adhawkins Posted January 13, 2006 Share Posted January 13, 2006 And please tell me you measured the wheel and not the tyre when you measured the offset... I measured the tyre, but then I measured the distance from the edge of the tyre to the mounting face. Isn't that the same thing? Andy Quote Link to comment Share on other sites More sharing options...
Blatman Posted January 13, 2006 Share Posted January 13, 2006 And please tell me you measured the wheel and not the tyre when you measured the offset... I measured the tyre, but then I measured the distance from the edge of the tyre to the mounting face. Isn't that the same thing? Andy If you measured the tyre to hub face, then measured the tyre to the rim and subtracted the difference in tyre to rim measurement from the overall measurement, then you probably got it right. My concern comes from the fact that you keep saying the wheels are stamped ET5 but that you are *sure* they are actually ET30. It is quite possible that the "extra" 25mm (12.5mm each side) could be the tyre overhang and that you do indeed have ET5 wheels. You need to be *sure*... Quote Link to comment Share on other sites More sharing options...
adhawkins Posted January 13, 2006 Share Posted January 13, 2006 I don't think I've ever said I'm sure about anything I didn't measure the tyre to rim. Someone posted a link to a web page that said the offset could be calculate by putting the wheel flat on the floor, and measuring the distance between the floor and the mounting face. Then flip the wheel over, and re-measure. The offset was (I think) the difference between the two measurements, divided by two. Would that work with a tyre on the wheel? Andy Quote Link to comment Share on other sites More sharing options...
Phil. S Posted January 13, 2006 Share Posted January 13, 2006 Would that work with a tyre on the wheel? Surely it would. Suppose without the tyre the two measurements were 170 and 150. Difference of 20 divided by 2 = offset of 10. Suppose the tyre adds 10mm either side to the width of the wheel. The two measurements would then be 180 and 160. Difference of 20 divided by 2 = 10. I think that's right, though I am never certain of my maths, and never feel confident with offsets. Quote Link to comment Share on other sites More sharing options...
Blatman Posted January 13, 2006 Share Posted January 13, 2006 Someone posted a link to a web page that said the offset could be calculate by putting the wheel flat on the floor, But you had the tyre on the floor, not the rim, I assume You can calculate it but as I have said, and as Phil has laid out, you have to subtract the extra width the tyre adds, unless the wheel rim was actually touching the floor even with the tyre on when you took the measurements. I've never had a 185 tyre n a 6" rim that isn't actually wider than the trim when laid on the floor, a 205 would certainly protrude by quite a lot. Either way, any offset measurement that isn't recalculated to remove the extra width of the tyre isn't worth a carrot... Quote Link to comment Share on other sites More sharing options...
adhawkins Posted January 13, 2006 Share Posted January 13, 2006 But surely the tyre sticks out the same amount on each side of the rim? So the offset calculation is gonna be the same (I think that's what Phil was trying to say). Or isn't it? Andy (confused). Quote Link to comment Share on other sites More sharing options...
Blatman Posted January 13, 2006 Share Posted January 13, 2006 But offset is calculated from the rim, not the tyre. So, wheel with tyre lays flat on the floor. Does the rim of the wheel touch the floor? If yes, you have no problem. If not, you need to measure how far off the floor the rim is, and subtract 2x that measurement from the overall width *before* you calculate the offset. The hub face of the wheel is further away from the floor by the amount that the tyre overhangs the rim. Remove the tyre and the hub face is immediately closer to the floor, so the offset measurement is different. So you must subtract the tyre to rim measurement before calculating offset... And your confusing me now... Quote Link to comment Share on other sites More sharing options...
adhawkins Posted January 13, 2006 Share Posted January 13, 2006 But when you turn the wheel / tyre over, the rim is off the floor by the same amount... Consider a 10" rim width, with a tyre that sticks out 1" from each side of the rim. Put the rim on the floor, and the mounting plate is 3" from the ground. Turn it over, the mounting plate is 7" from the ground. So the offset is 4" / 2 = 2 inches. Now if you take the tyre into account. In the first direction, the mounting face will be 4" off the ground. In the second case, the mounting ace will be 8" off the ground. So the offset is 4" / 2 = 2 inches. The same result. Correct? Andy Quote Link to comment Share on other sites More sharing options...
Blatman Posted January 13, 2006 Share Posted January 13, 2006 As long as the edge of the tyre is perfect, probably, and I see the light... That's the trouble with doing things properly, when someone does it the wrong way and asks if it's the same, it does yer head in... Quote Link to comment Share on other sites More sharing options...
adhawkins Posted January 13, 2006 Share Posted January 13, 2006 The perfection of the tyre shouldn't be too much of an issue though, because the odd millimetre out isn't going to cause too much of an issue I'd hope. At least it'll tell me if they are closer to ET5 or closer to ET30. Now just have to get off my and measure them... Andy Quote Link to comment Share on other sites More sharing options...
welsh wizard Posted January 13, 2006 Share Posted January 13, 2006 Now just have to get off my and measure them... Well that's not likely to happen this year, is it darling Luned Quote Link to comment Share on other sites More sharing options...
Blatman Posted January 13, 2006 Share Posted January 13, 2006 Oof. That's gotta hurt Quote Link to comment Share on other sites More sharing options...
adhawkins Posted January 13, 2006 Share Posted January 13, 2006 Nah, I'm immune to it now Andy Quote Link to comment Share on other sites More sharing options...
jago Posted January 15, 2006 Author Share Posted January 15, 2006 ok blatman its a pre lit se westy fitted with 13/ 5.5 cosmic alloys . and i fancy minilites or somthing simular Quote Link to comment Share on other sites More sharing options...
Blatman Posted January 15, 2006 Share Posted January 15, 2006 I'd be looking at 13x6 or 13x7 K&N Minators. Offset of ET24. Quote Link to comment Share on other sites More sharing options...
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