davidv

iTrader: (2)

The front tires are taller than the rear. This may be the reason for the TCS- slip problem.
Overriding TCS by turning it OFF may not be 100 percent effective.

Spike100

Unless you have the 2005 Grand Touring model (vs. the Touring model) you probably have TCS and not VDC (as you stated). You can discover this by looking at the label on the switch.

The tire dealer sold you the wrong-sized front tire (245/40-19” when it should be 245/35-19”). I would think you have some recourse here.

As David already mentions, turning off TCS may not provide a safe driving car since taller tires on the front could also adversely affect ABS. I would certainly get this problem fixed.

--Spike

GeturZZZs

iTrader: (2)

if i put a biiger side wall on the front than the back would that cause it

Spike100

Not necessarily...

It isn't the sidewall height (i.e., section height or profile) that you need to be concerned about, but rather the overall diameter that you need to respect. If your front tires have a greater overall diameter than your rears, you're in for trouble.

An Example: You could run 245/40-18” front and 275/35-19” rear.
--Spike

DrPhantum

I have the standard Touring Model... No VDC.

Unfortunately, I requested these tire sizes. Flame me if you want, but I did *some* research on safety, and the site I went to said it would be OK. I guess I should have posted here first. They did mount and balance the tires without ever warning me, though...

How will it adversely affect my ABS? Will the ABS never turn on... or will it be more sensitive? I'm guessing the latter is a safer condition. Are we SURE there's no way to reprogram? It sounds like an easy code change to me... I'd think that as long as the kinematics of the car aren't changed drastically (and they can't be... there isn't a HUGE difference), that a recalibration of the computer is all I'd need.

At least only the front tires are the problem. What size should I go with in the future?

Thanks again for the help.

DrPhantum

Wow... I wish I had seen that post when I bought my tires. I would definitely have thought twice. The site I went to gave a wider tolerance on stagger... I think it was 1.25" But it wasn't Z-specific. Duh

If I want to keep the front tires taller, for matters of having more rubber between my rims and the road (potholes), would I be able to put 40s on the back, so that they both match? Or, do they have to be 35 for some reason.

DrPhantum

What am I doing wrong? According to this site, there is a difference of only 4mm (.1") between my front and rear tires...

http://www.wheelsmaster.com/rt_specs.jsp

davidv

iTrader: (2)

For some reason I do not think that you are getting this concept. As I and others have mentioned: the front tires are taller than the rear.

DrPhantum

I get the concept... Did you look at the attachment? It says the difference is only .1" That is not enough to throw off the TCS. I even said "what am I doing wrong?" If you say I don't get that concept... then you are telling me that I am doing everything RIGHT. We both know that isn't true.

Spike100

Doc,

In fact you are missing the point (concept).

You are correct when you say the difference is very small, but the point you do not seem to understand is this:

Your front tires cannot be (must not be… should never be) taller than your rear tires.

If your front tires are taller than the rears, TCS will not operate as to specification, and ABS may not work properly either.

--Spike

terrasmak

iTrader: (8)

Read tSpike's post above me , and BTW the rear is suppost to be almost 1 inch taller of a tire, not within 0.1 inch.

DrPhantum

I've been under the impression that the tolerance is +/- 1" from Front-to-Rear or Rear-to-Front.

Please consult the thread here and read the part that says this:
DavesZ#3 says that a stagger of less than 1" is acceptable. Now, I can agree that in his post, none of the front tires are taller than the
rears... and I just noticed that now, along with the fact that he defines "stagger" as the fronts being a little shorter than the rears... but
Dave never expressly said "the fronts cannot under any circumstances be taller than the rears, but the rears can be taller than the fronts."
I interpreted the site as meaning that a stagger from front-to-back or back-to-front of less than 1" is OK. My bad... I apologize.

But again, I digress... The tire size calculator on the wheelsmaster site showed that, with my tire sizes, there is only a 0.1" difference. This
is a negligible difference, and I know that it has to be greater than that. I was asking someone to help me figure out what I had done wrong
in the tire calculator.

