My bixenons are plenty bright but it seems like they don't point up quite enough to light up the road very far ahead of me. I feel like I'm overdriving my headlights. I don't recall being bothered by this before. It could be that I'm getting more picky but I'm also wondering if the taller (265) tires I put on the back recently might be tilting the nose down enough to do this. Any expert opinions?

 

did you recently upgrade you wheels from 17s to 18s or 19s? and why are you running 265 (just curious)?
i'm sure it would effect your headlights a little. but nothing that much. running a 265 tires just means your tires are WIDER not taller... if you're running like a 265/50/18 (not sure if thats a real size or not) your side wall would be taller than the OEM size of 245/40/17 (for the C32) or a 255/35/18 (for the C55).

the middle number in 265/50/18 is the side wall height or the aspect ratio.

 

One slight correction, It is ONLY the aspect ratio, NOT sidewall height. Keep in mind that not all 265/50/18 will be the same overall diameter my friend. They DO change from manufacturer to manufacturer. Consult Tirerack.com for your individual tire diameter.

Okay, back on track, a slight cahnge, say 1" in overall diameter WILL have a dramatic effect on your headlights, IE they will point into the ground. Again, check to see what your difference is between the two tires, OEM, to your new one. And yes, headlights are adjustable up and down. Note: On my toy with the Bi-Xeon, I noticed no difference from a 245 to my new 255's. Granted, it was only a .2" difference in overall height.

See yeah

 

this is direct from tire rack's Tech Section

"Sidewall Aspect Ratio

Typically following the three digits identifying the tire's Section Width in millimeters is a two-digit number that identifies the tire's profile or aspect ratio.

P225/50R16 91S

The 50 indicates that this tire size's sidewall height (from rim to tread) is 50% of its section width. The measurement is the tire's section height, and also referred to as the tire's series, profile or aspect ratio. The higher the number, the taller the sidewall; the lower the number, the lower the sidewall. We know that this tire size's section width is 225mm and that its section height is 50% of 225mm. By converting the 225mm to inches (225 / 25.4 = 8.86") and multiplying it by 50% (.50) we confirm that this tire size results in a tire section height of 4.43". If this tire were a P225/70R16 size, our calculation would confirm that the size would result in a section height of 6.20", approximately a 1.8-inch taller sidewall."
http://www.tirerack.com/tires/tirete....jsp?techid=46

 

Please take a look at three different 255/40/17's. You will see that they ALL have different OD's. I am not trying to start an argument. I can assure you that this tip/trick is what people do to fine tune the rear end gear, and help on other issues. This is why I stated it is just that an aspect ratio. NOT a diffenitive height. Otherwise ALL tires regaurdless of brand, of the same size, would be the same OD.

See yeah my friend

PS: I did it for you, note three identical tires, ie spec, three different diameters

255/40ZR17 BFG
Load Index 94 = 1477lbs (670kg) per tire
Speed Rating “Y” = 186mph (300kph) 94Y SL Left Treadwear: 200
Traction: AA
Temperature: A200 AA A
1477 lbs.
44 psi
9/32"
27 lbs. 8.5-10"
9"
10.2"
NA
25" OD
831

255/40ZR17 [B]Bridgestone[/B
]Load Index 94 = 1477lbs (670kg) per tire
Speed Rating “W” = 168mph (270kph) 94W SL Runflat - OE vehicle use only Treadwear: 140
Traction: A
Temperature: A140 A A
1477 lbs.
51 psi
11/32"
30 lbs. 8.5-10"
9"
10.1"
8.8"
25.2" OD
827

255/40ZR17 Michelin
SL N2 (Porsche) Treadwear: 220
Traction: AA
Temperature: A220 AA A
1477 lbs.
51 psi
10/32"
24 lbs. 8.5-10"
9"
10.2"
NA
25.1" OD
827

 

I'm pretty sure there is some setting in the COMAND system to factor in what tires you have on the car. Not sure if this affects the autoleveling xenons, but it might.

 

Just curious, do the 265's feel a bit wobbly? Seems like a lot of rubber for the 18s.

 

If you have a C32 (or, presumably, C55) with OEM bi-xenons that came stock on the vehicle, you should have self-leveling headlights. Consequently, you wouldn't notice a difference, even if you changed your tire's OD in the rear (or front, for that matter)

 

not sure if it's related but i had my rear tires replaced a couple of weeks ago at the dealer, with OEM size, and the front headlights were pointed way low to the ground.

brought it back to fix but still not 100% sure they are at the level as before

 

My C55 had the same problem, low beams appeared to be adjusted very low. The fix was "test and replace Xenon level sensor" 81071CPMBU $210.00; and parts as follows: 010-542-77-17 sender unit $142.21 (less 15% for MBCA membership); 209-320-02-89 rod $32.30 (less 15%); freight 15.00 (less 15%). After the fix the lights worked like new, although only one side needed the repair.

 

The headlamp self-leveling sensors enable the headlamps to react and adjust to changes in the suspension’s position based solely on their fore and aft sprung loads. However, they’re not quite sophisticated enough to accommodate for differences in tire height.

zcct04, if your sensors and servos are otherwise functioning properly, the headlamps’ themselves facilitate a (limited) range of vertical and horizontal manual adjustments for this exact reason. Upon each startup, mine will cycle through from low to high before settling in on their programmed and adjusted aim.

Since yours is still covered by warranty, dsC32’s solution is probably the best bet.