TC light and tyre size
 

After having some rear tyres fitted I started noticing my TC warning light coming on without wheel slip.
The fronts were replaced recently with maxxis and rears were matched. Or so I thought. On closer inspection as things didn't look right to me, I have 205/50 17 on front and 225/50 17 on rear.
Will this confuse the TC into thinking the fronts are spinning when they are not?

what car are you driving? what engine?

On some cases you might not notice the slip when there might actualy be some (as the TC is dealing with it)

But with your tire sizes, others might correct me if im wrong but they should all be the same width .... your tire setup sounds like something for a RWD car

To my understanding - yes, exactly whats happening. 205/50/17 are standard size on that model and car has 1999mm circumference programmed in so it knows its suppose to be doing 500 revolutions per 1KM. on 225 ones, the actual circumference is 2062mm and car does only 485 revolutions per 1KM. I am not surprised that this can trigger TC warnings.
You should have it sorted ASAP. If thats what you were given as "matching set" they should immediately fix the mistake.

It's not my tyre setup, and your right those sizes are for rwd or stanced veedubs!
I asked for 205/50s and my invoice says 205/50s but looked at the car yesterday and thought the tyre wall looked too big on the rear for the same make and tread pattern tyre.

Car is v50 2.0d, and traction light will come on much easier than it ever has done. I text the mechanic I use and he said the tyres are confusing the abs, and it'll probably need re programming on diagnostics when the correct size has been fitted.

not sure what he means by that sentence, but once you are back to 205/50 here will be nothing in the car itself to reprogram - the tyre size is programmed into car's brain and it wont change even if you fit 19' there. It will just calculate deviation from its default and either display wrong speed or trigger TC in that case. So just get the correct ones on and dont worry :}

I've dropped it off at the tyre fitters, as my Subaru was in there anyway after having tyres last week that were badly out of balance! New staff in there, service has gone downhill somewhat!

They are changing them and said it would give the TC a hissy fit, and he will do a reset on the abs so it doesn't throw the abs/TC lights back on. Fingers crossed they don't f**k that up!