The influence of wheel weight on ride quality
#32
Originally Posted by 58spdstr
Tire brand and age also affect ride quality. Some brands have much stiffer sidewalls at the same aspect ratio (Bridgestone being one) and transmit more surface irregularity to the suspension. As you wear tread, and rubber ages you are likely to also notice (feel and hear) a difference.
I find the Bilstein PSS set up with Michelin PS2's to be very comfortable in the normal mode for most everyday use. I think the PSS with PASM adjusts infinitely as you drive (the point of active suspension management) with a slightly different baseline in the sport mode and more frequent updates of conditions from the computer to the damper. So if you drive aggresively in normal mode, it will stiffen up. I drove an entire track session in "normal" after forgetting to hit the sport button and noticed no major difference in how I got around the track.
All things equal, less unpsprung weight imprvoves performance as noted.
I find the Bilstein PSS set up with Michelin PS2's to be very comfortable in the normal mode for most everyday use. I think the PSS with PASM adjusts infinitely as you drive (the point of active suspension management) with a slightly different baseline in the sport mode and more frequent updates of conditions from the computer to the damper. So if you drive aggresively in normal mode, it will stiffen up. I drove an entire track session in "normal" after forgetting to hit the sport button and noticed no major difference in how I got around the track.
All things equal, less unpsprung weight imprvoves performance as noted.
#33
Originally Posted by blakt out
After having a really hard car, I disagree with you. I doubt seriously that how aggressively you drive validates an uncomfortable suspension. The cars are very capable from the factory. Just my 2 cents... which I get to give freely 'cause I started this thread.
Anyway, I track my car, and think I'm a decent driver. Have my SCCA license and all that. I want to soften it up a smidge because it's so uncomfortable on bumpy NC roads. I'll do like was previously mentioned and work on softening up my Bilstiens and the ride height.
Just wondered if, ceterus parabus (all things equal) if a lighter wheel would feel softer than a heavier wheel. That's the point of the thread.
Anyway, I track my car, and think I'm a decent driver. Have my SCCA license and all that. I want to soften it up a smidge because it's so uncomfortable on bumpy NC roads. I'll do like was previously mentioned and work on softening up my Bilstiens and the ride height.
Just wondered if, ceterus parabus (all things equal) if a lighter wheel would feel softer than a heavier wheel. That's the point of the thread.
#34
Easy answer -- you need 18" wheels to clear the brakes. 18's aren't just the best for the track, they are the best for any 997... period. If you want the facts, do a search here and at RL and you'll find the quotes from the engineers, Porsche insiders, writers from all car magazines, race car drivers that compared 18s and 19s on the 997, etc. It's well known that 20's handle and ride worse than 19s, which handle and ride worse than 18s... If you happen to like the looks, then that's fine -- just don't discount reality and the original question of the poster.
Originally Posted by dmoney
Yeah who's road and track, lol alpine your right again, i think we should take a poll of how many 6speeders track their cars? i mean sure all track guyz will vouch that 18's are the best FOR TRACKING... but why not 17's or 12 fuchs I mean all I can say is that Im happier with the new handles and looks of my Blingy 20's what more could you want...
#35
Have 20's on my 997S. Don't notice much if any ride difference. Additionally noticed no difference on my 0-60 or 1/4 mile times using my GTech meter, in fact my best 0-60 time was with the 20's. This is based on my results, not just something someone has heard.
Has anyone weighed their wheels? My 20" rears with 305's come in at 58.5lbs. That not much more than stock, only 2-3 lbs difference.
Has anyone weighed their wheels? My 20" rears with 305's come in at 58.5lbs. That not much more than stock, only 2-3 lbs difference.
#36
A million things can change performance from day to day... Temperature, humidity, etc. You can run 0-60 10 times and get different readings. Physics, however, is physics.
My oem 19s are 44 lbs front, 53 lbs rear. My Fikse 18s with RA1s are 41 / 45 lbs respectively. With PSCs those figures would be less. 1 lb of unsprung weight (wheels/tires) is equivalent to about 1 hp of gain / loss -- so 58.5 lbs vs. 45 is as though I have 13.5 hp more. May not seem like much, but who wants less performance in a Porsche?
As for ride difference, I can tell you this, that the handling and ride increased substantially when I went from 19 to 18, as all of the reports, articles, etc. suggest.
My oem 19s are 44 lbs front, 53 lbs rear. My Fikse 18s with RA1s are 41 / 45 lbs respectively. With PSCs those figures would be less. 1 lb of unsprung weight (wheels/tires) is equivalent to about 1 hp of gain / loss -- so 58.5 lbs vs. 45 is as though I have 13.5 hp more. May not seem like much, but who wants less performance in a Porsche?
As for ride difference, I can tell you this, that the handling and ride increased substantially when I went from 19 to 18, as all of the reports, articles, etc. suggest.
#37
How crazy is it that 18s are now 'little'? Like, the old 14s or so.
So do any of you have pics of 18s on your 997? I honestly can't get my head around that. Don't know why. Right now I think I'm just thinking about going to a very light 19. Thing is, all the ultra lights are one piece. Get curb rash and you're screwed.
So do any of you have pics of 18s on your 997? I honestly can't get my head around that. Don't know why. Right now I think I'm just thinking about going to a very light 19. Thing is, all the ultra lights are one piece. Get curb rash and you're screwed.
Last edited by blakt out; 08-14-2007 at 10:14 PM.
