Question: Does Light Wheels = Weak Wheels

[Gary in NJ]

Originally Posted by Shutter

I was skeptical on the 17 vs 18 thing too...Go 18", you wont regret it.

No doubt, that set up looks great. Really great.

The reason I want to stick with 17's is that I'm trying to preserve as much sidewall as possible to retain a comfortable ride. I'm a lot older then many of my fellow -86 enthusiasts and my old bones need to be driven is some semblance of comfort.

[CSG Mike]

Originally Posted by Gary in NJ

I'm considering installing Enkei RPF1 wheels on my daily driven BRZ. The size I'm interested in (17x8 +35) weigh in at a very light 16.10 pounds each. This is a significant weight reduction in sprung weight from the factory wheels. However I have concerns that I may be choosing a wheel that will not be able to withstand the abuse of public roads.

Is the weight of a wheel any indication of its robustness?

I've bent/destroyed/shattered my share of wheels on track. The quick answer is: No. However, cost is not an indication of robustness either. The only real way to get an answer is to do research on the particular wheels you're interested in.

If you avoid potholes, chances are, you'll never bend your RPF1 to the point where they can't be repaired.

[mav1178]

Originally Posted by Gary in NJ

This is a significant weight reduction in sprung weight from the factory wheels.

Sorry to correct, it's unsprung weight.

[ame="http://en.wikipedia.org/wiki/Unsprung_mass"]Unsprung mass - Wikipedia, the free encyclopedia[/ame]

Kind of a big deal for me... my last license plate in CA was "UNSPRNG"

-aex

[ayau]

Originally Posted by CSG Mike

I've bent/destroyed/shattered my share of wheels on track. The quick answer is: No. However, cost is not an indication of robustness either. The only real way to get an answer is to do research on the particular wheels you're interested in.

If you avoid potholes, chances are, you'll never bend your RPF1 to the point where they can't be repaired.

Can I infer and say that running expensive forged wheels at the track isn't worth it? The cost to replace a forged wheel isn't worth the extra 1-2lbs in weight savings.

You can almost treat wheels as a consumable when you track your car, right?

[CSG Mike]

Originally Posted by ayau

Can I infer and say that running expensive forged wheels at the track isn't worth it? The cost to replace a forged wheel isn't worth the extra 1-2lbs in weight savings.

You can almost treat wheels as a consumable when you track your car, right?

I've yet to bend any Rays or BBS wheels.

I can't speak for any other forged wheels (looking at basically any two/three piece forged wheels from HRE, CCW, etc.; these are machined out of forged ingots, and are not of the same quality as BBS/Rays)

Just remember who provides wheels to pro level racing: OZ, Enkei, Rays, and BBS. Coincidence? Probably not.

[mav1178]

Originally Posted by ayau

You can almost treat wheels as a consumable when you track your car, right?

You can..... if you also treat your car as a consumable at the track.

The chances of a true forged wheel to have a catastrophic failure versus a semi-forged/cast wheel having the same failure, is a lot less.

More engineering/testing and refined manufacturing processes don't translate to faster lap times. They translate to more safety when something happens beyond design limits.

-alex

[ayau]

Originally Posted by mav1178

You can..... if you also treat your car as a consumable at the track.

The chances of a true forged wheel to have a catastrophic failure versus a semi-forged/cast wheel having the same failure, is a lot less.

More engineering/testing and refined manufacturing processes don't translate to faster lap times. They translate to more safety when something happens beyond design limits.

-alex

You bring up a good point regarding safety. Most people just think of shaving lap times with lightweight wheels.

[mav1178]

Originally Posted by ayau

You bring up a good point regarding safety. Most people just think of shaving lap times with lightweight wheels.

Want to shave lap times?

Invest the money spent on a nice set of forged wheels, and take some true driving lessons at the track with a professional racing school.

Most people mod and race in canyons or on public roads... not knowing how to control their cars.

-alex

[wheelhaus]

Originally Posted by Gary in NJ

No doubt, that set up looks great. Really great.

