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I currently have 205/55 R16 91V M+S Goodridge tires and an '06 Honda Civic Coupe. Should I stick with the same type of tires for go for something else? What's the difference between getting R16 or R17? Does it really matter? I realize I don't want anything above R19 on my car because it's going to be too low, but 15,16, or 17? Why would I want any of those sizes? Also, should I change the tires myself or take it somewhere so that they can be aligned etc?

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3 Answers

up vote 5 down vote accepted

As pointed out by DXM, the 15,16,17 isn't an interchangeable number.

None of the first 3 numbers can just be changed individually.

With your 205/55R16 example:
205 is the width of the tire in millimeters 55 is the percentage of the width that equals the height of the sidewall (so 205 x .55 = 112.75mm)
16 is the wheel diameter in inches the tire fits on

One wheel can hold a range of widths, so you might be able to go from 205 to 225 to run a wider tire (more rubber on the road, creates a larger contact patch and so theoretically more traction) but you would need to reduce the sidewall percentage to 50 to keep the height of the sidewall close to the same (112.75mm vs 112.5mm).

If you do not keep the overall diameter of your tire the same (wheel diameter + sidewall height) you will be altering your final gear ratio which will make your speedometer incorrect, alter your fuel mileage (better or worse depends on driving behavior and altered size), impacts your acceleration, what speed you can reach in which gears, your effective power band, etc.

Again using the 205/55R16 your current overall diameter is 519.15mm (wheel size * 25.4 + tire width * sidewall percentage)

To move to a 17" wheel assuming the same wheel and tire width, you'd need to use a 205/45R17 to get close but you'd actually be 4.9mm taller (off by about 1%). Fitting a 215/40R17 would get you 1.35mm shorter (off by about .25%).

Going with a wider tire and especially a wider wheel you have to take more into account as you may have clearance issues and either need wheels with a different offset or make use of wheel spacers.

There is rarely a perfect match when changing the wheel size but the more you can reduce the variance, the less you will impact items on the car that you shouldn't be changing unless you understand why you are changing them.

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The choice depends on what you are trying to achieve with new tires and what's important to you. handling? ride comfort? looks?

These are the reasons people buy higher size rims:

  1. Since you want wheel diameter to stay the same, higher rim size, means tire side wall is thinner. This improves cornering as there's less flex in the tire. At the same time, ride becomes a little stiffer with thinner side wall. Not good for certain places like Detroit (at least last time I was there)
  2. Larger rim allows you to use larger brakes. Important for racing as larger rotor will be better at dealing with heat generated by braking
  3. Looks. Some think larger rims look better and to a degree that's true. However, this can be taken to an extreme and becomes tacky and stupid looking. Also, personally, I think large rims with dinky little stock brakes (i.e. large empty space inside the rim) don't look any good either.

You do realize that if you go to larger diameter, you'll need new rims as well. So staying at the same diameter could save you few hundred bucks.

As far as specific advice for your make/model, check out honda online forums and see what people are using in their cars. Just stay away from clowns who wouldn't recognize decent taste if it hit them in the face. 17" will probably be good on your car. I wouldn't go higher.

If you buy higher-size tires, you'll need new rims. If you buy tires/rims in one place like tirerack.com or discounttiredirect.com, they will mount the tires for free and ship you wheels which are ready to go onto your car. If you buy tires separately, you will need to have a professional shop mount them on your rims.

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As alluded to with the "Detroit" comment, particularly low-profile tires like 35 series can easily be damaged by holes in the road. Replacing your own tires is unlikely to be something you can do on your own unless you own specialized mounting and balancing equipment and a high volume air compressor. Though I have heard of people who have done it themselves, my local shop charges $20 or $40 to do it and I can't imagine it being worth it to do at home, particularly without the equipment. –  Sean Reifschneider May 31 '11 at 8:05
    
The low profile isn't just a risk to the tire, but the wheel itself. With less rubber between the road and the metal wheel, if you hit a good size pot hole at speed, you will bend your rim and have to replace it. –  ManiacZX Jun 2 '11 at 0:15
    
Primary reason for a larger rotor (mechanically at least, not aesthetically) is for stronger braking force. The rotor acts as a lever, the larger it is the more stopping power you have from the same sized caliper. At the same time, you also often increase the caliper size and/or number of pistons, creating more clamping strength onto the rotor. –  ManiacZX Jun 2 '11 at 0:17
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"Primary reason...is for stronger braking force"- On most cars you can easily lock up your wheels with stock brakes if you press the pedal hard enough. If that's the case, what would be the point of stronger force? Actual primary reason is that when you race, you need to be able to just get to lock-up point (but never cross it) over a considerable duration of time and this is where heat becomes your enemy and larger rotors help a lot. Same thing with pistons (I can lock up my 4500 lbs SUV with 1-piston calipers), more pistons is about spreading the load so brakes last longer, not force –  DXM Jun 8 '11 at 18:19
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Also have a look at:

Benefits of low profile tires

There is a performance / comfort tradeoff which can be decided depending on the usage. On a track lower profile is often better, but on the road not so much.

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