[Daskoff]

So I got a flat today and no biggie I pulled out my spare tire kit and proceeded to change the flat. Pulled off the flat rear tire (255/35/18) and took out the spare but when I compared the two, the spare (135/80/17) appeared to be much taller that the original. What the heck is going on. I compared the sizes on tirerack.com and the diff is actually 1/2" taller for the spare. I purchased this kit which was supposed to fit the e90 sedan. Is this normal? Is the 1/2" difference on one rear wheel compared to the other rear wheel going to cause havoc with the traction control when it senses a speed differential between the two rear wheels? Anyone used this size spare on the rear? I have not driven the car since I changed the spare, I can take another car to fix the flat but I am thinking in the future when I get a flat on the road not near home.

Thanks

[Daskoff]

Looks like nobody has been in this situation so here is what I found on a website that sells the spare tire kit for the E90.

Disclaimer:

While this fits over the OEM brake setup with no rubbing, it is noted that this spare tire kit was designed for the E60 5 Series (Rolling diameter of 25.5 inches) the rolling diameter on the E90+ 3 Series is 25 inches, this is a 2% difference in size which is deemed acceptable in the tire industry. With that being said, the purpose of this spare tire kit is SOLELY to get you out of a bad area (traffic, security) and NOT for any prolonged driving. By purchasing this spare tire kit, you acknowledge this statement.

[BruceJ]

I'm gonna tell you what you already know, or should since you at least took a moment to do more than just visually compare the spare to the original.

Of course there will be issues with traction control; and everything else related to driving. But IF you treat it, and the situation, as it was engineered, it works. Its a EMERGENCY spare, engineered to get your car moving again when you have a flat; AT LOWER speeds, and with much more driving caution. The original wheel must be replaced ASAP(immediately), period; Otherwise, you act irresponsibly, and will either be lucky, or not. The diameter difference is the least of your worries, its much smaller in width, meaning the contact patch on the road is commensurately smaller. The tire compound is probably not as effective (sticky) or as durable as your original either.

(Pardon the rant, soapbox follows) It is not a replacement wheel/tire designed to provide the same full functionality of the original. If you don't have the cash, bust out your credit card, get a loan, etc. Its much cheaper than replacing your entire car, paying a lawyer to defend you when sued for operating the vehicle in a blatant, irresponsible manner when you crash into another vehicle. Yep, that's exactly what the lawyer and the judge will say in court. You will be a leaf in a hurricane.

ONE of the main reasons why BMW got rid of the T-spare is USA litigation. They didn't want to be responsible for people that order coffee and cant understand its hot. They could have kept it, or offered it as an option, but that makes them complicit in the customers ignorant, irresponsible actions. I still see some of these tires on GM vehicles (SUV's) and ignorant, lazy people that drive around on them for month or more. In this day and age a tire can be shipped to nearly any location CONUS within 2-3 days.

Rant over, sorry.
May be time for some new tires (cause you also know you need to replace both on the same axle)

Good Luck
Bruce