Had to have new discs fitted all round (15K miles) not warped just worn out...out of warranty too, dammit anyways, braking performance was absolutely shite, numb, no bite, no power.... no idea what pads they fitted, so dug around on the forums and found a recommendation for these Product/Description BREMBO 07-BB-38-SC ROAD/TRACK SINT F PADS Code: 61611 Qty Ordered: 2 ordered from bikehps.com...great service difference is massive, plenty of power and feel...would also recommend! if only the lever action was better, i also experience what a lot of people mention on the forums in that there is far too much lever travel before the brakes actually take action, then a second pull on the lever seems to "pump up" the system and the actuation of the brake is much sooner in the lever travel. most fixes seem to be expensive replacements of the master cylinder :/ spent far too much on the thing already and a desmo service is looming later in the year. anybody got a cheap fix (apart from the zip tie on the lever thing)??
it's the SP so steel hoses already there, but I agree, it's probably overdue a strip down service... nervous about bleeding brakes on an ABS system though...i have the manual but there are no words on how to do that properly
On cars you are supposed to use a diagnostic tool to carry out a brake bleed routine, which activates the ABS pump to push fluid through. I suspect it'd be the same for bikes surely, although I can't imagine many dealers doing it if it's just a quick brake fluid service (bleed old fluid out). Maybe your new setup just needs more time to bed in?
I rate the brembo SC pads, I've fitted them to the front of every one of my bikes for the last few years and have always noticed an improvement in bite and stopping power. If you don't want to do a full bleed I would just remove the reservoir cap, clean everything up with brake cleaner to remove any moisture and then crack each bleed nipple with a bit of hose on it and give the lever a tiny squeeze just to see if you get a bubble out. The one on the top of the brake lever is a prime candidate for any air in the system
Maplesyrup...thanks for that advice...will give it ago I think the SC pads might be my new favourite... what's your experience on longevity? the standard pads on the SP lasted about 14K miles
I got about 6000 out of the stock brembo pads on my S1000RR and roughly the same out of the SC but the braking performance was greatly improved for the same milage. Probably not the best comparison to my Hypermotard as the BMW had little engine braking and therefore ran really hard on the brakes into corners but I'd expect to see similar milage to the stock pads when I fit them to my Hyper, possibly at the expense of greater rotor wear but that's no major concern to me.
I'm sure no ones that interested but I smashed my 939 SP up a couple of weeks ago on my brothers birthday, I'm fine, but am desperate to get it back from the dealers and put some fecking miles on it!
Thank you! Im just waiting for a "completion date" from the dealers, they've ordered all the parts from the factory and have been very good, I hope you get the brake feel sorted.
A quick and dirty way to improve lever feel is to tie wrap the lever in the fully depressed position overnight. This allows any minute bubbles to travel up into the reservoir rather than staying suspended in the fluid. It usually makes a surprising difference - just be careful not to wreck your grips.
Funnily enough, there is another thread busy discussing this at the moment: http://ducatiforum.co.uk/threads/brake-bleeding-and-the-cable-tie-trick.49337/ The consensus is that it is indeed "quick and dirty" (and perhaps temporary) as it dissolves small bubbles! I don't think they can travel up into the reservoir, because when the lever is depressed it has sealed off the port between reservoir and brake cylinder. I'd start with the quick basic bleed at each nipple as per Maplesyrup's recommendation.
It doesn't dissolve the bubbles. Air doesn't dissolve under pressure. It compresses. Hence air compressor rather than air dissolver. Once the bubbles are under pressure, they clump together and travel upwards thanks to gravity. You're right in saying that they don't escape into the reservoir straight away as it is indeed closed but they come to rest at the highest point in the system (the caliper side of the master cylinder) so when the lever is released, they end up back in the reservoir where they should be... It doesn't work 100% hence the quick and dirty comment but it does usually make a pretty big difference.
I think you should join the debate on the other thread! I suspect that in fact there is a combination of factors at work here. Air both compresses and dissolves (more) when under increased pressure, although I guess brake fluid does not allow nearly as much to dissolve as, say water can take. I don't think pressure makes bubbles more likely to merge though. One further credible point I've seen is that compressing the bubbles will make them smaller and thus may help them to get past obstructions and float up to the top of the system where they just might escape through the port at the master cylinder, into the reservoir, when the cable tie is released. I've certainly used the method after installing new lines and seen some additional small bubbles emerge into the reservoir after gentle movement of the lever in the morning, after having left the lever pressed overnight. I have no faith in the explanation provided by HEL: Bleeding HEL Performance brake lines where, although there is generally very sound advice, the explanation is supposedly "basically the back pressure caused by tying the lever back overnight will have forced any last remaining air out of the system out to the atmosphere and leave you with sharp brakes the next day" ?!
