spijun

Read what they say tire manufacturer, not the merchants who sell them.
Do you you know the structure of the tire tread????
Can you explain to me how 255mm tread tires can be 260-265mmm LOL

Which tires to be mounted on 7 "and 10"

The new tire model is: 255-265/45R19

Tread tire is fixed, it means it is impossible to change the mounting on wide or narrow wheels J7,5 or J9,5
http://www.discounttire.com/dtcs/infoTireMath.dos#row1
http://www.ajdesigner.com/fl_tire/tire.php
http://www.sizemytires.com/calculato...FWfMtAodXTMAVg

Good luck

MP4.2+6.0

Actual field pictures > diagrams/calculators. The OP's actual pictures of the wheels sitting there clearly rule. Bridgestone or Michelin didn't simply make his tires wrong, nor would Audi logically recall or swap them out if anyone ever seriously challenged "the spec." The Bridgestone's seem to be the really wide ones actually, I noticed the same when I bought the low miles S Line take off set w/ the Bridgestone's recently.

See below for more discussion.

gk1

As others said 255 is nominal tread width...

Because a tire's section width is influenced by the width of the rim upon which the tire is mounted, the correct industry assigned measuring rim width for the tire size being measured must be used.

The width of a tire mounted on a narrow rim would be "narrower" than if the same tire was mounted on a wide rim. NOTE: because the overall diameter of a steel belted radial is determined by the steel belts, there is little, if any, change to the overall diameter of the tire due to differences in rim width.

The industry rule of thumb is that for every 1/2" change in rim width, the tire's section width will correspondingly change by approximately 2/10" = 5mm.

Yoshimura

spijun, if you look tire specifications from manufacturers, you'll see that actual section width vary for the same tire size. Check those tires for exemple:

http://www.michelin.ca/tire-selector...ails#techspecs

P285/35ZR19 is 290mm and P285/30ZR20 is 278mm!

Also, manufacturers specify "Section Width on Measuring Rim Width". This probably means that section width is affected by rim width.

I just noticed this note at the end of the specification:

The dimensions shown are average tire design values for tires measured on specified measuring rim widths. Some tires may vary from this value by +/- 3% of the section height (affecting overall diameter), and +/- 4% of the section width

MP4.2+6.0

if you measure across the tread for a given width, it often varies some from one tire model to another. In some sizes around this one, I have seen it vary the better part of a full inch. Here, the rim width alters it only slightly, since it affects the point the tire starts to curve into the sidewall only a tiny bit (and for that matter, they have standard places on a tire to measure the deemed tread face whether it is actually touching the road specifically or not at that shoulder area). The rim width has more of an effect on the sectional measurement.

TireRack's specs sometimes pick up this tread width measurement, at least for some tires. Manufacturers vary on publishing or not publishing this, even from one tire to the next. If you focus on only one tire size on TireRack with a bunch of alternative models to choose from and then drill into each tires specs, you will start to see the tread width vary some. Can also see it more for some types of tires, like various A/S's to other summer tires.

As a different topic, the weights can vary a fair amount per tire--several pounds frequently. Significant enough that doing things like using two piece rotors (in part) to reduce weight can be fully offset (or doubled in the other direction) by a particular tire choice that s either heavier or lighter even in the same nominal size. It can correlate some to A/S tires (and of course is way heavier for run flats), but then some summers can be lighter and others heavier. XL load or higher speed ratings may bump up the tire construction and weight too. Tying to the original subject, a predictable result is that for a given tire of the same nominal size that shows up wide in the field and by the measurements, that tire model is going to tend to weigh more than others of the same nominal size that aren't as wide.