So, after Donington last year it was pretty apparent that my discs weren’t looking too happy.
They were looking even LESS happy when I removed them on Friday:
Just as well these turned up then!
Reyland 335 x 28mm J hooked discs.
I’m well aware that the Reylands are a cheaper option, and that they’re not curved vane, but I’m keen to give them a try and see if they will work for me.
The friction surfaces of the compbrake rotors were 6.5 and 5.5mm, outside and inside respectively. With an air gap of 16mm.
The main problem as I see it, is that the grooves machined in are very deep, and run right to the edge of the disc, meaning there is a very thin section at the end of each groove, and that’s exactly where they have cracked.
Each disc had 3-4 of these cracks, both front and rear, so they really were absolutely ruined, hence me not tracking the car at all this year.
Here you can see how thin the ‘plates’ are on the compbrake disc:
This is apparently to keep weight down, and also apparently they are designed primarily with rally use in mind, with a large air gap for maximum cooling and less chance of the vanes getting clogged by debris on stage.
The Reyland rotors have ‘plates’ of almost 9mm thick each side, with a 10mm air gap.
Whilst this means they are heavier, it hopefully means that there will be more metal to dissipate heat, and far less chance of cracking hopefully.
The old discs were looking REALLY crappy generally when I came to remove them:
I removed all the bolts to separate the discs from the bells:
I loosely wire brushed all the bobbins and bolts first:
Before soaking them overnight and all day Saturday in white vinegar, something I’d been told is excellent for cleaning and removing corrosion etc:
After a good soak, I spent a further 3 hours carefully wire brushing and cleaning up each individual bolt, bobbin, and nut. This was NOT fun.
With them all cleaned, I put them in groups into a paint can lid, and sprayed them liberally with silicon PTFE lubricant which dries and leaves a PTFE coating. Whether this will last, or be fried off immediately I’m not sure, but it seemed worthwhile when assembling anyway:
Then, as it was raining, I assembled the discs, bells, and bobbins, and torqued them all to 11lbft as recommended by AP:
Rich, who maintains the autotech TT recommended to me last year that after building up a disc, make sure it is freely floating by rattling it to ensure it moves freely on the bobbins.
I did this on the first disc, and it rattled nicely:
I tried on the second one, and it was silent. Eek.
By a process of elimination, I worked my way around the disc, and it was fairly easy to feel which of the 12 bobbins wasn’t moving freely. It would float if forced, but not freely at all.
I undid the troublesome bobbin, and as expected, I found a tiny bit of corrosion proud of the face on just one side. This was only around 0.2mm or so, but it was enough to lock up the disc.
I filed it back, and recoated in the PTFE spray, and torqued up the bolts, and this time, the disc floated and rattled nicely. Job done.
I've recently started a new job, and we've booked our wedding, so there is much going on there at the moment. As well as trying to get things in place for the garage as I've not had time yet this year. Hopefully the garage shall make some progress in the next month.
