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1977 T140, still with original Brake Discs.

6K views 41 replies 12 participants last post by  StuartMac 
#1 · (Edited)
I'm focusing on my original chrome plated (I think?) brake discs, before getting on with my wheel reassembly.


The appear on reasonable condition for their age but a lot of the chrome finish has given way to rust.

I've cleaned much of the rust away but understand the chrome finish isn't the best in terms of braking performance.

How many times can I have them skimmed?

Is the reduced disc thickness taken up with brake adjustment?


Thanks

R R
 
#2 ·
One shop I used to work at machined them it does remove the chrome. Me I wouldn't worry as long as they are in good shape all of mine show wear and a bit of rust. Your bike do as you wish.

One famous authority told me they were never chromed after I questioned one I purchased for my business stock. Told some other guys about it we all had a good laugh but it did make me watch everything else he has told me since.

I suppose the service manual may have wear specs.

#1 They can be machined as many times as you want as long as minimum thickness is maintained.

#2 You are not reducing the diameter of the disc only the thickness. The reduced thickness will be compensated just as pad wear is compensated.


K
 
#5 · (Edited)
Hi, 'mornin' K, :wave

a lot of the chrome finish has given way to rust.
understand the chrome finish isn't the best in terms of braking performance.
Having owned a T160 from brand-new, here where the climate can be a tad ... errr ... wet ... occasionally, if a disc's chrome is completely intact or all-gone, the braking performance, particularly in the wet, is fine; it's when they're part-chromed and part-not that wet performance is crap (dry, it's still fine).

How many times can I have them skimmed?
What would the minimum thickness specified be?
Original discs have a 45-degree chamfer around the outside edge of each side. It isn't particularly accurate but the distance between the two is between 3/16" and 1/4". As long as those chamfers are visible, or the disc exceeds that thickness, it's :thumb

Btw, to forestall any "both surfaces must be ground at the same time" horlicks, if you pick a competent machinist (how often have you read that? ;)) that realises the reference for both sides is the face that sits against the hub, each side can be machined separately (yes, this is first-hand experience :)). First time, check that the machinist known the chrome is only microns thick, so not a lot of actual disc material needs removing ...

Is the reduced disc thickness taken up with brake adjustment?
Hydraulic brakes compensate automatically, although usually for pad wear.

Hth.

Regards,
 
#6 ·
Hi, 'mornin' K, :wave


Having owned a T160 from brand-new, here where the climate can be a tad ... errr ... wet ... occasionally, if a disc's chrome is completely intact or all-gone, the braking performance, particularly in the wet, is fine; it's when they're part-chromed and part-not that wet performance is crap (dry, it's still fine).



Original discs have a 45-degree chamfer around the outside edge of each side. It isn't particularly accurate but the distance between the two is between 3/16" and 1/4". As long as those chamfers are visible, or the disc exceeds that thickness, it's :thumb

Btw, to forestall any "both surfaces must be ground at the same time" horlicks, if you pick a competent machinist (how often have you read that? ;)) that realises the reference for both sides is the face that sits against the hub, each side can be machined separately (yes, this is first-hand experience :)). First time, check that the machinist known the chrome is only microns thick, so not a lot of actual disc material needs removing ...


Hydraulic brakes compensate automatically, although usually for pad wear.

Hth.

Regards,
Thanks Stu.

So in summary, ensure minimal skimming is done, that the two chamfers on the edge of the disc are the wear/skim indicators, and that each face should be skimmed separately using the surface which mates with the hub.

Assuming the the disc can only sit on the lathe one way, using the face which mates with the hub, then is the machinist easily able to skim each side?
 
#13 ·
About 1/3 of the chrome is worn from mine. Each time I have the wheel off I remove the disc and clean them up with a vibratory sander and 60-80 grit pad, keeping it moving as I work. This dulls and scratches the chrome and cleans off any rust. I wash off the dust when I'm done . The resulting surface seems to brake well and definitely looks better, no squealing. Wet braking seems fine to me, though I don't ride fast in the rain.
 
#14 ·
If there's a plating shop nearby, drop off the disc and they will remove the chrome chemically...Machining the disc may not be necessary .....And some shops don't like to grind off chrome plating...
 
#19 ·
Interesting option T.

I called a large chrome plating business near where I work to discuss it.

He quoted $30 a disc to reverse the plating, but he said it will only work if it's nickel based chrome.

He said if its hardened chrome then it won't work.


Not knowing for sure, I'd assume they'd have to be plated with hardened chrome to handle their braking function.
 
#15 ·
For your consideration:

As I have previously said if it was mine I would use them as is. Take the wife out to dinner with the money you do not spend.

Happy Wife Happy Life

I doubt you will find that acceptable so next I would send an Email to www.oldbritts.com in the States they machine Norton rotors they may have a contact in your area. If that doesn't work you could contact the Triumph Owners Club of Australia or New Zeeland maybe they can be of assistance.



K
 
#18 ·
I had mine Blanchard ground by a guy on eBay. He did a nice job. Painted it too. It was $75 plus shipping. I know its about the cost of a new one but I feel better keeping the original. He puts an add in every once in awhile. He has an add for norton discs at the moment.

ghf150


Brian
 
#24 ·
I'm focusing on my original chrome plated (I think?) brake discs, before getting on with my wheel reassembly.
The appear on reasonable condition for their age but a lot of the chrome finish has given way to rust.
I've cleaned much of the rust away but understand the chrome finish isn't the best in terms of braking performance.
How many times can I have them skimmed?
Is the reduced disc thickness taken up with brake adjustment?
Thanks
R R
Mine warped in the first year of life.
I had a local truck machine shop true them up but it left them with some chrome and some bare metal.
The resulting braking, especially when wet, was grab, slip, grab, etc as each surface condition contacted the brake pads.
No point of cleaning them up unless you strip them entirely of chrome.
You might just as well put them on the shelf and buy some bare cast rotors. They'll serve you best and you'll have some nice antique chromed rotors to hang in the garage.
 
#31 ·
I had a disc skimmed years ago by a triumph (Meriden) dealer who also raced the bikes and built slippery Sam replicas and rob North framed specials. I'd say they knew their stuff.

There is a relatively new machine for cars that allows a portable unit to bolt to the wheel hub and skim both sides of the disc simultaneously
it's used on top of the range cars so isn't a bodge
 
#33 · (Edited)
Hi Marc.

I have found the absence of "in the flesh person to person" interactivity in Forum communications overly relies on the written text.

As a significant part of the way humans interact and communicate has been removed, we can often misinterpret what is being said as well as its severity.


I've found that I can partly overcome this by putting forward my points as a question rather than a statement.

If you project in a question form you can put a case forward without ownership or attachment to it.

In this way, as you've displayed non-attachment a responder is more likely to address the issue rather than associating you with it.


It can be as simple as the way one presents.

You win I lose, or you lose I win, should be avoided.

Good communication always results in I win you win with no loss of face.

It should never be about winning as this implies that there will be a loser.

If I'm attached to something in particular, rather than revealing this, I'll ask a concern I might have in a non-attached question form.

If someone disproves or minimises my leaning, I haven't lost as I did not display attachment.

On the other hand, if one's non-attached concern holds, then you have made you case.




What are your thoughts?
 
#38 ·
I took a trip out to the Chrome Platers used by a south eastern Melbourne Classic Motorcycle restorer.


They have the experienced and will be stripping the chrome plating on my Brake Discs for AUD$40 the a pair.

Took my mudguards for assessment while out there.

They'll be stripping, repairing, and plating front and rear guards for AUD$410.

I hope they don't repair the fitted dent in the rear guard. :)
 
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