E420 questions

I am going to buy new wheels for my '94 E420. What are the pros and cons of moving to a 16" wheel from the standard 15"? If I find a good deal on EBay (for instance) what specifications should I look at to
make sure that the wheel fits? The current wheels are 6-1/2J X 15 H 2 (according to the manual) - what do these codes mean?
Also, I have disconnected the factory alarm system because of false alarms. Does anyone know if there is a common cause for this? I'll have the dealer look at it in the future to try to find the problem, but I'm wondering if anyone out there has run across this problem and might be able to suggest a common problem so that I might avoid hours of shop time.
And also, when you lock the car from the outside, you have to unlock it from the outside or the car won't start. I'm having a problem that occaisionally the car won't start when it is unlocked using the key and I have to relock the car from the outside, wait a minute, unlock it again and try to start it. The car never starts when I unlock it from the trunk. Again, any ideas on where to start looking for the culprit?
Other than these things, the car is very enjoyable. I have driven it round trip from the west coast to the midwest three times and each time was extremely enjoyable. Cruising across the desert at 90 mph (or so) in this car, listening to Miles Davis is one of the greatest experiences you could have. I drove it at over 100 for a small stretch and the car seemed to say, "OK. Is this all you want? Yawn..."
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The 16's and 17's look better! Go to tirerack.com where you can shop for wheels and see how they look on your year/model/color Mercedes. They also will list the proper size tire should you go with on a larger rim.
The numbers you mention are 6-1/2" wide and 15" in diameter. You can go an inch or so wider in the rim usually. The key thing to match is the number of lugs and spacing (yours should be 5-lugs by 112mm or 5x112). And the offset - yours is probably 35mm or 41mm, just look on inside of the rim and there will be a number like ET35 or ET41.
On eBay sometimes it also gives you more choices if you know other MB models that have the same offset as yours because people do not always list the offset. (e.g. the older W124s have the same numbers as the new CLKs).
Scott D

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I'm about to purchase new wheels for my 87 300D (same chassis as your E420). I settled on getting 16x7.5 Reproduction 8-hole wheels which are of the same design as what you have now. Tirerack has them for about $120 each. With 7.5" wide wheels, I am going to have to fold the fender lip on the front of the car in to clear everything.
If you get a larger size wheel, they will look better, but ride quality will deminish as you have to get lower profile tires to keep the same total wheel diameter (and therefore not mess with the speedometer). Wider wheels allow you to get more rubber on the ground, but they increase rolling friction a bit and may decrease fuel mileage.
16x7 seems to be the optimum size for the 124... looks good, wide enough. Only thing you have to do is find a wheel that you like that is in the proper size for your car. However, I'd reccomend you figure out what your priorities are before you get new wheels -- if you want looks or increased handling, go with 16's. If you just want more rubber on the road, I reccomend 15x7 "Sportline" 8-hole wheels, which you can get in reproduction form from Tire Rack... more rubber on the road, and if you get 205/60/15 tires (sportline OEM), you'll see a difference in handling... but if you get 205/65/15s the car won't look odd at all, it will be totally normal looking but with more rubber on the ground.
Not sure about the alarm stuff... the non start sounds like an ignition disabling thing in the alarm box going haywire.
-Mike

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As you go to a wider rim you needless offset (to move the edge of the rim further away from the hub/brake suspension.
So on most W124 cars like yours: If your orginal wheel is 6.5x15 ET49, a 7" wide wheel would need an offset of about ET44, and a 7.5" wide wheel would require and offset of about ET35.
Scott D

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