Everything You Ever Wanted To Know About Wheel Spacers

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Everything You Ever Wanted To Know About Wheel Spacers
This page consists of everything we have learned about wheel spacers for BMWs. A lot of this info also applies to other makes as well. It's a very long and comprehensive collection of data, tips, and technical info. We hope it's useful to you but if you should have any further questions, please call or e-mail us.

Why Use Wheel Spacers?

-Appearance. You want to push the wheels out for a better stance and more aggressive look. This is totally subjective to your personal tastes. And we can't tell you what to like...

-Clearance. Many wheels are not compatible with big brake kits. The spoke of the wheel will scrape the new brake caliper and you need a wheel spacer to push the wheel spoke away from the caliper.

-Correction. You may have bought a set of wheels that don't have the correct offset for your car. The offset may be too high, resulting in the wheels sitting too far inward. This is both ugly and incorrect as the tire can now rub on the inside wheel well, or on suspension components, etc. A wheel spacer will push the wheel out and 'correct' the offset.

-Handling. By spacing the wheels further apart, you can make the car more stable and corner better. You can gain a similar effect as adding a wider wheel without the added weight and expense.

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What Size Should I Use?
This is one of our most commonly asked questions. Unfortunately, it has no easy answer. Picking a spacer that meets your needs is not as easy as it sounds. If it were easy, we'd all be using the same size. There are a few different reasons why people need spacers so every situation ends up being different. But every situation can be resolved by finding out how much available space you have to work with. That means measuring the tire-fender clearance. This empty space will likely be your spacer size. You don't want to exceed the empty space because that will lead to the tire rubbing on the fender. And you don't want to get too thin of a spacer because that may not meet your needs.



Turner Motorsport may be the biggest BMW wheel spacer dealer in the world. As such we have learned not to make assumptions on spacer size. Every situation is different and the best advice we can give is to measure your car. It's tempting to listen to what everyone else is running but unless they have your exact wheel, exact tire, exact suspension, and exact suspension settings, no one can tell you what spacer size to use. They can only guess... Please keep in mind that spacers that have been installed and tested cannot be returned. This is to be fair to the next customer who expects new, top quality parts from us. Which is all the more reason to be precise about what size you can install.

Here are some easy ways to measure your wheel gap -

Old-Fashioned Tape Measure
With the car on the ground, hang a piece of masking tape from your fender. Stick a quarter or a nickel on the end so that it hangs straight down. Next measure in from the masking tape to the outside edge of your tire. This will tell you how much space you have until the tire would contact the lip of the fender. Pick a spacer that is slightly less than this measurement. This will ensure the tire does not rub on the fender lip.



Even More Old-Fashioned Rulers
Same as the method above but if you don't have masking tape to hang from the fender, you can use a straight-edge or ruler and another ruler or tape measure. Gently hold the straight-edge from the bottom of the fender lip. Measure in to the outiside of the tire. The gap between the straight-edge and the tire is your available clearance. Choose a spacer size slightly less than this dimension.



Wheel Studs and Washers
For this method, you would purchase at least two wheel studs to thread into the hub and corresponding nuts to lock the wheel down ([URL="http://www.turnermotorsport.com/html/detail.asp?PRODUCT_ID=TWH9950"]link to TMS 90mm studs[/URL]). Remove your wheel and bolts. Thread the studs into the hub. Place washers down the stud to the hub. Slide the wheel over the studs. If it makes contact with the caliper or suspension, add more washers. Once the clearances are set, lock the wheel down with the nuts. Lower the car to the ground and roll - don't drive! - the car back and forth so the suspension will settle. Check your clearances again and also for tire-fender contact. Adjust if necessary. The end thickness of your washers will be your minimum spacer size. If you have space left over before the tire hits the fender, consider going with an even bigger spacer for improved looks.
Remember to remove your studs or install them the proper way before driving.


Studs and washers installed in the hub. Pictured is a BBS 90mm stud and 5 washers (roughly 15mm).


Studs and washers installed with the wheel.


