BBS E50 on a BBi

Continuing with my BBLM inspired mods to my '83 BBi, I am working on switching from the 17" Group 4 wheels I have now, to a set of BBS E50. Although not everyone's cup of tea, I personally don't think it gets any more 80s cool than center-lock E50s. I'm willing to put in the effort (it's a process just to get them, and then to maintain them).

I'm by no means an expert on 80s racing, but I think it's more than fair to say that the BBS E50 (and its variants) were very popular. It seems many (most?) of the BBLM cars ran the E50 (stepped up to 16"), but you'll find BMW, Volvo and Porsche also ran them (sometimes with the addition of the "turbo fan").

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It seems some of the Koenig cars also ran BBS E50, but in 15" (no step up).

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For those who don't know, the E50 is a three-piece wheel: a magnesium "center", with an aluminum inner "barrel" (typically raw or brushed), and an aluminum outer "lip" (typically polished). The barrels and lips come in various sizes allowing you to mix and match to dial in the ideal diameter, overall width, and offset.

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I was able to source a correct (pretty sure...) center-lock E50 set for the Boxer. I also purchased a set of hub assemblies from Hill Engineering so I don't have to pillage the stock ones I moved from the TRX wheels to the Group 4. I also have a spare set of wheel "trim" that covers the hub assembly bolts. So far, everything seems to fit perfect.

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Side note, but BBS will make you a brand new set of E50 for $1,300 each. The wait time is anywhere between one and three years.

My current plan (it could change), is to "double step" the 15" centers to 17"; with 225mm tires on 8.5" wheels in the front, and 255mm tires on 9.5" wheels in the rear. The tire / wheel choices are based around the idea of more support under the tire is better for performance (track time comparison). These widths should result in a slight stretch (not Singer levels). Also, with a wider rear lip, I can make the alignment of the wheel / fenders the same between the front and rear – effectively just inside the fender.

I'd like to keep the overall diameter somewhat close to stock; which makes tire choices somewhat limited (almost all the Summer performance tires have gone full low-profile these days). If I go with 225x50 and 255x45, I can use the Conti ExtremeContact Sport. Unfortunately, the Pilot Sport 4S isn't really an option unless I go up to 265mm; which would also mean going to 10" rear wheel. Not the end of the world, but I think I'd prefer to keep the rear at 9.5".

There are many many variables to play with that effect performance, tire availability, and aesthetic. I've tried to find that sweet spot, but it's hard to know for sure until the wheels are actually on the car and I've had some seat time. I'm currently waiting on new 17" BBS rims to replace the 16" that came with the centers. I'll post pics once I have the new rims.

 

Gottis are cool too, and definitely period correct. They look great on the Koenig Boxers. I just personally have a soft spot for the the BBS basketweave / mesh pattern.

 

Status update.

I received new rims from BBS. I was a little concerned if stepping up from 15" to 17" would have weird proportions, but I'm happy with how they look as I actually like the larger polished area (18" would be too much, IMO). I also attempted to offset the wheels so they both align with the fender. After test fitting, they're both 24mm from the edge; which I think will be perfect (hard to know for sure without tires). The outer flange of the rim is 0.5", so that would push the tires inward 36mm from the fender edge. Basically, the tires will both fill the fender the same amount (just shy of the edge).

For anyone curious, these are 8.5" in the front (5" inner, 3.5" outer) and 9.5" in the rear (5" inner, 4.5" outer). This gives the rear a subtle "deep dish" look (not as exaggerated as the Koenig or BBLM cars).

Now that I know the wheels fit, next is tires.

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In an attempt to mitigate downtime if one of these centers goes bad, I 3D scanned one and reverse engineered. As a test, I purchased a few different gold paints and 3D printed a pie slice of the center to experiment on. Looks like it'd cost $2k to 3D print one of these in aluminum. I think CNC would be cheaper, but 3D printing has a more similar look to cast. BBS will make a brand new center in magnesium, but the turnaround time is 1-3 years...

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Maybe I can turn these into book ends when I'm finished

 

Not sure. I'd need to do some more research before really saying one way or the other. From what I've found, there are pros/cons to each (as far as "strength").