#38
Originally Posted by RonCT
A million things can change performance from day to day... Temperature, humidity, etc. You can run 0-60 10 times and get different readings. Physics, however, is physics.
My oem 19s are 44 lbs front, 53 lbs rear. My Fikse 18s with RA1s are 41 / 45 lbs respectively. With PSCs those figures would be less. 1 lb of unsprung weight (wheels/tires) is equivalent to about 1 hp of gain / loss -- so 58.5 lbs vs. 45 is as though I have 13.5 hp more. May not seem like much, but who wants less performance in a Porsche?
As for ride difference, I can tell you this, that the handling and ride increased substantially when I went from 19 to 18, as all of the reports, articles, etc. suggest.
My oem 19s are 44 lbs front, 53 lbs rear. My Fikse 18s with RA1s are 41 / 45 lbs respectively. With PSCs those figures would be less. 1 lb of unsprung weight (wheels/tires) is equivalent to about 1 hp of gain / loss -- so 58.5 lbs vs. 45 is as though I have 13.5 hp more. May not seem like much, but who wants less performance in a Porsche?
As for ride difference, I can tell you this, that the handling and ride increased substantially when I went from 19 to 18, as all of the reports, articles, etc. suggest.
Last edited by JohnnyD; 08-15-2007 at 12:21 AM.
#39
If all this is true that 18's are the best then why did porsche it's self go with 19's on their most prize possession.... the 997. I mean the new gt2 will have 19's right. I will bet that the new 998 will feature 20's then what will all say????
#40
Originally Posted by dmoney
If all this is true that 18's are the best then why did porsche it's self go with 19's on their most prize possession.... the 997. I mean the new gt2 will have 19's right. I will bet that the new 998 will feature 20's then what will all say????
#41
Big wheels on new cars due to customer demand (bling) and to get over big brakes (see Ron's post above).
Geez people, this is not a complex answer to the original question. See, by way of example, http://en.wikipedia.org/wiki/Unsprung_weight
"The amount of movement is inversely proportional to the weight - a lighter wheel which readily moves in response to road bumps will have more grip when tracking over an imperfect road. For this reason, lighter wheels are often sought for high-performance applications. In contrast, a heavier wheel which moves less will not absorb as much vibration; the irregularities of the road surface will transfer to the cabin through the geometry of the suspension and hence ride quality is deteriorated."
Geez people, this is not a complex answer to the original question. See, by way of example, http://en.wikipedia.org/wiki/Unsprung_weight
"The amount of movement is inversely proportional to the weight - a lighter wheel which readily moves in response to road bumps will have more grip when tracking over an imperfect road. For this reason, lighter wheels are often sought for high-performance applications. In contrast, a heavier wheel which moves less will not absorb as much vibration; the irregularities of the road surface will transfer to the cabin through the geometry of the suspension and hence ride quality is deteriorated."
#42
The history of 19s on the 997 is well documented on the web (this forum and Rennlist for example). The car is designed for 18s, which is why they are standard on the 997. When you option up to the S, you get the otherwise optional 19" wheels. Porsche engineers have admitted (international press) that the car is "best" with 18s, but that the marketing department pushed hard and thus instead of delivering S and GT cars with 18s, they put on the otherwise optional 19s. The oem 18s fit just fine over even the bigger brakes on the S, but bling is in so the 19s became part of the package.
#44
As stated, tire diameter is the same for 18, 19, and 20" wheel applications. The front on a 997 is about 25.5" and the rear about 26.3". What that means is that with the outside diameter being constant, what you end up with is less and less sidewall as you go from 20" to 19" to 18". As engineers report, there is a falling off of benefit of a stiff sidewall. You want some flex so that your tire somewhat conforms with the pavement vs. being so stiff and hard as to be lock a hockey puck, which would just skip across anything imperfect. As R&T engineers explain (as do others), there's a ramping up from 16 to 17 to 18, which really is about the pinnacle of grip and ride, then a falling off as you go to 19 and even worse 20. With this falling off comes a much worse ride, less grip (as outlined), more potential for damage (less sidewall to absorb impact from potholes, etc.), and on and on.
It appears the media convinced some that bigger wheels is cooler, some wheel makers saw the opportunity and made them, but those sources are not explaining the downside, which probably explains why I keep hearing of people buying 20s and getting rid of them (or 19s and changing to 18).
It appears the media convinced some that bigger wheels is cooler, some wheel makers saw the opportunity and made them, but those sources are not explaining the downside, which probably explains why I keep hearing of people buying 20s and getting rid of them (or 19s and changing to 18).
#45
Tires will make a huge difference in comfort and ride quality . So far the best in my opinion is the Michelin pilot sport 2 . The wheel weight will also make a small difference .You can keep the 20" wheels and simply change to a lightweight forged 20" wheel . Champion has a few and HRE is in the process of making a new 1 pc forged wheel that is very light .Wheel weight is unsprung weight so it will also make your feel quicker .
I thought i read you wanted to sell your car w/ the supercharger how much do you want for it ? Kinda too late i bought a 06 c4s last week .I will be loading pictures soon . sport seats painted white ; white console and trim ; illuminated door sills , etc...
I thought i read you wanted to sell your car w/ the supercharger how much do you want for it ? Kinda too late i bought a 06 c4s last week .I will be loading pictures soon . sport seats painted white ; white console and trim ; illuminated door sills , etc...