Bigger tyres , by how much does it effect speedo accuracy ?

[jay see]

i just downloaded an app for android mobile called SPEEDVIEW . uses GPS for speedometer . I will test it later

I tried this app and its the same as my GPS, so got confirmation that the speedo is out, even though I'm running standard size wheels and tires. Did notice that it has a 1/4 mile time as well. Interesting to see who has the slowest patrol.

[Dales300exc]

Going from 31s to 33s. The speedo reads 94 when im doing 100. So 6%

[BigRAWesty]

Going from 31s to 33s. The speedo reads 94 when im doing 100. So 6%

What did it read with 31's

[93patrol]

With 33s on my gq my speedo is spot on with 1km/h

[Dales300exc]

It read pretty darn close to 100 at 100.

[nissannewby]

It read pretty darn close to 100 at 100.

I have found this is pretty much infinitely variable as every patrol seems to be different. A few examples- my gu was correct with 285/75/16 tyres, my sisters gq is out 5km with 31/10.5/15 tyres and her boyfriends gu was correct with 35/12.5/15s fitted.

[BigRAWesty]

I have found this is pretty much infinitely variable as every patrol seems to be different. A few examples- my gu was correct with 285/75/16 tyres, my sisters gq is out 5km with 31/10.5/15 tyres and her boyfriends gu was correct with 35/12.5/15s fitted.

Same. Mine has come out spot on with 33's and 4.1diffs.. But others are way over.. Or under.
If I ever change to 4.3 diffs it'll revert back to close to 6k under like my 31's were

[doka404]

I went from 31's to 33's on my GQ and the speedo is actually on the money now .. checked with 3 or 4 different GPS's...just to be sure

All depends on how far and which way your speedo is out in the first place..