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You mean "Golden Ratio". Based on the same underlying concept as the "Golden Section" numbers, but slightly different application (geometry vs. number theorem). But we got your point.
19" wheels are approximately 5% larger (diameter) than 18". Most would be hard pressed to tell them apart except by a side-by-side comparison.
I mean Golden Section- it is a term my professor used and it stuck with me but it makes no difference as the two terms are one and the same thing [along with several other names that describe the same thing].
For some weird reason the 19 inch wheels are exactly 1 inch greater in diameter than 18 inch wheels and when applying the plus one sizing concept one does not need to see them side by side to notice the difference as they stick out a mile with the obviously lower profile and tha tis the bit that for whatever reason just does not look right on the car from my point of view.
Lower profile TIRES was up to now not part of the 19" WHEEL discussion. This is another topic. Also how far one can derivate from the factory 25" wheel/tire diameter without running into issues is again another topic.
I don’t want to come across as a know-it-all because I don’t.
- Didn't know that I would have to bent the inner lips on my 944 to make the 19" fit, which in turn, required a not planned paint job on all four wheel fenders ($$$).
- Didn't know that 285mm tires don’t protect well the wheels from curb contact, resulting in curb rashes. 295mm tires should fit, which would mitigate curb rashes, but don’t know that for certain (that's why I went with the 285mm). 305mm would be even better for that, but probably won’t fit.
- Didn't know that I still will have clearance issue in the rear when the children are in the car and I make a sharp turn.
- Didn't know I will have a string of steering rack failures, probably partly due to the heavier and wider wheel/tire up front.
However, I had no such problems with the 19" on my 928 GTS. Bought my Carrera Classic used together with low-profile tires. When I will need new tires will try to go with a bit more side profile. (Would 26" wheel/tire diameter work on a 928 GTS?)
We could get into a discussion of principle of Psychophysics (perceptual science). What parameter is the (more) relevant one.
I would argue that with wheels it is not (surface) area but linear dimension. For example, wheels get advertised on their linear dimension (diameter), not (surface) area. Visible surface area of a wheel is also strongly depended on the design of the wheel.
That's it, I'm done. Apparently you'll argue just for arguments sake.
That's it, I'm done. Apparently you'll argue just for arguments sake.
Changed my reply. Don't want to come across as too adversarial.
19" too big for the 928 is also a question of personal perception. See many cars here (South Florida) with IMO way too big and flashy wheels. They would be laughing us thinking 19" are big wheels.
Lower profile TIRES was up to now not part of the 19" WHEEL discussion. This is another topic. Also how far one can derivate from the factory 25" wheel/tire diameter without running into issues is again another topic.
I don’t want to come across as a know-it-all because I don’t.
- Didn't know that I would have to bent the inner lips on my 944 to make the 19" fit, which in turn, required a not planned paint job on all four wheel fenders ($$$).
- Didn't know that 285mm tires don’t protect well the wheels from curb contact, resulting in curb rashes. 295mm tires should fit, which would mitigate curb rashes, but don’t know that for certain (that's why I went with the 285mm). 305mm would be even better for that, but probably won’t fit.
- Didn't know that I still will have clearance issue in the rear when the children are in the car and I make a sharp turn.
- Didn't know I will have a string of steering rack failures, probably partly due to the heavier and wider wheel/tire up front.
However, I had no such problems with the 19" on my 928 GTS. Bought my Carrera Classic used together with low-profile tires. When I will need new tires will try to go with a bit more side profile. (Would 26" wheel/tire diameter work on a 928 GTS?)
.
The width of the tyre has nothing to do with curb rash and everything to do with the specific tyre design. For structural reasons tyre width has to be matched to rim width within certain range limitations. Continental provide tyre designs with excellent "shoulders" that protect the rims very well indeed but my experience with Pirelli suggests otherwise, especially on my Cayenne Turbo S where any contact however minor causes paint rash.
The 928 can tolerate a rolling radius of 26 inches on the rear- I am currently running a 285x35x18 section on the rears that has a rolling diameter of 25.8 inches. This with 255x35 on the front that gives a 25 inch diameter, previously when tracking I was running a 265x35 up front at 25.4 inch diameter.
Fitting wider rims and tyres to a car is more complicated than most seem to realise and the 928 is no exception- far from it. Every 18 and 19 inch rim has to be low profile so it is very much part of the discussion- just a question of how one defines low profile which as far as I am concerned implies a type of aspect ratio 50 or less. Most people do not seem to realise that there is a difference between something that fits and something that actually works!.
Running a 19 inch rim and maintaining a 25 inch rolling diameter requires very low profile rubber which in turn as very stiff sidewalls and the downside of that is harsh suspension and rims that are likely to fail on the first serious pothole they hit. No problem on racetracks but on poor quality roads? I have never come across a 19 inch rim that has the correct front offset [65mm] but I dare say they exist if formed from a three piece forged centre construction but anything that came off a 911 will have an incorrect front offset just to add insult to injury. Many people run such offsets but personally I prefer the NSR that Porsche wisely designed into the suspension.
Bigger diameter/wider wheels are not necessarily heavier but if they are cheap then they are. My 3 piece forged centre 18 inch rims are lighter than the Stock S4 or GTS rims but if they were one piece cast they would invariably be heavier.
The width of the tyre has nothing to do with curb rash and everything to do with the specific tyre design.
With a 295mm tire on a 11" width wheel, there is a bit of a rubber bulge overhang that offers some protection against curb rashes. There is no such overhang with 275mm or 285mm tires.
There is no such thing.
Wheels come in absolute width dimensions, that is a formula for tire size ratio and not all tires of the same "size" are actually the same "size" when measured. This is why when trying to squeeze the most tire onto a car, section with & installed width must be looked at along with that ratio.
I've measured up to a full inch difference in width between tires of the same size on the same wheel. Yes they were different brands.
12-11-2017, 09:22 AM
