is it chaging to 18's and non-run flats?

L

lamlp640

Member
 Swansea
The lowest price i can get run flats for on the net is £145.00 each and thats a bridgestone.
My problem is that I love the look of 18 inch wheels, If I do change to 18's will the following be a problem?
a) will the speedometer be affected?
b) will 18 non-RFT's michelin's be more expensive than my 16's RFT's?
c) I have been told that if I do change to non-RFT's I should carry a mobilty kit and that will surfice in the event of a puncture, have any of you used a mobility kit? and what are they like?
d) if I do change to non-RFT's will I have to have a skinny tyre so they wont rub the arches? My current tyres are 225's

Thanks :D
 
If you have a lower profile the speedo should be close. BMW's (all of mine) always read higher than actual speed anyway.

I had (and used) a mobility kit in my M3. I drove 40,000km across North America through deserts, mountains, everywhere. when I finally needed it I had blown a fist size hole through a rear so it didn't matter. I will be getting one for my Zed after I burn the tires off and switch to non-rft's.

Can't help you with the other questions, sorry
 
Pretty much what mcbee said...

When you change from 16" to 18" the tyre sizes change also. So you go from say 225/50R16 tyres to 225/40R18 (or something like that - please check!). The second number is the depth of the profile. You put a large wheel on 18" and lower the profile to 40 and maintain the same rolling circumference. So...
a. No. It will say the correct tyre profile for the wheel in the back of the owners manual*.
b. I wouldn't expect so - I have Eagle F1s at around £90 each, fitted... after a few calls.
c. Not used one - standard with Ms, so I wouldn't worry about it. You can get them pretty cheap. I just have a couple cans of TyreWeld from Halfords (fit nicely in next to the battery)
d. Same circumference as the 16s so no difference. Just check the offset if you are buying aftermarket alloys - this changes how far the wheels stick out.

*Not sure if the owners manual assumes a 255 rear for the 18s?

Having seen A11ys and now DaveGs I'd be after a set of Elips! Otherwise there are some 108s on sale here I think, need a little more car though.

The numbers provided above may not be spot on... more illustrative.

You sound a little uncertain about tyres in general so if you post back with what wheels you're looking at buying (avoid the really cheap new stuff) hopefully we can help with the tyre sizes with out too much of the search stick :poke:
 
PawnSacrifice said:
Pretty much what mcbee said...

b. I wouldn't expect so - I have Eagle F1s at around £90 each, fitted... after a few calls.
:
Click to expand...
Sorry to hijack: Pawn Sacrifice, how do you like the Eagle F1's? They aren't a bad price over here and I was thinking about ordering a set.
 
As above, when you change to a larger wheel your tyre profile goes down to compensate. So as an example, a car with 195/55/16s might go to 225/45/18's. The first number is the width in mm. The second is the height of the sidewall as a percentage of the width (so 45 = 45%). The last number is the diameter. And yes, it really does combine metric and imperial in the same unit of measure!!!

The rolling radius of the wheel must remain within 2.5% of the original to not throw out speedos etc to much. When you see wheels that are the wrong tyre profile for the car it really stands out. Try this link here - enter your current tyre size and it will give you the correct size for different diameter wheels. http://www.tiresizecalculator.info/ . If it helps, Z4Ms have 225/45/18 on the front and 255/40/18 on the back. That's a staggered set up; you do not mention your engine but if it's a 2.0i or 2.2i (And I assume on 16"s it will be?) you don't have staggered from the factory, all four will be the same.

Run Flats are very expensive. Non RFTs should be much cheaper.
 
mikedav said:
The rolling radius of the wheel...
Click to expand...

Damn it, I always get that wrong!

mcbeee, very happy with the F1 Asymmetrics! Great in the dry, which I guess is a given, but surprisingly good in the wet too. Unless someone comes out with something spectacular before I buy my next set I'll be getting them again. That said, my immediate comparison is against the RFT.
 
My Z4 (delivered two weeks ago) has 225,35/19" on front and 255,30/19" on the rear :D
 
mikedav said:
As above, when you change to a larger wheel your tyre profile goes down to compensate. So as an example, a car with 195/55/16s might go to 225/45/18's. The first number is the width in mm. The second is the height of the sidewall as a percentage of the width (so 45 = 45%). The last number is the diameter. And yes, it really does combine metric and imperial in the same unit of measure!!!

The rolling radius of the wheel must remain within 2.5% of the original to not throw out speedos etc to much. When you see wheels that are the wrong tyre profile for the car it really stands out. Try this link here - enter your current tyre size and it will give you the correct size for different diameter wheels. http://www.tiresizecalculator.info/ . If it helps, Z4Ms have 225/45/18 on the front and 255/40/18 on the back. That's a staggered set up; you do not mention your engine but if it's a 2.0i or 2.2i (And I assume on 16"s it will be?) you don't have staggered from the factory, all four will be the same.

Run Flats are very expensive. Non RFTs should be much cheaper.
Click to expand...

Your right, My car is a 2.0i on 16's and they are the same back and front 225's
It took me 6 months to find the right car! God only knows how long it'll take to to find the right wheels, the agony of choice!
 
lamlp640,the 18" wheels that u can opt for on the z4's(eg my 3.0i se has the split rim 108 5spoke style),are 8jx18 on front and 8.5jx18 at rear.

The Tyres are 225/40 18s on front and 255/35 18s on the rear.
Hope this helps u.

cant renmember off hand,but the offset for the wheels are et35/tho if u look elsewr in the forum there are a few posts about this,giving u the exact offsets,front and rear,cheers
 
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