BMW Wheel Pin and Washers
If wheel studs are not available to you, you can use the factory BMW wheel pin tool in your tool kit. More than one pin is recommended. This method does not allow you to set the car on the ground as the wheel pin will not support the weight of the car and there is no way to fasten the wheel to the hub. Don't even try it! Remove your wheel from the car. Insert the pins into the hub. Slide M12 sized washers onto the pin down to the hub. Slide your wheel onto the pins until it contacts the caliper, suspension, etc.. Add washers until the wheel sufficiently clears. The thickness of your stack of washers is the size of your spacer.


Factory BMW wheel pin tool installed with washers.

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Wheel Spacers With Wheel Studs

Wheel studs protrude from the hub and help to locate the wheel to the hub. A wheel nut (lugnut) would then be used to fasten the wheel to the hub. The issue with using them with spacers is that it can actually push the wheel out too far, leaving you without enough threads to securely fasten the wheel nut. Here are some things to keep in mind when choosing studs and spacers -

length of available stud sticking out from the hub

brake rotor hat thickness (varies)

wheel bolt bore depth (the depth of the hole in the wheel) (varies)

spacer size

number of turns on your wheel nut (6.5 turns or 10mm for a 12x1.5 stud/nut)

For instance, a TMS 75mm wheel stud usually has enough room left over to use a 10mm spacer. However, a big brake kit may have a thicker rotor hat than stock which would reduce your available space on the stud. As well, the thickness inside the bolt bore can vary a lot as well. A thicker wheel will reduce your available threads. The solution here is to use a longer wheel stud.

TMS Wheel Spacer and Stud Design in SolidWorks
(click the image below for a super-sized version)
This image was created by the TMS engineers in SolidWorks - a CAD program. All components are scaled correctly in relation to one another. Here you can see the relationship between wheel spacers, wheels, and the hub (wheel bearing). You can also see how brake rotor hats and wheels also play into spacer fitment.

This particular drawing is of a E36 M3 with a TMS 12.5mm spacer, a stock BMW brake rotor, a TMS 75mm wheel stud and TMS wheel nut, and a generic wheel design. There's a lot to look at on this drawing but things to pay particular attention to are -

the fitment of the spacer (green) to the hub (red),

the fitment of the wheel (grey) to the spacer (green),

the thickness of the wheel bolt bore where the nut is fastened. A deeper bore will result in less threads for the nut to engage -OR- will require a longer than normal wheel bolt.


[URL="http://www.turnermotorsport.com/html/images/spacers/tms_solidworks_spacer_hub_drawing_xlg.jpg"]Click here to supersize[/URL]

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The 10mm Spacer Dilemma

10mm wheel spacers are one of the most common spacer sizes out there. However, what a lot of people don't realize is that a 10mm size is not a true fitment on any BMW. It's considered a "tuner" fitment, meaning some extra thought is usually required to correctly install them. Only with the right combination of parts will a 10mm spacer fit without a vibration or other fitment issues.

Factory Hub Lips Are Greater Than 10mm
The depth of the lip on the car where the spacer will rest will vary. The available lip space may be 11mm and a 10mm spacer with its own hubcentric lip cannot physically fit. The spacer will bottom out on the lip instead of on the brake hat, leaving a gap between the spacer and the rotor hat. The biggest reason for this is the thickness of the rotor hat. The thickness varies by manufacturer and design. A thinner hat (such as used with aluminum Euro Floating rotors) will leave more lip protruding and make the problem worse. Most spacer manufacturers add an extra chamfer, or shoulder, to push the hubcentric lip further out. The extra chamfer clears any extra part of the stock lip. The other way to get the spacer to fit is to shave the stock lip with a metal file. While not the most elegant solution, it works.

Wheels With Incorrect Beveled Edge
Some wheels (Kosei in particular) have a beveled mounting surface that is at a different angle than on the spacer. Think of really precise puzzle pieces fitting together - if the pieces are not precisely machined to match, the parts don't fit together very well. The wheel will vibrate since enough of the wheel bore is not resting on the spacer lip.

Note that all of this only occurs when using a 10mm spacer with its own hubcentric lip. Any spacer over 10mm is not affected by this. The [URL="http://www.turnermotorsport.com/html/detail.asp?PRODUCT_ID=TWH9905002"]TMS 10mm spacers with Hub Extender [/URL]is also exempt from this as the spacer has a flush outer face and will not interfere with the mounting surface of the wheel.

