Hi, i have a 2000 2.0 Zetec, the TC light keeps coming on and off intermittently. Had the ecu read and no codes have been flagged up. I have noticed though the 2 front tyres are 205/45/16 and the rears are 205/55/16, will this make a difference to the TC or is it ok as long as the 2 tyres on the same axle are the same size? Thanks for any help, Ade.

 

i take it its flashing when just driving along normally and not booting it about in the wet? lol.

standard size on 16's is 205/50.

presumably if the tc system is using the rear wheels as a reference for actual vehilce speed then by having smaller tyres on the front will make the fronts spin faster than the rear (conversly the rears spin slower as its the fronts that are driven) which could confuse the system.

only way to check for sure though is fit another set of wheels with same size tyres all round. got any friends with focus'?

if you have standard brakes on then you can fit any mk1 focus wheels too

 

Yeah thats what i thought if the fronts were spinning faster than the rears, it comes on and stays lit after a couple of mins driving, doesnt flash as i know thats when its doing its job lol. I'll try and borrow some wheels off someone, cheers for the reply mate.

 

I'll guarantee that's what's causing it. I had the same problem when I tried 215/45/17's on the rear and 40 profiles on the front.

 

Cheers mate, i'll try swapping wheels this week

 

my mate has different size wheels front to rear on his st170 and doesnt have any traction control issues and as far as im aware it only works on the front wheels anyway

 

The TC on my ST170 has a sensor on the rear beam attached to the drivers side lower control arm just like on the driver side wishbone so it definately looks for loss of traction at the rear?

 

what size tyres though as they may have a very similar circumfrence (spelling shit i know lol).

and yes the traction control only works on the fronts as they are the driven wheels but its whether or not it uses the signal from the rears as actual speed to determine the ammount of spin. i dont know the answer but it would seem if hogdog is right then that proves my theory.

 

fair enough im just guessing really but my mate deffo has no problems with different size wheels

 

215/45/17 front 225/40/18 rear they are visibly different if you put them side by side as i was bollocking him fo fitting them as it is pointless having bigger wheels on the rear of a fwd car lol!

 

they're actually very similar in size compared to cozziekid's. a quick online tyre size calculator shows cozzykid's to be 7% speed difference and your mates only 2% which is probably within the systems limits as anything upto 5% is usually considered acceptible and some say beneficial.

all depends on the design of the system of course and i could be way off for the focus so i could just be talking complete crap

 

2% doesnt sound a lot to be fair but when i put the wheels side by side it did look a lot almost an inch different

 

oh well, maybe some are more sensitive than others.

his definately has traction control right? lol gotta ask

 

The traction control system will allow a certain amount of 'slip' otherwise it would be on all the time...even tyres of the same size with different amounts of wear would cause it to come on if it didn't allow a little 'slip'.

The size differences Cozziekid has are obviously different enough to create an issue.

 

I have a sensor on my rear beam to the right of the Anti roll bar, is this linked to the traction control?

 

that looks like a load sensing valve to me mate which is weird as i thought the st170 had abs. my 2l zetec has rear discs and abs and does not have anything like that on it, only rear sensor is the wheel speed sensor.

 

The ST170 does have ABS, the ABS Sensor is in the back of the stub axle, there is an identical load sensing valve on the driver side wishbone too, i always thought they were related to the traction control as when i purchased new wishbones and rear lower control arms they did not have the rivnuts to attach the sensors to so i had to modify them to take the sensor?? This is why i was suprised a 2.0l non ST focus had traction control. Maybe they are for ESP which was an option but they are not in use as i only have TC Confused

 

Isn't that switch for headlamp leveling?

.

 

I have no idea? It may well be, the Xenon headlights i have are self leveling so maybe your right?

 

i didn't think of that so could well be.

 

Thanks for the help guys - problem sorted It was the tyres, had some new 205/50/16's fitted today and the TC light doesnt come on now. Just got to figure out my central locking now lol.