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Discussion Starter · #1 ·
What is the advantage of going with the 245 vs the 235 for the 20" wheel? I purchased the vehicle (15GLA45) with the 245s and recently came to the realization that they are not the stock size. I have seen/read other posts where people have changed to the 245s but I am curious to know what true advantage this has brought to a daily driver. I do understand the numbers and what they mean so I understand that it is a slightly wider and a taller tire.
Are there any advantages of going back to the 235s at my next tire purchase for a daily driver?
Thanks
 

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Michelin MPS4S need the 245 width to get the OEM diameter. The math doesn't always work when comparing one tire to another.
 

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A little more contact patch area from the 245's taller/wider aspect ratio. That can be an off the line/cornering grip advantage in the dry but a disadvantage in the snow dependent on soft/slush or hard pack.

However substantially wider contact patches can also cause a "railroading" effect in that they more resist changes in maneuverability.

The designer's typically do a good job of considering many such factors in selecting an aspect ratio. Many enthusiasts like the aesthetics of a wider tire and know they'll be compromising performance in certain situations.

However given that this 245/40 vs. 235/40 on a 20" rim is a relatively minimal change in most regards, just go with what you prefer.
 

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Michelin MPS4S need the 245 width to get the OEM diameter. The math doesn't always work when comparing one tire to another.
That’s not right. A MO (Mercedes Original) Continental ContiSportContact 5p in 235/40r20 is the same size as a 235/40r20 Michelin Pilot Sport 4S. I have both tires mounted on OEM rims and here’s some pics… A 245/40 Pilot Sport 4S would be taller than the 235/40 Conti.


Tire Automotive tire Wheel Tread Automotive design


The second pic is my phone level on top of the cardboard.
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Here is a comparison of the two tires. The 235/40 tire is almost a half inch taller as the sidewall is 3-28/32" compared to the 245/40 sidewall of 3-15/32". This could give a little softer ride for a daily driver.
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Are there any advantages of going back to the 235s at my next tire purchase for a daily driver?
Thanks
The main advantage is price. A set of Michelin Pilot Sport 4S (PS4S) in 235/40r20 is about $300 cheaper than a set in 245/40r20.

235/40r20 is the more restricted size though, with really only the MO Continental’s or Michelin PS4S available.


Since yours is ‘just a daily’, I’d just save the $300 and go back to a set of PS4S in 235/40r20 when you have to replace. And if you want flush fitment pick up a set of 15mm H&R spacers with the $300.

Tire Wheel Sky Cloud Vehicle
 

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2018 Gla250/4matic mountain grey option 1 and more
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What is the advantage of going with the 245 vs the 235 for the 20" wheel? I purchased the vehicle (15GLA45) with the 245s and recently came to the realization that they are not the stock size. I have seen/read other posts where people have changed to the 245s but I am curious to know what true advantage this has brought to a daily driver. I do understand the numbers and what they mean so I understand that it is a slightly wider and a taller tire.
Are there any advantages of going back to the 235s at my next tire purchase for a daily driver?
Thanks
The suspension and handling characteristics of any car are designed around the properties of the 235, yes a 245 will handle a little quicker in turning but you are giving up sidewall height which absorbs impacts and as a result you are more prone to wheel and tire damage I sell tires and auto repair for the last thirty years, and I can get tires somewhat cheaper than the average joe, but I run the factory size and run flats tires, I’m not out racing or anything so I use what the car/truck came with.
 

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Discussion Starter · #8 ·
Appreciate all the inputs. I will probably go with the 235 stock size when the time comes. It will be interesting to see how much of a difference I will notice. I do not like the way the current Bridgestone Potenza RE980as perform in the rain; seem to hydroplane somewhat easily. As AMGowner mentioned, the stock size may be somewhat cheaper as well. Thanks.
 

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Michelin has now the All season 4 in 235/40/20.
The S4 is a summer tire and I am not convinced that it's not a runflat, I thought I saw ZP in the designation.

Anyway, I just got a set of the Michelins A/S 4, they're not installed yet.
The thread width is .5 inch larger than the Continentals and they have a bumper around the edge of the rim.
Tire rack seems to give these better ratings than the Continentals even in dry weather.
They're 1 lb heavier than the Contis
 

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Discussion Starter · #10 ·
Michelin has now the All season 4 in 235/40/20.
The S4 is a summer tire and I am not convinced that it's not a runflat, I thought I saw ZP in the designation.

Anyway, I just got a set of the Michelins A/S 4, they're not installed yet.
The thread width is .5 inch larger than the Continentals and they have a bumper around the edge of the rim.
Tire rack seems to give these better ratings than the Continentals even in dry weather.
They're 1 lb heavier than the Contis
Let us know how the A/S 4s feel once you get them installed, good to know they have a bumper edge for rim protection. From what I see, Tire Rack has them at 26lbs per tire. I am not sure what my version of the Potenza RE980ASs weigh but if they are similar to the current RE980AS+s, then they are around 30lbs per tire. In this instance, going to the stock 235 size with the A/S 4s may net me 4lbs of un-sprung weight per wheel. That's great but may not matter too much for a daily driver.
In regards to the S4, If Tire Rack is correct and the weight is only 24lbs per tire, I highly doubt it is a runflat; would seem to light for the materials required for a runflat.
 

