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Discussion Starter · #1 ·
15x7 O.Z. Ultraleggera = 12lbs
205/50-15 tires = 20lbs
32lbs per corner
Gives 1 extra inch sidewall for ride comfort.

Stock 17x7 wheel = 22.5
205/40-17 tires = 20
42.5lbs per corner

O.Z. package saves 42lbs vas stock.

Who else is thinking this is a good/great idea?
 

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Can't run 15" wheels. Won't clear brakes
On the Focus ST this is true, on the Fiesta however the spare tire is a 15" wheel.

Full Size Spare
Your ST vehicle is equipped with a full size, dissimilar spare tire assembly. Although the spare is a traditional, full size tire (as
opposed to a mini spare), it is different in both size and handling characteristics from the standard Fiesta ST performance tire.
If you need to install the spare tire, you must adhere to the following precautions:
• Because of the different performance characteristics of the spare tire, avoid
aggressive steering, braking, acceleration or high speeds when the
spare tire is installed.
• Never enable electronic stability control sport mode or fully disable
electronic stability control when the spare tire is installed.
• Replace the spare tire with the correct original equipment specified tire as
soon as possible.
The following table lists the specifications for the full size spare tire and wheel assembly. Tire speed and load ratings should match those of the originally equipped tires as closely as possible.
Spare tire -
Size 185/60 R15
Speed rating H
Load rating 84
Usage All season
Wheel 15 in. x 6.0 in., 47.5 mm offset steel wheels
From the Fiesta ST owners guide supplement.

I still wouldn't recommend it given the minimum recommended wheel size of 16" for winter wheels over the 17" standard Fiesta ST wheels.
 

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It's hard to say how much it will affect the car but decreasing unsprung weight is almost always a positive and an added bonus is you usually get longer service life out of the dampers since they have less mass to slow. As long as they do clear the Fiesta ST's brakes, which most of the Ultraleggera wheels usually aren't known for being prone to problems with clearance at spokes/inner rim area, they're a nice looking wheel.
 

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Discussion Starter · #7 ·
Please do. Id love to see it and hear your impressions.

Also. I'd run a 225/45r15. Same OD and more meat.

- Drew
225/45-15 has very low selection of mostly race/autocross tires and soft compound street tires with average price of >$150 per tire. I chose 205/50-15 (23.1") for more selection and average costs <$100.

But I agree, the extra meat would look and perform awesome.

F215/50-15 is a perfect OD match for stock b(23.5"), but tires of this size simply do not exist.

195/55-15 is a near-perfect match (23.4") with a huge selection of excellent and reasonably-priced tires, but the tradeoff is a smaller contact patch. For a daily driver, you might not even notice the difference, but it is a tradeoff.


Some research into 16" tires:
215/45-16 (23.6") has very few, very low treadware, rather expensive tires.

205/45-16 (23.3") is the next closest match for stock with broader tire selection similar to 205/50-15
 

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Discussion Starter · #8 ·
It's hard to say how much it will affect the car but decreasing unsprung weight is almost always a positive
I would say it is always a positive.

As an added bonus is you usually get longer service life out of the dampers since they have less mass to slow.
Other benefits include faster acceleration, proportionally less rotational mass at the edge of the wheel/tire, marginally improved fuel economy and less wear on dampers and more responsive damping.

As long as they do clear the Fiesta ST's brakes, which most of the Ultraleggera wheels usually aren't known for being prone to problems with clearance at spokes/inner rim area, they're a nice looking wheel.
Brake clearance is the main concern, and yes, it doesn't hurt that they are a nice looking wheel, IMO.

Thanks for the good discussion all.
 

