Tire Size Conversion From 245/40/18 To 17 Inch

[vtsquid]

Searched all over but couldn't find the answer to this.

I want to get a set of winter tires on rims for my 2010 A4 with 18 Sport Pkg. snow tires in 18 inch sizes are way expensive so I'd like to go to a 17 inch rim and tire.
What is an equivalent 17 inch tire size for the stock tire that I have now? =245/40/18

Thanks for any help.

[AvantJunkie]

Here you go...

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
245/40/18 3.9 12.9 25.7 80.8 784 0.0%
245/45/17 4.3 12.8 25.7 80.7 785 -0.01%


Edit: The values don't exactly line up in the columns, but you get the idea. A 245/45/17 is damn near the exact same size.

[vtsquid]

Here you go...

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
245/45/18 3.9 12.9 25.7 80.8 784 0.0%
245/45/17 4.3 12.8 25.7 80.7 785 -0.01%


Edit: The values don't exactly line up in the columns, but you get the idea. A 245/45/17 is damn near the exact same size.

You Mean 245*40*18 is equivalent to 245-45-17 right?

[vtsquid]

BTW forgot to thank you.
-Andy.

[AvantJunkie]

Yes-- Typo on my part! Fixed it. And you're welcome!

[vtsquid]

Should I be concerned with hub sizes between B8 and B7 A4s?
This would limit my wheel choices.

[L0U]

you need at least a 66.56 bore, or larger with a hub ring attached to make it 66.56. If it is smaller, then it won't fit unless you get the rim bored to the larger 66.56 size.

17s usually come in 7 or 7.5" size 245s will be very wide for that rim in snows. 225x50-17 is what I would buy in a 17x7.5, or a 17x7 rim. et35 to et45

[Wildcat216]

On the subject of wheel/tire conversion, what is the OE wheel width for the B8 18" rims? I am buying replica wheels and want to make sure my sizes are correct. Thanks in advance!

[jcs]

18" Sport rim specs: 18x8 ET47 245/40/18

I would go with the factory 17" spec: 17x7 or 17x7.5 with 225/50/17. That's actually what I used for my winters this year.

[vtsquid]

18" Sport rim specs: 18x8 ET47 245/40/18

I would go with the factory 17" spec: 17x7 or 17x7.5 with 225/50/17. That's actually what I used for my winters this year.

The wheels are ASA GT2s 17X8 with 40mm backspace,Tires are Dunlop SP Wintersport 3D in 245X45X17.I'll post up pics when they get here.-Andy.

[c99]

I would go with the factory 17" spec: 17x7 or 17x7.5 with 225/50/17. That's actually what I used for my winters this year.

+1

[jcs]

The wheels are ASA GT2s 17X8 with 40mm backspace,Tires are Dunlop SP Wintersport 3D in 245X45X17.I'll post up pics when they get here.-Andy.

Cool. My biggest concern with 245 wide tires was their snow cutting ability and thus I went down to 225, but with quattro you shouldn't have any issues. I've heard great things about that rubber and my dad runs 3Ds on his RWD Infiniti.. they were good till they got down past half tread, didn't blow me away or anything. I got Marangoni's this winter and they were great,we'll see how they hold up with reducing tread.

[mmurph318]

you need at least a 66.56 bore, or larger with a hub ring attached to make it 66.56. If it is smaller, then it won't fit unless you get the rim bored to the larger 66.56 size.

17s usually come in 7 or 7.5" size 245s will be very wide for that rim in snows. 225x50-17 is what I would buy in a 17x7.5, or a 17x7 rim. et35 to et45

+1

[vtsquid]

I understand what you guys are saying about 245 width VS 225.I just didn't want the tires looking too skinny on my car.If floatation in snow becomes an issue I will go to the 225s when the 245s wear out.

[Wildcat216]

On the subject of wheels/tires, can someone with OEM 245/40-18s tell me what tire pressure is listed on the door jam. I am upsizing from 17s and want to get the pressure right.

Also, does anyone know how to reprogram the car to make sure "it knows" the size of the wheels/tires? I know the size can affect the speedometer calibration. Thanks!

[B_Boy]

forget the conversion go with these tires Continental ExtremeContact DWS. best tire for the price hence y they r back ordered till may. I have them on my b8 and they are wonderful, wet and dry performance equal or better than michelin pilot sport ps2 but way cheaper and wayyyyyyy better tread wear! to top it off they are all season so u can drive in the snow and they are top rated for snow also.

http://www.tirerack.com/tires/tires....9&autoModel=A4 2.0 Quattro&autoModClar=Premium Plus

[Wildcat216]

Ya know, I put those on my wife's RX-8 a couple months ago, and now they are back-ordered everywhere. So for the Audi I went with Goodyear Eagle GTs that have a very similar tread design. Since my wheels are coming in today and and I have a buyer lined up for my stock setup, I just couldn't wait for the Continentals to restock. I too would recommend those tires to anyone looking for a very versatile all-season.

Anyway, anyone know the OE tire pressure for the 245/40-18 tires listed on the door jam?

[jcs]

Don't know what's listed on the door jam but I remember my last service report saying all four set to 35psi by the tech.

[Wildcat216]

much appreciated

[equ]

245/45-17 or 225/50-17 will work. I use the latter for snow tires. I generally run 35f/33r cold pressures on my 245/40-18 summers.

[vtsquid]

Hey equ,I'm intrigued;where is Dogville?

[VMRWheels]

for future reference, here's a great tool for comparing tire sizing: http://www.1010tires.com/tiresizecalculator.asp

[Wildcat216]

for future reference, here's a great tool for comparing tire sizing: http://www.1010tires.com/tiresizecalculator.asp

Thanks. I don't think I will be bothering with recalibrating my speedometer given the .1 mph difference resulting from my wheel and tire setup change.