Speedos are cable driven from the rotation of the wheels so if its a bigger wheel then the wheel will rotate less to go the same speed as a small wheel, so surely a speedo would read low?????

With 17s you wont actually be going faster than the speedo reads, well, maybe +1/2% or something.

Speedo's read slow as standard.

With the first calculator thing i'm 0.1% out

thats not bad. That means when doing 60MPH on the Speedo I am doing 60MPH

[Edited on 24-03-2003 by J 11ESY]

try this site ;)

http://www.paspeedo.com/calculator.htm

There is another site, that measures the speed the vehicle is travelling at, and the speed it says on the speedo is below that of what the car actually does when over 70mph....my friends 205 gti was doing 90 and i overtook him, and mine read 85!!!

quote:

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Originally posted by DanielJ
still no luck, mine seems 2 b 10 mile an hour slower, its on 50mph an it only feels 40

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How the fuk do u get it sorted out? do u av 2 get it on the dyno? how much is it gona cost? fuk dis, i aint flashed again.

I've tested mine using a GPS system which is as expensive and as accurate as u can get. I posted this up before, but basically:

my 1.2 8v on 16"s with 195/45 tyres

50mph on clock = 48mph

60 mph on clock = 57mph

70mph on clock = 65mph

draw ur own conclusions. Oh and thats with a mechanical speedo cable dash.

Matt

shunt alter anything it calculates from the axle brace not wheel

You can put what you want on here in uk,as long as each axle has the same size tyre on,and the front tyres must be the same size as the rear or narrower.
Dave

Well...are you allowed to change the tyre size that much from original??? In Denmark we are NOT allowed to change the wheel size (diameter of whell...alloy and tyres) more than plus/minus 5 percentage from the original wheel size.

still no luck, mine seems 2 b 10 mile an hour slower, its on 50mph an it only feels 40

quote:

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Originally posted by CorsaGSI_DK
Come on guys!!!

It is simple geometric calculations! If you can't calculate the size of your wheel yourself then try this ---> http://www.miata.net/garage/tirecalc.html

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of course tyre size matters!!
different profiles will give a different circumference!
eg a 60 profile tyre will have a greater rolling circuference than a 50 profile tyre.
thus the speedo reading will be out.
Dave

Come on guys!!!

It is simple geometric calculations! If you can't calculate the size of your wheel yourself then try this ---> http://www.miata.net/garage/tirecalc.html

wtf? tyre size wudnt matter

Depends how much rubber you have on them doesnt it!

i no but we both got 17s an both got corsas

there was a web link put on here a while ago that calculated the difference that different size wheels made. do a search for it!

having someone drive next to you is not likely to be very helpful as most speedos are inaccurate!

ai will do :lol: im gonna get me m8 2 drive along next 2 me on weekend i think

I was dead next to my mate and he was in his brand new standard fiesta.

he was doing 70mph and i was sitting at 68mph so cant be that much out.

Wait and see what the millions say.

as above cos i think me speedo is 10mph out