New Wheels for my s6

TJT · 03-21-2012, 10:11 AM

I have stock 16's on my URS6, but I have a spare pair of 17's from a 1997 A8. The dimensions of the wheel are 17" x 8", 5 Lug, 112mm Bolt Pattern, 48mm Offset. I am not sure if they'd even look that great, but the ones on their now have some curb rash and such. Do you guys think that the 14mm difference will make a big difference? Will I have to get spacers?

GoHeels · 03-22-2012, 03:05 PM

Not sure, but I'm guessing a 14mm difference on 8" rims would be okay.

UrS4boy · 03-22-2012, 06:31 PM

I think those A8 17's are sometimes called Fat 5s because of the width of the spokes. They are a very heavy wheel and will, to some degree, impact your acceleration. As for the 48 mm offset, it is only 8 mm further in than the 8" wide five spoke Fuchs forged UrS4 wheels with ET40. Probably not an issue (which would be the front tire contacting the front spring). It should be noted that the OE UrS wheels in North America are either the stock Fuchs (16x8, ET40)(UrS4) or Avus (16x7.5, ET37). The Avus have a lower offset (ET 37) but the wheel width is 0.5 inch (12.7 mm) narrower.

GoHeels · 03-22-2012, 10:07 PM

Interesting Dave. I understand tire specs fairly well, but have always wondered a bit about rims. So I guess you're saying the Avus rims have less offset to make up for the narrowness. The result is the 1/2 comes off the inside, and the outside edge/lip stays about the same when mounted on the car.

Less unsprung weight is typically a good thing, and I've often wondered how the Avus rims compare weight wise to some of the other common S4/6 rims, and just in general.

Its late, and this probably makes no sense.

UrS4boy · 03-23-2012, 06:27 AM

Goheels: Generally made sense. I will add the details below.

A 16" UrS6 Avus wheel, with center cap and valve stem weighs about 18 lbs. Ref: http://forums.audiworld.com/showthread.php?t=2174163

As for the edges of the wheel relative to the face of the wheel hub to which the wheel is bolted, the equation for negative offset wheels like the ones on Audis and watercooled VWs is:

Distance from the hub face to outer wheel edge = (Width of wheel/2) - ET
Distance from the hub face to inner wheel edge = (Width of wheel/2) + ET

So for the 8" wide ET40 Fuchs wheel the numbers are:

Outer = ((8x25.4)/2)-40 = 61.6 mm
Inner = ((8x25.4)/2)+40 = 141.6 mm

For the 7.5" wide ET37 Avus wheels the numbers are:

Outer = ((7.5x25.4)/2-37) = 58.25 mm (in 3.35 mm compared to the Fuchs)
Inner = ((7.5x25.4)/2+37) = 132.25 mm (9.35 mm more spring clearance than the Fuchs so no problems)

For the Fat Five A8 17" five spoke 8" E48 wheels the numbers are:

Outer = ((8x25.4)/2)-48 = 53.6 mm (8 mm more inwards than the Fuchs)
Inner = ((8x25.4)/2)+48 = 149.6 mm (8 mm closer to the spring than the Fuchs) (maybe an 8 mm H&R spacer would be a good idea)

This is only the wheel. For the whole package, the tires have to be involved. But even the same nominal 225 x 50 x 16 tire specs will have different center to side wall bulge distances.

TJT · 03-23-2012, 10:34 AM

Hey dave, would the wheels affect my acceleration a noticeable amount? I am running a stock URS6 at the moment and I just can't imagine it really seeming any slower with a heavier wheel, but then again, I don't know much...

UrS4boy · 03-23-2012, 10:49 AM

F= ma = Force = mass x acceleration. For a given force (e.g. horsepower) more mass = less acceleration.

GoHeels · 03-23-2012, 01:01 PM

Thanks Dave. A bit of math involved, but makes sense in the end thanks to your examples.

As far as more unsprung weight being unfavorable in your Force = mass x acceleration equation
...it almost seems like a double negative because it takes more force to get the weight spinning, as well as accelerating forward. And then equally as affected for slowing down. But perhaps not.

It also sounds like an Avus setup weighing in at 18lbs is "not bad" and lighter than some had expected.

03-22-2012, 06:31 PM	#3
UrS4boy AudiWorld Super User Garage is empty, add now Join Date: Feb 2001 Posts: 18,209	I think those A8 17's are sometimes called Fat 5s because of the width of the spokes. They are a very heavy wheel and will, to some degree, impact your acceleration. As for the 48 mm offset, it is only 8 mm further in than the 8" wide five spoke Fuchs forged UrS4 wheels with ET40. Probably not an issue (which would be the front tire contacting the front spring). It should be noted that the OE UrS wheels in North America are either the stock Fuchs (16x8, ET40)(UrS4) or Avus (16x7.5, ET37). The Avus have a lower offset (ET 37) but the wheel width is 0.5 inch (12.7 mm) narrower. __________________ Naturally, IMHHEO(tm), Dave F. aka the Librarian Car and Mods: 93 S4, 1.8t coil pack conversion (First in world using integral POS coil packs (??)), CF (OE), S6 steering wheel, RS2'd, Samcos, MRC, TDS-1, Apikol FMIC, Eibach/Bilstein, BIRA Sys 1, relayed FP Click here to link to the UrS FAQ Thread Start Uncle Dave says "You want my 'high horse, elitist' opinion ?(IMHHEO(tm))Then just post something stupid." Unofficial Chief Cat-herder Vancouver UrS-car club

