Wouldn't 10" wheels be a better choice than 10.5"?

[TheOtherEric]

Greetings all, new RS6 owner here! Looking through the big wheels thread, it looks like everyone is sticking with the OEM wheel width of 10.5" for either 21" or 22" and running 275 or 285 (sometimes 295) tires. But 275, 285, and 295 are quite commonly used with 10" wheels, which avoids the stretched look and protects the wheel quite a bit from curb damage. I'm looking at some BC Forged 21" wheels; am I crazy to consider 10" summer wheels?

[CanAutM3]

For a given tire width, a wider wheel will yield better handling response from less sidewall deflection and more grip from less contact patch deformation. So I?d say no, a 10.5? wide wheel is the better option.

[KJ-RS]

If the wheel is too wide, the sidewall will get too stretched and the handling will get worse.

For the RS6, a 10" Rear Wheel will work fine and the tire will look fine as well. I actually have this setup because the wheels I wanted didn't come in 10.5".

That said, a 10.5" wheel is also within spec and will give you the option to go to a wider rear tire.

[CanAutM3]

If the wheel is too wide, the sidewall will get too stretched and the handling will get worse.

For the RS6, a 10" Rear Wheel will work fine and the tire will look fine as well. I actually have this setup because the wheels I wanted didn't come in 10.5".

That said, a 10.5" wheel is also within spec and will give you the option to go to a wider rear tire.

I agree, over stretched is no better. My comment was specific about the OP question: stock tire width vs a 10.5? wheel or a 10? wheel.

That being said, while tires can fit on certain wheel width range, they are still optimized around a nominal wheel width, and this is even more true for spec tires.

Regarding wheel width effect on performance, the video below is a very interesting test done by TireRack.

[Maitre Absolut]

stock is 10.5 how can 10 be "better". whats the reasoning.

I think you found a 10" wheel and want to justify it. Its probably fine but definitely not better

[TheOtherEric]

stock is 10.5 how can 10 be "better". whats the reasoning.

I think you found a 10" wheel and want to justify it. Its probably fine but definitely not better

See the OP. Again, the reasoning: 1) less silly stretched look; 2) less susceptible to curb rash; 3) it has long been considered adequate for 275, 285, 295 tires; 4) lighter wheel.

And again, I?m custom ordering the wheels can specify whatever width I want. Not trying to justify 10.

What?s the justification for 10.5?? I don?t see any, except that maybe it helps clear the brake calipers. Stretching the tire to maximize lateral grip isn?t relevant to a 4,800 lb car. ?Because that?s what came on the car? is also no basis, as we all know these OEM 42 lb cast wheels are big turds.

[CanAutM3]

See the OP. Again, the reasoning: 1) less silly stretched look; 2) less susceptible to curb rash; 3) it has long been considered adequate for 275, 285, 295 tires; 4) lighter wheel.

And again, I?m custom ordering the wheels can specify whatever width I want. Not trying to justify 10.

What?s the justification for 10.5?? I don?t see any, except that maybe it helps clear the brake calipers. Stretching the tire to maximize lateral grip isn?t relevant to a 4,800 lb car. ?Because that?s what came on the car? is also no basis, as we all know these OEM 42 lb cast wheels are big turds.

Adequate does not translate to optimal. A narrower 10” wheel will yield worse handling response and less grip, this has been proven and demonstrated. And it does matter, even on a heavy car. The OE cast wheels are indeed pretty heavy, so getting lighter aftermarket wheels is an interesting option, but if you are custom ordering, might as well get the better performance option. For me, the “advantages” you state of a 10” wheel are trivial compared to the disadvantages. I would not sacrifice performance on a performance wagon.

