McQuickster

Alright, I was reading about conservation of angular momentum, and I think I might have been wrong here. Although there still should be a significant difference during actual acceleration. But i lost my credibility in the last post.

99C5Vert

eh, don't worry, I'm wrong at least once a day

Allthrottleandsomebottle

Depends on your intented use of the car......brake rotor size.......and budget...........we have a HRE 18/19 combo on our vert, 265/35/18 & 295/35/19.

Big tires in the rear that eat some power but..........the rake is and they do well on the autox course/drag strip. 18" tires are easier to find. I have 18" all the way around on the other 2 C5s.

As for numbers.........

The REAL WORLD RESULTS don't always equate to what the book says and very rarely are things "equal"...........I have tried all types of tires in all weather conditions/tracks on my cars..........
None of my C5s are stock........
Static and kinetic friction both result from the "stickiness" between
two objects. The origin of friction is not at all simple, and is the
subject of the field of Rheology. That is, one does not generally
derive the coefficient of friction, one measures it experimentally.
So that would make me an experimental driver

Wndotintman

[QUOTE=ALLTHROTTLE&NOBOTTLE;1558652468]Depends on your intented use of the car......brake rotor size.......and budget...........we have a HRE 18/19 combo on our vert, 265/35/18 & 295/35/19.


Street use only. I like to get out and play sometimes though. Brake rotors will probably stay stock size. Our roads are pretty crappy around here too.

Can you really see the difference between your C5s with 18s v/s 19s? Tough decision.....

Allthrottleandsomebottle

18s on all 4:


18/19.........I think the best shot to date to see the rake I spoke of:


Either CCW choice is a good one, John is
I have some CCWs, just for racin............kinda.......
How about 16/18........

JohnTheStigGalt

Great, so for those of you driving your car in space, wheel weights won't matter... For the REST of you, it will. Even in space, it's still going to make a difference on acceleration (just like every other piece of the rotating drivetrain). HP isn't measured at a constant speed.... No one cares what your HP is if you're already going 100 mpg... What matters is how fast you can get there. That's acceleration, and under Newton's 1st law and every other law of physics, weight will matter. Will 5 lbs per wheel make a HUGE difference? Not likely. Will 20? Yup. The real concern for most people is when they move from 17/18 to larger diameters... increase your wheel diameter by 2" AND add 5-10 lbs/wheel weight? Now you're talking a noticeable difference. The moment delta is exponentially proprotional to the force delta required to achieve an equal rotation rate. Add big brakes on top of that with something like the new C6 Z06 rotor which weighs a ton?? You give up A LOT more than 5 HP.

cruisemon

Actually you don't. You change the rate at which the power can be used or extracted. Maybe this analogy will help:

I have a 5-gallon pail full of water (400 horsepower). I attach a valve to it that has a one inch diameter opening (car with lots of weight). I open the valve and the pail empties at some rate (acceleration). I take the same pail and fill it up. It is still a 5-gallon pail (400 horsepower). I attach a different valve, this one with a two inch diameter opening (took off a lot weight from the car). I open the valve and now the pail empties FOUR times as fast (much faster acceleration).

Changing the valve size (weight reduction) did NOT change the size of the pail (horsepower). It DID change the rate at which I could remove the water (use the horspepower).

Charlie

Alex1217

Same here, before buying my SP500's (18x10 front, 18x11.5 rear) I purchased a set of repro wheels which the rears were about 7 pounds heavier each than stock. I certainly felt the difference immediately. During acceleration, I felt like I was towing something behind me. The vette even with my h/c package, just didn't feel as fast. It wasn't in my head because I had no prior knowledge that I would feel a difference before getting them. I sold them and got my SP500 package which is 10 lbs lighter overall (including tires) than stock. Once they went on, the vette felt like it should again.

If you are just leisurely driving around town, it probably won't make a difference but if you are into racing, hard acceleration and HP, you'll be able to feel the difference between a heavy wheel and a light one.

Dave68

The Tire rack does list wheel weight for some of their wheels. However, when I asked them if they know what the OEM wheels weigh, they told me, No! Forged wheels are generally lighter than equivelant-sized cast wheels, so buying forged seems to be the way to go. The key, though, is knowing what your baseline weight is for each wheel.

