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  #1  
Old 03-02-2002, 03:56 PM
AAL
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Speed Ratings

Is it really important to stick with the MB recommended speed rating for tires? My car calls for an H rating. I think I'd have more choice and of course be able to get less expensive tires in a T or even an S rating. I don't drive over 100 mph. The H rating is up to 130, and I think the T is 118 and the S 112.

I know with my Jaguar, which is a very heavy car, it calls for V rated tires, and it definately is more stable with V tires. It had H rated tires on it when I got it, and although the ride was very comfortable, it was "wallowy."

I now have Michelin MXV energy plus on the Jaguar, and they're great. The MB has Michelin MXV, and they seem fine, but I don't have anything else to compare them to as far as experience on the car.

Some of the Yokahama tires get good reviews, and I'd consider these.

The MB tires are 205/70/14, and there isn't a lot of choice in H tires in this size.

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  #2  
Old 03-02-2002, 05:59 PM
Registered Diesel Burner
 
Join Date: Aug 2001
Location: Northern Virginia
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Just out of curiosity, what model and year is your car?

I've just gone through the same thing in buying tires. Its true that Mercedes specifies an H-rated tire for my 1987 300D. Like you, I don't need a tire rated for 130 mph. I'm not that stupid.

You will note that the available tires that are H-rated are typically about TWICE as expensive as the average T-rated tire. Thus the push to sell them. Also, the H-rated tires never have the equivalent warranty mileage rating, because they are a different rubber compound. So they want you to pay twice as much for a tire that's going to last half as long. Nice scam!

I deal with this relatively easily, because I never let them have the car. When I need new tires, I take the wheels off the car (either two at a time or all four in the back of the pickup). They tend to back down easier if they don't have to show on the sales form the type of vehicle.

If I were going to take in the vehicle, I still would not accept H-rated tires. They start out by telling you "Mercedes requires H-rated tires and that's what we have to install - its company policy." But they never tell you what "H-rated" means, thinking you will accept this without question. So I just calmly said "Well, I don't drive 130 mph, and I can get by with something like a T-rated tire." It's fun to watch their face fall when you tell them that.

So, I have little problem when taking in loose wheels. And if I took them the vehicle and they gave me any problem, I'd turn around and walk away. They need to sell you tires, so I think they will sell you what you request if you insist.

After all, they have absolutely no problem selling you a SIZE tire that is not specifically recommended by the manufacturer!

Ken300D
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  #3  
Old 03-02-2002, 06:14 PM
AAL
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I have a 73 450 sl. I don't really think of it a sports car, but rather some type of tourer. I'd rather have a good ride than high performance tires, and at the original 70 series size , I don't really think any tire could be considered high performance.
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  #4  
Old 03-02-2002, 06:53 PM
AAL
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Related to my previous messages, isn't there any difference between what was an H rated tire in 1973, almost 30 years ago, and an H rated tire today? I mean, haven't tires improved considerably? If an H rated tire was recommended 30 years ago, wouldn't a T rated tire today be equal or superior to a 30 year old design?
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  #5  
Old 03-02-2002, 07:09 PM
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Join Date: Aug 2001
Location: Northern Virginia
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I see what you're saying. I guess it depends on whether you're talking about Firestone tires. (Had a few jokes with the tire salesmen at the expense of Firestone today, as a matter of fact.)

There is nothing wrong in my opinion with running T-rated tires on your car or mine as long as we keep the speed down below 110 or so. Not a problem for me.

I did notice that the H-rated tires have an "A" temperature rating, and the T-rated tires were "B". Not that big of a deal in Virginia. And we're talking about Michelins, by the way. The wear rating on the Weatherwise was 480, which is pretty good.

I just do regular driving to commute to work.

Ken300D
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  #6  
Old 03-03-2002, 03:36 AM
tidawg
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Don't forget the other side of the coin. Putting a lower rated tire on your car, ie H to T and you just added 20 to 30 feet to your stopping distance. Speed rated tires not only have speed ratings but braking coefficents that need to be addressed. Abs brake systems are very sensitive to this.
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  #7  
Old 03-03-2002, 10:52 AM
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Join Date: Aug 2001
Location: Northern Virginia
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When you say the braking distance has increased 20 to 30 feet, at what speed are you referring to? 130 mph or 60 mph?

I can see how the different rubber compounds would make a difference in stopping power. I'm not able to understand how there would be any change in the operation of the ABS, since its function is to modulate the hydraulic pressure just enough to avoid locking the wheels. It might have to operate sooner with a harder rubber tire, but it should not malfunction.

It's a very good point you make, and I don't think I've ever seen the proper test data for braking. Are these braking coefficient ratings for tires available? I know there is a test for tread wear, temperature and traction. Is the braking coefficient tied up in the traction test? If so the T-rated Michelin Weatherwise is an "A". True, with only three possible results, A, B, or C, there is a lot of variation within one category.

Thanks,

Ken300D
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  #8  
Old 03-03-2002, 08:31 PM
Fimum Fit
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Speed ratings cover two important factors

One is the tire's ability to resist centrifugal force, which is clearly a speed issue, primarily, but the other is resistance to heat -- heat build up and consequent tire disintegration can happen when you have all your grandchildren and a ton of luggage in the car at 65 mph, too, especially in southern climates, or if someone doesn't notice a low tire pressure in time. Personally, I would never have less than an HR tire on my vehicles, even my old Datsun pick-up.
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  #9  
Old 03-04-2002, 09:42 AM
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Join Date: Jan 2002
Posts: 3,126
My car was originally specified with Z-rated tires (195/65ZR-15).

Any opinions out there as to how "low" one should go on the speed rating issue? For example, should I consider H-rated, S or T rated?

If MB designs a car with a specific tire rating, what is a good compromise between tire wear, stability and cost?

Any thoughts?
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  #10  
Old 03-04-2002, 02:34 PM
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Location: St. Albert, Alberta, Canada
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Go with the best tire you can afford. And if you decide to buy an S or T speed rated tire, buy the best in that category.

I often drive my car hard at highway speeds, and wouldn't put less than an H on it. I appreciate the stiffer sidewalls and am willing to give up a little tire life.

My wife used to think I was crazy. Then one summer we drove through the Mojave (sp?) desert. Lots of cars were on the roadside with tire problems. My Z-rated tires took the heat and speed in stride.

If you subject your car to less extreme conditions than some of us, drop to a lower speed rating. One thing to remember :LOAD RATINGS are very important. Ignore them at your peril.

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