Page 1 of 2

checking drums for "roundness"

Posted: Sun Jul 31, 2011 8:15 am
by Dean Moriarty
I'm in the process of overhauling my braking system.
I've noticed that virtually all the wheels have stiff spots where the brakes appear to bind as you hand turn the wheel. I've tried using the adjusters with little success.
I thought it would be a good idea to get the drums checked for roundness and phoned a local engineering company for a quote for checking and skimming if necessary.

The figure they quoted was £40-50 per drum. I must admit I was expecting to pay a similar figure for all 4 in total.

What is a reasonable figure I should be expecting to pay and does anyone have a good recommendation in the cheshire/lancashire area? Please feel free to PM if we are not allowed to recommend on the open forum.

Many thanks

Re: checking drums for "roundness"

Posted: Sun Jul 31, 2011 9:04 am
by David53
Are you sure they are out of round? Mine also rubbed a little in spots, but I have just backed off one click on the adjuster until no rubbing at all and I still have a firm pedal. I think it's more likely the shoes are not perfectly shaped as opposed the drums. Does your Series II have the older cast hub/drums like mine or the more modern removable drum?

Re: checking drums for "roundness"

Posted: Sun Jul 31, 2011 9:49 am
by mike.perry
Adjust the brakes then push hard on the brake pedal a couple of times, this usually centres the shoes. If they still rub then back off an extra click. It is only a problem if you can feel the pedal pumping when braking.
There is no reason for the drums to go oval as the brake shoes are doing the same as your expensive machinist would do. The usual problem is with scored drums though letting the linings wear down to the rivets, but with bonded linings even this is less of a problem

Re: checking drums for "roundness"

Posted: Sun Jul 31, 2011 9:58 am
by MarkyB
You need to check after they have had a chance to bed in.
Even then you may be able to hear a little rubbing, but unless you can feel something when using the brakes I wouldn't worry about it.

Re: checking drums for "roundness"

Posted: Sun Jul 31, 2011 10:01 am
by bmcecosse
It's normal for the drums to 'touch' slightly as you spin them round - don't worry about it! The shoes can move about on the cylinders anyway - and it's not as if they only press on one part of the drum when you use the brakes - they are pushed on to the whole surface as the drum revolves - at least they will do once initial high spots on the linings have worn away. The price quoted is crazy - and probably a useless operation anyway - what would they have centred on ? The hole in the face of the drum is not an accurate register..........

Re: checking drums for "roundness"

Posted: Sun Jul 31, 2011 7:31 pm
by Dean Moriarty
I've had drums that "touch" before but these are either so tight you can hardly turn them at one position of the wheel and free turning at other positions.

Re: checking drums for "roundness"

Posted: Sun Jul 31, 2011 8:57 pm
by mike.perry
Have you checked that the pistons are fully retracting?
Have you tried swapping the drums over or the shoes from top to bottom?

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 12:36 am
by David53
I'm with Mike - if your adjusters are backed right off and the wheel is sticking then you must have a cylinder stuck open.

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 8:41 am
by Dean Moriarty
Fair comment. They did seem a bit slow retracting. I'm renewing all the cylinders as part of the overhall so I'll see if the problem remains.
Cheers

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 9:50 am
by bmcecosse
Probably best to use the 'genuine' cylinders then - the non-gen front cylinders have been getting poor Press Reviews recently.....although rears seem to be ok.

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 9:51 am
by mike.perry
Try removing the piston from the cylinder and cleaning between the piston and the cap, open the bleed valve and push the piston fully in.

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 11:32 am
by Dean Moriarty
Ok they are coming apart today.
As a slight aside, what size brake unions does the Minor use?

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 2:46 pm
by taupe
Hi

3/8 Unf onto the front cylinders 3/8 BSF on to the rear.

Assuming you have the standard set up-

The rear flexi hose should be standard BSF female to accept the BSF pipe/union from the master cylinder

The other end of the hose is UNF and screws into the rear 3 way T connector the bottom one of the tee is marked with UNF on the casting The other two ways on the tee are BSF to the rear brake cyls.

Although it seems a bit strange to mix these threads it does result in the front and rear hoses being the same ie one end UNF male, other end BSF Female.

Also all the main brake pipes have BSF both ends except for the two short pipes linking the front cylinders.

Taupe

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 3:45 pm
by Dean Moriarty
Hi Taupe

Thanks for the info.

Just to make sure I've got that straight: Specifically the front flexi hose to copper pipe union is UNF?

Thanks

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 4:55 pm
by bmcecosse
Yes in fact on my car the front flexi hoses are 3/8" UNF at both ends........

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 5:21 pm
by Dean Moriarty
Is that because you have Wolseley or Riley front drum set up? :wink:

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 5:36 pm
by bmcecosse
Makes no odds - same fitment for all the sets.

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 10:55 pm
by taupe
Dean

No the front flexihose to the brake pipes is 3/8 BSF(female on the hose) the other end is 3/8 unf male into the front wheel cylinders which are all threaded 3/8 UNF hence the different unions on the front link brake pipes only. The rear cyls are 3/8 BSF.

taupe

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 11:05 pm
by bmcecosse
Not mine! I know - because I made and fitted new pipes and new flexis at the front ..... 3/8" UNF both ends.

Re: checking drums for "roundness"

Posted: Mon Aug 01, 2011 11:07 pm
by taupe
Yes BMC

But yours is not standard in the braking department :roll:

taupe