Grinding drums

[Gmg31]

I took my car out for the first time yesterday and it was immediately apparent that there was a very loud grating from the rear.  I removed the drums and it is clear that they are both rubbing on the front edge of the shoes. One is also scraping the rear cover.  Not entirely sure how this is even possible and presumably buying new ones won’t make any difference.  Other than adding a washer to each stud I’m not sure what my options are.

[BERNIEHUMBER]

HI:
"for the first time yesterday" so these are shoes that you just put in?
My bet is that the shoes are too wide.The washer idea would probably work but I would want to find out why the grinding in the first place.
As I recall my S2 had 1.25 inch wide shoe material.
Another thing to check is that the shoes are pushed against the back plate.
Good luck

[EuropaTC]

Another vote for checking shoe width, my TC should be the same as yours with 1.25" shoes, the later Specials had 1.5". Might be worth checking to see if you've been given the correct width.
Brian

[Grumblebuns]

I measured the distance from the edge of the shoes to the hub, there is about 0.29" (7.4mm) clearance. I'm assuming that the drums abuts the hub.  Like others have said, check the width of your shoes, should be 1.25".

[pboedker]

Have you seen this topic from about a year ago? http://www.lotuseuropa.org/LotusForum/index.php?topic=1965.0

It turned out the outer spacer was missing, causing the hub to be located too close to the rear plate. There are some nice photos and a list of dimensions of various parts to check out, just in case you measure your brake shoes to the correct dimension and need to search for another explanation.

[Gmg31]

A saw that thread a while back ( I think there were a couple) and stripped mine down again prior to completion to make sure I hadn’t made that mistake.

I’ve just placed a ruler across, as above, and it’s barely 3 mm and certainly not 7.9 mm

I’ve just double checked mine and the shoes are 1.25”.  I wonder if the PO had changed the drums? They're the only part that’s not new.  I’ve just measured the drums and they appear to be approx 38mm deep.

[EuropaTC]

Hmm, something sounds wrong there on the axle assembly based on what Grumblebuns has measured.  I don't know the width of the spacer between the hub and outer bearing but  I do have the drums from my TC (the same as yours) on the shelf so I can easily measure them and post up later this morning.

The only other spacer is the one between the bearings but I thought it was the inner bearing that floated, not the outer and if that's right then I can't see how getting the smaller spacer in there would affect the hub position.  Odd one.

Brian

Edit to add: Measured the TC drums which should be the same as yours and confirm your 38mm depth, so the drums are the right ones. If you've got all the right bearings & spacers in there then I'm puzzled on this one. Backing plates ?

[GavinT]

I'm pretty sure the outer spacer is 3/8 inch, so about 9.5 mm.
You should be able to see the spacer behind the hub if you've got the brake drum off.

[Gmg31]

Fortunately I have taken photos at every stage of this project so it was easy to check I had fitted the spacer.  However what I did find when I put a ruler across the hub is a clear difference between the position of the left and right shoes. The left is very close to the drum and the right is about 5 mm from the drum.

[EuropaTC]

 

You've clearly got a spacer in there and the shoes themselves look to be right so is the back plate bent then ? A caliper across either side from the ruler to the first contact on the plate should answer that one I expect. It does look that way from the shoes though.

If the backing plate is bent then congratulations on having the most unusual problem this week !   

[GavinT]

Hmmm . . . OK, the outer spacer is in place.

Can’t quite see it in the second pic, but it appears the left hand shoe isn’t sitting correctly with respect to the slave cylinder. It looks a little off centre to me.
Has that hand brake lever been ground down a little via contact with the drum?

Note that there are rubbing pads on the back plate where the shoes should be in contact at all times. I’ve placed a blue circle around one pad.

Check that both shoes are contacting their respective rubbing pads.
My current theory is that the left shoe is cocked up (engineering term) on the slave cylinder and not touching at least one pad.

You can use these rubbing pads as datum points, too. Their positions can be measured sufficiently with your ruler across the hub as you’ve been doing.
If the pads are at significantly different distances from the hub face plane, then you may be looking at a bent backing plate.

[EuropaTC]

Has that hand brake lever been ground down a little via contact with the drum?

Hmm, good spot. I wonder if the radius of the marks aligns with that handbrake lever ?  To have one bent backing plate is bad luck, but to have two you'd need to be really special 

I went through my records and found this shot from when I had drum brakes. The lever looks to be different from the one you have there, it doesn't appear to protrude as far as the edge of the shoes and the actuating arm outside of the backing plate looks shorter. Or it could just be the angle of the photo but if it would help I'll still have them in the "keep for reference" cupboard.

Edit to add......

Just after I posted that I had another look at your photo.  Is that the pivot pin outside the rear wheel cylinder ? If so it should be clamped underneath the two "arms" at the front of the cylinder and would account for how the arm looks bigger than the ones I had.

[GavinT]

Is that the pivot pin outside the rear wheel cylinder ? If so it should be clamped underneath the two "arms" at the front of the cylinder and would account for how the arm looks bigger than the ones I had.

Also a good spot by you too. 

Yep, that handbrake pivot lever appears to be sitting too close to the drum.

Here's three pics of the S2 set up.
It can be seen that the lever doesn't protrude beyond the width of the brake shoe.
As Brian says, that pivot pin should be behind the alloy arms of the brake cylinder, I reckon.

[Gmg31]

Thanks gents. I realised when looking at the photos that the pivot pin should be under the cylinder. School boy error.

[Gmg31]

All fixed now.  Ready for another attempted test drive this weekend.