Quick-links: ET Explained Factory Wheels Other Rim & Tire sizes Spacers Tires Tire Pressure
Tire Pressure Monitor
Wheels are normally a hot subject for M3 owners. The choice of wheels adds significantly to the cars appearance and has substantial influence on the handling. Quite a lot of M3 owners give priority to looks over practicality and actual handling. This goes for the stance as well. It’s not my personal choice. 20” rims and a very low stance may look “fantastic” (to some) but it will not improve the way the car drives. There are discussions about the optimal rim size, but it seems a tie between 18” and 19”. About the width of rims one also has to compromise between looks and handling. Offset (ET= (German) Einpresstiefe) is another issue. Having the wheels as far out as possible is not necessarily an advantage. Basically the center of the wheel should not differ from the OE position – which means that you should stick to the ET values the car had from factory. Deviations from this will have a negative effect on steering and braking balance on the front and bearing wear on both – however you may gain a little corner speed with wheel centers moved outwards (lower ET).
Factory wheels:
From factory the E46 M3 came with the following wheel combinations: Link
As you can see from the above link, the E46 M3 came with the following rim combinations:
F: 8”x18” ET 47 ; R: 9”x18” ET 26 (Style 67, M Double Spoke) (Base model)
F: 8”x19” ET 47 ; R: 9,5”x19” ET 27 (Style 67, M Double Spoke) (Optional)
F: 8”x19” ET 47 ; R: 9,5”x19” ET 27 (Style 163M, M Cross Spoke) (ZCP & CS Package)
F: 8,5”x19” ET 44 ; R: 9,5”x19” ET 27 (Style 163M, M Cross Spoke) (CSL)
Wheel paint color
unfortunately, rims may be scratched. Should you be so unfortunate
that your CLS style 163M rims need restoration the color is
DEKORSILBER METALLIC Ref. A55, code WA55.
It probably takes some effort to find a supplier.
To my knowledge it’s not possible to match the original color by powder
coating. For wet paint Glasurit , the premium refinish paint brand of BASF,
has specified the formula to the right.
Other rim and tire sizes:
If you want to fit other rim and/or tire sizes on your E46 M3 E46 M3 Apex Race Parts has a fine Wheel & Tire Fitment Guide. It’s a real good guide that covers many aspects – and spans from square to staggered ; from bolt-on OEM+ to aggressive. Follow the link.
According to Apex Race Parts the most aggressive that do not require modifications on the car is:
Front: 19x9” ET28 (ARC-8) or ET30 (EC-7 & SM-10) with 245/35-19 tires
Rear: 19x10” ET25 with 275/30-19 tires
This combination moves the edge of the front rim 20 mm more outwards than the CSL combination.
I believe this is the absolute max on an unmodified car.
At the rear I positively know that the combination does not touch anything.
Please be aware that some aftermarket suspensions are wider than stock and may not allow the 9” / 10” versions.
The two drawings to the right show some combinations of rim width and ET.
On drawing 1 it’s shown that the distance from wheel hub to outer edge
of rim (119 mm) is max. at rear without modifications to the wheel arc.
This goes with 19”x255/35 tires.
On drawing 2 the distance 100 mm (front) is for 19”x10” ET25 as Apex states as max for fitment
without modifications. Tires according to Apex are 275/30-19”.
Personally I should think this is right at the edge, however it may not
be possible to fit 10” with higher ET due to clearance to spring etc.
The distances from wheel hub to outer edge of rim may be calculated as:
Rim width [inch] x 25,4 / 2 – ET + Lip Thickness [mm]
OR if you use spacers:
Rim width [inch] x 25,4 / 2 – ET + Spacer + Lip Thickness [mm]
When you look for new rims, be aware that some rims have considerably
stepped barrels. Often this not an issue, however if you have “big brakes”
(large diameter brake discs) there may be a problem. See photo to the right.
Here is a link to all Original BMW rims
Spacers
In principle spacers are corrections to ET. If you use a 12 mm spacer it is the same as reducing the rim ET
by 12 mm – however the use of spacers is never as good (steady/robust) as having the offset in the rim itself.
There are two “weaknesses” with the use of spacers. The wheel bolts have to be longer and the centering of the wheel may be compromised.
