I didn’t read Bobs question as negative, I wouldn’t be too tough on him as I had the same queries actually, which you have explained well here. I didn’t know much of what you have set out and will check my brake fluid as it is probably as old as the car (MY18). The air here isn’t overly humid, but the climate is damp (it rains a lot) which may affect things. I think this job is on my list though, if not for immediate use, certainly a good mod for future proofing the car, as like you, I think I’ll be keeping it for quite a while.What's up with you insisting that I justify my installation of speed bleeders to your satisfaction? You already have your mind made up negatively about speed bleeders, throwing out a murky critique, to wit: "In the motorcyclist world, they are not well respected." As a motorcyclist who is in the motorcyclist world myself, you are the first I've heard to level that broad and non-specific charge from vague and non-specific persons who aren't part of this forum. Nothing I can say to you will change your pre-formed opinion, so I distrust your motives and intent in asking for further justification.
I'm going to respond in more detail, even though you are trolling me, for the benefit of other members who may be confused by your non-specific beef with speed bleeders and, apparently, those who install them.
As I said in my How To thread: "Speed bleeders have a check ball that doesn't let air flow back into the caliper when you release the brake pedal during the bleeding procedure. This means you don't need a helper to pump the pedal while you tediously open and close the bleeder valve at each caliper, calling out "Down!" "Down!" "Up!" "Up!" innumerable times to each other." After installing speed bleeders, I completed my first non-spouse- / non-offspring-assisted total automotive brake bleed. Isn't that reason enough for any enthusiast?
How often do you need to bleed your brakes? Glycol-based brake fluid is hygroscopic, meaning that it absorbs moisture from humid air. The brake system is not perfectly sealed off from atmospheric contact, so ambient moisture is absorbed by the brake fluid. This lowers its boiling point, which could lead to brake fade if the dissolved water turns to steam in the brake lines. This is something that is a consideration in a sports car that is driven with hard and continuous brake use.
Further, the moisture in the brake lines causes corrosion. Corrosion can cause brake caliper pistons to stick, leading to brake noise and / or premature or uneven brake pad and rotor wear. Corroded calipers can damage rubber seals as they scrape across pitted surfaces, causing fluid leaks. Eventually, corrosion can eat through brake lines, causing total loss of braking pressure which could of course be catastrophic. I have had that happen to me with an older vehicle once; thankfully it was in my own driveway but I never want to have it happen again.
It's easy to see a color change in brake fluid as it absorbs moisture: it changes from a clear very light color to an increasingly opaque and darker amber color. As a motorcyclist you should know that's why handlebar-mounted clear brake fluid reservoirs on motorcycles are called "urine specimen jars". When the brake fluid gets old and full of absorbed moisture, the reservoir looks like a jar of piss, which motivates the rider to bleed the brakes to stop the embarrassment of riding around everywhere looking at a jar of piss on their bike.
Many here have noted dark green particles and residue floating around in the reservoir. A senior contributor here, whose knowledge and experience I greatly respect, said that it was likely copper oxide from corrosion inhibitors in the brake fluid. If you are seeing the byproduct of spent corrosion inhibitors in the reservoir, that means corrosion processes are at work and the sacrificial inhibitors are being consumed. Once they are all gone, the brake system components themselves will get consumed. In my view, the appearance of these residues is an immediate indication that the brake fluid needs to be replaced.
Note dark amber color and cloudy appearance of this brake fluid (cause: water absorption) as well as the greenish residue of spent copper corrosion inhibitors:
Regarding the construction and design of speed bleeders: they are constructed exactly like standard bleed valves in terms of how they completely close off fluid flow when fully seated. They essentially act like a plug, same as standard bleed valves. The only difference in operation is when they are cracked open. The spring-loaded ball is simply a one-way check valve; it lets fluid out but closes to prevent the backflow of fluid and/or air into the caliper. Ball check valves are used in millions of applications all over the world and are "well-respected" by innumerable engineers for their low cost and simplicity.
The fact that speed bleeders are available in stainless steel is a real bonus: no chance of a rusted / seized bleed valve getting stuck and breaking off in the caliper. If that happens, you either have to extract the broken stem - potentially leaving metal particles inside the caliper - or replace the caliper. During a broken bleeder extraction attempt, if you generate particles that fall inside the caliper, you would then need to disassemble the caliper to clean it out before re-installation or else risk seal damage or piston sticking as a result of the metal debris.
Another speed bleeder benefit I noted: the bleed ports were larger for greater flow. This is a subtle feature that further eases and speeds the bleeding process.
So, how often do I "need" to bleed my brakes? As often as necessary to minimize the opportunity for water in the brake system to corrode its components. In practice, for me this means ideally every year but at most every two years in my climate. But, no need to take my word for it. Here are some words from an automotive industry professional:
Speed bleeders make the job so much faster and easier that there's no reason not to do it annually, for example when the wheels are off to rotate tires or to perform a brake pad inspection. Speed bleeders are even more useful on an automobile than a motorcycle; on a bike, you can open and close the bleed valve with one hand while operating the brake lever or pedal with the other. On a car, this is not even possible.
I'm planning to keep my Spider for a long time. I don't want it to become like the 124s of old, with corroded and defective brake systems that caused their owners to park them, never to be driven again. My one-time cost here was $71.95 for the speed bleeders, bleeder bag & hose combo, and shipping. My variable cost was about $10 for 24 oz. of DOT 4 synthetic brake fluid, so about $82 all-in for a DIY brake fluid change. The next fluid change will cost me $10.
My questions back to you @Bob T: 1. What's your problem with $10 a year brake fluid changes during the ownership of the vehicle? 2. How infrequently do you bleed your brakes and why do you need to bleed them so infrequently?
Editorial comment: It's people like you who make it frustrating for other people to post here about things that they've done to their cars. Nobody wants to share something cool or fun or useful when they have to put up with irritating nits and picks and digs from the likes of you. I saw your snarky comment just today regarding someone's choice not to paint their turbo bracket red, when the blanket itself was already red. It would have looked naff to have both of them red. But besides that, why badger the person and be a killjoy? This kind of rude commentary is how enthusiast forums like this lose enthusiasm.