Questions abound about what wheel spacers are, how they work, and which ones to choose. Basically, a wheel spacer is a metal washer that fits between the hub of the car and the wheel, pushing the wheel further outwards towards the edge of the body. Spacers are typically used for the purpose of allowing a wheel to fit which would otherwise contact the brake caliper or suspension components, or, to push the wheel outwards to fit more flush with the edge of the fender for better aesthetics. For the purposes of this article we will be mainly focusing on spacers for modern Audi, BMW, Porsche and Volkswagen applications, specifically H&R brand "DR" and "DRA" type spacers.
First, an overview of spacers: H&R "DR" type spacers are 135mm to 149mm in outside diameter which matches the diameter of the hub of the car, the width can vary between as low as 3mm up to 25 or 30mm. The DR type spacers have holes machined in them which will match the bolt pattern of the vehicle (5x100, 5x112, 5x120, 5x130 for this discussion) and must be used with longer wheel lug bolts to account for the width of the spacer chosen. H&R "DRA" type spacers differ from the DR type in that they are offered in thicknesses of 20mm - 30mm and can go up to 45mm for some Porsche applications. DRA type spacers also differ in their attachment method, the spacers have 5 holes which are used in conjunction with supplied lug bolts to attach the spacer to the hub, the wheel is then attached to the spacer using the existing wheel bolts which thread into 5 threaded holes on the spacer itself.
Spacer selection: Choosing the correct spacers involves a few criteria, first it is necessary to find the optimum thickness to use from the available spacer selection. For some the optimum spacer may be the smallest spacer possible that allows clearance of the wheel/tire to brake or suspension components. For others the optimum thickness may be the thickest spacer possible that places the wheel/tire assembly flush to the edge of the fender while still allowing it to travel through it's normal range of motion during suspension movement and turning while not contacting the body or other components "rubbing". Spacer selection typically needs three things to ensure a successful choice, research, measurement, and sometimes, despite diligent research and measurement, trial and error. Research of fitment information for the year, make and model of the vehicle accounting for the suspension ride height, wheel width and offset, and tire size, brand, and model is important. Measurement of available clearance (or lack of in the case of brake or suspension contact). Testing of fitted spacers to verify that they provide proper clearance or fit as flush as desired. For measurement tips please see http://www.trakplus.com/measure.
Fitment and compatibility of spacers: An important aspect of spacer fitment is the fitment or interface between the spacer and the hub of the car and the fitment between the spacer and the wheel of the car. Hubs will have a protrusion from the center area of the hub which is used to center the wheel on. The diameter of this protrusion will match the wheel centerbore (typically 57.1mm, 66.56mm, or 71.6mm (Q7) for Audi, 72.5mm or 74mm(E39) for BMW, 71.6mm for Porsche, and 57.1mm or 71.6mm (Touareg) for VW) and can extend by 11 to 15mm outwards (the "hub height"). Depending on the design of the spacer it may have a "maximum hub height" that the spacer is able to fit over. Hub heights are not a tightly controlled tolerance, we recommend measuring the hub height of your vehicle before spacer purchase to ensure compatibility. Spacers with a hubcentric lip have the requirement of needing to match the diameter of the hub protrusion on the inside face in order to fit over the hub snugly as well as match the hub diameter on the outside face so that the wheel fits over the spacer snugly. At some point the bore of the spacer will need to shrink down from the hub bore in order to allow enough material for the hubcentric lip to be machined into the spacer. If this point is lower than the hub height then the spacer will bottom out on the hub protrusion before the back face of the spacer contacts the face of the brake rotor which will not work. On many spacers this transition point will also require a bevel on the outer face of the spacer to transition from the flat surface to the hubcentric lip in order to provide strength to the spacer in this area. These bevels are typically 2mm to 7mm in size which brings us to the spacer to wheel interface.
Wheels are made with a centerbore on the mounting face which corresponds to the diameter of the hub protrusion (57.1mm to 71.6mm depending on the application). Some aftermarket wheels may require a "hubcentric ring" which is inserted to a wheel which has a larger centerbore than the diameter of the hub protrusion which then allows a snug fitment to the hub for proper centering. The centerbore or hubcentric ring will also have a chamfer of 2mm to 7mm which eases installation, however, if the chamfer of the centerbore or hubcentric ring is smaller than the bevel on the outer face of the spacer the bevel will bottom out in the centerbore before the face of the spacer comes into contact with the mounting face of the wheel which will not work. In these cases it may be possible to have custom hubcentric rings made to match the bevel on the spacer or to have the chamfer of the wheels machined to match the bevel on the spacer.
