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So I want to get new rims and tires for my 2018 SEL Hatch. Currently I got stock 17’ wheels and Continental tires.

I want to get wheels that are bigger and tires that are skinnier. Any suggestions?
 

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The easiest way to do a search and know you have the right sizes, is to go to Tire Rack and enter your car info, then tell it search for wheels and tires.
The system will automatically give you the right size tire to go with the larger rim size.
EVEN IF YOU DO NOT BUY FROM THEM. YOU can save the info and go anywhere. [cheers]
 

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Skinnier as in lower ratio or narrower tire?

Personally, I like my 17s with 235/45s, or you could base it off of the ST's 18s or the RS's 19s, I wouldn't go higher than an 18 on a base model, but that's just my personal preference, especially since bigger, heavier wheels will strain the already iffy DCT.

EDIT: For clarification, I went from the stock 16x7 to a 17x7.5.

Also, your stock tire height is 25.46". 235/40R18 is factory ST size and 235/35R19 is factory RS size, both are within .06".
 

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Taller and skinnier tires? So all the weight, none of the benefits?
I think the op means the aspect ratio as 'skinnier' and not the actual tire width. [poke]

The main benefits of low aspect ratio tires (skinny) are quicker TURN IN and steering response in general and when racing around corners like a maniac.
The added weight really does not matter much unless you are a stoplight dragster.
The main viewing benefit is they look 'cool'(er) and make you seem like boy racer' (Even I 69 year old bag, have that boy racer aura driving my ST LOL)
One negative is 'skinny' profile (low profile 40 or 35) is harsher ride. Also one has to pay more attention to being certain the tires are properly inflated. Since there is a lot less actual air inside a low profile tire, losing a little matters a lot more, than a fat profile tire.
 

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I think the op means the aspect ratio as 'skinnier' and not the actual tire width. [poke]

The main benefits of low aspect ratio tires (skinny) are quicker TURN IN and steering response in general and when racing around corners like a maniac.
The added weight really does not matter much unless you are a stoplight dragster.
The main viewing benefit is they look 'cool'(er) and make you seem like boy racer' (Even I 69 year old bag, have that boy racer aura driving my ST LOL)
One negative is 'skinny' profile (low profile 40 or 35) is harsher ride. Also one has to pay more attention to being certain the tires are properly inflated. Since there is a lot less actual air inside a low profile tire, losing a little matters a lot more, than a fat profile tire.
I wouldn't say that the added weight doesn't matter much, especially since it's unsprung, rotational mass. The larger wheels add more rotational mass on a low powered car and the larger diameter pushes more of the weight out away from the center of rotation. On a DD it wouldn't matter but it's a pretty big difference on the track when chasing time.

3 pounds of rotational mass/weight per corner on the evo was slightly noticeable. 5 pounds loss per corner on the focus was even more noticeable.
 

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I agree. Reducing unsprung mass has many benefits, and isn't just for "stoplight dragsters", and the farther from the axle centerpoint the weight is, the greater the effect is.
 

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So why then do they put 19's on the RS and 18's on the ST?
If the wheel weight was so important, they would be putting 14's on!
Tiny wheels with weird brakes to fit in the little wheels... LOL
 

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Because low profile tires are great for turn-in and handling, as you mentioned. It certainly not because they want to add rotating mass. [neener]

Brake size...now there's something that's not all that important for a daily driver.
 

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So why then do they put 19's on the RS and 18's on the ST?
If the wheel weight was so important, they would be putting 14's on!
Tiny wheels with weird brakes to fit in the little wheels... LOL
Just for looks since the car still has to appeal to the masses in order to make any money. Cornering response can be another reason, but a 30 sidewall tire is still a 30 series regardless if the wheel is 16" or 19".

For a race car you always want the smallest "things" that will work for weight and cost savings. Generally speaking, 5 pounds off unsprung non-rotational mass is like 20 pounds of sprung weight. So buying wheels that are 5 pounds lighter per corner than your current ones is like booting your GF out the car. It doesn't always apply since there's a lot of factors but it gives a general idea.
 

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The manufacturer likes to keep the wheel/tire combo diameters similar across the line so they don't have to re-gear transmissions or re-calibrate speedometer settings, especially for models or trim lines that share the same transmission. Therefore, small wheels get high profile tires, larger wheels get correspondingly lower profile tires so the rotating diameter/circumference is similar across the board, as is ride height, etc. The more sport-oriented models of the line will have the larger wheels and lower profile tires primarily for increased handling, and the "base" trims will get small wheels for a lower price tag and slightly improved MPG. The Focus is a good example of this, with the "handling package" equipped with 18" wheels, vs. 17" on the SE Sport, SEL and Ti packages and 15" on the S & SE base models.

So, the manufacturer isn't typically going to offer a 16" wheel and a 19" wheel both with a 30 aspect ratio on the same vehicle....
 

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Generally speaking, 5 pounds off unsprung non-rotational mass is like 20 pounds of sprung weight. So buying wheels that are 5 pounds lighter per corner than your current ones is like booting your GF out the car. It doesn't always apply since there's a lot of factors but it gives a general idea.
No... a rotating wheel contributes an additional 30% to 40% of its non-rotating weight to the 'equivalent mass' of the vehicle.

