"In this entry, I explore new wheel fitment possibilities opened up by the wider fenders in preparation for the CSL style forged wheel program. I include fitment tables and in-depth specs. "
- Matt

Test fits, fits, and more test fits. 

The widened carbon fenders have been painted and sitting for a little over 6 months due to the bound-to-happen "Hiatus" in the complete restoration process. 

They had previously been satisfactorily test fitted for their alignment with the original metal doors. With the arrival of the carbon doors, the fenders were again test fitted in "We just wanted to be sure."

This test was in itself more about the doors than the fenders, yet it was a reminder about the quality of these fenders. I was also reminded of just how light they are, coming in at 1.2 kg / 2.6 lbs. 

Yet, we still had no idea how 10mm at the top of the arch would actually translate in terms of wheel fitments; it is is the missing piece of information for many.

A first step in a new world. 

With the fenders partially bolted on the car along with the 1:1 CSL carbon bumper, it was time to explore wheel fitments with the original Competition (CS/ZCP) wheels. 

I've had this used ZCP set repaired, sealed and sanded ready for paint since February 2022. It's been laying around the shop ever since. They are Genuine BMW original flow formed wheels manufactured by BBS. 

A refresher on wheel specs.  

Before I dive into my preliminary fitments with the CS wheels, let's set up expectations with a comparison with the original CSL and usual aftermarket fitments.

What matters most in the context of the widened carbon fenders will be front wheel and tire fitment. 

The original 163Ms. 

The original Competition wheels were partially derived from the CSL. The front wheel specs were originally more aggressive, and slightly wider. Still, the CS and CSL wheels were both filed under the 163M style. 

Widths	Offsets	Tires
ZCP Wheels
19x8.0	+47	225/40/19
19x9.5	+27	255/35/19
CSL Wheels
19x8.5	+44	235/35/19
19x9.5	+27	265/30/19

Aftermarket fitments. 

As a disclaimer, my fitment goals are personally oriented for road & track; it needs to remain functional in the street. 

Precisely, it needs to remain compliant at full locks and tuck inside the fender on full compression with the original fender liners without having to run negative camber in excess of -2.0. 

The camber restrictions require the use of an aftermarket coilover system with camber plates. Precise control over ride height and alignment settings are fundamentals to proper wheel fitment.

Below are various 19" front wheel fitments popular in the E46 M3 aftermarket world. I've added the outer position and inner clearance change against the original CS/ZCP 19x8.0" front wheels. 

Diameter & Widths	Offsets	Tires	Negative Camber	Outer Position	Inner clearance
19x9.5	+27	245/35/19	-2.0	+39mm	+1mm
19x9.5	+22	245/35/19	-2.5	+44mm	+6mm
19x10	+25	255/35/19	-2.8	+47mm	-3mm

Dynamics to remember.

The further out the wheel sits, the more camber you need to dial in. The wider tires you want to run, the less inner clearance you have, and the more negative camber you'll need.

This matters most to owners with aftermarket coilovers. They most often tend to have less inner clearance due to helper springs and larger diameter damper bodies.

My custom KW Clubsport kit uses the V3 damper body with helper springs, and external reservoirs. 

The previous owner's fitment. 

The Phoenix was currently sitting on a set of Beyern Mesh from the previous owner. The front wheels were 19x8.5J ET40 front wheels wrapped in Alibaba 225/40/19 tires.

The fitment was OK on original suspension, tire sizes and ride height. They extended an extra 13mm over stock CS/ZCP specs.

Looking back to September 2021 has me feeling older than I should. 

The fitment became ultra meh with the widened fenders, lowered chassis on coilovers and a dab of negative camber over original specifications. The wider arch made the entire fitment shameful. 

I took out the super-not-really-precise magnetic camber gauge, tried finding the 0, and hit -2.0. Those are the standard road camber specifications of the custom KW Clubsport kit. 

My preliminary test fitment notes. 

I did not bother testing with the CS/ZCP front wheels as the napkin maths made it futile. I opted to test with the rear 19x9.5 wheel at the front. 

These notes remain preliminary as I test fitted the wheels without tires.

It's a common practice for wheel fitment tests as it is much less of a hassle to accurately position the wheel outer edges to the fender. 

But first, self-respecting wheel fitment bros will carry around their box of spacers and extended bolts in various sizes. Unashamedly, I'm part of those: I had a variety of 12mm and 20mm spacers handy.

Test #1: No spacers. 

