Not happy with stock brakes

[Twixboy]

I've been driving my 2004 Z4 3.0i for a few months now and don't like the feel of the OEM brakes. The initial bite is almost as bad as my pickup truck and the pedal feels mushy even after I got the brake fluid flushed. My Audi Q5 which is almost 50% heavier seems to stop much better than the Z4. There's 58k on the clock and the original owner already replaced the pads once at the dealer at around 30k. Is it time for new pads/rotors or should I just go for a brake upgrade?

The OEM front rotors are 300x22 mm. If I do a brake upgrade I was thinking of going up in size to either the 3.0si (325x25 mm) or M rotors (345x28 mm) - would they be a direct fit? I'm guessing I'd need the 3.0si or M calipers too if I go that route. Are there any companies that make larger rotors that allow me to keep my stock calipers? I'm not looking to spend thousands on a BBK, I just want a little better braking performance for street use.

[seank]

Originally Posted by Twixboy

I've been driving my 2004 Z4 3.0i for a few months now and don't like the feel of the OEM brakes. The initial bite is almost as bad as my pickup truck and the pedal feels mushy even after I got the brake fluid flushed. My Audi Q5 which is almost 50% heavier seems to stop much better than the Z4. There's 58k on the clock and the original owner already replaced the pads once at the dealer at around 30k. Is it time for new pads/rotors or should I just go for a brake upgrade?

The OEM front rotors are 300x22 mm. If I do a brake upgrade I was thinking of going up in size to either the 3.0si (325x25 mm) or M rotors (345x28 mm) - would they be a direct fit? I'm guessing I'd need the 3.0si or M calipers too if I go that route. Are there any companies that make larger rotors that allow me to keep my stock calipers? I'm not looking to spend thousands on a BBK, I just want a little better braking performance for street use.

I dont know your audi but every Bmw that i own or have driven had sufficient stopping power. I would check the fluid, change brake pads, and possibly look into a brake booster upgrade before changing the brakes. Since your z4 is tons lighter, you dont need much force to have equal to better stopping power than a heavy Audi.

[TexasZed4MC]

I agree with seank, better pads and new fluids should help also adding stainless braided brake lines replacing the stock rubber ones will help a great deal also

[Twixboy]

I just got new fluids, so I think the problem may be the OEM pads. They've gone 30k miles in 7 years, so its very possible they just aren't as good as they were when new. What's a brake booster?

[seank]

Originally Posted by Twixboy

I just got new fluids, so I think the problem may be the OEM pads. They've gone 30k miles in 7 years, so its very possible they just aren't as good as they were when new. What's a brake booster?

The brake master cylinder is what i meant. It is attached to the brake booster. It moves the fluid. A larger master cylinder will make the pedal firmer and less movement for the braking force. Common upgrade on a track car. I dont see an upgrade for the e46 m3, but ours could be an upgrade to you.

[dc_wright]

Originally Posted by Twixboy

The OEM front rotors are 300x22 mm. If I do a brake upgrade I was thinking of going up in size to either the 3.0si (325x25 mm) or M rotors (345x28 mm) - would they be a direct fit? I'm guessing I'd need the 3.0si or M calipers too if I go that route. Are there any companies that make larger rotors that allow me to keep my stock calipers? I'm not looking to spend thousands on a BBK, I just want a little better braking performance for street use.

When you increase the rotor diameter at a minimum the calipers have to move out to accommodate the larger diameter. In this case you're wanting to use both larger diameter and thicker rotors so you'd need the rotor, caliper, and caliper carrier. The 3.0i and 3.0si use the same front spindle castings so the si brakes should fit. The Z4M uses the front suspension from the E36M3 and all of the parts are different so fitting those brakes without custom fabrication is unlikely.
WRT to the Audi vs. the Z4 have you actually found a lonely road and done a stopping distance comparison? That's really to only way to compare legitimately, feel can be a poor indicator. In the late '60s, early '70s Ford launched an updated body style Lincoln Continental. Test reviewers universally faulted the poor brakes. Ford put softer springs in the front along with shocks with greatly reduced compression damping shocks. When you hit the brakes the nose of the car dropped 6-8 inches. They did subjective comparison tests between the two versions and the reviewers rated the updated car significantly better WRT braking. In reality the stopping distance hadn't changed one bit.

[Twixboy]

Originally Posted by dc_wright

When you increase the rotor diameter at a minimum the calipers have to move out to accommodate the larger diameter. In this case you're wanting to use both larger diameter and thicker rotors so you'd need the rotor, caliper, and caliper carrier. The 3.0i and 3.0si use the same front spindle castings so the si brakes should fit. The Z4M uses the front suspension from the E36M3 and all of the parts are different so fitting those brakes without custom fabrication is unlikely.
WRT to the Audi vs. the Z4 have you actually found a lonely road and done a stopping distance comparison? That's really to only way to compare legitimately, feel can be a poor indicator. In the late '60s, early '70s Ford launched an updated body style Lincoln Continental. Test reviewers universally faulted the poor brakes. Ford put softer springs in the front along with shocks with greatly reduced compression damping shocks. When you hit the brakes the nose of the car dropped 6-8 inches. They did subjective comparison tests between the two versions and the reviewers rated the updated car significantly better WRT braking. In reality the stopping distance hadn't changed one bit.

Thanks, so if I can find aftermarket rotors/pads for the 3.0si they should fit my 3.0i right?

Shouldn't the larger rotors on the 3.0si in theory give it better braking than the 3.0i? I looked up car and driver's stats and both models had an identical 158 ft braking distance from 70 to 0 mph. That's also with the 3.0si having a few hundred pound weight advantage.