BMW M3 Forum (E90 E92) - View Single Post - Everything You Ever Wanted To Know About Spacers

rzm3 · 01-01-2010, 01:23 AM

Spacers for Wheel Offset Issues
A lot of the calls we get are to correct a wheel offset when using a wheel not intended for the chassis. Examples - E36 M3 wheels on an E30 M3 or E46 wheels on an E34. The 3-series cars generally have a higher offset than the 5-series. This results in the wheel being tucked in too far and making contact with brakes, suspension components, or the inner wheel well. The differences in offset are usually around 15-20mm but that's not the whole story...

Not only is the offset different but the width of the wheel is usually different as well. An E30 M3 had a 7.0" stock wheel. Most E36 wheels are 7.5" or 8.0" and a higher offset. So not only are you fighting the higher offset but the wheel is physically wider. If the wheels were the same width, your spacer would simply be the differences in the offsets. But add the extra width and you now have another dimension to figure out. The mathematical formula is very intricate but you can find offset calculators online. Call us if you need further assistance.

E39 owners need to be careful because their wheels use a different center bore than most other BMWs. This limits their wheel choices. The E39 center bore is 74.0mm. Just about all other BMWs use a 72.5mm center bore. Depending on what the wheel was originally designed for (E36, E46, etc) there may be an offset difference to deal with as well. In the case of fitting one of these wheels to an E39, H&R has developed a wheel spacer adapter that is 72.5CB on the wheel side and 74.0CB on the hub side. The adapters come in 15mm and 20mm sizes to take up the offset difference. See these adapters on our website here - 15mm adatpers, 20mm adapters.

Here are some not-uncommon situations:

E36 M3 wheels on an E30 M3. The stock wheel is a 15x7.0 ET20. The new wheel will be a 17x8.0 ET40. If we just installed the wheel with no spacers, it would be 33mm futher inward than stock but will stick out 7mm more than stock. The stock E30 M3 has a lot of wheel clearance before the stock wheel will hit the fender (20mm using the measuring methods above). So right away we know that a big spacer can be used without worrying about it rubbing on the outside fender. Let's say we put just a 7mm spacer on - it will bring the new wheel to the same position as the stock wheel on the outside, but will still be 26mm tucked in towards the strut (and rub on the strut). But we know that we can safely go another 20mm more and still not touch the fender. If we put a 25mm spacer on the new wheel, it will rest 18mm further out than stock and only 8mm further in. We now have a wheel that is spaced out enough to sit flush with the fender and not rub on the inside!

Winter Wheel Package for E92 335 coupe. Many people are finding themselves without a true winter wheel package on the E9X models. These cars come with a stock wheel with an offset quite a bit lower than the E36 and E46 predecessors. When trying to fit these E36/E46 wheels to the 335, they sit too far inward because of their higher offsets and narrower width. The best solution would be to buy wheels with the correct offset. Aside from that, spacers can be used to make up the difference.

First measure your stock wheel clearance as outlined above.
We'll use a 17x8.0 ET40 as the winter wheel. The stock 335 wheel is a 18x8.0 ET34. In this case, you only need a 6mm spacer to get it back to the original stance. However, the back wheel is a 18x8.5 ET37 and to use the winter wheel you will need a 9mm spacer to get it back to stock stance. Because you measured beforehand, you know how much more room you have to space the stock wheels out. This is critical because 6mm and 9mm spacers don't exist; you will need something larger and you need to make sure there is adequate clearance for it.

E46 M3 19" ZCP wheels on an E92 335 coupe. The stock sport package wheel is a 18x8.0 ET34 and 18x8.5 ET37. The E46 M3 uses a 19x8.0 ET47 in front and a 19x9.5 ET27 in the rear. Using our calculations, the front will sit further in by 13mm. A 15mm spacer will bring it back to the factory wheel stance. Measuring the stock wheel beforehand we know that it will take a 12mm spacer before the stock wheel contacts the fender. Therefore, adding 15 and 12 gets us to 27mm. So the E46 M3 front wheel will take a 20-25mm spacer in order to sit flush with the E92 fender. The M3 rear wheel will sit only 3mm in but an additional 23mm further out. Measuring beforehand, we found that the stock wheel only has 15mm of clearance before it hits the fender. The M3 wheel will most likely rub on the fender, requiring the fender to be rolled or negative camber added for more clearance.

