Wheel Specifications

The 7J refers to the rim width in inches, the 16 is the wheel diameter in Inches I forget what the rest is but part of it is to do with the offset of the wheels rolling centreline (line 3.5 inches across) and the bolt pattern/centre type. You will find similar numbers on the tyres normally 60H16/225 which gets confusing as it is 16 Inches diameter Rim fitting a sixties series aspect ratio (rolling width to height ratio) with a speed rating of H which is one under V which is bloody fast. The 225 is teh tread width in Millimetres...Just to make sure you learned both systems as a little tacker!

common misconception, although less relavent today with low profile tyres being more common - the 225 is not the tread width but the overall width of the (properly inflated) tyre. in other words, this includes the "bulge" in the sidewall.

7J is the width of the wheel, 16H is the wheel diameter and ET 31 should be the 31mm offset/backspacing. The backspacing is where the center of the wheel (hub mounting portion) is, in relation to the center of the rim (tire mounting portion). This backspacing or offset can be positive or negative. when you see cars with that stupid bowlegged look on them where the wheels stick out from the car, that is a positive offset. Because as you move the mounting center of the wheel further back from the center of the rim, it will cause the rest of the wheel to come out away from the car. with a mercedes you probably have a negative 31mm offset, this keeps the wheel just slightly under the edge of the wheel well so that when the tires are installed and the weight of the vehicle is put on the wheel the bulge of the tires do not stick out from the side of the car. because honestly, you don't want that stupid bowlegged compact car look, you want the smooth slick mercedes look!

#1 Ah! you were working on it too! Yes, the wheels roling centerline is what I mean by the center of the rim on reply #2

7J x 16H2 ET31

7 = Rim width in inches

J = Shape of the tyre bead profile of rim

16 = Diameter of rim in inches

ET =offset from the centre line of the wheel to the bolt face (from 'Einpresstiefe' – insertion depth)

31 = 31mm positive offset – note, this means 31mm inset

H2 = double hump design rim – just means the profile of the wheel rim to prevent the tyre sliding off!

Thank you a lot!

ET does not call home in this particular example, it is exactly what someone else mentioned and in German is written as "Einpress Tiefe". A good source with diagrams with an English explanation can be found at:-

http://www.hrps.demon.nl/jwbus/T2-tires.htm - sorry, link no longer available

The reason for this ET though is not to do with the look of the wheels, it is to fix the center of load at a point between the inner and outer wheel bearings, so that they are equally loaded and do not fail early.

Some "Boy-Racers" add spacers to make the wheelbase wider, but forget that they also load up the outer wheel bearing much higher and could cause an early life failure of that bearing.

Spacers are not a good way to do this, better is a wider tyre, with a wider wheel, where the load from the wheel passes exactly through the same designed point between the inner and outer bearings.....so as to not overload either bearing more than what was designed, or better said, to keep the differences to a minimum.

Thanks for the correction, your English is hugely better then my German.

Many thanks for the compliment, I am not native though, I have lived here since 1981 (one should be able to speak the language, etc, after such a time!!), its been a lot of fun, I would not have missed it for anything.....

I learned French at school and until I left the RN I was fluent, its got very rusty now. I also leaned to read Portuguese when stationed on tha Azores for a time (no English books or newspapers then) and started learning German here at 35, not a good age to learn a language really, younger is much better.....

Nowadays my English is getting rusty especially with regards to the spelling of words I haven't used in years......but Dictionaries are a great help, especially online ones!!