Rechroming discs

[Mark]

Hello all.
I'm thinking of getting something done with the ragged chrome on my 350 Sport's discs.
What's the current thinking, do I strip them back to the cast iron (it is cast underneath isn't it?) and leave it at that, or is it viable to get them rechromed?
If they are rechromed, should it be hard chrome or just ordinary decorative? I assumed hard, but someone in the trade recently told me that ordinary would suffice.
What about pad choice in relation to either option, ie, should only organic pads be used on chromed discs etc?
All info gratefully received.

Also, anyone have any info on the arrangement that held the clocks on the early double drum sport? Whereas the later bikes have a single holder with 2 holes to locate the two clocks, I
understand from Stuart at NLM that this model had 2 components doing this job.
Does anybody have any for sale or even any info/photo please?

Many thanks,
Mark.

[EVguru]

The discs are pressed steel and hard chromed.

Decorative chrome is at maximum about 1 thousandth of an inch thick, whilst hard chrome (which isn't actually any harder) is up to around 20 times thicker.

The difficulty in getting discs re-plated will be in finding someone who can correctly grind them afterwards to achieve flat an coplanar surfaces.

You might be best off getting the remaining chrome stripped.

[alexluzzi]

yes, Stuart is right.
I have the 2 components, even if unpainted.
Write a message to my address and I will send you a picture.
alexluzzi@gmail.com
regards

[Mark]

Hmmm,
That's interesting.
Thanks for the input.
Is it really that difficult for an engineering company to get a flat chromed disc true - I'm reasoning that somebody did 30 odd years ago when the bikes were new, so why not now?
I have a couple of bikes with this problem so I assume I'm not alone.
What does everybody else do, strip, chrome, replace or nothing?

Regards,
Mark.

[EVguru]

Is it really that difficult for an engineering company to get a flat chromed disc true - I'm reasoning that somebody did 30 odd years ago when the bikes were new, so why not now?

Brake discs are Blanchard ground, but on a special fixture that allows both sides to be ground without remounting them.

There's an example of such a machine here; http://www.dcm-tech.com/dcm_products/br ... rinder.php

Thin motorcycle discs will tend to resonate and I suspect the OEM machines ground both sides simultaneously to counteract this. Cast Iron discs are self damping to some degree, but steel (and in particular stainless) can ring like a bell!

There are a few companies offering to regrind motorcycle discs, but generally only flat discs, ie. those with no integral tophat, or semi-floaters that have been removed from their hubs.

I have a couple of bikes with this problem so I assume I'm not alone.
What does everybody else do, strip, chrome, replace or nothing?

Most owners seem to do nothing. NLM commissioned new discs from Grimeca, but they don't seem to have as fine a finish as the old ones (I have a pair of NOS for comparison). I and others have had problems with scoring if you ride in the wet before the disc surface is fully run in (mirror finish).

Some people have upgraded to a semi floating disc (modified Ducati rear).