[giotecno]

Guys, I have been experimenting today with larger tyres and have the M3 tyres left over from my 18" M3 alloys, the rears rub as the M3 setup is aggresive but the fronts dont so I thought Ill chuck the Michelin sports on as I got a nail through the side wall on my vreds, the Michelins tyres are 245/40/18 and all I can say is WOW! the bumps on the road are so forgiving the humps on back roads are not like rocks on impact its smooth and slighlty forgiving ride and not to mention michelins hold the road great. I was thinking for the rears what kind of size should I get to match this setup? I have 255/35/18 at the mo but want more rubber between me and the road so would match the fronts, I know this affects the speedo but not by much, so 255/40/18 or 255/45/18. Let me know what you think guys. Mind you the Michelins are like £200 a pop so might have to sell a kidney

[HighlandPete]

Not quite sure what you are removing, (RTFs?) and what rim widths you have. Assume it is on the 320d.

To me you are putting a very wide tyre on an (8" rim), bit like the way a lot of cars are set up, soggy dynamics for steering and cornering ability. It is not just the vertical stiffness you are changing, but lateral stiffness will be softened as well. Is that what you want?

HighlandPete

[giotecno]

HighlandPete I already moved from RFT to Non, but as one fo my tires got a huge nail through the side and was rendered useless, so unitl I got a new set in I fitted the larger tyres and realised cornering and general ride quality was imporved dramatically.

[giotecno]

I got genuine M3 Alloys style 260, hence the M3 tyres that came with it

[zltm089]

245 for the fronts ....bit too large in my opinion....especially for the standard 18 inch rims....

if you're running standard 18inch rims, the maximum u can go at the rearwill be 255....unless they are 19 inch wheels...

[zltm089]

http://www.kouki.co.uk/utilities/vis...ize-calculator

[zltm089]

i think 235 is the perfect setting for std 18 inch wheels...

not sure whats the wheel size of the M3

[Captain Chaos]

Originally Posted by zltm089

245 for the fronts ....bit too large in my opinion....especially for the standard 18 inch rims....

if you're running standard 18inch rims, the maximum u can go at the rearwill be 255....unless they are 19 inch wheels...

The tyre profile size you can fit has nothing to do with the diameter of the wheel, but the width of it. You can get a wider tyre on an 8.5J18 than you can an 8J19, for example. 245/40 is the OE fitment for the M3's 260 rim.

BMWs invariably benefit on turn-in from a wider front tyre as it helps to reduce the natural understeer, but as Pete says you are increasing the sidewall profile and therefore affecting the lateral stiffness (and other elements). Looking at what you've changed, your improvements will absolutely include the increase from mid-range rubber to premium - the Michelins are one of the best tyres you can buy, so you'd expect them to perform much better than a Vred.

You should take care when playing with tyre profiles - BMW's geometry R&D has no doubt benefitted from a lot more investment than you (or any of us) have put in on the daily commute, and you'll find that improving your tyre manufacturer is often the safer way to improving your drive (and it doesn't FUBAR your insurance policy ). I'm not saying don't do it, just saying be wary of the downsides.

[zltm089]

Originally Posted by Captain Chaos

The tyre profile size you can fit has nothing to do with the diameter of the wheel, but the width of it. You can get a wider tyre on an 8.5J18 than you can an 8J19, for example. 245/40 is the OE fitment for the M3's 260 rim.

BMWs invariably benefit on turn-in from a wider front tyre as it helps to reduce the natural understeer, but as Pete says you are increasing the sidewall profile and therefore affecting the lateral stiffness (and other elements). Looking at what you've changed, your improvements will absolutely include the increase from mid-range rubber to premium - the Michelins are one of the best tyres you can buy, so you'd expect them to perform much better than a Vred.

You should take care when playing with tyre profiles - BMW's geometry R&D has no doubt benefitted from a lot more investment than you (or any of us) have put in on the daily commute, and you'll find that improving your tyre manufacturer is often the safer way to improving your drive (and it doesn't FUBAR your insurance policy ). I'm not saying don't do it, just saying be wary of the downsides.

Correct!!! ...


I didn't word it properly... the width will depend on the 8j, 8.5j sizes....and they can be all 18inches... but i think the standard bmw wheel for the front is 8j

[ALF_E90]

I'm happy fitting non-RFT but not sizes other than BMW-listed sizes, personally, for insurance reasons.

I have noticed a massive ride improvement from my 225/45/17 all round compared to the staggered 18's, but a lot of this will be tyres - on previous cars there have been big differences between ride quality just with different tyres tyes. Conti SC3's were especially good.

As to a wider front tyre helping reduce understeer - a narrower rear will do this also, and wider tyres tramline and aquaplane more. Also, better a premium narrow tyre than a cheaper wide one. I have never had a car that didn't ride and handle better on the narrowest tyres and smallest wheels I tried.

One thing I'd be interested to know is if anyone notices ride quality differences between different non-RFT of different load ratings? My 17's are generally available in 91 and 94 load ratings, the latter is very high. Does this lead to a RFT-like stiffer sidewall? Comparisons between different tyre types are not valid - the various manufacturers have different philosophies on sidewall stiffness, compound, etc.

[HighlandPete]

Originally Posted by ALF_E90

..I have noticed a massive ride improvement from my 225/45/17 all round compared to the staggered 18's, but a lot of this will be tyres - on previous cars there have been big differences between ride quality just with different tyres tyes. Conti SC3's were especially good.

As to a wider front tyre helping reduce understeer - a narrower rear will do this also, and wider tyres tramline and aquaplane more. Also, better a premium narrow tyre than a cheaper wide one. I have never had a car that didn't ride and handle better on the narrowest tyres and smallest wheels I tried.

Careful now... we'll be having another 18" to 17" wheel debate. But have to agree, why oversize the tyres, for perceived advantages which are usually to the detriment of our drive, in a practical sense?

HighlandPete

[ed335d]

Originally Posted by zltm089

i think 235 is the perfect setting for std 18 inch wheels...

not sure whats the wheel size of the M3

These are the standard M3 wheel and tyre sizes....

Front 8,5J ET:29, 245/40/18
Rear 9,5J ET:23, 265/40/18