Dropping a wheel size for comfort?

squerble

squerble

squerble

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Has anyone dropped a wheel size for comfort? My Focus was bought with optional 18” wheels and I’m thinking of dropping down to the standard spec 17”s, but I’m curious if I’ll actually gain much comfort?

The current wheels are 18 with 235/40R18 tyres on, and the standard spec was 17 with 215/50R17 tyres on. I used an online calculator which showed the rolling circumference would be a mere 5mm more so the Speedo change would be -0.25% so I’m guessing it wouldn’t need coding in any variety.

First - has anyone done this on their car and found it noticeable more comfortable or quiet?
Second - those that changed, did you inform your insurance and was it affected? As I’d be buying genuine Ford wheels (either new at £600 a set or get some eBay ones and just live with a few scuffs) I’m wondering if this could be seen more favourably.
 
Yeah I went from 17 to 16 on our Suzuki swift sport, I think I went from 195 40 17 to 205 50 16, I noticed a difference its better over rubbish roads for sure.

I did only do it as I already had a set of 16" alloys and tyres from a previous car but I'm glad I did, in an ideal world I'd have gone down to 15" I think. That's what they use on the nurburgring cars
 
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sovietspybob said:
Yeah I went from 17 to 16 on our Suzuki swift sport, I think I went from 195 40 17 to 205 50 16, I noticed a difference its better over rubbish roads for sure.

I did only do it as I already had a set of 16" alloys and tyres from a previous car but I'm glad I did, in an ideal world I'd have gone down to 15" I think. That's what they use on the nurburgring cars
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Would you say it was a marked difference or just enough that it was noticeable?
 
On my previous focus I had 18" and 16" winter tyres.
What I did notice when using the 16" ones is that on curvy country roads there was more roll, but it's something you'll get used to.
 
My experience is that it makes minimal difference. Owned my previous car with both 18 and 19", and the current one I have 18 and 20". The type of tyre makes more difference.
 
My Focus came with the 18" sport wheels and althought they look great I hate them - The road noise is horrendous also probably due to XL tyres which I was thankfull for last week as I hit a huge pot hole - don't think a normal tyre would have coped.
I also have a set of steel 16" winter wheels and much prefere the ride - My 18s have suffered from buckle and dents in rims so really should change them but tyres are too good at moment and I am very tempted to go 16"
 
squerble said:
Would you say it was a marked difference or just enough that it was noticeable?
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There is a noticeable difference IMO, the thing I noticed that most was the lack of shudder or shimmy when going over potholes. The car seems more settled on the smaller wheels if that makes sense.
 
sovietspybob said:
There is a noticeable difference IMO, the thing I noticed that most was the lack of shudder or shimmy when going over potholes. The car seems more settled on the smaller wheels if that makes sense.
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Yup that makes sense, thanks!

Half the reason for me wanting to change the wheels is also because the 18s are just 5-spokes, and you can see how pathetically small the front discs and rear drums (really, a drum on a 1.4 tonne Focus Estate) are - the 17" 15-spokes will hide that a lot better :D
 
Can you go down to 16s on your gen of focus? If it were me I'd go to smallest I could fit.

Also nout wrong with drum brake especially on the rears, they give good stopping power, generally work better for the handbrake and are nice and cheap, just don't start doing track days!
 
I went from 16" to "17 on my Volvo and I don't notice much difference at all comfort wise.

I get more "tramlining" but thats only because the 17's are slightly wider.
 
I had 19" wheels on my Mondeo Titanium X Sport. I changed them for 17" wheels because the ride on it was incredibly harsh. It was still hard after but it made a hell of a difference for sure.

I did inform my insurance, I told them I'd swapped for smaller genuine Ford wheels and not aftermarket but it made no difference at all to my premium.
 
sovietspybob said:
Can you go down to 16s on your gen of focus? If it were me I'd go to smallest I could fit.

Also nout wrong with drum brake especially on the rears, they give good stopping power, generally work better for the handbrake and are nice and cheap, just don't start doing track days!
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Looking at a price list from 2017 it looks like both the Zetec and Titanium came with 16s as standard, whereas the TitaniumX, which I have, was 17s. I'm very doubtful the brakes will be any difference between models so see no reason why the 16s wouldn't fit. Guess that'd just be down to the rolling circumference difference depending on tyre.
 
Quartz said:
Don’t forget to get the speedometer recalibrated if you do change the tyre size.
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Yea I just checked an online calculator with the tyre sizes that Ford list against the relevant alloys - to go from the 18” to the 17” would result in -0.25% change in reading so wouldn’t need a change; 18” to 16” though would give a 2.1% change resulting in a bit of an over-read so would likely require recalibration/recoding.
 
I wouldn't bother to try and recalibrate at 2% difference, you'll get that much fluctuation going between new and old tyres or different brands. Don't worry till it's over 4% imo.
 
I'll just chime in and say normally when you downsize your wheel you generally increase the aspect ratio - that's where the magic lies.

Also don't forget the unsprung mass difference and if you can find a forged alloy all the better. Can transform a cars handling, mpg and breaking !
 
squerble said:
Yea I just checked an online calculator with the tyre sizes that Ford list against the relevant alloys - to go from the 18” to the 17” would result in -0.25% change in reading so wouldn’t need a change;
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That doesn't sound right. The circumference of the new tyre should be 17/18ths of the old one so there should be a 5.6% difference. Which means that you could be doing 58 when the speedo reads 55.
 
Dont forget to tell your insurance you've changed tyre sizes. They probably wont care, but best tell 'em anyway just in case.
 
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