32 replies to this topic

[orcadian]

Thanks for all the replies - just goes to show, you're never too old to learn

[tuf998]

I agree with making an angled edge on drums and rotors. Maybe the following should be done? the pads/linings dont go past the outer edges and yet the drums and rotors are easy to remove

ps the blue bits are the calipers and drum linings. red is brake pads and black is the drum/disk

[orcadian]

Thanks tuf998,
that is exactly what I was suggesting - a picture is worth a thousand words. This thread proves to me that we often accept things the way they are, rather than questioning the reason - 'we've always done it that way'. I will accept some of the criticism of my proposal, but not just speculation or hearsay - as an Engineer I only want hard, tried and researched facts - that's how we progess.

Edited by orcadian, 02 November 2010 - 11:24 AM.

[tuf998]

well said orcadian. Being a general motor mechanic I hate removing lipped drums and pads off lipped rotors. The answer is right there as Ive shown but I would assume that it would be the manufacturing cost that stops it. customers want to pay minimum prices even though there are benifets to be had in some cases.

Edited by tuf998, 02 November 2010 - 11:47 AM.

[Ethel]

Dan's point about uneven temperatures & expansion seems credible. Since both situations increase tolerances over newly fitted linings & drum/discs it ought to be possible to back off the linings enough to get the brakes stripped down. A good slapping about with a copper mallet has always worked on drums for me. I've discovered corrosion where the hub flange fits in the drum is often a bigger problem. Shoes are mounted on springs so can't really hold the drums solid, if they don't move at all it must be worth looking elsewhere.


A seized adjuster is a problem that needs fixing with or without the drum on. Fair enough, it may be easier to tackle a Mini front drum adjuster with the drum off, and be marginally easier on the rear if sprayed with penetrating oil from both sides. I think I'd prefer threaded holes in the drum to accept a puller.

[tuf998]

Its not the fact that the linings are pushed into the drums. Its when the brakes are worn and then adjusted to even thought the linings are pulled back by the springs the linings are sitting that tiny but further out than normal and so foul on the lip on the drum. Then you need to spend time trying to back off the adjuster and thats ok unless they're siezed/rusted lol

[mk3 Cooper S]

I did the proposed mod to a set of minifins as the lip had got bad.

As I stated earlier they went oval. If you removal in inner ring or lip you are reducing the minimum mterial thicknes as the drums wear.

[tuf998]

Cheers for the info Its settled then ay

[MRA]

If the lip is that big then you are compromising your safety and any other road, path or possibly even field user...... ie when your brakes fail where will you stop ?

The lip is left in place by most motor mechanics so as to keep an eye on wear and therefore replacement point.

removing the lip or adding a chamfer to the edge is in my opinion asking for trouble.

[tuf998]

If the lip is that big then you are compromising your safety and any other road, path or possibly even field user...... ie when your brakes fail where will you stop ?

The lip is left in place by most motor mechanics so as to keep an eye on wear and therefore replacement point.

removing the lip or adding a chamfer to the edge is in my opinion asking for trouble.

We dont want to make the chamfer so we can use the discs and drums longer thats stupid. Only so when they're worn they can be very easily removed

[orcadian]

If the lip is that big then you are compromising your safety and any other road, path or possibly even field user...... ie when your brakes fail where will you stop ?

The lip is left in place by most motor mechanics so as to keep an eye on wear and therefore replacement point.

removing the lip or adding a chamfer to the edge is in my opinion asking for trouble.

We dont want to make the chamfer so we can use the discs and drums longer thats stupid. Only so when they're worn they can be very easily removed

Thanks for that tuf998,

I had all but given up on this post - it seems that no one (except your good self!) had actually read the original topic title (anyone tried to PREVENT this?) I have never suggested chamfering worn out components to get some more miles - I am fortunate in having sufficient money to replace stuff at the right time. If the guy with the Minifins waited till they had a big lip AND THEN chamfered them then I'm not surprised they went oval. As for ending up with no brakes as was recently suggested, please feel free to tell me how. I would never rely on a visual check of a wear lip either, it's too subjective - the manufacturers give EXPLICIT measurements for min. disc thickness and max. drum diameters.
However, many thanks for all of your interesting replies.

[l_jonez]

the problem i can see with it is how long the chamfer would have to be. quick drawing....



same as above black- drum, blue - shoes but the grey is how the drum would wear

if the chamfer starts at the end of the shoe then it will still create a lip (just a narrower one). if you wanted to create a chamfer that stopped a lip forming then it would need to be much wider meaning that a section of the pad would not be in contact with the drum (when new)

[tuf998]

good points, the second diagram is the ideal one. the trick is to use mathematical stunts to work out where the maximum runout would be and make the chamfer adjusted to that. And so minimising the bit of low contact with new pads as best as can.

Edited by tuf998, 03 November 2010 - 11:52 AM.

[bunch1980]

Now i know why one weekend i could not get the drum off lol and i only had 1 screw holding it on is that normal dont matter to much as wheel holds it on also.
Only after did i read haynes and realise i need to slacken off adjusters to, thankfully mine are easy to move last time i adjusted them.

It also probably wont help the fact i left the hand brake on 2 notches other week for a mile or so whoops! will try again soon to get those drums off!!!

[tuf998]

yea 1 screw would be ok, two is preferred though. Yea if you do get the drums off, wouldnt hurt measuring them, as when they have a small lip that is very close to maximum runout. (I could be wrong though as I dont know the specs)