Recent comments about “wooden brakes” and the like from other parties encouraged me to investigate the Aprilia’s braking system. The rear brakes had been re-lined and wheel cylinders refurbished only a couple of years back so my attention turned to the front pair.
The shoes had been re-lined and the wheel cylinders sleeved back in 2008 but an inspection revealed all was not well in there. Both wheel cylinders were leaking and pretty much seized and the linings had virtually no wear, after 8 years something was very wrong.
Leaking cylinders and linings with very little wear after 8 years!
On to the Cavalitto website to see what parts they had for brakes:
Two new front wheel cylinders and a set of brake linings were despatched via UPS
New linings and new alloy wheel cylinders
The shoes went of to BGT to get re-lined. Here I was advised not to use the supplied rivets but to bond the new linings. I don’t know why but they always coat the nice alloy shoes with some yellow/brown gunk that won’t come off, I guess no one sees them but I far and away prefer the clean alloy look.
New Cavalitto linings bonded to shoes
The new cylinders were bigger than the old Lockheed originals, about 10mm longer and the piston 3mm greater diameter but I was assured by BGT they would be fine, just give a ‘higher pedal’
Top; new wheel cylinder, bottom old Lockheed cylinder
Old Lockheed cylinder
New Cavalitto wheel cylinder
New wheel cylinder and re-lined shoes
After fitting the new cylinders and shoes, bleeding the system using the one person bleed method and adjusting the shoes the first test drive revealed all was not well; the brakes were not releasing correctly and partially locking on! After much head scratching, more bleeding and adjusting the problem didn’t go away. An email was fired off to Cavalitto with the reply to make sure everything was cleaned with alcohol and the workshop manager would get back to me after the weekend. Advice from Puce Goose & Stainless Stephen thought muck in the master cylinder would definitely be the problem, what do they know?? I thought maybe the flexible brake lines were blocked or collapsed. In a moment of rational thought I phoned Mike the Three Wheeler, automotive engineer extraordinaire who lives not that far away. He was going to be driving past the next day and could stop for a look. Mike’s diagnosis was the master cylinder residual pressure check valve didn’t need to be there with the new wheel cylinder piston seals.
New wheel cylinder with modern seals
Removed the master cylinder from the car, always a fun job with not much room, stripped it down, found the inside to be spotless, and removed the inner rubber from the check valve.
Master cylinder hiding underneath the car
Rubber valve removed from residual pressure relief valve
Reassembled the lot, bleed the system again and adjusted the shoes. This time the brakes didn’t seize and stopped extremely well. A nice progressive pedal with room to heel and toe, and pulled up in a nice straight line. Once the linings are bedded in they will only improve, but right now its are the best they have ever been. A reply from Cavalitto on the Monday said new return springs for the shoes would have helped and probably worked, but doing what Mike suggested was also ok.