The reason I want to stick with 17's is that I'm trying to preserve as much sidewall as possible to retain a comfortable ride. I'm a lot older then many of my fellow -86 enthusiasts and my old bones need to be driven is some semblance of comfort.

Sidewall height is only one element in ride quality and tire performance, especially considering a tire's construction design can vary a lot. From a 17" tire, an identical 18" tire (same OD) will technically have a stiffer sidewall purely by virtue of it being shorter, but that doesn't mean the 18" tire will perform better. 17" tires can still have extremely stiff sidewalls, but this goes both ways as they can also have soft spongy sidewalls with nearly zero reinforcement for lateral loads (such as a snow tire, for instance)... In this respect, you can have a very comfortable 18" tire, and a very harsh 17" tire. On the other extreme, look at how tall the sidewall is on a F1 car, it's huge! It's extremely stiff, but engineered specifically for the application.

18" wheels on the 86 will not improve performance in any way over a comparable 17" wheel. In fact, they typically make the car slower. Larger wheels are typically heavier, and anything that adds rotational weight will slow acceleration to some degree. This has been proven with a stock car, where wider 17's hurt lap times (due to extra wheel/tire weight) and 18's also hurt lap times, a bit worse I believe. The only thing that actually improved lap times were either much grippier tires, or much lighter 17's with grippier tires. A wider 17" wheel that is the same weight as the stock wheel will ultimately weigh more in the end, simply buy virtue that is uses a wider tire.

Also, a wider wheel may have similar weight to another narrower wheel, but the wheel's design is a very critical element. If it has a wider rim, then it may still require more energy to accelerate because more mass is located farther from center. This isn't always the case, but something to consider beyone simple weight comparisons.

[Gary in NJ]

Dave,

You bring up very valid points. The choice of wheel and tire is a trade-off and potential compromise on many fronts. Not mentioned in your reply are the effects of a wider tire on turn-in (front) and rotation (rear) which can adversely effect the fine handling qualities of the -86 platform.

At this point I'm still trying to figure out the (or rather, my) "Goldilocks" configuration. I want to stay with 17" rims for the reasons you mentioned above. I want to go with an 8" wide rim to accommodate 225 section width tires (perhaps even a 245/40 when I install a SC). And I'd like to go with a +35 off-set for looks...I know that's the wrong reason but I do like the look of a flush fit. I believe I can accomplish all of the above and still loose 2 to 3 pounds per wheel/tire and maintain the fine balance of the -86.

[ayau]

For stock power, I think 17x8 is a good balance between grip and weight. A lot of track guys run that configuration right now.

[yoshiharadesign]

18" allow for bigger brakes which you would need to consider once you have the s/c system. Because ultimatley, even though you dont want to unbalance existing set up, adding power brings a whole additional list of variables that will require bigger brakes hence bigger wheels and tires along with other components to strengthen the chassis to cope with added power. Besides, when the power comes in, the unsprung weight difference will be less noticeable vs to a factory stock set up. The key is to remember what the end game would be on the car. Weve seen many consumers buy 2 sets of wheels because they have issues putting on bigger brakes on stock wheels... Its great for the wheel business but not necessarily good for the consumer... As indicated before, its all about trade offs and compromises. A good article from car and driver on bigger wheels and tires http://www.caranddriver.com/features...d-tires-tested It shows what you give up on acceleration and fuel economy you gain in grip along with shorter stopping distance. Now imagine adding power to the mix and the deficits of the slower acceleration are erased. Of course, wider 17" might be a solution but wider will still give the same effect as 18" because instead of adding weight in diameter, you are adding weight in width...

[feldy]

If you are not doing 17s because of brake upgrades just look through the build threads. While there are some doing them. The majority has not. And if you give us the right offset like the 17x9 +35 rpf1 we won't have issues.

[yoshiharadesign]

Originally Posted by feldy

If you are not doing 17s because of brake upgrades just look through the build threads. While there are some doing them. The majority has not. And if you give us the right offset like the 17x9 +35 rpf1 we won't have issues.

wheel size also would be dependent on how big diameter of brakes and caliper set up that would be put on the vehicle. That would determine if a 17 diameter wheel will still fit or not.