01-01-2010, 01:23 AM	#6
rzm3 Moderator 673 Rep 4,737 Posts Drives: E92 M3 Join Date: Aug 2007 Location: USA iTrader: (18)	Spacers for Wheel Offset Issues A lot of the calls we get are to correct a wheel offset when using a wheel not intended for the chassis. Examples - E36 M3 wheels on an E30 M3 or E46 wheels on an E34. The 3-series cars generally have a higher offset than the 5-series. This results in the wheel being tucked in too far and making contact with brakes, suspension components, or the inner wheel well. The differences in offset are usually around 15-20mm but that's not the whole story... Not only is the offset different but the width of the wheel is usually different as well. An E30 M3 had a 7.0" stock wheel. Most E36 wheels are 7.5" or 8.0" and a higher offset. So not only are you fighting the higher offset but the wheel is physically wider. If the wheels were the same width, your spacer would simply be the differences in the offsets. But add the extra width and you now have another dimension to figure out. The mathematical formula is very intricate but you can find offset calculators online. Call us if you need further assistance. E39 owners need to be careful because their wheels use a different center bore than most other BMWs. This limits their wheel choices. The E39 center bore is 74.0mm. Just about all other BMWs use a 72.5mm center bore. Depending on what the wheel was originally designed for (E36, E46, etc) there may be an offset difference to deal with as well. In the case of fitting one of these wheels to an E39, H&R has developed a wheel spacer adapter that is 72.5CB on the wheel side and 74.0CB on the hub side. The adapters come in 15mm and 20mm sizes to take up the offset difference. See these adapters on our website here - 15mm adatpers, 20mm adapters. Here are some not-uncommon situations: E36 M3 wheels on an E30 M3. The stock wheel is a 15x7.0 ET20. The new wheel will be a 17x8.0 ET40. If we just installed the wheel with no spacers, it would be 33mm futher inward than stock but will stick out 7mm more than stock. The stock E30 M3 has a lot of wheel clearance before the stock wheel will hit the fender (20mm using the measuring methods above). So right away we know that a big spacer can be used without worrying about it rubbing on the outside fender. Let's say we put just a 7mm spacer on - it will bring the new wheel to the same position as the stock wheel on the outside, but will still be 26mm tucked in towards the strut (and rub on the strut). But we know that we can safely go another 20mm more and still not touch the fender. If we put a 25mm spacer on the new wheel, it will rest 18mm further out than stock and only 8mm further in. We now have a wheel that is spaced out enough to sit flush with the fender and not rub on the inside! Winter Wheel Package for E92 335 coupe. Many people are finding themselves without a true winter wheel package on the E9X models. These cars come with a stock wheel with an offset quite a bit lower than the E36 and E46 predecessors. When trying to fit these E36/E46 wheels to the 335, they sit too far inward because of their higher offsets and narrower width. The best solution would be to buy wheels with the correct offset. Aside from that, spacers can be used to make up the difference. First measure your stock wheel clearance as outlined above. We'll use a 17x8.0 ET40 as the winter wheel. The stock 335 wheel is a 18x8.0 ET34. In this case, you only need a 6mm spacer to get it back to the original stance. However, the back wheel is a 18x8.5 ET37 and to use the winter wheel you will need a 9mm spacer to get it back to stock stance. Because you measured beforehand, you know how much more room you have to space the stock wheels out. This is critical because 6mm and 9mm spacers don't exist; you will need something larger and you need to make sure there is adequate clearance for it. E46 M3 19" ZCP wheels on an E92 335 coupe. The stock sport package wheel is a 18x8.0 ET34 and 18x8.5 ET37. The E46 M3 uses a 19x8.0 ET47 in front and a 19x9.5 ET27 in the rear. Using our calculations, the front will sit further in by 13mm. A 15mm spacer will bring it back to the factory wheel stance. Measuring the stock wheel beforehand we know that it will take a 12mm spacer before the stock wheel contacts the fender. Therefore, adding 15 and 12 gets us to 27mm. So the E46 M3 front wheel will take a 20-25mm spacer in order to sit flush with the E92 fender. The M3 rear wheel will sit only 3mm in but an additional 23mm further out. Measuring beforehand, we found that the stock wheel only has 15mm of clearance before it hits the fender. The M3 wheel will most likely rub on the fender, requiring the fender to be rolled or negative camber added for more clearance.
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