Am upgrading from stock tires to Bridgestone RE730's at 225 45 17?????

 

I just put 225/45-17 Sumitomo HTR+ on. I haven't noticed much difference. I would say maybe 3-4 mph+ difference. I.E. Your speedo says 50mph but your actually only going 46-47 mph. It's not a dramatic difference.

 

I've got that size tire. According to the online tire size calculators, the speedo will be 1.9% fast. 70 MPH on the speedo will actually be 68.7

 

stock tire RPM = 819

your new tire RPM = 827

thats a discrepancy if 18 revs per mile

that means every 45 miles, your car will have an extra mile on the odometer than it should have...

if you keep these tires for 25,000 miles, you your odometer will actually rack up at least an additional 556 miles....(your odometer will have changed by 25,556)

this does not take into account the fact that the tires will wear down so your additional mileage will be closer to 600

you will lose 600 miles off of your warranty

your speedometer will be off by 2.26%

that means when you are traveling at 75 mph, your speedo will show 76.695 mph.

 

those online tire size calculators are OK but in order to be truely accurate (as i have in my previous post) you need to get the exact specs of each tire as the overall size of tires varies between manufacturers even if the tires are listed as the same size...they may not be.

i.e. a bridgestone 225/45/17 is not the same size as a toyo 225/45/17

 

so not much hahaha. The car goes bye bye in 1.5 years anyway and I only have 21k on it now. I am not worried about reaching my warranty limit. So far my average mileage is 900 a month and this is my only car. So I am going to rip the hell out of these new beauties

 

Ya, I used some of those calculators. And they came up with completely different #'s then the specifications from the manufacturer.

 

ok, I was curious... To make this even more confusing, Bridgestone lists the RPM for the RE730 at 837 (same as my tire), not the 827 you mentioned. Stock is 819. That means the speedo will be 2.15% faster than actual speed (comparison with new tires). 70 MPH on the speedo is actually 68.5 MPH. So the 68.7 MPH I originally mentioned was completely wrong.

Another thing about the shorter tire is that it will increase the final drive ratio by a small margin. The RPMs will spin up a bit faster on launch theoretically improving acceleration by miniscule margin. Probably nothing measurable though...

 

Just remember, the wider the tire, the more horsepower it takes to turn it. But they sure look sweet.

 

Here ya go bro! Jus enter in your info and yoru are set!
http://www.miata.net/garage/tirecalc.html

 

this is a circular thread That's the site (or one similar to) where I got the numbers that I included in my first post in this thread :P