[funclub@caseyha]

Tire review on YouTube and some other channels have done testing on track regarding wheel width vs tires. Bottom line is you want the wheel to be as wide as the Tire so it's steering response is better. It leads to faster lap times. Those are tested facts

Your opinion on tires looking silly if they are stretched is just an opinion. It's your car, do what you want, but if you want performance, then a 10.5 wheel is going to be better for a 285 than a 10.0 of you want to take corners at speed

If you just want the car to look good on the road, go with what ever you think looks best for your car. It's your car

[MtnRinger]

Who here is doing hot laps in a 6000 lb wagon? For the benefits OP mentioned and at the extremely minor increased turn-in of a 295 on a 10.5 wheel or a 285 on a 10 wheel, he is correct, a 285 tire is too narrow for 99% of use cases for a RS6 with 10.5 wheels. I found that I was literally driving on the sidewalk during spirited cornering with a 285 on oem wheels. That's best left for the track.

ETA: racers would say you want wheels 0.5" wider than tread width so you want to run 11" wide wheels with a 285? LOL, try that on the street and report back.

[funclub@caseyha]

Who here is doing hot laps in a 6000 lb wagon? For the benefits OP mentioned and at the extremely minor increased turn-in of a 295 on a 10.5 wheel or a 285 on a 10 wheel, he is correct, a 285 tire is too narrow for 99% of use cases for a RS6 with 10.5 wheels. I found that I was literally driving on the sidewalk during spirited cornering with a 285 on oem wheels. That's best left for the track.

ETA: racers would say you want wheels 0.5" wider than tread width so you want to run 11" wide wheels with a 285? LOL, try that on the street and report back.

Dunno about the rs6 however a c8 rs7 only weights 5k when full of fuel.

And I do, I run hot laps in it. I run 295s and 315s on 11 inch fully forged wheels. I wouldn't run 285s on an 11 though. Over-stretching the tire sounds like a good way to get yourself killed if you through a 5k lbs car into a turn at speed

[MtnRinger]

Dunno about the rs6 however a c8 rs7 only weights 5k when full of fuel.

And I do, I run hot laps in it. I run 295s and 315s on 11 inch fully forged wheels. I wouldn't run 285s on an 11 though. Over-stretching the tire sounds like a good way to get yourself killed if you through a 5k lbs car into a turn at speed

Most people would run 315s on an 11 wheel. Not seeing your point.

Regardless, OP id driving on the street.

[funclub@caseyha]

My point is all the other stuff in my post you didn't mention in your reply

The 295s are on 11s

And I would run 315s on a wide wheel if they would actually fit in the car. Physically impossible to do it

BTW, I drive on the street too. Both sets of wheels take turns without any issues on city streets and highways

So, again, it all really just comes down to what OP wants

Performance should be wider wheel for the tire without overstretching. dropping from a 10.5 to a 10 doesn't make any sense on a performace front imo

Aesthetics, who cares. It's about what OP wants the car to look like end the end on that front

[TheOtherEric]

Adequate does not translate to optimal. A narrower 10” wheel will yield worse handling response and less grip, this has been proven and demonstrated. And it does matter, even on a heavy car. The OE cast wheels are indeed pretty heavy, so getting lighter aftermarket wheels is an interesting option, but if you are custom ordering, might as well get the better performance option. For me, the “advantages” you state of a 10” wheel are trivial compared to the disadvantages. I would not sacrifice performance on a performance wagon.

Agreed, racers have known for decades that a stretched tire improves cornering speed. But for 99+% of us, that’s just irrelevant since we don’t track or race the RS6. And the performance benefit on track is modest anyway; truly only relevant to racing. The performance benefit of a 0.5” wider wheel on the street is absolutely negligible.

[CanAutM3]

Who here is doing hot laps in a 6000 lb wagon? For the benefits OP mentioned and at the extremely minor increased turn-in of a 295 on a 10.5 wheel or a 285 on a 10 wheel, he is correct, a 285 tire is too narrow for 99% of use cases for a RS6 with 10.5 wheels. I found that I was literally driving on the sidewalk during spirited cornering with a 285 on oem wheels. That's best left for the track.

ETA: racers would say you want wheels 0.5" wider than tread width so you want to run 11" wide wheels with a 285? LOL, try that on the street and report back.

