Tire sizes

alik01 · 12-16-2009, 03:57 AM

Hi guys,

Trying to order a set of Michelin Pilot Sport PS2s for my 130i and just saw that the car had 205/45/18 at the front and 225/40/18 at the rear! Is this how it's supposed to be i.e. staggered width and profile or has someone made a booboo somewhere?

What sizes should I opt for? Any help and advice on this will be very much appreciated as I'm really lost on this!

Thanks in advance.

Jeef Beef · 12-16-2009, 04:32 AM

Yep, the rears are supposed to be wider than the fronts. No mistake there. My 135i is 215 fronts and 245 rears.

The 'profile' figure in the middle (i.e. 45 and 40 for you) is a percentage based on the width. Therefore, your fronts and rears are the same profile, but since your fronts have a lower width, then the percentage would be higher.

alik01 · 12-16-2009, 04:56 AM

Thanks Jeef Beef. Makes sense now, so should I stick to the same sizes or should I try something wider? I don't think Michelin has a 205 either.

AussieRacer · 12-16-2009, 06:04 AM

You can go wider, but try to keep the ratio close to original. Eg. 205 x 0.45 = 92.25 sidewall height (theoretically). So if you went 215/40, you'd get 86, which is a big gap, but 215/45 is closer ay 96.75. One reads over and one reads under when it comes to the speedo. Since most speedos already read under, the preference is to go over.

However if the rims and guards can cope with 225/40, the ratio is a lot closer to original. That's called two sizes up.

alik01 · 12-16-2009, 06:15 AM

Thanks for the clarification AussieRacer. My rims are the 18" M double spokes and as far as the guards are concerned, I have the standard M-sport suspension. Do you think it'll handle the 225/40 setup? And should I just use 225/40 for all 4 corners or double up on the rears?

dk130i · 12-16-2009, 03:43 PM

225/40 will be fine, I have the same car/rims as you and I've tried the following combinations so far:
205 front 225 rear
225 front and 245 rear
225 both front and rear

....and prefer the 225 all 'round.

takahashi · 12-16-2009, 04:20 PM

Quote:

Originally Posted by AussieRacer

One reads over and one reads under when it comes to the speedo. Since most speedos already read under, the preference is to go over.

Stictly speaking it is not advisable. Not because it does not make sense, it makes perfect sense to have a larger diameter tyre but....

http://www.vicroads.vic.gov.au/NR/rd...340/0/VSI8.pdf

Which states that.... in the image below.

15mm in diameter change is a rediculous thought but I guess if a cop knows about it you will get a yellow sticker on your windscreen.

But if you find the latest 130i having a bigger wheel/tyre size you can go to that, since they said largest diameter "specified by the vehicle manufacturer for that model or vehicle series".

takahashi · 12-16-2009, 04:24 PM

There are also "tire calculator" out there. Google "tire calculator" in American spellings.

The Vic guide also said no 25mm or wider, but please check NT.... it may be more relaxed and I know of some slight variation in rules for ride height between states/territories.

alik01 · 12-16-2009, 06:02 PM

Thanks so much for all the info guys, really appreciate it.

Checked the tire calculator as per Takahashi and the 225/40 only has 0.7% variance, which seems nominal.

Also judging by dk130i's comments, 225/40 all
around might be the go, hopefully the increased grip area up front should aid in mitigating the understeer a little bit.

Thanks again guys.

dk130i · 12-17-2009, 02:56 AM

Quote:

Originally Posted by alik01

Also judging by dk130i's comments, 225/40 all
around might be the go, hopefully the increased grip area up front should aid in mitigating the understeer a little bit.

225s all'round definitely help in that regard.

using 225s front ans 245s rear means limits are higher but balance is still the same and front tyres are still letting go first, also 245s on the rear give more traction and grip and somewhat reduce ability to adjust direction of travel using accelerator...

If you value traction off the line more than the overall chassis balance you may want to stick with a staggered setup.

dr.bmw · 12-17-2009, 03:12 AM

I thought that because of different rim sizes front/rear, 225s up front will buldge out quite a bit?
I think front rims are 7" and rears are 7.5" correct me if i'm wrong please

Taymaishu · 12-17-2009, 03:40 AM

I run 225 (width) /45 (profile) /R17 (size).

