MINI Brake Problem- Need Help

[PinkLinc]

Hi Guys- I was doing a rear brake job on my MINI and noticed on the right rear, the pads were unevenly worn. Not the inside pad compared to the outside pad, but the top of it compared to the bottom. To further explain this... the remaining friction material was wedge shaped. The right rotor was also significantly thinner from wear than the left rotor.

I figured it was the caliper that was bad so I replaced it with a rebuilt unit from NAPA, bled the system, reset the parking brake adjustment and it's still super tight. Everything was properly greased and torqued to spec. Any thoughts here? Master cylinder? Traction control? ABS? Can those components be tested? I'm at the end of my knowledge and ability here.

 

[bd8134]

Wheel bearing worn allowing the disc to tilt?
The rear disc is held in place by a screw but maybe wheel bolts loose allowing disc to tilt, less likely?
Bent caliper mounting bracket or stuck caliper piston?
If you look straight on at the edge of the disc, caliper and pads does it all look straight now?
Traction control would be just on the driven/front wheels.
You might have stability control but that would just apply the brakes as needed, just like you had used the foot pedal, same as ABS.

 

[wess23]

Maybe I missed it but did you check to see if the rotor is warped?

 

[geotek]

Fellow MINI owner: any mods? Slotted rotors, performance brakes, etc? Sounds like something didn't seat correctly or is miss aligned. I'm not sure if your a member but consider checking out North American Motoring for help. www.northamericanmotoring.com if someone there hasn't already posted the answer or doesnt have the answer then it's not answerable. Also not sure what you paid at NAPA for rebuilt calipers but consider pricing at British Atlantic Ltd. They actually supply my local dealer with parts so I go directly to them (plus they are just down the street )Good luck.

http://www.northamericanmotoring.co...ms-issues/165670-brake-pad-wear-question.html

 

[blasto9000]

Post pics... the "top" and "bottom" of the pad is not a very good descriptive term, depending on which way the calipers are oriented... which will be different from right to left. Also seeing the direction of brake pad wear will be helpful, especially if it's not symmetrical.

 

[PinkLinc]

As far as I can tell nothing is bent. It all looks straight. The rotors are new German made Zimmermans. That wheel bearing was replaced about 40,000 miles ago with a new SKF unit and seems fine. I actually disassembled everything down to the point where I took the wheel bearing off to make sure everything was straight, in good working order and torqued correctly. I can't post pics of the old pads because I threw them out but to further explain the wear, on one side, the portion of the pad closer to the center of rotation is thin while the portion further from the center of rotation is thicker. The opposing bad was the opposite. Hope that makes sense.

I was a member at North American Motoring a long time ago but haven't been on there in a while. Maybe I'll check it out again.

 

[PinkLinc]

Fellow MINI owner: any mods?

15% reduction pulley, Ported Supercharger, Koni adjustable dampers, Hotchkis lowering springs, Hotchkis rear control arms, Polyurethane lower control arm bushings on the front.

 

[bd8134]

Has the car been in an accident?
Is the tire wear uneven?
Did a new caliper mounting bracket come with the replacement caliper?
Maybe check the pads after a few days to see if they are still wearing uneven.

 

[jjjrmx5]

Check your slider pins on each aliper/carrier and make shure they slide free adn are using the PROPER lube.

Sometimes the boots rip allowing water and corrosives to get in there and wash away the lube and rust out the pins.

The pins are ther to make sure teh caplier floats evenly on the carrier thus compressing teh pasd evenly on both sides. If a pins slows or seizes, the caliper coks and you get abnormal wear depending upon which pin or no wear if they seize and render the calper useless. I see 5 x the amt of buggered pins compared to bad calipers.

Also use the right lube. Not typ. silver antiseize, but the blue or clear slider pin lude made for the hight heat. Typ. silver anti-seize can;t take the brake heat range.

 

[Boomer343]

Your original tapered wear on the pads was from the slides binding causing the caliper to tilt. Then because of the binding the caliper can't move back. Common on rear disc brakes as they seldom get serviced and are more complicated than front calipers.

Do these calipers have the caliper piston that screws in/out as part of the hand brake mechanism? If they are then my experience with reman units was to check the rebuild very carefully and ensure before mounting that the piston could be screwed in and out smoothly and completely. Also again if this is the case make sure the pins on the back of the pads line up properly with the slots in the piston, if there was too big of gap between the piston and the pad and the disc when you were doing the assembly then when you pushed the pedal for the first time the piston moves past the pin and causes the over tightened condition.

Hope this helps....made a lot of money off GM and Honda rear disc brakes.....

 

[Jagmandave]

Also make sure you have the pads installed correctly....the piston side pad has clips that are supposed slip over a groove in the piston, if you don't get thse installed right it can hold the pad at an angle and cause it to bind.

Also make sure the slide pins are cleaned, and as the other poster said that the em brake parts are working correctly.

 

[PinkLinc]

No accidents. Even tire wear. Thanks guys but everything mentioned has been checked and re-checked. New pins came with the rebuilt caliper, properly greased, correctly installed. I've done plenty of rear brake jobs in my day with no problems. What I don't understand is the new parts are doing exactly the same sh!t as the old parts which makes me think it's something else. My manual says this condition could be due to a failure of some sort in the master cylinder but I have no way of checking that. I guess a trip to a proper MINI tech is in order. $$$$$$$$$$... UGH!!!

I appreciate all the responses. I'll update when I get this sorted.

 

[Boomer343]

Would not be unusual to get a poor reman caliper.....I would do an exchange with NAPA.

They have heard this story before.....

