DHL

I assume the OE center caps will fit, but come to think of it, I don't know for certain.
Will take some more photos when I can wash the car. Am waiting for the rain to stop here in CA. BTW, the HREs are finished in "dark clear tint" over a shot peened aluminum alloy finish.

BMinSFL

No worries about a dirty car, if the stance and wheels are right, it will always look good. Thats a beautiful finish, on the darker side but not the standard black that we all have seen 100x times over. I was considering a tinted clear on the Spyders when I had them powdercoated but wanted the classic, bright, BBS look for now. Brake dust from standard pads will darken them in to time.

I decided to not pursue the front 20x10, 275/40 square setup. Aside from the cost, I am very happy with the feel as-is. I tried 20mm spacers up front for aesthetics to bring the tires out more flush. That nailed the look I was going for but with 15mm spacers out back, its causing a sharper turn-in and twitchier steering feel. Its not bad at all, but very interesting to play around with and see how only a 5mm spacer difference (10mm total track) can make a difference. Time to try 20mm out back to match.

DHL

Yes, I wanted a finish between silver and black. Actually first had this color on my Saphire blue 911, and it also looks good on the Ginsien blue Macan.

One thing you probably should be aware of using spacers. Sometimes you get fender/shock interferences when the suspension is fully compressed or fully unloaded, which may not be evident driving around lazy on the street. BTW, the HRE rear wheels are 10.5" wide, not the stock 10.0".
This website is pretty good for checking wheel fitment. Put in you spacers along with your actual offset and see how they fit.

https://www.wheel-size.com/size/pors...macan-gts--434

https://www.wheel-size.com/calc/?whe...-40-21X9.5ET27

BMinSFL

Cool stuff on those sites, I already have the hardware, no calculation needed since I can physically test but I always take it easy when first testing a new fitment. I am not expecting clearance issues since I am simply getting the tire to an OE (or OE with common 10mm spacers) positon with a smaller overall diameter. The OE tire fitment on 20" wheels has bulge whereas my fitment is now inboard due to the slight OE-style stretch. That brings the wheel a bit more outbard or flush but the top of the tire is ultimately inboard of the fender

More evidence for the one-time poster from post #18:

Grip on wet pavement ⬈ Narrower tires improve the braking performance on wet pavement because they can expel the water from beneath the wheel more effectively.

dml

Where are you getting this 10X factor from? The kinetic energy of all of the mass spinning at the edge of a disk is the same as the energy of that same disk moving at the edge velocity. In other words, the total energy if all of the weight is at the outer perimeter of the tire is only 2X. Since it isn't, more likely 1.5X or so.

DHL

From tuners like Frank Fahey. Its unsprung weight and that is the commonly accepted fudge factor. You can also ask the techs at HRE which gave me the same info.

DHL

It should not matter what the rim size is because to overall tire+wheel od (rolling diameter) should be the same. What matters is the width of the tire and the offset with the spacers. If you are not going the wider rim/tire up front, then your are not likely to have an interference issue. Years back, I owned an E39 M5 and all the rage was to mount the rear wheel fitment upfront for a non staggered setup. Until a few folks did some track schools and found the tire was rubbing on the inner fender/strut under high compression braking. Only way to see this beforehand was to pull the springs and compress the suspension manually to check. You also vary the steering angle lock to lock with the suspension fully compressed. If that is what you mean by testing, then you are good to go.

BMinSFL

OD is slightly smaller with the smaller tire setup, which is why there is such a big difference in performance, both from lower weight and a slightly lower effective final drive ratio (numerically higher).

The spacers are only for looks, not for any interference concerns since I am using the same OE wheels and only have more clearance with the smaller tires. Much easier when going smaller than when going with bigger wheels and tires!

DHL

This is a bit of a generalization. All other things being equal (tire compound, tread design, etc) maybe, but I think its due to the higher contact pressure (same weight over samller contact patch). But dedicated rain tires are the same width (look at Formula 1 rain/intermediate tires for example) because they have wider rain grooves and sticker compounds designed for adhesion to wet surfaces. I don't think stopping distance data for wet pavement (ie Tire Rack tests) will confirm that given the same compound and tire design, stopping distances are shorter with a narrower contact patch.

BMinSFL

This was from the link you posted. How much do your HRE wheels weigh?

DHL

From an email from HRE (Logan Ostrander) "I was forwarded your contact information regarding your inquiry for some wheels to put on your Macan GTS, specifically our R101 or other lightweight alternative. Since this vehicle is quite large and would run 21” wheels, they will of course be slightly on the “heavier” side just due to the load-ratings required and diameter. I would say our 21” P101 would probably be the best bet, this is a similar relative to the R101/LW. For the P101 you be looking at roughly 23-24lbs for the front and rear wheels, this would be with a 21x9.50 & 21x10.50-wheel size" FWI I ran the HRE R101 LW (light weight) on my 991.2 Carrera S.
I think with Mich Pilot Sport 4S tires they weighed 33-34 lbs each vs the stock alloys with Mich Pilot Sport All Season rubber at 44 lbs each or so.

