In 2003, purchased new MB E320S/SW. In 2004, wife replaced all tires (including the spare) with michelins.

Along about Spring of 2007, the ABS and BAS/ESP warning lights would turn on, intermittently, while I was driving on an Los Angeles freeway. They never stayed on long.

Intended to take the vehicle infor Mercedes check-up and service, butother things got in the way, until July of 2007. When we took it in the first time, the MB folks couldn't find what was wrong. Warning lights continued to appear intermittently, but with what seemed like greater frequency than before.

Took the vehicle into MB folks again,on 1/8/2008, for Flex Service B and reported warning lights again. This time, they said they found and replaceda faulty stop lamp switch which was still under warranty.

No warning lights now. But ...

Along about 01/13, we took the vehicle into the company (intentionally not named here), who sold us thetires in 2004, for service: rotation, balance, etc. Told the unnamed tire service company that it looked likewe had a slow leak in one of the tires. They found the leak, declared the tire unrepairable, and told us that they couldn't replace the tire with the spare tire we had because it (and one of the other four tires) was a different size from the remaining three of the total five tires purchased from them. The unnamed tire service company guys insisted that mismatched tires were dangerous.

We pointed out to them that, if we had five tires, three of which were 215 in size and two of which were 205in size, thenthe unnamedtire service company sold us mismatched tires back in 2004. We ended up getting threebrand new tires for the price of half a tire.

Now, here's the first question:

(1) Could the fact that we were running the car on four tires of two different sizes have initially caused the ABS and BAS/ESP lights to turn on intermittently?

Additional info for the second question:
[blockquote]
Along about March, after the warning lights began appearing but before we took the car in to have them checked out, I had an accident. I was coming down an off-ramp at
legal speed. The off-ramp makes a sharp turn before feeding into a street. The rearend of the car began to slide to the left, I turned the steering wheel counter-clockwise to avoid driving from one side of the offramp to the other, but that only made me drive up and onto the ramp curb on my left. End result: Left-front rim damaged beyond use and repair and less-than-pretty damage to the front bumper and the lower portion of car between the left-front and left-rear tires.[/blockquote]
Now for the second question:

(2) Could four tires of two different sizes have caused, contributed to, or facilitated the accident that I had? (I've driven off that off-ramp frequently over the past 21 years, so I was no stranger to it.)

Trying to explain to my wife why I should not have my driving privileges revoked or be carted off to a nursing home, I am ...

Curious in L.A.

 

if there are different tire sizes on the car it will put on the esp bas light, it thinks that the tires are slipping. because of different tire roation speeds it will cause this issue. seen it many times. your main concern in the tire size is the aspect ratio number which is the second number....70,60, 55, 50 is the height of the tire,the 205, 215 is the width of the tire, the height is what affects the esp traction control.

 

OK. Heres my input for what it worth!

Different tyre sizes CAN impact the ABS/ESP system.
However some MB's are fitted as STANDARD with different tyres Front to Rear.

Having different sizes ACROSS an axle is NOT A GOOD IDEA. You don't say how yours were fitted.

When the ABS etc warning lights come on they come on FOR A REASON and the vehicle should be taken to the dealer as stated in the handbook. The car is not dangerous when the system is not working. It just can't assist when the vehicle goes "out of control".
Faulty brake light switch is a common failure causing the light to come on.
However differential tyre size especially across an axle can also cause the system to malfunction as can differential front rear size greater than the parameters allowed in the software.

Re your accident: ABS/ESP systems are there to HELP once you have put yourself at RISK.
If your car skidded you must have been going TOO FAST for the conditions PREVAILING. (PERIOD).
However to make you feel somewhat better MAYBE the road had spilled Diesel, or similar, on the surface which you did not see/was not visible which significantly altered the amount of grip available when compared to normal.

Now ABS/ESP is there to help once the car is on the limit of skidding. If the system wasn't working (yellow light on) you didn't get the assistance of a truly useful system so you were down to your own devices. i.e. Steer into the skid and NO BRAKES. ABS has the advantage of being able to apply braking on just one wheel and with electronic data regarding which wheel is skidding and what direction the car is heading in vs where it should be going, can make decisions that even the best driver can't.

So. The ABS/ESP didn't cause the accident. They may not have been available to help you in your "hour of need". The car was going too fast for the prevailing road conditions.

So how did the garage come to fit the wrong tyres or were they in fact the correct tyres?