OK, having second thoughts on the 18" wheels, they just look too good to pass up. Just concerned about ride quality vs. the 17s. I know the sidewalls are shorter, but is there that much of a ride quality difference between the two?

Before comparing the stock 17s vs 18s, I do plan to replace the Runflats on day one. so that leaves me up to some size choices as well.
To get a little more meat on the sidewalls, I'm thinking of a 215/55/17 or a 235/50/18 tire

 

my dad has a cms all4 with 205/55-17 pirelli p7 all-seasons rfs, stock suspension

i have a cms all4 with 225/45-18 pirelli p7 summer rfs, sport suspension

dads is a smoother/softer ride

mine is much crisper in the corners, yet not a bone jaring ride

dads will slide all four corners (with DSC/DTC off) at speeds where my car has not yet begun to slide at all

i attribute some to the tires and some to the suspension

scott

 

I test drove both sizes and thought the 17 inch wheels offered more comfort with only a minor difference in handling.

But I was surprised at how few tire choices there are for the 17 inch wheels. The 18 inchers have a lot more options in the aftermarket.

 

You know, it all depends on the condition of the roads on which you drive. I have no doubt that the subjective assessments of folks in So Cal will yield different results than the folks in northern New England.

Might be good to state the road conditions in the areas you drive the most...

FWIW,

 

New Jersey, mostly crappy pot hole roads and such. Will be towing as well.

If I go with the 17s, I'll probably up the size to 215/55/17s.

Much more tire choices and a nice 1" rise in height, 1/2" more sidewall. Probably want a stiffer performance tire to help compensate.

I also like the engine strut mount kit for the FWD. Should help reduce engine pull/torque steer.

 

Not sure I follow. According to THIS tire calculator, the sidewall increase will be only 0.3", not 0.5". Also the increase in diameter is only 0.4" -- but you have to halve that increase since height will be a function of radius rather than diameter. Therefore, your height will only increase 0.2". Make sense?

 

I have an ALL4 w/ the factory Sport Suspension as well. I just went from the 17/AS RF to a 19 A/S. (yes 19).
Here's what I noticed, I imagine the 18s would be slightly less. (also actual tire characteristic will play a small part,, ie sidewall, tread firmness, etc)

19's: I can feel the road, always through the steering wheel. I now feel every crack & dip & it reminds me of my coilover lowered VW. Not crashing harsh, but less isolation & more real vibration/feel/feedback. The turn in is also better, better tires. It felt like the 17's w/ the sport button engaged.
The car rides harder. As you can imagine, less sidewall resulted in more harshness (NVH). Now, as a 20+ yr (every car ever owned has been lowered) driver, I am used to feedback & harshness.
In a brand new car, that I still plan to put springs on, It might not be for everyone.
I imagine the 18's would be a bit less harsh, but my 19's are borderline 'too much' ..and I opted for a taller 45 series tire.

I think a slightly taller than recommend 18 is a great choice.
Upsizing to the recommended diameter does nothing to fill the wheel well. It keeps overall diameter the same while using a larger rim & smaller tire. (shorter sidewall)

I opted for a 225/45 instead of the 225/40 that is the recommended size. I did it for comfort & increased sidewall while filling the opening another .3" (Im so glad I did too)

SO, on an 18, the recommended size is a 225/45.
If you want to retain some comfort while IMO looking better go to a 50 series instead of the recommended 45. The taller sidewall will help correct the ridic. low speedo reading as well. (3-5mph lower than actual based on my GPS/various speeds.)

17 205/55
18 225/45 (*try a 225/50)
19 225/40 (I went 225/45 here)
*all based on a 7-8" wide rim

 

If you go with an 18 and go above the factory size 225/45R18 then you will have a little differance in your speedo, MPG, Performance.

http://www.rimsntires.com/specs.jsp

Check out this link, its great for sizing tires and wheels.

We had a CM base for a loaner for 5 months while ours was being built. It had the 17" RF Continentals, our car has the sport suspension and the 225/45R18 Duelers. I can feel a differance in handling, like was said above by Smithwerks, I feel the road better, like the car tries to follow the little tar strips and ruts more. The more "Performance"the tire the more you will feel the road.

As for ride I didn't find enough differance to give up the better performing setup. Lets face it Minis ride pretty rough and thats the bottom line, my '12 Wrangler is like a Caddy compared to the Mini.....now thats saying something. Of course my wife leaves me behind on the turns....

I said it in other tire posts I have no issues with the RF tires and will buy them again when the stockers wear out.

 

I once considered going from 17's to 18's. My dealer was more concerned about the ease of damaging the 18" wheels than about ride quality. I was advised that it was pretty easy to bend 18" wheels by hitting everyday potholes. I stayed with my 17's.

