Shoof, would you also agree that (everything else being equal) a taller sidewall will provide a bit softer ride, at the expense of a bit sloppier handling?

For my winter tires on my 18" Turbofans, I'm thinking of going with 225/50's rather than the OEM 225/45 size. I was thinking the taller sidewall would do a better job of protecting the rims from potholes, and I like the way the larger diameter tires fill in the wheel wells too. Someone here on the forum submitted photos with 225/50 all seasons as I recall.

 

According to the miata.net tire size calculator, you would only be gaining 4/10ths of an inch in height while creating a speedometer error of 3.4% too slow. See below:



In addition, IMHO it's not just the height of the sidewall, it's also how the sidewall/tire is constructed. Generally, turn-in response may improve with a lower profile tire, but as Schoof has mentioned, wheel (not tire) width is a factor as well (among myriad other factors). Going with too narrow a wheel for a given tire can introduce some "slop" in cornering and delayed turn-in. I'd want to examine the tire manufactures wheel width recommendation for a given tire size.

 

Shark, I'm probably not using the right word...What I'm referring to is the opposite of a "stretched" tire, where one puts a wide wheel on a narrow tire. Worst thing to come to an automobile, in my opinion.

Example of "stretched":


The "bulge" I'm referring to is putting a wider tire on a narrow rim, not a bubble on the sidewall caused by a road impact. In this case, the OEM 17's are 7" wide. The stock 205 section width is best suited for a wheel that is 5.5"-7" wide. A 225/50 tire is best suited for 6"-8" wide wheel. A 245/45 tire is best suited for a 7.5"-9" wide wheel.

I'm not saying that you can't put a 245 width tire on a 7" wheel, I'm saying that it wouldn't be a good idea to do it, IMO you would be affecting the handling in a negative way at that point. Too wide a tire on too narrow a wheel will cause too much sidewall flex in side to side motion, like taking a hard turn. I did it once before years ago, and it didn't help the handling at all, which is why I am coming to my conclusion. I'm no rocket scientist on this stuff, I'm only talking from experience and manufacturer recommendations.

A taller sidewall will give you a little softer a ride. I think 45 is a good sweet spot as far as handling and ride for this car. I'm not a fan of putting a bigger overall diameter tire than the factory recommendation for tire size, which is why I went with 225/40/19's for my new wheels, not 245/40/19 like some have done. going from 225/45 to 225/50 is giving you a little less than a half inch more sidewall. You really think it's worth going with a bigger overall diameter tire for such a small difference in tire thickness? Plus you're putting a bigger overall diameter tire, which will make the car appear slower because of the bigger tires to what is recommended. I mean it's a minute difference, but it still is a difference.

Your wheels are 18x7.5" wide.
Stock Tire - 225/45R18
Section Width: 8.85 in 225 mm
Rim Diameter: 18 in 457.2 mm
Rim Width Range: 7 - 8.5 in
Overall Diameter:n25.97 in 659.63 mm
Sidewall Height: 3.98 in 101.09 mm
Radius: 12.98 in 329.69 mm
Circumference: 81.58 in 2072.1 mm
Revs per Mile: 800.9
Actual Speed: 60 mph 100 km/h

Tire 1 - 225/50R18
Section Width: 8.85 in 225 mm
Rim Diameter: 18 in 457.2 mm
Rim Width Range: 6 - 8 in
Overall Diameter: 26.85 in 681.99 mm
Sidewall Height: 4.42 in 112.26 mm
Radius: 13.42 in 340.86 mm
Circumference: 84.35 in 2142.4 mm
Revs per Mile: 774.6
Speedometer1: 58.0 mph 96.7 km/h
Speedometer Difference: 3.395% too slow
Diameter Difference: 3.28%

I think by changing to a 225/45 non RF tire, you'll get a slightly softer ride overall. My choice of going with a 225/40/19 tire wasn't my ideal choice, but I went with recommended specs. The ride definitely isn't worse than my stock 205/55/17 RF tires, the bigger non RF tire does absorb the bumps a drop better though. Only a drop. Going from 205/55/17 to 225/40/19 is pretty drastic, and I wasn't looking for a better ride, just better looks and better handling. That the non RF tires ride a little better is only a plus in my books.

Just me though...

 

Thanks to both of you for responding...what you are saying makes sense.

 

I would not have beleaed at this late in my life I would be confronted with so many thoughts on tires. I guess I have never had run flats before, some seem to thing they are inferior? Unless , as the salesman said to me on Sat. , The cms4 dors not have room for a spare, so, the run flats. So far I think they are fine, I have no problem with " road feel" however, my driveway is gravel and rock. That is the real concern , will they hold up along with these cast wheels on my less then ideal road conditions (about a mile)".?
I have no problem with the winter tires that will go on in a month or so. I have no interest in wider tires as who wants to push snow up my mountain drive.A round here the narrower the better. The only place for wide tires would be on trucks for weight . , after all the Mini is not a big truck, or a dragster with huge hp , it's a 1.6 4 cylinder on the small side as well.Big tires on small cars are usually a bad idea, unsprung wt.and all.. Maybe I am wrong with the CMs4 ?

 

I never said tha I was one of those folks longing to go home again. I found out long ago that can not happen. Fact is I couldn't wait to get out Iowa., and I never really looked back!
I have lived almost everywhere in North America, one time or another. I was a traveling kinda Guy.

 

Mine.

 

i will be putting supersports on my cms all4, size 225/50R18, when the oem pirelli p7s wear out

my reasoning is thus (in no particular order)

1) 225/50 is less expensive than 225/45 (i would love to know why this is)
2) more sidewall may better protect my 18" turbofan rims
3) my speedo reads faster than i am really going, so a bigger tire will improve the accuracy of the speedo
4) i think the 225/50 fills the wheelwell better and looks better

my winter tires will be the xice xi3, size 205/65R16 on oem 16" steel rims, my size pick is probably for a different thread

scott

 

I was looking though some old bookmarks and found this comparison that I bookmarked about a year ago...

http://www.caranddriver.com/comparis...mparison-tests

 

I'm running 225-50/18's SuperSports on my Countryman Al4. I have about 6000 miles on them. The responsiveness is fantastic and I love the ride. Also, the 50 series is SIGNIFICANTLY more affordable than the 45 series. And I had two bent rims fixed previously this year so the 50's are much better for my road conditions.

I think somebody had a set posted on their 17's but they don't make these in that size. I think they are running Pilot Sports, which is a different tire.

I ran Blizzaks last year in a 215/55-17 but sold them back to Discount Tire due to a vibration issue. To make a long story short, it wasn't the tires...I had my rear differential replaced by mini (after 3 months of ridiculous inability on their end to diagnose the issue) and vibration solved. Anyhooooooo, I'll also be trying out the Michelin X-Ice Xi3 this year for winter.

 

thanks Shoof & Koopah

thanks for pointing out that the 225/50R18 tire will change the speedo 2mph ... my speedo is off by 1.9mph so this will make my speedo read near spot on!

scott

 

update ...

yesterday, i purchased 4 oem 16" MINI R123 5 Hole Circular Spoke 16x6.5" ET46 wheels from ECSTuning.

as soon as they arrive, they go to my friends body shop for repainting to white, then to the local tire store for tire and tpms sensor install


i will still be installing 205/65R16 michelin x-ice-xi3 tires if they clear

my local tire store will fit one on a wheel and we will use that to check clearance at all 4 wheel positions

has anyone here painted their wheel bolts to match the wheels? results?

scott