Copper sintered disc pads

[Scooterlam]

Just fitted some old ex display ones off eBay.
Fitted easily.
Really impressed with the stopping power especially when I got brake tested today, was willing to lock up.
Only problem is they squeak.
Is this normal I can see it getting tiresome over my 12 day euro jaunt.

[Knowledge]

Did you put copper grease on the back of the two pads? That is supposed to stop the squealing.

[Scooterlam]

Had thought of that but the fixed pad only touches the end of a 6mm stud.
I'll try on the piston side,
It's a hydrolic convention btw.

[Toot]

Yea, the one's fitted to mine squeaked as well. Got to the point that I had to change them as it became annoying

[HxPaul]

Try putting copper slip on the sides of the disc pads,as well as the back.

[Toot]

I always sensed that the squeak was as a result of the sintered pad touching the disc when you braked?

Not sure how you would therefore prevent this from occurring?

I suppose the primary question here is why and how are copper sintered disc brake pads supposedly more superior to standard disc pads? (Especially considered that the vast majority of Lambretta disc brakes are never going to get anywhere near to the working temperature of a racing two wheeled machine going around a race track?)

[a.lo]

mine squeeled when applying brake while pushing it. had to get rid!

[dickie]

I suppose the primary question here is why and how are copper sintered disc brake pads supposedly more superior to standard disc pads? (Especially considered that the vast majority of Lambretta disc brakes are never going to get anywhere near to the working temperature of a racing two wheeled machine going around a race track?)

A very good question with 100 answers! The coefficient friction is what changes. So what is the COF of 'original' or 'standard' pads? Depends massively on what standard pads you happen to get hold of.

Personally, I found a huge difference between ebc greenstuff organic pads and ebc hh sintered pads, but that was on sports bikes. Don't get me wrong though, that was from cold when just pootling around as well as hard braking lap after lap.

You'll struggle to get COF values from manufacturers as they won't commit themselves when so many variables are involved: drilled, plain or slotted discs; dry or wet; worn or new discs; hot or cold?

Even within those sub categories, the COF can actually change with braking pressure as the pad face distorts at a microscopic level.

Bloody minefield it is.

[Storkfoot]

On this scooter, I have a second hand Vietnamese copy front disc hub. The actuating lever is an original Italian one rebuilt with new bearing and ball bearings. I have replaced the disc itself that came with the hub to another Vietnamese vented one (at the time I rebuilt the disc hub during the pandemic, I couldn’t get the better quality Italian disc)

viewtopic.php?f=19&t=15144&p=146291#p146291

Anyway, the pads I have are sintered, the type that essentially look like they are solid copper almost. I have taken them out a couple of times to clean them up, check that they are free to move and put some copper grease on the back.

The braking is good and that’s without doing a reverse pull. But the squeal at slow speeds is pretty annoying. At this point, the benefit of good braking outweighs the squeal but is there anything I can do to stop it?

[dickie]

After you removed and cleaned the pads, did the squealing disappear for the first few applications? If it did, then it's probably contamination getting onto them. It can take the tiniest amount for this to happen.

Also, is your disc drilled or plain? Drilled ones can help to keep the pad surfaces slightly roughed up and keep squealing down.

Hard braking can help too, whereas light frequent braking tends to polish up the surfaces. Maybe the slide pins are a little tight, so the disc is rubbing on the pads all the time and causing them to glaze? That last point is pure conjecture, I've never come across that being a problem, but a thought just popped into my head.

[bookertmgs1]

Had thought of that but the fixed pad only touches the end of a 6mm stud.
I'll try on the piston side,
It's a hydrolic convention btw.

I encountered this but used a 3mm shim made from some brass sheet I bought from ebay - made it slightly smaller than the diameter of the pad.

[Rich Oswald]

Mine squealed but then stopped after I reverse pulled it.

[Storkfoot]

After you removed and cleaned the pads, did the squealing disappear for the first few applications? If it did, then it's probably contamination getting onto them. It can take the tiniest amount for this to happen.

Also, is your disc drilled or plain? Drilled ones can help to keep the pad surfaces slightly roughed up and keep squealing down.

Hard braking can help too, whereas light frequent braking tends to polish up the surfaces. Maybe the slide pins are a little tight, so the disc is rubbing on the pads all the time and causing them to glaze? That last point is pure conjecture, I've never come across that being a problem, but a thought just popped into my head.

Cleaning did, as you say, help for a few miles but then it went back to what it was like before. It is a vented disc. I do still have the circlip fitted to the disc though. That said, it appears to move okay on the pins.

[Storkfoot]

Mine squealed but then stopped after I reverse pulled it.

Interesting. Presumably, that is because there is extra force immediately applied between the pads and disc

[Rich Oswald]

Mine squealed but then stopped after I reverse pulled it.

Interesting. Presumably, that is because there is extra force immediately applied between the pads and disc

Well reverse pull did make a massive difference to the braking. When I used to MOT it, the tester said he'd never tested one so good.

[missing lynx]

Have you given them a good spray with brake cleaner? Squeaking can be caused by contamination on the pads or disk also is the anti rattle clip working properly? If the disk isn't able to float under centrifugal force it will rub (squeak) the static pad

[Storkfoot]

Have you given them a good spray with brake cleaner? Squeaking can be caused by contamination on the pads or disk also is the anti rattle clip working properly? If the disk isn't able to float under centrifugal force it will rub (squeak) the static pad

I have used copious amounts of brake cleaner on pads and disc. I may as well try taking the circlip out of the disc next time I am in the hub. I’ll also check the adjustable grub screw that positions the static pad is okay. I didn’t take much notice of it before but it did appear to have a sharper point than I remember them having.

Cheers

[Storkfoot]

I have taken the circlip out, cleaned the disc and pads up again and taken it for a short test ride. Too early to categorically say that has resolved the squeak but it seems better.

[Cgt75b]

I have a spare Italian disc if you’d like to try that Paul?

But it sounds like you may have cracked it.

[dickie]

I once had a disc that didn't float on the pins properly. The fix was to bend the spring into a tighter radius. Basically the spring was applying too much force on the pins. Maybe you could do the same rather than leave it out?