Trying to upgrade to 245's

dr.bmw · 12-17-2009, 03:55 AM

cool got some pics of the front tyres' sidewalls?
what brand? i'll be due for new set all around in a few months i think

woosh · 12-17-2009, 04:07 AM

Quote:

Originally Posted by dk130i

225s all'round definitely help in that regard.

using 225s front ans 245s rear means limits are higher but balance is still the same and front tyres are still letting go first, also 245s on the rear give more traction and grip and somewhat reduce ability to adjust direction of travel using accelerator...

If you value traction off the line more than the overall chassis balance you may want to stick with a staggered setup.

I tried doing that.... still didnt help me trying to alleviate this problem:

lol

I'm back to stock wheels right now... so I might take your suggestion Drazen, and try running the 225 tyre/wheel combo i have sitting in the garage on the fronts, along with the 225 runflats on the rear. hehe... will see how they go =]

alik01 · 12-17-2009, 05:12 AM

Dk130i, definitely sounds like the 225 all around is the go, definitely want the chassis balance, and accelerator direction changes are nice thing to have, not that I do that sort of thing!

The understeer is really prevalent on mine at the moment as the rear are brand new and the fronts are nearly shod! Hopefully I'll have these new shoes on before xmas!

dk130i · 12-17-2009, 05:32 AM

Quote:

Originally Posted by dr.bmw

I thought that because of different rim sizes front/rear, 225s up front will buldge out quite a bit?
I think front rims are 7" and rears are 7.5" correct me if i'm wrong please

I think that applies for cars with 17"s.
Not sure about 125s but Pre-facelift 130i that come with 207 style 18" rims are 71/2" fronts and 8" rears and post facelift (mid 2007 onwards I think) were 8" front and 8 1/2" rear.

225 PS2 RFT on 7 1/2" looks OK, no "bulging"

Sina,
Forget about 245s, for more traction off the line (and to beat those pesky 125s) you need one of these:

dk130i · 12-17-2009, 05:40 AM

Quote:

Originally Posted by alik01

....... and accelerator direction changes are nice thing to have, not that I do that sort of thing!......

just enough to correct understeer mkay

, we wouldn't promote lairy tail all out slides out of roundabouts now, would we?

alik01 · 12-17-2009, 06:42 AM

All I want for a few xmas is a Quaife LSD!

Quote:

Originally Posted by dk130i

just enough to correct understeer mkay

, we wouldn't promote lairy tail all out slides out of roundabouts now, would we?

We would never! Never ever!

dr.bmw · 12-17-2009, 04:49 PM

dk130i
Taymaishu's 125i is 17" all around, so is mine
I've been toying with the idea of 225/40 all around but just not sure about those front rims coping with oversized tyre
cheers

Taymaishu · 12-17-2009, 04:53 PM

Quote:

Originally Posted by dr.bmw

dk130i
Taymaishu's 125i is 17" all around, so is mine
I've been toying with the idea of 225/40 all around but just not sure about those front rims coping with oversized tyre
cheers

I have 225/45 all around, they're perfect

Wouldn't mind 245 rears

alik01 · 01-19-2010, 06:57 AM

So, have had my new tires on or about a week now and wanted to break them in before passing on my impressions.

I went with the PS2s with 225/40 all around. Got it from
Tirerack.com and have to say I'm amazingly impressed, they handled everything beautifully. Had the wheels delivered less than 1 week from
ordering, including wire transfer and all. Cost me
around AU$1700 landed including $300 tax and customs. Which I am
really happy about as I got it a lot cheaper and faster than anything here.

Had the tires fitted, cost $135 with alignment. The fitting was the only unpleasant part as the Goodyear guys here detroyed the lip of the rim and scared some of the face - looks like they use a crowbar to lever off the runflats. Also mucked up the alignment. This was supposed to be me being taken care of! But they have agreed to repair and is getting sorted so not too fussed and this stuff just happens in Darwin, as I am
findig out daily!

But, the tyres are incredible! The ride is improved a thousand fold and has really helped with the understeer. They are so sticky even in the wet, it's amazing - and it gets crazy wet here, more rain in an hour than Victoria gets in a year or somthing like that! So steering feel is really good and the car feels
really responsive! Also hardly see the traction control light anymore during normal driving!

