Ask MF: Upgrading to 18″ Wheels
This question comes from MF reader Kevin D.:
>Did you have to change anything when upgrading to 18″ rims? Will the run flat light come on and does the mph gauge need to be re-calibrated?
In my personal experience there’s nothing more to do than to reset the tire monitoring button after installation of the wheels/tires. The reason being that the circumference is typically different than the previous combination and the system will need to be re-calibrated. Otherwise that’s pretty much it. MINI has a steering angle stop kit they recommend with 18″ wheels but I’ve found that the several popular sizes (205/40/18 & 215/35/18) don’t rub so I’m not sure there’s much of a point. I’ll be testing that theory further when I pick-up new 215/40/18 rubber (replacing my current 215/35/18) for my car early next year.
Of course this doesn’t begin to answer all the reasons you may or may not want 18″ wheels on your MINI.
Huh? If I change the overall size of the rims, then the diameter of the tire will change? Not if you buy from the right place. Remember, you’re wanting to go from a 17″ rim to an 18″ rim. If you buy from the right people, those people will find you the correct tire sidewall height to make sure your overall diameter does change. No change in overall diameter will make no changes to rolling distance for one turn of the wheel, which will make for no difference for the speedo or odo. Saying that changing your rim size will make your overall tire diameter different is quite a bit like saying buying pants with a longer inseam will make you taller.
Checkout the following link where you can play around with various rim and tire sizes and see the effects of the speedo changes: <a href="http://www.miata.net/garage/tirecalc.html" rel="nofollow ugc">http://www.miata.net/garage/tirecalc.html</a>
Try for yourself: Put in a 205/75/r13 and then on the other side put in 205/45/r18. What?! You can’t do that. That’s five inches of change on the rims! But wait, you can. Plug in those numbers and see the overall circumference has not changed and you will not need to worry about the speedo. Go crazy and you can see that you can get big rims
>Huh? If I change the overall size of the rims, then the diameter of the tire will change? Not if you buy from the right place.
Well actually it will change – there are subtle differences even between the different sizes that come from the factory. Check out the wonderful <a href="http://www.mini2.com/forum/faq.php?faq=faq_wheels_tyres" rel="nofollow">MINI2 Tire/Wheel FAQ</a> for the specifics.
I replaced the 17″ S-lites/stock all-season run flats on my R53 with 18″ JCW wheels with the MINI supplied Dunlop performance runflats. I did not have to reset the tire pressure sensor when I did that.
I have since had a slow leak in one of my tires, and the warning light only comes on when I have lost aroud 5 lbs of tire pressure. I think it is safe to say the sensor is not extremely sensitive to minor overall diameter changes.
I also didn’t put the MINI recommended steering angle stops in when I switched to the 18″ rims, and have had no problems.
I think I really need to lower the suspension slightly (thinking about the JCW suspension kit) and some spacers would also help to fill the wheel wells. I might have some rubbing issues if I do that.
Doesn’t the JCW racer come with 17″ wheels?
It’s a good idea to always reset the tire monitoring system to keep it monitoring it’s intended range, whatever that may be. My theory is, if your new 18″ wheel/tires are just slightly larger it may not need to be reset but you may find you need to lose a larger than desired amount of air before it warns you.
>Doesn’t the JCW racer come with 17″ wheels?
Yes they run 17″ Borbet (BBS) wheels. The current cars run the same size but using BBS R90s. I asked one of the guys who help organize and run the Challenge in Germany about this at MU. He said it comes down to two things; cost (since they have to stock an enormous amount of wheels at any given time in the season) and it’s also a limiting factor in terms of grip and performance.
Déjàvu?
<blockquote>MINI has a steering angle stop kit they recommend with 18″ wheels but I’ve found that the several popular sizes (205/40/18 & 215/35/18) don’t rub so I’m not sure there’s much of a point.</blockquote>
I believe this kit is recommended because of the high (52mm) offset of OEM 18″ wheels. I don’t think aftermarket wheels with lower offsets will need it.
Like Gabe said, it’ll change the diameter b/c none of the available 18″ tires exactly match the diameter of the factory 17″ tires.
But, even different brands in the same size will have subtle diameter differences. No worries, though–just think about how much diameter change there is in a new factory tire & by the time it wears out. ~0.5″.
I’ve had up to 225/35/18’s on my MINI w/ the JCW suspension–no rub w/ 42mm offset rims.
All this being said, I’ll never have 18’s on my MINI again. I really like the look & steering response, but the ride is so harsh & it’s so much nicer to not have to worry about curbing a rim every time you parallel park. Of course, these are city concerns.
It took a little while to get used to the ‘squirmyness’ of a 45 series 17″ tire, again, but you relearn how to throw the car around & it makes the bumps & potholes in DC liveable, IMO.
Another complaint about 18″ tires-there is much more unsettling of the car in bumpy corners. The compliancy of the 17’s make them stick much better mid-corner, again just on bumpy roads.
And, that was w/o the MINI recommended steering stops.
What are “steering stops”?
<blockquote>He said it comes down to two things; cost (since they have to stock an enormous amount of wheels at any given time in the season) and it’s also a limiting factor in terms of grip and performance.</blockquote>
So they are trying to limit the cornering speed by using 17″ tires? If they are buying in such quantity with sponsorship I’d guess they could get 18s at similar cost.
18″ are so magnifique for the mini . But not for front lower arm bushing!!!
or the fault of the 215/35/18 tires ?
Got some alta psrs ( with a little issue though …7/10M/M..) and think i’m getting back to 215or 205/40/18 to save them . So bad roads over here !!
Thinking of jcw suspension too .
Thanks Gabe .
Did anyone actually go and use the miata tire calculator that dominicminicoopers posted a link to? How much % difference are you going to have? Seriously, post your numbers here, including the sizes as well as the percentage. Is that % great enough to warrant changing your odo? How about when your tires start running low on tread due to normal wear? Do you run to the dealership and have them change it because of the % difference from the time the tire was new?
<blockquote>So they are trying to limit the cornering speed by using 17″ tires? If they are buying in such quantity with sponsorship I’d guess they could get 18s at similar cost.</blockquote>
18″ wheels on a Mini are for vanity, and have no business on a real Mini racecar for a few reasons: As implied by another poster in this thread, the reduced sidewall and compliance will unsettle the car, there is more risk of tire/wheel damage, and because smaller wheels are lighter.
“Steering stops” are turn-to-turn limiters that are sometimes needed to avoid tyres fouling on bodywork when on extreme lock.
Also if you put different wheels on you need to get your alignment checked, as slightly wider wheels may affect the steering geometry.
If you alter your car’s specification without being endorsed by MINI NA your warranty may be null and voided.
Gabe,
Have you ever thought of painting your calipers black?
<blockquote>Gabe,
Have you ever thought of painting your calipers black?</blockquote>
I don’t know if Gabe has thought of this, but I have been. I have a Dark Silver/Black MCS with the all black JCW Wheels, and I think black calipers would be very nice…