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I have a 2002 Hyundai Elantra, which ordinarily comes with P195/60R15 87H tires. What are the pros and cons of changing these tires to a set of P185/65R15 86T? Some sites say they're compatible, but not all do, and while I understand the benefits of lower profile tires, there's not much talk on higher profile ones.

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Not very on topic, so I post as comment: In general compatible sizes pros is that certain sizes are more common/cheaper than others. –  Krom Stern Apr 11 '12 at 13:44

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up vote 6 down vote accepted

Caveat: all of the following information is heavily dependent on the tire construction, tread pattern, application, etc. If you care more about a particular application, you should research that specifically:

A higher profile tire will potentially affect the following factors:

  1. Comfort: increased - you've increased the vertical air space in the tire, allowing the tire to adapt to small bumps pneumatically before they hit the suspension.

  2. Handling: decreased - a taller, less stiff sidewall will generally reduce turn-in ability and responsiveness (i.e., in back-to-back comparison, you'll notice a distinct lag between turning the wheel and seeing the car turn).

  3. Deep snow performance: increased - a tall thin tire is better able to dig down into a deep pile of snow than a wider shorter tire.

  4. Speedometer reading: different - the rolling circumference between the two tires will almost certainly be different.

Regarding that last point: there are plenty of rolling circumference calculators on the web. I plugged your numbers into this one and it thinks that the difference at the highest level would be 20 millimeters of circumference. The calculator estimates that there would be a difference of about 1 kph (i.e., too small for most people to observe on a standard speedometer).

Now, considering your specific example, Tire Rack does list both of these sizes as valid choices for winter tires. Its default search does not show that size but that may be more of an assessment of their customer base than a judgment.

Using all of the above, if this was my vehicle where I live (i.e., I buy all-weather tires since deep snow is rare), I would not go with a taller tire. There are plenty of tire vendors, brands and applications available for me to select a stock size tire without sacrificing our mutual criteria (comfort for her and handling for me).

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1 KPH isn't a big deal for the speedometer, I'm not so sure about the odometer. Ideally, the powertrain controller would be updated with the new tire size. If that's not an option, document the heck out of it, so you can calculate the true mileage on the car. –  Mark Johnson Apr 11 '12 at 16:11
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@MarkJohnson, in the US, it's almost certainly illegal to do anything that might affect the odometer (so updating the computer to show a different number is off limits). 1 KPH is in the realm of errors that can be introduced due to under/over inflation or tire wear (i.e., not really a cause for concern). –  Bob Cross Apr 11 '12 at 18:08
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Nowadays the speedometer and odometer are fed by the PCM, which is correcting the signal from the transmission based on the tire circumference and gear ratios the vehicle left the factory with. I guess you're right about the error from tire inflation/wear being comparable to 1 KPH. Still, if it was my vehicle, I'd fix the PCM, or at least keep the paperwork in a safe location to document the change. I don't know of any vehicles where you can edit the current odometer reading by screwing with the PCM. You can change the rate at which miles go on, but you can't take the old ones off. –  Mark Johnson Apr 11 '12 at 22:12
    
Thanks @BobCross! I've decided it's worthwhile to stick with the original-size tires. Like you, I don't deal with much snow, and while I "only" drive an Elantra, I do appreciate good handling. :-) –  Melissa Avery-Weir Apr 12 '12 at 12:50

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