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Wheel Fitment check

 
Old 03-13-2019, 05:39 PM
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Default Wheel Fitment check

Hello All,

I have a 2011 A8L that I need summer tires for. I am trying to figure out if 2018 A5 8.5J 19H3 ET32 wheels will fit my 2011 A8 (I need to get the winter tires off here soon). I know the 8.5in will fit fine as I have been looking at aftermarkets as well, but I wasn't sure about the ET32 part. Any advice/experience would be helpful!

In addition, Will ALL B8/B9 wheels fit? Or only certain ones?

thanks all!
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Old 03-13-2019, 05:50 PM
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Originally Posted by MVoorhees View Post
Hello All,

I have a 2011 A8L that I need summer tires for. I am trying to figure out if 2018 A5 8.5J 19H3 ET32 wheels will fit my 2011 A8 (I need to get the winter tires off here soon). I know the 8.5in will fit fine as I have been looking at aftermarkets as well, but I wasn't sure about the ET32 part. Any advice/experience would be helpful!

In addition, Will ALL B8/B9 wheels fit? Or only certain ones?

thanks all!
If you're running a 19" wheel today, you have a 9Jx19 ET33 wheel, with the standard 5x112 bolt pattern. Going to an A5 wheel will be fine. However, the issue you want to be sure about is that the weight of the D4 is significantly more than the A5 and that the wheels are certified for the addl load. My hunch says, you'd be fine. Since, you are looking for summer "tires", 19s on your vehicle seem kinda small....why not look at 20s?
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Old 03-13-2019, 06:06 PM
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Originally Posted by raj99 View Post
If you're running a 19" wheel today, you have a 9Jx19 ET33 wheel, with the standard 5x112 bolt pattern. Going to an A5 wheel will be fine. However, the issue you want to be sure about is that the weight of the D4 is significantly more than the A5 and that the wheels are certified for the addl load. My hunch says, you'd be fine. Since, you are looking for summer "tires", 19s on your vehicle seem kinda small....why not look at 20s?
Good point about the weight, will have to check that. as for the question about 20s, I would LOVE 20s (or 21s) but please see the picture below for a view of a fairly standard Michigan road :-) Worst int he nation I believe!

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Old 03-13-2019, 06:11 PM
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We messaged privately about these working out in general.

Answering your question here, "ET" is numerically the "offset" you hear us refer to in wheel posts. Many links available to explain and visualize it, but here is one from TireRack as a site probably a lot of tire enthusiasts know: https://www.tirerack.com/tires/tiret...jsp?techid=101.

The math nuance is if you are trying to visualize how the wheel will look (and fit) on the car, then as you grow or shrink the wheel width, the offset (ET) is interrelated. If you want to hold the outer wheel face the same relative to how it looks in the fender opening but reduce the width like here relative to typical stock (going from 9" to 8 "), then you want to take half of the width difference " / 2 = " = +/-6mm. The reason for the "halving" BTW is if you just held the offset constant, half of the wheel width reduction falls on the outside and half on the inside relative to the wheel centerline. By adding or subtracting only half, you basically position the face of the wheel to where it would be stock. So here, the math is 9" stock at ET 37mm [some OE fit wheels are 35mm in 20's and maybe a bit less in 19's], less approx 6mm for " wheel with decrease, nets to target of 31 ET. At 32ET actual for the wheels you have in mind, you are essentially at the same place.

Below is a visualization of what I said above in text. I chose to use the 20" OE size many have and assumed 265 tires in both cases, but you could do the same calc and get to same answer with 19 pre and post. Notice in the diagram, besides the diameter change, the only other thing happening is the inside of the wheel is what is moving out the " in question. In the field, the wheel will move out as shown, but the tire will bulge a bit more on the sides--both inward and outward. With 265's I expect it would look fine. With 275's it will look a bit more pronounced. 275/45's are spec'ed for minimum 8-" wheels if you look at some tires on TireRack, so it does still check that box if you go 275 rather than 265.

If you like the wheels and/or price is right, your choice of course. Trying to stay yet more closely stock, I would tend to go for D4 OE 19's if I wanted to run 19's in general--and thus the 9" width. D4 OE 19's also eliminates any question about vehicle weight spec for a given choice. But sticking your question, yes I think it does technically work as far as physical fit, and the outside wheel face appearance and placement will essentially appear stock. As we dialoged offline, that will generally be the case for wheels coming from late model A5's/S5's and Q5's, and perhaps some others. But getting to the 9" width except via D4 wheels is more elusive, even if the offsets otherwise mathematically line up to an OE sort of look. Q5's for example only get you to 8" widths in 19's, which in D3 tires is probably a 255 max. width.



