[Lyds_corsa_b]

Hi guys,
I found this link that works out how much a different size wheel can affect your speedometer. I thought it may be of use to you lot who are getting alloys. You don't want an inaccurate speedometer - speed cameras might get you!

You have to put in your original tyre size, then input the new tyre size that you're going to fit. It's handy if you're going to get low profiles like I have. It tells you the percentage of how much your speedometer will be affected.

http://www.miata.net/garage/tirecalc.html

Hope this helps. Lyd

 

[Darko]

Brilliant. Thanks! Im about 5 miles off my speedo with my 15".

 

[Lyds_corsa_b]

I'm about 1.5% off my speedo

 

[Matt]

hmm im not so sure

 

[GSi mark]

cool i have a-3.7% difference on my 195/45-15 toyo's

if i put 195/50-15 then it become's 0.3% which is almost bang on to factory stats so fuel and performace should be as stated by vx woop woop

 

[Deathscythe]

just out of interest, does anyone have the size of the stock wheels and tyres? my car didnt come with them so im in the dark here.

 

[jim610]

it recons mines -3.7% iv got 195/45 15

 

[LAD VXL]

My speedo is out by 6.2% with my 17's which means when my speedo reads 60mph i'm actually doing 63.7mph

 

[Clutch]

just out of interest, does anyone have the size of the stock wheels and tyres? my car didnt come with them so im in the dark here.

165/70/13
well thats what mine are on anyway (1.2)

 

[jim610]

165/70/13
well thats what mine are on anyway (1.2)

just tryed that size mines -0.8% an iv got 195-45 15

 

[Jonny]

it recons mines -3.7% iv got 195/45 15

exactly the same as mine and mine are 16's

 

[corsasi]

with my 205/50/15s it says when im doin 60 im actually doin 62.7

but when i get my 195/45/15s on its only 0.8% out, and its the safe side so it says im goin faster than i am, wich means less chance of speeding by accident haha.

 

[gregwalters]

mines 3.8% i got 215/35-17"

 

[Lee]

Will sticky this. Thanks Lyds.

 

[andy88]

woo mine are 0.3 on my 195/50/15

 

[corsa-tom89]

jsut out of intrest does anyone know if you have to take your inner arches out

old wheels 165/70/13
new wheels 215/35/16

thanks this will help me decided if i can get the alloys i want or not hehe

 

[CorsaBoySuty]

surely it wont make your speedo inaccurate will it?

just smaller wheels faster excelleration

bigger wheels, higher top speed??

i mean i just got a 7.3% difference, surely this cant be right with 185/55 15's on?

 

[Sam]

surely it wont make your speedo inaccurate will it?

just smaller wheels faster excelleration

bigger wheels, higher top speed??

i mean i just got a 7.3% difference, surely this cant be right with 185/55 15's on?

Of course it's right, it's mathematically proven!

 

[CorsaBoySuty]

sowhen i do 60mph im actually doing 67.3 mph?

or am i thinking of this all wrong?

 

[Sam]

sowhen i do 60mph im actually doing 67.3 mph?

or am i thinking of this all wrong?

Yes, the speedo is set to give an accurate representation of the speed your wheels are going - so if you change the size of the wheels it's no longer accurate.