Larger tyres and speedo differences

[Wozza244]

There is prob a thread on here about this but i cant find it, does anyone have a table or formula of how much your speedo goes out per inch bigger your tyres are, for example i hav 35's and 37's but the speedo was right when it had 31's on it if ya get wat i mean.
Cheers

[hilux79]

Have emailed you one.
Don't know how to post it up here as it is a Excel program

[ISUZUROVER]

It is quite simple.

Just work out the circumference of your existing tyre: Diameter x PI So for a 31" tyre it would be 31*3.14 = 97.4 (33" = 103.7 and 35" = 110).

work out the % increase. e.g. 31" to 33" = (103.7 - 97.4) / 97.4 *100 = 6.5%

31-35 is 13%

So if your speedo is 100% accurate with 31's, you would be doing 113 km/h on 35's when your speeds is on 100.

[dklyne454]

That's all good........ as long as your tire is the size that is indicated. there is a lot of variance in stated size, and actual size.

Best bet,
Wrap a tape around your tyre to get the circumfrence and a more accurate measure.

as isuzurover said.

Circ / pi = diameter.

2760mm / 3.14 = 878.98 (mm x 0.39 = inches eg. 878.98 x .39 = 34.28 inches)

Now work out your difference between the 2 tires





or

borrow a GPS and get an accurate reading of what your new tires are at.

[Tomo_89]

Get a mate who has standard tyres and an accurate speedo and have him drive at 100km/h and just follow him and see what your speedo reads.. to get a rough idea just how much bigger your tires are. say 10% and add 10% to your speed and thats what you will be doing. ie 100 = 110

hope this helps
Tomo

[frp88]

when I had my 29' and went to 33 it has gone up 10km/h spot on.

[love ke70]

10kph at 50?
or 10 kph at 100?
percentages work so much better than a kph difference

id go off what the tyre says it is, theyre gonna be a little smaller than they state normally, so then u drive just under the limits.
keeps you safe

[kruzen84]

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

this should help ... as a guide only i would think.

[frp88]

10kph at 50?
or 10 kph at 100?
percentages work so much better than a kph difference

id go off what the tyre says it is, theyre gonna be a little smaller than they state normally, so then u drive just under the limits.
keeps you safe

the diffrence is constance it is 10 kph

[Wooders]

10kph at 50?
or 10 kph at 100?
percentages work so much better than a kph difference

id go off what the tyre says it is, theyre gonna be a little smaller than they state normally, so then u drive just under the limits.
keeps you safe

the diffrence is constance it is 10 kph

So when you are parked the Jeep is still doing 10km/h
Percentage is the right way to measure it.

[blackmav]

http://www.thelongranger.com.au/longran ... tools.html

[ISUZUROVER]

10kph at 50?
or 10 kph at 100?
percentages work so much better than a kph difference

id go off what the tyre says it is, theyre gonna be a little smaller than they state normally, so then u drive just under the limits.
keeps you safe

the diffrence is constance it is 10 kph

So when you are parked the Jeep is still doing 10km/h
Percentage is the right way to measure it.

Indeed - a constant 10kph difference is unpossible. I call BS.