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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Wheels and Tires Forum Sponsored by The Tire Rack > 2 piece Split Rims Bought - OFFSET help



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      01-19-2013, 04:28 PM   #1
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Question 2 piece Split Rims Bought - OFFSET help

Guys & Gals,

I've got set of 19" 2 piece wheels which I'm keeping secretive until I mount them on Timeless and boy will they look good when on

I need help however............ I bought them online via ebay and the seller was unsure of the ETs and what not so I took a leap of faith, bought them, got them refurbed and now since I'm looking to buy tires, I realised why all this info is so crucial.... yes it's my 1st time buying wheels so I know NOW, what I need to look for next time.

Anyways, since the wheels got refurbed, I can't quite make out the stamped info inside the wheel but from whatever little I can see, I THINK it reads the following:

Fronts:
- 8.5j x 19"
- ET 40

Rears:

- 10j x 19"
- ET 40

Now.. From the measurements I have taken (following a step by step guide to work out the offset).. my findings are as follows:

Fronts:
- Overall Width = 240mm
- Centre Line = 120mm
- Backspace = 160mm
- Offset = Backspace - Centre Line = ET40

Rears:
- Overall Width = 280mm
- Centre Line = 140mm
- Backspace = 165mm
- Offset = Backspace - Centre Line = ET25

Question is... what do I go by? What I THINK I read on the reverse of the wheel (and it does look that rear ET = 40) OR what I have worked out using the traditional method?

Also, it may be handy to know I've got an E92 335D Pre LCI dropped on BC BR Coilovers. I can of course raise the car to avoid the rims catching the coilover etc.

Would I absolutely need spacers? I want a semi-aggressive kinda' stance so I'm going for a slight stretch of tyres.

Currently on OEM 230s (19") and fronts are 225/35/19 and rears are 255/30/19

I was thinking of 215/35/19 for Fronts.... and 255/30/19 rears? How will these go down with the spec give?

Lastly, is there ANY other way to find out what 'J' the rims are??

Many thanks in advance,
Sam
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      01-19-2013, 10:32 PM   #2
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Bump
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      01-20-2013, 01:19 AM   #3
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if it is et 40 all around put a 20mm spacer on front and rear with a tiny tiny fender roll and youd be fine it not just get 15mm all around with no roll with a 235/35/19 in front and 265/30/19 in the rear
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      01-21-2013, 08:46 AM   #4
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^^ Thanks.

What if they are ET 40 Front (19" x 8.5j) and ET 25 Rear (19" x 10j)??
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      01-21-2013, 03:21 PM   #5
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So you bought BC Forged by the sounds of the way you are using the J
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      01-21-2013, 04:52 PM   #6
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No, I bought rials buddy, rials daytona.
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      01-21-2013, 06:32 PM   #7
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20mm spacer up front imo
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      01-21-2013, 08:21 PM   #8
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Quote:
Originally Posted by AWBimmer View Post
What if they are ET 40 Front (19" x 8.5j) and ET 25 Rear (19" x 10j)??
ET 40 with an 8.5 will be moving closer to the inner strut but have the same clearance to the fender as the OEM 19's.. The oem 19x8's are ET 37 and they look sunken. I think if you are going to run an ET of 25 in the rear and ET 40 up front will probably look a bit off cause the backs are going to sit somewhat flush and the fronts will defintely be sunken. I agree with the rest of the guys a 20mm all the way around will give it a purty stance!
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      01-22-2013, 05:46 PM   #9
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ok from your formula, I would say if your fronts are 8.5(+40) and your rears are 10(+25), just add a 20mm spacer to the front and you'll be good. The 19x10(+25) is going to have your RIM sitting flush with the fender. And with the +20mm spacer for the front it'll put your front RIM 1mm behind the fender. B/c you are going to have a small stretch on both tires you could add a +10mm spacer to the rear and that'll put the back RIM 10mm past the fender. So then it'll look funny and you would have to do either a +25mm or +30mm to the front to make the poke of all the rims look about the same.
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      01-23-2013, 04:17 PM   #10
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I'd go with what is printed on the rims. Takign into consideration the rims are all originall faces/hoops
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      01-23-2013, 04:23 PM   #11
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just mount the wheels on the car and see how it looks. if it's +40, you WILL KNOW just by looking at it... it'll look sunken in. if it's +25, you WILL KNOW again just by looking at it... it'll look flush.
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      01-24-2013, 04:10 AM   #12
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Thanks guys, I think one crucial piece of info I forgot to include was that I'm dropped on BC BR series coilovers but since I'm getting a full audio boot install, I'll be getting new longer springs to accommodate for a good stance, not a dumped / dub style!

