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Discussion Starter #1
I am installing 13" 2000 Cobra R Brembo Front brake kit on my 95 GT

I had 17x9 17x10.5 Bullet wheels on it with Nitto NT01's. I am selling them to a friend because they wont fit due to the calipers.

Question is what wheels should i buy:

Thinking i still may need 14" brake kit in future cause i don't know if this kit is going to stop the car (552rwhp) I was thinking i would buy 18"s

is there a big performance gain due to weight of wheels?
like:

18x9 18x10 Saleen wheels
&
18x9 18x10 SSR or Volk

I need at least 18x10 or wider to get the power down what is the biggest that will fit?

the 17x10.5 has been working great

Any rims recomendations? I think i am going to buy Hoosier R6's for the first time ever how long should they live?

Thanks Fellas,
Jay
 

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For open track, I can't see any reason to get all spendy on wheels...the last 2-3 lbs a corner the Volks or SSR Comps will save means nothing, unless you are fighting for every 1/100 of a second...on the other hand, afaik, all Saleen wheels since the old Speedline made rims have been boat anchors (I haven't really looked at anything Saleen makes in years, so I could be way off base)...no reason to add an extra 5+ lbs of unsprung, rotational mass per corner, either. I'd think you could find something in between, maybe by OZ or Enkei, that would be a good compromise.
 

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yea like the decision i just made to go with the 15.9lb Enkei RPF1s 17"x9". you think the 9lbs lighter per wheel compared to a cobra R replica will be a noticeable difference? it should excelerate faster, and stop shorter.
 

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No, I don't think you'll notice any difference in the car's ability to "excelerate" or stop.

The RPF-01 is the type of light, cast wheel I was referring to, though, for the OP. Good bang for the buck and well proven design.
 

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Thinking i still may need 14" brake kit in future cause i don't know if this kit is going to stop the car (552rwhp) I was thinking i would buy 18"s

...I need at least 18x10 or wider to get the power down what is the biggest that will fit?

the 17x10.5 has been working great
552 rwhp will hardly tax the 2000R Brembo calipers with the right race pads and race rubber. Same with the going part. You don't need bigger wheels. You need real rubber. The stock Galpher pads Brembo's come with are okay but dusty as hell and not as capable as dedicated track pads (which means you must run race rubber because street tires will not handle the grip).
 

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^I'd agree. If the OP has to go to 18" rims to clear the calipers, maybe going to equal size (18X9.5" or 18X10" are pretty common sizes) all around and running 295/30-18 R6's makes sense, if there's no clearance problems up front. The 295 will work fine on as small as a 9.5" rim and running the same size all around makes it easier to manage tire wear.
 

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Doesn't mean it doesn't exist but all 17x9 mustang wheels I've heard of will clear the Brembo's. 18s aren't necessary. Its the width of the calipers that causes clearance issues with 17x8 wheels, with very few exceptions. Not the height of the caliper.
 

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No, I don't think you'll notice any difference in the car's ability to "excelerate" or stop.

The RPF-01 is the type of light, cast wheel I was referring to, though, for the OP. Good bang for the buck and well proven design.
I disagree with this statement - if he's saving 9 lbs per wheel, using the widely accepted adage that one pound of unsprung weight is roughly equivalent of eight pounds of sprung weight, that would be the same as removing 288lbs from the interior.

We can throw out some other adages - every 100lbs removed is equal to 100hp, 1" of brake rotor and 1" of tire width...

Increasing wheel diameter will have an exactly negative effect...you're moving the heaviest part of the wheel/tire combo (the bead and related tire-mounting area) farther outward from the center of the spindle. More energy wasted getting it moving and slowing it down. If at all possible run the smallest rims you can. This will offset some of his gain from the weight savings, but certainly not all of it.

