Questions: Load index and speed ratings?

[B15SE]

I did some searching, and I found most of my answer on the speed rating, but can't find anything on the load index questions I have.

My Civic's OEM tires are shot and I'm looking at new tires. They are a 205/55-16 89H. Most of the tires in this size that I'm looking at are 205/55-16 91H or 205/55-16 89V.

From what I found searching the web, going from a H to a V will make my ride more stiff, which I don't want. But if I stay with a H and go to a load index of 91, will I increase the "stiffness" of my ride? Would the 91H and the 89V pretty much be a wash (ride the same)?

I'm looking at touring tires. I don't want anything that is high performance. I want the MPG and smooth ride more than anything (I want to fully exploit the 40MPG numbers out of my Civic). My 89H tires I have now take corners just fine for my suspension setup.

If anyone have any recommendations in this size, please let me know. I'm still a few 1,000 miles before I change tires (unless we get more ice/sleet here in DFW

).

Thanks for the help,
Brian

 

[bdcardinal]

you will not notice a difference from 89h and 91h. the difference is too small to notice.

 

[B15SE]

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you will not notice a difference from 89h and 91h. the difference is too small to notice.

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Thanks. That is what I wanted to hear!

Brian

 

[alreadygone]

Agree with BDC. There will be more difference between different brands than any atributable to ratings. Picking a brand is the crapshoot.

Bob

 

[GC4lunch]

Quote:

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I did some searching, and I found most of my answer on the speed rating, but can't find anything on the load index questions I have.

My Civic's OEM tires are shot and I'm looking at new tires. They are a 205/55-16 89H. Most of the tires in this size that I'm looking at are 205/55-16 91H or 205/55-16 89V.

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Are the shot tires the original tires on the car? What does your owner's manual say about recommended tires?

Quote:

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From what I found searching the web, going from a H to a V will make my ride more stiff, which I don't want. But if I stay with a H and go to a load index of 91, will I increase the "stiffness" of my ride? Would the 91H and the 89V pretty much be a wash (ride the same)?

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You have been reading the wrong parts of the Web.

The speed ratings and the load ratings are only remotely related to ride stiffness.

The load rating is an essential safety specification, and is related to the recommended inflation pressure of your tires. You shoud always fit a tire with a load rating at least as high as the car manufacturer's load rating. (Fitting a higher one cannot hurt; fitting a lower one is dangerous.) Also, you should always inflate your tires to at least the pressure recommended by the car manufacturer if the tires have the same load rating. If the tires have a load rating greater than the car manufacturer's recommended load rating, then you may safely use a lower pressure (no more than 3psi per load rating number) for a better ride -- but a lower inflation pressure will also adversely affect gas mileage.

The speed rating indicates the maximum speed at which the tires may be driven over a sustained period under ideal road conditions when the tires are in brand-new condition. It is kind of like a "reverse" guarantee: drive at higher speeds for a sustained time, and the tires are more or less guaranteed to blow up due to heat build-up. (The sidewall flexes on each rotation of the tire -- extended at the top of the tire, and "flat" where the tread is flattened by the road surface -- and that flex causes internal friction in the tire carcass.) The nominal speed rating is the best the tire can do; the "real" speed rating (the speed at which the tire will blow up) actually decreases as the tire ages and the road surface gets hotter; it is wise to have a safety margin there, as well.

As for your concerns for a better ride and good mileage, one strategy you might consider is going to a narrower tire with the same overall diameter. A 185/60R16 tire will have essentially the same diameter as your 205/55R16 tires (so your gearing and speedometer and odometer readings would stay the same), but will likely feel softer through the steering wheel and through the seat of your pants at the same inflation pressure as your 205/55R16's. The narrower tire also would present less wind resistance, and would have the same effect on improving gas mileage as not driving with the windows rolled down. Incidentally, going to a narrower tire at the same inflation pressure will not decrease the size of the contact patch where the tire and the pavement interact; it will change only the shape of the contact patch.

Also, if you add about three pounds pressure (to either the 205/55R16 or the 185/60R16), you will improve mileage, but at some cost to your smooth ride.

 

[Quattro Pete]

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A 185/60R16 tire will have essentially the same diameter

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If only someone made a tire in this size.

 

[B15SE]

Thanks for all the help.

I guess you can't believe everything you read on the internet

. That is one of the reasons I asked here. I just had a lot of confusion about the speed ratings/load index vs. ride quality. There are just so many more tires available in this size with a 91H rating. I guess this is because this size is popular with German cars, and they all spec the 91 load index.

I'm happy with the 205's, so I will stay with those. I'm getting good mileage now and anything thinner would look kind of funny.

Thanks for setting me straight. I now know more than I did before.

Brian