03-23-2012, 06:27 AM	#5
UrS4boy AudiWorld Super User Garage is empty, add now Join Date: Feb 2001 Posts: 18,209	Wheel Edge Calculations based on ET and width. Goheels: Generally made sense. I will add the details below. A 16" UrS6 Avus wheel, with center cap and valve stem weighs about 18 lbs. Ref: http://forums.audiworld.com/showthread.php?t=2174163 As for the edges of the wheel relative to the face of the wheel hub to which the wheel is bolted, the equation for negative offset wheels like the ones on Audis and watercooled VWs is: Distance from the hub face to outer wheel edge = (Width of wheel/2) - ET Distance from the hub face to inner wheel edge = (Width of wheel/2) + ET So for the 8" wide ET40 Fuchs wheel the numbers are: Outer = ((8x25.4)/2)-40 = 61.6 mm Inner = ((8x25.4)/2)+40 = 141.6 mm For the 7.5" wide ET37 Avus wheels the numbers are: Outer = ((7.5x25.4)/2-37) = 58.25 mm (in 3.35 mm compared to the Fuchs) Inner = ((7.5x25.4)/2+37) = 132.25 mm (9.35 mm more spring clearance than the Fuchs so no problems) For the Fat Five A8 17" five spoke 8" E48 wheels the numbers are: Outer = ((8x25.4)/2)-48 = 53.6 mm (8 mm more inwards than the Fuchs) Inner = ((8x25.4)/2)+48 = 149.6 mm (8 mm closer to the spring than the Fuchs) (maybe an 8 mm H&R spacer would be a good idea) This is only the wheel. For the whole package, the tires have to be involved. But even the same nominal 225 x 50 x 16 tire specs will have different center to side wall bulge distances. __________________ Naturally, IMHHEO(tm), Dave F. aka the Librarian Car and Mods: 93 S4, 1.8t coil pack conversion (First in world using integral POS coil packs (??)), CF (OE), S6 steering wheel, RS2'd, Samcos, MRC, TDS-1, Apikol FMIC, Eibach/Bilstein, BIRA Sys 1, relayed FP Click here to link to the UrS FAQ Thread Start Uncle Dave says "You want my 'high horse, elitist' opinion ?(IMHHEO(tm))Then just post something stupid." Unofficial Chief Cat-herder Vancouver UrS-car club

03-23-2012, 10:34 AM	#6
TJT Audiworld Junior Member Garage is empty, add now Join Date: Nov 2010 Posts: 58	Hey dave, would the wheels affect my acceleration a noticeable amount? I am running a stock URS6 at the moment and I just can't imagine it really seeming any slower with a heavier wheel, but then again, I don't know much... __________________ Trace T. 1995 Audi S6 1991 Audi 200 (10 valve) 1989 Audi 5000 2002 Audi Allroad 2001 Audi Allroad (6spd)

03-23-2012, 10:49 AM	#7
UrS4boy AudiWorld Super User Garage is empty, add now Join Date: Feb 2001 Posts: 18,209	F= ma = Force = mass x acceleration. For a given force (e.g. horsepower) more mass = less acceleration. __________________ Naturally, IMHHEO(tm), Dave F. aka the Librarian Car and Mods: 93 S4, 1.8t coil pack conversion (First in world using integral POS coil packs (??)), CF (OE), S6 steering wheel, RS2'd, Samcos, MRC, TDS-1, Apikol FMIC, Eibach/Bilstein, BIRA Sys 1, relayed FP Click here to link to the UrS FAQ Thread Start Uncle Dave says "You want my 'high horse, elitist' opinion ?(IMHHEO(tm))Then just post something stupid." Unofficial Chief Cat-herder Vancouver UrS-car club

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03-22-2012, 03:05 PM	#2
GoHeels AudiWorld Member Garage is empty, add now Join Date: Nov 2009 Location: Charlotte Posts: 344	Not sure, but I'm guessing a 14mm difference on 8" rims would be okay.

03-22-2012, 10:07 PM	#4
GoHeels AudiWorld Member Garage is empty, add now Join Date: Nov 2009 Location: Charlotte Posts: 344	Interesting Dave. I understand tire specs fairly well, but have always wondered a bit about rims. So I guess you're saying the Avus rims have less offset to make up for the narrowness. The result is the 1/2 comes off the inside, and the outside edge/lip stays about the same when mounted on the car. Less unsprung weight is typically a good thing, and I've often wondered how the Avus rims compare weight wise to some of the other common S4/6 rims, and just in general. Its late, and this probably makes no sense.

03-23-2012, 01:01 PM	#8
GoHeels AudiWorld Member Garage is empty, add now Join Date: Nov 2009 Location: Charlotte Posts: 344	Thanks Dave. A bit of math involved, but makes sense in the end thanks to your examples. As far as more unsprung weight being unfavorable in your Force = mass x acceleration equation ...it almost seems like a double negative because it takes more force to get the weight spinning, as well as accelerating forward. And then equally as affected for slowing down. But perhaps not. It also sounds like an Avus setup weighing in at 18lbs is "not bad" and lighter than some had expected.