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      08-29-2012, 09:01 AM   #1
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If I wanted to change to 8x18, what would be the perfect ET?

Let's see if my calculations are correct

Point of beginning. BMW's measures " 7,5x18 ET49 " and " 8,5x18 ET52 ".

My car is a BMW e81 130i pack M.

1 º FRONT RIM (to increase ahead to 8x18, we would have 1/4 of 1 inch (25,4 mm) more as every side), be read:
6,35 mm + (RIM 7,5) + 6,35 mm = RIM 8,0
Therefore and in order that it was not rubbing within we extract the ET in 6,35 mm.
Total ET 42,65 (aprox. ET43).

2 º BACK RIM (to reduce behind to 8x18, we would have 1/4 inch less as every side), be read:
-6,35 mm + (RIM 8,5)-6,35 mm = RIM 8,0
Therefore and to compensate we extract ET, in two parts. The first one to compare the front exit (6,35) and the second thing to compensate the loss of width in the back wheel (6,35 x 2 = 12,7).
Total 19,05 mm towards out. Total ET52 - 19,05 = 32.95 (aprox. ET33).

8x18 ET43
8x18 ET33

And in the differential of checking it would stay ...:
8x18 ET43 re-turned made-to-measure original it would be ... 7,5x18 ET 36,65 (aprox. ET37)---12,35 (49 - 36,65) millimeters towards out with regard to the measure OEM.
8x18 ET33 re-turned made-to-measure original it would be ... 8,5x18 ET 39,35 (aprox. ET39)---12,65 (52 - 39,35) millimeters towards out with regard to the measure OEM.


I want to install these wheels:


A e81 could look at this:


These wheels are habitual in WRC, specially in production category:





Last edited by SSunklug; 08-29-2012 at 11:02 AM.
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      08-29-2012, 05:36 PM   #2
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I get your math up front and it seems correct. I have no idea why you multiplied the factor you used times 3 then added it in the rear?. A 18x8 et 33 rear will be very close to rubbing depending on tire size, camber, etc. I'd go with 18x8 et 42ish all around.
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      08-29-2012, 05:58 PM   #3
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Quote:
Originally Posted by Eyeman View Post
I get your math up front and it seems correct. I have no idea why you multiplied the factor you used times 3 then added it in the rear?. A 18x8 et 33 rear will be very close to rubbing depending on tire size, camber, etc. I'd go with 18x8 et 42ish all around.
I have reduced it, because 8x18 it is a measure smaller than 8,5x18. If not the 8x18 wheel finished more inside.
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      08-29-2012, 05:59 PM   #4
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8x18 ET43 could rub?
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      08-29-2012, 06:01 PM   #5
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Thank you very much for answering. I know my english is not perfect.
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      08-29-2012, 07:40 PM   #6
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Your proposed offsets would probably be fine. Et45 all around would work too.
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      08-29-2012, 09:05 PM   #7
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Quote:
Originally Posted by hardliner130 View Post
Your proposed offsets would probably be fine. Et45 all around would work too.
Thanks!!!!

Then... is et45 better?
Have you got any pic with those sizes?
Not brushed on the inside with et45?
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      08-29-2012, 10:25 PM   #8
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Hi there, I have 18x8 wheels, ET is 35 and... well, rear they are just fine but cannot go any wider-taller than 235/40, and it will depend on the tire brand. with ET 33 at the back you will rub unlesss you use 225 max and add a bit of camber. on the front 43 would be just fine, I have 35 front and had to remove the alignment pin as they rubbed in some cases, but my car is very low, if you are in stock height you will be fine, but think if you plan to lower. I'd go 40 front and 35 rear with sqaure 225/40/18.
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      08-30-2012, 07:35 AM   #9
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Quote:
Originally Posted by maupineda View Post
Hi there, I have 18x8 wheels, ET is 35 and... well, rear they are just fine but cannot go any wider-taller than 235/40, and it will depend on the tire brand. with ET 33 at the back you will rub unlesss you use 225 max and add a bit of camber. on the front 43 would be just fine, I have 35 front and had to remove the alignment pin as they rubbed in some cases, but my car is very low, if you are in stock height you will be fine, but think if you plan to lower. I'd go 40 front and 35 rear with sqaure 225/40/18.
Is a perfect answer.it will help me a lot. Have you got a few pics?

What's the meaning of "alignment pin"?
Will I have problems with the ET43 because it could rub in?
Could ET40 rub out?

PD te lo pongo también en español que seguro que también lo entiendes y por si mi ingles no es perfecto.

