Rear wheels Sense check
Discussion
I have a venerable 2004 R53 Mini Cooper S which is a long term keeper, scrupulously maintained by me. I can hear a rhythmic rumbling from the rear which I've ascribed to a worn wheel bearing. That in itself isn't a problem, however, in checking which side I've discovered my offside rear is binding a little.
About this time last year, I replaced both rear calipers & handrake cables with new & adjusted them to a light drag with the handbrake off, all good there. Yesterday, I released the adjustment on the handbrake cable with the intention of redoing it but found even with the cable slackened, no difference was seen at the wheel. I'm thinking caliper rather than cable but since the handbrake cable mehanism is strongly springloaded at the caliper, that seems questionable.
For the record, I also removed & relubed the slider pins on both wheels while I was in there & the pads are about 50% worn. Open to suggestions on why the wheel is binding. Should add the wheel rotates freely once free of the caliper.
About this time last year, I replaced both rear calipers & handrake cables with new & adjusted them to a light drag with the handbrake off, all good there. Yesterday, I released the adjustment on the handbrake cable with the intention of redoing it but found even with the cable slackened, no difference was seen at the wheel. I'm thinking caliper rather than cable but since the handbrake cable mehanism is strongly springloaded at the caliper, that seems questionable.
For the record, I also removed & relubed the slider pins on both wheels while I was in there & the pads are about 50% worn. Open to suggestions on why the wheel is binding. Should add the wheel rotates freely once free of the caliper.
Do the pads move freely?
Perhaps as a sign that I should be spending more on pads, I find that I always (or at least often) need to file off the ears slightly when new to make them fit better. I've always wondered if the metal mould is spot on but then a coating of paint is applied which brings them out of spec.
Perhaps as a sign that I should be spending more on pads, I find that I always (or at least often) need to file off the ears slightly when new to make them fit better. I've always wondered if the metal mould is spot on but then a coating of paint is applied which brings them out of spec.
Check what the brake fluid looks like at the effected caliper. I had a binding brake problem on my car that took ages to figure out, including garages replacing the caliper twice! It turned out that the inside of one of the brake lines was degrading and there was crud in the fluid, the brakes went on fine as there was enough pressure to force it through, but it was blocking the caliper from releasing properly. A replacement brake line, cleaned out caliper, and new brake fluid has fixed the problem.
Cheers chaps, some decent ideas to explore.
Couple of other things, the pads on the affected wheel are wearing slightly asymetrically, just a touch thinner on the upper side & in the cabin, the handbrake cable at rest is slightly shorter on the offside wheel as in I would expect them to be equal lengths as they meet at the handbrake union/clamp fixing if they were wearing at the same rate.
Couple of other things, the pads on the affected wheel are wearing slightly asymetrically, just a touch thinner on the upper side & in the cabin, the handbrake cable at rest is slightly shorter on the offside wheel as in I would expect them to be equal lengths as they meet at the handbrake union/clamp fixing if they were wearing at the same rate.
Before you strip everything, just check for that brake bind with the suspension at running height, not at full droop.... eg if it's jacked up and on stands , raise the rear arm with a trolley jack under the shock lower mount. The problem with these is that the outer sheath of the handbrake cable is too short and, on full droop, pulls the caliper inwards, note that it doesn't operate the caliper handbrake lever, it actually tugs the whole caliper across on its slides, bringing the outer pad into contact with the disc. It's bad enough with OE cables but even worse with aftermarket ones (I now will only ever fit OE ones to these).
Re your initial issue, the rumbling noise could well be tyres, check that they haven't gone out of shape and are now multi-faceted (they will feel rough and bumpy when spun with your palm brushing the tread area).
@tux850 In 44 years of professional 'spannering', I have NEVER had to file a pad to make it fit, the problem is ALWAYS failure to remove the baked-on crud in the pad carrier, they just have to be scraped back to bare metal (before adding the lightest smear of a suitable grease). Yes it's hard work, but it has to be done if you want happy brakes.
Maybe you're buying really nasty quality pads.
Re your initial issue, the rumbling noise could well be tyres, check that they haven't gone out of shape and are now multi-faceted (they will feel rough and bumpy when spun with your palm brushing the tread area).
