A pointless apples 'n oranges wheel weight comparison
11-22-2010, 12:25 AM
#1
Archive Gatekeeper
Rennlist Member
Rennlist Member
Thread Starter
A pointless apples 'n oranges wheel weight comparison
On a whim I decided to swap a set of 17" Cup 1's off the GT and onto the GTS to see how they would affect the ride. Decided to weigh everything, why not.
So the vaunted 16" CS rims with Avon M500s: So much for being lighter than 17" Cups with PS2's....
16" - total weight 190 lbs
17" - total wt 186 lbs
At least the 18" Cup 4's are still bricks (213 lbs):
So the vaunted 16" CS rims with Avon M500s: So much for being lighter than 17" Cups with PS2's....
16" - total weight 190 lbs
17" - total wt 186 lbs
At least the 18" Cup 4's are still bricks (213 lbs):
11-22-2010, 02:27 AM
#2
Race Director
When I did the math on my setup....I estimate my stock S4 rear wheels are 20lbs each since they are forged...the tires I run are between 22 or 26lbs (R comps are lighter) so that makes between 42 to 46lbs each or 168lbs to 184lbs..... I did hear the CS are around 18lb for the 8" and 19lbs for the 9"
11-22-2010, 01:40 PM
#3
Nordschleife Master
Rob,
That is VERY interesting! I had no idea they were that heavy! That the 17" are actually lighter shocks me.
Not surprised the 18" were heavier but just surprised the 16" weighed more than the 17"! I would think CUPII's would be even lighter because no tire pressure sensors!
That is VERY interesting! I had no idea they were that heavy! That the 17" are actually lighter shocks me.
Not surprised the 18" were heavier but just surprised the 16" weighed more than the 17"! I would think CUPII's would be even lighter because no tire pressure sensors!
11-22-2010, 01:52 PM
#4
When I swapped my manhole covers for my Cup 2's I can say just from lifting them in the garage the cups were slightly lighter. The 18" twist solid spokes I had for a while were quite heavy though.
11-22-2010, 01:55 PM
#5
Rennlist Member
guys, you guys are driving me crazy with this wheel weight stuff. ITS NOT THE diameter of the wheel that matters, its its construction. wheel for wheel, there is not a very measureable difference in the wheel weight WITH tire weight package. what you gain in wheel weight in material, you lose in tire weight and material, thus canceling each other out. (thats why you found that inconsistancy with the 16s vs 17s) * also providing that the same overall diameter is kept. also keep in mind that tire weight can be all over the map too. an old R3 hoosier will weigh 5 lbs less per tire than a toyo RA1 for example, only 2-3 lbs less with the new steel belted R6s. 
remember, rolling weight on the tire is worth about 2x as if that weight is in the car, vs 1.5 x if its on the wheel (generally). as far as straigth line acceleration effects.
remember, rolling weight on the tire is worth about 2x as if that weight is in the car, vs 1.5 x if its on the wheel (generally). as far as straigth line acceleration effects.
11-22-2010, 02:08 PM
#6
Rennlist Member
thats pretty interesting. keep in mind that the 17s R and the 16s R both weight the same, due to my points above. they both traded off rubber for wheel metal. dont know what happened with the fronts, being off a couple of lbs, but not a big deal. could have been tire construction
Now, the curious part is the 18s. are they porsche wheels? I think the GT and hollow spoke 17s are, right because they came off a GT and GTS respectively.
now, you guys find that SO interesting that the 18s are "pigs" Did anyone notice that you were comparing a 18" 295 vs a 255???????? Of COURSE its going to be heavier!! however the 235front weighed 2lbs more than the 245 and 255 17 /16" rears. (i.e. 50lbs vs 48.5lbs) ! this could have been tire weight alone, or those 18s might just be heavier wheels, but that has nothin to do with the size.
Do you want me to post a picture of my 335s on 18s on the scales??? 50lbs.
Now, the curious part is the 18s. are they porsche wheels? I think the GT and hollow spoke 17s are, right because they came off a GT and GTS respectively.
now, you guys find that SO interesting that the 18s are "pigs" Did anyone notice that you were comparing a 18" 295 vs a 255???????? Of COURSE its going to be heavier!! however the 235front weighed 2lbs more than the 245 and 255 17 /16" rears. (i.e. 50lbs vs 48.5lbs) ! this could have been tire weight alone, or those 18s might just be heavier wheels, but that has nothin to do with the size.
