Braking Imbalance?

[zeroping]

In June I purchased and installed Tony's rear caliper upgrade. The kit came with the conversion brackets, pads (Power Stop Z23-1417), and pad retaining clips. He also provided front/rear braided steel brake lines. I installed the kit and the brake lines on the rear only and flushed fluid. I planned to install front lines when it was time to service the front brakes which still had plenty of thickness all around.

Fast forward a month and I do a track day at Limerock completely roasting the rear pads requiring a complete overhaul including rotors. I stick with OE rotors (34212284903 & 34212284904) but go with Textar (TEX-2455402) instead of pads originally supplied with Tony's kit.

Fast forward 10k miles and the rear pad material is low again - within the next few thousand miles I will need to service them.

Can someone wiser then me confirm that I'm doing myself a disservice by having OE brakes line on the front but upgraded on the rear? It would seem the rear is doing the heavy lifting here. Would that be accurate? The truck stops on a dime and if the rear is doing most of the work I can't feel it.

[Yuille36]

I think that your track day, was the major contributing factor to your brake wear issue. However, steel braided lines do apply more pressure to the calipers, as they have less flex then plain old rubber hoses. Also everyday pads, do not hold up to track abuse. I have Power Stop braided lines on my X5M and E63 AMG, and I absolutely love them. And I run PowerStop Carbon Ceramic pads on both my vehicles, but I wouldn't do a track day with them. As, they wouldn't hold up to the abuse, get a dedicated track pad. I do think that your brake balance is off, as the front calipers should do 60-70% of the work.

[dentprotony@gmail.com]

Typically front brakes do around 60-70% of work on most vehicles. I would recommend specific track pad for track, textars are great for daily, but are soft to an extent especially for severe use. I would recommend proper brakes/pad cooling after each track application, but definitely look into proper pad for what you are doing, i doubt brake lines would be the culprit in this.

[zeroping]

I appreciate the responses but they tend to focus on my single track day to date and not general driving. To confirm, I went through a set of rears on a track day. All good there...you gotta pay to play.

But since that single track day I completely overhauled the rear brakes only to have the rear pads down to 15% material after ~10k of street driving only.

[V i C]

believe it or not, rear brakes play a role in this level of cars in braking in general applications - not track per se. my rear brakes wear out quicker in my cars when i'm using them as daily drivers than you'd think. i've been told because the brake applies to make the stop smoother. i'm buying what they're saying for now.

just to be clear here, i'm not saying rear brakes provide the majority of stopping power. i'm saying the electronics apply more rear brake than we think during daily driving as it makes for a more comfortable stop; massive front brakes are grabby, they lead to jerking movements

anyway, that's my experience daily driving these kinds of vehicles - not so much in my x5m, as that is new to me. but in my mercs that's what's happened. early rear brake changes.

furthermore, on my w205 c63, when it needed brakes, it was the rear ones that were down past the endplate, and making a grinding noise. and that's when i really noticed what MB was telling me all these years. as i was coming to a stop in daily city driving, the rear brakes would start grinding noises. they were applying pressure.

i'm also not saying your rear brakes should go in 10k. just something to put out there.

[Yuille36]

As far as the AMG's go, if you don't have a LSD, the rear brakes will engage to keep the tires from spinning, unless you turn off traction control.

[dentprotony@gmail.com]

Id say try a different pad and install front braided lines, this might change thing maybe.

[Cbozz]

Originally Posted by zeroping

I appreciate the responses but they tend to focus on my single track day to date and not general driving. To confirm, I went through a set of rears on a track day. All good there...you gotta pay to play.

But since that single track day I completely overhauled the rear brakes only to have the rear pads down to 15% material after ~10k of street driving only.

So the Porsche rear caliper pistons are 32mm x2 per side. Long story short they are in a ballpark of 18% larger piston surface compared to oem rear brake piston surface area. That makes the brake bias shift to the rear making it brake more than it should… that was the major reason why I opted out and went with Brembo calipers that are 28mm and 30mm making it 4% smaller than oem.
Yes they are not 1:1 ratio and brake bias is shifted to the front but my tolerance is a lot tighter and way closer to oem size than Porsche.
I think that could be a factor why your pads go out so quickly especially when you track it.

[shimmy23]

believe it or not brake bias is a huge deal if you are tracking your car. street driving you can mix and match these bigger calipers and not "feel" the impact as much. if you are tracking your car i'd highly recommmend doing the calcs or seek someone that has the knowledge to do so. stopping faster doesn't always equal better if that make sense.