Hi I have a 2010 Mercedes e class rwd. It hasn’t been stock in years but I’ve been running 255/35/19 front and 275/35/19 rear. I recently went to 235/40/19 front and 285/35/19 rear. I love the ride so much better but I think it gave me a few weird shifts or maybe I imagined it. I was wondering if this is a large enough size to mess up the transmission of the car if I continue to drive with this setup. The wheel widths are 8.5 front and 9.5 rear if that helps.
yeah, changing tire sizes like that can mess with your transmission’s shift points. it’s best to stick with the manufacturer’s recommended sizes to avoid potential issues.
No, as long as they’re the same size on both sides of the axle you aren’t going to have transmission problems with a larger tire.
You should go down on aspect ratio if you go up in width however, as going to 285/35 from 275/35 will increase overall diameter of the tire and your speedometer will be slightly less accurate.
Your transmission might be shifting weird because you’ve been beating on it.
Check the transmission fluid, look and see if mkultra supports your TCU (doesn’t look like it), depending on the year and transmission there’s an issue where transmission fluid will start wicking up the transmission electronics connector and get into the TCU and cause issues there.
Did you ever do a re-learn via xentry/das/whatever after changing the rear size?
This only started once I put the larger tires on and it is very minimal. I’d probably be the only one to notice because I drive the car daily. The trans itself is pretty well maintained. I recently did a service on it. I have not done a relearn on it however is that required? I didn’t do it any of the other times I went up in size.