21" run flats for non run flats?
Discussion
Hi all, I have a new X3 M40i on its way and its on the 21" wheels with the run flat tyres. Just wondering if anyone has swapped the run flats it comes on to non run flats? If so, which tyres have you gone for and thoughts on how the swap has made a difference to ride, handling, tyre noise etc. would be great to hear!? Thanks!
They are 325/30/21.
If it were me I would change for 315/35/21, to just get that smidge more side wall.
Not much choice though.
https://www.camskill.co.uk/m78b0s11610p160982/Pire...
If it were me I would change for 315/35/21, to just get that smidge more side wall.
Not much choice though.
https://www.camskill.co.uk/m78b0s11610p160982/Pire...
In fairness to Stig, the question he was asking was would there be an improvement if he changed from runflats to conventional tyres. The answer is "maybe" but the sidewalls are still the same height so they have little springing.
On the other hand, some of the newer runflats have improved greatly so there might be little advantage in swapping over to conventional tyres.
I am running Bridgestone T005 runflats (205/60/16) on an ED version of the 320d and thay are not much different than conventional tyres.
On the other hand, some of the newer runflats have improved greatly so there might be little advantage in swapping over to conventional tyres.
I am running Bridgestone T005 runflats (205/60/16) on an ED version of the 320d and thay are not much different than conventional tyres.
Also, you have to remember that the 30 profile is a percentage of the width.
So 325/30/21 will give you 9.75mm of sidewall, compare that say a 205/50/16 which will give you 102mm of sidewall, not much in it at all.
Now of course a 325/50 would give you loads more.
OP, have you got the car yet?
Does it feel bad? Or are you thinking it will?
So 325/30/21 will give you 9.75mm of sidewall, compare that say a 205/50/16 which will give you 102mm of sidewall, not much in it at all.
Now of course a 325/50 would give you loads more.
OP, have you got the car yet?
Does it feel bad? Or are you thinking it will?
gizlaroc said:
Also, you have to remember that the 30 profile is a percentage of the width.
So 325/30/21 will give you 9.75mm of sidewall, compare that say a 205/50/16 which will give you 102mm of sidewall, not much in it at all.
Now of course a 325/50 would give you loads more.
OP, have you got the car yet?
Does it feel bad? Or are you thinking it will?
Wow! 9.75mm sidewall really is ‘rubber band’.So 325/30/21 will give you 9.75mm of sidewall, compare that say a 205/50/16 which will give you 102mm of sidewall, not much in it at all.
Now of course a 325/50 would give you loads more.
OP, have you got the car yet?
Does it feel bad? Or are you thinking it will?
I was going to put 9.75cm and then realised we are talking mm on the width so changed it to mm, of course I meant 97.5mm. 
30 profile sounds low, but when the tyres are that bleeding wide, 30% is quite a lot!
Locknut said:
Actually the size I quoted is 205/(sixty)/16 which gives 123mm of side wall.
You seem to be having a bad day, gizlaroc!
I wasn't referring to your wheels, I was just saying that a popular wheel size is 205/50/16 for many cars, and would be considered compliant, and that is only a few mm more sidewall. You seem to be having a bad day, gizlaroc!
30 profile sounds low, but when the tyres are that bleeding wide, 30% is quite a lot!
Of course that calculation only gives the free sidewall height. The actual free sidewall height needs to be calculated by looking up the rolling circumference, working out the rolling radius, and then taken that from the static free radius to get the difference between static and free sidewall height. Typically it will be around 10mm difference.
e.g.
255/35-R19 gives 89mm free static sidewall height, and 80mm laden rolling sidewall height.
(Free = no load at all on tyre; that is the side opppsite that which is in contact with the road)
e.g.
255/35-R19 gives 89mm free static sidewall height, and 80mm laden rolling sidewall height.
(Free = no load at all on tyre; that is the side opppsite that which is in contact with the road)
Thanks all for your inputs on this so far! I have actually test driven one on these 21" RFTs and the ride was surprisingly good, in comfort setting at least! Back to my original question, being, does anyone have any experience in swapping out RFTs on the X3 M40i for conventional tyres? The RFT tyres on the 21" wheels it comes with are Bridgestone Alenza's - front = 245/40 R21 100Y / rears = 275/35 R21 103Y.
Just to point out also that when configuring the X3 M40i you now cannot have the adaptive suspension unless you spec the sports plus package and the sports plus package contains the 21" wheel option only! so I was a tad restricted when specing the car in January. I would have liked to have gone for the 20" wheel, with adaptive suspension and suck up the looks of a smaller wheel (not that 20" is small mind! But on a car a large as the current X3, you know what I mean) but you cant have that spec! Thanks BMW!
Just to point out also that when configuring the X3 M40i you now cannot have the adaptive suspension unless you spec the sports plus package and the sports plus package contains the 21" wheel option only! so I was a tad restricted when specing the car in January. I would have liked to have gone for the 20" wheel, with adaptive suspension and suck up the looks of a smaller wheel (not that 20" is small mind! But on a car a large as the current X3, you know what I mean) but you cant have that spec! Thanks BMW!
Gassing Station | BMW General | Top of Page | What's New | My Stuff