So I did the brakes this past Saturday: Carbotech pads, rotors, and RBF600 fluid. Bed-in as per TSW's instructions (multiple 80-30mph slowdowns). Car does seem to brake better – ABS more intrusive for instance – but the pedal is really soft. To get the brakes working in earnest requires the brake pedal about level / a little lower than the gas pedal.

This is more travel than before, although my biggest complaint with all stock components was the amount of travel also.

I've bled 3 times now at all four corners (gravity bleeding). It's all new fluid with no air bubbles. What gives? Is all of this indicating a bigger problem, like a brake component on the way out? What causes a soft pedal other than bad / air-bubbley fluid?

I was hoping for better initial bite / braking and I've gotten the exact opposite.

TIA

 

There could be a small amount of air stuck in the ABS controller which means . Other than that, a hose could bad. It could have swelled and blown outward. Maybe an internal leak in the master cylinder. Honestly have no definite here.

 

Could also have a bad caliper. Just had another customer with the same type of issues and once the caliper found (rear) and rebuilt/replaced the issue was resolved. Hope that helps.

 

I don't think you can get better bite than stock (soft rotors and pads) without a BBK. SS lines will get you marginally stiffer pedal, but overall your set-up probably needs higher pedal force for the same stopping power. That's why the pedal feels softer.

 

His pads (Bobcats) and rotors (TSW) are not soft. I run the same setup on stock lines and have a nice high firm pedal. The rear calipers will go bad due to the e-brake parts, that's the 1st place I'd check.

 

I'm pretty definitely sure that there is some sort of problem here, and considering how straight forward brake work is, I don't think it's on my end.

I did notice a tear in a rear caliper boot, assumed I did it with the screwdriver while popping out the wheel sensor. Piston was working fine though. Also missing the bleeder valve rubber caps in the rear, picking up replacements, but that couldn't have anything to do with this.

Might take it to the dealer to diagnose. Not the most "mod-friendly" people.

Will mention the above suggestions! Any other potential solutions?

 

Fully agree - the stock pads and rotors are softer than the Bobcat/TSW, which is why the initial bite is better with the stock parts. I'm sure heat fade is better with the aftermarket set-up, though.

Of course, he could have a bad caliper, but I'd expect there would be a pull to one side in that case. To have both rears or both fronts go bad at the same instant seems kind of unlikely.

 

pump the pedal and bleed them. start with the wheel farthest from the master cyclindar. i just did the same thing about to mounths ago to 2 mini's one i got frist time the second i had to do again. they mini mechinic i talked to said that you do not want to miss with the abs, and that the chances of getting bubbles there is slim. how ever you can get them on the clutch pedal the share the master cyclindar but even the is not likely. do you still have the rubber thing that the breaks ride on or did you up grade them?

 

The CT Bobcat pads have a MUCH higher CF than stock pads, and are ceramic, so much less prone to brake fade. Pedal squishyness has nothing to do with the pads being soft, hard or anything in between. I suspect air in the lines. Are you sure you properly bled the system?

 

Hey Rusty, we can get you CT pads for your Wilwoods too. Just drop me a PM for the details.

 

Yea, I remember reading about it a few months ago. The kit came with pads, but when I need new ones I'll be sticking some Panther's in for the street I think.

 

He says he only "gravity" bled them which sounds like he was working alone. To get them bled properly when you don't have some help you need a Mity-vac or something similar to create a vacuum to pull the air out. Either that or get someone to pump them for you............sounds like air in the lines to me.

 

Ya, that'd do it --^.

 

According to the Bentley manual it is either a faulty master cylinder, a faulty traction control module or air in the fluid. Going by what I know this sounds like air in the fluid.

Look at it this way, at least you cant push you brake pedal all the way to the floor like I can...

 

+7 Air, bleed with someone helping...
Pump, pump, pump ... Hold, Crack the line till the peddle hits the floor, tighten.. Replete

 

K, I mispoke earlier. I was having someone help by holding the brakes. After doing a bit of googling, I've gone out and bled again. That's about 4x and I've gone through a liter of RBF600. Too expensive for this monkeying around.

I'm not getting any bubbles at this point and am PO'd, so I'm breaking down and taking it to a place today.

