Tire Load Question - PeachParts Mercedes-Benz Forum

gmercoleza · #1 09-29-2006, 11:12 AM

This is also posted in Wheels & Tires.

I just put a set of 195/75R14 tires on my 85 380SE, which weighs 3,685 according to: http://home.hiwaay.net/~gbf/mbmodels.html. Tire pressures recommended on the door jamb sticker are 30/34.

Looking at the tires, the sidewall lists maximum load limit of 1400 and maximum pressure of 35. Am I okay? Do they even make a car that weighs 1400? Geo Metro perhaps?

lkchris · #2 09-29-2006, 11:40 AM

1400 per wheel, i.e. 5600 lb car.

BTW, 195/75 is an incorrect size for your car.

Should be 195/70.

195/75 indicates an American car P-metric tire, unsuitable for anything European.

gmercoleza · #3 09-29-2006, 11:44 AM

Quote:

Originally Posted by lkchris

1400 per wheel, i.e. 5600 lb car.

BTW, 195/75 is an incorrect size for your car.

Should be 195/70.

195/75 indicates an American car P-metric tire, unsuitable for anything European.

Thanks for the info, that makes more sense than a 1400 lb. car.

Yes, I am aware that the correct size designated for my car is 205/70R14 (that's what was on there before). Can you tell me exactly what would make a 195/75R14 tire "unsuitable" for a European car other than the fact that it is 10mm narrower?

t walgamuth · #4 09-30-2006, 05:15 AM

i dont think it will cause problems. but it wont provide ideal grip i dont think.

the slight size increase will make your speedo read slower than you are going. i havent done the math but i estimate roughly 3 to 5 mph so you will need to be vigilant to avoid speeding tickets.

tom w

deanyel · #5 09-30-2006, 10:36 AM

There's less than 1 percent difference in diameter so well less than 1 mph difference on the speedometer.

lkchris · #6 09-30-2006, 12:21 PM

P-metric tires have no reliable speed rating.

Your Merc will go faster than they will.

gmercoleza · #7 09-30-2006, 12:27 PM

Just went back and returned the tires for the original size 205/70R14 - discount tire allowed me full credit and I went with the Kumho 758s which I have on my 300E and absolutely love. World of difference - I'll never make that mistake again!

gmercoleza · #8 09-30-2006, 12:28 PM

Just went back and returned the tires for the original size 205/70R14 - discount tire allowed me full credit and I went with the Kumho 758s which I have on my 300E and absolutely love. World of difference - I'll never make that mistake again!

raymr · #9 09-30-2006, 02:22 PM

I have the 758s too. Good tire for the buck, but I'm a little concerned about wet/snow traction. The back tires spin pretty easy, even in a little bit of rain.

t walgamuth · #10 09-30-2006, 02:39 PM

the distance traveled per rotation is what needs to be compared. and that is pi times the diameter so take the diameter of the original equipment and the diameter of the oversized multiply out and divide to find the differnce in percentage

tom w.

gmercoleza · #11 09-30-2006, 07:22 PM

Quote:

Originally Posted by raymr

I have the 758s too. Good tire for the buck, but I'm a little concerned about wet/snow traction. The back tires spin pretty easy, even in a little bit of rain.

Not a problem for me at all here in TX. My hometown of Chicago was another story. My wife on a couple occasions managed to pull a 360 in the 560SEL without even trying...

deanyel · #12 10-01-2006, 10:14 AM

Quote:

Originally Posted by t walgamuth

the distance traveled per rotation is what needs to be compared. and that is pi times the diameter so take the diameter of the original equipment and the diameter of the oversized multiply out and divide to find the differnce in percentage

tom w.

The percentage difference remains constant whether you are measuring the diameter or the circumference because of the fixed relationship between diameter and circumference.

raymr · #13 10-11-2007, 06:25 PM

Well its about a year later and the front Kumho just blew out with less than 10K miles. The tires weren't quite to the wear bars but are pretty worn down. The inner edge was through the cords. Similar rapid wear happened on our other car with these tires, which I originally blamed on my son's agressive driving style. They also have bad flat spots when cold. Verdict: these tires are junk.

Now the problem is that it's almost impossible to find 205/70-H14s anywhere. TireTack only sells winter or summer tires in those sizes.

t walgamuth · #14 10-11-2007, 09:51 PM

Quote:

Originally Posted by deanyel

There's less than 1 percent difference in diameter so well less than 1 mph difference on the speedometer.

diameter difference times pi is the amount it will be off. 3% if your statement about the diameter is correct. the circumference is the amount traveled on one revolution.

ok lets see....if one tire is 100 cm and another is 101 that is one percent larger, right? so the 100 cm tire runs 314.16 in one revolution. the 101 cm tire will turn 317.3016 or about three cm more or about 1% more.

You are right....but is the tire really only one percent taller?

Tom W

Tomguy · #15 10-11-2007, 10:34 PM

Keep in mind, higher speed rated tires usually wear a lot faster.

I've got Firestones on my 300s right now (pretty heavy cars) and their wet traction is lousy (I'm being generous here). A small amount of standing water makes you feel like you've gone SURFIN USA. But they handle great in the dry. The wear looks ok, I've got about 7k on my silver 300 so far and there's about 70% tread left.