CasperGTI Posted December 29, 2009 Report Share Posted December 29, 2009 (edited) I stumbled accross this gem of information regarding changing the dishes on your bbs wheels, thought it would be good to add in to here for futrue refrence.The rule of thumb seems to be, for every 0.5 inch you add, you subtract your original ET by 6.35mm.This thread will help get you started on building your BBS RM and BBS RS wheels, the two most popular wheels to build.BBS RM:These are two piece wheels with the centers built into the barrel and the lips can be taken off, all RMs are the same as opposed to the RS's. These wheels are as follows: 15x6.5 et33, with the lips being .5". BBS RM on the left, BBS RS on the right.BBS RS:These are three piece wheels, barrel, center, and the lip. These wheels are more complicated then the RMs as there are many different styles that were produced, here is a list of RS's please note that there might be other out there, just make sure to get the right center bore and offsetNOTE: If you wish to change the lips, please keep that in mind as you might run into fitment issues if you get the wrong wheel.RS001 15x7 et25RS002 15x8 et12RS016 15x6.5 et32RS033 15x6.5 et34RS070 15x7 et16 RS071 15x8 et18RS099 15x8 et12RS003 16x7 et25RS004 16x8 et12RS073 16x8 et 13All center bores are 57.1mm the E21 is 57.1mm so they will fit.Spacers can also be used to get the proper stance of the vehicle. Here are the measurements with various size lips. For every .5" you go up on the lips, the ET drops by 6.35mm. Let's take a BBS RS wheel that is 15x6.5 et 34 to use as an example:1.0" = 15x7 et 27.651.5" = 15x7.5 et 21.32.0" = 15x8 et14.952.5" = 15x8.5 et 8.63.0" =15x9 et2.25Torque Spec:BBS RM bolt torque is 12-15 lb/ftBBS RS bolt torque is 12-15 lb/ft Put together the wheels by tighening them by hand using wrenchs (front of the bolt is an 8mm and the nut is a 10mm), then do a cris-cross pattern torquing them down.NOTE: No sealant should applied until after the wheels are torqued. To seal the rim, get any type of all purpose 100% silicone sealant. Start by running a thick bead where the lip meets the center, for RM's its at the front of the "center" and for the RS's its at the front and the back of the center. Once you have your thick bead all the way around, use your finger to smooth it out applying light pressure. Make sure its smooth all the way around and there are no holes. Let it sit for 24hrs. If you are satisfied with your work, your done, but if you want to make sure there are no leaks, you can apply another coat of sealant, but this should be very thin and should be done by putting the sealant on your finger and gently going over the existing sealant.If you want to know what the ET will be when using a spacer, just take the ET of the built wheel and subtract the width of the spacer and that's your ET. For example if you are using a 10mm spacer on a wheel that is ET10, your new ET will be 0 or equivalent.John Edited December 29, 2009 by CasperGTI Link to comment Share on other sites More sharing options...
nayr Posted December 29, 2009 Report Share Posted December 29, 2009 Nice one, very useful Link to comment Share on other sites More sharing options...
Mitchell Posted December 29, 2009 Report Share Posted December 29, 2009 the only thing i will say is you do not need an 8mm spacer for running rm's, i am wondering what car he has based the findings on. the rest is good info Link to comment Share on other sites More sharing options...
Mitchell Posted December 29, 2009 Report Share Posted December 29, 2009 i read it again and he does mention the bmw but only in the rs wheel form, so i'm hazarding a guess the rm is tested on the same bmw platform, Link to comment Share on other sites More sharing options...
CasperGTI Posted December 29, 2009 Author Report Share Posted December 29, 2009 Yeah sorry mitch, that was taken off a BMW forum. Ill edit it and remove the BMW info. Link to comment Share on other sites More sharing options...
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