Do you want me to post a picture of my 335s on 18s on the scales??? 50lbs.
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11-22-2010, 03:18 PM
#8
Nordschleife Master
Mark,
You are right the POINT is that the CS wheels are forged and supposed to be light in weight. That is why it was a surprise to me that the cast 17" were actually lighter. Maybe the CS wheels are MUCH stronger. Though apparently the cast CUP I and CUP II wheels are strong enough...for street use anyway (though one might argue that as a great many of the are cracked.) My guess is if you ACTUALLY made a 17" CUP I or CUP II wheel as strong as a CS wheel it would weigh quite a bit more than the CS wheel.
Trading the wheel weight for tire weight is true, but rubber tires weight quite a bit less than dense metal...at least the last time I checked...I also did notice the width difference, but only on the rear of the CUP I vs CS wheel. The fronts were the same width.
You are right the POINT is that the CS wheels are forged and supposed to be light in weight. That is why it was a surprise to me that the cast 17" were actually lighter. Maybe the CS wheels are MUCH stronger. Though apparently the cast CUP I and CUP II wheels are strong enough...for street use anyway (though one might argue that as a great many of the are cracked.) My guess is if you ACTUALLY made a 17" CUP I or CUP II wheel as strong as a CS wheel it would weigh quite a bit more than the CS wheel.
Trading the wheel weight for tire weight is true, but rubber tires weight quite a bit less than dense metal...at least the last time I checked...I also did notice the width difference, but only on the rear of the CUP I vs CS wheel. The fronts were the same width.
11-22-2010, 04:47 PM
#9
Rennlist Member
they are forged because they are thin and need to be a little beefier because of that.
rubber doesnt weigh less than the metal used in wheels. (we dont use "dense" metals in rims, as they are usually alloys) want proof. my rim weighs 18.5lbs and my tires are betweek 25 and 30lbs. you would want to shave as much wheel weight as possible, but have some sidewall, thats why 18s are near optimal, and give a theoretical weight advantage, but the difference is slight, apples to apples.
The main point, to your comment, is that if you did make a 17" CS wheel, yes, it would weigh more, but would have less tire weight, so in the end, they would weigh near the same.
rubber doesnt weigh less than the metal used in wheels. (we dont use "dense" metals in rims, as they are usually alloys) want proof. my rim weighs 18.5lbs and my tires are betweek 25 and 30lbs. you would want to shave as much wheel weight as possible, but have some sidewall, thats why 18s are near optimal, and give a theoretical weight advantage, but the difference is slight, apples to apples.
The main point, to your comment, is that if you did make a 17" CS wheel, yes, it would weigh more, but would have less tire weight, so in the end, they would weigh near the same.
Mark,
You are right the POINT is that the CS wheels are forged and supposed to be light in weight. That is why it was a surprise to me that the cast 17" were actually lighter. Maybe the CS wheels are MUCH stronger. Though apparently the cast CUP I and CUP II wheels are strong enough...for street use anyway (though one might argue that as a great many of the are cracked.) My guess is if you ACTUALLY made a 17" CUP I or CUP II wheel as strong as a CS wheel it would weigh quite a bit more than the CS wheel.
Trading the wheel weight for tire weight is true, but rubber tires weight quite a bit less than dense metal...at least the last time I checked...I also did notice the width difference, but only on the rear of the CUP I vs CS wheel. The fronts were the same width.
You are right the POINT is that the CS wheels are forged and supposed to be light in weight. That is why it was a surprise to me that the cast 17" were actually lighter. Maybe the CS wheels are MUCH stronger. Though apparently the cast CUP I and CUP II wheels are strong enough...for street use anyway (though one might argue that as a great many of the are cracked.) My guess is if you ACTUALLY made a 17" CUP I or CUP II wheel as strong as a CS wheel it would weigh quite a bit more than the CS wheel.