Agreed, racers have known for decades that a stretched tire improves cornering speed. But for 99+% of us, that’s just irrelevant since we don’t track or race the RS6. And the performance benefit on track is modest anyway; truly only relevant to racing. The performance benefit of a 0.5” wider wheel on the street is absolutely negligible.

It’s not about tracking the car, it’s about overall performance, handling and feel. The 285 tire on a 10.5” is not a random selection. Audi invests significantly in the engineering, development and optimization of their cars, particularly their RS models. They probably went with that combo because the car is relatively heavy and needs good sidewall stability. Further, when using RS6/7 A0-spec tires, these tires are specifically designed and optimized to work on a 10.5” wide wheel. So no, these 285 are not “too narrow for 99% of use cases”. After some 30 odd years of tracking cars and having played with a variety of wheel and tire sizes, I can attest that the performance advantage of the right wheel/tire combo is not marginal. And it is not only about ultimate grip, but a lot about how the handling and feel. Albeit some driver might be less sensitive to those subtleties.

Now if the OP is more concerned about aesthetics than performance, that’s up to him. But he did come on forum to specifically ask for opinions on the topic. Why come ask if he already made up his mind?

[TheOtherEric]

...
Why come ask if he already made up his mind?

Lol, what a polite thing to say. Geesh sometimes car forums really suck.

Clearly I'm asking if folks stick with 10.5" for possible reasons like this:

1) "I tried 10-inch wheels and the car performed terribly because _______."
-OR-
2) "I couldn't get my 10-inch wheels installed because they interfered with ______."
-OR-
3) "Audi engineers have stated that they needed a 10.5-inch wheel because ______."
-OR-
4) "There's low risk of curbing 10.5-inch wheels since ContiSportContact 6, ____, and ____ tires have lips for wheel protection."
etc.

It seems perhaps the only support for 10.5" is speculative performance benefits, and that's perfectly fine if it's the answer.

[MtnRinger]

It’s not about tracking the car, it’s about overall performance, handling and feel. The 285 tire on a 10.5” is not a random selection. Audi invests significantly in the engineering, development and optimization of their cars, particularly their RS models. They probably went with that combo because the car is relatively heavy and needs good sidewall stability. Further, when using RS6/7 A0-spec tires, these tires are specifically designed and optimized to work on a 10.5” wide wheel. So no, these 285 are not “too narrow for 99% of use cases”. After some 30 odd years of tracking cars and having played with a variety of wheel and tire sizes, I can attest that the performance advantage of the right wheel/tire combo is not marginal. And it is not only about ultimate grip, but a lot about how the handling and feel. Albeit some driver might be less sensitive to those subtleties.

Now if the OP is more concerned about aesthetics than performance, that’s up to him. But he did come on forum to specifically ask for opinions on the topic. Why come ask if he already made up his mind?

I had 295s on mine and I thought it drove better for the 11,000 miles I put on the car. I've been tracking cars for decades as well. Grass roots motorsports did a test on all this. Lap times were 1/10th second faster on the stretched tires. I'll call that "marginal" and, again, we're talking about street use for OP.

And LOL to Audis "investment" in engineering the wheel and tire combo. Who knows what decisions and compromises lead to the oem combo. I guess we shouldn't change a thing about these cars? So much for lowering modules, forged wheels, a variety of tires to choose from etc... obviously Audi knows best

And if you're after performance versus aesthetics, you'll probably want to ditch the 22-in Wheels too.


ETA: what the heck was Ford thinking with their $1.2 MM GT mkii? These sidewalls are basically even with the rims!
https://rmsothebys.com/en/auctions/a...-mk-ii/1429566

And OMG these tire sidewalls aren't stretched at all either! Porsche must be clueless!

https://bringatrailer.com/listing/20...p-car-racecar/

[CanAutM3]

I had 295s on mine and I thought it drove better for the 11,000 miles I put on the car. I've been tracking cars for decades as well. Grass roots motorsports did a test on all this. Lap times were 1/10th second faster on the stretched tires. I'll call that "marginal" and, again, we're talking about street use for OP.