What's the solution? You could shave the stock lip on the car so its depth is under 10mm... Or you could just use a 12mm spacer and be done with it. The difference between a 10mm spacer and a 12mm spacer is the thickness of a nickel! The 2mm difference is smaller than the thickness of a CF memory card or your typical cardboard box. Trust us - 12mm is the way to go. The TMS Hub Extender/10mm Spacer set also works well and allows you to swap spacers in and out for different setups.

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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 - [URL="http://www.turnermotorsport.com/html/detail.asp?PRODUCT_ID=3075740725"]15mm adatpers[/URL], [URL="http://www.turnermotorsport.com/html/detail.asp?PRODUCT_ID=4075740725"]20mm adapters[/URL].

Here's a not-uncommon situation:
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!

Another common scenario:
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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Miscellaneous Notes and Details on Spacers

-Most BMWs will take a 15-20mm spacer when used with the stock wheel/tire setup. This is because the German TUV (similar to our own DOT) still requires adequate clearance for snow chains. These are still widely used in Europe, especially in The Netherlands, Norway, and Sweden even though they are obsolete or irrelevant in other markets. The TUV also requires that every car in Germany be equipped with either dedicated snow tires or snow chains for winter driving.


-All BMWs use hubcentric wheels. When mounted to the car, the wheel rests on a lip instead of the wheel bolts or studs. The lip is usually 9-10.5mm in depth. The lip contributes to the strength of the wheel and the wheel cannot safely be used without a lip. The wheel bolts are not strong enough to support the weight and loads generated through the wheel.

Any spacer smaller than 10mm will not have a hubcentric lip on it. It's physically impossible since the spacer slides over the existing lip but is not thick enough to take the lip's place (the standard lip still protrudes through the spacer). With a 9mm lip, a 5mm spacer will only leave 4mm of stock lip left for the wheel to rest on. This is important to keep in mind when considering your wheel/spacer setup. A wheel with a [URL="http://www.turnermotorsport.com/image/wheels/wheel_hub.jpg"]beveled edge[/URL] on the back will not adequately rest on the lip, resulting in a vibration because the wheel is not truly centered on the hub.

For most 5-lug BMW applications, Turner Motorsport offers a [URL="http://www.turnermotorsport.com/html/detail.asp?PRODUCT_ID=TWH9905001"]hub-extender.[/URL] This takes the place of your hub's dust cap and adds an extra 10mm of lip for the wheel to rest on. Using the example above, instead of 4mm left over on the lip, you now have 14mm of lip to use. With the [URL="http://www.turnermotorsport.com/html/detail.asp?PRODUCT_ID=TWH9905001"]hub extenders[/URL], you can also change spacers around without fear of losing lip space - it can be used with a 3mm, 5mm, 8mm, or 10mm spacer.

Spacers with their own integrated hubcentric lip are: 10mm*, 12mm, 12.5mm, 15mm, 18mm, 20mm, 25mm, and 30mm.
* -- Note that H&R and Turner Motorsport each make a 10mm hubcentric spacer but due to interferences between the spacer and lip, it's best to leave this to specialized applications. The lip on the car must be shaved down so the 10mm spacer will fit flush on the rotor hat.


-When talking about tire sizes, remember that sizes vary a great deal from one manufacturer to another. Even though the tire size is listed as "245", the actual widths can be hugely different among brands and even tire types. Tire manufacturers publish their actual widths on their websites. This is important because a setup with a wider 225 tire may rub versus a setup running a narrower 225 tire.


-When installing spacers, never use anti-seize or grease between the spacer and the rotor hat face. In fact, you should scrub this area clean with Scotch-Brite or a wire wheel attachment. A thin amount of anti-seize can be placed on the lip of the hub for the spacer to sit on and on the spacer lip for the wheel to rest on. The number one reason for wheel vibrations with spacers is rust or some other substance on the rotor hat.


-Removing spacers can be a frustrating experience. Many spacers have a chamfer along the inner edge and with a hammer and chisel, the spacer can be knocked off the hub. However, this will easily damage the spacer. The newest generation of TMS Wheel Spacers include pockets around the entire circumference of the spacer. This allows you to pry the spacer without damaging the material

Lots of good info here man. Keep it comming!