[stressdoc]

From conversation with BBS: [note: unsprung weight savings of about 6 lbs. per wheel. That will have significant performance effects. I would personally opt for 235/35 and 265/30 tire sizes]

"BBS-Japan makes an RI-D wheel that should work. They are 20x8.5 et41 & 20x10 et45. Again, this rear, I feel, will be a little aggressive; tire selection will be important. These wheels are listed on their site at 17.4 lbs & 18.5 lbs each for the front and rear respectively.

Keep in mind that going to a wider wheel will necessitate a wider tire. A switch from the OE 215/45 & 245/40 to a more sporty/attractive 245/40 & 285/35 will likely add 3 to 4 pound per tire so some of the wheel savings will be undone.

A photo of the wheel is attached.
They are made in Silver, Diamond Black (as in the photo), & Matte Black.

These are special order so current ETAs are not exactly known… If interested I will request this info from BBS-Japan."

Robert Way
Phone: 770.967.9848
BBS of America, Inc.
§ http://www.bbs-usa.com/ §

[Amgeater2]

Originally Posted by stressdoc

From conversation with BBS: [note: unsprung weight savings of about 6 lbs. per wheel. That will have significant performance effects. I would personally opt for 235/40 and 265/35 tire sizes]

"BBS-Japan makes an RI-D wheel that should work. They are 20x8.5 et41 & 20x10 et45. Again, this rear, I feel, will be a little aggressive; tire selection will be important. These wheels are listed on their site at 17.4 lbs & 18.5 lbs each for the front and rear respectively.

Keep in mind that going to a wider wheel will necessitate a wider tire. A switch from the OE 215/45 & 245/40 to a more sporty/attractive 245/40 & 285/35 will likely add 3 to 4 pound per tire so some of the wheel savings will be undone.

A photo of the wheel is attached.
They are made in Silver, Diamond Black (as in the photo), & Matte Black.

These are special order so current ETAs are not exactly known… If interested I will request this info from BBS-Japan."

Robert Way
Phone: 770.967.9848
BBS of America, Inc.
§ http://www.bbs-usa.com/ §

Why will you go with a 235 & 265 set up ? First the overall diameter is off since the factory is 27.71 and your set up is 27.30

Also the width of those rims require a 245/40 and 275/35 since the car already brings the 245/40 on the rear all you need is the 275/35 and your are done ! Btw the 10 inch width with a 45 offset will be just fine

[stressdoc]

I agree that fitting the rears on the front and sticking 275/35 on rear would be great.
Key issue is weight reduction. BBS FI-R and DI-R are amazing forged rims.

[Jo-Sta07]

That's so light. Very interested. I'm also surprised it only represents 6 pounds per wheel. I'd think more like 9/10 pounds.

[MKSixer]

Originally Posted by stressdoc

I agree that fitting the rears on the front and sticking 275/35 on rear would be great.
Key issue is weight reduction. BBS FI-R and DI-R are amazing forged rims.

I have 275s on the rear and they look and work perfectly. These wheels look amazing and offer significant weight savings! Huge win!!

[Twitch Massacre]

I'm rocking chunky 285s on the rears and still wish they were wider.

[Amgeater2]

Originally Posted by Twitch Massacre

I'm rocking chunky 285s on the rears and still wish they were wider.

Correct on the same boat here, the truth of the matter here is that 14-16 pounds in weight reduction is not going to do great things. In fact won't do anything IMO but going with your set up 235 & 265 you will continue to have the narrow tire syndrome (that looks horrible on this platform) and no to mention traction problems... But hey to each his own enjoy !

[MKSixer]

Originally Posted by Amgeater2

Correct on the same boat here, the truth of the matter here is that 14-16 pounds in weight reduction is not going to do great things. In fact won't do anything IMO but going with your set up 235 & 265 you will continue to have the narrow tire syndrome (that looks horrible on this platform) and no to mention traction problems... But hey to each his own enjoy !

A quick primer on the importance of wheel mass, inertia, and angular velocity. Cheers-mk

http://www.tuneruniversity.com/blog/...t-people-down/

[Jo-Sta07]

Originally Posted by MKSixer

A quick primer on the importance of wheel mass, inertia, and angular velocity. Cheers-mk

http://www.tuneruniversity.com/blog/...t-people-down/

Bump

in reality I believe these wheels may save closer to 30-35 pounds (maybe 25 factoring in tires) which is pretty massive. Should translate to performance gains worth close to 100 pounds of weight savings above the wheel

[Amgeater2]

Originally Posted by MKSixer

A quick primer on the importance of wheel mass, inertia, and angular velocity. Cheers-mk

http://www.tuneruniversity.com/blog/...t-people-down/

That information is relevant when you are adding weight to the car with a new set of wheels, in this case he is taking weight off with either set up. Also the add/article is not that great, if anything on that matter please refer to how weight to ratio works.

[MKSixer]

Originally Posted by Amgeater2

That information is relevant when you are adding weight to the car with a new set of wheels, in this case he is taking weight off with either set up. Also the add/article is not that great, if anything on that matter please refer to how weight to ratio works.

I understand that he is taking weight off the vehicle. Please reference the highlighted portion of his post that I quoted. He stated that it would not make a big difference.