And LOL to Audis "investment" in engineering the wheel and tire combo. Who knows what decisions and compromises lead to the oem combo. I guess we shouldn't change a thing about these cars? So much for lowering modules, forged wheels, a variety of tires to choose from etc... obviously Audi knows best

And if you're after performance versus aesthetics, you'll probably want to ditch the 22-in Wheels too.


ETA: what the heck was Ford thinking with their $1.2 MM GT mkii? These sidewalls are basically even with the rims!
https://rmsothebys.com/en/auctions/a...-mk-ii/1429566

And OMG these tire sidewalls aren't stretched at all either! Porsche must be clueless!

https://bringatrailer.com/listing/20...p-car-racecar/

I think you are missing the point. It’s not about how “stretched” a tire looks, but rather about optimal wheel and tire pairing.

You might also be confusing the results of the Grassroots motorsport test that you refer to. What they found is that optimizing wheel width has a greater impact on performance than just going with a wider tire. A wider tire on the same size rim only yielded 0.1 sec improvement, while using a wider wheel yielded ~0.5 sec improvement. If you indeed have a lot of track experience, you’ll reckon that half a second is not insignificant over a 1:20 lap. They also found that fitting a too wide tire on a too narrow rim actually deteriorates performance. The Tire Rack test I referenced earlier comes to the exact same conclusion. Proper pairing is of the essence.

https://grassrootsmotorsports.com/ar...always-better/

I am sure you fitting 295 on the stock RS6 worked fine, as results demonstrate that wider tires on the same wheels can yield more grip (within reasonable margin). It has nothing to do with the “stretch”, it is about the contact patch shape. Fitting a wider tire on a given wheel is very different than fitting a given tire on a narrower wheel.

It is also important not to judge proper fitment based on looks. The width of the contact patch relative to the nominal section width has an important impact on how a tire looks and handles when installed on a given wheel. For a given nominal section width, a wider contact patch will yield a squarer looking tire that will look less stretched, while a narrower contact patch will yield a more rounded shape that will make the tire look more stretched. For instance, the 911 GT3 cup car (the factory spec for the one you reference) fits a 310mm wide racing slick to a 12” wide wheel in the rear and a 270mm wide slick on a 10.5” wheel in the front. That is actually more “stretched” than the RS6 OE fitment. Since racing slicks have a very wide contact patch relative to their section width, they do no “look stretched” even when fitted to the relatively wide wheel needed for proper support.

https://presskit.porsche.de/motorspo...1-gt3-cup.html

A good friend of mine is a tire development engineer for a big tire manufacturer. I love chatting tires with him since he is very knowledgeable. He says it is amazing how much development time is spent optimizing tires in the course of vehicle development, particularly so on high end performance cars. He says this has significantly increased in the last two-three decades with the avenue of OE spec tires.

I am not saying we should not modify anything on our cars. Any setup is the result of a chosen compromise. An individual might prefer a different compromise bias than the one selected by the manufacturer. What I am saying though is that it is important to do proper research when doing so. Handling performance is a very fine art and a delicate balance to achieve, it is easier to mess things up than to improve them. Don’t ask me how I know.

If the OP prefers to reduce “curbing risks” over handling performance and feel by going with a narrower wheel, it is up to him. But it is not something I would do.

[TheOtherEric]

I think you are missing the point. It’s not about how “stretched” a tire looks, but rather about optimal wheel and tire pairing.

