Why?

The standard is tires must be within 30% on the SAME axle. Check your manual.

Where does it say in any manual tires depths must be the same between axles? Thats some Subaru rule where each axle get 25% all the time.

 

To be track ready! Or just an abundance of caution after some experimenting with various 20" alternatives. I am hoping this is the optimal setup for 20" wheels to reduce weight, sidewall bulge and increase response and handling with the smaller sidewall. I wanted to maintain the optimal OEM ratio and simply feel better about a closer match than pairing a 9.5/32 tire with a 8/32 tire (the existing 285/40/20 in the rear).

I've always been curious about this process and it's exceeded my expectations so far.

 

If it makes you feel better. That’s all that matters.

 

A maximum 30% variance is pretty big, considering summer sneakers for the Macan run ~10/32" when brand new.

My tire guy said he believed it was to protect the differential, thinking that if one side is too worn, the system "thinks" there's
slippage or loss of traction because the revolutions per axle are too far off and it allows slip to accommodate what it believes
is a loss of traction on one side. Over time, he though tit would result in excessive wear on the differential, resulting in a big hit
to the wallet - tires are cheaper to replace than differentials (like brakes vs. transmissions and the downshifting to brake argument).

That would allow for a new tire to be mounted on one side of the vehicle if/when the worn tire on the other side
was worn down to 7/32". Recall the 8/32" is only 1/4", which is not a whole lot of remaining tread!

Are forum members running their tires til the steel wires are showing?!? (I once had a VW bus that inadvertently got to that point - yikes)

I'm thinking not...

 

I replaced 3 perfectly good tires when I had a puncture because I was changing brands. I’d never replace just one unless it essentially happened driving home from them being installed. The manual does also say always replace both on an axle when replacing one.

 

As I suspected, the front tires rotate at a slower rate due to their larger diameter. Below is after a couple of revolutions in reverse using fairly new NE0 tires.

 

As I suspected, the front tires rotate at a slower rate due to their larger diameter. Below is after a couple of revolutions in reverse using fairly new NE0 tires.

Interesting, nice empirical data. So what? for example, Subarus are locked at 25% traction to each wheel. Hence, the need to ensure the rolling circumference is within some tolerance. Otherwise the differential is damaged. that's not true for these cars so I'm not seeing the point?

Whats the big deal? What am I missing.

 

My later set of tires are the same as yours. The brand. So far, based on the fact I live in the Houston area, I’ve run Conti 6’s, Goodyear Asymmetrics, Pirelli and now Michelin. Best tire, IMO? Goodyear. Have you looked at them at all?

 

I had mixed experiences with Goodyear. Mainly due to traction issues on a more powerful rwd car that was solved after switching to Michelin PSS and then PS4S. I've stuck with Michelin since and they have been sublime each time, whether for my cars or my wife's.

The OE Goodyear A/S that came on the Macan were pretty good for comfort and steering feel but compromised on traction. I switched to the PS4 SUV and loved them.

The 21" wheels pictured above had the OE Continentals, which I was looking forward to trying out but they tramlined badly and I switched to the Michelin PS4 A/S and could not be happier for an OE tire.

For this 255/285 20" project, I was considering OE Pirelli PZ4 from an Alfa Romeo Stelvio Quadrifoglio but I couldn't find great reviews so I went with Michelin PS4 and PS4S. Essentially, I end up at Michelin and couldn't ask for anything better. That may change for each individual who has different needs from a tire. On a meta level though, Michelin tends to top the charts in reviews in the categories I shop.

 

Those Pirellis I mentioned? PZ4's. Couldn't wait for them to wear out. The A/S I mentioned are the Asymmetrics Sport Eagle something or other and not All Season. My bad... Most of the year you don't need an A/S on the Gulf Coast. Next Thursday the wife's Benz gets a full set of the Michelin PS4S tires installed. I know they're two very different vehicles. My Macan runs the PS4's now. The Benz will be running the PS4S by the end of next week. I'll be curious in comparing the two all the same.

 

I typically run exclusively Summer tires also but in looking at the latest round of OE tires for the 21" wheels, the Michelin PS4 All Seasons seemed to be the best choice over the Pirelli Corsa Summer tires.

On your Macan, you have PS4 SUV which are different than PS4 but I am curious to hear your comparison to the PS4S. In my case, I found the PS4S more comfortable because the specific sizes I chose had a much lower and closer to OEM load rating than the PS4 SUV which are at an exceptionally high 108 and 110 to accommodate heavier SUVs. That makes them heavier as well to their OE N0 counterparts that have a lower load rating.

 

After a couple of days of driving, any signs of shaving are gone and these tires are perfection in terms of steering feel, feedback and overall handling.

 

Always nice to have the option to have tire shaved. I have used the service from tirerack in the past.

 

Just did something similar with my AWD and ended up shaving the front tires to match the rear. Tire Rack made it super easy, added a note and $25 later, done the same day. Took me a bit to figure out the process, but worth it for peace of mind. If anyone’s looking for a place for bigger setups, there’s a heavy truck tire shop Montreal that handled some extra work for me without any hassle.

 

That's really so interesting. Today was the first time I ever heard about shaving tires.

 

Yeah....file it with the Pedal Commander and Cobb tuning magic.

 

It's not for everyone but nice to have a mainstream, available option if an individual's needs direct them to this specialized work. For me, it accomplished what I needed to safely match diameters when experimenting with different, non-OE sizes.

In the end, I enjoyed the 255/45/20 and 285/40/20 combination a lot but ended up selling all extra sets and going with a set of OE 21" GT design wheels with OE tires (the lightest OE 20" or 21" combo), which I like even more.

 

It's not for everyone but nice to have a mainstream, available option if an indiviual's needs direct them to this specialized work. For me, it accomplished what I needed to safely match diameters when experimenting with different, non-OE sizes.

In the end, I enjoyed the 255/45/20 and 285/40/20 combination a lot but ended up selling all extra sets and going with a set of OE 21" GT design wheels with OE tires (the lightest OE 20" or 21" combo), which I like even more.

View attachment 297878

View attachment 297881

Those wheels look amazing.