I recently got replacement rear tires on my 2005 touring, same size as stock 245/45-18 (fronts are stock 225/45-18). Even though the fronts are almost worn out, I didn't replace them for a variety of reasons. However, since replacing the rears, VDC rather consistantly goes off when on freeway on ramps - almost making me lose control as it applies the brake to what feels like one of the front wheels! I have a hunch that the wear on the front tires causes them to violate the VDC front vs. rear spec. By my math, a 10/32" wear (reasonable according to the tire store) on the front tires translates to a -2.4% difference in circumference. Maybe the difference in rotational speed during a turn is then enough to set it off? Has anyone else experienced this? I'd like a little confirmation before I order new tires for the front, only to find out that it didn't fix the problem.

Thanks!

 

its not just the circumferance difference but also the grip difference between your worn front tires compared to the rear. Get new front tires and it should solve your problem

 

1) New tires (the rears) are slippery until "broken in". You can lose traction easily and that can help VDC kick in due to the second problem:

2) The fronts may be relatively smaller due to wear (as you already found out). That extra difference might be making the stagger too large.

I would also check the air pressure in the rear tires. Shops tend to overinflate tires which causes them to bulge making them an even larger diameter. It also reduces contact patch which reduces traction.

 

Thanks. Air pressure all around is at 35 psi. It doesn't feel like I'm losing traction at all, and I'm not going THAT fast, but I suppose given little margin from the front tire wear, even a little bit could throw it over the edge. I've ordered new front tires since I need them anyway; I just hope it fixes the problem. I could also try deflating the rears down to, say, 30 psi?

 

You report having new rear tires along with very worn front tires. I'm thinking that could be a very problematic combination. Your worn front tires could exaggerate under-steer (especially when the car is being pushed by new rear tires). And, the new rears might be slippery for a short time (possibly causing over-steer). I would think this combination, while doing some aggressive driving, could certainly result in some sliding (that VDC senses).

I see from your last post you are replacing the worn front tires.This is certainly a wise decision. I think you may have been driving on a dangerous platform. Certainly your report experiencing engagement of VDC during normal driving confirms this.

re:> "I could also try deflating the rears down to, say, 30 psi?"
No... do not do this since it will only cause more problems. Keep your tire pressure set to the what Nissan recommends for the Z.

One thing I have learned on this Forum is that high performance cars (the Z, Porsche, Corvette, etc.) require vigilant adherence to proper tire/wheel setup and maintenance.

--Spike

 

aftermarket wheels and wider tires is the way to go for max grip. Better in turns. I just turn my VDC off everytime I start up my car.

 

New front tires WILL fix your problem.

 

yes i would get those front replaced at the same time, i did that when i replaced my stock 18" tires, and have had zero problems

 

Just turn the stupid vdc off...i never leave it on unless its raining.

 

Thanks everyone for the comments and suggestions. By the way, both the dealer and the "tire guy" said replacing just the rears should be fine. In any case, I'm replacing the front tires and will report back!

 

You're ZeroCool? I thought you were black...

 

I am currently dealing with the saem exact problem to the tee. I just got new rear tires and my fronts are pretty worn. I get the same response from VDC on onramps. I still happens, even if I turn off TCS. That makes it the VDC as the cause for the automatic control of the difference in size. everyone told me the same....but new front tires.
Also, let me know if you are having this symptom aswell: since putting on my new rears, (without my new front, because I havn't bought them yet) at high speeds I get almost a wobble when changing lanes for example. It almost feels like my steering is loose when I turn the wheel slightly. It is difficult to explain, but if it happening to you then you would know what I'm refering to.

Well good luck and I am glad to find someone else with the same concerns because now it just confirms what we really need to do...buy matching front tires!

 

It's hard to say, but I think I've felt the same thing. Just a little bit of instability. It's very subtle though and, until you said something, I thought it was just in my head. I felt that turning off VDC alleviates this... although the slip light never comes on.

 

The cause could be a difference in sidewall rigidity of the new rears and old fronts. Another possible reason for this is that new tires are slippery during the break-in period. I noticed the same thing immediately after mounting new rears. Handling improved after putting a few miles on the new rears, but installing new fronts (same brand as the rears) fixed the problem completely.

--Spike

 

Man....whew!!!! I thought I was crazy...I had the SAME problems...replaced my rears and kept the front(almost worn) on. I had the lane change issues as well as the SLIP light coming on and the brake engaging at high turn speeds. It feels like I could lose control any minute...I HATE IT! I'll replace the front too. The psi on the rears is 50 while the psi on the fronts are 35...that might be an issue.

How have you guys faired with replacing the worn tires?

 

50 PSI ?? That's insane. The correct pressure is 35 psi all around. No wonder you're having problems.

 

After replacing the fronts with matching new tires, my problems seem to have gone away. Lesson of the day? Replace all the tires on your 350z at the same time!

 

experiencing the same problem right now.
I'm just trying to get more out of my front PS and save some $ you know.
Which tires did you end up going with for the rear and front?