Sport drum brake shoes: Different diameter?

[morini312]

I am trying to mount the front brake shoes which NLM relined for me, but I cannot get the shoes into the wheel drum on one of the sides due to a slight diameter difference. I notice that the shoes are a little different, but the lining material has the same thickness, see attached photos.

The brake shoes on the right have a larger thin area towards the cam. These fit fine, but the one on the left is the problem. I have tried to swap them from side to side, to no avail, but not yet tried to combine large/small on the same side. Strange thing is that according to the spare parts catalogue, the shoes have the same part number so they should be identical. The springs, however, have different part numbers from side to side, indicating uneven inner shoe distances. Two of my springs are slightly longer, so this seems right (though my logic would have the longer springs mounted close to the cam).

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Am I doing something wrong or have I received wrong shoes?

Grateful for any tips:-)

[nickst4]

I guess it's all about quality control, for which the Italians weren't well-known! The shoe castings do appear different, but you'd think the dimensions would be the same. Apart from trying to get another set of shoes and hope for better luck, the pragmatic way would be to turn the linings down to fit the drum. We certainly used to get this done way back when, in efforts to improve on drum brake performance. You'd put some shims behind the cam and turn the shoes to the exact size of the drum, remove the shims and you'd have just the right clearance.

Good luck!

Nick

[morini_tom]

I have no experience of setting these up so I will leave it to others to advise you, however I thought it worth pointing out that putting a good chamfer on the leading shoe is advised to greatly improve the feel and progressiveness of the brake.

The drum sport has good brakes when set up well but when not they can be a bit intimidating!

[3potjohn]

If I am seeing this right the problem shoe friction material is more proud than the one that fits due to that thicker metal end. As said the leading edge chamfer will improve braking. Can you mark the drum edge somehow then try inserting the brake, thereby marking the shoe to verify where it is touching.
I have had similar with rear drums once but think a bit of shoe trimming worked in that case, as can turning the cam 180 degrees.
Good luck.

[MickeyMoto]

On my Strada the new shoes did not fit. NLM found the drum to be oval. I think they ground it round. This can happen with spoke wheels.

I never understand the attraction of a drum. Give me a disc any day.

[morini312]

Thank you for your recommendations! I will absolutely chamfer the brake shoes, but just to be shure (English is not my mother tongue) : You mean to put an angle on the braking material so that its edge is not so abrupt?

To turn the linings down I will have to go over them with a bow file. The trick with shims under the cam is good advice, but requires me to get the brake shoes in there first.

The front brakes were actually very good before I relined them. Only the rear brakes needed fixing and I thought it smart to reline the lot while I was at it. Guess I should have left them alone:-)