Sebastian777

So I just had my rear tires replaced after getting my wheels powder coated. (Having car on blocks for almost 4 weeks sucked.) I put Michelin Pilot Sports on the rear, and kept my Pirelli A/S tires on the front. I am not sure if I have the front tires back in their original location if that matters. Stock size tires. Also have new TPMS sensers that haven't been programmed yet.

Took the car for a casual test drive, no pushing it at all. On some curves the slip light comes on and I can feel the front brakes activating. Could this be an issue with worn tires on the front and new on the back, or is it likely just new tires being greasy, or is something else? Drove for about 30 miles and still have issue.

guitman32

iTrader: (15)

The braking sounds like your EBD kicking in. Or are you talking about under braking like abs? If you are pushing your car with VDC on the slip light is also normal.

You are running a way stickier tire out back which generally isnt advisable, and although there could be a small diameter change which made the system more sensitive, the former is likely the root cause.

Have you tried driving it with VDC off to see if the EBD still kicks in abnormally? If it does then its just the compound difference causing the fronts to lose grip first.

Sebastian777

Was doing casual driving, not pushing it at all. Wasn't on gas or brake when it was happening. Have not tried turning off VDC, will do that tomorrow.

guitman32

iTrader: (15)

Maybe there is an appreciable diameter change then. That a wheel speed sensor became damaged. Either way does seem to point to tires..

Sebastian777

So I took it out for another drive today. I tried turning off the VDC and the slip light/braking almost when away. I'd say it happened twice when driving with VDC it happened about 20 times. I turned VDC back on and it started happening again.

Does this tell us anything?

guitman32

iTrader: (15)

Tell us its time for some pilot sport fronts!

Sebastian777

noticed this. Should the brake pads be that close to the rotor when parked?

dkmura

iTrader: (64)

This^^. Are you running 225-45-18 (Pirelli) fronts and 245-45-18 (Michelin) rear tires? Those are the stock sizes and let's confirm that before moving on to other potential solutions.

Sebastian777

Yes, stock sizes. Pirellis are near end of life and Michelins are brand new.

Spike100

Different brands of tires might have different diameters for the same metric size.

The Perelli's "near end of life" might be out of specification.

You can probably solve the problem by installing the correct size Michelin Pilot Sports on the front.

Spike100

You said the tire sizes are stock, but (just to be sure) tell us what the actual tire sizes you have on your car.

Sebastian777

225 45 18 and 245 45 18

Sebastian777

So any ideas on why vdc off decreases the frequency it happens? Does that somehow decrease the sensitivity of the wheel slip detection?

Freise

I might be pulling this out of my *** but I believe the VDC off does not disable the system 100%, parts of it may remain active but I don't know enough about it to know how it remains active.
However my guess is the worn tires is creating just enough of a diameter decrease vs the brand new rears to trip the VDC

Sebastian777

Update: Took the car out again, same thing. This time I tried light braking on the curves, the slip light didn't come on, but I could feel additional braking being done by the car.

JMII

+1

I had a similar problem (just opposite ends) when my rear tires reached "near end of life". The lower grip combined with a different diameter was enough to cause fits for the VDC. New tires all around and things were perfect again.

Since the VDC is part of the car's safety systems I would get this addressed ASAP.

Sebastian777

I already ordered new fronts and will have them installed this week.

So I drove to work today and noticed something else. I only see the slip issue at moderate speeds. Taking a 90 degree turn and pushing the car a little bit does not activate it. Taking a highway entrance ramp at 40 does though.

Sebastian777

Update. So I had new fronts put on yesterday. Tire shop said the alignment was already in spec. On a 40 mile drive, with VDC left on, the slip light only came on 3 times. Probably would have came on 20-40 times (sometime multiple times on the same curve) with the old fronts. Also when it kicked on, it was less dramatic than before.

Any ideas?

bealljk

iTrader: (13)

Some of the wiser / more experienced guys can correct me and/or add information...(please do in-fact)...but how I understand the traction control system...

The slip light comes on and braking measures are applied by the ECU when the ECU notices that a difference in individual wheel speeds beyond a given threshold. I thought the number was around 3%?

Meaning, if the rear wheels are rotating 3% faster than the front wheels, than the traction control will flip on...


Furthermore, your steering angle comes into play to account for the car is turning.

The ECU is constantly calculating each individual wheel speed based on geometric calculation using data from from the steering sensor and wheel speed sensors.

The ECU is determining a theoretical rate at which each wheel should be rotating based on the speed sensors and steering angle sensor.

When you are in a tight turn, the outside wheels are going to be rotating faster than the inside wheels. But if the speed of the vehicle is slow enough the ECU doesnt apply any traction control measures. But if you exceed the tolerance nissan set and push past the threshold than the ECU will take over and apply braking...it's just one massive math equation going on in the ECU.

All that to say ... if you are 10,000% sure that your new tires are identical in circumference (and it may be smart to physically measure with a piece of string/rope/tape measure) than consider these next steps (which may require you to take the car to a shop)...

Is your steering wheel and steering angle sensor correctly installed, calibrated, aligned??

Are you wheel speed sensors in good working order?

Are your wheel bearing in good condition?

MicVelo

Right you are bealljk. But the other way around sorta.... the front wheels are already spinning faster due to their shorter height. TCS/VDC as programmed looks for higher speeds to some degree above the "100/97" theoretical ratio the wheels/tires are running at and applies its magic (braking and/or engine cut) based upon the ACTUAL amount the wheel is spinning above the norm, thereby applying the right amount of force to slow that wheel from spinning.

But yes, you're spot on.