Audi 100/A6 (C4 92-97) FAQ Digest
01-03-2004, 06:20 AM
#1
AudiWorld Super User
Thread Starter
Audi 100/A6 (C4 92-97) FAQ Digest
Here, how it works:
I have seen, how it works on VW forum. Basically we will put a short articles or links to good posts as replies to this thread. Of course you can upload pictures to the audiworld.com and attach it to your articles. Please follow the structure of the thread.
Also if you are about to type a comprehensive answer, please type it in the FAQ thread and make a link to it. Please do not start flames in the FAQ thread. Thanks
I have seen, how it works on VW forum. Basically we will put a short articles or links to good posts as replies to this thread. Of course you can upload pictures to the audiworld.com and attach it to your articles. Please follow the structure of the thread.
Also if you are about to type a comprehensive answer, please type it in the FAQ thread and make a link to it. Please do not start flames in the FAQ thread. Thanks
01-03-2004, 06:25 AM
#2
AudiWorld Super User
Thread Starter
brakes
you might find a lot of answers about brakes in tech section. our car have same brakes, as A4 and similart to A8. All articles might apply to our cars.
01-03-2004, 06:30 AM
#3
AudiWorld Super User
Thread Starter
brake upgrades
First of all about why you need better brakes.
Brakes convert kinetic energy of the car into heat energy. They can convert only fixed amount of energy per second. The kinetic energy is proportional to the square of the car's velocity. At the same time wheels can apply fixed force to the ground (the dry friction force) independent from the speed. As a result on high speeds during threshold braking wheels will be able to grip even when brakes cannot convert anymore energy (wheels "overpower brakes") and you will need better brakes to improve high speed performance.
On low speed kinetic energy of the car is small and brakes will overpower wheels. As a result you will need better tires to improve braking distance on low speed.
Now If you will drive 80MPH and brake hard at first your wheel will overpower brakes until you will slowdown to ~40MPH after this brakes will overpower wheel. It means, that at this point ABS will kick in or wheel will skid. You can go on some drive safe area and find the magic speed on you own. If you want to improve above this speed - get better brakes. Bellow this speed - get better wheels. Also if you repeatedly threshold brake and overheat brakes, you might want to improve them. In my case I had 195/65/15 AS tires and was happy with stock brakes. Then I put 205/55/16 wheels with summer tires and the magic number slept in 40MPH area (it means, that above 40MPH area I need to improve brakes). So I got better pads and slotted rotors (not like it helped much). Then I put 225/45/17 with S03 tires and magic number slept into 25MPH area. It is horrible. I get A8 rotors on front and plan to put S4 rotors/calipers on back. So far I am really happy with A8 rotors.
The way to get better brakes are:
1. better pads. Ferodo, AXXIS, EBC Green Stuff are good examples. I just put AXXIS and have no complaint so far. Do not go for extreme - racing pads have better fade resistance, but they do not brake when cold.
2. Put slotted and/or cross drilled rotors. You can fins a lot of con/pro for each of approaches. I personally prefer slotted - they help with wet braking and somewhat in brake fade. Of cause the plane rotors can be resurfaced and that is why they can be used twice longer then slotted or xdrilled. xdrilled look nice (but somewhat stupid, because it is not a big red brakes on the sport car).
3. get A8 rotors (see ref for how-to). I did the front and happy with it. Rear calipers are different for 100 and S4 so I am having problems. I think this is reasonable upgrade and it is "proportional" to the price of the old car.
4. SS lines. They suppose to firm up pedal. I installed them and would say, they give minor improvement. Check your lines. If they have any damage and you need to replace them - replace with SS. Otherwise it does not worth it.
5. Replace brake fluid with high quality DOT4. It really might help.
6. If you brake and ABS kicks in, it means, that you have enough brakes and you need to install better tires.<ul><li><a href="https://www.audiworld.com/tech/wheel1.shtml">A8 upgrade instructions</a></li></ul>
Brakes convert kinetic energy of the car into heat energy. They can convert only fixed amount of energy per second. The kinetic energy is proportional to the square of the car's velocity. At the same time wheels can apply fixed force to the ground (the dry friction force) independent from the speed. As a result on high speeds during threshold braking wheels will be able to grip even when brakes cannot convert anymore energy (wheels "overpower brakes") and you will need better brakes to improve high speed performance.
On low speed kinetic energy of the car is small and brakes will overpower wheels. As a result you will need better tires to improve braking distance on low speed.
Now If you will drive 80MPH and brake hard at first your wheel will overpower brakes until you will slowdown to ~40MPH after this brakes will overpower wheel. It means, that at this point ABS will kick in or wheel will skid. You can go on some drive safe area and find the magic speed on you own. If you want to improve above this speed - get better brakes. Bellow this speed - get better wheels. Also if you repeatedly threshold brake and overheat brakes, you might want to improve them. In my case I had 195/65/15 AS tires and was happy with stock brakes. Then I put 205/55/16 wheels with summer tires and the magic number slept in 40MPH area (it means, that above 40MPH area I need to improve brakes). So I got better pads and slotted rotors (not like it helped much). Then I put 225/45/17 with S03 tires and magic number slept into 25MPH area. It is horrible. I get A8 rotors on front and plan to put S4 rotors/calipers on back. So far I am really happy with A8 rotors.
The way to get better brakes are:
1. better pads. Ferodo, AXXIS, EBC Green Stuff are good examples. I just put AXXIS and have no complaint so far. Do not go for extreme - racing pads have better fade resistance, but they do not brake when cold.
2. Put slotted and/or cross drilled rotors. You can fins a lot of con/pro for each of approaches. I personally prefer slotted - they help with wet braking and somewhat in brake fade. Of cause the plane rotors can be resurfaced and that is why they can be used twice longer then slotted or xdrilled. xdrilled look nice (but somewhat stupid, because it is not a big red brakes on the sport car).
3. get A8 rotors (see ref for how-to). I did the front and happy with it. Rear calipers are different for 100 and S4 so I am having problems. I think this is reasonable upgrade and it is "proportional" to the price of the old car.
4. SS lines. They suppose to firm up pedal. I installed them and would say, they give minor improvement. Check your lines. If they have any damage and you need to replace them - replace with SS. Otherwise it does not worth it.
5. Replace brake fluid with high quality DOT4. It really might help.
6. If you brake and ABS kicks in, it means, that you have enough brakes and you need to install better tires.<ul><li><a href="https://www.audiworld.com/tech/wheel1.shtml">A8 upgrade instructions</a></li></ul>
01-03-2004, 06:42 AM
#7
AudiWorld Super User
Thread Starter
original wheel sizes and compatable rims
A6 had the following:
tires are 195/65/15
rims 15x7" with ET45 offset.
bolt pattern is 5x112. the lugs diameter is 14mm.
Another important number is the center bore size.
Basically Merc has the same bolt pattern, but different lug diameter (12mm) and bigger bore as a result you need Merc's lugs and even then the wheel will rest on bolts not on the center bore, so you should use some adaptor ring.
In general you should look for wheel, made for Audis (except TT - TT has 100x5 bolt pattern) and for VW Passats (again, all others have different bolt pattern).
tires are 195/65/15
rims 15x7" with ET45 offset.
bolt pattern is 5x112. the lugs diameter is 14mm.
Another important number is the center bore size.
Basically Merc has the same bolt pattern, but different lug diameter (12mm) and bigger bore as a result you need Merc's lugs and even then the wheel will rest on bolts not on the center bore, so you should use some adaptor ring.
In general you should look for wheel, made for Audis (except TT - TT has 100x5 bolt pattern) and for VW Passats (again, all others have different bolt pattern).
