need help interpreting numbers on rims
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Velocewest
- Posts: 1558
- Joined: Feb 12, 2006 12:00 PM
- Location: UK
[QUOTE="dotrp"]What does '73x16 H2 IS20 31/04' mean? Clearly they are 16" wheels. Is '73' the hub hole size, meaning it should fit an e28's 72.5mm hub? Does 'IS20' mean 20mm offset?[/QUOTE]
Look closer. I'll bet you it says '7Jx16' , meaning it's 7 inches bead to bead inside of the rim, and 16 inch mounting diameter, with a 'J' shaped bead flange (common). The 'IS20' is the offset, so 20mm. The 31/04 might be day and year of manufacture.
The dimensional measurements of wheels are relative to where the tire mounts, not the overall dimension including the bead flange.
[Edit by Velocewest on [TIME]1109354747[/TIME]]
Look closer. I'll bet you it says '7Jx16' , meaning it's 7 inches bead to bead inside of the rim, and 16 inch mounting diameter, with a 'J' shaped bead flange (common). The 'IS20' is the offset, so 20mm. The 31/04 might be day and year of manufacture.
The dimensional measurements of wheels are relative to where the tire mounts, not the overall dimension including the bead flange.
[Edit by Velocewest on [TIME]1109354747[/TIME]]
Thanks. I'm sure you're right about that. I didn't read them myself, got them from the person I'm thinking of buying them from.Look closer. I'll bet you it says '7Jx16'
Not sure what you mean by that. A related question though: do spacers increase or decrease the offset? In other words, does positive offset mean the wheel moves out or in?The dimensional measurements of wheels are relative to where the tire mounts, not the overall dimension including the bead flange.
This may be useful info for somebody. The wheels in question were totally confusing me. Couldn't get them to fit on my e28. Turns out the current owner made an attempt to mount them on a e39 and ended up beating the crap out of the hub bore ... so now it won't fit anything. Think I may try to buy them cheap and try to fix it/them.
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Velocewest
- Posts: 1558
- Joined: Feb 12, 2006 12:00 PM
- Location: UK
What I was trying to say about dimensions through the haze of this fricken' cold is -- the measurements cast on the rim are not the overall dimensions, they represent the tire mounting dimensions. If you measure a 7x16" rim, the distance from outer lip to outer lip will be like 8 inches wide and 16.75 inches diameter. I'm not sure why I felt the need to explain that, possibly it is a result of the hallucinations brought on by Sudafed abuse.
BMW wheels have positive offset -- that is to say, the mounting surface is offset towards the outside of the rim from the centerline. So spacers will move the mounting surface back toward the centerline, reducing the positive offset.
Check out Tirerack.com's tech section, they have a very good article on offset with nice diagrams and such.
BMW wheels have positive offset -- that is to say, the mounting surface is offset towards the outside of the rim from the centerline. So spacers will move the mounting surface back toward the centerline, reducing the positive offset.
Check out Tirerack.com's tech section, they have a very good article on offset with nice diagrams and such.