Another tyre/wheel question

[Anonymous]

I've just put 03 wheels on an 01 car, as the rear tyres are now 16s will this effect the speedo.. Apologies if this is a dumb question but it's my profession

[Ernie Ball]

If the speedo measures off the rear wheels, it will be affected unless you can get the rolling radius of the wheel/tyre combination to be exactly the same.  If you are planning on putting 205s or 215s on the back, this won't be possible since there will always be some difference.  The closest you can get on 16" wheels is 225/40/16s, which will lead to a speedometer reading only 0.1% too slow (which I'm sure is within the speedo's margin of error).

But maybe it doesn't matter: maybe the speedo reads off the front wheels?

Here's a handy tyre size calculator:

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

[kanujunkie]

here you go Bowman, works out all you'll need for ya

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

[Darth Paul]

My speedo is about 3mph out with 17"s on the car. So when I'm doing an indicated 30mph, it's really only 27mph. Great for town driving!  s:lol: :lol: s:lol:

[heathstimpson]

My speedo is about 3mph out with 17"s on the car. So when I'm doing an indicated 30mph, it's really only 27mph. Great for town driving!  s:lol: :lol: s:lol:

And better that way round for the speed cameras  s:wink: :wink: s:wink:

[Darth Paul]

My speedo is about 3mph out with 17"s on the car. So when I'm doing an indicated 30mph, it's really only 27mph. Great for town driving!  s:lol: :lol: s:lol:

And better that way round for the speed cameras  s:wink: :wink: s:wink:

Indeed.  s8) s8)

[roger]

My speedo is about 3mph out with 17"s on the car. So when I'm doing an indicated 30mph, it's really only 27mph. Great for town driving!  s:lol: :lol: s:lol:

And better that way round for the speed cameras  s:wink: :wink: s:wink:

My speedo is out by 3mph "standard", and I still got done doing 35   s:cry: :cry: s:cry:  which makes me think I was done

[heathstimpson]

My speedo is about 3mph out with 17"s on the car. So when I'm doing an indicated 30mph, it's really only 27mph. Great for town driving!  s:lol: :lol: s:lol:

And better that way round for the speed cameras  s:wink: :wink: s:wink:

My speedo is out by 3mph "standard", and I still got done doing 35   s:cry: :cry: s:cry:  which makes me think I was done

Must have been as that would have been 32mph, well below the normal error allowance given  s:? :? s:?