I haven't really pushed too much with the new tyres, wanted to
get them fully run in. Will post up at the limit thoughts next week or so. But so far, would recommend to anyone!

12-16-2009, 03:57 AM	#1
alik01 Lieutenant Colonel 51 Rep 1,792 Posts Drives: Slowly & Responsibly Join Date: Nov 2009 Location: Darwin, Australia iTrader: (0)	Tire sizes Hi guys, Trying to order a set of Michelin Pilot Sport PS2s for my 130i and just saw that the car had 205/45/18 at the front and 225/40/18 at the rear! Is this how it's supposed to be i.e. staggered width and profile or has someone made a booboo somewhere? What sizes should I opt for? Any help and advice on this will be very much appreciated as I'm really lost on this! Thanks in advance. Last edited by alik01; 12-16-2009 at 04:21 AM..
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12-16-2009, 04:32 AM	#2
Jeef Beef Lord Captain Commander 110 Rep 3,093 Posts Drives: a sleeper Join Date: Oct 2009 Location: Sydney, Australia iTrader: (0)	Yep, the rears are supposed to be wider than the fronts. No mistake there. My 135i is 215 fronts and 245 rears. The 'profile' figure in the middle (i.e. 45 and 40 for you) is a percentage based on the width. Therefore, your fronts and rears are the same profile, but since your fronts have a lower width, then the percentage would be higher. __________________ E82 135i M-sport: SGM/6MT/Black
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12-16-2009, 04:56 AM	#3
alik01 Lieutenant Colonel 51 Rep 1,792 Posts Drives: Slowly & Responsibly Join Date: Nov 2009 Location: Darwin, Australia iTrader: (0)	Thanks Jeef Beef. Makes sense now, so should I stick to the same sizes or should I try something wider? I don't think Michelin has a 205 either.
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12-16-2009, 06:04 AM	#4
AussieRacer Major 24 Rep 1,058 Posts Drives: 2008 135i Join Date: Apr 2008 Location: Aust iTrader: (0)	You can go wider, but try to keep the ratio close to original. Eg. 205 x 0.45 = 92.25 sidewall height (theoretically). So if you went 215/40, you'd get 86, which is a big gap, but 215/45 is closer ay 96.75. One reads over and one reads under when it comes to the speedo. Since most speedos already read under, the preference is to go over. However if the rims and guards can cope with 225/40, the ratio is a lot closer to original. That's called two sizes up. __________________ Current: 135i Auto, Le Mans Blue - w/ Bridgestone RE-11 rears, GP Thunder 7500k angels, & "golf tee" mod plus a few M3 suspension bits and pieces...
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12-16-2009, 06:15 AM	#5
alik01 Lieutenant Colonel 51 Rep 1,792 Posts Drives: Slowly & Responsibly Join Date: Nov 2009 Location: Darwin, Australia iTrader: (0)	Thanks for the clarification AussieRacer. My rims are the 18" M double spokes and as far as the guards are concerned, I have the standard M-sport suspension. Do you think it'll handle the 225/40 setup? And should I just use 225/40 for all 4 corners or double up on the rears?
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12-16-2009, 03:43 PM	#6
dk130i Private First Class 5 Rep 134 Posts Drives: Blue car Join Date: Jun 2009 Location: Sydney iTrader: (0)	225/40 will be fine, I have the same car/rims as you and I've tried the following combinations so far: 205 front 225 rear 225 front and 245 rear 225 both front and rear ....and prefer the 225 all 'round. Last edited by dk130i; 12-16-2009 at 04:42 PM..
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12-16-2009, 04:24 PM	#8
takahashi Retired trackie 36 Rep 1,527 Posts Drives: 1///M Join Date: Jul 2008 Location: Melbourne, Australia iTrader: (0)	There are also "tire calculator" out there. Google "tire calculator" in American spellings. The Vic guide also said no 25mm or wider, but please check NT.... it may be more relaxed and I know of some slight variation in rules for ride height between states/territories. __________________ TAKA 一仔BLOGブログ: BMW 1 series M 2011! Delivered 18/11/11.
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12-16-2009, 06:02 PM	#9