The information I posted says different as do the laws of physics. Reducing the amount of unsprung mass (Which is what the brakes, wheels, and tires are in street cars, improves performance by lowering the effort necessary to change any parameter from it's state at a given moment in time. In cars with identical performance but fitted with a different wheel/tire combinations, the car with the lighter wheel/tire combination will fare better in overall performance.

That is a quick and dirty explanation of the phenomenon. If you want detailed information, I can provide articles from Race Car Engineering that will provide you with more math than than you bargained for.

Cheers-mk

[stressdoc]

Correct.

Originally Posted by MKSixer

I understand that he is taking weight off the vehicle. Please reference the highlighted portion of his post that I quoted. He stated that it would not make a big difference.

The information I posted says different as do the laws of physics. Reducing the amount of unsprung mass (Which is what the brakes, wheels, and tires are in street cars, improves performance by lowering the effort necessary to change any parameter from it's state at a given moment in time. In cars with identical performance but fitted with a different wheel/tire combinations, the car with the lighter wheel/tire combination will fare better in overall performance.

That is a quick and dirty explanation of the phenomenon. If you want detailed information, I can provide articles from Race Car Engineering that will provide you with more math than than you bargained for.

Cheers-mk

[Amgeater2]

Originally Posted by MKSixer

I understand that he is taking weight off the vehicle. Please reference the highlighted portion of his post that I quoted. He stated that it would not make a big difference.

The information I posted says different as do the laws of physics. Reducing the amount of unsprung mass (Which is what the brakes, wheels, and tires are in street cars, improves performance by lowering the effort necessary to change any parameter from it's state at a given moment in time. In cars with identical performance but fitted with a different wheel/tire combinations, the car with the lighter wheel/tire combination will fare better in overall performance.

That is a quick and dirty explanation of the phenomenon. If you want detailed information, I can provide articles from Race Car Engineering that will provide you with more math than than you bargained for.

Cheers-mk

I never said other wise, what I was referring to was to the difference of weight between his set up 235 & 265 rather than 245 & 275 which if you want to go to the the race and performance aspects car without grip or proper tire set up means nothing... But I do get your point and I completely agree I regards to weight reduction but in this case it's a bit difference IMO

[stressdoc]

Ahhh, that explains it. Yes I agree that the 1 lbs. difference btw 235 / 265 versus 245 / 275 would not be significant, and a tradeoff with the potential increase in performance from the wider tires. That we all agree on. Likewise, we all agree that 18 lbs. rims would be a significant performance upgrade over the stock rims. Much more so than the 18 lbs. reduction from the titanium exhaust, for example.

Mind you, most weight reduction mods for the i8 are $$$. A set of BBS forged would set you back $8k or more. I wish BMW had fitted them stock, as they would make great sense for this car.

Originally Posted by Amgeater2

I never said other wise, what I was referring to was to the difference of weight between his set up 235 & 265 rather than 245 & 275 which if you want to go to the the race and performance aspects car without grip or proper tire set up means nothing... But I do get your point and I completely agree I regards to weight reduction but in this case it's a bit difference IMO

[Jo-Sta07]

Originally Posted by stressdoc

Ahhh, that explains it. Yes I agree that the 1 lbs. difference btw 235 / 265 versus 245 / 275 would not be significant, and a tradeoff with the potential increase in performance from the wider tires. That we all agree on. Likewise, we all agree that 18 lbs. rims would be a significant performance upgrade over the stock rims. Much more so than the 18 lbs. reduction from the titanium exhaust, for example.

Mind you, most weight reduction mods for the i8 are $$$. A set of BBS forged would set you back $8k or more. I wish BMW had fitted them stock, as they would make great sense for this car.

I wish as well. BBS rims are probably the best quality forged aluminum and magnesium (big $$$) rims available. They make the Weissach wheels for the Porsche 918 and also make the wheels for the Veyron/Chiron. I'd love BMW to include a set of aluminum BBS forged wheels as an option with the next i8.

[stressdoc]

Originally Posted by Jo-Sta07

I wish as well. BBS rims are probably the best quality forged aluminum and magnesium (big $$$) rims available. They make the Weissach wheels for the Porsche 918 and also make the wheels for the Veyron/Chiron. I'd love BMW to include a set of aluminum BBS forged wheels as an option with the next i8.

I would pay $5k for such an option. Increased fuel economy, acceleration, and better handling. Much more value than laser lights or leather engine cover...

We should develop a concerted effort here to lobby BMW Performance to offer products like this for the i8. We may be a tiny group, but the i8 is the flagship for BMW's future, and we are highly motivated to improve our i8s.

[JasH]

Originally Posted by stressdoc

I would pay $5k for such an option. Increased fuel economy, acceleration, and better handling. Much more value than laser lights or leather engine cover...

We should develop a concerted effort here to lobby BMW Performance to offer products like this for the i8. We may be a tiny group, but the i8 is the flagship for BMW's future, and we are highly motivated to improve our i8s.

Agreed

[mws]

Originally Posted by Jo-Sta07

That's so light. Very interested. I'm also surprised it only represents 6 pounds per wheel. I'd think more like 9/10 pounds.

that is because most stockers, like 625 wheels are about 24-25 lbs per wheel. but be careful, if you go with any tire other than the stock 215 and 245 S001s which are especially light tires, you can take that 6 away and add another 2-3 lbs more per tire, easily (even if the tire is the same exact size). I get this info from Tirerack.com by clicking around on specifications. You can see tire weights.