You might also be confusing the results of the Grassroots motorsport test that you refer to. What they found is that optimizing wheel width has a greater impact on performance than just going with a wider tire. A wider tire on the same size rim only yielded 0.1 sec improvement, while using a wider wheel yielded ~0.5 sec improvement. If you indeed have a lot of track experience, you’ll reckon that half a second is not insignificant over a 1:20 lap. They also found that fitting a too wide tire on a too narrow rim actually deteriorates performance. The Tire Rack test I referenced earlier comes to the exact same conclusion. Proper pairing is of the essence.

https://grassrootsmotorsports.com/ar...always-better/

I am sure you fitting 295 on the stock RS6 worked fine, as results demonstrate that wider tires on the same wheels can yield more grip (within reasonable margin). It has nothing to do with the “stretch”, it is about the contact patch shape. Fitting a wider tire on a given wheel is very different than fitting a given tire on a narrower wheel.

It is also important not to judge proper fitment based on looks. The width of the contact patch relative to the nominal section width has an important impact on how a tire looks and handles when installed on a given wheel. For a given nominal section width, a wider contact patch will yield a squarer looking tire that will look less stretched, while a narrower contact patch will yield a more rounded shape that will make the tire look more stretched. For instance, the 911 GT3 fits a 310mm wide racing slick to a 12” wide wheel in the rear and a 270mm wide slick on a 10.5” wheel in the front. That is actually more “stretched” than the RS6 OE fitment. Since racing slicks have a very wide contact patch relative to their section width, they do no “look stretched” even when fitted to the relatively wide wheel needed for proper support.

https://presskit.porsche.de/motorspo...1-gt3-cup.html

A good friend of mine is a tire development engineer for a big tire manufacturer. I love chatting tires with him since he is very knowledgeable. He says it is amazing how much development time is spent optimizing tires in the course of vehicle development, particularly so on high end performance cars. He says this has significantly increased in the last two-three decades with the avenue of OE spec tires.

I am not saying we should not modify anything on our cars. Any setup is the result of a chosen compromise. An individual might prefer a different compromise bias than the one selected by the manufacturer. What I am saying though is that it is important to do proper research when doing so. Handling performance is a very fine art and a delicate balance to achieve, it is easier to mess things up than to improve them. Don’t ask me how I know.

If the OP prefers to reduce “curbing risks” over handling performance and feel by going with a narrower wheel, it is up to him. But it is not something I would do.

Sure, but a miniscule difference in "handling performance" is utterly irrelevant to us. This is not a track car.

Running 275 or 285 on a 10" wheel cannot reasonably be called a compromise, as that's plenty wheel for that. By virtually any reasonable comparison. Unless again there's something unique to the RS6 that we can only speculate about.

Ever go through a car wash listening to your wheels get ground down by the track for the entire ride? It's not fun. "Curbing risks" are very real if the wheel is too wide for the tire and/or the tire has insufficient rim protection.

[funclub@caseyha]

No, why would I take a 150k+ car through a robotic car wash and risk scratching the cermic coating I have on it?

Performance is performance, on or off track. Anyone who needs to make an evasive maneuver or hit their brakes in an emergency situation should have a healthier appreciation for how their wheels and tires could affect the handling of a 5k lbs car imo

You guys do what you want, at this point it just seems like people are trying to justify their opinion on what looks nicer than caring about how the wheels affect the actual performance of the vehicle

Since aesthics is all opinion, it's not really worth talking about any more imo

[CanAutM3]

Sure, but a miniscule difference in "handling performance" is utterly irrelevant to us. This is not a track car.

Running 275 or 285 on a 10" wheel cannot reasonably be called a compromise, as that's plenty wheel for that. By virtually any reasonable comparison. Unless again there's something unique to the RS6 that we can only speculate about.

Ever go through a car wash listening to your wheels get ground down by the track for the entire ride? It's not fun. "Curbing risks" are very real if the wheel is too wide for the tire and/or the tire has insufficient rim protection.

That is your opinion based self justification for a 10” wheel.

Many of us value handling performance on a performance wagon and I do not perceive that difference to be “minuscule”. Further, I have not “curbed” a single wheel in 35 years of driving.

[CanAutM3]

Another video on the topic. Important to listen to the commentary on handling feel. Handling is not only about ultimate grip.