Help Please - Traction Control Cutting In When Not Required

Hi Guys Please help. Last week I fitted some new rear tyres which are Falken in the standard size same as removed but obviously not N rated. I had seen mixed reviews but thought I would try them. They have been on a week now so 500 miles and pressures are correct. The issue I have is the traction light comes on and the power cuts or the brakes cut in when not require. Typically this happens on a bend when at steady speed or when slowing down into a bend. Strange thing is when accelerating out of bends it does not happen. Any thoughts on what to try should I increase or decrease pressures? Should I get new front tyres to match the Falkens or should I just get some continentals like I had before? Or could it be something else like a damaged or failed sensor or component? Cheers Winny

I had a BMW 330 on which I changed the rear tyres only... it handled dreadfully afterwards, much like you describe, improved after a while when the tyres were properly worn in. It could be the difference in tread depth giving odd wheel speed sensor readings. What is the tread depth on the front?

Off topic - Is that a sneaky bit of Beachy Head I spy?!

I would start by getting an Indy to do a steering angle calibration .. After that we are into the rotational difference between tyres .. ie the fronts might need changeing . Basically the car thinks its starting to slide , it can only measure this by the rotation of the tyres .. if not N rated then you are out of specs but that shouldn,t make a huge difference .. its a bigger problem to have an N rated and a non N rated on the same axle . Either ways .. steering angle sensor calibration first then we go from there .

Broken reluctor ring.

Is your speedo giving a reasonable reading or is it a fair way out? Also, is it one sided that the braking is on or front/rear? You can tell by feeling the discs after its done it. One (or a pair) will be a lot hotter

I can't see it being tyre related so long as the tyre sizes are correct.

Thanks for the quick response Front tyres are 3-3.5mm continental contact sport 5s non n rated. Just checked the pressures all consistently down 2-3 psi but would be expected with recent temp drop By chance it is going into Parr tomorrow for a 12k service would that include scanning for codes? And would a steering calibration cost much while it is in there? Yes that is beachy head. Cheers Winny

Thanks Alex Speedo seems accurate. There is no odd braking but will check wheel temps when I get to work tomorrow. Could it be the front diff? I have noticed it it seems stiff (tyres judder) when pulling away from cold in the morning but it goes within 20 seconds of driving this has also started to happen post tyre change last week. Cheers Winny

I thought you said the brakes cut in when not required?

I am sure Demort is right re the steering angle sensor needing a reset. Parr can do this easily. The judder you experience may also be related to the steering, with the back wheel now having more grip and pushing the front a bit more. Is this mainly when cold, low speed with some lock on?

Alex I'm not sure how the traction control works but yes driving along a bend or going into a roundabout the light comes on and the car starts to jump about I'm not sure if the traction control cuts the power or applies the brakes (or both?) but when braking going into a roundabout if it comes on you do get that on off pulsing from the abs Braking without a bend the brakes feel fine and the abs stays off John The judder seems to be only when cold and only if turning out of a parking space or the drive way. I have had this before but not for a long time and I seem to remember it being a cold thing. Could his really be tyre related and how / why would a steering sensor suddenly fail following a tyre change? Is it just a coincidence? Cheers Winny

My money's on a broken reluctor ring. Mine was doing a similar thing. After feeling round each disc (and feeling the heat), the rear RH brake was actuating on its own causing the judder and also when you pressed the brakes, you also had the pulsating. Turned our the rear LH reluctor ring had broken. Was still in position but giving an incorrect speed reading, conning the traction system that the RH rear wheel was travelling a lot faster than the left so applied the brake to slow it down.

What is the date code on new tyres? Could they be losing grip due to release agent from the mould? It might happen at lower speed than expected due to low temp and damp roads? Just a thought. Hopefully parr will resolve it.

what size are the front tyres? - i bought some second hand wheels for my car and the front tyres were actually the wrong profile! The larger profile fronts meant that the rears (correct size) were always turning quicker and cause the ECU to back off the ignition timing and all sorts - changing the fronts when i spotted it made a significant difference to performance and its behaviour...... ...... if it's not that and i don't expect it is..... I'm with Alex - check the traction rings....