 

[c39er]

Flex hose to this caliper plugged causing the dragging situation?

 

[vegar]

The rear calipers are a common problem on MINIs, and other small cars with rear disc brakes. The problem is basicaly that it is not necesary with rear discs during normal use. They will not be used enough during the putting around to the store and work, so will be rusted/binded after a couple of years.

Only way to make sure this doesent happen is to replace calipers and use the car as it was designed to, trackdays

 

[PinkLinc]

This is probably a stupid question but it's the only thing I can think of at this point before I take it to a shop. The banjo bolt that connects the flex hose to the caliper called for something like 35 ft. lbs. of torque but when my wrench clicked, the hole in the bolt that lets the brake fluid flow through it wasn't even close to lining up with the hose. I had to turn that bolt another 90 degrees to get those to line up.

Are there any issues there? Is that hole not supposed to line up with the hose for some reason? The manual didn't say anything about lining those 2 things up but it seems like common sense to do so.

 

[bd8134]

Inside the brake hose itself is a relief for the brake fluid to pass all around the banjo bolt, ie it does not matter what direction the hole in the bolt faces.

 

[Jagmandave]

Not line up how?

Banjo fittings typically are large enough that the liquid can flow around the bolt, regardless of where the hole is pointing, the liquid then flows thru the center of the bolt and into the caliper or whatever. The only location needed is that the holes in the sides of the bolt are in the center portion of the banjo fitting.

Edit: BD types faster than me....

 

[bd8134]

I dont see how a master cylinder can cause a brake pad to be tilted. It only has the ability to apply pressure or release it. So if you had a problem in that area you might see the pads or rotor possibly worn on side of the car, it depends on the plumbing, split system etc, you might see it on the diagonal front. It would not cause the tilt/uneven wear of the brake pads you experienced.
It is something in the hub/caliper area, if you have not already fixed it with a new caliper.

 

[PinkLinc]

OK well I learned something new about the banjo fitting! Guess I'll take it apart again so I can at least correct that aspect of it. I'm also going to post this up on NAM and see what comes up. I have an appointment at my MINI shop for next Wednesday. I'd love to get this figured out before taking it to them.

 

[richfinn]

It sounds like the brake caliper is either not mounted square (worn slides) or maybe the bearing was pressed in incorrectly (maybe not pushed home square due to debris)

 

[PinkLinc]

I do have a spare rear hub/bearing. Maybe I'll swap it out and see if that makes any difference.

 

[bd8134]

If you loosen the banjo fitting it might now leak. You most likely got new copper or alum washers with your new caliper. Pick up a pack of these washers at Napa and replace them if you feel compelled to loosen the banjo bolt to the correct setting. You will then need to bleed the brakes. I would just leave it as it is.
Are you still having problems with your brakes wearing uneven?

 

[PinkLinc]

If you loosen the banjo fitting it might now leak. You most likely got new copper or alum washers with your new caliper. Pick up a pack of these washers at Napa and replace them if you feel compelled to loosen the banjo bolt to the correct setting. You will then need to bleed the brakes. I would just leave it as it is.
Are you still having problems with your brakes wearing uneven?

I have some extra copper washers so no worries there. It's too soon to tell if they're wearing uneven but they are definitely dragging compared to the other side.

 

[bd8134]

I would try to logically step by step try to find the problem rather than throw parts in.
1.. Jack up both rear sides of the car. Jackstands etc..
2.. Release handbrake, spin each wheel, don't remove wheel yet.
3.. Grab top and bottom of each wheel and attempt to pull in and out checking for worn or loose wheel bearing, do this also at the 3 and 6 O'clock positions.
4.. Do they spin even? Then apply handbrake a click at each time and check each wheel.
4a.. Same thing with footbrake. Someone slowly depressing and holding footbrake, check each wheel locks at same time.
4.. If wheel does not spin freely, remove that wheel. Looking from above brake caliper do the pads look like they are parallel to the rotor, not twisted?
5.. Remove brake pads, spin freely?
6.. Check for wear on the new brake pads, even so far across?
7.. If still not spinning freely then remove brake rotor and spin hub.
8.. What does the wear on the new rotor look like?
I am presuming you replaced the rotor and pads when you replaced the caliper.
Follow these logical steps and it will not be rocket science to find the problem.

 

[geotek]

What ended up happending?

 

[ra42mario]

I am not sure if you found your remedy yet, but I will chime in.

I own an automotive repair shop in Northeast Ohio. Normally uneven pad wear is contributed to guide pins that are not properly lubed. Remove the caliper and the guide pins (there are a couple of different styles). The Guide Pins are either apart of the bolt to remove the caliper, or they are under the caliper in the caliper bracket. You can identify them because they will have a rubber boot on them.

Clean the pins with a wire wheel and lube them up with brake & caliper grease. At the shop we use CRC Synthetic Brake & caliper grease. It is just a thick grease with a paint brush attached to the lid so you can apply it liberally to the guide pins.


Inspect your brake pads after a moderate period of time for wear. If they still are wearing uneven you could possibly have a sticky caliper (but it sounds like you replaced this) or a defective rotor.

 

[Bella123]

I have a similar problem on my rear driver side brake and I'm trying to argue the point with the garage that it should be a warranty issue and they need to work out why it's happening and not just change the pads. Did you ever find out what the problem was?

 

[dadsEH]

I have a similar problem on my rear driver side brake and I'm trying to argue the point with the garage that it should be a warranty issue and they need to work out why it's happening and not just change the pads. Did you ever find out what the problem was?

nice 'drive-by' first post man! good intro too.