18" Wheels Factory vs. Aftermarket
06-20-2006, 01:29 AM
#11
4th Gear Member
Join Date: Apr 2006
Location:
Posts: 1,313
RE: 18" Wheels Factory vs. Aftermarket
I dont know if I would worry too much about it either way. If you are really into performance you may be swapping out the shocks and springs in either case anyway.
I am sure there are a ton of guys running 18"s on cars that came with 17"s. That was my intention but I found a car with the 18"s and liked it so I went with that given it was the only one like it in probably a 500 mile radius given the difficulty I had finding it.
I am sure there are a ton of guys running 18"s on cars that came with 17"s. That was my intention but I found a car with the 18"s and liked it so I went with that given it was the only one like it in probably a 500 mile radius given the difficulty I had finding it.
06-20-2006, 09:20 AM
#12
2nd Gear Member
Join Date: Apr 2006
Location: Dallas, TX
Posts: 245
RE: 18" Wheels Factory vs. Aftermarket
keep in mind that the 18" Oem wheels add about 5 pounds per wheel of unsprung weight. while 5X4 = 20 pounds doesn't sound like much, if you believe the addage that 1 pound of unsprung/rotating weight is equivalent to 10 pounds of sprung weight (because the engine has to overcome rotational inertia of mass in wheels, etc) then you are talking about a 200# effective weight difference by going with the larger wheels.
Not sure if I believe that rule of thumb 100%, but it's something to think about.
I upgraded my stock 17's for 18's, but spent a mint on light, multi-piece wheels to keep the unsprung mass at least as low as it was before. Not sure if it was worth it, but I think they look nice. [sm=smiley20.gif]
Not sure if I believe that rule of thumb 100%, but it's something to think about.
I upgraded my stock 17's for 18's, but spent a mint on light, multi-piece wheels to keep the unsprung mass at least as low as it was before. Not sure if it was worth it, but I think they look nice. [sm=smiley20.gif]
06-20-2006, 04:41 PM
#13
3rd Gear Member
Join Date: May 2005
Location:
Posts: 632
RE: 18" Wheels Factory vs. Aftermarket
I thought the "rule" of thumb was 1 pound rotational mass was equal to about 6-7 pounds of
regular mass (not 10 pounds as you listed).
I can tell you right now, that I've done several "tests" of this and on ALL my cars
I've switched out to lighter weight wheels and tires.
Weight drop on my other cars wheels/tires have ranged from 2 pounds (couldn't tell
really any performance difference) to 6.5 pounds (made the car feel more snappy and handle/steer
a bit better.
On a dyno, with the car that I've dropped 2.5 pounds per wheel/tire on, the car dynoed
about 2 additional hp.
There's no way dropping 5 pounds per wheel/tire is equal to dropping 200 pounds out of your car.
I could believe dropping 5 pounds per wheel/tire is equal to 120 pounds sprung mass lost (which would be
6 pounds for each 1 pound of rotational mass).
In any case, what it comes down to is that without question, losing rotational mass in your wheel/tires
improves your cars performance, so even dropping a pound or two can be helpful.
regular mass (not 10 pounds as you listed).
I can tell you right now, that I've done several "tests" of this and on ALL my cars
I've switched out to lighter weight wheels and tires.
Weight drop on my other cars wheels/tires have ranged from 2 pounds (couldn't tell
really any performance difference) to 6.5 pounds (made the car feel more snappy and handle/steer
a bit better.
On a dyno, with the car that I've dropped 2.5 pounds per wheel/tire on, the car dynoed
about 2 additional hp.
There's no way dropping 5 pounds per wheel/tire is equal to dropping 200 pounds out of your car.
I could believe dropping 5 pounds per wheel/tire is equal to 120 pounds sprung mass lost (which would be
6 pounds for each 1 pound of rotational mass).
In any case, what it comes down to is that without question, losing rotational mass in your wheel/tires
improves your cars performance, so even dropping a pound or two can be helpful.
06-20-2006, 06:33 PM
#15
1st Gear Member
Join Date: Jun 2006
Location:
Posts: 100
RE: 18" Wheels Factory vs. Aftermarket
ORIGINAL: classj
Definatly. I think that they are stiffer. And I wouldent be shocked in the least if someone told me the springs were slightly stiffer as well. It was a major difference. Much more than just a wheel/tire size upgrade.