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While there would be significant weight savings, which would be great for drag racing, the very tall sidewalls the 15 inch tires have would lead to massive loss in the little bit of steering feel the car has. It would feel sluggish to respond to steering inputs as well. The quick response is where this car shines. I've go ahead and ordered a set of 17x7 lightweight oz wheels. They're 17.4lbs each. That's a fairly large drop in unsprung weight that you feel w/o losing the feel and response. If you really wanted lighter, I wouldn't recommend going below a 16" wheel. The tire gets too tall for anything fun and sporty anymore unless you're planning on just straight line work.
 

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That would be one of my only concerns as well and it would depend on how you plan to use the car. If you can find a max performance street tire in a 15-inch size or want to run a track/R-compound tire the pounds of saving can add up, but if tire selection isn't good I'd probably also go with a 16 or 17-inch tire on the same wheel if you like the design and just be a little more selective on which tire to run. There's often multiple pound difference in the same size, different brand performance tires (e.g. Dunlops usually running on the heavy side and Continentals in the same size quite a bit less, etc.)
 

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Discussion Starter · #11 ·
While there would be significant weight savings, which would be great for drag racing, the very tall sidewalls the 15 inch tires have would lead to massive loss in the little bit of steering feel the car has. It would feel sluggish to respond to steering inputs as well. The quick response is where this car shines. I've go ahead and ordered a set of 17x7 lightweight oz wheels. They're 17.4lbs each. That's a fairly large drop in unsprung weight that you feel w/o losing the feel and response. If you really wanted lighter, I wouldn't recommend going below a 16" wheel. The tire gets too tall for anything fun and sporty anymore unless you're planning on just straight line work.
205/40-17 sidewall is 3.2", 205/50-15 is 4". The increase is less than 25% and approximately 0.8"

There will be some loss in steering feel and response, but I don't know if I would characterize it as "massive", 50-series tires are still considered low-profile with appropriately stiff sidewalls. It might really depend on a given individual's personal preferences. Personally, I find any thing lower than 45-series too much a compromise in ride quality for a daily driver. The great thing is the fact that we have choices.

Regardless, I applaud your choice in lightweight 17s. Losing ~5lbs per corner is awesome and I'm sure you will enjoy the difference it makes. (and on a side note, I love the looks of all the OZ wheels)
 

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While there would be significant weight savings, which would be great for drag racing, the very tall sidewalls the 15 inch tires have would lead to massive loss in the little bit of steering feel the car has. It would feel sluggish to respond to steering inputs as well. The quick response is where this car shines. I've go ahead and ordered a set of 17x7 lightweight oz wheels. They're 17.4lbs each. That's a fairly large drop in unsprung weight that you feel w/o losing the feel and response. If you really wanted lighter, I wouldn't recommend going below a 16" wheel. The tire gets too tall for anything fun and sporty anymore unless you're planning on just straight line work.
Be sure to post up pictures of your new wheels when you get them mounted. I had 18x7.5 OZ Ulteggeras on my Focus SVT. While they were very light, they also were VERY prone to lip bending and or cracking/breaking over any kind of bad roads. 17's might be better though
 

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Coming from 14 years of Impreza ownership, it's somewhat surprising to see the weights of some of the wheels being offered for the Fiesta. I know we're early in it's life cycle here in the states, but man, 17 lbs for a 17x7 OZ wheel seems really high. A 17x8 Enkei RFP1 for the STi weighs ~16 lbs. Hopefully lighter wheels can be sourced from foreign markets or local distributors will get some better options available here.
 

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I am going to put 15s on my St and probably run 195 55 15 .I have done this(smaller wheels) on my prevoius cars (16s on a 2008 golf gti and 16s on a 2007 focus st)and had very good results. Faster accelaration, much better braking, cheaper tires just to name a few. As far as losing steering response is concerned, there is nothing to worry about, just get a tire with a stiffer side wall and/or give it a few more psi of tire pressure. Trust me, handling will not suffer,and I am speaking from experience, after all ,one of the greatest handling fwd car of all time, the Dc2 integra type R ran this set up, and that car also weighted around 1100kg. Last but noy least , you can drive onto any curb you want and have the Ricers watch in envy☺
 
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