THE END RESULT:

Now the caliper sits dead-center over the rotor, as it should, using our RotorLab-engineered bolt kit. Problem solved.

Now that the offset has been corrected, we do all the 'gussy-up work' to make them look fantastic, and give your car that motorsport look and bigtime braking power increase...and now the whole conversion is a bolt-on job.

Mount 'em up, hook up your brake lines, bleed the system and away you go.

THE MODIFICATION:  

Here you can see the machine work done on the 2 tabs. This is the right way to do the job. The mounting will be true and solid, and dead parallel with the rotor, as it is supposed to be.

And our bolt kit is already engineered to work with this...the bolts and sleeves are the right length for the new tab thickness. We've done all the engineering for you.

THE ANSWER:

Mill a specific amount off the inner contact surface of the mounting tabs. DO NOT just try and 'grind this off the mounting tabs yourself at home with your die grinder', folks...you will NEVER get it perfectly flat and parallel with the rotor, which means poor contact...which actually IS dangerous. 

We've had 2 people already called us after the fact who did this and messed their calipers up...we had to do custom machinework for them to fix it....and it was not cheap.

And absolutely DO NOT make the mistake, like some folks have, of trying to grind down your factory strut towers. You will never get those perfectly flat, either, and you just destroyed a set of strut towers, which will cost big bucks to replace, plus now you'll have to pay for a front-end alignment to put the specs back. Big mistake.

HERE'S THE PROCESS AND WHY:

THE PROBLEM: 

Here's a pic of the unmodified 18Z caliper mounted to the strut tower on B6/B7 S4 OE 345mm rotors. (Doesn't matter whether it's on a B6/B7, or B5...same issue....the strut tower tab orientation is the same) When the rotor is mounted on the hub, and an unmodified caliper is bolted to the upright (the strut tower), the offset is way off----the caliper strikes the rotor.

That ain't gonna work. Same situation for Mk5 or Mk6 GTI or GLI, when using these rotors, which are by far the most cost-effective of the options out there. 

The 18Z calipers are a near-bolt-on job for the B5 A4 and S4, the B6/B7 Audi A4Q and C5 Audi Allroad.....as well as the Mk5 and Mk6 VW GTI and GLI. This is because of the distance between the bolt holes. However, the offset must be modified if you are going to use the OE 345mm B6/B7 S4 rotors...which are an excellent and affordable route go, especially using our RotorLab rotors. So what do you do? Well we have a program to modify the mounting tabs, which makes this possible.

What this does is center the caliper directly over the rotor. There is still plenty of 'meat' left on those mounting tabs to ensure a strong and reliable mounting point to the strut towers. This basically makes the entire conversion a "bolt-on " job...meaning no special tools or other mods necessary. See the pictures below. 

This mod costs us 60 dollars....we here do not charge you any more than what it costs us, which is this same 60 dollars. We figure we shouldn't be charging you for work that we ourselves aren't actually doing, other than just dropping off the calipers and picking them back up. This mod, combined with our B6/B7 S4 345mm RotorLab custom crossdrilled rotors, will STILL end up being dramatically cheaper than buying the custom-offset 2-piece rotors available for purchase from several different retail sellers out there (those are typically about $700), making their "kit" run in the $1700 to $2000 dollar range......far higher than ours.