[Mightymousemighty]

This has been going round the houses for some time, with no concise answer, just lots of debate on electric range, efficiency etc etc

Generally on the stock option tyres... I observe a community desire (I would prefer) to change the Bridgestone rubber to Michellin PSS.

So lets go on the presumption we are changing the tyres.....cause they are awesome

Has anybody actually fitted these to the 20" turbine or W-spoke alloys?

This is only an issue for the fronts as there is the correct size available for the rear (245/40 R20)

If so what Dimensions? Do they rub?

Stock

Front 215/45 R20 95W XL

Nearest MPSS size I can find 225/35R20

[stressdoc]

OK I might cross-post some of this info. First, there are several variants of Michelin Pilot Sports tires that are possible options. Here is a list of sizes for the MPSS. Note the diameter for both front and rear is about 27.5, 755 revs per mile, and rim width for front 7-8". So we want a close match for that. A 235/40 would be good, but Michelin does not make that size. The best is 245/35 for diameter, but that is too wide for rim and clearance. 235/35 is a bit better for the stock front rim. I plan to go 235/35 front, 265/30 rear. That is a 26.5 diameter, 790 revs per mile, 2" wider tire set up. Tire weights (22 lbs, 24 lbs) are the same as stock size. Definitely going to reduce gas mileage though.

for comparison, data on OEM front Bridgestone S001 l:
215/45R20 95W XL
Star BMW 280 A A 1,521 lbs. 50 psi 8/32" 22 lbs. 7-8" 7" 8.4" 6.5" 27.6" 754 PL

Michelin PSSS:
225/35ZR20 (90Y) XL
300 AA A 1,323 lbs. 50 psi 10/32" 22 lbs. 7.5-9" 8" 9.1" 8.8" 26.2" 793 FR

225/35ZR20 (90Y) XL
300 AA A 1,323 lbs. 50 psi 10/32" 22 lbs. 7.5-9" 8" 9.1" 8.8" 26.2" 793 FR

235/35ZR20 (92Y) XL
K1 Ferrari 300 AA A 1,389 lbs. 50 psi 10/32" 22 lbs. 8-9.5" 8.5" 9.5" 9" 26.5" 786 FR

235/35ZR20 (88Y) SL
2011 Production 300 AA A 1,235 lbs. 51 psi 10/32" 22 lbs. 8-9.5" 8.5" 9.5" 9" 26.5" FR

245/30ZR20 (90Y) XL
300 AA A 1,323 lbs. 50 psi 10/32" 23 lbs. 8-9" 8.5" 9.7" 9.7" 25.8" 805 FR

245/35ZR20 (95Y) XL
K1 Ferrari 300 AA A 1,521 lbs. 50 psi 9/32" 23 lbs. 8-9.5" 8.5" 9.8" 9.4" 26.8" 777 FR

245/35ZR20 (95Y) XL
K3 Ferrari 300 AA A 1,521 lbs. 50 psi 9/32" 23 lbs. 8-9.5" 8.5" 9.8" 8.8" 26.8" 777 FR

245/35ZR20 (95Y) XL
K2 Ferrari 300 AA A 1,521 lbs. 50 psi 9/32" 23 lbs. 8-9.5" 8.5" 9.8" 8.4" 26.8" 777 FR

245/35ZR20 (95Y) XL
300 AA A 1,521 lbs. 50 psi 10/32" 23 lbs. 8-9.5" 8.5" 9.8" 8.5" 26.8" 777 FR

245/40ZR20 (99Y) XL
Star BMW 300 AA A 1,709 lbs. 50 psi 9/32" 26 lbs. 8-9.5" 8.5" 9.8" 8.7" 27.7" 750 FR

245/40ZR20 (99Y) XL
300 AA A 1,709 lbs. 50 psi 10/32" 26 lbs. 8-9.5" 8.5" 9.8" 8.7" 27.7" 750 FR

245/45ZR20 (103Y) XL
300 AA A 1,929 lbs. 50 psi 10/32" 26 lbs. 7.5-9" 8" 9.6" 8.5" 28.7" 726 US

