Issues with tire ratios
Thread Starter
Intermediate
Joined: Aug 2017
Posts: 30
Likes: 7
Issues with tire ratios
Hi. I'm new to the forum. I just picked up my new DD and did the work necessary to get it running on all cylinders, slapped some new tires on and drove it across the country. Anyways, I replaced the rears with 275/40r17's and now when I punch it at high speeds the ASR kicks in and I have to frantically look for the ******* button while I'm in the oncoming lane. I hypothesize that this is a result of the smaller diameter and the ASR recognizes the increased speed as slip. I read this can be adjusted somehow for the new tires but I have absolutely no idea where or how it can be done. Does anyone have any ideas? This car will be seeing snow and ice and I'd like to keep the system running.
Last edited by WindHam; Aug 24, 2017 at 08:52 PM.
Le Mans Master
Joined: Feb 2000
Posts: 9,061
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From: Epping NH
I've never heard ASR being affected by tires size before and haven't heard of changes that can be made because of tire size. Sounds more like a bad speed sensor, check for codes...although technically the "Service ASR" light would be on.
Melting Slicks
Joined: Oct 2016
Posts: 2,024
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From: Central Alabama
What light is coming on?
It sounds like your ASR Engaged light since your reaching for the ASR off button.
Could it be your actually loosing grip? Which means the system is working as advertised.
It sounds like your ASR Engaged light since your reaching for the ASR off button.
Could it be your actually loosing grip? Which means the system is working as advertised.
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At high speeds? what speed, any issues from a stop when you go WOT? Does ASR work than?
Never heard of ASR creating an out of control issue.
Never heard of ASR creating an out of control issue.
Last edited by FASTAZU; Aug 25, 2017 at 10:39 AM.
Thread Starter
Intermediate
Joined: Aug 2017
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Do'h. Sorry I forgot to include that information. It's a 93 with an auto. The ASR works fine at low speeds but at around 50 mph it starts acting up. It doesn't mess with the brakes but it does retard and kick back the pedal. All I know is that it never did it before I replaced the tires and someone on reddit told me that "it should be programmable by someone who knows their way around 80's tech". Tires definitely aren't spinning haha.
Team Owner
Joined: Dec 1999
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From: Lacey WA RVN 68-69
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93-96 C4's could have either the 285/40 or 275/40 tires on the rear based on what suspension the car had. The difference in tire diameter mounted on 17x9.5" wheels should only be around 3/10" and that should not cause any issues with ASR.
When you feel the ASR kick in, just what are you doing? What speed are you traveling? Is this happening on a curve? If t he car has an auto trans, is a downshift to 1st and the engine going to a high RPM? The LT1 engine has enough power to get the car out of shape at lower speeds and if the rear wheels break loose under hard acceleration, the ASR is designed to help control the car.
Do you feel a shaking of the gas pedal when this happens? One thing that ASR does is to reduce the opening of the TB butterflies. That would be the shaking feeling. ASR will also retard timing and even apply the rear brakes to help gain control.
When you feel the ASR kick in, just what are you doing? What speed are you traveling? Is this happening on a curve? If t he car has an auto trans, is a downshift to 1st and the engine going to a high RPM? The LT1 engine has enough power to get the car out of shape at lower speeds and if the rear wheels break loose under hard acceleration, the ASR is designed to help control the car.
Do you feel a shaking of the gas pedal when this happens? One thing that ASR does is to reduce the opening of the TB butterflies. That would be the shaking feeling. ASR will also retard timing and even apply the rear brakes to help gain control.
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93-96 C4's could have either the 285/40 or 275/40 tires on the rear based on what suspension the car had. The difference in tire diameter mounted on 17x9.5" wheels should only be around 3/10" and that should not cause any issues with ASR.
When you feel the ASR kick in, just what are you doing? What speed are you traveling? Is this happening on a curve? If t he car has an auto trans, is a downshift to 1st and the engine going to a high RPM? The LT1 engine has enough power to get the car out of shape at lower speeds and if the rear wheels break loose under hard acceleration, the ASR is designed to help control the car.
Do you feel a shaking of the gas pedal when this happens? One thing that ASR does is to reduce the opening of the TB butterflies. That would be the shaking feeling. ASR will also retard timing and even apply the rear brakes to help gain control.
When you feel the ASR kick in, just what are you doing? What speed are you traveling? Is this happening on a curve? If t he car has an auto trans, is a downshift to 1st and the engine going to a high RPM? The LT1 engine has enough power to get the car out of shape at lower speeds and if the rear wheels break loose under hard acceleration, the ASR is designed to help control the car.
Do you feel a shaking of the gas pedal when this happens? One thing that ASR does is to reduce the opening of the TB butterflies. That would be the shaking feeling. ASR will also retard timing and even apply the rear brakes to help gain control.
Le Mans Master
Joined: Jun 2009
Posts: 6,528
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From: South Dakota
The 285/40/17 and 255/45/147 tires are 26.0" and the 275/40/17 tires are 25.7". The wheel sensors will see the difference front to back, but I have never heard of this small amount causing the ASR problems.
I have run 255/45/17 tires with 275/40/17 rears on several C4's and never had a problem with the ASR
(unless I used too much throttle for the tires and broke them loose
)
I suppose it is possible for yours to be sensitive to this, but I think it unlikely.
I am a novice at looking at the vehicle programming, but I do not see anything that adjusts the front to rear difference in the .bin file to set off traction control at different points. (I looked at a '94) But like I said, I am a novice and could have missed something.
Good luck.
I have run 255/45/17 tires with 275/40/17 rears on several C4's and never had a problem with the ASR
(unless I used too much throttle for the tires and broke them loose
)I suppose it is possible for yours to be sensitive to this, but I think it unlikely.
I am a novice at looking at the vehicle programming, but I do not see anything that adjusts the front to rear difference in the .bin file to set off traction control at different points. (I looked at a '94) But like I said, I am a novice and could have missed something.
Good luck.
Last edited by QCVette; Aug 25, 2017 at 01:58 PM.