Dices que mejor ET40 que ET43 pero si dices que el ET43 queda justo, si le meto ET40 que obviamente queda mas desplazado hacia el exterior entonces si podría rozar,no?

O quieres decir que con ET43 me podría rozar por la parte interior y que mejor sacarlo hacia afuera para que no rozase?

Es que con mas medidas de arriba, al ensanchar también he tenido en cuenta eso y por eso la medida sale 6,35 hacia afuera y el ET es menor por lo que no debería rozar, salvo que fuese por el tamaño o la forma del neumático.

Last edited by SSunklug; 08-30-2012 at 07:50 AM.
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      08-30-2012, 08:48 AM   #10
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Quote:
Originally Posted by SSunklug View Post
Is a perfect answer.it will help me a lot. Have you got a few pics?

What's the meaning of "alignment pin"?
Will I have problems with the ET43 because it could rub in?
Could ET40 rub out?

PD te lo pongo también en español que seguro que también lo entiendes y por si mi ingles no es perfecto.

Dices que mejor ET40 que ET43 pero si dices que el ET43 queda justo, si le meto ET40 que obviamente queda mas desplazado hacia el exterior entonces si podría rozar,no?

O quieres decir que con ET43 me podría rozar por la parte interior y que mejor sacarlo hacia afuera para que no rozase?

Es que con mas medidas de arriba, al ensanchar también he tenido en cuenta eso y por eso la medida sale 6,35 hacia afuera y el ET es menor por lo que no debería rozar, salvo que fuese por el tamaño o la forma del neumático.
Creo que ET40 seria mejor, aunque 43 te da un poco mas de claro y podrías bajarlo con coils. Yo me quedaría con 40 por el tema estetico. La parte de atras tiene mas espacio pero las medidas que usaste son del e82, el e81/87 usa rines ET 47 adelante y 49 atras y son de 7.0 adelante y 7.5 atrás. El e82 es mas ancho de atras. Por eso es que tus calculos te dan un ET33 atras, pero en realidad es demasiado.

Te comparto una foto de mi E87 (130i) con rines 18x8 ET 35, los rines son iguales adelante y atras. Si ves, adelante ya estoy en el limite, atras aun me quedan unos 2 o 3 mm de espacio, pero mi llanta atras es 235/40, si pongo 225/40 tendria mas espacio, aun asi no rosa nada atras, pero adelante sin quitar los pernos de alineacion si llega a rozar un poco, por eso te recomiendo ET40. Sin ellos parece que no, pero tampoco paso muy rapido en los bados.



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      08-30-2012, 08:51 AM   #11
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Another pic more.



And again, it all depends if you wanto to lower her much in the future, if you use the stock height then 35 is fine, 40 will be ideal and 43 would be safer, also 35's look odd (they appeared to be too pushed out) if not lowered. I would go with the middle option, that is 40. but again you will still be limited to the width of the tires you could use. I cannot by any mean run any wider that 225 front or 235 rear, and some tires are wider, so even some 225 tires could rub so I have to be careful when selecting tires.

Last edited by maupineda; 08-30-2012 at 08:56 AM.
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      08-30-2012, 10:42 AM   #12
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They look like the alufelgen's diamond!! nice car
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      08-30-2012, 10:50 AM   #13
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I have 17x8 et 40 wheels all around.

You're right on the front - an extra 2-3 mm offset would kill my rub in the front on 245 Star specs.

You're rear is correct IMO. The 18x8 et40 in the rear easily leaves 10-15mm on the table outboard - to the point that I'm considering spacers
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      08-30-2012, 11:09 AM   #14
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Quote:
Originally Posted by maupineda View Post
Another pic more.
And again, it all depends if you wanto to lower her much in the future, if you use the stock height then 35 is fine, 40 will be ideal and 43 would be safer, also 35's look odd (they appeared to be too pushed out) if not lowered. I would go with the middle option, that is 40. but again you will still be limited to the width of the tires you could use. I cannot by any mean run any wider that 225 front or 235 rear, and some tires are wider, so even some 225 tires could rub so I have to be careful when selecting tires.
A really complete answer.

The sizes in e81-e87 are:
207M wheels
7x17 ET47
7,5x17 ET47

First 208M wheels
7,5x18 ET49
8x18 ET49

Second 208M
7,5x18 ET49
8,5x18 ET52


You can see it here...: http://felgenkatalog.auto-treff.com/

My dude is, have you got problems with rub inside or outside?
ET40 is more outside than ET43
ET43 is more inside, i won't have to be problems with rub,or not?
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      08-30-2012, 11:16 AM   #15
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Quote:
Originally Posted by BrokenVert View Post
I have 17x8 et 40 wheels all around.

