New BBS CI-R Unlimited in Emira fitment

[Porter]

Highlighted on Instagram by KW Suspension Switzerland.

Claimed spec 20x9.0 front and 20x11.0 rear. Apparently these new "Unlimited" series wheels from BBS have integral adapters to vary the offset, so they can be matched to a wide range of cars and bolt patterns. Great idea, if it works and doesn't break under serious load. I trust these more than a "sandwich" bolt-through spacer though.

More info on the BBS Unlimited customizable offset system:

BBS Unlimited | Overview

bbs.com

Original context on Instagram:

 

[Porter]

There seem to be a few barriers to configuring an appropriate set on the BBS website for an Emira, though... bit of a head-scratcher considering they've clearly built at least one set. Hopefully they get this updated.

 

[Porter]

Based on the available specs, I suspect that this particular fitment was using Concavity 0 (zero) in the front and Concavity 2 in the rear. They have to be matched with a hub adapter and the minimum thickness of that adapter is 14mm, so those are the base wheel specs that are workable.

Front wheel 20 x 9.0 Concavity 0 is an ET72 offset, PCD 5x117.5. The minimum 14mm hub adapter brings that to ET58, PCD 5x114.3. The alternative 17mm adapter moves it out to ET55. [edit] Unknown which hub adapter they may have used, the 14mm would keep the scrub radius to near-zero (matching the stock tire centerline to steering axis relationship) so my guess is they used that.

Rear wheel 20 x 11.0 Concavity 2 is an ET70.5 offset, PCD 5x117.5. The minimum 14mm hub adapter brings that to ET56.5, PCD 5x114.3.
The alternative 17mm adapter moves it out to ET53.5, likely what was chosen for both scrub radius matching and aesthetic reasons.


These are an expensive but interesting option, honestly.

 

[KAR120C]

Great idea to quickly get a set that fits. I'm like you, I got stuck trying to configure. Also, looking at the available sizing, the hub adapters have the right bolt pattern, but I wasn't able to get comfortable with the center bores on the centering rings. My data on the Emira wheels may not be right, though.

I don't know where I got these numbers, but had a 69.1mm on the fronts and 68.06mm on the rears. Now I'm not so sure.

 

[Porter]

Great idea to quickly get a set that fits. I'm like you, I got stuck trying to configure. Also, looking at the available sizing, the hub adapters have the right bolt pattern, but I wasn't able to get comfortable with the center bores on the centering rings. My data on the Emira wheels may not be right, though.

Interestingly, the wheels bolt to the adapters when you take them on and off the car, not to the wheel hubs directly. They "convert" the car to 5x117.5 bolt pattern on a semi-permanent basis. So you're less dependent on the hubcentering ring to get the wheel concentric in any context other than the first install. I would still want it there for a variety of reasons, but it's not a 100% necessity unless they have some engineering reason I'm not aware of.

 

[KAR120C]

Based on the available specs, I suspect that this particular fitment was using Concavity 0 (zero) in the front and Concavity 2 in the rear. They have to be matched with a hub adapter and the minimum thickness of that adapter is 14mm, so those are the base wheel specs that are workable.

Front wheel 20 x 9.0 Concavity 0 is an ET72 offset, PCD 5x117.5. The minimum 14mm hub adapter brings that to ET58, PCD 5x114.3. The alternative 17mm adapter moves it out to ET55. Likely what was chosen.

Rear wheel 20 x 11.0 Concavity 2 is an ET70.5 offset, PCD 5x117.5. The minimum 14mm hub adapter brings that to ET56.5, PCD 5x114.3.
The alternative 17mm adapter moves it out to ET53.5, again likely what was chosen.


These are an expensive but interesting option, honestly.

Those offsets are great, I'd go with them, only 1mm off.

 

[TomAce]

I think this is very fresh news with these BBS wheels. And I also did not know that BBS is now owned by KW…

So the circle closes now.

