Lighter 17's anybody?

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13' CX-5 and 16' Mazda6 both Touring w/Tech/Bose
Hello all. New member here thats been lurking for 2 weeks attempting to get a feel for the all new CX-5. This is my wife's vehicle as I own a 2013 Volkswagen CC however I drive the CX-5 on occasion. The CX-5 is really impressive considering it's a CUV that isn't low to the ground. I'd like to improve the existing handling characteristics without sacrificing comfort since this is my wife's car. Lowering springs/coilovers are out of the question for her. 19-20+ inch wheels look nice but adding more weight on an automatic 150hp vehicle doesn't make sense from a performance stand point imo (no disprespect to anyone). Plus with bigger wheels comes bigger heavier tires.

Then I thought about retaining the stock 17inch size tires and replacing just the stock 20+lb oem 17 inch wheels with some super light 14-16lb 17inch wheels. I figure losing 4-6lbs of rotational mass per wheel would provide a noticeable difference. I'd like to know what you guys think.
 
Can't go wrong for RPF1's. One of the best non-forged options for the money. Extremely light and strong spun cast wheels. Though I would go for something wider than 17x7. 17x8 at the very least.

If you go with a bigger diameter wheel (E.G. 18"), just go with a smaller spec aspect ratio. Use this calculator for tire shopping.

http://www.miata.net/garage/tirecalc.html
 
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Can't go wrong for RPF1's. One of the best non-forged options for the money. Extremely light and strong spun cast wheels. Though I would go for something wider than 17x7. 17x8 at the very least.

If you go with a bigger diameter wheel (E.G. 18"), just go with a smaller spec aspect ratio. Use this calculator for tire shopping.

http://www.miata.net/garage/tirecalc.html

The link was informative. The drawback of getting just 1 more inch larger diameter was an increase of anywhere from 3 to 4 lbs I noticed. Add to the fact a just 1 inch larger and/or wider tire weight would increase by no less than 3 lbs as well. However, the link is a good guide should someone seek to go larger diameter. I may just go up to 18 or 19 so I'll keep this link in my favorites.
 
I did...pulled a stock tire/rim and the shipping scale said 47lbs IIRC. Guess I can go back and find the post a few weeks ago, and edit if I got it wrong. Anyway, they aren't bad for stock... I have my eye on a set of 18s that will weigh the same as stock... or even drop a couple pounds with a careful choice of tire. With 20s you have to spend a ton to get a light enough rim to keep it at stock weight.

I wonder how the stock 19s compare to the 17s?
 
The NC Miata/MX-5 17x7 10 spoke (+55 offset) is only 17.0 pounds. I lost 3 pounds per corner on my 5 even with a wider wheel and heavier tire by using the MX-5 wheels.

mx5_wheel_sm_2.jpg


Just throwing that out there as an OEM option that you can find every now and then used on Craigslist.
 
Oh, and these in a 17x9 +63 are less than 18 pounds each- $216 each at Discount Tire before coupons and promos.

s2k_wheel_clearance_02.jpg
 
The NC Miata/MX-5 17x7 10 spoke (+55 offset) is only 17.0 pounds. I lost 3 pounds per corner on my 5 even with a wider wheel and heavier tire by using the MX-5 wheels.

mx5_wheel_sm_2.jpg


Just throwing that out there as an OEM option that you can find every now and then used on Craigslist.
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you put the MX-5 wheels on your CX-5?
What kind of MPG are you getting now?
 
has anyone weighed a stock 17" wheel yet?

At least 20lbs imo.

I did...pulled a stock tire/rim and the shipping scale said 47lbs IIRC. Guess I can go back and find the post a few weeks ago, and edit if I got it wrong. Anyway, they aren't bad for stock... I have my eye on a set of 18s that will weigh the same as stock... or even drop a couple pounds with a careful choice of tire. With 20s you have to spend a ton to get a light enough rim to keep it at stock weight.

I wonder how the stock 19s compare to the 17s?

Your weight of the tire/wheel comb is at 47lbs.....The stock 17 tires are 27lbs per tireracks website. Thats how I based the oem 17 inch wheel's weight to be around 20lbs. I bet the 19s weigh around 25-27lbs.

The NC Miata/MX-5 17x7 10 spoke (+55 offset) is only 17.0 pounds. I lost 3 pounds per corner on my 5 even with a wider wheel and heavier tire by using the MX-5 wheels.

mx5_wheel_sm_2.jpg


Just throwing that out there as an OEM option that you can find every now and then used on Craigslist.

Thanks this helps alot. Those Miata wheels are a good option imo.

Oh, and these in a 17x9 +63 are less than 18 pounds each- $216 each at Discount Tire before coupons and promos.

s2k_wheel_clearance_02.jpg

Concerned the weight savings (for the Wheels) would be offset by the heavier 9 inch wide tires. Good option nonetheless since your putting more power to the ground.
 