You're right on the front - an extra 2-3 mm offset would kill my rub in the front on 245 Star specs.

You're rear is correct IMO. The 18x8 et40 in the rear easily leaves 10-15mm on the table outboard - to the point that I'm considering spacers
What's the meaning of IMO???? I don't understand that word .
So in your opinion it would be prefer ET30 in the rear better than ET40 in your car?

And... ET43 in the front... would be it all right?

But you have a e82-e88...no?

Could you insert a pics of your car?

Thanks!!!
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      09-02-2012, 10:05 PM   #16
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Today when I arrived home, I take several pics of my inside wheel hole.
I were able to see that it's very near, about 1 centimeter.
I have 207M wheels. 7x17 ET47.
If for example, 208M wheels, are 7,5x17 ET49 these have to finish really near, a few milimeters.
What's your opinion?


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      09-04-2012, 08:15 PM   #17
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1cm isn't too close to the strut, actually its a big clearance. 3mm would be "close". You only need enough clearance for the tyre deformation.

I've heard the E87 has a bit more space on the rear fender than the E82. Most people on the forum have experience with E82 coupe only.

Its hard to discuss offsets because you didn't say what size tyre you would like to use.
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      09-10-2012, 05:15 PM   #18
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Quote:
Originally Posted by John_01 View Post
1cm isn't too close to the strut, actually its a big clearance. 3mm would be "close". You only need enough clearance for the tyre deformation.

I've heard the E87 has a bit more space on the rear fender than the E82. Most people on the forum have experience with E82 coupe only.

Its hard to discuss offsets because you didn't say what size tyre you would like to use.
I'd like to use 225/40 R18 or maybe 235/40 R18. Last one is the most possible.

I think that "E87 has a bit more space on the rear fender than the E82" is truth.

I've seen this car, with "M alloy wheels styling 216M 18inch with Goodyear NCT5 Runflat tires 205/40R18 frond and 225/35R18 rear"
AND
Eibach Pro Spacer spacers front & rear (24mm per axle)

Stock wheels are: 7,5x18 ET49 and 8,5x18 ET52. with a 24mm spacers, it has been the same as:
7,5x18 ET25 and 8,5x18 ET28, and these look... (http://www.1addicts.com/forums/showt...php?t=210381):



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      09-11-2012, 12:47 AM   #19
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Quote:
Originally Posted by SSunklug View Post
I'd like to use 225/40 R18 or maybe 235/40 R18. Last one is the most possible.

I've seen this car, with "M alloy wheels styling 216M 18inch with Goodyear NCT5 Runflat tires 205/40R18 frond and 225/35R18 rear"
AND
Eibach Pro Spacer spacers front & rear (24mm per axle)
24mm is a big spacer! Are you sure its a 24m per side? Anyway the 205 front tyres are narrow, especially those goodyear runflats, so that also makes a BIG difference too.

In the case of E82 coupe, you need about ET45 to fit 235/40 front tyre. However if you get ET43 and make a small camber adjustment it would also be fine in the case of most 235 road tyres. Except some track style tyres have square shoulders that could cause problems for the front. If fitting 225/40 front tyres, again it depends on the tyre brand, but around ET40 to ET43 would be safe for the E82.
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      09-14-2012, 06:26 AM   #20
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Quote:
Originally Posted by John_01 View Post
24mm is a big spacer! Are you sure its a 24m per side? Anyway the 205 front tyres are narrow, especially those goodyear runflats, so that also makes a BIG difference too.

In the case of E82 coupe, you need about ET45 to fit 235/40 front tyre. However if you get ET43 and make a small camber adjustment it would also be fine in the case of most 235 road tyres. Except some track style tyres have square shoulders that could cause problems for the front. If fitting 225/40 front tyres, again it depends on the tyre brand, but around ET40 to ET43 would be safe for the E82.
My car is an e81 130i. So it's different that e82,at least rear wheels,no?

He wrote that had installed 24mm front and rear spacers. But i don't know it's truth.
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      09-14-2012, 10:22 AM   #21
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Im running winter square setup 17 225/45 8J with et47 but it is a bit to close to strut and still far away from fenders so I think et45 et40 would be perfect
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      09-14-2012, 10:45 AM   #22
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Quote:
Originally Posted by RimasRS View Post
Im running winter square setup 17 225/45 8J with et47 but it is a bit to close to strut and still far away from fenders so I think et45 et40 would be perfect
Thanks!!!

Hace you got any pic?
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