 

The perception of pedal squishiness indeed has a lot to do with the CoF between rotor and pad. Agreed, the pedal is not truly more squishy with the higher performance rotor & pad, but because this set-up likely needs greater pedal force than stock for the same braking power, it seems squishier. I experienced the same thing as the OP when I switched from stock to TSW rotors/Hawk HPS. Without even bleeding the brakes (no possibility of air entrapment) I had to press harder to get the same braking power, which brought the brake pedal below the gas pedal for decent stopping. Not good for heel-toe. Brake bleeding did not help, but SS lines did, as well as simply more time for additional break-in.

I'm wondering how you know the CT - TSW combo has greater CoF than stock. CoF for brakes is not a simple one-number thing -- it depends at least on temp and pressure. OEM brakes, and MINI is no exception, tend to be optimized for high CoF at low temp/press, at the expense of higher temp/press performance.

I'm betting the OP will get the car back from service unimproved wrt pedal feel.

 

How much are we betting? The cost for service?

 

if you gravity bleed ABS it is very difficult to get all he air out of the pressure manifold and lines. I find gravity works best for non ABS cars.

I would get a pressure bleeder from harbor freight or something.

 

Verdict is... I wasn't getting all the air myself despite the lines appearing free o' bubbles. Local shop redid, found air, and it's better than before doing the work / bleeding myself. Lesson learned. Cheap one too - glad I didn't end up taking to the dealer.

I'm inclined to agree with you, inimmini, but I think your point can really vary from pad to pad. The Carbotech Bobcats aren't requiring more effort than the stockers do (from what I remember) and are significantly better, although in an ideal world I'd like more linearity and less travel to get them biting more. Although it's just about perfect for heel-toeing now, unless you're really mashing the brake...

Thumbs up for the brake combo, thumbs down for nooby topics.

 

I feel compelled to comment. Seeing that all MINIs have ABS the statement above is somewhat mis leading.

There is no harm in a simple gravity bleed on any car. ABS or not. I've done more than a share of MINIs and others fully solo. The issue here is that the mc reservoir must not be allowed to run dry and thus induce any air to the ABS system. In that case there can be a need for some further "high tech" work. However from many year of brake service I can say with certainty that no brake system will fully drain itself of fluid in any panic time manner. Servicing one end of the car at a time (please don't get me started on proper order- for a simple bleed it does not matter) you have ample time to allow fluid to flow freely for many minutes before you'll see any significant drop in the reservoir level.

Simply keeping the reservoir topped up with fresh fluid will insure a smooth transition from old fluid to new without any issues to ABS systems.

 

i am glad that you got your breaks sorted out.

 

The haynes manual may be incorrect, but it states that the mini's brakes are self bleeding. Now obviously if you have a crap load of air in there, the brakes won't even work...and you need to bleed the system to change fluid and move the large amounts of air, but if there is just a little bit and there is just a little more pedal travel, it should get better over a couple of days. I guess the way the system is set up, pumping the brakes should cause the small amount of air to rise through the system and eventually into the reservoir. I do know that the clutch system works this way. If there is a little bit of air, it gets better over a couple of days or a lot of pumping.

 

The haynes manual may be incorrect, but it states that the mini's brakes are self bleeding.

An interesting statement. And I'm reasonably certain that it refers to the basic gravity bleed where simply opening a caliper will purge said caliper of air as the bleeder nipple is higher than the inlet port. However pumping a brake system while the nipple is open is asking for problems...as the pedal is released and brought up the vacuum in the system will draw air back INTO the caliper thus requiring the whole process be done all over.

There remains absolutely NO reason for air to be in an ABS system or any part of the braking system other than bad procedures being employed. Even replacing a hose is no differet than changing the hose on a beer bong- the beer is flowing and so long as the funnel is full it's not going to stop and air is not going up. Connect the new hose, fill the caliper, keep the reservoir (the beer funnel) full and there shall remain no air in your system.

Bleeding is not about pressure, it's only displacement. Some procedures make it appear far more complex than it really is.

 

I'm happy to see that you have worked it out. As far as brake "feel" the higher performance pads will feel different then the OEM or your local parts store pads. I do think you will find what I found after a few days, I have a much better "feel" in braking and have learned where the "bite curve" is on the Bobcats and when I want to stop short or hard they will but it takes a few miles to learn where that bite curve is. I look forward to your thoughts after a few more days of use.