Upgrades and Enhancements
Here are some options for upgrading your brake pads:
You can get cross-drilled or slotted rotors from many vendors. Here are a few:
The 90Q20V has weird front brakes. The rotors are 256mm like the regular 90, but it is NOT the same rotor! The offset is different. Because the demand for these special rotors is low, it's tough to find replacements, and the dealer will charge $120 -- $140 EACH! The Audi P/N is 893 615 301A.
The overall diameter of the "small" rotors is 256mm as opposed to 276mm (found on the Coupes) and the center hole is 68mm with a 30mm "tophat" (offset from the rotor face). The portion between the rotor face and top hat is NOT vented in the joint. I'm including this info because most of the books on the car are WRONG or confusing at best. Best Price in Ottawa Canada (800-636-0854) carries high quality rotors (blank, drilled or slotted for an extra fee) that will fit this car for around $120 per pair. Ask for P/N EUR #AU258. IMPEX (800-736-3550) also carries suitable rotors. They use the Audi P/N.
See below for details about upgrading the 90Q20V to the 276mm rotors and G60 calipers that came stock on the CQ.
Most of the usual Audi-specific vendors offer "big brake" upgrade kits. Some use a larger Porsche (Brembo) caliper, others use aftermarket calipers. There are lots of options, and you're only limited by your wheel size and your budget. Beware that the calipers in some kits are designed for racing applications, and may require frequent rebuilds. For the 90Q20V, see below for a relatively easy conversion to the larger G60 brakes that came stock on the CQ.
G60 Upgrade for the 90Q20V
(Sean Douglas, Ray Tomlinson, Mike Benno, Bob D'Amato)
The sedan came with 256 mm rotors and a single piston caliper as stock. The 20V sedan front brakes can be quite easily upgraded to the Girling 60 (G60) dual piston calipers and 276 mm rotors similar to those of the CQ. You must upgrade to at least 15" wheels, as the G60s will not fit within a 14" wheel. The Euro-spec 20V sedan came with the G60s as stock, which makes this upgrade easier. If your stock brakes are in need of replacing, its a worthwhile investment as the 256 mm rotors for the 20V sedan are unique and expensive. Having said that, the 276 mm rotors required for the sedan are different from the CQ because the offset is different. They are available in North America as long as you quote the right p/n. TPC is a good source for these.
The following assumes that you can get a used set of G60 calipers and carriers for a decent price and you are willing to rebuild them. Bead blasting and painting is optional and adds about a day's work, but the end result is worthwhile if you are concerned about appearance.
* G60s from a CQ are preferable. The caliper is mounted on the leading edge of the rotor on the 5K/200 but on the trailing edge on the CQ/90Q. The piston orientation in the caliper is reversed in these two applications, so if you use the 5K/200 caliper, the leading piston (in the direction of rotation) will be the larger one, rather than the smaller one. It is unclear if this will present any problems for caliper operation, so proceed at your own risk if you opt for the more common 5K/200 calipers. Also, there an issue with the placement of the brake line fitting. Double check the length of brake line to make sure it will reach comfortably.
** Kevlar-carbon pads made by Kerr Friction. These do not come with the anti-rattle clips as per OE.
Depending on the build date of your car, you may already have two flex brake hoses up front. If you have two flex hoses up front, you DO NOT need to buy new brake hoses. If you have an early build date, with a single flex hose, you will need a longer hose (405 mm long) from 5KTQ p/n 443 611 707C (2 required). These are expensive, list is $92 ea.
If you need new lines for you late build date sedan, the part numbers are as follows (its a good idea to replace these while you have everything apart anyway):
The brake master cylinder is slightly larger on the Coupe, so you might want to upgrade it. However, several have done the switch without changing the master cylinder, so it's not really necessary.
Prepping the G60's:
Remove existing pistons by blowing air into the old brake line or the bleeder valve. Block one piston (larger), and remove the un-blocked (smaller) piston nearly all the way, but not totally out. Then block the smaller piston, and blow out the larger. Be sure to hold back the pistons with a loose c-clamp as they could suddenly pop out and fall, potentially damaging them.
Remove the dust boots with your fingers, and gently pry out the inner seal with a small screwdriver or a pick. Remove bleeder screw and old brake line, and you are ready for bead blasting, or aluminum oxide (recommended for brake parts by a mechanic).
Blast everything, including the bores. You will not hurt the caliper. You can also mask the pistons, and blast the edge that touches the pad and is exposed by the dust boot. There can be some rust buildup on this part. Be careful not to blast the piston surface itself.
Be sure to blast inside the piston bores, but tape off before painting. Once blasted, give a good wash with plain water (to remove all traces of sand, etc.), then a good cleaning with brake cleaner, followed by two cleanings with DT870 automotive reducer. This helps to clean the surface, and actually seals it before painting, apparently. You must paint immediately after cleaning, as the calipers and bores will begin to rust if left exposed to humidity or any air moisture.
Remove any traces of overspray from the bores with steel wool and clean up the pistons. Its a good idea to check if the piston slides freely in/out of the bores before installing the seal. Bentley describes the installation of the pistons (47.11). Insert the ring seal into the lower groove of each bore. Slide the dust boot over the piston in correct orientation as pictured. Leave about 1/4" overhanging the end of the piston. Lubricate the piston and bore with brake cylinder paste. Install inner lip of dust boot into upper groove of bore and push the piston in. Press firmly until the piston contacts the seal. Use a large c-clamp to push the piston all the way in until the outer lip of the dust boot seats into the groove on the piston. Make sure the piston is aligned squarely before tightening the c-clamp! Otherwise you will jam the piston in the bore and it will be a PITA to get out!
Installing the G60 is basically the same procedure as replacing the pads and rotors. Refer to Bentley on this if you are not sure. The only exception is that you will have to crack open the brake line and attach to the G60s. Use a flared wrench to undo the fittings and make sure that the brake line is not twisted. As you have opened the hydraulic system, you will need to bleed the system. As always with new pads, make sure you seat them by using your brakes lightly for the first 100 miles to avoid glazing them.
Stainless Steel Brake Lines
Stainless steel brake lines don't expand under pressure, so you'll get better pedal feel.
See also: Brake Maintenance, Brake & Hydraulic Problems
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