BMinSFL

Nice! The OE forged 21" Turbo IIs are about 30.5lbs each but if you had 21" sport classics, those are 35-36lbs each!

roule

First of all, the wheels look great. Kudos for dialing in what you want in a wheelset.

With all due respect, though ... this thread confuses me. The first post implied that more performance was desired. Since that first post, I haven't been able to locate any objective performance measurement offered. Lots of pictures promoting subjective appearance preferences, but nothing showing dynamic performance measurements.

Motor Trend did a rim comparison test (construction method, not size difference) using identical tires quite a while ago: https://www.motortrend.com/how-to/mo...ce-wheel-test/ The results showed that ... commercially available wheels affordable to the common man don't make anywhere near the impact that theory and advertising hoopla would imply.

Others have laid out some guidelines, which are good to keep in mind. Allow me to summarize some more generally accepted truths:
- On a ~4400 pound SUV, it's unlikely that the average driver would be able to feel or measure 5, 10, or even 15 pounds difference on wheel weight (just the rims).
- Total mass of wheel, tire, TPMS, spacer, etc, all add up. It's possible to find a 19" diameter setup that weighs more than a 21" diameter, and vice versa. The available options affordable and legal to the common man won't make much difference in the big scheme. Diameter of wheel rim or its mass in isolation is a poor indicator of performance or mass. If maximum total performance is desired, then your use case (smooth streets, potholed streets, track, forest road, offroad, etc) needs to be considered first and foremost. Reduction of mass is always a goal, but it is seldom a primary requirement especially when you consider the safety implications of wheel and tire selection. The dumbest thing you can do is pick inappropriate tire and wheel for your real needs. We've all seen those on the side of the road.
- Steering forces (which the attentive drive can feel) are altered by rim offset. Steering feel is not usually considered a performance measure, but messing with Porsche's designed steering geometry would call into question why anyone would pay the Porsche premium only to mess with the steering geometry. Choosing the wrong offset to the extreme can have negative effects on suspension joints, tire wear, and dynamic performance. In general, offset spacers can never improve performance versus selecting the correct rim for the job, usually pretty close to what Porsche dials into their higher end models (i.e., reference GTS for the Macan, not the base model for optimal wheel package for dynamic performance. The base wheel package, as always, is the economic choice).
- After the nut behind the whee, the next most important performance part for your vehicle (any vehicle) is the tire. Benchmarks there are a moving target and only you can select the right one for your needs. The larger the tire contact patch, the more forces can be put to the ground, the better the total vehicle performance. Ergo, in general, the wider & larger diameter rims are popular despite these often resulting in substantially greater total mass. Some of the best snow or ice-specific tires are narrow; a sticky summer tire might be as wide as you can stuff in the wheel well. A narrow super sticky tire will probably give you more grip than you can ever use legally but durability will be poor. Everything is a tradeoff.
- Choosing the lightest tire (as opposed to ideal total package) would imply giving up both width and sidewall height (profile). Taking this to an extreme (rubber bands on the rims) almost always results in dynamic performance degradation and/or safety implications.
- Choosing too large diameter rim will result in sacrificing tire sidewall height in order to fit in a wheel well and/or limiting suspension travel. This not only reduces comfort but at some point it will reduce performance on all but pristine high-grip racetrack surfaces. Inadequate sidewall means the driver has to increase tire air pressure to protect the rim, which relatively makes a tire hard and less able to maintain optimal grip with the road. "Power is nothing without control". You want that tire deformed to every microcrack in the asphalt, not bouncing over it. A general rule is: for best dynamic performance, apply the least air pressure needed to prevent tire overheating for the given application, and also just enough pressure to maintain driver's desired feel under hard cornering (every tire has its unique sidewall lateral stiffness). Any increase in inflation pressure beyond that will improve fuel economy/lower rolling resistance/ lower tire wear but degrade traction (forward, lateral acceleration and braking). Having a bit of extra sidewall for the rough roads of the real world is usually a good idea and the driver can fine tune the air pressure to his specific needs.
- Choosing too small a rim diameter is difficult on any Porsche given the size of brakes. The era of very tall profile tires ended long ago with the advent of strong rim construction and well-tuned suspension damping and, let's face it, more asphalt covering the planet than ever before. Needless to say the less smooth your terrain, the taller profile you will want those tires to be for comfort and rim safety.
- Ultralightweight rims are awesome. Buy them and put them on your track day Cayman GT4 early and often. But I'd not go for that on any SUV. Real world conditions would incentivize the wise driver to avoid race rims. Carry some safety margin; pick rims with a load rating that follows common sense. You didn't buy an SUV to let it sit on a dainty glass display stand, did you?
- if you really want superior rims, you can find them. In general, for best strength/weight: choose straight relatively skinny spokes, two spokes per lugnut, minimal ornamentation, never multi-color or partially face machined, always one-piece (monoblock) fully forged will typically give you best strength to weight ratio. But for an SUV? That's a lot of money for something you're not likely to feel, and which probably won't appreciably improve your Nurburgring lap time.
- If performance is more important than looks, then avoid wheel spacers and get the right wheel dimension, which for this size vehicle is more important than rim mass.
- the gap between top of tire and the fender arch is not a measure of performance. It does however indicate the maximum suspension travel before tire contact, and for many people More is Better. If you lower your vehicle to look better -- yes, you'll feel it. But there is negligible performance gain in real world performance, and perhaps noticeably worse comfort. All personal choice.
- Finally ... If true performance is really desired it's not just weight that matters. If you really care about getting extreme performance (not likely for a bloated SUV, but let's be complete here) ... Aero matters too. In general, mainstream vehicle manufacturers don't spend a millisecond designing wheels with aero in mind. But take a look at Formula 1 wheels and you will see that open spokes have given way to much more sophisticated designs. This is what BBS offers today: https://cdn.gpblog.com/news/2022/01/...693124551d.jpg