In fact in the ford accesory book, they state that only 17" wheels should be used on cars that originally came with the 17" wheels. And only 18" wheels should be used on cars that came with the 18"s.
While I think ford is being drastic and most dealers would probably go against the rule. To me it shows that the wheels are not the only change when you order 18"s
Definatly. I think that they are stiffer. And I wouldent be shocked in the least if someone told me the springs were slightly stiffer as well. It was a major difference. Much more than just a wheel/tire size upgrade.
In fact in the ford accesory book, they state that only 17" wheels should be used on cars that originally came with the 17" wheels. And only 18" wheels should be used on cars that came with the 18"s.
While I think ford is being drastic and most dealers would probably go against the rule. To me it shows that the wheels are not the only change when you order 18"s
06-20-2006, 08:56 PM
#16
4th Gear Member
Join Date: Apr 2006
Location:
Posts: 1,313
RE: 18" Wheels Factory vs. Aftermarket
Not really. I have done +1 wheel size upgrades on quite a few cars (stangs, BMW's, porsches, musclecars) cars. They are never that drastic of a difference. And usually the swaps involved going from all seasons to max performance summer tires. Which the factory 18" wheels dont do.
There is something stiffer going on under there on the factory 18" cars.
There is something stiffer going on under there on the factory 18" cars.
06-21-2006, 01:28 AM
#17
5th Gear Member
Join Date: Nov 2005
Location:
Posts: 3,235
RE: 18" Wheels Factory vs. Aftermarket
ORIGINAL: Sonic Boom NH
I agree that the GT’S that come with the 18†wheels do NOT have softer shocks but rather stiffer shocks for a better handling car. I too drove a GT with 17†vs. 18†and it was night and day, the 17†GT had softer shocks, or a softer tuned suspension then did the GT with the 18†wheels…
I agree that the GT’S that come with the 18†wheels do NOT have softer shocks but rather stiffer shocks for a better handling car. I too drove a GT with 17†vs. 18†and it was night and day, the 17†GT had softer shocks, or a softer tuned suspension then did the GT with the 18†wheels…
06-24-2006, 04:31 PM
#18
Join Date: Jun 2006
Location:
Posts: 20
RE: 18" Wheels Factory vs. Aftermarket
I also have the GT Premium with 18 in. Factory wheels and drove the 17" in car and the car is much stiffer on the 18"s with a much better feel to the car.. I have really now idea if Ford or the the wheels make the difference but basically the stiffer sidewalls and the larger diameter is much better for me.
[IMG]local://upfiles/40670/D2661E4F579A443BB322C0A64A5915C9.jpg[/IMG]
[IMG]local://upfiles/40670/D2661E4F579A443BB322C0A64A5915C9.jpg[/IMG]
06-24-2006, 04:45 PM
#19
Join Date: Jun 2006
Location:
Posts: 20
RE: 18" Wheels Factory vs. Aftermarket
Not likely, the Ford replacement springs and shocks according to my dealership are the same so the wheel and tire make the difference and of course the 18"s are superior due to the smaller aspect ratio and thus feels better in handling. Although many dealerships will change out wheels and tires of course to get your money.
06-24-2006, 08:37 PM
#20
4th Gear Member
Join Date: Apr 2006
Location:
Posts: 1,313
RE: 18" Wheels Factory vs. Aftermarket
I have seen other makes of cars such as BMW, and other brands do similar things. On some BMW's, different wheel sizes from the factory have different shock valving. This is confirmed by BMW engineers at a club meeting at BMW NA.
HOWEVER, the replacment shocks sold at the dealers cover all wheel sizes sold under that model. This is done to reduce inventory supposidly.
I have seen this done with, for example chassis bushings. There might be 3 bushings on a car that are all the same size and are interchangable. But each one has a different durometer rubber spec'd to them. But due to inventory, there will be only one sold through the dealer over the parts counter.
HOWEVER, the replacment shocks sold at the dealers cover all wheel sizes sold under that model. This is done to reduce inventory supposidly.
I have seen this done with, for example chassis bushings. There might be 3 bushings on a car that are all the same size and are interchangable. But each one has a different durometer rubber spec'd to them. But due to inventory, there will be only one sold through the dealer over the parts counter.