Last edited by MP4.2+6.0; 03-13-2019 at 06:18 PM.
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Old 03-13-2019, 06:19 PM
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Originally Posted by MP4.2+6.0 View Post
We messaged privately about these working out in general.

Answering your question here, "ET" is numerically the "offset" you hear us refer to in wheel posts. Many links available to explain and visualize it, but here is one from TireRack as a site probably a lot of tire enthusiasts know: https://www.tirerack.com/tires/tiret...jsp?techid=101.

The math nuance is if you are trying to visualize how the wheel will look (and fit) on the car, then as you grow or shrink the wheel width, the offset (ET) is interrelated. If you want to hold the outer wheel face the same relative to how it looks in the fender opening but reduce the width like here relative to typical stock (going from 9" to 8 "), then you want to take half of the width difference " / 2 = " = +/-6mm. The reason for the "halving" BTW is if you just held the offset constant, half of the wheel width reduction falls on the outside and half on the inside relative to the wheel centerline. By adding or subtracting only half, you basically position the face of the wheel to where it would be stock. So here, the math is 9" stock at ET 37mm [some OE fit wheels are 35mm in 20's and maybe a bit less in 19's], less approx 6mm for " wheel with decrease, nets to target of 31 ET. At 32ET actual for the wheels you have in mind, you are essentially at the same place.

Below is a visualization of what I said above in text. I chose to use the 20" OE size many have and assumed 265 tires in both cases, but you could do the same calc and get to same answer with 19 pre and post. Notice in the diagram, besides the diameter change, the only other thing happening is the inside of the wheel is what is moving out the " in question. In the field, the wheel will move out as shown, but the tire will bulge a bit more on the sides--both inward and outward. With 265's I expect it would look fine. With 275's it will look a bit more pronounced. 275/45's are spec'ed for minimum 8-" wheels if you look at some tires on TireRack, so it does still check that box if you go 275 rather than 265.

If you like the wheels and/or price is right, your choice of course. Trying to stay yet more closely stock, I would tend to go for D4 OE 19's if I wanted to run 19's in general--and thus the 9" width. D4 OE 19's also eliminates any question about vehicle weight spec for a given choice. But sticking your question, yes I think it does technically work as far as physical fit, and the outside wheel face appearance and placement will essentially appear stock. As we dialoged offline, that will generally be the case for wheels coming from late model A5's/S5's and Q5's, and perhaps some others. But getting to the 9" width except via D4 wheels is more elusive, even if the offsets otherwise mathematically line up to an OE sort of look. Q5's for example only get you to 8" widths in 19's, which in D3 tires is probably a 255 max. width.


Thanks again for all of your help! Your post are always incredibly informative and awesome!
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Old 03-13-2019, 06:21 PM
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Originally Posted by MVoorhees View Post
Good point about the weight, will have to check that. as for the question about 20s, I would LOVE 20s (or 21s) but please see the picture below for a view of a fairly standard Michigan road :-) Worst int he nation I believe!
Good pic BTW. Unfortunately here in warped spending priorities and diverted tax revenues CA, that could frankly be many a local backwater street in any of San Francisco, Oakland or San Jose. Just take whatever (shorter) time it is in MI and extend it literally out to 30 or 40 years, if even that. In between they (rarely) bandaid the worst potholes, plus apply a little thin slurry to one quarter of the roads maybe once every 6-10 years. Even that is proverbial useless lipstick after about 3 more years in mild coastal weather without snow or ice.

Last edited by MP4.2+6.0; 03-13-2019 at 06:26 PM.
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Old 03-14-2019, 03:31 AM
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My 2014 A8L came with 20" wheels (see photo). I swapped them out for some D3 18" rims that I had bored out, put new 235/55R18 Michelin tires on them. Very happy with the softer ride on Northern NJ roads.
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Old 03-14-2019, 04:25 AM
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Originally Posted by cliA8l View Post
My 2014 A8L came with 20" wheels (see photo). I swapped them out for some D3 18" rims that I had bored out, put new 235/55R18 Michelin tires on them. Very happy with the softer ride on Northern NJ roads.
Excellent job... fantastic looking wheels!
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