2012 merc amg

One of my biggest complaints on my 2019 E450 luxury wagon has been it's ride quality over broken up pavement and not so great roads when I travel. If you look at the stock profile of the tires the area of rubber between the road and the rim is very narrow indeed. This is mainly because of the middle number on the stock tire size designation. By going from a 40 profile which is stock to a 45 profile would give the tire a little extra of a taller profile off the road and would therefore improve the quality of the ride. Getting rid of the stock run flats of course would improve the quality of the ride also by making the sidewall less stiff. I'm gonna need tires in the not too far future and am thinking about making these two changes, getting rid of the runflats and going with the 245-45-19 profile. I know it will slightly throw off the speedometer readings but I would think that would be about it, it is not that major of a change. I notice the new 2021 all terrain wagons use this slightly higher 245-45-19 profile tire and just looking at the wheels tells me there would not be as much of chance of bent rims (been there done that 4 times with my car) and the ride would improve. Anyone tried this? I want to investigate this more before I just go ahead and do it.

ua549

The 245/45R19 tire has a 1" larger diameter. You would have same sidewall height improvement with less of a speedo error with 235/45R19 tires.

Sidewall Height - Diameter (Change)
245/40R19 = 3.9" - 26.7" (0.00%)
235/45R19 = 4.3" - 27.3" (+2.2%)
245/45R19 = 4.3" - 27.7 (+3.7%)

2012 merc amg

Might be worth a try. The ride on my wagon is not very good. I know going non run flat alone though should really help out. Maybe thats the way to go and keep the stock size incase there was a warrantee issue in the driveline. Seems like when cars are still under warrantee best off keeping everything by the book.

ua549

I went with non-RFT on my E300 with 245/45R18 tires. There was a significant improvement in ride quality.

threeMBs

The sidewall hight is not exactly correct:
Sidewall Height - Diameter (Change)
245/40R19 = 3.86" - 26.72" (0.00%)
235/45R19 = 4.16" - 27.32" (+2.2%)
245/45R19 = 4.34" - 27.68 (+3.6%)

So assuming 245/45-19 fits "regular" E (other than all terrain variant), it would suit OP's requirements better.

2012 merc amg

So looks like about an inch taller or 3.6 percent meaning that it would throw off the speedometer accuracy only around a couple of miles per hour. Sidewall is about 1/2 inch taller, I'll bet the car would ride better.

nycebo

Great idea to do so. The 2 mph issue is irrelevant compared to the importance of ride comfort. Let us know how it goes if you switch.

MWmp5

Would this also apply to an e300? I currently have the AMG 19" wheels.

ua549

The sidewall heights came directly from a Continental tire site. The extra hundredth of an inch precision is immaterial considering tire wear. That said if your measurement source is accurate and Continental is wrong, then I agree with you that 18/100" makes a difference.

2012 merc amg

I won't be making this change anytime soon as I still have enough life on my run flats for another 6K miles or so and the amount I drive the car is not all that much. It is something to think about doing though as find this car to have a very choppy sports car type of ride and really surprised that Mercedes opted to go with the 40 series on such a car. It would be a slight trade off in that the car would not handle quite as well with the 45 series but I'm sure would ride better and does not seem like there is a clearance issue. My only worry is if there were a drivetrain Warrantee issue could Mercedes say you were driving the car with the incorrect tire sizes. Being that all 4 tires were the same OD though this should not put extra strain on the drive, it's only when you put different size tires on the front vs back where you could run into a issue.

threeMBs

The sidewall hight of 235/45 and 245/45 tires are not identical. Period. The source of your "info" is irrelevant, because they are not the same for all other tires in these sizes. One Conti tire that you say their site says are the same (mathematically impossible as 45% of 245mm can never equal to 45% of 235mm) and built the whole "concept" around it. Full stop. No need to go any further.

Frank Rizzo

On my 2009 CLK 550, I changed the rears from the factory 255/50 to to 265/50 (needed extra traction) and I noticed when driving aggressively thru corners - the traction control lamp would flash like crazy, so the car noticed the small difference in diameter. Most "normal" type drivers would never even notice.

2012 merc amg

Interesting, thats what I'm nervous about some unexpected thing happening in making a change like this. I guess I'll let somebody else be the Guinia pig

threeMBs

255/50 to 265/50 on CLK?

Gordp

The same issue with ride comfort, I installed a set of 245/45/19 non-run-flat and the ride improved dramatically. The clearance is fine, no rub on any of the tight turns.

2012 merc amg

Very tempting to do. Do you notice very much speedometer error after the change? Any other effects. I can imagine the ride is much better. I still do worry about what the dealer might say about the warranty should something go wrong with the drive train. I still have another 3 years left on a extended Benz warranty.

Gordp

The speedo error is minimal and not noticeable. I think I saw the calculation by another contributor in this post of 1 or 2%. No other issues so far, other than a much smoother, quieter ride. I purchased the extended warranty and I am not worried. I understand if you change the front / rear side wall heights you can mess up the computer, but with this change it is consistent all round.

2012 merc amg

What kind of tires did you go with? I was thinking about pirelli cinturato p7 non run flats. I got 46k miles out of them on my pickup truck. The 45s vs 40s would probably help with less likelihood of getting rim damage too for those up north with pothole ridden roads.

The G Man

I test drove 2 E300 with 18” and 19” runflats on AMG rim and notice very minimal difference in comfort or handling. Runflat tires have very stiff sidewall, stiff enough to support thousands of pounds of weight. That is the source of the bumpy ride and the tire noise not so much that extra 0.5 inch on the sidewall. Maybe If we are comparing 17” to 19” conventional tires, then there is a noticeable difference in ride comfort and tire noise. I ended up with the 19” AMG rims because It was the better looking of the two.

Gordp

I am north and needed a winter tire. Went with a Michelin Xice 245 45 19. Took off a Goodyear Eagle Sport AS 245 40 19 Runflat. I am running the 19" AMG Rim.