[eddyj14]

Hi guys I'm new to this so bare with me..
I recently purchased about a month ago a 2006 330xi
Two day ago I dropped the car on h&r sport springs and out on some
18 inch xxr rims that my cousin had so I took them
Fronts are 18x8.5 backs 18x10 with 12mm spacer..
Ive had no lights on the car since i got it but after putting the rims
On my 4x4 light comes on when I start driving it only when I
Start driving the car when I turn it on it stays off..
And also my traction controll light on too..

The lights are in yellow
And I did disconnect the negative in the battery
Before putting rims on because I had the tire pressure
Light on and wanted to see if the light would reset.

Could my lights go on when I drive it because of the rims
Or the drop in springs?

Like I said when the car was stock it didn't have these lights
Only after putting springs and rims.

Thank you guys
God bless

[///M3NACE]

Whats your tire size you could've ruined your transfer case.

[scotty_miller]

You made sure your rolling diameter was less than 1% right...?

[ssmith96]

Originally Posted by scotty_miller

You made sure your rolling diameter was less than 1% right...?

Highly doubting that. Hope he didn't ruin the car.

[CombatNinja]

I think the problem is your stupid wheels.

[eddyj14]

Hi guys front tires 215/40/r18 x8.5
Backs 225/40/18
And I know I sound dumb but it's my first BMW don't know anything :/
I don't know what you mean by rolling diameter less than 1%
What is that? And how do I make it 1%
I have only been driving car about 2miles a day
To work and back 2 days with today with light on

[parabola]

Your problem is most likely different rolling diameters front to back, which is a no-no on awd models.

215/40/18 will have approx 24.772" rolling diamater
225/40/18 will have approx 25.087" rolling diamater

Based on above numbers, there is 1.27% difference, so far I've heard staying below 1% will be OK, you should confirm this.

These numbers can vary also based on the tire pressure, if your fronts are under-inflated it will make things worse (decreased rolling diameter).
Put the same size tires all around.

[eddyj14]

Oh man okay I didn't know anything about that
Thank you... So what tires should I go with in the
Front? To fix or make it less than 1%

[eddyj14]

But how do I put same tires all around if back are
Wider?

[Meeni]

215 on 8.5 is stretched. You could just put 225, they are even smaller than recommended for that size anyway. But...

225 on 10... Well.... I don't know what to tell you. Go to some shop that have people that know proper fitment for proper wheel sizes so that your car is not dangerous with its over-stretched tires...

[matraks]

225/40/18 front
255/35/18 rear
Just use online charts.

[eddyj14]

Is that gonna give me the stretch look I'm
Looking for?

[matraks]

No. They are original sizes. I think that stretch will not be good for any 4x4.

[parabola]

You're dealing with different rolling diameters here, go online and search for "tire rolling diameter calculator", match the numbers front to back as close as possible.
Personally, I'd put same size all around on am awd car an forget about "stretch".
The way you have it now, you'll ruin you awd system, transfer case or something else, which will be major $$$ to replace.

[eddyj14]

Here is what a calculator gave me like you said

Front tire 215/40/r18= 24.772

Rear tire 225/40/r18= 25.087

I'm guessing you have to subtract which is 0.315

Got this from a calculator

[parabola]

The difference you show is in inches.

You need to be looking at percentage difference, which is about 1.27%.

[Gordy]

offtopic but is their any pictures of your car you could post I've been wanting to put on some h&r springs with some ccw rims, which is what the xxr is a replica of I assume.

[eddyj14]

Oh okay my bad... I tried but says I have to reseize
My pictures not sure
How

[Envuks]

You likely blew your transfer case by putting on the wrong size wheels. A rwd car could handle that for for Xdrive thats not a good setup at all. It's rare that it would happen so quickly after you out them on. Perhaps it was on its way out anyway.... The stretched look might be the dumbest thing to hit the automotive world since glow lights under the car. It looks like crap, handles like crap, and can lead to situations like this. Get a normal setup

[parabola]

I wouldn't necessarily say the transfer case is toasted, it could be simply wheels sensors reading wrong speeds and throwing a light.
Put the stock wheels back on, drive and check if the light is still on.

[eddyj14]

Okay I will do that... One more thing if my backs are
225/40/18. What seize tires can I use in front to make it
Less than 1%?

[Efthreeoh]

So what no one has explained to you is why the tire diameters need to be the same front to back. On an all-wheel drive car there is a center differential (transfer cases are usually found in 4x4 trucks) that applies power to the front axle and rear axle. The center differential is computer controlled and can vary the amount (percentage) of engine power between the front and rear axles. It does this though a clutch mechanism.

Regardless of the amount of power that is directed to each axle (it's always 100% combined) both axles have to run at the same speed. The speed of rotation of the axle is tied to the diameter of the tire, so to have both axles rotate at the same speed the tires need to have the same overall diameter. If the tires are of different diameter between the front and rear axles, the center differential is stressed because the gearing inside it can not compensate for the difference in the speeds of each axle, so eventually the clutch mechanism takes the brunt of the stress and breaks.

Using a staggered wheel set up can create a difference in the tires diameter for the front and rear axles if the tires are not sized correctly to have the same overall diameter for all four tires (which is what you did). A tire's size specification, for the front tire example of 225/40-18, means the inside diameter of the tire that attaches to the wheel rim is 18 inches, the tread width is 225MM, and the 40 means the height of the sidewall is 40% of the width of the tread, so 225MM x 40% means the height of the sidewall is 90MM, which determines the total diameter (rolling distance) of the tire. Reducing the sidewall for the rear tires from 40% to 35% against a 20MM treadwidth difference gets a sidewall height of 89.25MM (255MM x 35% - close to 90). So the staggered setup of 225/40-18 in front and 255/35-18 rear has essentially the same tire diameter for all four tires.

If it were me, I'd get 4 wheels of the same size and correctly size the tires for an Xi car.

It's best to first understand how things work when deciding to modify them.