I've tried to destroy 3D printed aluminum parts, and it was surprisingly strong. It did not crack along a "layer line" like you might expect. It essentially deformed just like any other aluminum part.

I'm currently running 3D printed exhaust in stainless steel, which also seems to be holding up just fine (we'll see).

I should check the price to CNC just for comparison sake. The thing is, CNC just always looks like CNC. It's not just surface texture.

 

Okay, I was curious so I ran some CNC quotes (6061 Alu).

- Xometry (US): $1800
- Xometry (China) $700
- PCBWay: $1000
- Protolabs (US): requires manual quote
- PartsBadger: requires a manual quote

So basically, it's 65% cheaper to CNC vs 3D print (both in China). CNC parts always just look like they were CNC'd (which I don't love), but for less than half the price, might be hard to justify 3D printing.

 

Quick up on the CNC quotes. Protolabs came back with $3,900 (for one). In my experience, they are always the most expensive option, but I've heard good things about their quality, and the work is done in the US.

 

Little update. I've been preoccupied with other projects, so it's been slow going. Almost ready for tires though.

I repainted the centers with GrimmSpeed BBS gold. It looks almost identical to the original gold (less yellow, more bronze). I experimented with a few different "gold" paints out there that were specifically marketed as "BBS gold". According to BBS Motorsport America, there really is no such thing, the color has changed over the years, and they don't really share how they do it. Anyway, I'm happy with this color.

I waited seven days for the gold to cure before hitting them with a satin 2k clear; which basically didn't change the sheen at all (which I prefer). Then more waiting / curing.

In going with the BBLM motif (the car as a whole, but especially the wheels), I was able to find NOS BBLM wheel nuts! They're a more simple design than the road car nuts with the embossed cavallino. Not sure if Koenig used the same ones, but they look similar.

Attached are pics of the wheel assembly. Next up is ordering / installing / balancing the tires. I may wait until I have the new shocks before installing the tires as the total diameter will be slightly different and I'll just have to readjust the preload all over again. We'll see.

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After months of research, sourcing rare parts, stressing over shades of gold, offsets, ride height, and stretch, I finally have the wheels on the car. I'm really happy with how it's turned out. It's definitely very 80s race car; which I think works well with the whole modificata theme I've been going for (white quad exhaust, ITBs, roof scoops, etc.). A few more details / thoughts below.

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Tires

For tires, I settled on Continental ExtremeContact Sport02. It is very difficult to find performance tires with a taller side wall these days. Nitto makes a taller sidewall, but I ultimately went with Conti. The dimensions are 225/50R17 on an 8.5" wheel in the front, and 255/45R17 on a 9.5" wheel in the rear. This gives the tires a slight "stretch". Overall, the total diameter is 26" (vs 26.7" stock). Since these are three piece wheels, I was able to adjust the offset to better align the outer wheel edge with the fenders.

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Ride Height

There's too much fender gap at this point. I am working on a custom set of shocks that will allow for adjusting height (along with compression and rebound). I'm not looking to remove the gap, just bring it down a little. For one, I don't want the car to scrape. Two, anything more than an inch will start messing with suspension geometry and requires lots of other things to change. Three, it's part of the character of the car to have some gap (even if apparently Fioravanti originally designed the car not to have a gap).

Wheel Nut

I was able find an axle wheel nut socket for commercial vehicles that works with the BBLM hex nut. I made some minor tweaks as the tolerances were just a bit too tight. These are 80mm WAF.

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Handling

Honestly, I didn't expect the handling to change at all vs the Primary 3 I have on the Group 4 wheels, but it did. These tires bite sooner. The Primacy 3 always had a "numb on center" feel that I didn't like. I'm guessing this is attributed to the side wall stiffness, but I can't say for sure. Any additional changes to handling will come after I change out the shocks. Then I'll really dial in the toe / camber.

 

Thanks. I worked with BBS Motorsport America for a lot of this. Eric helped me date the centers, and source brand new parts to build up the wheels. So the rims and hardware are all brand new BBS parts. They'll even make brand new magnesium E50 centers if you want – they just don't advertise it.