audi q7 tdi larger? snow tire options

[allan]

Our 2013 Audi Q7 (TDI #5 that we've had) that we just got needs better tires. been up in South Lake Tahoe
dealing with massive massive amounts of snow (working on the 6th 3ft dump this year). last Audi TDI and VW TDI
were both crushed by falling 16" tree last year with me standing between them (audi was totaled)

Roads are completely hosed (3-4" potholes from flooding), and need to get something to replace
stock 21" wheels since I had 2 flats in 2 days.

stock 21", P295/35 ZR21. offset ET53, 5x130 bolt pattern

option #1.
get 18" porsche 2003 cayenne wheels (18" i think is smallest that can still clear brakes)
with same bolt pattern and offset, and run studded tires
during winter with same outer diameter. would give me good traction and 1.5" more meat between rim and road.

option #2
get 18" porsche cayenne wheels
get larger diameter tires (what would my limit be with stock suspension?). i'll rarely if ever
take it offroad (wife's vehicle), but having extra ground clearance can be good during storm.
was up to the top of wheels last week.



have the rosstech cable, so i could modify instrument cluster to make speedometer & odometer work.

but the stock spare is a special folding deal.

and not sure how long I could drive with a tire different
than the others before damaging AWD. not having a spare around here during snow storm might mean
a 5-8 hour wait for tow truck. carrying a large full size spare around in the rear would be a pain but might be
best option.

Is there a fuse that you can pull like in the subaru to disable the rear AWD? or with VCDS?

 

[Lug_Nut]

295/35-21 is a wide tire. A comparable circumference (29.1 diameter) tread with an 18 inch rim would be a 235/60-18 and that's much narrower. What rim width is your proposed 18 winter wheel?

The tire you select may totally hinge on what wheel you can fit over the Q7 brake. See if a Q5 offering may clear. Offset should be the same in whatever rim diameter if the intent is to keep a nearly similar rolling tread circumference (maintains speedo and odo accuracy and maintains ground clearance).
A narrower rim width will permit a narrower tread which is better for snow. A wide tire will snow-shoe and sit on top of snow, a narrower one will penetrate better down to the road surface where grip is greater.

Her 2011 Q5 came with 19s. I'm believing those are also 5x130 bolt pattern. They are 8 inch wide 39 mm offset. Summer will have 255/50-19 on those. I bought winter alloys (presently on the truck so I wasn't able to get width and offset specs) in an 17 inch diameter fitted inside 235/65-17 studded snows. Those two sets each are coincidentally 29.0 inch diameter, really close to your current 21 inch rim tire size.

P.S.: Maintaining rolling circumference will also mean the spare, when inflated, will be compatible.
P.P.S.: center diff (in transmission housing) can't be 'switched off'.
P.P.P.S.: a 1/2 inch wheel spacer and appropriately longer wheel bolts would make a 39 mm offset wheel a 52 offset.

 

[allan]

thanks didn't know about the wide vs narrow on snow.

18" rims were an option that year, and i'm going to get an old one and test for fit over the calipers. supposedly 17" won't work for Q7

the cayenne OEM 2003-2006 is 18x8.5. guy at tire shop said some of the q7, cayenne, and maybe mercedes G used that 5x130 pattern. has same 53mm offset.
mainly leaning to it since i can get them cheap off ebay ($80-90ish). no cheapo steel rims i could find in that size.

chains tend to chew up the wheels anyway, so didn't want anything nice.

 

[allan]

decided to go with studded 265/60R18 on porsche 18" rims. waiting on them to come in @les schwab