: Whats the formula for resivin the tire size and not losin cruise control



Naf
01-16-11, 02:46 AM
Ok, i have an EFI and i did the whole tire size change but i lost cruise control.

Speedo was spot on, but no cruise, i returned it back to stock and the cruise works once again...

Who here knows the formula for pluggin in the right number to get the speedo to work correctly and still maintain cruise control options...?

Twitch
01-16-11, 03:59 AM
I've changed the speedo a few times but never lost cruise.
1. Are front/rear tires the same size?
2. There is a minimum speed to engage cruise control. I think it's 25mph.

Naf
01-16-11, 04:46 AM
The front will be 285/35R18 and the rear 305/35R19...

I know of the min speed for the cruise to work, i am at about 70mph and it just wont hold...When i put the original numbers in it all works, but when i have it as per EFILIVE no work...

its weird...

AAIIIC
01-16-11, 10:27 AM
Can't help you on cruise control, but I'd bet your ABS and traction control are going to be a problem with those rather unusual tire sizes. Those fronts and rears are 6% different - that's no good.

crankedupforit
01-16-11, 11:16 AM
Can't help you on cruise control, but I'd bet your ABS and traction control are going to be a problem with those rather unusual tire sizes. Those fronts and rears are 6% different - that's no good.

:yeah::yeah::yeah:
http://www.cadillacforums.com/forums/images/smilies/yeahthat.gif

ctsv154
01-16-11, 11:17 AM
Just find a tire that will keep the difference under like 3%. Its been a while, I think thats the magic number to make everything work right.

Stepside
01-16-11, 02:02 PM
Yup, I have read that, also. ~ 3% ~ is the max.

Naf
01-17-11, 01:36 AM
I was runnin 275/35R18 and 255/40R18 no issues with abs nor traction control...I have also had 275/40R18 and 255/40R18 and still no issues....

I dont see an issue with the other functions, just an annoyance from the PCM for the cruise control...

AAIIIC
01-17-11, 11:36 AM
I was runnin 275/35R18 and 255/40R18 no issues with abs nor traction control...I have also had 275/40R18 and 255/40R18 and still no issues....
And your point is... ?? Those setups are ~1.7% and ~2.4% different, so there shouldn't be any problems with those combinations.


I dont see an issue with the other functions, just an annoyance from the PCM for the cruise control...
Let me clarify my original reply to this thread. My impression is that the cruise control issues are happening with your street tires, which presumably are some normal size. I don't think the cruise control issue has anything to do with tire size at all - I think it's a problem with whatever ECU flash program you're using. I'm assuming you haven't run the race tires yet, since you said they "will be 285/35R18 and the rear 305/35R19" - "will be" implies to me that they're not on the car yet. Hence my original reply was intended to be a warning - rethink your tire sizes or you can expect to have issues.

If you actually are running those sizes already and not seeing ABS or TCS issues then I'm guessing you haven't really pushed the car yet. Or, you just typed in the wrong numbers and you're not really running 19" rear wheels and 18" front wheels, in which case your 285/35-18 and 305/35-18 tires are only 2.1% different and should work fine.

Naf
01-18-11, 03:13 AM
And your point is... ?? Those setups are ~1.7% and ~2.4% different, so there shouldn't be any problems with those combinations.


Let me clarify my original reply to this thread. My impression is that the cruise control issues are happening with your street tires, which presumably are some normal size. I don't think the cruise control issue has anything to do with tire size at all - I think it's a problem with whatever ECU flash program you're using. I'm assuming you haven't run the race tires yet, since you said they "will be 285/35R18 and the rear 305/35R19" - "will be" implies to me that they're not on the car yet. Hence my original reply was intended to be a warning - rethink your tire sizes or you can expect to have issues.

If you actually are running those sizes already and not seeing ABS or TCS issues then I'm guessing you haven't really pushed the car yet. Or, you just typed in the wrong numbers and you're not really running 19" rear wheels and 18" front wheels, in which case your 285/35-18 and 305/35-18 tires are only 2.1% different and should work fine.

You are right, i have the tires sittin in my garage collecting dust till the wheels get here...

As for pushin my car, lets not get into that...Too many factors involved...

Now if i will look into the ecu flashin, will get my friends HP tuner and try flashin with that instead of my EFILIVE