 

[kitkat]

I love the FI-R/CI-R design and I know to keep scrub radius similar to stock they went with similar effective offsets but that 0 concavity front just looks bad.

 

[kitkat]

I can appreciate how much thought KW has been putting into these releases for the Emira, they're really sticking to the improving but not to the detriment of Lotus tuning.

 

[Porter]

I love the FI-R/CI-R design and I know to keep scrub radius similar to stock they went with similar effective offsets but that 0 concavity front just looks bad.

You can probably get the non-"unlimited" variant in an offset that is super close, without the 14mm to make up with the hub ring. Concavity 1 in that case. Let me do some looking.

 

[Porter]

You can probably get the non-"unlimited" variant in an offset that is super close, without the 14mm to make up with the hub ring. Concavity 1 in that case. Let me do some looking.

The closest CI-R (non-unlimited) variants in 5x114.3 PCD are 20x8.5 in a 43 offset, or 19x8.5 in a 43 offset. Both Concavity 1.

That's too low for Emira. And even if it were closer, like 48 or 50, it likely wouldn't do great things for steering with the altered scrub radius.

There are other BBS wheels that are way closer, for example the FI-R comes in 20x8.5 in ET54, but only in 130mm PCD for the Cayman/Boxster front. Similarly the rear in 20x11 ET50, but only in 130mm PCD for the rear of the Cayman GT4. Both unusable without a custom order.


So anyway, this Unlimited program looks really cool, but you do definitely sacrifice concavity to achieve the fitment flexibility.

 

[Porter]

Those offsets are great, I'd go with them, only 1mm off.

I updated the above... exact match offset isn't necessarily what you want if the rim width changes. The offset measures from the centerline of the wheel, so as the wheel width changes the offset has to shift slightly with it in order to keep the center of the wheel aligned with the steering axis. Rear is less sensitive to this but typically you still want to minimize deviation from the factory track center if you can.

One of the best calculators I've found online for this stuff is here... allows you to compare arbitrary wheel and tire combinations on the fly both visually and in comparison table form:

Rim & Tire Size Calculator. Custom Offsets

Tire Tech Information - The Wheel Fitment, Tyre Stretch, Rolling Radius and Speedometer Error Calculator. Play with specs, try different settings, compare results

www.wheel-size.com

 

[KAR120C]

I updated the above... exact match offset isn't necessarily what you want if the rim width changes. The offset measures from the centerline of the wheel, so as the wheel width changes the offset has to shift slightly with it in order to keep the center of the wheel aligned with the steering axis. Rear is less sensitive to this but typically you still want to minimize deviation from the factory track center if you can.

One of the best calculators I've found online for this stuff is here... allows you to compare arbitrary wheel and tire combinations on the fly both visually and in comparison table form:

Rim & Tire Size Calculator. Custom Offsets

Tire Tech Information - The Wheel Fitment, Tyre Stretch, Rolling Radius and Speedometer Error Calculator. Play with specs, try different settings, compare results

www.wheel-size.com

I was going with the OEM width, so the 1mm outboard offset works fine for me. I've gone with wider wheels/tires on a number of cars in the past, but never with my Lotus cars. I'll most likely keep the second set stock. I've always felt really good with the Lotus set-up. I probably won't change anything to start with except the alignment.

 

[KAR120C]

I updated the above... exact match offset isn't necessarily what you want if the rim width changes. The offset measures from the centerline of the wheel, so as the wheel width changes the offset has to shift slightly with it in order to keep the center of the wheel aligned with the steering axis. Rear is less sensitive to this but typically you still want to minimize deviation from the factory track center if you can.

One of the best calculators I've found online for this stuff is here... allows you to compare arbitrary wheel and tire combinations on the fly both visually and in comparison table form:

Rim & Tire Size Calculator. Custom Offsets

Tire Tech Information - The Wheel Fitment, Tyre Stretch, Rolling Radius and Speedometer Error Calculator. Play with specs, try different settings, compare results

www.wheel-size.com

The one I use most often is tiresize.com. It has less parameters, but lets you put spacers in and then overlays the before and after.