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Concerned the weight savings (for the Wheels) would be offset by the heavier 9 inch wide tires. Good option nonetheless since your putting more power to the ground.

I just read a great writeup on tires in Road and Track: http://www.roadandtrack.com/auto-news/tech/anatomy-of-a-tire and they say that you don't necessarily end up with more contact with the ground:



Its common as well for performance upgrades to fit a wider tire, provided, of course, the added width is compatible with suspension geometry and fender clearances. For example, instead of the Miatas 205/45R-17, why not fit a 235? Wouldnt it give a larger contact patch?

The best Id say is not necessarily. Itll certainly be a wider contact patch, but likely commensurately shorter as welland thus yielding approximately the same contact area. To unravel this oddity, remember that were dealing with a pneumatic structure. And, as any flat tire displays, without its inflation the tire doesnt support much load.

That is, we can get a fairly good estimate of contact area (though not of contact shape) solely from load and inflation pressure: For example, a tire supporting 1000 lb. and inflated to 35 psi will have a contact area of about 28.6 sq. in. Namely, each sq. in. of inflation pressure supports 35 of the 1000 lb. (I say fairly good as this neglects the tires sidewalls and carcass contribution to supporting the loadbut again, remember that flat tire.)

Then why do wider tires improve cornering? Because the shape of a contact patch is as important as simply its area. A wider tires wider contact patch is better at combating side loads and thus provides enhanced cornering.
 
Wider tires also hydroplane easier and have to move more air out of the way...
 
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you put the MX-5 wheels on your CX-5?
What kind of MPG are you getting now?

Mazda 5, not CX-5. Just read the thread, thought I could throw in on it. My tire combo went from 45.6 pounds per corner down to 42.6, old = 205/50-17, new = 235/45-17. Same MPG as before after factoring in the taller tire, about 22 in the city beating on it and 27 on the highway fully loaded and beating on it.

Thanks this helps alot. Those Miata wheels are a good option imo.

Concerned the weight savings (for the Wheels) would be offset by the heavier 9 inch wide tires. Good option nonetheless since your putting more power to the ground.

The only concern I'd have with the Miata wheels is overall weight capacity- but considering that my 5 is 300 pounds heavier than your CX-5s, it's probably fine. The S2000 only puts down 200whp at a 2800 pound curb weight, so it's really not the straight-line grip that I'm worried about. Consistently pulling 1+ Gs in the corners without having to think about it is more important. :)

As for the weight of the tire, you wouldn't necessarily have to run a wide tire on the 9" wheel. You could go with a 225 or 235 to give the sidewall a bit more rigidity while still keeping tire weight and cross section down.

Wider tires also hydroplane easier and have to move more air out of the way...

Yup. Honda dropped the CRX's drag coefficient down a hundredth of a point when making the HF model just by running a thinner tire.
 
As for the weight of the tire, you wouldn't necessarily have to run a wide tire on the 9" wheel. You could go with a 225 or 235 to give the sidewall a bit more rigidity while still keeping tire weight and cross section down.

Let me get this right cause I'm kinda slow lol. OK so getting thinner profile yet wider thread keeps the weight in check yet provides rigidity. Keep in mind I'm sticking with 17x7, 17x8, or 18x8 lighter wheels.
 
Let me get this right cause I'm kinda slow lol. OK so getting thinner profile yet wider thread keeps the weight in check yet provides rigidity. Keep in mind I'm sticking with 17x7, 17x8, or 18x8 lighter wheels.

Not necessarily.

Same width tire on wider wheel = less sidewall flex = better handling (quicker response)

The weight of the wheel is totally up to the design and manufacture of that wheel- you have to know the true measured weights, you can't just judge wheel weight based on size.

The thinner profile is required to maintain the same tire diameter given a wider tread- the aspect ratio is just that, a ratio. A 215/50-17 (215 x .5 = 107.5mm sidewall) is virtually the same diameter as a 235/45-17 (235 x .45 = 105.75mm sidewall). Tire weight is also totally up to the tire manufacturer- size does not necessarily dictate weight.
 
You put one on a scale like I did?

mz5_fitting_235s_800_01.jpg

The design of this wheel suggests it could handle the CX-5's weight. Its a good alternative if you can find some locally. Also, my cousin has an EVO 8 with 17inch forged BBS wheels. I believe they fit but too bad he ain't selling them to me. :(
 
As long as you stick with a 17, 18,19 inch rim, you will likely not see any change in the mpg at all. If you have a 17inch rim, go with 65 tire, 18 inch 60 tire, 19 inch 55 tire. In my opinion a 8 inch rim with a 235 finishes the look as the the 7 inch rim and a 225 tire is too narrow......which is the only thing I did not like about the CX-5.....the stance was too narrow for a vehicle which such a muscular shape. The Kia Sportage top model sits on 235/60/18.....all just my opinion though.....do what you think looks best or feels good too you.
 
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