My intention with this initial test was to ensure inner clearances with the original wheels, and larger diameter damper bodies and helper springs. The 19x9.5J ET27 have 1mm more inner clearance over the stock 19x8.0J ET47. 

The KW springs peek through, it felt close without even being fully compressed. It cleared under full compression, barely.

The good news was there was still lots of clearance to further push the wheel out. The MacPherson front struts will add negative camber as they compress, this wheel was only going to go further inwards. 

Test #2: 12.5mm spacers.

Up next, I sought to test what would essentially be the equivalent addition of a 12.5mm spacer that matches the widened fenders extra dimensions of 10mm. It would serve as visual reference to owners currently using a 19x9.5 square setup with original CS/ZCP wheels. 

The 12.5mm effectively created a 19x9.5J ET14.5. This would extend an extra 13mm and have 13mm more inner clearance over the stock 19x.5J ET27. This spacers' width is a BMW enthusiast favourite as they are sufficiently large to allow the machining of a hub bore lip to avoid vibrations and sheering of the lip. 

Knowing the inner clearance was fine, I compressed the suspension up to its minimum travel. This was already looking much better: the wheel's lip was nearly aligned with the fender's edge. 

Test #3: 20mm spacers.

The 3rd test's spacer effectively created a 19x9.5J ET7. This would extend an extra 20mmm and have 20mm more inner clearance over the stock 19x9.5J ET27. As an added comparison, this spec extends 12mm further out than a 19x10J ET25. 

The Alibaba-spec 20mm spacers suck, the machining of the hub bore is slightly off and they will fuse with most wheels in a matter of a few minutes on sitting under weight. Traumatized from my experiences with these spacers, I greased them first. The bolts are lengthy, and it's not something I would ever recommend on any M car. 

The outer edge of the wheel was now nearly perfectly aligned with the fender's arch at minimum travel. However, this test had me feeling ride height was set too low for this fitment when accounting for bump-stops compression.

Test #4: 30mm spacers.

With the limits set, I wanted to explore more aggressive fitments using a 30mm spacer. The 30mm spacer would effectively create the following equivalents. 

Widths	Offsets	Inner Clearance
19x9.5	-7	Reference
19x10	+3	16mm less
19x10.5	+6	26mm less
19x11	+12	38mm less

We finally removed the TSW wheels and swapped the Chinese tires over to the original CS/ZCP wheels. Unfortunately, the tire beads were damaged, and the tires wouldn't hold pressure. This wouldn't be a perfect test - it's data nonetheless. 

Test #4.1: Lowest ride height, most aggressive camber KW CS specs. 

The first set with the 30mm spacer was using the previous slammed ride height specs of the Custom KW Clubsport V3s, but pushing camber to their limits. The top plates are somewhat limited, giving a max camber of approximately -3.0, even when pushing the top plates inwards with the slotted strut tower. 

The top plate position below shows what would be considered a stock-like camber spec.  I had to unbolt the top plates and raise the car to loosen the 4x top plate bolts. 

Once lowered, we laughed - yea that wasn't going to work. The thicker side wall is a risk as it deforms in turns, increasing rubbing risks. It wasn't hitting the fender on any steering angle, but this is a bump away from cracking a fender. It simply was too low. 

Test #4.2: +5mm ride height

The second test with the 30mm spacer had me increase height. This was the only variable I could test for: I was already max'ed out on camber, and I couldn't yet fit the 265/30 tire with a smaller overall diameter to gain clearance.

The KW Clubsport's helper spring setup makes it incredibly easy to adjust. No tools needed, I turned the collar by had.  

There was still a significant amount of poke, and this tire is simply too thick. 

My recommendations.

I have put together the preliminary recommendations on wheel and tire fitments to pair with the widened carbon fenders. This is based on my tests described above and previous experiences fiddling with wheel and tire fitments across various chassis. 

It's deemed preliminary as I do not include final ride height, and the 11" fitment remains to be tested. 

The recommendations are aimed for street oriented 19" wheel setups. I will revisit this with 18s. As a rule of thumb, you can usually add +05 to the tire sidewall - the 19x11 tire is ridiculous and purely put up for good measure. 

Diameter & Widths	Offsets	Tires	Est Negative Camber
19x9.5	+7	255/35/19	-2.0 or less
19x10	+25	265/30/19	-2.0
19x10	+15	265/30/19	-2.5
19x10.5	+15	275/30/19	-3.0
19x11	TBD	295/25/19	-3.0 & more

 

The prototype 163M CSL style forged wheels will finally land. We will be able to re-explore our fitment tables. 

Up next: we revisit the V1's design flaws, and develop the V2s.