alik01 Lieutenant Colonel 51 Rep 1,792 Posts Drives: Slowly & Responsibly Join Date: Nov 2009 Location: Darwin, Australia iTrader: (0)	Thanks so much for all the info guys, really appreciate it. Checked the tire calculator as per Takahashi and the 225/40 only has 0.7% variance, which seems nominal. Also judging by dk130i's comments, 225/40 all around might be the go, hopefully the increased grip area up front should aid in mitigating the understeer a little bit. Thanks again guys.
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12-17-2009, 03:12 AM	#11
dr.bmw Chirurgeon 39 Rep 424 Posts Drives: 125i AW/CR Join Date: Apr 2009 Location: randwick iTrader: (0) Garage List 2008 125i [10.00]	I thought that because of different rim sizes front/rear, 225s up front will buldge out quite a bit? I think front rims are 7" and rears are 7.5" correct me if i'm wrong please __________________ E Pluribus Unum
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12-17-2009, 03:40 AM	#12
Taymaishu Banned 145 Rep 3,016 Posts Drives: I love massive black cocks Join Date: Jul 2009 Location: in my ass and around my mouth iTrader: (0) Garage List 2009 125i [5.50]	I run 225 (width) /45 (profile) /R17 (size). Trying to upgrade to 245's
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12-17-2009, 03:55 AM	#13
dr.bmw Chirurgeon 39 Rep 424 Posts Drives: 125i AW/CR Join Date: Apr 2009 Location: randwick iTrader: (0) Garage List 2008 125i [10.00]	cool got some pics of the front tyres' sidewalls? what brand? i'll be due for new set all around in a few months i think __________________ E Pluribus Unum
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12-17-2009, 05:12 AM	#15
alik01 Lieutenant Colonel 51 Rep 1,792 Posts Drives: Slowly & Responsibly Join Date: Nov 2009 Location: Darwin, Australia iTrader: (0)	Dk130i, definitely sounds like the 225 all around is the go, definitely want the chassis balance, and accelerator direction changes are nice thing to have, not that I do that sort of thing! The understeer is really prevalent on mine at the moment as the rear are brand new and the fronts are nearly shod! Hopefully I'll have these new shoes on before xmas!
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12-17-2009, 04:49 PM	#19
dr.bmw Chirurgeon 39 Rep 424 Posts Drives: 125i AW/CR Join Date: Apr 2009 Location: randwick iTrader: (0) Garage List 2008 125i [10.00]	dk130i Taymaishu's 125i is 17" all around, so is mine I've been toying with the idea of 225/40 all around but just not sure about those front rims coping with oversized tyre cheers __________________ E Pluribus Unum
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01-19-2010, 06:57 AM	#21
alik01 Lieutenant Colonel 51 Rep 1,792 Posts Drives: Slowly & Responsibly Join Date: Nov 2009 Location: Darwin, Australia iTrader: (0)	So, have had my new tires on or about a week now and wanted to break them in before passing on my impressions. I went with the PS2s with 225/40 all around. Got it from Tirerack.com and have to say I'm amazingly impressed, they handled everything beautifully. Had the wheels delivered less than 1 week from ordering, including wire transfer and all. Cost me around AU$1700 landed including $300 tax and customs. Which I am really happy about as I got it a lot cheaper and faster than anything here. Had the tires fitted, cost $135 with alignment. The fitting was the only unpleasant part as the Goodyear guys here detroyed the lip of the rim and scared some of the face - looks like they use a crowbar to lever off the runflats. Also mucked up the alignment. This was supposed to be me being taken care of! But they have agreed to repair and is getting sorted so not too fussed and this stuff just happens in Darwin, as I am findig out daily! But, the tyres are incredible! The ride is improved a thousand fold and has really helped with the understeer. They are so sticky even in the wet, it's amazing - and it gets crazy wet here, more rain in an hour than Victoria gets in a year or somthing like that! So steering feel is really good and the car feels really responsive! Also hardly see the traction control light anymore during normal driving! I haven't really pushed too much with the new tyres, wanted to get them fully run in. Will post up at the limit thoughts next week or so. But so far, would recommend to anyone!
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