Some thinner DR type spacers such as 3mm, 5mm, and some 8mm thicknesses may not have a hubcentric lip, essentially they are "flat". These type of spacers have no concerns with hub heights or centerbore chamfer interference, however, these two measurements do have a part to play in fitment of spacers of this size. If we take a typical hub height of 11mm - 15mm and a typical centerbore chamfer of 2mm to 7mm then we can see that the wheel centerbore is only making contact with 4mm to 13mm of the hub protrusion. A typical Audi hub will have a 13mm hub height and a 7mm chamfer on the OEM wheels which leaves 5mm of contact, however, to further complicate matters on some vehicles there may only be a thin band 2-3mm wide on the hub protrusion that is the matching diameter of the centerbore of the wheel. In these cases fitting a 3-8mm spacer may result in vibrations as the centerbore of the wheel will be pushed off of the hubcentric band of the hub itself.
Bolts for "DR" type spacers: As touched on earlier "DR" type spacers will require longer lug bolts to account for the thickness of spacer desired. To select the proper bolt it will be necessary to find the specifications of the bolt needed for the wheel and the vehicle. Bolts have a few critical measurements: The diameter of the threaded portion of the bolt in millimeters (typically either 12mm or 14mm). The thread pitch or how many millimeters the bolt threads in with one full turn (typically 1.25 or 1.5). The length of the shaft of the bolt (length of the bolt from the bottom of the head to the end of the threaded portion) The seat of the bolt which is the transition between the head and shaft of the bolt (typically a "cone" seat or a "ball" seat, ball seats may be an R12 12mm radius, R13 13mm radius or R14 14mm radius). The head of the bolt which is typically a 17mm hex head, 19mm hex head, or for some aftermarket wheels a "tuner" head which is typically splined and requires a special socket for installation and removal. Once the specifications of the bolt are known it is recommended to use a bolt with identical specifications with the exception of the length which should be increased by the thickness of the spacer chosen. Example, a wheel which uses a 14x1.5x27mm R13 ball seat bolt would use a a 14x1.5x32mm R13 ball seat bolt if 5mm spacers are used. It can be difficult to find bolts with "tuner" heads in extended lengths.
Bolts for "DRA" type spacers: DRA spacers can typically use either the stock bolts with OEM wheels or the bolts that were provided with your aftermarket wheels. One concern on the 20mm DRA spacers is the length of the bolts or more precisely the length of the bolt that protrudes out of the back of the wheel once inserted. If the bolt protrudes from the back of the wheel by more than 20mm then it will bottom out against the brake rotor prematurely and not provide proper torque to fasten the wheel to the spacer securely. In these situations it will be necessary to use shorter bolts, shorten the existing bolts. Switching to a DR type spacer may be preferred for cost savings if different bolts will need to be sourced.
Spacer Install: Clean hubs of rust or other foreign material with a wire brush. Confirm that the spacer fits flush both against the mounting surface of the wheel as well as against the hub of the car, there should be no gap. If the spacer does not sit flush against either surface do not install it, a spacer with a different configuration should be chosen. Confirm that the lugs are the proper length by threading a single bolt in by hand and counting the rotations until seated, you should get 7 rotations on a 1.5 thread pitch bolt and 8.5 rotations on an 1.25 thread pitch bolt, then rotate the wheel slowly to ensure the lug is not contacting any components on the inside of the hub. Be sure that you are using the correct ball seat or cone seat lugs for the wheel. Install spacers and wheels in the air with zero load on the tire, using the brakes to stop the wheel from turning and torque the lugs to the recommended factory torque first in a star pattern, followed by a circle. Be sure that you get 7.0 turns (+/- .5 turns) of thread engagement on 1.5 thread pitch lug bolts and 8.5 turns (+/- .5 turns) of thread engagement on 1.25 thread pitch lug bolts. Re-torque the lugs after 1 week on brand new wheels.
FAQs: Will spacers affect the handling of the car? Only to an extremely minimal degree, spacers will widen the track of the car which may allow slightly more grip during hard cornering and may increase the turning radius by an insignificant amount.
Will spacers affect the wheel bearing life? Spacers may have some impact on wheel bearing longevity depending on how much further the centerline of the wheel is being pushed out compared to stock. Even in the case of some of the widest spacers the impact we have seen is minimal, in the last 10 years + that we have been doing wheel spacers we have seen no correlation between bearings wearing out on unmodified cars and those using wheel spacers. The rate of wheel bearing replacements as a whole has been extremely low with almost all of those occurrences happening at over 100,000 miles.
Will spacers affect the warranty? In the rare and odd occurrence that a wheel bearing failure happens while under warranty with spacers installed the dealership may be inclined to cite the spacers as the cause of failure if they find that wheel spacers have been used.
Can I test fit spacers and exchange them if needed? Unfortunately once spacers have been fitted we are unable to exchange them.
Can I run different size wheel spacers in the front and rear? Yes. Different size wheel spacers in the front and rear are very common even on AWD vehicles. Often times the front and rear have different requirements for optimal fitment.
Will spacers stop my tires from rubbing the fender lip? Unfortunately not, if your tire is rubbing your vehicle's fender lip the solution will likely be rolled fender lips or other fender modifications, a change to the camber setting of the vehicle or use of a different tire size.
Is an alignment necessary after install of spacers? It is not necessary, however if it has been more than 2 years since the car was aligned last it would be a good idea to do so.