I've noticed something about my MINI. I've never had 4 wheel disc brakes before. I'm not that car mechanical. But I've noticed when the rear wheels are in the air (jacked up). I can rotate them by hand and feel some resistance even though the brakes are not applied. I can also hear scraping noises like a brake pag on the rotor (which it may very well be).

But anyway the reason I bring this up is to find out if this is contributing to my poorer performance. Notably poorer fuel economy. More rolling resistance it appears to have see one of my previous postings on rolling the car on the garage floor compared to my Neon)

I just reread my old thread and someone mentioned brake calipers dragging. OK, so is this what it could be? Is this a factory adjustment? If this something I could adjust?

 

Was the parking brake on? I read somewhere else that the parking brake is tied into the rear brakes. Maybe thats where the tension came from...????

 

Parking brake off. Definately off. I even "reset" the parking brake to make sure it was not it.

 

I had my front brakes replaced, and when they were worn down, and with carbon metallic brakes, it is common for the pad to eat into the rotor a little bit. This caused a noisy condition where the brake pad had a "slot" on the rotor where the pad sat during contact. There was a lip on the rotor around the edge where the pad did not hit. If you can revolve your wheels and hear a slight 'whhooooo' of metal contact as you do it, they should be ok. If you cant move them at all, there could be a problem.

 

Are there any adjustments for this?

 

Disc brake pads are ALWAYS in light contact with the rotor on all cars. If they were not, brake pedal freeplay would be extreme.

You should be able to hear the contact as you spin the wheels without the brakes applied.

There are no adjustments.

 

OK, thanks!

That answers my question. No adjustments. So there must be some sort of spring tensioner in it to account for pad wear and disc wear, right?

 

>>OK, thanks! :smile:

It pretty much sits where it sits when you take your foot off the brake. Without the hydraulic pressure the pads don't grip the discs but they are right there ready to go for the next time.

 

>>>>OK, thanks! :smile:
>>
>>It pretty much sits where it sits when you take your foot off the brake. Without the hydraulic pressure the pads don't grip the discs but they are right there ready to go for the next time.
>>
>>


The rear brakes have several internal, mechanically adjusted parts. They are part of the parking brake mechanism. Unless the brakes are being applied, they should NOT contact the rotor. The piston seal is designed to pull the piston back into the caliper. The mechanically adjustable parts are only in the rear caliper, and probably (depending on the type of rear-integral park brake caliper) a part of the piston . There are two main types of RIPB calipers, ball-and-ramp, and cam- the MINI appears to have the former. The slight rubbing noise and resistance described in the first post is caliper drag. So very many things can cause this, that I would be hesitant to guess-corrosion, faulty seal, binding of any number of internal parts...and solving it can be even harder than diagnosing it.

 

OK, one says there is an adjustment and another says there is NO adjustments.

I'm confused :???:

 

>>OK, one says there is an adjustment and another says there is NO adjustments.
>>
>>I'm confused :???:


There are adjustable components in the rear calipers-none that are manually adjustable, though. There are also adjustable(manually) parts in the park brake cable assembly. The rear calipers need a special tool to push the piston back in, to counteract the screw-like adjuster. All parking brakes have self-adjustment mechanisms to account for wear.

 

Both are correct, IMHO:
the driving brake has no adjustments. It basically self-adjusts by varying the amount fo brake fluid in the brake lines, as the pedal returns to resting the correct amount of fluid is sucked into the cylinder and lines from the reservoir.
However, the parking brake does have adjustments, although I am not familiar with the way this works on the MINI.
To my knowledge, on disc brakes you always have the pads just ever so lightly resting on the discs. According to polmear, that should not be so on the rear discs because of the setup with the parking brakes, if I understand P. correctly.
A very slight amount of pad drag on the rotors would not worry me, but if you get noticeable resistance to spinning the wheel on a jacked up car, then there is something wrong and you need to have it checked out by the dealer.
A dragging pad can definitely decrease your mileage and is a safety concern. The dragging can lead to overheating of the brake, and to brake failure because the brake fluid will be set to boil, and other problems can arise as well.
Bottom line, if there is noticeable resistance to the wheel spinning, have it checked out by the dealer!!!