Will do, what's the other thread called? If we're going to get into detail, we need to think about the pressures and temperatures at play here. We're talking about putting the fluid under a modest amount of pressure at whatever the room temperature is (say 15degC). We're not talking about putting it under 20,000psi at 90degC... So with that in mind, the ratio of air dissolved under modest pressure is tiny compared to the ratio at which it is compressed under modest pressure. So largely speaking, for the sakes of this conversation, air compresses under pressure. If you ramp up the pressure (or temperature) greatly then yes, you will start to dissolve air. By dissolve I mean convert the gas to a fluid. The problem here, and the reason why I didn't agree originally, is that once you release pressure, the liquid "air" will turn back into a gas (when equilibrium is reached). The air clumping together is legit. Think about the Specific Gravity of the fluid vs the density of the gas (air). Pressure as an acting force will separate the 2 substances just like gravity separates oil in water... My knowledge is in mechanical stuff rather than chemical so I'm about at my limit here but the above few comments are my understanding of what's happening when you tie your brakes up overnight. :thumbsup:
The other thread is titled "Brake Bleeding And The Cable Tie Trick". As I did Chemistry at A level I feel compelled to continue the debate! Air doesn't become a liquid unless subjected to huge pressure, but it can dissolve easily, with its molecules mingling with those of a liquid, like water. A good example is the gas in a bottle of soft drink (CO2, which is part of air anyway, although a lot more soluble than the Oxygen and Nitrogen). Also, the pressure in a braking system is a lot more than atmospheric pressure, due to the leverage at the master cylinder. I can't find any reference to typical motorcycle brake line pressures, but I think they are tested to around 4000 psi (vs atmosphere at 15 psi). Even with gentle pressure at the cable tie, I'll bet that the pressure is several times atmosphere (15 psi) and Henry's Law (which I am no expert on!) means that that a significant amount more gas will dissolve when that pressure is exerted. I agree that gravity will have exactly the same affect as with oil and water, and bubbles of air will rise to the top of the system, if unobstructed. The pressure does not move them upwards or downwards though, or closer together, but I do think it will make them a little smaller (because air is easily compressed under pressure, unlike brake fluid).
this is very interesting.. so based on the last couple of messages, i would conclude that a "normal" brake bleed should be conducted after some "rest" period, which would allow any air bubbles to come out of a dissolved state, thus giving the best opportunity to purge air from the system?? a brake bleed attempted after pressure had been applied to the system may not result in any noticeable bubbles being eliminated since they have been dissolved/absorbed by the brake fluid
Good point. I've even seen suggestions in other forums about de-gassing brake fluid before using it (by subjecting to vacuum in syringe for instance!). Also, it seems that DOT 5 Silicone fluids (not used in Ducatis as far as I know) tend to dissolve a lot more air than DOT 3, 4 or 5.1 glycol fluid. Taking all into account, I think the best sequence might be: - Replace fluid with fresh, ideally from a sealed new bottle, or at least a previously used bottle which has been kept properly capped and not shaken up. Do an initial bleed, but that's part of the fluid change anyway.. - Leave overnight without any lever pressure, for bubbles to rise/combine to some extent. - Bleed again. - Then over the next night use the "cable tie trick" and see if it helps! - Perhaps one more quick bleed. Not much more you can do.
Completely agree that it doesn't become a liquid unless subjected to huge pressure, that was my point. I realise that the MC will exert some pressure but when we're talking about converting air from a gas to a liquid, the pressure at the MC is completely insignificant. My best guess would be that a good Brembo MC coupled to a decent set of braided hoses would be able to exert something like 100psi. Definitely not enough to dissolve air (by my definition of dissolve anyway). I understand that CO2 dissolves very easily as I brew beer in my spare time and dissolving CO2 post fermentation is essential to get that nice bubbly mouth feel... Getting back to the debate, I think we need to recognise that there are 2 entirely different types of air that can be in our lines. The following was stolen from an article about brake fluid solubility: The term “dissolved air” (air absorbed from the atmosphere) should not be confused with the term “entrapped” or “free air” since their effects on brake system performance can be entirely different. Air that has been absorbed from the atmosphere does not result in an increase in fluid or system volume, whereas entrapped air or free air does occupy system volume and can be easily compressed when force is applied to the system. What we worry about when we come to do a fluid change is the "entrapped" air and when I'm speaking about compressing rather than dissolving, I'm speaking about the "entrapped" air, not the small percentage of dissolved air that's already a part of our brake fluid. In a round about way, I think we've pretty much come to a consensus... The cable tie trick works by encouraging the air to move up the lines by applying pressure to the fluid which already has a significant differential density to the air. The air then forms a clump of sorts at the highest point of the system, under the MC. When the cable tie is removed, the air is allowed to escape thus improving the lever feel of the brake system. Agreed?
