I recently got a speeding ticket the officer said i was doin 85 in a 65, according to my speedometer i was doin about 70-73, I got a 00 honda civic si w/ 215/45-17's, there huge tires(they fill my wells) a big difference from the low profiles i used to have untill i cracked a rim on a pothole, anyways, does anyone khow the MPH difference between them and my stocks? He asked me about calibration, I'm a chic what the heck is that?

 

what size were the stocks?

 

im pretty sure they were 15's

 

My calculations is that your current overall tire diameter is 24.6 inches. Your factory installed tires for a 2000 Civic SI were195/55-15. That diameter would be about 23.4. That is a huge difference. You've gone from 811 revolutions per mile to 886 revolutions per mile. That is a 0.092 or 9.2 % increase in speed. I guess that would be your calibration factor but you should be more worried about your gear rations.

Keep you 17" rims and switch to 204/40-17 tires. They are almost exactly the same diameter as your original factory tires - actually 23.45 inches. You won't even notice the difference on you spedometer.

 

Typed a little too quickly. You went from 886 RPM (factorytires) to 811 RPM (currenttires). Also meant "gear ratios" not "rations". The rest is OK.

Except you were probably driving about75 mph when you got the ticket or your spedometer is offor the cop was on crack.

 

suggest you take your car to a shop that has a dyno, to do a actual tire spin up and speed check, or a speed-0-meter shop, they will do the proper adjustment to the meter to give you the most accurate reading. This way you can keep what you already have on the car.i don't know the cost. This will give you your speed from 0-100 mph or km, with a certificate of check, avoiding a ticket unless you do speed, and you are certified by the shop.

 

u seems realy good at calculating revolutions , i have a 16" tyres factoy recomend 13 " , wat u suggest ?

thanks

 

wish someone would of told me that when i got the tires, my car was stolen before i got to get it checked. so i had to fight a ticket, pay a 220. fine, eat 4 pointsand retake my drivers test for a car i don't have anymore. that sucks!!

 

ravinsen,

Regarding 16" to 13" tires. Those figures are only thesize of your rims.

You need to knowthe height of your tires to get your overall diameter.

Let's say your tires are 204/40-17 tires. For tire height multiply 204 millimeters by 0.40which gives you 81.6 mm which you divide by 25.4 to get 3.2 inches above and below your rims. So you add 2 x 3.2 inches plus 17 inches = 23.4 inches diameter.

Take You can find out the RPM by compairing similar diameter tires on www.tirerack.com

Anyways,tire size is more about handling and look. I don't think it has any bearing on power output as your torque will remain constant.

 

I was debating putting 17z on my civic but im worried about the reading what would the difference be my car is 2001 civic dx.