255/30ZR20 (92Y) XL
300 AA A 1,389 lbs. 50 psi 10/32" 23 lbs. 8.5-9.5" 9" 10.2" 8.8" 26.1" 798 FR

255/35ZR20 (97Y) XL
300 AA A 1,609 lbs. 50 psi 10/32" 25 lbs. 8.5-10" 9" 10.2" 9.2" 27" 770 FR

255/35ZR20 (97Y) RF
K2 Ferrari 300 AA A 1,609 lbs. 51 psi 7/32" 25 lbs. 8.5-10" 9" 10.2" 9.2" 27" 770 FR

255/40ZR20 (101Y) XL
N0(Porsche) 300 AA A 1,819 lbs. 50 psi 9/32" 27 lbs. 8.5-10" 9" 10.2" 10" 28" 742 FR

255/40ZR20 (101Y) XL
300 AA A 1,819 lbs. 50 psi 10/32" 28 lbs. 8.5-10" 9.5" 10.2" 9" 28" 742 US

255/45ZR20 (105Y) XL
300 AA A 2,039 lbs. 50 psi 10/32" 29 lbs. 8-9.5" 8.5" 10" 9" 29.1" 716 US

265/30ZR20 (94Y) XL
300 AA A 1,477 lbs. 50 psi 10/32" 26 lbs. 9-10" 9.5" 10.7" 10" 26.3" 791 US

265/30ZR20 (94Y) XL
Star BMW 300 AA A 1,477 lbs. 50 psi /32" 24 lbs. 0-0" 8.9" FR

265/35ZR20 (99Y) XL
Star BMW 300 AA A 1,709 lbs. 50 psi 9/32" 25 lbs. 9-10.5" 9.5" 10.7" 9.7" 27.3" 761 FR

275/30ZR20 (97Y) XL
300 AA A 1,609 lbs. 50 psi 10/32" 26 lbs. 9-10" 9.5" 10.9" 10.1" 26.5" 784 FR

275/35ZR20 (102Y) XL
300 AA A 1,874 lbs. 50 psi 10/32" 27 lbs. 9-11" 9.5" 10.9" 10.1" 27.6" 755 FR

275/35ZR20 (102Y) XL
Star BMW 300 AA A 1,874 lbs. 50 psi 9/32" 27 lbs. 9-11" 9.5" 10.9" 9.7" 27.6" 755 FR

285/25ZR20 (93Y) XL
300 AA A 1,433 lbs. 50 psi 10/32" 28 lbs. 10.5-10.5" 10.5" 11.6" 10.5" 25.6" 813 FR

285/30ZR20 (99Y) XL
300 AA A 1,709 lbs. 50 psi 10/32" 27 lbs. 9.5-10.5" 10" 11.4" 10.2" 26.8" 777 FR

285/30ZR20 (99Y) XL
K1 Ferrari 300 AA A 1,709 lbs. 50 psi 7/32" 24 lbs. 9.5-10.5" 10" 11.4" 9.5" 26.8" 777 FR

285/30ZR20 (99Y) XL
Star BMW 300 AA A 1,709 lbs. 50 psi /32" 26 lbs. 0-0" 9.9" FR

285/35ZR20 (104Y) XL
K2 Ferrari 300 AA A 1,984 lbs. 50 psi 9/32" 30 lbs. 9.5-11" 10" 11.4" 10.1" 27.9" 746 FR

285/35ZR20 (104Y) XL
300 AA A 1,984 lbs. 50 psi 10/32" 30 lbs. 9.5-11" 10" 11.4" 10.5" 27.9" 746 US

295/25ZR20 (95Y) XL
300 AA A 1,521 lbs. 50 psi 10/32" 27 lbs. 10-11" 10.5" 11.9" 11.2" 25.8" 805 FR

295/30ZR20 (101Y) XL
MO Mercedes 300 AA A 1,819 lbs. 50 psi 10/32" 29 lbs. 10-11" 10.5" 11.9" 9.4" 27" 770 FR