@tux850 In 44 years of professional 'spannering', I have NEVER had to file a pad to make it fit, the problem is ALWAYS failure to remove the baked-on crud in the pad carrier, they just have to be scraped back to bare metal (before adding the lightest smear of a suitable grease). Yes it's hard work, but it has to be done if you want happy brakes.
Maybe you're buying really nasty quality pads.
That's a good shout. never thought of that, although they did fit fine new last year. On the bearing, I'm relaxed about it since it's a four bolt unit on these which makes life easy, rust notwithstanding & I wasn't especially convinced either side had failed when I checked yesterday. One of those keep an eye on it, see what develops scenarios
TwinKam said:
@tux850 In 44 years of professional 'spannering', I have NEVER had to file a pad to make it fit, the problem is ALWAYS failure to remove the baked-on crud in the pad carrier, they just have to be scraped back to bare metal (before adding the lightest smear of a suitable grease). Yes it's hard work, but it has to be done if you want happy brakes.
Maybe you're buying really nasty quality pads.
^^^ this 100 foldMaybe you're buying really nasty quality pads.
Almost no one pings off the stainless spring clips and cleans up the pad carrier of the caliper itself, nor give the spring clips themselves a clean up if refitting the same ones, crud always builds up over time between the clips and the caliper.
Every time when you clean things up properly, both the old pads, and if replacing with new, the new pads, slot into place so much easier than the old ones came out.
A few minutes spent exersing the pistons in their bores pays dividends too, its one of the reasons i prefer the drum inside disc park brake design rather than self adjusting calipers which also serve as the manual park brake, allows as easy exercising of the rear calipers as one enjoys with the typical fronts.
Smint said:
Almost no one pings off the stainless spring clips and cleans up the pad carrier of the caliper itself, nor give the spring clips themselves a clean up if refitting the same ones, crud always builds up over time between the clips and the caliper.
Ah, that's interesting actually.I was going to reply to TwinKam's post saying that all the calipers I've worked on have had stainless steel clips in and so haven't been subject to any corrosion (bar perhaps a bit brake dust discolouring) so I doubt that's it. But of course - what I don't explicitly recall ever doing is removing the clips and giving the calipers behind a good clearing out. Thank you both - something for me to take on board for next time.
Smint said:
TwinKam said:
@tux850 In 44 years of professional 'spannering', I have NEVER had to file a pad to make it fit, the problem is ALWAYS failure to remove the baked-on crud in the pad carrier, they just have to be scraped back to bare metal (before adding the lightest smear of a suitable grease). Yes it's hard work, but it has to be done if you want happy brakes.
Maybe you're buying really nasty quality pads.
^^^ this 100 foldMaybe you're buying really nasty quality pads.
Almost no one pings off the stainless spring clips and cleans up the pad carrier of the caliper itself, nor give the spring clips themselves a clean up if refitting the same ones, crud always builds up over time between the clips and the caliper.
Every time when you clean things up properly, both the old pads, and if replacing with new, the new pads, slot into place so much easier than the old ones came out.
A few minutes spent exersing the pistons in their bores pays dividends too, its one of the reasons i prefer the drum inside disc park brake design rather than self adjusting calipers which also serve as the manual park brake, allows as easy exercising of the rear calipers as one enjoys with the typical fronts.
same line, same hymn 
Should also add that this descaling exercise CANNOT be done without removing the pad carrier and taking it to the bench, even if it's only a pad change and the carrier isn't coming off to remove the discs. Only with the disc out of the way can all of all of the faces of all of the pad slots be properly cleaned through from end to end. Even if you think they look OK and the new pads fit OK without scraping back to bright metal, they won't be free for their lifespan if you don't start with a clean sheet. Makes me wince when I hear someone say they can change pads in ten minutes; no you can not.
TwinKam said:
same line, same hymn Should also add that this descaling exercise CANNOT be done without removing the pad carrier and taking it to the bench, even if it's only a pad change and the carrier isn't coming off to remove the discs. Only with the disc out of the way can all of all of the faces of all of the pad slots be properly cleaned through from end to end. Even if you think they look OK and the new pads fit OK without scraping back to bright metal, they won't be free for their lifespan if you don't start with a clean sheet. Makes me wince when I hear someone say they can change pads in ten minutes; no you can not.
