wheel/tyre size changes- speedo incorrect??

[trekbiker]

I'm currently running 265/30/19 on a B6 avant , which i have been told by an experienced employee of ATS are 10mm bigger in overall circumference than the standard fit of 205/55/16 or 235/45/17 which would normally be standard fit.

these wheels were fitted by an Audi dealer from new. I have 2 questions:-

1. Would the speedo read slower than i'm actually going and by how much(is there a calculation?). would the mileage also be affected as my MPG, which i have worked out by brimming the tank against the mileage(supposedly) done?

2. Would a smaller tyre, say a 235/35/19 be better? /ubbthreads/images/graemlins/noidea.gif

Any help please!

 

[sash]

if you want the speedo to remain accurate you need to keep the rolling circumference pretty much the same.

You can use this calculator to determine best tyre size:

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

 

[trekbiker]

thats really handy, top link thanks /ubbthreads/images/graemlins/beerchug.gif

 

[jojo]

Silly question, do 265's fit on the front with no catching? and what brand tyres are they?

 

[trekbiker]

[ QUOTE ]
Silly question, do 265's fit on the front with no catching? and what brand tyres are they?

[/ QUOTE ]

no catching, Audi put them on as new. I have conti sport contacts and 'Nexus'(??), think the former are on front axle

 

[jojo]

[ QUOTE ]
[ QUOTE ]
Silly question, do 265's fit on the front with no catching? and what brand tyres are they?

[/ QUOTE ]

no catching, Audi put them on as new. I have conti sport contacts and 'Nexus'(??), think the former are on front axle

[/ QUOTE ]

Interesting, 265s seems overtyred for an A4, but if it doesn't catch.... why not huh

 

[trekbiker]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Silly question, do 265's fit on the front with no catching? and what brand tyres are they?

[/ QUOTE ]

no catching, Audi put them on as new. I have conti sport contacts and 'Nexus'(??), think the former are on front axle

[/ QUOTE ]

Interesting, 265s seems overtyred for an A4, but if it doesn't catch.... why not huh

[/ QUOTE ]

cos of the cost per corner perhaps???

 

[rojocho]

try tyresave.co.uk for tyre diameters really easy, just fill in the sizes it does the rest.

also if you have a larger rolling diameter your speedo will read slow compared to your actual road speed, not good for speed camera's! /ubbthreads/images/graemlins/beerchug.gif