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Dave B

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Yea, I would have thought there was no problem with the strut. OTOH, what about the outside and the fender lip?



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Tev42

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I bought 18x9 +35 with 245/40 tires. I do feel a noticeable amount of sidewall flex if I get feisty in the corners. I bent three stock wheels in under 5k miles so I had to downsize.

18" wheels with meatier tires and a lower offset do impact the handling, but the car is still wicked fun. The decreased offset and thicker tire is more visually appealing to me for sure. Hopefully my wheel insurance will actually pull through when I put the stock wheels on for summer but who knows.
 

J o n

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The question, how do you recalibrate the speedometer once larger wheels are put on?
Tire diameter is all that matters. OEM tire diameter is 25.8". Whatever wheel size is inside of that is irrelevant
 

DiamondPuma

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Tire diameter is all that matters. OEM tire diameter is 25.8". Whatever wheel size is inside of that is irrelevant
Let's assume that the tire thickness/height remains the same, increasing the wheel size will increase the tire size. Which then becomes an issue for your speedometer. So, how does one recalibrate a speedometer for 10th gen Civics?
 
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tinyman392

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Let's assume that the tire thickness remains the same, increasing the wheel size will increase the tire size. Which then becomes an issue for your speedometer. So, how does one recalibrate a speedometer for 10th gen Civics?
You wouldn't use the same tire sickness if you reduced the diameter of the rim, you'd opt for a thicker tire. There currently is no way to recalibrate the speedometer for the gen X Civics.
 

DiamondPuma

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You wouldn't use the same tire sickness if you reduced the diameter of the rim, you'd opt for a thicker tire. There currently is no way to recalibrate the speedometer for the gen X Civics.
What are you even saying? Thanks for the reply on the speedometer. However, if you increase the diameter of the wheel, the diameter of the tire increases too. Tire thickness is the same across brands unless you are getting a different type of tire e.g. off-road, all-season, performance, etc. The thickness will then vary. Let's put it this way if the wheel diameter increases, the tire diameter will increase when using the same type of tire. With a larger wheel, and the same tire type the, circumference of the tire has increased, which is what ultimately will throw off the speedometer.
 

tinyman392

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What are you even saying? Thanks for the reply on the speedometer. However, if you increase the diameter of the wheel, the diameter of the tire increases too. Tire thickness is the same across brands unless you are getting a different type of tire e.g. off-road, all-season, performance, etc. The thickness will then vary. Let's put it this way if the wheel diameter increases, the tire diameter will increase when using the same type of tire. With a larger wheel, and the same tire type the, circumference of the tire has increased, which is what ultimately will throw off the speedometer.
If you increase the diameter of the rim, you decrease the thickness of the sidewall and thus keep a somewhat equal overall wheel diameter. Keep in mind you're in a Type R forum, no CTR owner in their right mind would increase the diameter of the rim. If you decrease the diameter of the rim, you increase the thickness of the sidewall for the same effect.

Edit1: For reference: a 245/40/18 tire has approximately the same diameter as a 245/35/19 which as the same diameter as a 245/30/20. If you were to theoretically up the diameter of the CTR rim to 21" you'd want to do a 245/25/21 tire, though after that it would not be possible to get a rim (>22") that could support the stock 25.8" diameter tire.

Edit2: The latter three examples (19, 20, and 21") above all have equal overall diameters of 25.8" while the 18" rim would have a 0.1" difference in diameter (or about 0.4% = 1.004x).
 

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Use this tool for a visual and understanding of tire and wheel specifications.

https://www.rimsntires.com/specspro.jsp

Put oem specs on left. Desired specs on right. It will show the comparisons and tell you the various differences

The numbers 245/30/20 mean... 245mm width, 40% of width for sidewall height, and 20" rim diameter
 

DiamondPuma

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If you increase the diameter of the rim, you decrease the thickness of the sidewall and thus keep a somewhat equal overall wheel diameter. Keep in mind you're in a Type R forum, no CTR owner in their right mind would increase the diameter of the rim. If you decrease the diameter of the rim, you increase the thickness of the sidewall for the same effect.

Edit1: For reference: a 245/40/18 tire has approximately the same diameter as a 245/35/19 which as the same diameter as a 245/30/20. If you were to theoretically up the diameter of the CTR rim to 21" you'd want to do a 245/25/21 tire, though after that it would not be possible to get a rim (>22") that could support the stock 25.8" diameter tire.

Edit2: The latter three examples (19, 20, and 21") above all have equal overall diameters of 25.8" while the 18" rim would have a 0.1" difference in diameter (or about 0.4% = 1.004x).
I understand now. So the sidewall thickness decreases when the diameter of the wheel increases even when the type of tire remains the same? This is so the circumference of the overall wheel, and tire assembly stays constant- correct? Are there no situations when the sidewall thickness remains the same, even with an increased diameter? I was operating under the premise that sidewall thickness was constant for the type of tire (e.g., 16" wheel has a Summer tire with 16" diameter, 4" sidewall and an 18" wheel has a Summer tire with an 18" diameter, 4" sidewall). I understand this to now be incorrect. Obviously, a large tire would have to increase the sidewall for structural integrity and uniformity past a certain point (what's the largest performance tire that any brand makes?)

Thanks for the clarification and candor in your corrections! :D
 

tinyman392

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I understand now. So the sidewall thickness decreases when the diameter of the wheel increases even when the type of tire remains the same? This is so the circumference of the overall wheel, and tire assembly stays constant- correct? Are there no situations when the sidewall thickness remains the same, even with an increased diameter? I was operating under the premise that sidewall thickness was constant for the type of tire (e.g., 16" wheel has a Summer tire with 16" diameter, 4" sidewall and an 18" wheel has a Summer tire with an 18" diameter, 4" sidewall). I understand this to now be incorrect. Obviously, a large tire would have to increase the sidewall for structural integrity and uniformity past a certain point (what's the largest performance tire that any brand makes?)

Thanks for the clarification and candor in your corrections! :D
Tirewall thicknesses vary. You can compute it off of the tire size which is defined by three numbers: width, aspect ratio, rim diameter. So a 245/40/18 tire is designed for an 18” rim that is 245mm wide. The tirewall thickness is = width * aspect ratio / 100.

Different types of tires come in a variety of sizes, though those sizes may depend on what type of tire it is. For example, the 245/40/18 has a 3.9” tire wall. You’ll be hard pressed to find an off-road tire with this thickness, but all season tires and performance summer tires should be easy to find in this size. The stock 245/30/20 that the Type R comes with has very few all season tires available for it, a small selection of winter tires, and a large selection of summer tires.
 








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