It’s evident that the wheel bolts shall be longer. Use wheel bolts that are as many mm longer as the standard bolts as the spacer is thick. This ensures that the thread grip is the same.
Some (especially thicker) spacers have threads in them for the wheel bolts and are fixed to the wheel hub by a separate set of bolts. This may be OK, but since most spacers are made of aluminum be sure that the wheel bolts are threaded into steel inserts that are anchored well in the aluminum. (See the center picture above)
Another issue is centering of the wheel/rim. Normally the rim is centered on the hub by the Ø 72,6 mm bore/flange. The wheel bolts alone do not center sufficiently - see left picture above - not recommended.
Especially if you use not original dust caps you should watch out for the thickness of the dust cap edge. If it’s too thick the spacer will not flush properly with the brake disc. See photos.
It’s my experience, that spacers thinner than 12 mm do not provide the Ø72,6 mm flange that centers the rim/spacer. See right drawing above.The reason for this is that the thickness “A” at the drawing is not present when the spacer is less than 12 mm. In some cases the material “A” is present on 10 mm spacers, but the bore fitting on the hub (shown as 10 mm) is not deep enough to allow the spacer to be pressed correctly onto the hub. If the spacer is not pressed completely against the hub, the wheel will wobble.
If your rim has a modest chamfer and the edges are not rounded/
damaged, then a 5 mm spacer may fit and provide sufficient hub-
centering surface (see illustration to the right).
When using spacers be sure that the bolts are of correct grade (10.9) and not some cheap soft Chinese iron.
For M3s with CSL/CS wheels spacers 15 mm front and 12 mm rear seems to be the max w/o other changes.
Tires:
Given the rim size, there is the question of tire size and profile. Generally it is not recommended to deviate from the tire manufactures recommendations as to which tires are suitable for which rim sizes. An example is that for tire 265/30 R19 the nominal rim width is 9,5” with min. 9” and max 10”.
Personally I would stick to the OE BMW combinations – see link.
As to tire load index the recommended is 93Y XL in the front and 96Y XL in the back.
Michelin Pilot Sport 4S is probably the most popular tire for E46 M3 (not track use). Be aware, that this tire comes with SelfSeal feature (reduces (risk of) puncture) only in the size 235/35. There is however no technical/safety or legal constraint to use tires with SelfSeal on one axle only.
It is a bit basic, but here are some fundamental things about tires that are worth knowing: Link
Tire pressure:
Within limits tire pressure is a matter of personal preference. By experimenting with different front and rear pressures you can modify the cars balance when cornering. As a rule of thumb you should not deviate too much from the values recommended by BMW. Be aware that both too much pressure and too little pressure increase wear on the center of the tire. Too much pressure is obvious, however too little pressure reduces the overall tire “stiffness” and allow the tire center to be slung out at high speeds giving more wear.
The BMW recommended tire pressures are:
(240 kilopascal = 2,4 Bar)
Tire Pressure Monitor:
The E46 M3 has a Tire Pressure Monitor System (normally). In reality this name is a little misleading since the system does not actually monitor the tire
pressures, but monitors a derived property,
the wheels rotation. The system works with
the ABS impulses from each wheel – plus
information from the steering wheel angle
sensor. (see also this). The steering angle
sensor tells the system which relations to
expect between left and right wheel rotational
speeds. If you are steering straight ahead
left and right rotation speed should be the
same. If you turn the outer wheels shall
rotate faster. If the detected differences
exceed some preset limit the warning goes.
Differences may be minor (yellow light) or
serious (red light).
Note: The system is NOT a TPM (Tire Pressure Monitoring) System where the actual tire pressure in each wheel is transmitted wirelessly to the central system.
Initializing the system (activate / deactivate):
In order to work properly the system needs to be initialized or reset. The owner’s manual explains it.
Resetting the system:
If you have a puncture or the Tire Pressure Monitoring System for some other reason gives an alert (Yellow or Red) you firstly need to correct the cause of the alert. Change tire, inflate tire or whatever is needed. Please observe that the system interacts with the steering angle detector, so the cause may come from misalignment – or a defect steering angle detector. When the cause is attended to you will find the procedure explained in these DIY videos (link 1 , link 2 and link 3).
