Hi, i just replace the Rear tires to Dunlop Direzza DZ101 245/45r/18. For some reason, when i driving on freeway around 60 + miles. The car going unsteadily, sometimes slide to right, sometimes to the left. Once in awhile the car also skid and the SLIP device was on then the car just kinda lagging and almost lose control on the freeway. I told the shop about this and the guy guessing that because the front tires is old and the rear tires is new, that's why there will be a different between the speed timing and the traction control will automaticly detected and that's why VDC turns on and also affect the ABS system....... Is that true? cause he asked me to get the new front tires too but mine still have like 50% left on the front......

 

I don't buy his explanation. If you're just driving down the freeway (straight line, constant speed, don't nothing unusual) and the Slip indicator comes on, that is usually caused by an improper stagger - that is, the ratio of tire heights from front to rear is not correct. Are your front tires the original OEM ones (225/45/18)? Did you check the new rears and make sure they installed the proper size (245/45/18)?

Sometimes when somebody replaces the front or rear tires and not the other set, they will have problems when accelerating and/or turning and the Slip indicator will kick in. That is caused by the new tires being a little slippier than the old ones. Once they get scuffed up, the problem goes away.

 

I have Direzzas, and haven't any problems with them. I replaced all four tires though. I think they are great tires for the money. I don't know what would be causing the VDC problem in straight cruise mode.

 

Actually is when I turn slightly right or left or change lane on the freeway, then the VDC will kick in, but when i go straight 70 and up then the car starting to slide to left or right just like alignment problem but that is not alignment for sure, cause i never have that problem before i replace the tires. damn, i really don't want to change the front tires too, still can last at least 6 months, or other advice? and THANKS for all the replied

 

Shouldn't have anything to do with new rear tires unless you have unusual tire wear from bad alignment, shocks, tire balancing ect. I would get them balanced and get an alignment. Not sure if the Direzzas are directional, buy check to see if they were installed correctly. Sounds stupid, I know but it happens.

The VDC is touchy and sometimes goes off with the incorrect stagger, but I never heard of it being fooled by the very, very slight difference of diameter because of tire wear. I had to replace only the right rear temporarily (ran over a nail and went through the side wall and didn't have the cash for both) and never had a VDC problem.

 

If you find the car wanting to drift left or right on the road, it could be caused by the different tread pattern of the new tires. Some tires are more suseptable to "tramlining" (http://www.tirerack.com/tires/tirete....jsp?techid=47) than others. Even if that was the case, that wouldn't trigger VDC/TCS.

Simple lane changes at speed should not be triggering VDC/TCS unless something else is wrong. People who don't have the normal stagger in their tires will usually see VDC/TCS kick in on sharp turns at moderate speeds.

Again I would suggest checking the tire sizes of the old and new tires. It wouldn't be the first time that a shop put the wrong size tires on somebody's Z and they started having weird problems. As 2LowZ pointed out, check for Rotation indicators to make sure they're installed on the right sides.

 

What size are the front tires?
What size are the rear?
Check to make sure that the installer put the correct tires on the correct wheels, and the correct wheels on the correct axle(sounds stupid but believe me it happens).

 

I didn't even think to recommend what David said. They are directional tires like most of the other performance tires. If the installer mounted them wrong, and the tread pattern is backward then you may have traction and ride issues. Mine are pretty quiet and grip really well. Sometimes I get the VDC to light off during really hard acceleration but that is normal compared to my OEM tires but the car tracks straight.