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Discussion Starter #1
What would be the widest tire I could get on this car without rubbing issues? I was wondering if anyone with the factory 18's would consider swapping for the painted 17's? I really want some 18" wheels kind of like the ones I have now. Painted with a chrome lip or highlights. But I think I could be OK with the factory 18's. Just an idea.
 

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With the factory 18x8s they run a 235 width tire, BUT they ARE fitted with a steering limiter to keep the tires from rubbing. So I'd consider an 18x7 to avoid rubbing and just go with a 215/35/18 tire.
 

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With the factory 18x8s they run a 235 width tire, BUT they ARE fitted with a steering limiter to keep the tires from rubbing. So I'd consider an 18x7 to avoid rubbing and just go with a 215/18/35 tire.
The tires would need to be:
215/45/18
To be anywhere near stock outer diameter.
The 215/45/18 would still be slightly bigger than the OEM 18" tires. but it is a tiny difference.
 

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The tires would need to be:
215/45/18
To be anywhere near stock outer diameter.
The 215/45/18 would still be slightly smaller than the OEM 18" tires.
Um, how so? The OEM 18"s run a 235/35/18 (sorry I had the layout wrong)

So if the OP runs a 215/35/18 the OD/height will be the same.
 

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The second number is derived from the first and is the aspect ratio: the height of the tire is this percentage of the width.

So the 235 has a smaller aspect ratio to be the same sidewall measurement.

technically.
in reality the easiest way to compare tires is to go to Tire Rack. pull up the tires, look at the revolutions per mile in the statistics. the closest one in the two different rim sizs wins.
The OEM tire is 235/40/18
and the 215 is 215/45/18

Which makes sense as the 17" wheel and tire 215/50/17
The general rule of thumb is one inch bigger rim, one 5% change down in aspect ratio. It works pretty good for the average wheels
So a 215/50/17 with an 18 wheel would turn into a 215/45/18

main point is getting the same number of revs per mile. Then the circumference is the same. Anything within five turns is Ok. the usual revs per mile in these sizes is 819 rev per mile stock 18
The replacement 215/45/18 turns 814 revs per mile. so this tire is slightly bigger. (oops I mixed up before, it is always confusing..)
Different brand can have different final revs per mile, so if you really want the exact revs per mile you might find a tire that is a very close fitment.
 

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The second number is derived from the first and is the aspect ratio: the height of the tire is this percentage of the width.

So the 235 has a smaller aspect ratio to be the same sidewall measurement.

technically.
in reality the easiest way to compare tires is to go to Tire Rack. pull up the tires, look at the revolutions per mile in the statistics. the closest one in the two different rim sizs wins.
The OEM tire is 235/40/18
and the 215 is 215/45/18

Which makes sense as the 17" wheel and tire 215/50/17
The general rule of thumb is one inch bigger rim, one 5% change down in aspect ratio. It works pretty good for the average wheels
So a 215/50/17 with an 18 wheel would turn into a 215/45/18
Never heard that and still confused by your explanation of aspect ratio and percentage of width, can you explain that a little more in depth? I assumed the numbers were pretty straight forward. 50 sidewall to 35 sidewall is 1.5cm different x2 is rougly the 1 inch lost (3cm is less than 1 1/4in.) so it makes sense to go from a 50 to 35, and with that in mind I don't see how your statement works out.
 

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Never heard that and still confused by your explanation of aspect ratio and percentage of width, can you explain that a little more in depth? I assumed the numbers were pretty straight forward. 50 sidewall to 35 sidewall is 1.5cm different x2 is rougly the 1 inch lost (3cm is less than 1 1/4in.) so it makes sense to go from a 50 to 35, and with that in mind I don't see how your statement works out.
You math is totally wrong. (sorry)

You cannot just use the aspect ratio without the number it RATIOS to. never. ever never never.
The aspect ratio is in a way not a real number. it is a ratio, and not by itself anything. it only can exist as a real number when combined with the tread width, and depends entirely on the tread width for a real physical distance

The aspect ratio (height of the sidewall) of the OEM tire 40 is related to the specific width of the OEM tire 235mm This pair of numbers with an 18 hole in the donut is the stock tire. ((so 40% of 235mm is the height of the sidewall)
It has a specific diameter, circumference et al. and one mile of rolling this tire down the road equals 819 revolutions of this wheel

Now for a replacement, to GET THE SAME NUMBER OF REVOLUTIONS you have to change the aspect ratio to whatever works..
So you WANT the 215mm tread width, and you want the 18 wheel donut hole. so what ever 'aspect' (or variable) gives near a 819 revolutions per mile is the winner.
that aspect ratio happens to calculate out to (as close as can be had 45 aspect ratio) which give a decent 814 turns per mile of travel ((So 45% of 215mm is the height of this sidewall)

++++++++++++
totall different method. more like hair of the dog method:
The stock 215/50/17 OEM wheel
The general rule like on Tire Rack is for a one inch bigger rim you cut 5% of the aspect ratio. This ONLY WORKS by chance,
the common chance that for most wheels in the 14 15 16 17 18 sizes, the one inch bigger wheel size calculates out to be a close approximation to 5% aspect loss (keeping the tread width the same)
Or going to a smaller wheel, a 5% aspect gain. (again keeping the tread width the same)
It is just a coincidence of the numbers in this range,(and the fact most tires we are interested in are 195mm to 280mm just a perfect range to fit by coincidence with the 2.54 mm per inch we can use and no magic of wheels at all. (forget all of what I just wrote in that sentence if it makes your head spin... it is for others also.)

