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I recently got the tires changed on my 2005 Brabus Smartcar fortwo. The guy didn't listen to me and put way different size tires on it. So when they were done I left and the three lights on the left side of the console went on and the speedometer stopped working. So I brought it back and he said no problem just drive it for 30 miles and it will reset itself. So I did that then the engine light came on and there started to be a knocking sound come from the rear. Then the car did this weird thing where the shift window came up three lines and was stuck in gear. Does anyone know if these tires may have screwed my trans? Thanks in advance!
 

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What size did he put on your car and how much larger were they than the stock Brabus sizes? My 2009 US spec Brabus came with 215/35-17 on the rear from the factory. Several years ago, I installed the same size on the front. No issues or nanny intrusions at all. It sounds like you have other issues than tire sizes. I am sure someone with more mechanical knowledge will chime in soon to offer help. Also, Welcome to the forum!!
 

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What size did he put on your car and how much larger were they than the stock Brabus sizes? My 2009 US spec Brabus came with 215/35-17 on the rear from the factory. Several years ago, I installed the same size on the front. No issues or nanny intrusions at all. It sounds like you have other issues than tire sizes. I am sure someone with more mechanical knowledge will chime in soon to offer help. Also, Welcome to the forum!!
Hello, he put 195/45/17 tires on. Is this a problem?
 

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…the difference between the two … installed and USA Brabus specs …in circumference is 3” … rotating 440 less revolutions per mile … 1” larger diameter …and here’s where the computer can get confused with the spedo error at almost 3 mph higher than actual speed...

jetfuel…digging into this
 

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Same size for every tire or were there different sizes going on?
So, I was really having a hard time finding the 225/35/17 so I got 225/45/17 and all the dash lights went on again and no speedo. I tried to talk to Mercedes service to see the max size I could put on without an issue and they were unable to tell me. Do you think a 225/40/17 would work? There wasn't an issue when I put a different size in the front. The front now has 195/45/16.
 

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…the difference between the two … installed and USA Brabus specs …in circumference is 3” … rotating 440 less revolutions per mile … 1” larger diameter …and here’s where the computer can get confused with the spedo error at almost 3 mph higher than actual speed...

jetfuel…digging into this
So what would work as far as a size close. I am trying to find a 225/40/17. The original one was a 225/35/17. Does this have to do with being the same size with the front or just the rear and a maximum size there? Thank you!
 

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Use this...

Tire Size Comparison | Comparison of tires and wheels

Put in the size you are supposed to have in order to keep the stock vehicle happy... (the key there is circumference)
Then experiment with width and diameters that match the factory spec... (wider but not taller, or taller but not wider, etc...)
At least keep the circumference in the same ratio front to rear... that's where the computer is getting confused.
Then go try to find the tire you select in the marketplace.

Good luck

Jim
 

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Hi thanks for chiming in! The front tires are 195/45/16 and the rear are 225/35/17. The problem happened when I put 225/45/17 on the rear.
There's your problem. The computers depend on all tires having an equal diameter for everything to work smoothly.

Your rear tires are a full two inches taller than the fronts, so the computers are receiving two very different inputs for wheel speed.

You can put pretty huge tires on a smart and have everything work, you just have to make sure that your tire sizes equal out to the same diameter.

Go back to 225/35/17 and you should be fine. :) You could also play around with tire sizes, just run them through this calculator to make sure that they come out to about the same diameter.

 
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