5lbs of weight savings per wheel is like removing 7lbs x 4 = 28lbs from the body. That's a very thin GF....
 

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Taller and skinnier tires? So all the weight, none of the benefits?
Welp depends on what the op is looking to do.

Bigger wheels will look better and fill the wheel gap. Now if he lowers the car quite a bit a smaller tire will help with rubbing thats if he's going for the slammed look.


OP what are you looking to do? Answer that and we can help you with better info...
 

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No... a rotating wheel contributes an additional 30% to 40% of its non-rotating weight to the 'equivalent mass' of the vehicle.

5lbs of weight savings per wheel is like removing 7lbs x 4 = 28lbs from the body. That's a very thin GF....
It's widely accepted that 1:4 ratio is the generic non-rotational unsprung mass to sprung mass ratio. (1:3.8 I believe but for simplicity sake.) I have no idea what it is for one that's accelerating or braking but I wouldn't be surprised if the ratio was greater.
 

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These threads are dangerous to noobs whom are seeking helpful info.

In simple terms, weight always matters. Be careful when increasing either sprung or unsprung/rotational weight. I would strongly recommend against adding weight in this area. It is worth spending a few more dollars if you have to in order to keep the weight of wheels/tires down. As mentioned, the distance the weight is from the rotating center is critical for accelerating and decelerating.

I hope the assumption stated earlier about "skinnier" tires is correct(lower aspect ratio vs narrower width). However, it would be fantastic for OP to chime in and confirm his misuse of terms.
 

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Discussion Starter #17
Oh damn, I didn’t mean to cause any arguing over anything. I’m a noob and don’t really know the correct terms for these things. But yes I was looking at getting what the RS wheels are like and if they could possibly fit the SEL. Thanks for the pros and cons of having these different wheels and tires.
 

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These threads are dangerous to noobs whom are seeking helpful info.

In simple terms, weight always matters. Be careful when increasing either sprung or unsprung/rotational weight. I would strongly recommend against adding weight in this area. It is worth spending a few more dollars if you have to in order to keep the weight of wheels/tires down. As mentioned, the distance the weight is from the rotating center is critical for accelerating and decelerating.

I hope the assumption stated earlier about "skinnier" tires is correct(lower aspect ratio vs narrower width). However, it would be fantastic for OP to chime in and confirm his misuse of terms.

Mr Nanny, I hope you realize we are all adults. No children with plastic minds easily swayed to jump off cliffs, Nor taunted to try to swim raging rivers on a dare.
If anyone makes suggestions, we ALL expect the person reading any sort of suggestion will have the ability to MAKE ADULT DECISIONS for themselves.
Otherwise, it they don't, they probably don't have a driver's license either.
Thank you for worrying. I bet you worry all day all night about the poor slobs being misguided by folks. But really, respect folks ability to make up their own minds, hey. [sadpanda]

As for wheels, the Focus MK3 has all sorts of sizes OEM, from 16" 17"18"19" so as long as you have the right offset. no problem.
 

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Mr Nanny, I hope you realize we are all adults. No children with plastic minds easily swayed to jump off cliffs, Nor taunted to try to swim raging rivers on a dare.
If anyone makes suggestions, we ALL expect the person reading any sort of suggestion will have the ability to MAKE ADULT DECISIONS for themselves.
Otherwise, it they don't, they probably don't have a driver's license either.
Thank you for worrying. I bet you worry all day all night about the poor slobs being misguided by folks. But really, respect folks ability to make up their own minds, hey. [sadpanda]

As for wheels, the Focus MK3 has all sorts of sizes OEM, from 16" 17"18"19" so as long as you have the right offset. no problem.
People ask questions because they don't know the answer and are seeking guidance.
What concerns me is a noob receiving inaccurate information and thus making a poorly informed decision.
Sometimes, people make inaccurate comments and it can sway a noob's perspective.
I'd hope that everyone contributes what they believe is helpful, but sometimes the contribution can be more harm than good.
 

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It's widely accepted that 1:4 ratio is the generic non-rotational unsprung mass to sprung mass ratio. (1:3.8 I believe but for simplicity sake.) I have no idea what it is for one that's accelerating or braking but I wouldn't be surprised if the ratio was greater.
It's F = Ma, but M is not just the static mass of the vehicle, but also includes the equivalent mass from the rotating inertia of the entire driveline : tires, wheels, rotors, halfshafts, gears, clutches, flywheels, crankshafts, etc.

Again, for a single alloy wheel, take the actual static wheel weight and multiply it by 1.3 or 1.4 or so. Bigger diameter wheels trend more toward the larger multiplier. The result is roughly the equivalent mass contribution that the vehicle "sees" under acceleration or braking from that particular wheel. Then take into account that there are four of them per vehicle.

Tires are each multiplied by at least 1.9 as their mass is located closer to the rolling radius of the tire/wheel combo.

Note: the individual multiplier can never reach 2.0 or higher, as that is the equivalent mass of an infinitesimally thin rotating ring under linear motion.
 
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