hi all

i have a 02 WRX with standard alloys currently wrapped in 215/45/17 rubber.

managed to get a cheap set of 225/45/17 rubber.

a:- will the rubber fit the alloys?

b:- togather, will it fit under my arches?

thanks

 

you will have no problems with those tyres, i have the same on mine, WRX blobeye with WR1 wheels and the 225 width rubber on

although im sure you will be aware that your rolling diameter is now ever so slightly bigger so your speedo will be EVEN MORE inacurate lol


john

 

isnt the 225 part the width of the tyre? so why will this effect the rolling diameter?

 

because the 45 bit in the tyre size is the profile.

that means the wall depth is 45% of 215mm

therefore 45% of 225mm is going to be larger, thus, making the rolling diameter bigger


john

 

thanks, i understand

 

You learn something new every day.
I thought the 45, 50 etc bit meant the profile was 45mm, 50mm etc.
Didn't realise it was a percentage of the width.
Scooby net is useful

 

i hope im right on that lol


john

 

Yes, your correct.
It's the percentage of the width.

Handy site here for working out bigger alloys / tyres.
http://www.miata.net/garage/tirecalcold.html


David

 

haha wicked site

Tire Size Comparison

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
215/45-17 3.8in 12.3in 24.6in 77.3in 819 0.0%
225/45-17 4.0in 12.5in 25.0in 78.5in 808 1.4%

 

does this mean in a 30mph zone with 30 on the gage am i going faster or slower than 30mph?

 

Your tyres are bigger, therefore for each revolution you travel further, so your speedo will under-read. However your speedo is designed to over-read by +10% to -0% so it will balance the 1.4% difference.

In normal use your treads will reduce from 7mm to 2mm i.e. 5mm. The difference between 225x45% and 215 is 4.5mm, virtually the same.

ATEOTD you will not notice any difference.

 

looking at the tyres, they looks considerably fat!!!!!

the rims it is going on are 7*17

 

how do you mean under read, when im doing 30mph GPS, on the clock im reading about 36mph....


sorry if av totally got that wrong, its been a long hot day


john

 

well???

 

@EVOLUTION: the tyre change alone will cause the speedo to under-read. This is balanced by the fact that they are designed to over-read as you have seen compared to GPS (true speed).