I understand this changes what spacers you guys have suggested. I'm going to raise the car and get 215/35 fronts and hopefully 255/30 rear, on what I believe (with the measurements I've taken, since reading the stamped info on the back so awkward!!) are 8.5j front and 10j rear – read on

I think I've had to recalculate!!
The way I've worked that out is measuring the overall width of the wheel and subtracting 1" or 25mm off the measurement since the measurement is take from the outside lip of wheel to inner lip of hub mounting side. This will therefore equate to..

Fronts
240mm overall width
(Less 25mm)
= 215mm ..... = 8.5J if converted
.. Centre Line is 120mm (240 divided by 2)
.. Backspace is 160mm

Therefore the diff between Backspace and Centreline is 40mm so at offset of ET40 front!

Rear

280mm overall width
(Less 25mm)
= 255mm ..... = 10.2inches (J) if converted
.. Centre Line is 127.5mm (255 divided by 2)
.. Backspace is 165mm

Therefore the diff between Backspace and Centreline is 37.5mm, so an offset of ET38 rear!

I simply can't go wrong with a measuring tape I figured and would rather do the calculations myself than to go by Illegible stamped info.

How does this sound now??
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      01-25-2013, 01:12 PM   #13
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ok based on your new calculations, 20mm up front and 12mm in the back will put both rims 1mm behind the fender. If you want a little more poke I would say 25mm up front(which I don't know if they make that) (which will put you 4mm pass the fender) and 20mm spacers in the rear (will put you 7mm pass the fender)

also how are you BC coils? How low do they go? And do you have to adjust the preload for them to go real low?
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      01-28-2013, 06:00 PM   #14
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Quote:
Originally Posted by ACEE View Post
ok based on your new calculations, 20mm up front and 12mm in the back will put both rims 1mm behind the fender. If you want a little more poke I would say 25mm up front(which I don't know if they make that) (which will put you 4mm pass the fender) and 20mm spacers in the rear (will put you 7mm pass the fender)

also how are you BC coils? How low do they go? And do you have to adjust the preload for them to go real low?
BC's go pretty low alright, that sunken look - that low! I'm looking to buy slightly longer springs to accomodate for a boot full or audio upgrades LOL. You get rear adjusters to have control of rear damper settings... is that what you're referring to?
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      01-28-2013, 07:50 PM   #15
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I'm assuming these are two or three piece wheels - is it possible that they were intended to be assembled with the centers outboard of the barrels and that someone took the rears apart and reassembled them with the centers inboard of the barrels? And the centers are just about 15mm thick at the point where the barrels mount to them?
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      01-29-2013, 05:39 AM   #16
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Wow, I wish I had an answer for that but I've no knowledge. Since I bought them off ebay and the previous owner had them on his E46 M3, he was either not very clued up or played dumb, either way I took a gamble and I'm sure it'll pay off
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      01-29-2013, 09:43 AM   #17
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I'd just look at them, if they were both originally ET40 but the fronts have the inner lip of the barrels outside the centers and the rears have the inner lip of the barrels inside the centers that would explain the discrepancy between actual offset and the stampings.

I've never done this - only BBS wheels I've ever had have all been one piece - but it seems that this is occasionally done to change the offset and it doesn't seem that it's a real safety issue, as different offsets are often made with the same centers from BBS.
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