'll be into the ABS often. If you have sticky track tires but are running stock pads and fluid, you'll be overheating the pads and boiling the fluid.

flink said I don't think it's sucky at all - it's really a very good ABS on my C6's. The DRP (Dynamic Rear Proportioning) works very well.

The 2009 and newer have a Bosch ABS. Prior to that the C6 had a Delphi system.

Bob

sperkins

If I don't hit the ABS in every corner on a flyer lap, I've done something wrong.

brkntrxn

In the ways of internet geekery,


+100


What Scott said. If I am not hitting ABS, I am not on the podium.



-Kevin

rustyguns

i had an" ice mode problem" by having brakes the bite too fast and scrubs that were not sticky enough, fricken scary. fixed that problem with different pads

otherwise i absolutely luv late braking with ABS.

Dirty Howie

Thanks all for your inputs.

I'm much happier not worrying about fade with weak pads than too much ABS. I didn't have any issues at AutoClub Speedway and that has some high speed 130 MPH straights down to 90* turns in 2nd gear. Maybe I just have really good brake modulation skills.

I will be at a different track (Buttonwillow Raceway) next week weekend. I will get back here with a report on how it went.


DH

Timz06

I have tried to run without ABS, good practice but lot's of flat spotted tires.

I think the problem without ABS is the F/R bias. With the stock system, the rears will lock up too early. Best to leave it alone. It stops fine with the ABS.

vette6aut0x

The c5/c6 corvettes have electric brake proportioning. Not a good idea to eliminate the abs. I have heard the story many times that you can brake better with out but I say bs. A good abs system is the way to go. It will save tires and make you go faster. I have looked at the data with and with out and I am faster with it. Now with that said our race car is a 07 z06. We are using a GM computer that did not come with the car. It is made for people who just need a computer for engine management. We us a c5 abs unit that is basically a stand alone unit. We got it to operate the abs only and it works like a dream.