Plus... If anyone ever said "your front tires can't be taller than the rears... but the rears CAN be taller than the fronts, but only if it's
less than one inch," then I didn't catch it, and I'm sorry. I understand that a difference in tire height has a direct effect on an offset in the
speed sensors (manifested through the difference in tire circumference when calculating speed in revolutions, or number of circumferential
lengths that pass a given point, per second)

I get all of the physics stuff... I took a lot of classes covering that kind of stuff, and designed crude sensors to measure this kind of
stuff... What I don't get is how the Nissan dealership told me that ALL FOUR of my tire speed sensors agreed with each other (within an
acceptable tolerance), but that the speedometer disagreed with the popular value given by the tire speed sensors. If that is true, then the
difference in tire height from front to back has a neglible effect on the speed reading... and hence should have a neglible effect on the
TCS/VDC.

I did upsize my rear tires, but if the speed sensors agree to within an acceptable tolerance... then I'm led to believe that the circumferences
are ALSO within an acceptable tolerance. That's the hangup... and that's why I was hoping to just reprogram the speedometer and/or tire speed
sensors so that they agree with each other. If the fronts and rears were giving different speeds, then I would agree that I just simply need to
downsize my front tires.

So... I'm sorry to post all that stuff... but I want to get over the hump of "DrPhantum... you just don't get it..." and start attacking the
problem, and trying to figure out how to solve it.

DavesZ#3

iTrader: (26)

Sorry for not being explicit enough. In general, the fronts should not be taller than the rears. 99% of the time, when somebody stumbles across the forum and starts a thread "just got new wheels/tires and now my slip light comes on randomly/regularly/etc", when questioned the OP reveals that the fronts are the same size or taller than the rears.

Yes, a burnout will wear some off the rears, but turns and toe-in will wear out the fronts too.

Besides some builtin tolerances for front-rear stagger difference, over the years it appears as though the sensitivity to the stagger has gotten less since the earlier models. I don't know if the ECU is more forgiving or less people are making the mistakes of putting the wrong sizes on, but the number of complaints has dropped off a lot since the 03/04 years.

The biggest problem in all this is that Nissan has never published anything that defined hard limits. Rumors were that 0.25 to 0.75" was the acceptable stagger. We've seen people with 1" stagger with no problems. I drive my autocross setup with no stagger to and from events and never have a problem with TCS or VDC.

DrPhantum

So... I guess my next question should be:

"Do you know anyone that's looking for almost-brand-new 245-40-19" tires?"

Spike100

^^ That's a long message, but I'm not sure what it says.

My only comment: "You can lead a horse to water, but you cannot make 'em drink."
____________________________________________
EDIT: I see that Dave explains this and you now seem to agree.

--Spike

DrPhantum

That reminds me of an old saying, too...

"If you're not a part of the solution... you're part of the problem"

EDIT... Dave did explain it... and I do agree. I never caught that the fronts couldn't be taller than the rears in the forum posts I read... It was never explicit enough for that fact to jump out at me. And I apologize for any wasted time.

So, now that we've established that, how can we finally explain why the Dodge screenshot with my tire sizes says that there's a 1.18" difference, and the wheelmaster site says that there's a .1" difference? Really, though... I just decided that it doesn't matter. It's not going to help me, so "if it's not part of the solution... it's part of the problem." Anyone wanna buy a pair of oversized tires?

DavesZ#3

iTrader: (26)

The problem with those tire calculators is that they are just that - a calculator. They are using a formula to estimate the OD, etc. Every manufacturer's tires will be a little larger or smaller than the "book" dimensions.

davidv

iTrader: (2)

I am a victim of TCS.

Difference size tires on the rear axle. When I would get to about about 60 MPH the car would shut down. Shut down meaning that the motor shut OFF, and I would have to pull to the side of the road. TCS ON or OFF it didn't matter.

I surmise that TCS is measuring difference in wheel RPM. When the difference exceeds the maximum allowable tolerance (at 60 MPH in this case) the TCS computer signals the ECU to shut down the motor. The TCS computer is pretty powerful computer.

davidv

iTrader: (2)

No need to apologise. All of us are learning. And airing our experiences is a learning experience.

The VDC/TCS/ABS computer is a powerful tool. We have anecdotal evidence of symptoms, diagnosis and results. Want we are not privy to is the algorithms used and tolerances.

Spike100

^^ Good point... Dave also mentions that we really do not have specifications on the tire-sizing as it relates to TCS/VDC/ABS. One reason could be as simple as protecting trade-secrets for the devices, or maybe to protect against lawsuits that are so common in our litigious society.

It’s apparent that Nissan wants us to respect the OEM tire-sizing, at least the overall diameter.

--Spike