"In this Special Series about the OE+ widened carbon fenders, I document the logistics, unboxing impressions, multiple test fitments and final impressions.
In this entry, I explore new wheel fitment possibilities opened up by the wider fenders in preparation for the 163M CSL style forged wheel program. I include fitment tables and in-depth specs. "
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. I know this is the missing piece of information for many E46 owners to pull the trigger.
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.
As a disclaimer, my fitment goals are personally oriented for road & track - meaning 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 imply 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
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. I intend to run Michelin PS4S, a tire brand and model with sidewalls that naturally stretch a little more.
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.
Unfortunately my set of H&R 30mms were still fitted to the V10's BBS CHRs.
I filmed and edited a reel of the test fit process here.
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 - vibrations be damned.
Knowing the inner clearance was fine, I compressed the suspension up to its minimum travel.
This was already looking much better. Slowly, but surely, we were moving in the right direction.
The wheel's lip was nearly aligned with the fender's edge.
I wasn't looking to test ride height yet - however I could imagine how a 265/30/19 tire with a stretch friendly sidewall measuring roughly 3.1" / 80mm would look.
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 H&R 30mm spacers are first bolted into the hub, and use the OE bolts to connect the wheel to the spacer.
Alright - we got something here. Let's move back a little.
Not bad, not bad at all.
This had me feeling ride height was set a tad too low for this fitment when accounting for bump-stops compression which I cannot test with this method.
That looks great.
The outer edge of the wheel was now nearly perfectly aligned with the fender's arch at minimum travel.
Welcome to the Danger Zone.
A truly aggressive street fitment will have the wheel's outer point outside of the fender at the full compression, with the tire's sidewall stretched to tuck inside the fender at full compression.
I deem this the danger zone for a reason or two - which aren't obvious at first.
Unrolled, uncut fenders.
These fenders were molded and enlarged from a Genuine BMW unit. They are not rolled - and, you cannot roll a carbon fender.
The white edge where the outer edge of the wheel and tire would sit indicates the extra material. You will need to cut it if you intend to run uber-aggressive fitments. I don't.
You're now officially in a game of millimetres.
But how is this mathematically possible?
The fenders may only be widened by 10mm, but by positioning the wheel further out, you gain slightly more track width potential.
The reasoning is you can also dial less camber for the equivalent track with the original fenders. You can also dial in more camber to tuck under the fenders due to the increased inner clearances.
However, a more aggressive offset in combination with more negative camber will have the downside of having the lower section of your front wheels stick out massively from the standard width front bumper and doors.
Do you like re-doing your PPF yearly? Does your body shop hold blackmail material over your head? Extreme fitments have compromises.
Still, this rationale only applies for street cars. If you are a Clubsport / Track only E46 M3 owner, feel confident that you have more room to play with then I personally intend to.
Owners have that previously played with E46 M3 front fitments know what this means - there's a lot of room still.
Test #4: 30mm spacers.
With the street limits set, I wanted to explore more aggressive fitments using a 30mm spacer. The 30mm spacer would effectively create the following equivalents.
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.
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.
For performance, the front right height of the E46 M3 needs to be slightly higher than the rear as well. This fitment work needs to remain functional.
+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.
It's visibly an improvement.
There was still a significant amount of poke, and this tire is simply too thick
With some fiddling to ride height, and more camber, this could work - but it just wouldn't do it for what I want.
Disregard the panel fitment as they were all loose to avoid damaging any of them during the fitment process. You can see how far out the tire sticks.
My recommendations: geometry!
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.
Diameter & Widths
Est Negative Camber
|19x9.5||+7||255/35/19||-2.0 or less|
|19x11||TBD||295/25/19||-3.0 & more|
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.
Before the end of '23, the prototype 163M CSL style forged wheels will finally land.
Up next: we do the final fitment of the fenders during re-assembly, and we revisit the wheel fitment with tires mounted.
Until then, you can spec your set of widened fenders year long here.