 

[Porter]

I was going with the OEM width, so the 1mm outboard offset works fine for me. I've gone with wider wheels/tires on a number of cars in the past, but never with my Lotus cars. I'll most likely keep the second set stock. I've always felt really good with the Lotus set-up. I probably won't change anything to start with except the alignment.

Gotta redo the math with the OEM widths. The offset of the base wheels is different on the 8.5 and 10.5.

 

[KAR120C]

Gotta redo the math with the OEM widths. The offset of the base wheels is different on the 8.5 and 10.5.

Yep, I did. Comes out good in the back and a little wonky in the front (4mm). That's right on the edge of acceptable for the fronts.

 

[KAR120C]

I'm seriously thinking about these for a cold weather set. I reached out to BBS and they gave me their specs for this build:

Wheel front	Wheel Rear	Tires front	Tires Rear	Adapter front	Adapter rear	Centering Rings /front & Rear	Assambly Kit
CI6201AD02 9x20 ET72	CI1701AD02 11x20 ET70,5	245/35 ZR20 GoodYear 95Y EAG F1 SuperSport XL FP	295/30 ZR20 GoodYear 101Y XL Eagle F1 Supersport	59003161 17mm	59003060 20mm	65251101 + 65B85901	68324129 + 68324244

This results in a small offset difference of +2mm front and +3.5 in the rear.

This adds up to about 2960 euros (incl. vat) + shipping. Not sure what the final $ cost would be after dropping VAT and adding back shipping and local taxes. But worse case about $3500 for the whole shebang, except tires!

 

[kitkat]

I'm seriously thinking about these for a cold weather set. I reached out to BBS and they gave me their specs for this build:

Wheel front	Wheel Rear	Tires front	Tires Rear	Adapter front	Adapter rear	Centering Rings /front & Rear	Assambly Kit
CI6201AD02 9x20 ET72	CI1701AD02 11x20 ET70,5	245/35 ZR20 GoodYear 95Y EAG F1 SuperSport XL FP	295/30 ZR20 GoodYear 101Y XL Eagle F1 Supersport	59003161 17mm	59003060 20mm	65251101 + 65B85901	68324129 + 68324244

This results in a small offset difference of +2mm front and +3.5 in the rear.

This adds up to about 2960 euros (incl. vat) + shipping. Not sure what the final $ cost would be after dropping VAT and adding back shipping and local taxes. But worse case about $3500 for the whole shebang, except tires!

I'd be keeping the OEM set as winter and these as summer IMHO -- that's just me.

 

[KAR120C]

I'd be keeping the OEM set as winter and these as summer IMHO -- that's just me.

That's also a possibility. I'll have to see them both in person to decide. And we're likely to be past the winter season before that will happen.

 

[JimH]

I'm seriously thinking about these for a cold weather set. I reached out to BBS and they gave me their specs for this build:

Wheel front	Wheel Rear	Tires front	Tires Rear	Adapter front	Adapter rear	Centering Rings /front & Rear	Assambly Kit
CI6201AD02 9x20 ET72	CI1701AD02 11x20 ET70,5	245/35 ZR20 GoodYear 95Y EAG F1 SuperSport XL FP	295/30 ZR20 GoodYear 101Y XL Eagle F1 Supersport	59003161 17mm	59003060 20mm	65251101 + 65B85901	68324129 + 68324244

This results in a small offset difference of +2mm front and +3.5 in the rear.

This adds up to about 2960 euros (incl. vat) + shipping. Not sure what the final $ cost would be after dropping VAT and adding back shipping and local taxes. But worse case about $3500 for the whole shebang, except tires!

If you need (or are obliged to fit by law in your territory/state) "true" winter tyres then the Lotus recommendation (excerpt from the user manual) is these :