Aside from the LC, another of the bikes I'm working on (the VFR this time) is having trouble containing some of its fluids - brake fluid in this instance. My initial thought was that the brake lines I've made up for it had failed, but that wasn't so. It was the calipers that were leaking, and as I'd modified them, I was pretty sure it was a self-inflicted wound. It was...
What I haven't mentioned is that apart from non-OE forks, brake calipers and wheel, the brake discs are also non-OE, in fact I've never seen another pair like them. They were an ebay purchase from someone who had very little idea what they were. They are a full 320mm diameter (RC30 OE are 310mm) and are not only drilled axially, but also vented radially. They are also ductile iron (not stainless) and came with magnesium carriers, FFS. As a consequence of the radial drilling/venting the discs are noticeably thicker than normal, measuring about 6.7mm. 'Normal' discs all tend to be about 5mm thick when new. This means that caliper to disc clearance is marginal, to say the least, and it quickly became apparent that if I wanted to use my 4-pad Brembos with these discs that this clearance would need to be increased.
So I got in touch with one of the 'makers' on the Mig welding forum I also frequent and asked him if he could laser cut some distance pieces from 1mm aluminium plate. 1mm doesn't sound much, but it would make the difference between unwanted contact and spinning freely. Matt was optimistic he could do it so I sent him the caliper halves for him to assess. He replied in the affirmative and sent me these photos of the parts he'd cut. Perfect.
- 1mm_inserts_for Brembo_caliper.png (317.9 KiB) Viewed 536 times
He'd also mounted them up to a caliper half so I could check the fit, and all looked exactly what I wanted. To top it all off he only charged me the excessively reasonable price of £30 inc. P&P. Bargain!
- 1mm_inserts_fitted_to_Brembo_caliper.png (334.09 KiB) Viewed 536 times
What I now needed to do was to find a larger o-ring to make the seal between the two caliper halves. The extra 1mm I'd added to the area to be sealed meant I needed an o-ring with a substantially larger cros-section. The only one I could find that matched my requirements in EPDM was 2.62mm cross section, 10.47mm outside diameter. This fitted the hole perfectly and would hopefully be chunky enough to seal the two halves.
You can probably guess where this is going by now...
So the caliper halves were reassembled with the distance pieces and heftier o-rings installed, pads and retainers fitted and then bolted up to the bike. Then it was time to fill the master cylinder reservoir with brake fluid and start the tedious bleeding process. I tend to use a syringe with hose attached to the caliper bleed nipple to draw fluid down from the reservoir. So I was well placed to observe the drip drip of brake fluid onto the floor coming from the brake caliper. Bugger. Panic stations ensued as I tried to minimise the spread of brake fluid to wheel, pads, disc, tyre, floor etc. etc. I hate brake fluid - nsaty stuff.
So now it was back to the drawing board. Larger cross section o-rings of that o.d. simply aren't available, so the only way I could seal the two caliper halves was to make a gasket out of 3mm EPDM sheet, using two hollow punches - a 10mm and a 5.5mm. This would give me a wider sealing area and a larger cross section. And as I'm a believer in belt and braces, I also used Threebond TB1215 RTV instant gasket on both caliper faces. The calipers were then torqued up to 25Nm and left on one of our radiators for a couple of days to cure.
And I'm relieved to say, that appears to have cured the problem. I bled the brakes without seeing any fluid leaks and have left the system under pressure with a rubber band around the brake lever and throttle grip. If there are still no drips when I check tomorrow I'm calling that a result.
There is no cloud, just somebody else's computer.