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Appreciate all the inputs. I will probably go with the 235 stock size when the time comes. It will be interesting to see how much of a difference I will notice. I do not like the way the current Bridgestone Potenza RE980as perform in the rain; seem to hydroplane somewhat easily. As AMGowner mentioned, the stock size may be somewhat cheaper as well. Thanks.
Just a comment, my Bridgestone Potenza RE71R's perform flawlessly in the rain, at least out here in CA. If there is grip to be had, I have it. That covers every wet scenario short of hydroplaning, which I can't address because I haven't experienced it yet. In the past 3 years in my area of CA we've only had enough rain for us to hydroplane in 1 storm, and we were in the honda.

I don't recommend RE71R's for a "just a daily driver" (mine is a HPDE daily driver), my point is if those RE980's suck in the rain, not to let that influence your opinion of Bridgestone generally in the rain, or even Potenza generally in the rain. It's just an RE980 thing.

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Just a question, do you use your car for anything more than city driving? If not, have you considered a 300+ treadwear run flat all season? you don't need sticky tires to pass/merge dual-motor tesla model3's on the interstate, and for a city-car AMG that's pretty much the primary use of a 355 HP hot hatch.

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edit: just read post #10. Why do you care about weight? (rhetorical question). For a commuter car, comfort and convenience and cost per mile is king. That's high treadwear run-flats. with just enough grip to not slip when you stomp the gas at 0 MPH on a metered freeway onramp. Which in your '15 should give you a 'soft race start' where the RPM jumps to 3k then the clutch gets a soft but not-too-soft dump into 1st. A 300TW tire should handle that with panache and zip you to 60 right quick. The run-flat will ensure you're not stranded when they blow out. The cost will be super high but 300TW ensures you'll get more mileage than the OEM contis, so the value is there. You can shop for tread depth too, some tires are deeper than others, which translates to high mileage before replacement.
 

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Got them installed yesterday.
The look wider on the car than the Continentals.
I just managed to re-torque the lug bolts last night, as the tire mechanic didn't use a torque wrench.
Tonight I will set the pressures and tomorrow, I may begin driving the car.
I looked at the tire rack survey, the A/S4 doesn't concede too much dry weather summer performance even to the S4.

Meanwhile the Conti still have useable thread and will go to ebay, unless someone here is interested for a very modest price.
 

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I'd rather have your wheels at modest price. I got my sights on some Hoosier racing slicks at TW40 and there's no way I'd put them on the car except to drag the wheels to the track and swap wheels before DE session1.

Nice thing about the GLA, we can put the wheels in the hatch and drive to the track, no need for a goofy roof rack like a 911 or wheel trailer like a corvette :)
 

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This morning, 4 inches of snow, not plowed 100% yet, I was able to keep up with the traffic, doing 40 MPH sometimes.
This is my first experience in this car on snow.
I have high standards, coming from a modded WRX, manually lockable center differential, self locking front and rear diffs, driving on DWS tires, good alignment, relaxed in snow..
The AWD of the GLA did ok and the tires did good too, no scary moments.
 

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Four weeks after our 45 finally arrived at the dealer we headed south out of the San Francisco Bay Area to visit family in Southern California. As we approached the Grapevine warning signs were indicating eminent closure. We were detoured east to the Mojave amongst significant traffic. We had the summer performance tires, rated for use only in temperatures above 40F. The snow began as we climbed. The snow got thick. Ice formed under the snow. And as much as I tried I could not get the GLA to spin a tire, let alone fishtail.

We had the same experience in the mountains outside Grenoble France when we encountered chip seal on a narrow wooded path. The car was absolutely stable on the loose stones. Within turns the inside rear brake would gently operate to maintain the steering line. Other than that it was like we were on dry clean pavement.

Then I attended the AMG Driving School (part of the package when you buy the 45). In the afternoon we got time on the skid pad. I then learned exactly what the computers do. I grew up driving on snow and ice. I thought I was good. But the computers ... wow!!!

For ultimate traction, tires matter. But new cars are pretty impressive (at least to this old guy) with any tire.
 

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Was your car on the OEM Continental 5P? On those the GLA45 can drive on ice ? I mean I had thoughts about what happens to a 240 rated “bubble gum” tire on ice, but didn’t think it can grip.
 

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I haven't experienced skidpad in this car. Did you get to drive it with TC on, sport mode, and TC off?

My question is, are the nannies TOTALLY OFF when TC is off? Some cars (370z), even when you turn it off, it's not OFF. Not unless you go in and unhook the vehicle Yaw sensor, only then the system gets disabled.
 
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