If you are still confused go to Tire Rack dot comhttp://tires.tirerack.com/search?p=Q&lbc=tirerack&uid=334789995&ts=custom&w=aspect ratio&af=cat:tiretech&isort=score&method=and&view=list
 

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You math is totally wrong. (sorry)

You cannot just use the aspect ratio without the number it RATIOS to. never. ever never never.
The aspect ratio is in a way not a real number. it is a ratio, and not by itself anything. it only can exist as a real number when combined with the tread width, and depends entirely on the tread width for a real physical distance

The aspect ratio (height of the sidewall) of the OEM tire 40 is related to the specific width of the OEM tire 235mm This pair of numbers with an 18 hole in the donut is the stock tire. ((so 40% of 235mm is the height of the sidewall)
It has a specific diameter, circumference et al. and one mile of rolling this tire down the road equals 819 revolutions of this wheel

Now for a replacement, to GET THE SAME NUMBER OF REVOLUTIONS you have to change the aspect ratio to whatever works..
So you WANT the 215mm tread width, and you want the 18 wheel donut hole. so what ever 'aspect' (or variable) gives near a 819 revolutions per mile is the winner.
that aspect ratio happens to calculate out to (as close as can be had 45 aspect ratio) which give a decent 814 turns per mile of travel ((So 45% of 215mm is the height of this sidewall)

++++++++++++
totall different method. more like hair of the dog method:
The stock 215/50/17 OEM wheel
The general rule like on Tire Rack is for a one inch bigger rim you cut 5% of the aspect ratio. This ONLY WORKS by chance,
the common chance that for most wheels in the 14 15 16 17 18 sizes, the one inch bigger wheel size calculates out to be a close approximation to 5% aspect loss (keeping the tread width the same)
Or going to a smaller wheel, a 5% aspect gain. (again keeping the tread width the same)
It is just a coincidence of the numbers in this range,(and the fact most tires we are interested in are 195mm to 280mm just a perfect range to fit by coincidence with the 2.54 mm per inch we can use and no magic of wheels at all. (forget all of what I just wrote in that sentence if it makes your head spin... it is for others also.)

If you are still confused go to Tire Rack dot comhttp://tires.tirerack.com/search?p=Q&lbc=tirerack&uid=334789995&ts=custom&w=aspect ratio&af=cat:tiretech&isort=score&method=and&view=list
Tire Rack's info page made it clear to me. I'd just link to that from now on if I were you, I couldn't really grasp your explanation without first being explained how it all fit together. You said aspect ratio, when I think aspect ratio first thing I think of is screens, TV, Computer, what have you. When you say the aspect ratio is 35, that makes no sense to me unless you first explain that the aspect ratio is found by taking 35% of the width of the tire. Not to be rude but I know you've explained this before and I just never grasped the concept until I read the page on TR. But thanks for the link! Now I know, and it definitely will make a difference when buying tires in the future!
 

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Hint go to google. Type in "Cat Freeware". Download free Tire size comparitor. I have mine linked to the desktop.. very helpful!
 

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Discussion Starter #12
Im running 215's right now with my 17's so width wise there wouldnt be any change. If I went to 18's I would only gain 1" in appearance. Whats the widest tire I can run with the 17's? What do you think, gain an 1" in diametere or put more rubber on the road with the 17's if I can?
 

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Well if the 235's only fit with turn limiters, and they also stick out a bit more..

I had asked if anyone knew if 225's would fit. no one knew. What you would have to do is check in the wheel wells.. Get you hand between the shock/strut springs where ever the come closest to the wheel/tire and feel how much gap. and in the front turn the wheels all the way and feel how much gap..
Cannot be much if 235' do not fit.
And do not plan on saying "i will just not turn the steering wheel too far..'
Sooner or later you or a service person will and the shredding eek!

So YOU could be the guinea pig to test if 225's rub?
For myself it is not worth the cost to find out they do rub.
215 is plenty wide for 200hp..
 

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Posted via FF Mobile I have 18's on my Focus and I was using 215/40/18 tires and I would rub going over bad dips in the roads. Now I have 215/35/18 series tires and no rubbing issues at all and I'm lowered with the Frpp kit.
 

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Typically at the Tire Rack...........if you go up a wheel size (called plus one), say from a 17 to an 18, you got up a bit on width and down on aspect ratio.
i.e. stock = 215/50R17 so a plus one = 225/40/R18 (or maybe a 235/40R18).

Depends on rim width a bit 18 x 7.5 I'd go with the 225 tire; 18 x 8 I'd look for a 235. But that's just me.
 

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Discussion Starter #16
Well I was wondering if 235 would fit nicely on the 17's seeing they are smaller by an inch. Ill get in there and feel around. See what I find.
 
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