295/30ZR20 (101Y) XL
300 AA A 1,819 lbs. 50 psi 10/32" 29 lbs. 10-11" 10.5" 11.9" 11.5" 27" FR

295/30ZR20 (101Y) XL
Star BMW 300 AA A 1,819 lbs. 50 psi 9/32" 29 lbs. 10-11" 10.5" 11.9" 11.6" 27" 770 FR

295/35ZR20 (105Y) XL
K1 Ferrari 300 AA A 2,039 lbs. 50 psi 9/32" 30 lbs. 10-11.5" 10.5" 11.9" 12" 28.1" 740 FR

295/35ZR20 (101Y) SL
K1 Ferrari 300 AA A 1,819 lbs. 51 psi 9/32" 31 lbs. 10-11.5" 10.5" 11.9" 11.6" 28.1" 740 FR

295/35ZR20 (105Y) XL
N0(Porsche) 300 AA A 2,039 lbs. 50 psi 9/32" 30 lbs. 10-11.5" 10.5" 11.9" 11.5" 28.1"740 FR

305/25ZR20 (97Y) XL
300 AA A 1,609 lbs. 50 psi 10/32" 27 lbs. 10.5-11.5" 11" 12.3" 11.1" 26" 801 FR

305/30ZR20 (103Y) XL
K3 Ferrari 300 AA A 1,929 lbs. 50 psi 9/32" 31 lbs. 10.5-11.5" 11" 12.3" 11.4" 27.2" 764 FR

305/30ZR20 (103Y) XL
300 AA A 1,929 lbs. 50 psi 9/32" 31 lbs. 10.5-11.5" 11" 12.3" 11.8" 27.2" 764 FR

315/35ZR20 (110Y) XL
K1 Ferrari 300 AA A 2,337 lbs. 50 psi 7/32" 33 lbs. 10.5-12.5" 11" 12.6" 11.5" 28.7" 726 FR

315/35ZR20 (110Y) XL
K2 Ferrari 300 AA A 2,337 lbs. 50 psi 10/32" 34 lbs. 10.5-12.5" 11" 12.6" 11.6" 28.7" 726 FR

325/25ZR20 (101Y) XL
300 AA A 1,819 lbs. 50 psi 9/32" 31 lbs. 11.5-12.5" 12" 13.2" 13.1" 26.3" 788 FR

335/30ZR20 (108Y) XL
N0(Porsche) 300 AA A 2,205 lbs. 50 psi 9/32" 35 lbs. 11.5-12.5" 12" 13.5" 13" 28" 744 US

345/30ZR20 (106Y) SL
300 AA A 2,094 lbs. 51 psi 10/32" 35 lbs. 12-13" 12.5" 14" 12.7" 28.1" 716 FR

[Mightymousemighty]

thanks mate realistically think the 225 and 235's are the only option due to the 7.5J alloy.

The 225/35R20 seems closest to stock size.

[ElSpa]

they will be a lot smaller

[Mightymousemighty]

Originally Posted by ElSpa

they will be a lot smaller

what do you suggest? thanks

[Aye-eight]

I think this means you can do it. But your front will sit 18 mm lower than current (that's not a little if you're starting with a relatively low car) and you will introduce a speedo error (albeit on the "safe" side).

[Aye-eight]

Now, I don't know about Scotland. But here in Switzerland, I would have to get this tire change checked and approved by the DMV / MOT, whatever you call it, because it's not listed as an approved size in the car's papers. Police here are occasionally fond of pulling people over and checking for correct tires, exhausts, lights, etc.

[363ny]

Originally Posted by Mightymousemighty

This has been going round the houses for some time, with no concise answer, just lots of debate on electric range, efficiency etc etc

Generally on the stock option tyres... I observe a community desire (I would prefer) to change the Bridgestone rubber to Michellin PSS.