Nobody has mentioned the corrosion that expands the rubber guides the slider pins pass through on the caliper, I've done hundreds
of these over the years for customers and it's one of the main problems with mini rear brakes not operating properly. Are you finding the sliders
are still stiff even after greasing them?, if so you need to remove the rubbers and clean away the alloy corrosion on the caliper,
this stuff expands the rubber and tightens against the slider pins, clean it right back to clean metal and grease it up, then replace the rubbers
and slider pins.
of these over the years for customers and it's one of the main problems with mini rear brakes not operating properly. Are you finding the sliders
are still stiff even after greasing them?, if so you need to remove the rubbers and clean away the alloy corrosion on the caliper,
this stuff expands the rubber and tightens against the slider pins, clean it right back to clean metal and grease it up, then replace the rubbers
and slider pins.
President Merkin said:
Yep, you're right, the calipers are a year old but the slide pins on both sides had corrosion at the exposed ends & were bone dry too. I put all four in a drill & sanded them back to cean with a bit of 800 grit & relubed all four.
Did you remove the rubbers on the calipers that the sliders pass through?, it's the alloy corrosion behind these rubbers that buildsup pressure on the slider pins.
Master Of Puppets said:
Nobody has mentioned the corrosion that expands the rubber guides the slider pins pass through on the caliper, I've done hundreds
of these over the years for customers and it's one of the main problems with mini rear brakes not operating properly. Are you finding the sliders
are still stiff even after greasing them?, if so you need to remove the rubbers and clean away the alloy corrosion on the caliper,
this stuff expands the rubber and tightens against the slider pins, clean it right back to clean metal and grease it up, then replace the rubbers
and slider pins.
of these over the years for customers and it's one of the main problems with mini rear brakes not operating properly. Are you finding the sliders
are still stiff even after greasing them?, if so you need to remove the rubbers and clean away the alloy corrosion on the caliper,
this stuff expands the rubber and tightens against the slider pins, clean it right back to clean metal and grease it up, then replace the rubbers
and slider pins.
A Dremel 'chimney sweep' brush (#530) is the ideal tool for this task, perfect size. It occurs on all the Fords/Volvos/Mazdas which have similar alu calipers. I've never had to repeat the process on any given car, which tells me that the red rubber grease I use to prevent the corrosion restarting actually does a good job; clearly nothing at all is used at the factory.
TwinKam said:
Master Of Puppets said:
Nobody has mentioned the corrosion that expands the rubber guides the slider pins pass through on the caliper, I've done hundreds
of these over the years for customers and it's one of the main problems with mini rear brakes not operating properly. Are you finding the sliders
are still stiff even after greasing them?, if so you need to remove the rubbers and clean away the alloy corrosion on the caliper,
this stuff expands the rubber and tightens against the slider pins, clean it right back to clean metal and grease it up, then replace the rubbers
and slider pins.
of these over the years for customers and it's one of the main problems with mini rear brakes not operating properly. Are you finding the sliders
are still stiff even after greasing them?, if so you need to remove the rubbers and clean away the alloy corrosion on the caliper,
this stuff expands the rubber and tightens against the slider pins, clean it right back to clean metal and grease it up, then replace the rubbers
and slider pins.
A Dremel 'chimney sweep' brush (#530) is the ideal tool for this task, perfect size. It occurs on all the Fords/Volvos/Mazdas which have similar alu calipers. I've never had to repeat the process on any given car, which tells me that the red rubber grease I use to prevent the corrosion restarting actually does a good job; clearly nothing at all is used at the factory.
only when you prise out the rubbers you then see how much corrosion has built up. That one fix alone can often totally transform rear brake / handbrake performance yet can be so easily overlooked.
Got round to this today. No corrosion in the calipers nor slide pin channels. It seems that lubing the pins which were bone dry fromthe factory did the trick.
Also swapped the wheel bearing. Got all the way to refitting the wheels only to discover the wheel bolt threads are wider than the OEM hub & therefore I had to refit the old hub which is irritating. Also bought FAG for quality & double checked the part numbers so doubly annoying, Don't really fancy havng two sets of wheel bolts on the car, so will need to think it over.
Also swapped the wheel bearing. Got all the way to refitting the wheels only to discover the wheel bolt threads are wider than the OEM hub & therefore I had to refit the old hub which is irritating. Also bought FAG for quality & double checked the part numbers so doubly annoying, Don't really fancy havng two sets of wheel bolts on the car, so will need to think it over.
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