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md
Dodge Dakota
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9/24/2003
09:23:00
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 Subject: Tire Diameter/ABS Question
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Does anyone know how much taller you can go with new tires before it affects the ABS system. I'm planning on going 1.6" taller than stock on my 2000, 4.7. I will have the computer calibrated as close as I can to the size I intend to instal - in effect, leaving me within .7" of the new diameter. (Going from 255/65/15 (28") to 265/70/15 (29.6") and calibrating for a 235/75/15 (28.9").
Any thoughts?
Thanks,
MD
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Perpetrate
GenIII
9/24/2003
13:43:58
| RE: Tire Diameter/ABS Question
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The CAB (Controller ABS) does not talk to the trucks computer and has its own tire size and gear ratio programmed into it. Changing tire size trough a scanner will only affect the speedometer. I have seem a pattern of ABS lights coming on after larger tires are installed. I have been talking to Chris (forexfour) about this because he has a shop manual for his truck. He might know something else that I don't know.
Craig
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forexfour
GenIII
9/24/2003
16:04:53
| RE: Tire Diameter/ABS Question
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I do not think tire size has anything to do with the ABS / brake light problems. Nor do I think tire size effects the ABS system. As stated in the book the ABS controller and the PCM do not communicate or share tire size info. They are independant of each other. We read that in you living room.
Also I ran 33's for over a year before this abs/ brake light problem came up.
Perpetrate had a different problem but he still has the lights come on. It was trouble shot to be the CAB (Controller Antilock brakes).
But the question of programming the tire size into the CAB is still unanswered. I will have my mechanic trouble shoot this one of these days. With the 2 big weekends trips back to back I am sure I will have some thing go hay wire, I am due!!!
Never late for a Tee time or wheelin with my buddies! Always ready for both!!!Forexfour's home
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md
Dodge Dakota
JOIN HERE
9/24/2003
18:32:24
| RE: Tire Diameter/ABS Question
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Message:
Thanks guys for the response. The reason I brought up the issue is this: I'm not worried so much about the ABS light comming on (unless it means the ABS is not working). I have been told by a service mgr that tire size can, and often does, screw up the ABS. I realize a service mgr is not the final authority, but I'm having trouble factually refuting his statement. I'm not sure that installing larger tires - if it did void the ABS system - would necesarilly prompt the ABS light to come on or go off, as the case may be. The light, it seems to me, could simply be an indicator that the sensor is malfunctioning. I think??
Now that I think about this seemingly never ending conundrum, I'm starting not give much of a sh*t whether the ABS works or not. The stock tires are a joke and having ABS brakes on only the light end of the truck - the back wheels - is next to useless. LMAO
Thanks again,
MD
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Mike Robb
Dodge Dakota
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9/25/2003
01:07:25
| RE: Tire Diameter/ABS Question
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ABS is actually a fairly simple system. There is a pick-up at each wheel which senses rotation. When the brakes are applied, the ABS brain begins to back off brake pressure (the pulsing you feel when braking hard) to keep the wheel from locking up and skidding. It doesn't know or care what size your tires are. All it knows is whether ir not the wheel is spinning. An ABS light is an indicator of a fault in the system and is more than likely due to a bad wheel sensor.
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forexfour
GenIII
9/25/2003
09:27:27
| RE: Tire Diameter/ABS Question
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Sensors are usually the fix but we have done that on both our trucks.
Tire size is not an issue for the ABS system as far as I see it but the CAB is programmed independently with tire size info and you are supposed to be able to re-program for a larger tire but I do not have the book with those proceedures. I am gonna have my mechanic see what he can do for me. He diagnosed Craigs ABS problem down to a specific relay within the CAB.
Never late for a Tee time or wheelin with my buddies! Always ready for both!!!Forexfour's home
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