Trading the wheel weight for tire weight is true, but rubber tires weight quite a bit less than dense metal...at least the last time I checked...I also did notice the width difference, but only on the rear of the CUP I vs CS wheel. The fronts were the same width.
11-22-2010, 05:30 PM
#10
Archive Gatekeeper
Rennlist Member
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Thread Starter
This is why the thread is titled both pointless, AND apples and oranges. No inference can be drawn about wheel weights or tire weights without dismounting the tires and weighing separately. I just thought it was interesting that the overall set of 16"s was heavier than the 17's. And the 18" wheels are cast aftermarket wheels, so even more appley and orangey.
I have some D90's in the garage too- between those and Mark's collection at 928Intl some day I'll weigh every factory wheel to within 2 grams and settle the issue.
I have some D90's in the garage too- between those and Mark's collection at 928Intl some day I'll weigh every factory wheel to within 2 grams and settle the issue.
11-23-2010, 01:33 PM
#11
Rennlist Member
I think an indication of this is the comparison of the 16 vs the 17" rear rim with the 245 vs 255 on the 17s. you know the style of the rim isnt that much of a deal, because the fronts were just the opposite as a weight result, but in the end, the 17 actually weighed the same,and probalby less than the 16s because it had a slightly bigger tire. this is because of the trade offs I listed.
11-23-2010, 06:12 PM
#13
Race Director
I have been researching 18" wheels for the 928 Estate...I found these
http://www.tirerack.com/wheels/Wheel...All&sort=Brand
18x10x65mm and quoted at 19lbs each.....very light for an 18" rim....add in about a 24lb tire and its the same weights as I run now....
http://www.tirerack.com/wheels/Wheel...All&sort=Brand
18x10x65mm and quoted at 19lbs each.....very light for an 18" rim....add in about a 24lb tire and its the same weights as I run now....
11-24-2010, 07:36 AM
#14
Racer
As I looked at that OZ wheels, I re-open the wheel fittment calculator and I wonder what was the alternative choice from wheel to alignment.
The real stuff for a 928 is the front wheel fittment with rubber. As I am looking for 18" wheel and 260 mm large rubber, I found that there was no big tire in clearanceand consequently, there will be a limitation of Camber adjustment.
So for those who regularly race there 928 what spread of camber angle are you using?
Best
Puyi
The real stuff for a 928 is the front wheel fittment with rubber. As I am looking for 18" wheel and 260 mm large rubber, I found that there was no big tire in clearanceand consequently, there will be a limitation of Camber adjustment.
So for those who regularly race there 928 what spread of camber angle are you using?
Best
Puyi
11-24-2010, 03:44 PM
#15
Rennlist Member
The front is most critical. the rears generally can be fit with spacers and some rolling, depending on the offset.
The fronts just need to be 10" with 8.5" backspacing or 9.5" with 8" backspacing.
camber for 928 race cars is in the 1.7 to 2 degree range and there is no benefit to going radical as there is with other types of cars, especially BMWs and 911s.
275s fit with NO problems with a little fender rolling (just the lip on the inside bent back) BUT, you need the right wheels. 260ish size are no issue at all.
The fronts just need to be 10" with 8.5" backspacing or 9.5" with 8" backspacing.
camber for 928 race cars is in the 1.7 to 2 degree range and there is no benefit to going radical as there is with other types of cars, especially BMWs and 911s.
275s fit with NO problems with a little fender rolling (just the lip on the inside bent back) BUT, you need the right wheels. 260ish size are no issue at all.
As I looked at that OZ wheels, I re-open the wheel fittment calculator and I wonder what was the alternative choice from wheel to alignment.
The real stuff for a 928 is the front wheel fittment with rubber. As I am looking for 18" wheel and 260 mm large rubber, I found that there was no big tire in clearanceand consequently, there will be a limitation of Camber adjustment.
So for those who regularly race there 928 what spread of camber angle are you using?
Best
Puyi
The real stuff for a 928 is the front wheel fittment with rubber. As I am looking for 18" wheel and 260 mm large rubber, I found that there was no big tire in clearanceand consequently, there will be a limitation of Camber adjustment.
So for those who regularly race there 928 what spread of camber angle are you using?
Best
Puyi