Traction Control Problem

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Mar 9, 2006 | 12:35 AM

kman0066

Thread Starter

Burning Brakes

Joined: May 2000

Posts: 1,160

Likes: 10

From: Nashville TN

Traction Control Problem

I'm having a problem with the traction control on my 98 vert 6spd. I just put some new Sumitomo tires on the rear which surprisingly stick very well. Sometimes though when the traction control activates now, it will not deactivate or I have to release the pedal and then it will deactivate. Once I had to shut the car off so that I could start accelerating again. What should I look for? The tires being mounted could just be coincidence but I thought I'd mention it because it happened shortly after. I even tried going with it for awhile and for about 25 seconds, I was stuck at the same speed after the traction control had activated(Traction Control warning message stayed on) until I released the pedal.

Mar 9, 2006 | 01:17 AM

Bill Dearborn

Tech Contributor

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From: Charlotte, NC (formerly Endicott, NY)

Quote:

Originally Posted by kman0066

Sounds like your rear tires are too small in diameter. If the rear tires are smaller in diameter than the front tires the TC will activate (brakes) even though you are coasting down hill in nuetral. If you are trying to drive you will get rear brake activation and throttle cutoff.

Bill

Mar 10, 2006 | 12:14 AM

kman0066

Thread Starter

Burning Brakes

Joined: May 2000

Posts: 1,160

Likes: 10

From: Nashville TN

O yeah, they're probably different size now, put on 285's instead of 275's, same series though. Anything I can do to remedy this or I just have to deal with it?

Mar 10, 2006 | 12:46 AM

Bill Dearborn

Tech Contributor

Joined: Oct 1999

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From: Charlotte, NC (formerly Endicott, NY)

Quote:

Originally Posted by kman0066

O yeah, they're probably different size now, put on 285's instead of 275's, same series though. Anything I can do to remedy this or I just have to deal with it?

Check the profile on the rear tire. Based on the Tire Rack Web Site you can only get the 285/18 Sumitomo in a 30 or 35 profile. Not sure what you have on the front but if your rear profile is a 30 then that is probably your problem. The ways to solve that problem are to get larger profile rear tires, swap the front and rear wheels or turn off TC everytime you drive the car. If the profile is 35 then the rear tires are large enough depending on what you have on the front. The system can handle equal diameter tires front and rear but as soon as the rear diameter is less than the front you have problems.

Bill

Last edited by Bill Dearborn; Mar 10, 2006 at 12:55 AM.

Mar 10, 2006 | 03:08 AM

kman0066

Thread Starter

Burning Brakes

Joined: May 2000

Posts: 1,160

Likes: 10

From: Nashville TN

OMG wow, yeah I have the 35 series on there, just realized that compared to the stock 40 series. It really only happens when I loose traction and then the problem starts, so I'll just deal with it for daily driving and turn it off when I want to have fun.

Thanks for the help...I feel like an idiot now...well at least the wider tires are sticking like glue

Mar 10, 2006 | 11:30 AM

Bill Dearborn

Tech Contributor

Joined: Oct 1999

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From: Charlotte, NC (formerly Endicott, NY)

You still may want to analyze the problem a little more. If you have 275/40/17s on the front and the 285/35/18 on the rear the rear tires are about .2 in larger in diameter which means you should have no problem. Even with equal diameter tires front and rear my TC does not stay on if I forget to turn it off when I autocross. At the start the rear tires will spin a little then TC applies the brakes, cuts the throttle and the car bogs coming off the starting line. However, TC will deactivate within a couple of seconds once the rear tires are under control. If you are getting longer periods where the TC remains activated after initial slippage of the tires there could be some other problem.

Bill

Mar 10, 2006 | 11:41 AM

ThePizzaC5

Instructor

Joined: Jul 2005

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From: Cussing at my car somewhere

I'm assuming this is a problem that can be fixed using something like HPtuners?

I've got a set of BFG 315 30s in the garage waiting to go on the back - and I'm hoping I'll be able to program the change within the PCM... yes? My copy of HPtuners isn't here yet, but is due any day now.

Mar 10, 2006 | 12:01 PM

Bill Dearborn

Tech Contributor

Joined: Oct 1999

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From: Charlotte, NC (formerly Endicott, NY)

Quote:

Originally Posted by ThePizzaC5

I don't think so. The PCM only reacts to requests made by the EBTCM. The Corvette TC is not just a throttle application like a lot of cars on the market or an ignition control application like some NASCAR teams are accused of using. The Corvette TC is a combination of brake and engine controls. Under certain conditions the only TC action will be a short rear brake application to the slipping wheel to get it back under control. The EBTCM decides whether to activate engine controls after it first applies the rear brakes. GM has the ability to reprogram the EBTCM but nobody outside of GM engineering has the ability. Since it requires a highly trained engineering team and a lot of track testing to determine changes to TC parameters that is not something that is available to the backyard mechanic or tuner shops. If done incorrectly it could be highly dangerous.

Bill

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Mar 13, 2006 | 02:44 PM

kman0066

Thread Starter

Burning Brakes

Joined: May 2000

Posts: 1,160

Likes: 10

From: Nashville TN

OK got some updates. Got to the interstate and the traction control seems to randomly kick on at higher speeds, circa >65mph. I also found the tire diameters for the tires I have on there
Fronts = 25.68"
Rears = 25.85"

So they're pretty close to the rears but I guess the stock rears are 26.66", so I think that this is the problem, considering it gets worse the faster I go.

Mar 13, 2006 | 09:02 PM

#10

shurite44

Le Mans Master

Joined: Sep 2004

Posts: 7,027

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From: Shiloh Ohio

Quote:

Originally Posted by kman0066

It could be the problem but I would not be absolutely sure about it. Quite a few guys run same size tires all around and do not have traction control problems. But then again I have read of people having the TC screw up in situations like yours also.

Any chance of someone in your area letting you put on some taller rears and see if it fixes the problem?
Good luck.

Mar 14, 2006 | 12:07 AM

#11

Bill Dearborn

Tech Contributor

Joined: Oct 1999

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From: Charlotte, NC (formerly Endicott, NY)

Reprogramming the PCM will not do it. TC is handled in the EBTCM. The EBTCM uses the wheel speed sensors to determine if the wheels are slipping. If the wheels are slipping then it applies the rear brakes and if necessary it requests reduced torque from the PCM.
Bill