Another thing not mentioned is the weight difference between runflats and non-runflats. Each runflat is about 6 lbs heavier than a non-runflat and the extra weight is far from the wheel center.

Wndotintman

Tires are often overlooked in this subject . I was looking at 305/30/19 and noticed that a PS2 is 5 lbs lighter than a Bridgestone in the same size. That is alot of difference just in tires.

JohnTheStigGalt

Charlie, ONCE AGAIN, you're talking about flywheel HP... You're right -- that doesn't change. But there is clearly a LOSS of HP on every car on the planet when you compare flywheel HP to rear-wheel HP! Friction isn't the only factor, but it's the biggest. You'll often see car manufacturers giving both stats flywheel/rearwheel... You can argue semantics all day long. Your bucket analogy is just another way of saying that there's no loss in HP (potential engery of the water), just loss of the ability to "deliver" (the valve) the HP to the street. Well since that's how a dyno measures HP, there is effectively a reduction in the measureable HP to the street by increasing the rotational mass. The greater the weight, the more force is required, therefore your loss of HP as applied to the street (or a dyno) goes up. The engine itself isn't losing HP. In keeping with your bucket analogy, I could have said "You'd lose the ability to translate engine HP to the street resulting in a lot more than a 5hp reduction when measured at the wheels." But that's silly. You lose HP in the only way anyone measures it or cares about it -- how it moves the car. Again, a small weight delta on equal diamter wheels isn't going to change much (absent some bizarre wheel design the drastically shifts weight away from the axis of rotation). But a large weight delta or even small weight delta plus diameter increase does. And of course this doesn't even address all the other benefits of reducing unsprung weight not related to HP.

99C5Vert

FANTASTIC ANALYSIS

too bad you didn't read the question. here it is, with the important part highlighted. can't find that pesky "acceleration" thing you speak of.

cruisemon

The original post was whether or not wheel/tire weight changed horsepower. It changes the ability to use the horsepower or how the horsepower is applied but it does not change the horsepower. The discussion has never been about whether the car ran faster/quicker or not, it was about whether engine horsepower was increased or decreased by changing the weight of the wheels. As measured by a pulse dyno, the horsepower is different because of the measurement method, not because of a change in the engine.

I'm done here.

Charlie

JohnTheStigGalt

The original question was:

"Anyone dyno heavy wheels v/s [sic] lightweight wheels?" (Emphasis added).

Apparently neither of you 2 read the question. Maybe you thought he meant pulling his engine out of his car to dyno it that way. Problem is that wouldn't measure any effect at the wheels. The question by necessary implication is "What's the difference at the wheels..." HP on any dyno measured at the wheels measures the power of the engine, through the drivetrain, across the curve of RPM's... If you can figure out how to increase RPM's of the wheels WITHOUT accelerating, then you sir are a genius. Sadly, ya canna defy the laws of physics.

You're done here.

Vaughn

99C5Vert

Dude, it's pretty simple... On a chassis dyno, your output might be 305 HP @ 5700 RPM. That means you bring the car up to speed, then apply the load and roll on the throttle to keep it at 5700 RPM (notice you are not accelerating at this point - constant speed). At some point, you reach WOT and make the reading... still at 5700 RPM. You end up with a proper power number. Explain to me again how acceleration has anything to do with that reading

Allthrottleandsomebottle

By most maybe
I can speak to these:
My consolidated list of personal stock
Wheel size,type, & weight in lbs ea
OEM MAG 17 x 8.5, 17.5
OEM MAG 18 x 9.5, 19.5
OEM MAG 18 x 9.5 w/ new Yoko 295/35-18 AVS sport non-runflats, 50
OEM MAG 18 x 8.5 w/ new Yoko 275/35-18 AVS sport non-runflats, 46

PWO 5 spoke Y2K repos 17 x 8.5 +58mm, 20
PWO 5 spoke Y2K repos 18 x 9.5 +65mm, 23
HRE 18 x 9.5 545 w/ clear center +58mm, 22
HRE 18 x 12 545 w/ clear center +74mm, 27

