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http://www.carbibles.com/tyre_bible_pg2.html

But its the right way

Check it out!

Quite an interesting site too !

Very good that. I know my Speedo is over calibrated as when you go through the speed traps in urban zones the speedo can read 33-35 mph by ony read 29 on the roadside camera sign.

The downside with 275/30/19 is: the odometer will show more mileage than what the car actually traveled, not so good for depreciation! just a thought.

Ozrs4 wrote:The downside with 275/30/19 is: the odometer will show more mileage than what the car actually traveled, not so good for depreciation! just a thought.

so if we put smaller tyres on will the odometer show less milesthan we actually travel??
not that i'm gonna change from the 255's- just curious

booski wrote:

Ozrs4 wrote:The downside with 275/30/19 is: the odometer will show more mileage than what the car actually traveled, not so good for depreciation! just a thought.

so if we put smaller tyres on will the odometer show less milesthan we actually travel??
not that i'm gonna change from the 255's- just curious

Yes, it would but then getting a few speeding tickets coz you thought your speedo said you were only traveling at 60mph when you're actually doing 65mph is not fun either for the hip-piocket!!! haaha, can't have it both ways my friend.

What matters is the rolling circumference - 275/30's have a smaller rolling circumference than 255/35s so the wheels turn more times per mile, which means it appears you're going further and faster than you really are.

Ozrs4 you're a dentist like me aren't you - get working !! lol

PetrolDave wrote:What matters is the rolling circumference - 275/30's have a smaller rolling circumference than 255/35s so the wheels turn more times per mile, which means it appears you're going further and faster than you really are.

Ok - so who is going to build a converter to work out true mileage?!

Ozrs4 wrote:The downside with 275/30/19 is: the odometer will show more mileage than what the car actually traveled, not so good for depreciation! just a thought.

True and I may have asked this before, is there not a way through VAG-COM to prgram in what tyres you are running or is that just RNS-E specific for it to calculate on the Sat Nav? I remember when retro fitting an RNS-E on my B6 S4 it asked for wheel size and tyre size?

There must be becasue surely thos who were running 18" wheels on the RS4, their rolling radius is never going to be the same as that on the 19's?

P_G wrote:True and I may have asked this before, is there not a way through VAG-COM to prgram in what tyres you are running or is that just RNS-E specific for it to calculate on the Sat Nav? I remember when retro fitting an RNS-E on my B6 S4 it asked for wheel size and tyre size??

That's just to calibrate the RNS-E - it has no effect on the speedo or the odometer.

I suspected that part Dave, I was more curious for those handy on VAG-COM whether something similar existed for to odometer otherwise how does it know what size wheels and tyres are on the car because they would be standard factory odometers for the entire Audi / range surely?

P_G wrote:I suspected that part Dave, I was more curious for those handy on VAG-COM whether something similar existed for to odometer otherwise how does it know what size wheels and tyres are on the car because they would be standard factory odometers for the entire Audi / range surely?

Aren't they calibrated for each car/tyre etc. That plus the +/- 10% rule would cover it.

Did this back in 1997 when a mate of mine was looking to change the tyres on his Jensen Interceptor III...

Have put starting dimensions in for RS4. Play away...

(Have to unzip it - as forum won't allow an Excel att.)

P_G wrote:I was more curious for those handy on VAG-COM whether something similar existed for to odometer otherwise how does it know what size wheels and tyres are on the car because they would be standard factory odometers for the entire Audi / range surely?

They're not standard speedos/odometers across the entire range - they're specific to type, e.g. the RS4 speedo/odo is only used on the RS4, and that applies across all models/variants (look on ETKA, there is a different speedo/odo combination for each model/engine combination). Not only is the calibration different but the tacho has different redlines and the speedo has different maximums...

With VAG-COM you can calibrate the mpg reading on the trip computer by +/- 20% but there's no known calibration adjustment for the speedo/odo. I guess that's hard-coded in the firmware?

Are you supposed to get the wheel alignment done when you change from 255 to 275 tyres? As I am still experiencing judders!
Thanks