So lets go on the presumption we are changing the tyres.....cause they are awesome

Has anybody actually fitted these to the 20" turbine or W-spoke alloys?

This is only an issue for the fronts as there is the correct size available for the rear (245/40 R20)

If so what Dimensions? Do they rub?

Stock

Front 215/45 R20 95W XL

Nearest MPSS size I can find 225/35R20

I too would prefer to be running with MPSS opposed to the Bridgestones. I wonder if the rear wheels would fit in the front and then we could run a square set up of 245/40 R20. Under this approach we have very minimal chnage to the diameter, revs/mile and circumference as compared to the stock set up and we getting a 1" more of rubber on each side in the front. Question is will they fit and not scrape?

[Mightymousemighty]

Originally Posted by Aye-eight

Now, I don't know about Scotland. But here in Switzerland, I would have to get this tire change checked and approved by the DMV / MOT, whatever you call it, because it's not listed as an approved size in the car's papers. Police here are occasionally fond of pulling people over and checking for correct tires, exhausts, lights, etc.

As long as they are stock alloys and the tyre/rim does not move outside the top boundary of the wheel arch you are OK

Otherwise you need to inform the insurance company

[ElSpa]

Originally Posted by Aye-eight

I think this means you can do it. But your front will sit 18 mm lower than current (that's not a little if you're starting with a relatively low car) and you will introduce a speedo error (albeit on the "safe" side).

No, it won't work because the car will read more revolutions on the front axle then the rear, thinks it's spinning constantly and traction control will be

[Mightymousemighty]

Originally Posted by Aye-eight

I think this means you can do it. But your front will sit 18 mm lower than current (that's not a little if you're starting with a relatively low car) and you will introduce a speedo error (albeit on the "safe" side).

The point about the front being lower for kerbs is a very good point.

[Mightymousemighty]

Originally Posted by 363ny

I too would prefer to be running with MPSS opposed to the Bridgestones. I wonder if the rear wheels would fit in the front and then we could run a square set up of 245/40 R20. Under this approach we have very minimal chnage to the diameter, revs/mile and circumference as compared to the stock set up and we getting a 1" more of rubber on each side in the front. Question is will they fit and not scrape?

That is pretty much be the solution as it's near identical.

Would they fit on a 7.5J alloy? Is 8" not minimum?

Expert opinions please

[NGR]

Originally Posted by Mightymousemighty

The point about the front being lower for kerbs is a very good point.

Effectively you're reducing the gearing to the front axle. I would expect
traction control to kick in more often especially when in "e-drive" mode. My front end is very fond of breaking traction with the stock size and sticky s001 compound.

Don't know if it would be noticeable though....guinea pig time !

[stressdoc]

In general it is a good idea to keep the diameter ratio constant (same as OEM) between front and rear. Hence my suggestion above that the 235/35 front matched with 265/30 rear is the best option for Michelin. Although the rolling diameter is about an inch less, and the width 2 inches more (a bit wider than ideal for narrow front rim), the front/rear ratio is constant.

The ideal $ no object solution is to opt for BBS RI-D forged ultralight rims in proper widths.

[Mightymousemighty]

Originally Posted by stressdoc

In general it is a good idea to keep the diameter ratio constant (same as OEM) between front and rear. Hence my suggestion above that the 235/35 front matched with 265/30 rear is the best option for Michelin. Although the rolling diameter is about an inch less, and the width 2 inches more (a bit wider than ideal for narrow front rim), the front/rear ratio is constant.

The ideal $ no object solution is to opt for BBS RI-D forged ultralight rims in proper widths.

thanks but the ideal solution would be for Michelin to stop being dicks and get them made to the stock sizes

In anybodies view would it fit on a 7.5"? did some reading about poor handling under extreme cornering

[SlipperyGary]

Originally Posted by Mightymousemighty

thanks but the ideal solution would be for Michelin to stop being dicks and get them made to the stock sizes

In anybodies view would it fit on a 7.5"? did some reading about poor handling under extreme cornering

I guess it depends on how extreme the corning is that you are planning on doing. For normal driving on the street I can't imagine that the additional width would make any difference with regard to the rim size. You are not going to pop a bead under normal driving.

