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Tire pressure is a function of speed and weight of the car, so there isn't a single correct tire pressure. The faster you plan to drive or the more stuff you load into the car the higher the tire pressure needs to be to cope with the deflection and not overheat the tires. To that end there are several tire pressures depending on the vehicle. MBs usually have a sticker inside of the fuel door with all of them listed by tire, speed and load of the car. In the USA the driver door sticker only lists the highest recommended pressure. That's known as the max load pressure. It's for when you want to drive near the top speed with the car loaded to its gross weight. This goes back to the Firestone incidents in the 90s. The highest recommended pressure is the safest, but you pay by having a less comfortable ride. For most of your driving by yourself or with 1 or 2 passengers and a mostly empty trunk you wanna use what's known as the normal load pressure. Don't know what the sticker looks like in your case, but yours won't have as many options. As an example here's the one from my C63S coupe, with several different pressures depending on tires, load and speeds, and below that a different one from I believe a GLC with less options, but a note to increase the pressure by 4 psi for speeds over 100 mph.
Last edited by superswiss; 04-03-2022 at 12:47 PM.
I follow the recs posted on the inside of the fuel flap and my tires have worn very well. I generally add a pound or two to compensate for the inevitable gradual loss of pressure so I don't have to check the tires every week (the reading available on the dash is also helpful). BTW, I swapped our the RFTs that came with the car for a set of Michelin Pilot Sport 4S tires — using the same pressure recs, the car's ride and handling are much improved.
2019 E 450, 2016 E350 4matic (retired), 2018 Ford Edge Sport, 2008 Porsche Boxster
Originally Posted by The_Judge
I follow the recs posted on the inside of the fuel flap and my tires have worn very well. I generally add a pound or two to compensate for the inevitable gradual loss of pressure so I don't have to check the tires every week (the reading available on the dash is also helpful). BTW, I swapped our the RFTs that came with the car for a set of Michelin Pilot Sport 4S tires — using the same pressure recs, the car's ride and handling are much improved.
+1
I use the tire pressure for normal load, on the fuel flap, plus 2 psi. At 25,000 miles on my Pirelli Centurato P7 RF, I still have 7/32 of tire tread left and anticipate 40,000 miles before replacement. No problem with either quality of ride or handling.
BTW, out of curiosity, you mentioned that your ride improved going from RF to non RF: Is your set up 19" wheels?
2019 E 450, 2016 E350 4matic (retired), 2018 Ford Edge Sport, 2008 Porsche Boxster
Originally Posted by The_Judge
Yes, the car came with 19" AMG 5 Twin Spoke Wheels.
When you said the ride improved I thought so: those of us who have the standard 18" wheels do not have the same problems: the 18" wheels with tires that have a larger sidewall, ride better and the 18" wheels are not as prone to pothole damage as the 19" wheels. I think the trade off going to 19" with slightly better handling, but poorer ride and extra cost, is, for me, not worth it. I am old school: form follows function. I also find the 18" stock wheels on my E450 good looking.
I test drove the E300 with both 18” wheels and 19” wheel and did not notice much difference in ride quality or handling. The runflat’s stiff sidewall is the cause of the rough ride, not the thinner sidewalls. With that said, I run my tires at 35 psi but if I were to changing to non-runflat, I would run them higher at 37 psi or so to protect the rims due to the softer sidewalls.
2019 E 450, 2016 E350 4matic (retired), 2018 Ford Edge Sport, 2008 Porsche Boxster
Originally Posted by The G Man
I test drove the E300 with both 18” wheels and 19” wheel and did not notice much difference in ride quality or handling. The runflat’s stiff sidewall is the cause of the rough ride, not the thinner sidewalls. With that said, I run my tires at 35 psi but if I were to changing to non-runflat, I would run them higher at 37 psi or so to protect the rims due to the softer sidewalls.
There are numerous threads on changing from RF to non RF because of ride quality.
When you dive into the complaints, not all (nothing is 100% except my wife who is never wrong!) but nearly all who complain have non stock 19" wheels.
IMO, it is the narrower sidewall of the tires on the larger wheels, not the stiffness of the RF that is causing the complaints.
As I have 18" RF, I run my tires at 35 psi - which is 2 more than the recommendation (for normal driving) of 33 psi. I have tried 37 which would be +4 over the recommendation: there was a noticeable, i.e., negative, degradation in the ride.
There are numerous threads on changing from RF to non RF because of ride quality.
When you dive into the complaints, not all (nothing is 100% except my wife who is never wrong!) but nearly all who complain have non stock 19" wheels.
IMO, it is the narrower sidewall of the tires on the larger wheels, not the stiffness of the RF that is causing the complaints.