PWO 17 x 8.5 +58mm w/ oem runflat 245/45/17 (8/32 tread), 50
PWO 17 X 8.5 +58mm w/ new MT ET Street 26 x 11.50 x 17 with TPS & lots of weights, 45
OEM MAG 17 x 8.5 w/ NITTO 555 275/40/17 (1/2 tread), 45
OEM MAG 18 x 9.5 w/ stock OEM 275/40/18 runflats, 53
OEM MAG 17 x 8.5 w/ stock OEM 245/45/17 runflats, 47
OEM MAG 17 x 8.5 w/ new MT ET Street Radial 275/40/17, 47
OEM MAG 18 x 9.5 w/ new Hoosier R3S05 275/35/18 road race radial 4.5 32nds tread with std valve stems 42

CCW drag pack rear 16 x 10 classic full polished with well worn MT ET Street 26 x 11.50 x 16 (1/32 tread) with center cap, 34

CCW drag pack front 16 x 5 classic full polished with like new Firestone deluxe champion 5.00/5.25-16 (10/32 tread) with center cap, 33

OEM runflat 275/40/18 worn to wear bars, 29
Bridegstone expedia S-01 345/35/18 (9/32 tread), 37
New MT ET Street Radial 275/40/17 (6/32 tread), 30
New MT ET Street 26 x 11.50 x 17 tires (6/32 tread), 25
OEM runflat 245/45/17 (8/32 tread), 29
BFG G-force drag radial 345/30/18 new, 30
BFG KDW2 295/35/19 new, 32
Yoko 295/35-19 AVS sport non-runflats (2/32 tread), 29

Topline 5 spoke Y2K repos 18 x 10.5 +58mm offset rims w/ new 275/35/18 BFG G-force TA drag radial, 53

Bob' House of Wheels 18 x 10.5 Chrome Y2K repos widened to 18 x 12. Work was done by Weldcraft Wheels.+56mm (with the 1.5" strip inserted, they should be right at 9.375" backspace, 31

HRE 18" x 12 545 w/ 345/30/18 BFG DRS, 57
HRE 18 x 9.5 545 w/ clear center +58mm w/ new 275/35/18 BFG KDWs, 52
HRE 18" X 9.5" 545 full polished w/ Yoko 265/35-18 AVS sport non-runflats (8/32 tread), 50
HRE 18" x 12 545 w/ 345/35/18 EXPEDIA S-O1 (9/32 tread), 64
HRE 19" X 10" 545 w/ Yoko 295/35-19 AVS sport non-runflats (5/32 tread), 58
HRE 19" X 10" 545 w/ new BFG KDW2 295/35-19 (10/32 tread), 61

AU N EGL

Weights of rotors

C5 & C6 stock front rotor = 17 lbs
C5 & C6 stock rear rotor = 11 lbs
C6 Z51 front rotor = 21 LBS
C6 Z51 rear rotor = 15 lbs

C6 Z06 front rotor = 27 lbs
C6 Z06 rear rotor ~ 22 lbs

Here are my wheels:

Street rear wheel CCW Classic Street 18x12 with 18x335/30 Mich PS = 51 lbs



Track rear wheel CCW Classic track 18x13 with 18x11.5x25.5 Good Year G19 or Hoosier 18x335/30 = 39 lbs


12 lbs difference per rear wheel or 24 lbs for rear wheels

fronts are 10 lbs differnce or 20 lbs

Track / racing wheels are 44 lbs lighter then street wheels

Street wheels dynoed ~ 400 rwhp
track wheels dynoed ~ 406 rwhp
( not done at the same time and on different dynos so differnce is questionable)

I do notice a difference when driving the two different set of wheels.

The other thing to consider when going to a lighter wheel is what is you inteded use??

If AT&NB went to a very light wheel for his rear drag set up, in theroy that would be great. In actuallity would the cars HP eventually break up the very light wheel??

I road race / track days. If I went to a thin spoked light weight wheel, again in theroy that would be great. In reality the latteral g-forces on the spokes of the wheel could crack a thin spoke wheel ( which I have seen ) where as the honey comb spoke of the Classic wheel has much more strength. The CCW Corsare wheel is slightly heavery then the Classic and has much greater latteral stregth.

Rember to ask yourself what is your inteded use for the wheels? Personnaly I think 19" rear wheels look but not for any type of racing.

1SG_Ret

https://mbworld.org/forums/c63-amg-w...orsepower.html

Verrückt ZR1

ElisTwoCents

Just cruising by bro