Had my first commute in tropical downpour out of NYC, last night.
REMEMBER the Ratio of the width of the tires compared to the weight of the car.I have 20 inch Contis on my Range rover SC...they are 2 inches narrower each tire. The RR weighs about 1000 lbs. more.There is no hydroplaneing at safe speeds in that car.
The Ml63 however is a 5000lb. car with WAAAY more footprint...so the formula is the wider the tire the more apt to walking ontop of water than cutting through it, and with less weight, Fogetaboutit!.
Everyone knows that feeling of 60mph in the left lane in a downpour when the road cannot shed the water fast enough, when you hit ponded water your heart skips quickly....
That was the scenario at 30mph with these tires and what worse is the spray that is sent off goes far and wide but mostly comes back on the windscreen...Its a joke....you have to re adjust your driving habits immediatly in rain....
I would imagine it wont be a better choice on black ice either!
Small price to pay for owning such a beast!!!


Remember the TV commercial for the E55 a few years back, When the MONSTER lived under the hood of that car.....They should bring back that add with the ML now!

What kind of tires do you have on the ML63?

Did you notice this same problem with your Cayenne Turbo? Similar weight and tire size.

Phil

The ML63 comes with 295/40-20" tires...
Thats a footprint on dry pavement.

Actually I ran 18" Blizzacks on the Cayenne t bo,
but the cayenne had summer tires stock and they were a tad narrower.

BTW. I cant find a car wash that these tires can fit through either.

Not complaining just stateing the facts

ML63 at a carwash? Take it to a detailer for a hand wash at least.

I've hit ponded water on the road in my ML430 and it wasn't too pretty. I really thought I was gonna lose it. Not to mention all the water came up on my windshield totally blinding me. My girlfriends aunt has a 2005 ML350 and she complains about it hydroplaning as well. Maybe its not just the ML63.

I have 275/40 R 20's on my Cayenne Turbo and have never had a problem in the rain. Not quite the same size, but real close. Wonder why the difference in rain performance between the two??????? The U.S. spec Cayenne Turbo shows a curb weight of 5192#. The U.S. spec ML63 shows a curb weight of 5093#.

Phil

Good to know...thanks for the warning. I would have thought the all wheel drive might help minimize loss of traction in one wheel? It also makes me feel the need for snow tires all the more.

I was out in the rain last night also. Luckily I did not have the same problem. Thanks for the warning. And I was just thinking the 20s were going to be fine year round.

Did ESP kick in at any time?

Been driving my ml350 in the rain and havnt noticed this problem at all. Intresting tho.

Narrower tires?

Yes 255.

Great. I just came back from the dealer telling him that I will probably take the ML63 that I orginally ordered and now this. Florida downpours aren't pretty but my 2001 3/4 ton XL in 4wd always had no problem until 75 mph. It sound like the 4matic is useless in this format. More reason to stick with E55. He was also trying to sell me a CLK63. That interior is a $95K disappointment.

All cars will Hydroplane at a specific speed...The Ml63 tires are almost 2" wider per wheel....All that means in comparison to th Cayenne is that it starts to plane at a lower speed because the pressure per square inch on each tire will not slice through the water, it will float through it..
easiest anology is a step hull on a v bottom boat..the faster you go the more it rises or PLANES.

That extra 2" at each wheel equates to a whole extra 8" wide tire on the car.
Like I said the overall footprint here is in supercar territory.
295/40's are massive

Yes, the 295/40 R 20 (11.61") on your ML63 is wider than the 275/40 R 20 (10.83") on my Cayenne Turbo. But not by as much as you state. The first number on the tire size is the width in millimeters. So, a 295 tire is 20 millimeters wider than a 275 tire. 20 millimeters equals .79 inches (or roughly 3/4").

Plus I have wider tires than that on my 911 (305's) and have never had a problem. So width alone does not necessarily cause hydroplaning. Perhaps MB went for max dry performance tires that don't do well in water.

Phil

Sorry you cannot compare widths in different series...a 295 in 40 series is wider than a 295 in 45 series...and again wider than a 275 in 45 series...the 2nd # is the aspect ratio...so in order to get a 295 in 40 series at the aspect ratio it is much wider than a 275/45...
Just sold my CTT with 20's and I am sure the foot print is much bigger

I Think!!!!


Anyway my CTT just squeezed into the track at the car wash...the ml rides up onto the 2 tubes that guide the wheels...so no auto car wash for the ML.

I don't think that is right. I believe the width is a constant. The second number is the aspect ratio. It means in the case of a 295/40 that the sidewall is 40% of the width of the tire, or in this case 118 millimeters. So, the aspect ratio changes by the width of the tire, but the width of the tire does not change with various aspect ratios. Here is info directly off a tire manufacturers website:

"Tire Width is the width of the tire measured in millimeters from sidewall to sidewall.

Aspect Ratio is the ratio of the height of the tire's cross-section to its width. On our example, 65 means that the height is equal to 65% of the tire's width."

So, your tire is about 3/4" wider than the tire on my Cayenne.

Phil

Sorry , I thought you were talking 45 seriescompared to 40 series, your definition is correct.

Great analogy the boat hull. I've noticed speed boats with the flatter hull tend to ride on top of the water (bumpy ride!), whereas other boats with the V shape hull, cut into the water, and have a smoother ride.

So, I need pointed tires in the rain??????

Phil

When I hit that monster puddle, that yellow triangle was blinking like a Biatch!!! Didn't stop the truck from almost going off the road though.

I have an X5 with 315 rear and 275 fronts and have never had an issue with hydroplaning, and it weighs almost the same as the ml.

I guess driving style has somewhat of a play here...

True, and tire design. Maybe drive a little slower