 

I am quite surprised about how well mine have done in the potholes. I have hit some real bad ones at highway speeds. So bad I actually pulled over to check out the car. Perfect no issues....lucky I guess.

 

another factor that changes the ride is tire pressure

using a tire pyrometer and chalk, i have raised the tire pressures on both my car with 18" pirelli p7 rfs/sport suspension and my dad'd car with 17" pirelli p7 rfs/stock suspension

my car 42 front/36 rear

dad's car 38 front/34 rear

on both cars, the ride improved dramatically, more on my car with the 18" pirelli rfs

on both cars the handling improved

on both cars the tire wear is even across the tread on all tires and even front to rear

on both cars the tires are very quiet

scott

 

I went 215/45-17s for the same reasons. Maryland is I guess the bottom of the rust belt and the roads here suck, easily as bad as the roads in PA where I did a 14 yr tour. As noted above, if you live in SoCal or Arizona, 18s or 19s are prob a no-brainer choice, but here, meh. I have a 92 GP 4 cam with springs (lowered 1.5") and 245/40ZR18s and it rides rough, but its a weekend toy and so no big deal, when you modify a sedan you know that "poor mans Caddy ride" is going to go away but then why did they give it 215HP if you shouldnt abuse it? (Now est 265 BHP). A fun car, no doubts. So anyway, if you dont mind a punishing ride, go w/ the 18s. Around here I was worried about bending a rim, some of these craters will swallow a Peterbilt. BTW, ditching the RFTs is the best move you can possibly make, they are one of the most horrendous decisions in the history of tires.

 

You will typically get a pinch-flat before you bend a rim. Quality rims dont easily bend, non-rated gravity cast ones do.
When opting for anything above 17s, tire pressure will be your saviour. The higher pressure will be a rougher ride to some degree as stated, but its better than a flat or damaged rim IMO.
Also, when going to the upsize wheel, you can easily upsize the sidewall ratio & not have fitment issues.

for instance...
going from a 205/55-17 to the recommended upsize of 225/45-18 yields nearly the same diameter.
sidewall 4.4 to 4"
diameter 25.9 to 26"
speedo difference = -0.4% or 60mph when real speed is 60.2mph

Now, you can go to a 225/50-18 & that would yield a -3.8% difference , or 62.3mph when reading 60. (which would actually make up for the grossly under rated speedo.)

the recommended size for a 19 is a 225/40-19
this yields only 0.8% speedo difference. reads 60.5 when doing 60
a sidewall of 3.5 vs the 17's 4.4"
and a diameter of 26.1 vs the original 25.9
(obviously this will fit as its only .2" larger than the original)
However, thats a big loss of sidewall, nearly an inch.

I chose a 225/45-19 & ended up with a -4.2% difference. real spped of 62.5 when actual is 60.
This now makes my speedo 100% correct when traveling upto 75mph(as confirmed via GPS), over 75mph my speedo reads under 1-2 mph actual.
Going 45 series I also gained more sidewall than the recommended 19" size. 4" vs 3.5" (orig is 4.4), So not much of a loss really.
The total diamter did increase though as ecpected. just over 1".
Again, 17s were 25.9 & my 19's are now 27" in diameter.
This, IMO actually fills the wheel well better & keeps a proper look. I personally dislike the looks of a large vehicle with dainty shoes(ie thinwall tires). (like Suburbans on 30's with huge wheel gaps & paper thin tires, it just looks goofy to me)

*I know this is a 17-18" comparo thread, but wanted to chime in on the size differences and how selecting the next size sidewall ratio can yeild additional sidewall height as well as overall diameter. (thus retaining some comfort & rim/tire protection while still upsizing)
I know a few ppl have selected 18"/50series tires & with the proper rim width & offset this is not an issue, even when lowered.

 

at the stock tire pressure of 32f/32r, my pirelli p7 225/45-18s were brutally hard riding

after raising the pressure to 42f/36r, the ride IMPROVED dramitically, to the point that i will run these tires until they wear out

the next set of summer tires will be michelin pilot super sports in size 225/50-18, non rfs

the handling also improved, particularly the turn in response

i am guessing that the stock pressure is slightly underinflated, resulting in the sidewalls carrying most of the weight

on a runflat the sidewalls are very thick and very stiff

my dealer now recommends higher pressue to all countryman buyers that opt for the 18" wheels

raising the pressure on my dad's 17" pirellis also improved the ride comfort , but not to the extent of my 18" pirellis

scott

 

Well, I went from a Clubman S with Stock 16's to my Countryman S with the 2 Piece Black wheels in 18"

Honestly, due to the larger wheel base the ride is slightly BETTER than it was with my countryman. So far, I'm still in the break in period so I havent' throw it into any turns yet or anything - but due to the higher ride I probably wont be even when the Break IN period is done lol

Really though, I cant compare to the 17s - but the ride is great on the 18s compared to my clubman s on 16s