ayc light

[wantavr4]

1 ayc bar almost constantly on?

while waiting for my other two wheels to show up i put the two wheels i have recieved on the car today.
I now have 17s on the front and 18s on the back.

Would this cause 1 ayc bar to stay on for long periods of time?? only one bar lights up, never two or 3.

or, i painted my brake callipers, is there any ayc sensors i could have got paint on by accident?

Could the impact of hitting the pothold which destroyed my wheels done damage to the ayc and if so what do i look for?

or finaly, my brakes are fcuked could that be the reason?

Cheers.

[Ryan]

Are the tyre pressures on the rear wheels equal?

[chris g]

As a worrier about wheel/tyre size combinations, I would want to put on wheels of same size...

[wantavr4]

Yup all wheels are of same presure ryan, double checked this morning.

Chris my plan was to put the 4 wheels the same size untill dhl lost 2 of them.

[Roberto]

I'd get the wheel balance checked or did you get the new wheels balanced yourself before fitting?

[Turbo_Steve]

The different wheel sizes will be giving it the heebs unless the rolling radius is almost exactly the same, which I doubt.

So the AYC system will see different wheel speeds and be trying to correct.

If you keep driving it like that, I would guess that it's likely it'll wear out one of the fancy pants clutches in the diff eventually.

[bradc]

You haven't told us what size the tyres are and how much tread is on each tyre.

[bakerboy-2007]

I had this problem when i fitted on my 18's, must ensure tyre pressure's and also the same tyres and tread pattern all round these things sorted it out for me...........

good luck

[AlanDITD]

brakes stuck on one side?

[wantavr4]

Brad:
rear 235 40 18
front 215 or 225 45 17
all tyres are praticalt brand new.

Rob, iwas gona wait till i get the other 2 wheels before i get them balanced but i supose ill get them balanced tomorrow to see if there is any difference.

steve:
If the balancing makes shag all of a difference ill probably take her off the road after tuesday until i get wheels sorted.

Alan:
To the best of my knowlege no brakes are sticking. Like when ii brake hard the car will stop straight rather than go to each side. the brakes are getting a complete going over anyway tuesday. Replacing master cylinder, tinking of mintex dot 5 fluid instead of the dot 4.1 blue line stuff i have and new pads.

Baker boy:
i was supposed to recieve a set of 4 wheelswith 4 identical tyres, must locate new wheels before i can tink about matching tyre tread. Maby r888s for the summer.

Cheers for the replys and any other information gratefully apreciated.

[bradc]

215 or 225/45/17 is quite a bit smaller than the 235/40/18 size.

[Roberto]

215 or 225/45/17 is quite a bit smaller than the 235/40/18 size.


Tyre rolling circumferance of 1907/1907 mm against 1968 mm.

But would having that difference between the front and rear make a difference to the AYC.
I don't know totally how the system works, but thought it was based on the rear axel only.

Where as I would have thought it would matter more to the transfer box.

Or am I tired working a night shift and talking b0ll0x?

[bradc]

No idea how you got those figures but the 17's are either 1964mm or 1993mm, the 18's are 2027mm

With a difference of that much it could be the wheel speed sensors are reporting back such different speeds that it causes problems.

More likely though that the tyres aren't all inflated to the same amount.

[Turbo_Steve]

Or am I tired working a night shift and talking b0ll0x?

Yes and no.

Mechanically, you are correct: the AYC system only actuates the rear wheels, and the transfer diff will be bearing the brunt of the extra work of the differing wheel sizes. It's probably shortening it's life, but it'll take a while before it kills it as there is a degree of lassitude for differing tyre-pressures, getting a flat, going round corners, etc etc.

What you're missing is that the AYC isn't just mechanical: it's an electronic system that looks at all four wheel sensors, the steering position, throttle position (iirc) and a lateral G sensor to establish the present attitude, direction and yaw angle of the car compared to what it thinks the driver is aiming for, and then uses the active rear diff to compensate.

So, with different sized front wheels, it may believe that the rear of the car is stuggling to get traction and thus "diddling with the diff" everytime the steering wheel is turned. If the AYC is working all the time, the hydraulic fluid is working a lot harder to keep the clutches actuated, and the clutches themselves are likely to be slipping continuously which means more wear and more heat etc etc etc.