The long slow build of my strada continues despite many domestic interruptions and an frustrating lack of time to work on it.
I've recently sourced a replacement disc, originally from a Ducati or Laverda it should fit straight on, it is cast iron as far as I can tell so will be permanently rust coloured unless I can clean it up a bit.
What would the easiest way to do this then?
I was planning to paint the carrier black and just leave the swept area alone but the casting in the inside 'arms' of the disc is very rough and wont be easy to clean, - paint over it and dont worry or try and clean it as best I can ( how would you do it) ?
Also...
Can anyone also tell me what size the ball bearings needed for the steering head are?
I need 42 and there was less than that when I removed them.
"The problem with quotes on the Internet is that you can't tell whether or not they're genuine" - Abraham Lincoln
Another technique would be to bead blast the entire disc then paint the nonbraking surfaces. The bead blasting is a recommended way of removing the glazing from prior pads anyway. It also works great at cleaning up the rough surface areas. I just did this to my Dart 350 after the Bonneville salt flats.
Jarl
1985 350 K2, 1978 500W, 1979 500W, 1983 500 Sei-V, 1982 250-2C, 1977 125H, 1953 175GT
1990 Dart 350
Moto Madcap
Falling Waters, West Virginia USA
Holds AMA Records at Bonneville Salt Flats
A question for you while you have the disc off.
Can you stand each disc face down and measure the height of the stand-off or 'dish'? I have seen results posted with results saying 'straight swap' and also 'had to file down the forkleg and spacer to allow the caliper to fit', ie. the disc comes out a little closer to the forkleg. Would be useful to know when new disc time comes.
Thanks.
Now in addition to the earlier answers.
If you want to go either the zinc or paint route, get yourself a bottle of phosphoric acid off ebay. Pour some into a bowl of water to make up a mixture at about 10% strength and leave the disc to soak in it. After about 2 days it will come out looking like new. Rinse with some washing soda and it will be ready for either painting or plating.
(It isn't a dangerous acid - it is in most 'cola' type drinks at about 1%, and is the ingredient that makes coins come out sparkling when left to soak for a while in coke. Just use normal sensible precautions when using it. Also always add acid to water, not water to acid.) Also keep it away from anything aluminium.
If you go the plating route, seek out your local zinc platers and ask how much they charge for a 'bucket of bits' to be done. I got 2 bucketfuls of bits replated for £40 down in Essex near where I work. I did all the miscellaneous bits like chain adjusters, carb screws, wheel spindles and spacers, clutch lever mount, cable guides etc, as well as lots of the nuts and bolts from around the bike. All cleaned up beforehand in the same acid bath. Makes a huge difference to the appearance when you put it all back together.
If you decide to paint, use manifold paint as the disc will get VERY hot in use and normal paints will soon bubble up and look horrible.
George.
George
350 sport 1978, 350 Strada 1978
650 Norton 1967, 650 Kawasaki 1977 and 650 Enfield 2019
You could try paint stripper, any DIY one will do and wire wool, I used black enamle for the paint and stayed on well. As already said check darmah disc for offset. Hope this helps. Muller
A question for you while you have the disc off.
Can you stand each disc face down and measure the height of the stand-off or 'dish'? I have seen results posted with results saying 'straight swap' and also 'had to file down the forkleg and spacer to allow the caliper to fit', ie. the disc comes out a little closer to the forkleg. Would be useful to know when new disc time comes.
Thanks.
Just managed a quick look and the new discs are 2mm higher than the OE ones so a 2mm shim on the caliper mounts should match that I think.
"The problem with quotes on the Internet is that you can't tell whether or not they're genuine" - Abraham Lincoln
You will need to REMOVE 2mm from the caliper mounts not add
One of the mounts uses a thick washer which can be replaced with one
that is thinner
The other mount will require taking material off the caliper.
I used a bench grinder.
I suppose as George has mentioned you could take the material
from the fork leg ... But as the calipers are still available
they seemed the most logical to modify incase of error.
mgill wrote:You will need to REMOVE 2mm from the caliper mounts not add
One of the mounts uses a thick washer which can be replaced with one
that is thinner
The other mount will require taking material off the caliper.
I used a bench grinder.
Mathew
Ah, does it bolt to the inside then?, its been over a year since I've dismantled it and I haven't even looked at the caliper yet.
"The problem with quotes on the Internet is that you can't tell whether or not they're genuine" - Abraham Lincoln
i thought i would throw a spanner in the works, instead of grinding off calliper , how about taking the hub of the disc down so it moves over, a lathe would be needed and some way of setting it up, maybe take 2mm down, there still should be plenty of metal left to support the bolts or have i lost my mind! tell me its not true.
I have to say that sounds like a really logical solution - BUT - is the carrier somewhere you'd want to make thinner? Will losing 2mm matter? Just being the Devil's avocado.
Dom
I really can't be comfortable with 'hacking' metal off of the caliper mounting. The mountings need to be co-planar (to each other and to the disc) and decently flat (full contact, not partial) to avoid putting stress into the caliper, or allowing flex on the mountings. Production tollerances tend to be much better these days, but it used to be quite common to shim calipers to achieve all this.
Machining brake discs, particularly used ones, can be really tricky to do without introducing run-out. I think the safest surface to machine would be the wheel. You're not losing any strength is that area and it's an easy setup (albeit requiring a lathe of substantial swing). You'd have the option of easily returning to OEM discs with a spacer.
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
