Repro disc brake problem

[superhooper]

Hi peeps, I have repro front disc brake (bought from Cambridge Lambretta so assuming it's a Tino one)
The problem I have is when braking it has a kind of grab/let go feel to it almost like 'kangarooing' when spinning the wheel whilst scoot is on stand & rotated it runs freely for approx 1/2 to 2/3 of a turn but makes contact with the pads for the rest of the turn. I suspected a warped disc but on removal & inspection the disc looks flat in My eyes ( I held if onto a pane of glass in shed and no rocking occurred) Could the problem be the disc isn't sitting properly on the pins? Any help remedying this would be most gratefuly received.

Cheers Super

PS the pads look to have worn evenly

[bike grim]

Try enlarging the holes on the disc a little bit. Get some fine wet n dry paper and smooth the three pins clean them off and add a smear of coppaslip to each pin. Worked for me.

[coaster]

Try enlarging the holes on the disc a little bit.

I think it is recommended to run a drill bit through but I'm not sure what size though but someone will. Mine was doing the same and I just used a small sanding drum in a dremel and applied a little copper grease to the pins. It is only a nuisance when pushing the scoot, the disc will centre itself on the pins when you start riding unless its very tight.

[superhooper]

Just checked the disc on the pins & they are VERY tight Evan after removing the anti rattle circlip, also they is some paint residue on the pins. Just looked in Stickys manual & it suggests drilling holes out to13/32 of inch & retain clip. I'll get an adult to do that & post results. Thanks for help!

Super

[nsaints]

I had an issue with a repro disc recently, and think it’s cured now. A few 100 miles will prove it.

My disc was fine as I took it for it’s first MOT in Oxford, about a 15 mile journey, it on the return at a set of traffic lights the front end bounced up and down on the suspension. It wasn’t something you could live with, it was pretty bad.

Someone mentioned it could be cheap pads, and as I had a spare set when I replaced them ensuring they didn’t bind in the hub holes and had plenty of clearance. But also I throughly decreased the disc Incase it was contaminated with oil, and cleaned the paint off the pins. Spent a good two hours cleaning and ensuring the pads fitted perfectly, and disc didn’t bind.

Made zero difference, still awful braking with the front bouncing on braking

It had to be the disc and I needed to get it machined, but first someone in the club had a spare innocenti disc I could try and prove it was the disc 100%

Bingo cured the issue straight away.

Posted this up on our clubs FB page and Pete who knows metal through his job stated that it’s likely as the disc was fine initially but quickly warped it’ll be low quality Far East metal. Pooly manufactured and heat treated. I could have it skimmed flat, but it’d soon reverted to warped again. Pete committed it’d be fit only for the bin when I mentioned it lasted 15/20 miles before starting the weird bouncing up and down thing.

So what I’ve done is bought an evergreen disc from scooter Centre. Just the internal disc. It needed 5mins on the internal diameter with the dremel. And braking is fine now.

BTW. My disc wasn’t bought from Cambridge Lambretta.

Edit: I’ll add whilst I was trying to work out the issue, I’d ridden the scoot to get it dyno’ d. Whilst there we mounted the disc on a lathe, but as it ran up to speed in the lathe it appeared to run true, so we didn’t bother machining it and thought it must be the pads, and went down the replacing the pads route up there ^^^

[Knowledge]

Just looked in Stickys manual & it suggests drilling holes out to13/32 of inch & retain clip.

Just in case some reads this and mis understands: remove the circlip, drill it out, and then refit the circlip.

I have a drill press Roy, if you want to buy a drill off eBay. It has only got to do three holes. I have a few reams, but I am not certain that any are that specific size.

[superhooper]

Cheers knowledge, gonna have a look if I have correct drill bit. Must add I have done about over 2000 miles with this hub. It's sporadically not to bad then for no apparent reason it's worse than abismal. Gonna try cleaning drilling first but I have another disc brake I can take disc out and try.