Lightweight wheels were one of the modifications I found most beneficial on my cars. Whether you can feel it or not is up to the accuracy of your own butt dyno - whether it improves your lap times is a quantitative and important measure. Weight is the single most important modification variable on a road course - that's why most, if not all classes run in wheel to wheel competition have some type of major limiting weight factor not only power to weight ratio but a weight limit period. Weight makes the car work less hard to turn, accelerate, and decelerate - it makes it more predictable and easier to control doing all three, and it wears your parts down at a much smaller rate than a heavier car. You consume less fuel, less brake, less tire...
 

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I know one thing, I went from my POS saleen rims 18x9, roughly 30 pounds each to 17x10 ccw classics~~20-21pounds and I felt a big difference with responses (ie. braking, exit speed, etc)

What looks pretty doesn't mean its fast. There is a middle ground for reasonable price.
 

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I am ordering up a set of the RPF1's for my fox body in the 17x9's.
Like stated earlier they are only 15.9 pounds. I would imagine that would make a significant improvement. It would even help at the drag strip to, wich I don't plan on doing much of.
 

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Discussion Starter #11
wow great info fellas

only reason i was thinking i would need 18s was due to the 13" brembos would not be enough. I would rather have 17's due to tire price and less weight

i have been reading all over about lightweight wheel being better but (no real people have written an article talked about yes this is worth 2000 bucks for wheels)

i appreciate the info

so a better plan is either buy

lightweight
4 18x9.5's
or
17x9
17x10.5

with hoosiers

thanks again for great info
 

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wow great info fellas

only reason i was thinking i would need 18s was due to the 13" brembos would not be enough. I would rather have 17's due to tire price and less weight

i have been reading all over about lightweight wheel being better but (no real people have written an article talked about yes this is worth 2000 bucks for wheels)

i appreciate the info

so a better plan is either buy

lightweight
4 18x9.5's
or
17x9
17x10.5

with hoosiers

thanks again for great info
The enkeis in 17x9 are $250 a wheel @Tirerack, a bargain if you ask me..

You see them alot on 350z'z but they look good on a Mustang too.

 

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i was just looking at those wheels :) you have the sbc coating ? does that make them heavier?
That's not my car just one of the two fox's I could find pics of with these wheels. And I believe the weight is with the coating. People I autocross with that have these wheels swear by them.
Mine will be ordered next month when I get my bonus.
This is my car with Enkei V1's on it wich are pretty light but don't really fit the car.

And you can see I have 13" cobra front's and to am thinking of getting the Brembo 4 piston calipers.
 

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Discussion Starter #15

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Yeah I thought about those two. The thickness of the caliper is what you need to worry about. I would think that if a 03 cobra wheel will fit that any off the 22-20mm wheels would. Cobra R is a 24mm offset don't know how important those 2-4mm are..
 

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I disagree with this statement - if he's saving 9 lbs per wheel, using the widely accepted adage that one pound of unsprung weight is roughly equivalent of eight pounds of sprung weight, that would be the same as removing 288lbs from the interior.

We can throw out some other adages - every 100lbs removed is equal to 100hp, 1" of brake rotor and 1" of tire width...

Increasing wheel diameter will have an exactly negative effect...you're moving the heaviest part of the wheel/tire combo (the bead and related tire-mounting area) farther outward from the center of the spindle. More energy wasted getting it moving and slowing it down. If at all possible run the smallest rims you can. This will offset some of his gain from the weight savings, but certainly not all of it.

Lightweight wheels were one of the modifications I found most beneficial on my cars. Whether you can feel it or not is up to the accuracy of your own butt dyno - whether it improves your lap times is a quantitative and important measure. Weight is the single most important modification variable on a road course - that's why most, if not all classes run in wheel to wheel competition have some type of major limiting weight factor not only power to weight ratio but a weight limit period. Weight makes the car work less hard to turn, accelerate, and decelerate - it makes it more predictable and easier to control doing all three, and it wears your parts down at a much smaller rate than a heavier car. You consume less fuel, less brake, less tire...
Well, the extra rotational inertia of a heavier wheel or tire contributes to the effective linear inertia of the car, just like extra weight in the cabin would, as you said. But, the theoretical absolute upper limit (that I've been given by both MIT and Harvey Mudd engineering geeks) is 1 pound more at the surface of the tire tread contributes to inertia as if it were 2 pounds in the cabin, contrary to the old racer's myth. If you're talking about the wheel itself, the farthest out the weight can be added is the rim, again as you said. So, for an 18" rim with a 25" tire, the "bonus" weight drops from a maximum of 1 pound per pound to about 1/2 pound per pound. The bonus weight is less than that if it's not all concentrated at the lip.