In autocross, I routinely see people putting tires on that are wider than the recommendation for the wheel width and I haven't seen anyone pop a bead.

When it's time for me to replace my tires, I plan to put 245's up front and 275's in the rear. Until then, I won't have any first hand experience to share.

[Mightymousemighty]

Originally Posted by SlipperyGary

I guess it depends on how extreme the corning is that you are planning on doing. For normal driving on the street I can't imagine that the additional width would make any difference with regard to the rim size. You are not going to pop a bead under normal driving.

In autocross, I routinely see people putting tires on that are wider than the recommendation for the wheel width and I haven't seen anyone pop a bead.

When it's time for me to replace my tires, I plan to put 245's up front and 275's in the rear. Until then, I won't have any first hand experience to share.

Understand your point. If 235's are too big for the front are you not pushing it with 245's?

[Groundhog]

Not to rain on everyone's parade about more grip but Chris Harris' words keep ringing in my head; with wider tires comes less steering feel.

Anyone running the skinny 195 rubber?

http://www.roadandtrack.com/new-cars...-chris-harris/

A small, one-word caveat: understeer. For all Munich's talk of balanced weight distribution and a center of gravity just 18 inches off the ground, the front tire choice shows that BMW has been cautious with the i8's fundamental grip. Those tires are a weeny 215-section, and that's only if you choose the optional wide ones. Standard fit is a 195 front on a 20-inch rim.

I'd love to see how the handling balance changes on thinner rubber. In most cases, on the optional tires, the i8 gradually pushes its nose wide. Nothing too unpleasant, but it's not that adventurous, either. The narrow paws should bring delicious steering, but with the i8's electrically assisted steering rack—as with most of this type—there's little sense of connection. You never feel blinded by it, but you can't read the road surface through the jingles in your hands, because there are no jingles.

[SlipperyGary]

Originally Posted by Mightymousemighty

Understand your point. If 235's are too big for the front are you not pushing it with 245's?

I've read that people are running the 245's from the rear on the front without any problem, so I thought I'd give it a try.

[Mightymousemighty]

Well I had her on a ramp today looking with a body shop at clearances for oversized tyres on stock 7.5/8.5" staggered turbine rims i.e. michellin supersports.

My rears are still legal but I'm not comfortable with such low tread.

There are serious clearance issues in the front and rear. without spacers or changing offsets on stock turbines I think it's a risk putting anything but stock Bridgestones.

You might be able to squeeze 10mm on the inside but that would be 1-2 mm away from suspension components, body work etc

Please someone convince me I'm wrong?

[MKSixer]

Originally Posted by Mightymousemighty

Well I had her on a ramp today looking with a body shop at clearances for oversized tyres on stock 7.5/8.5" staggered turbine rims i.e. michellin supersports.

My rears are still legal but I'm not comfortable with such low tread.

There are serious clearance issues in the front and rear. without spacers or changing offsets on stock turbines I think it's a risk putting anything but stock Bridgestones.

You might be able to squeeze 10mm on the inside but that would be 1-2 mm away from suspension components, body work etc

Please someone convince me I'm wrong?

I'm running 255s in the front and 275s in the rear with no clearance problems either statically or dynamically. The understeer is gone and the car is now very well balanced. I'm still running the stock "W" wheels with no fitment problems. This, imho, is the way the car should have come from the factory. No contest.

[Mightymousemighty]

Originally Posted by MKSixer

I'm running 255s in the front and 275s in the rear with no clearance problems either statically or dynamically. The understeer is gone and the car is now very well balanced. I'm still running the stock "W" wheels with no fitment problems. This, imho, is the way the car should have come from the factory. No contest.

Thanks matey

Can you give me the specific tyre size/ make and brand please (just want to be double sure we are talking about MPSS's)? How do they look as far as sidewall bulge? Any pics? Thanks in advance