As I have 18" RF, I run my tires at 35 psi - which is 2 more than the recommendation (for normal driving) of 33 psi. I have tried 37 which would be +4 over the recommendation: there was a noticeable, i.e., negative, degradation in the ride.
Just my $.02.
From my experience, a conventional tire’s aspect ratio affects the ride quality a lot more than a runflat tire’s aspect ratio. A higher profile runflat does not ride all that well compare to low profile runflats, both having poor ride quality. I have been an early adaptor to runflat with a few of my BMW in the late 2000s, believe me when I said, runflat tires has gotten a lot better. The first gen runflat rides like a rock and gets damage a lot more easily and more often. Conventional tires have a build in air suspension, it will always ride more comfortable than any similar size runflat.
FYI the tire pressure listed on the tire is always the MAXIMUM Pressure Allowed by tire manufacturer.
You should not run your tires at this pressure as there is no need and a real harsh ride.
Max tire pressure is used to calculate tire load capacity based on Car Manufacturers recommended tire pressure.
(Actual Tire Pressure / MAX PSI) * MAX TIRE LOAD CAPACITY / = Tire load capacity as load capacity s pretty much direct ratio to tire pressure.
Auto/truck manufactures have to make sure the tire can handle the GVWR & GAWR (Gross Vehicle Weight Rating and Gross Axle Weight rating)
Run Flats are a bit different but they use same formula.
This load capacity is important and I hope those that change tire/wheel size take into account else you get some blow outs.
FYI the tire pressure listed on the tire is always the MAXIMUM Pressure Allowed by tire manufacturer.
You should not run your tires at this pressure as there is no need and a real harsh ride.
Agreed. But, one should not ignore the max pressure molded on the tire either.
I just replaced the OEM tires on my wife's car with new Yokohama YK740 all-season tires. Nothing special about these tires, except the sidewall MAX pressure is 51psi. The tire store inflated them to 32psi, which made the tires look all but FLAT.
I bumped the pressure to 42 psi -- printed nowhere on the car's gas flap, etc. -- and they now look and run normally. Yet another example of reading the tire sidewall MAX pressure and subtracting 10-15% to arrive at proper inflation for normal loads.
Car manufacturers have no earthly idea what tires you will place on their cars. Tire manufacturers know the tires they build and the pressures they need.
2019 E 450, 2016 E350 4matic (retired), 2018 Ford Edge Sport, 2008 Porsche Boxster
Originally Posted by DFWdude
Agreed. But, one should not ignore the max pressure molded on the tire either.
I just replaced the OEM tires on my wife's car with new Yokohama YK740 all-season tires. Nothing special about these tires, except the sidewall MAX pressure is 51psi. The tire store inflated them to 32psi, which made the tires look all but FLAT.
I bumped the pressure to 42 psi -- printed nowhere on the car's gas flap, etc. -- and they now look and run normally. Yet another example of reading the tire sidewall MAX pressure and subtracting 10-15% to arrive at proper inflation for normal loads.
Car manufacturers have no earthly idea what tires you will place on their cars. Tire manufacturers know the tires they build and the pressures they need.
I do not agree with your premise: Car manufacturers work with tire manufacturers to achieve a combination of fuel economy, mileage, handling and comfort. Anyone can disregard those findings and put whatever pressure they want in their tires.
When in doubt, I tend to rely on the highly paid engineers at Mercedes who are charged with finding the best combination of mileage, comfort, handling and economy: I will continue to use as a guide the recommendations on the fuel filler cap of my Mercedes.
I do not agree with your premise: Car manufacturers work with tire manufacturers to achieve a combination of fuel economy, mileage, handling and comfort. Anyone can disregard those findings and put whatever pressure they want in their tires.
LOL. Keep on drinking that cool-aid. The only way in which Car manufacturers and Tire manufacturers work together is to agree on a contracted delivery price of trainloads (millions) of tires. German car manufacturers "prefer" European tires only because they are made in Europe and therefore, the supply chain is shorter resulting in much cheaper transportation costs. Same reason why Japanese and Korean cars come with Oriental tires, and the same reason why American cars are delivered with US made tires.
When a car manufacturer buys tires by the millions, "fuel economy, handling and comfort" are minor considerations, if at all.
I just replaced the OEM tires on my wife's car with new Yokohama YK740 all-season tires. Nothing special about these tires, except the sidewall MAX pressure is 51psi. The tire store inflated them to 32psi, which made the tires look all but FLAT.
I bumped the pressure to 42 psi -- printed nowhere on the car's gas flap, etc. -- and they now look and run normally. Yet another example of reading the tire sidewall MAX pressure and subtracting 10-15% to arrive at proper inflation for normal loads.
