Hello, if this already covered I am sorry but I could not find.

I am thinking to get 215/45 R17 tires once I get my new rims (TD pro race 1.2). I wonder how many miles off with 215/45 R17? the stock tires usually 3 miles off as you know.

 

If the stock tire reads 63 mph at 60 mph actual speed, a 215/45/17 will read 62.1 mph.

 

Thank you much

 

I have been running this combination (215/45 on 17x17 TD PR1.2) for three years now on four different tires. Love the set up. I have no idea what the precise impact is on speedo numbers versus stock and could care less. New tires versus worn tires... under inflated versus over inflated... 205/45 versus 215/45... Whatever. Just so long as the rubber is sticky, I am happy.

 

Wow, that is one wide rim. What's he offset?

 

Typos are so funny.

 

Here is a nice tire size calculator that will tell you how off one tire size is from another in all dimensions including speed reading. http://www.miata.net/garage/tirecalc.html

 

Why not 215/40-17? It would offer better gearing compared to a 45 series tire.

 

It will offer shorter gearing.

 

40 vs. 45 ... 40 is good for acceleration... worse for highway mileage... and less comfortable ride...

Oh yeah... and my speedo is more accurate with 215/45R17...

But lots of guys run 15" wheels with medium-profile tires on the track - to get the benefits of lighter weight and shorter gearing.

 

Thank you all replies.

And what about tire pressure? both front and rear 36 should be good enough?

 

I am running 32 front and rear on my 215 45 17s, no issues at all

 

I run 36F, 35R with good results. Optimum pressures will vary based on which tire, loading, suspension setup, driving style, and preferences for grip vs. mileage vs. tire wear.