BMinSFL

Thanks for the compliment and your input, I appreciate it! In my first post, it all started with improving the looks and it led to a pleasant surprise after a careful choice of tires that are slightly smaller but much lighter. Performance wasn't my initial goal.

The Macan is a commuter and from my seat on suburban roads, I noticed instant improvement in acceleration, response, steering feel and overall road-holding that made it closer to a sport sedan than SUV than I thought possible. With a bit more lowering, this would be the small sedan, baby Panamera GT that Porsche never made. This wasn't a one-time placebo, I switch between a 21" set of wheels every few weeks and notice the difference every time.

All subjective, I agree. I have some acceleration logs from when I was tuning the JB4 that I can compare to new logs I can take, hopefully that can offer some true performance data if desired but it's mostly a subjective measure.

I had a set of forged wheels lighter than the OE Spyders and didn't notice much difference but now with the lighter tires, I am still amazed at the difference for something as easy and overlooked as tires. Add a 7mm lower center of gravity and a slightly lower effective gear ratio for a numerically higher effective final drive and thats just a perfect, unexpected performance mod that started out with different intentions.

Again, it's all about the finesse and not going to extremes. I went with a slightly smaller size that is used by many OEMs, including on the Cayenne, to not disturb too much from the original specs. For my use, it works. For others, it may not, but I wanted to share my experience.
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I agree in terms of messing with the steering angles and scrub radius but keeping in mind the tires are a bit more narrow than OE spec, spacers are not actually messing with the total geometry as much as I would have thought. I have some toe plates I can use for comparative measurements vs. stock positions.

I have a love-hate relationship with spacers and typically end up ditching them. I'll see how it goes this time around. The car has a base suspension and I have messed with it already in terms of sway bars and springs. The result has been phenomenal and while I respect the Porsche / Audi engineering, the final showroom product is a compromise of many factors to please many types of buyers. I always end up dialing in the car to my uses and preferences, but ensure it remains at OE or OE+ levels of appearance and little or no NVH increases.

Again, thanks for your input and details, I'll check out your links as well.

BMinSFL

I think the best takeaway from that article, with relevance to this thread is:

"At 25.4 lbs, each tire weighs more than the wheel itself, and because it’s at the outer diameter of the rolling stock, its effect on rotational inertia will have a much larger effect than minor differences in rotational inertia within each wheel."

Btw it's interesting to see how far tires have come in 15 years. The 245/45/20 PS4S I have up front weigh less than the 255/35/18s used in that article.

Obviously you can't play with tires too much on every car but the Macan happened to have a bit of wiggle room due to the oversized tires on the 20" fitments. Even on the 21" fitment, when comparing to the BMW X4 M Comp, they use 255 and 265 vs. 265 and 295 widths. I happen to like the 21" OE Porsche sizes due to less/no sidewall bulge so I won't mess with that on my 21" set.

In the end, these are tires, a wear item, and I typically buy a new set each year. Its not as permanent as a new set of wheels so the ease of experimentation is what attracted me to this experiment. I am considering going to 255/45 and 285/40 for a bit more diameter/width, mainly for looks and less spacer but I will enjoy this setup for now.