Short and sweet, my mate's rx8 has a traction control problem.

 

If you turn left the tcs kicks in very easilly, under quick but totally legal driving and you can hear it, feel it and the light comes on. As part of the test drive I did with him, I went right at a roundabout at a startling rate and it didn't do anything at all, then as I turned left off it quite gently, full tcs event.

 

No flat tyres.

 

No smoking gun.

 

Help me please with what people think it could be. All suggestions welcome.

 

Thanks :)

Check wiring from body to front abs sensors as this could be damaged and only affected when on a slight lock

 

The tcs system is seeing a sudden change in wheel speed and or the yaw rate sensor (if this car has one) and compensating for that.

 

Live data logging whilst on test drive should expose the wheel which is changing speed.

It’s an RX8 and the build quality is crap...:lol:

Ok... perhaps not 'all' suggestions are welcome :lol:

Check wiring from body to front abs sensors as this could be damaged and only affected when on a slight lock

 

The tcs system is seeing a sudden change in wheel speed and or the yaw rate sensor (if this car has one) and compensating for that.

 

Live data logging whilst on test drive should expose the wheel which is changing speed.

 

Would the front wheel sensors affect tcs on a rwd car? My guess would be not.

 

Does the car have stability control?

Would the front wheel sensors affect tcs on a rwd car? My guess would be not.

 

Does the car have stability control?

The Rx8 uses DSC so all wheel speed inputs inc steering angle and yaw rate, plus longitudinal and lateral acceleration inputs are monitored continuously.

Answers my question then, it does have stability control so yea could be fronts. But on a pedantic level it's not the tcs doing it I don't think if the fault is on a front sensor.

 

Chris's suggestion of monitoring it live/logging is of course the best route, but I'm curious Tom, could you tell what it was trying to do? You may have been going too slowly to tell, but was it trying to turn in to the corner more or less?

Well, I didn't want to suggest my thoughts as I wanted people's un biased ideas.

 

The problem came about after he changed both rear tyres from sport ones to rubbish ones following a puncture.

 

He thinks it's his new rear tyres.

 

But they are both the same tyre, and the problem is very much a left hand only problem as if the back right was flat and it was wet.

 

I think there is a grometry problem or a bush gone or something that I can't find without jacking it up. Because I thought it turned left more readilly than it turned right.

 

So I think it is correct TCS/DSC response to a mechanical loss of grip, which was previously masked by having really sticky tyres.

Unless the yaw sensor or something is screwey and it is just triggering the stability programme prematurely on left turns.

 

It makes a rasp noise like going over a cattle grid and you feel it flat spot and you get the skiddy car symbol comes up. It was doing this on a normal swooping left, but let me do about 1G at 45mph all the way round a roundabout.

For it to be as noticeable as it sounds, I would guess the geometry would have to be wildly out...

 

He hasn't had the steering wheel off or something? Wheel alignment done? Could need recalibrating if something has been changed

Chris's suggestion of monitoring/logging would show whether your theory was correct as well though, if it's a front that is causing it then it's probably not the rear tyre change!

I think he should start with getting it tracked. I'm prepared to be wrong. But I think it was physical. All the mazda people are saying things like.

 

The DSC is very sensitive to the wrong tyres.

 

It can't be alignment because its only using wheel speed to trigger the system (well geometry can cause slip and therefore wheel speed).

 

Rx8s don't like the wrong tyres

 

Don't mix and match front and rear tyre type (I get that for left/right but not front/back. Mine are always different front/back)

 

Reset various ecus (really?)

 

Is it the diff causing it (surely not)

 

Is a rear brake dragging (could be that on the unloaded tyre I s'pose)

 

I just think it's a physical thing :lol: I'd be so supprised if it's something else. I asked if he'd had the wheel off or moved the yaw sensor so it's twisted.

I would be surprised if it was only wheel speed feeding the stability control. I can't see how it works unless it compares yaw angle (ie actual car angle) to steering wheel angle (ie desired car angle). Afaik it will only use wheel speeds to feed tcs, but not stability control

Ok... perhaps not 'all' suggestions are welcome :lol:

 

:lol: no offence. My dad had one for a bit when they were newish and it wasn’t great.