Speed Sensor Bases Limp mode after new tires

[MrSlay]

Installed the rear tires on my wheels today (285/40/18) and the car soon went into a Speed Sensor based limp mode. Abs, Hand Brake, Power steering, and a few more lights Christmas treed the dash while vehicle speed read 0 as the car was doing about 60mph.

My friend also had the same issue with his initial set of tires as they was about a 9% difference in diameters between the front and rear tires. He fixed the issue with a new set of tires that are now have about a 2% difference in diameter.

Question here is if anyone knows the minimum ratio/percentages that will satisfy the electronics on the car. I have a set of tires set to come in on Monday that are 7.2% smaller than my rear tires and really don't want to mount them if there not going to work.

Thanks In Advance

[JerryMichaels7]

holyshit you fit 285s???

[MrSlay]

Originally Posted by JerryMichaels7

holyshit you fit 285s???

Ya, thankfully my measurements were right and they were no problem. I could even run a 305 If I were to roll the fenders.

[no chrome]

Originally Posted by MrSlay

Installed the rear tires on my wheels today (285/40/18) and the car soon went into a Speed Sensor based limp mode. Abs, Hand Brake, Power steering, and a few more lights Christmas treed the dash while vehicle speed read 0 as the car was doing about 60mph.

My friend also had the same issue with his initial set of tires as they was about a 9% difference in diameters between the front and rear tires. He fixed the issue with a new set of tires that are now have about a 2% difference in diameter.

Question here is if anyone knows the minimum ratio/percentages that will satisfy the electronics on the car. I have a set of tires set to come in on Monday that are 7.2% smaller than my rear tires and really don't want to mount them if there not going to work.

Thanks In Advance

did you try it with 7.2% difference?
did that trigger limp mode?

i'm considering a 5% diameter difference front to rear
anyone running that right now?

if we all hit limp mode, maybe custom tone rings would work?

[Dwood11]

Originally Posted by JerryMichaels7

holyshit you fit 285s???

Um I second that. Impressive, most impressive. I am thinking of going 235 or 245. Now those sizes just seem puny. Props man. How much do those bad boys weigh, wheel and tire together. You gotta be feeling some power loss there. How does the car feel in terms of that? I am really curious.

[SkAsphalt]

Originally Posted by Dwood11

Um I second that. Impressive, most impressive. I am thinking of going 235 or 245. Now those sizes just seem puny. Props man. How much do those bad boys weigh, wheel and tire together. You gotta be feeling some power loss there. How does the car feel in terms of that? I am really curious.

Power loss? oh yeah, he neutered it.
lol @wparsons made a good point. If he has that much power, he needs that girth

[wparsons]

^^ If his signature is even remotely accurate, he'll need 285's or bigger

[SkAsphalt]

Originally Posted by wparsons

^^ If his signature is even remotely accurate, he'll need 285's or bigger

haha waaaaaaaait TOUCHE.

[AtlasMick]

What can you do to correct the limp mode? The computer runs it, if you can tune the ECU for emmissions and timing couldn't you also tune it to fix speedo and traction control issues associated with larger diameter wheels/tires?

[Crazy Drew]

Originally Posted by AtlasMick

What can you do to correct the limp mode? The computer runs it, if you can tune the ECU for emmissions and timing couldn't you also tune it to fix speedo and traction control issues associated with larger diameter wheels/tires?

+1 was this ever resolved without changing tire size?

I'd like to run 18/19 stagger and I can't really do this without concerns about what you had going on.

[diss7]

I've run 225/40/18 and 205/40/17 and that causes it.

Also 205/55/16 and 205/40/17 caused it as well.

205/40/17 and 205/50/16 DOESNT do it. Neither does 205/40/17 and 205/45/16

Not running the abs fuse doesn't solve it. It obviously solves the abs from panicking when you brake with such a stagger (because pulling the fuse disables the pump) but it'll still set rev limit at 4200 or so, and do weird things with the ps (provides weird levels of assistance at different speeds.

[adjusts]

Originally Posted by no chrome

did you try it with 7.2% difference?
did that trigger limp mode?

i'm considering a 5% diameter difference front to rear
anyone running that right now?

if we all hit limp mode, maybe custom tone rings would work?

did this ever get resolved? do you know the maximum difference that is acceptable?

[adjusts]

Originally Posted by no chrome

did you try it with 7.2% difference?
did that trigger limp mode?

i'm considering a 5% diameter difference front to rear
anyone running that right now?

if we all hit limp mode, maybe custom tone rings would work?

did you have issues with 5% diameter? I'm interested in how this turned out.