I changed all 4 tyres the other day, and noticed the car's SLIP indicator is appearing a lot now. Even when im turning a normal turn in 5th gear...would doing a wheel alignment help?

Thanks.

 

what size of new tires

 

+1. Sounds like the diameters are not matching the old ones. This will cause a problem with the TCS.

 

New tires? New tires are slippery. Give them 100 miles.

 

hey guys...thanks for the input...

my rears are 265/35zr18 and the front are 235/40zr18....ive already done more than 100miles on them...but still slipping. But you are right, the rears are slightly larger than the originals....will this really stuff the TCS up?

 

Your rears are way too small. They should be /40 profile

Yes, having incorrect tire sizes messes up the TCS/VDC system.

Sorry if I sound like a jerk here, but if you had searched and done your research before buying, you wouldn't be stuck with this problem.

 

And just to shed light on why tire size affects VDC/TCS; the ECU is preprogrammed to accept a certain front/rear tire ratio. As long you stay within that ratio, there are no issues. But if you are veer too far out, the ECU would think rear tires are moving faster than the front (just as do in a burnout or while sliding in rain/snow) so to fix it, ECU cuts power/applies breaks to the rears (even if too lightly to notice) and the slip light comes on.

My rears are 285-width compared to OEM 265 and fronts are 255 compared to 245 OEM, on OEM GT wheels, but I did my homework and came up with a size combo that was off by only 0.01% in front/rear diameter ratio, hence my ECU was never confused.

 

The front tires are taller than the rear. I assume that you have VDC, and this set-up is not acceptable.

 

Thanks for the input guys...

Ive called the tyre guys and are willing to change the rears to 245/45zr18. only the back needs changing right? 245/45zr18 is what states in the glove compartment

thanks again!

and sorry for being a novice...i love my car, but dont know much about it :P

 

What wheels do you have?

6 spoke touring trim 18" wheels?

or the 2006 model 18" wheels?

 

6 spoke touring trim 18" wheels

 

I installed BF goodrich G'forces of the same size (225/45 front and 245/45 rear on 18" stock wheels) about 3 months ago. About 2 months later I had one instance where the vdc off, slip, and brake light all went on (Randomly) until I shut the car off and restarted it. The problem didnt show up again until 4 days ago, and has been coming up much more often (about 60% of the time the car is on) My driving has been very conservative since I noticed the problem. Does anyone have an answer for that?

 

All three lights illuminated can indicate either a problem with the system or something as simple as low brake pads/low fluid. Check the fluid and pads first.

 

The TCS kicks in when the rear tires are spinning at detectably different speeds. Not front to back relative velocities-tire sizes do not matter to the TCS. Try this- go onto a cloverleaf on the curved part of the ramp. Drive at a steady 40 MPH, the TCS will be not activate. Do the same thing at a steady 55, then at a steady 65-70 (Safe speed). At the higher speed, the TCS will probably kick in and the engine will cut out and stumble.) The ECU has detected the inside rear tire spinning at a markedly different rate from the outside rear tire, and decided you were slipping. Turn off the TCS control and you can go around the curve at a high speed without the stumble. (Don't do something stupid and wreck the car!!!). Depending on the curve and banking you will not get any slip unless you floor the gas (even then on concrete it is very hard to spin with sticky tires). I have big G-Force on the back (275/35-19) and the small Bridgestones on the front (225/50-17, the last of the free replacements for the feathering problem...). They are 3/4" different in diameter, and there is no problem with the TCS activating under any condition other than taking curves at very high speeds. This dimension is twice the stock tire setup. The "slip" is not really slip, only differential rotation velocity.

 

Actually, it's the total opposite of what you describe. From the FSM:
TCS detects unexpected velocity differences between the front and rear wheels. If the rears are rotating at a rate that does not match the expected value based on the front wheel rotation, that causes TCS to activate. The most common cause of "false positives" is tires sizes that don't have the correct stagger.

Your first statement is correct ("The TCS kicks in when the rear tires are spinning at detectably different speeds.") in that the detectable different speed IS relative to the front wheels.


Believe it or not, the stagger of those sizes is the same as the stock setup (0.7"). That's why TCS doesn't kick in while driving around normally. If it's kicking in while turning, it probably because you're getting some slippage. It's not uncommon for a car with different front/rear tires (new vs old, different brands, etc.) to experience the Slip indicators. Worn tires are a different diameter and can result in the stagger being off more than tolerable. New tires can be slick and actually slip until the "break in". Check out this thread as a perfect example of that phenomenon (especially his last post today)...
https://my350z.com/forum/wheels-and-tires/277357-new-rear-tires-correct-size-cause-vdc-to-activate-on-highway-on-ramps.html

 

Believe it or not, the stagger of those sizes is the same as the stock setup (0.7"). That's why TCS doesn't kick in while driving around normally. If it's kicking in while turning, it probably because you're getting some slippage. It's not uncommon for a car with different front/rear tires (new vs old, different brands, etc.) to experience the Slip indicators. Worn tires are a different diameter and can result in the stagger being off more than tolerable. New tires can be slick and actually slip until the "break in". Check out this thread as a perfect example of that phenomenon (especially his last post today)...
https://my350z.com/forum/showthread.php?t=277357[/QUOTE]

I read your post, thanks for the corrections.
Only minor point is that the original stagger is 0.39 inches, not 0.7.