Car manufacturers have no earthly idea what tires you will place on their cars. Tire manufacturers know the tires they build and the pressures they need.
You are incorrect. From Yokohama’s website:
Tire pressure should be checked at least once a month when the tire is cold and set to the manufacturer’s recommendation.
Yawn... Just more marketing pablum. Inflating my new 51psi (MAX) Yokos to the car's recommended pressure of 28-32psi only ensures Yokohama can sell more tires when they wear out sooner. It's their business to sell more tires.
My C320 (purchased new) came with OEM Pirelli P6s (52 MAX psi). I ran them at the gas flap recommended 32psi until they quickly demonstrated extreme inner/outer shoulder wear (zip in the center tread). I pumped them to 44psi and the wear evened out.
Check the W203 forum... Pirelli P6s were notorious as 12-18,000 mile tires.
Agreed. But, one should not ignore the max pressure molded on the tire either.
I just replaced the OEM tires on my wife's car with new Yokohama YK740 all-season tires. Nothing special about these tires, except the sidewall MAX pressure is 51psi. The tire store inflated them to 32psi, which made the tires look all but FLAT.
I bumped the pressure to 42 psi -- printed nowhere on the car's gas flap, etc. -- and they now look and run normally. Yet another example of reading the tire sidewall MAX pressure and subtracting 10-15% to arrive at proper inflation for normal loads.
Car manufacturers have no earthly idea what tires you will place on their cars. Tire manufacturers know the tires they build and the pressures they need.
Not only does car manufacturers do not know what tires you will put on, tire manufacturers also do not know what car their tires are going to be install on. 42 psi seem awfully high, even for conventional tires, unless you are tracking your car or routinely do over a 100 mph.
Yawn... Just more marketing pablum. Inflating my new 51psi (MAX) Yokos to the car's recommended pressure of 28-32psi only ensures Yokohama can sell more tires when they wear out sooner. It's their business to sell more tires.
After the Ford/Firestone debacle that resulted in hundreds of deaths and cost the two companies many billions of dollars, both manufacturers of vehicles and tires take pressures very seriously. Of course you will do what you want, but it is dangerous to incorrectly state publicly that manufacturer recommended tire pressures are driven by marketing and should be ignored. I'm done here.
A couple of videos for those who think OEM tires are just marketing. Admittedly, this is for the performance variants, but there are real differences between OEM and non-OEM tires. Although, in more econo box cars, the OEM designation is mostly about guaranteed availability of the tires, rather than a OEM specific tuning. This is not to say a non-OE tire can't perform the same or even better, especially a newer generation tire.
A couple of videos for those who think OEM tires are just marketing. Admittedly, this is for the performance variants, but there are real differences between OEM and non-OEM tires. Although, in more econo box cars, the OEM designation is mostly about guaranteed availability of the tires, rather than a OEM specific tuning. This is not to say a non-OE tire can't perform the same or even better, especially a newer generation tire.
For the purposes of this thread in an E-Class sedan forum, we are not discussing specialty tires, but rather... those wonderful Run-Flat tires that everyone loves to tears, the tires that Mercedes buys by the traincar load for fitment at the factory on all its latest sedans, regardless whether C, E, S, etc. No "tuning" the car to the tire, or vice-versa. Whatever fits at the lowest cost to MB is what is supplied... the same tire you will find on "lesser" cars throughout Europe and the States, etc. Nothing remotely "special" for MB.
Further, MB has been using Run-flat tires on it's W213 for several years now. Has anyone been asked in a MB survey or otherwise whether they like these tires? Of course not. MB has several warehouses stacked to the rafters with these tires, and they will be thrown on these cars til they run out of them.
Be aware that Mercedes-Benz cars do NOT have Continental OEM tires worldwide. Out of the Mercedes-Benz Assembly plant in Indonesia, the sedans are fitted with Michelin tires... because Michelin manufactures those tires in Indonesia, Thailand and China. MB will NOT pay to ship Contis from Europe, half-way around the world to the Orient. Bottom line... Tires by the carload at the lowest bidder delivered price.
my 2015 e400 came with normal tires and a space saver spare.
Law is run flats or normal tires
W/ normals they are also required to have a SPARE or can of tire fox a flat or compressor (these last 2 make no sense if you get a nail in your tire while out at the beach.)
For tire pressure I try to do the chalk test - grab grand baby's sidewalk chalk - draw line across tread - drive car until chalk line leaves mark behind on driveway.
If even - pressure fine.
IF light in middle - add air.
IF light on edges remove air.
for the RFT, go by the gas cap.. i did 33 front and 39 rear... the car is better to drive and makes slightly lower road noise / bump noise.. someone else posted at length regarding this.
04-03-2022, 12:21 PM
