carnutz

I am wondering how much differance the ABS will allow between the front and rear before it throws a code. Can it be done with tire size or is it more tollerant of change? There has to be an accepable range of pulses from the front Vs the rear. I cant seem to find any specs or info on what is the acceptable range.

Z95m6

The ABS setup notices with the reluctor ring isn't spinning so tire size shouldn't effect it. Just as changing gears in the rear which speeds up or slows down the reluctor ring speed doesn't effect the ABS.

Mikey97Z

Yes when I put my slicks on the ABS always complains. They're 26" ET Streets, but they're a little taller than stock.

Z95m6

Mikey your problem must be somewhere else. If not everyone that put in diff gears would have ABS problems because the reluctor ring would change speeds.

Injuneer

Actually, the speed at which the axle (and hence the reluctor gear on the carrier) rotates is dependant on the tire diameter... not the rear axle ratio. Changing gears does not change the rate of the reluctor gear rotation for a given speed. It just changes the number of driveshaft turns and engine RPM for a given speed.

I would suspect the ABS is activated when the sensor detects that the reluctor is nearing "0" rotational velocity. I run 28" slicks, 26" fronts, and never had a code from the ABS.

Now that I've thrown in my .02, I'll move it to "Suspension, Brakes...." where it belongs.

carnutz

Sorry, the reluctor is mountd on the carrier so it doesnt care about driveshaft speed (IE differnt gears) it spins the same speed as the tires so when it see's a differnce in the pulses vs the front is when it has a problem.
I am wondering how touchy it is, evedentally it has to be pretty close to the fronts.
To let the cat out of the bag I am trying to come up with a ABS system that mounts to the pinion. the stock reluctor has 106 teeth, So to get the same number of pulses per tire revolution I am trying to size my reluctor correctly. For example a rear with 4.11's in it I need a 26 tooth reluctor. (26 teeth X 4.11 revolutions of the drive shaft to = one tire rev. 26x4.11=106.86) I am wondering if the ECM would tollerate a lets say 25 tooth reluctor, now 4.11x25 teeth is 102.75 Is that out of range for the ECM?

carnutz

Darn it you beat me to it!
I'm sorry if i placed it incorrectly but didnt think it would get the technical support I am looking for.

Z95m6

Yes i know where the reluctor ring is at. I did what you are trying to do along time ago. Do a search in the drive train forum. I built an ABS setup for my 8.8 1.5 yrs ago.

Mikey97Z

It's pretty sensitive. When I calmly come to a stop it notices that the revolutions of the back wheels is not keeping up with the front. The tire's only about 1 taller.

I just measured the circumfrence of the front tires at 80" and the back at 84". I think it's the LOW TRAC light that comes on. So i guess it starts pumping the back brakes because it thinks they're locking up.

96ltz

Do you get the "low trac" light alot or no more than when you run equal size tires?

94formulabz

3 Channel - Sensor on each front wheel and 1 for the rear. The reluctor ring attaches to the ring gear and indicates the condition of both rear wheels. 3 Ch -> no traction control

4 channel - sensor on all 4 wheels, traction control and that extra dash light.

Freds car is a 94, no trac control/no light, the original post also specified 3 channel.



-brent

96ltz

I've got the 3 channel (no traction control) and get a low trac light when the abs kicks in. This is on a '96 though. Just wondering if he was talking about a error code or if the abs engages when it normally wouldn't with the same size tires all of the way around. Thanks.

Injuneer

I didn't get the "LOW TRAC" light or the "ABS INOP" light at all when running the larger rear tires. I do get a "BRAKE" light when the line lock is activated, but that is understandable, based on the difference in line pressure between the front and rear brakes.

All that was based on running a Strange 12-bolt, with their weirdo sensor on top of the housing. It was extremely hard to keep it adjusted properly, and when it wasn't adjusted correctly, it would appear to "lose" the sensor output just as the car came to a stop, and the ABS would activate and take a few feet extra to stop the car.

Since its only a "track" car now, the ABS is not going to be there very long. The Strange sensor also seems to have a life span of only 2 years or so, and its not working any more. I'll pull the carrier with the reluctor gear, sell it to someone who wants to keep their ABS, and install a spool.

carnutz

Mine is a 94, and when the ABS works (IE wet etc) the "low trac" light lights for a few seconds, I think just to let you know that the ABS ECM sensed a loss of traction IE wheel lock up....
I am thinking the lets say 25 tooth reluctor with a 4.11 gear isnt going to work as I gather the ECM has a tighter window of operation.

Z95m6 I have done a couple of serches and came up with bumpkis, nada..... Care to share your set up?

Z95m6

http://web.camaross.com/forums/showthread.php?t=169674

For some reason everyone tries to keep 3channel ABS setup's a secret.
I've run much bigger wheels in the rear and i never had ABS problems. I've also had no ABS problems with this setup.