Mushy brakes

[fatire_mtb]

This has puzzled me long enough so I am turning to the good people of NICO who always seem to be able to help me out.

Here's the scoop. I recently replaced my OEM brake rotors and pads and had the lines bled. I followed the bed-in procedure exactly. This was a few months ago now so it's been long enough to know that this is the way it's going to operate and not just a short term glitch. Don't get me wrong, it's not like the brakes don't work, it's just that they are very mushy feeling and do not exactly instill much confidence if I were to have to stand up on them to avoid a bad situation.

I have two working theories. The first is that the material the brake rotor is made out of simply does not create enough friction with the brake pads (Hawk HPS pads) to result in the neck breaking grip the G can provide. The second is that with the rotors being drilled and slotted (and possibly in conjunction with "soft" rotor material) there is less surface area to grab resulting in a softer grip than I would like.

Any ideas and/or feedback would be greatly appreciated. Before I give up on the rotors I thought it would be a good idea to seek out some enlightenment.

Thanks

[C-Kwik]

A mushy pedal would indicate that there is either air in the lines and/or the brake lines are flexing. You stated the lines have been bled so you might rule that out. And even with 4 years on the car, I wouldn't expect the OE brake lines to have any significant flex in them.

I have to wonder if your description is truly accurate. There is a very distinct difference between having a mushy brake pedal and requiring more pedal effort. Also, there is also a big difference between requiring more pedal effort and requiring more pedal movement for a given amount of braking. I think we need a bit more clarity in this regard in order to help diagnose your issue.

[fatire_mtb]

Thanks. After seeing your much better descriptions you definitely stated it better than I did. More pedal movement is required for it to begin grabbing, but even if I engage it to the floor the "bite" is much softer than when it was new.

What can I do to check for brake line flex? I'm ready to investigate/rule out every possibility.

[C-Kwik]

Severe brake line flex can be seen as swelling in the rubber hoses when pressing the brake pedal. Lighter amounts of flex may be harder to detect.

BTW? What kind of brake fluid are you using?

[fatire_mtb]

I'll have to recruit a helper and see if I can detect any brake line flex.

I'm currently using Motul brake fluid.

[C-Kwik]

I'm currently using Motul brake fluid.

Okay, wanted to make sure you weren't working with a silicone based fluid.

Who bled your brakes? If a cheap pressure bleeder was used, it may have forced air into the lines.

The effect is better explained towards the bottom of this page:

http://www.stoptech.com/tech_i...shtml

[tollboothwilley]

I agree with Chano

Sounds like you have air in your brake lines.

Might as well upgrade the brake lines to the steel braided!

haha

Thats one of the things on my list right now. I would say that the rotors being cross drilled/slotted shouldn't change the actual bite.

[Sentientbydesign]

If the rotors were glazed prior to installing the Hawk pads, I can see that being the problem.

The hawk pads worked great the first time I installed them on my I30, after the rotors were turned, they didn't work so well. Subsequent sets of powerslot/HPS brakes never had the same bite. I blame that on improper bed-in and not deglazing the rotors.

[C-Kwik]

I'd agree if the symptoms are that the pedal is firm, but requires more pressure to get the same brake torque as before. If the pedal is actually softer, then something is giving (air, brake line, caliper)