So if you want a realistic estimate of how much weight savings you're going to realize for your money, multiply the weight loss from wheels by about 1.3-1.4. This is based on data that I've been given by true propeller heads and I'm talking about rotational mass (not unsprung weight), which is what is going to effect acceleration and braking, per the original post. I don't disagree, at all, that there are significant benefits in wheel control to be had in lowering unsprung weight...but even that benefit is muted on super smooth surfaces. btw, the only other really credible estimate I've ever seen regarding reduction in rotational mass vs. "cabin weight" is in Herb Adams' book, where he gives a 1:3 ratio, at the axle...which needs to be corrected for rim diameter and distance of total mass from axis, I believe.


For competition use, at the highest levels, it is an advantage and, like you said, you have to do everything you can...We did quite a bit of testing on the Z06, using both oem and CCW wheels (about 4lbs corner) and couldn't find any time that was consistent and repeatable, but that was autocrossing, where we only had 60 seconds per sample, not multiple minutes, like road racing.


btw, the Cobra R, I've been told by those that actually run them scale at 22#, so the weight difference is actually 6#. (edit: oops, that's for the 17X9" iirc)

And, finally, the butt dyno is the most inaccurate form of measurement...at least mine is, maybe some of you guys are more sensitive :)

So, yeah, you're absolutely right, imho, there's a reason why competitive race teams run the lightest wheels that provide sufficient strength. But, in the "real world", going with superzoomy, super light wheels isn't worth the money...again, imho. If you think about it, in terms of acceleration and braking, the weight of tires is actually more important.
 

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You're confusing two different concepts. When you add wheel diameter, your tire overall diameter is the same. But you just moved that weight further to the outside (like the crust on the pizza). We're talking about the forces of inertia in this case.

When we talk about the wheel's weight, we're talking about reducing unsprung weight and how that compares to sprung weight. The 1:8 ratio has to do with how removing unsprung mass minimizes the load placed on the controlling motion of the wheels and tires. When you ditch interior, you lose weight. When you ditch unsprung weight, you not only get the weight savings, you allow the suspension to do its job more easily. The suspension directly has to overcome the unsprung weight of the car to make any changes...the less unsprung weight you have, the less resistance the suspension has, and the quicker and more accurate adjustments it can make.
 

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You're confusing two different concepts. When you add wheel diameter, your tire overall diameter is the same. But you just moved that weight further to the outside (like the crust on the pizza). We're talking about the forces of inertia in this case.

When we talk about the wheel's weight, we're talking about reducing unsprung weight and how that compares to sprung weight. The 1:8 ratio has to do with how removing unsprung mass minimizes the load placed on the controlling motion of the wheels and tires. When you ditch interior, you lose weight. When you ditch unsprung weight, you not only get the weight savings, you allow the suspension to do its job more easily. The suspension directly has to overcome the unsprung weight of the car to make any changes...the less unsprung weight you have, the less resistance the suspension has, and the quicker and more accurate adjustments it can make.
No, I'm not confusing anything. The original question was relating to the benefit of lower rotational mass in terms of acceleration and deceleration. No mention was made of changing any of the variables that would effect the moment of inertia.

You've chosen to introduce some ratio, which I have no idea how you've arrived at (1:8), to attempt to quantify some type of overall "weight savings" attributed to reducing unsprung weight...which does confuse the hell out of me, because I have no idea what you're trying to say. f you're saying that less unsprung weight is beneficial to controlling wheel movement, I'd agree...but, that wasn't the question.
 
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