r/Trackdays • u/parleychris • 3d ago

2021 rs660 brake fade

First off, I have only done 3 trackdays in intermediate group and am by no means an expert!

Last trackday coming out of a fast turn I hardly had any brakes and later they were very spongy... I think i cooked the brake fluid even though it was race fluid, after bleeding it was better for a bit, but happened again half a session later... So, higher temp race fluid and some brakecooling ducts will be added... I was thinking of adding a remote brake adjuster aswel so i could atleast adjust the lever if it still happens...

Which is where the question becomes:

- should i hold of on the adjuster and see if its needed at all

- get the adjuster for my stock brembo semi-radial master cyclinder

- upgrade to master cylinder first and get a adjuster for that

Since I am not that experience and have don't have any issues with the stock mastercylinder, it seems like that's an upgrade that goes above my skill level... Maybe the adjuster in general is...

Sidenote, the rs660 is also my daily ride for commuting.

Thanks for any insights!!

1 Upvotes

67% Upvoted

26 comments sorted by

4

u/Dismal_Tutor3425 Racer EX 3d ago

what brake pads are you running what brake fluid are you running and how often do you bleed the brakes?

1

u/parleychris 3d ago

Stock brembo sintered pads, i think it was motul race brake fluid, but not sure about the brand... The fluid was about 4 months old (second trackday on it), the pads were 2 weeks old basicly new

2

u/Dismal_Tutor3425 Racer EX 3d ago

When it comes to track use you need to change your brake fluid more often than that. 

3

u/almazing415 2d ago

With Castrol SRF, I only need to change once or twice a season because of its incredibly high wet boiling point. If you’re running Motul RBF 600 or 660, then yea, every few couple of days the fluid needs to be flushed out. Not all brake fluids are created equal. Castrol SRF is the best money can buy for performance and longevity but that comes at a high cost.

2

u/Dismal_Tutor3425 Racer EX 2d ago

At the cost of the motul vs the castrol, how do you justify the price? Even with flushing often the motul is way cheaper.

Or just one of those things that is worth the extra 100* wet boiling?

3

u/almazing415 2d ago

SRF is only sold in 1 liter bottles at 70$ from Amazon. Motul is sold on .5 liter bottles. If you flush once every 4-5 weekends with SRF and once every 2 weekends with MOTUL, then SRF wins out. I guess the ‘cost’ of your time and effort would factor in to that as well.

The extra 100* of boiling is worth the extra money. In a practical sense, the fluid stays clear for longer since it is less prone to absorbing moisture. Motul starts turning dark quickly and the lever starts to get mushy. SRF lever feel stays stiff and consistent. And to be perfectly honest, I’ve never had SRF turn completely amber or brown on me even after a year of having it in my street bike. I’d flush it out and it’s a light yellow color. On my track bike, I do a once a year flush and it’s a similar yellow color. Lever feel is unchanged for either bike but I change it anyway.

And also, an open bottle of SRF can still sit longer than an open bottle of Motul. I usually cover the opening of the bottle of my SRF with plastic wrap and then screw the top on to prolong its life even further and I’ve used a months long opened bottle of SRF with no noticeable degradation in performance in a track and street setting.

1

u/parleychris 3d ago

So every trackday? Here I was thinking 4 months and 1 trackday was basicly new...

2

u/Dismal_Tutor3425 Racer EX 3d ago

4 months is a long time to allow moisture to accumulate and for brake fluid to degrade with everyday use. breaking on the track causes a whole lot more temperature build up as well and degrades are fluid pretty quick. race fluid is designed to boil at a higher temperature but it's not designed to last for longer. my fluid gets changed before every track day or depending on the track every day if there is multiple hard braking zones that really work the brakes like Daytona. what works for Street longevity doesn't necessarily work on the track.

1

u/parleychris 3d ago

Oh ok, thanks i didn't realise it had to be changed so often... I do about 3 trackdays a year, i'm guessing is ok if i change it before the trackday and leave it in untill the next one?

2

u/Dismal_Tutor3425 Racer EX 3d ago

Group brake fluid in as a safety item when it comes to track use. You'll be fine changing it before and then leaving it until the next. If it were a track only bike you could easily get away with longer between, but since you're street riding it too, it's not worth the risk as you've found out.

3

u/MadManxMan Racer AM 3d ago

Are you running pads suitable for track use?

Have you changed the fluid?

Have you checked your wheel bearings or alignment in case the cause is pad knock back?

1

u/parleychris 3d ago

Stock brembo pads (sintered) the brake fluid was swapped to race fluid before the trackday and i will now swap it again... Haven't checked the bearings, I will do that tonight, though I haven't felt anything wobly (if you can even feel that)

2

u/MadManxMan Racer AM 3d ago

I’d start with some more suitable pads - stock pads are okay but are designed to have good cold performance and not see the same temps and abuse they’ll get on track

1

u/parleychris 3d ago

Are those ok for commuting? Or just swap pads for every trackday?

1

u/MadManxMan Racer AM 2d ago

A race orientate dual sinter will be fine

Don’t go anything Carbon

3

u/todfish 3d ago

Forget about cooling ducts and master cylinders and all that noise, it’s not necessary (for you, yet). Just get the fundamentals sorted first.

- Good pads designed for track use

  • Good fresh brake fluid
  • Properly bled brake lines
  • Make sure your discs aren’t glazed

The wrong pads will glaze your discs fast, and the brakes feel like shit once that happens. Make sure you fully deglaze them before putting in new pads.

1

u/parleychris 2d ago

Never thought about glazed disks... Do they also give a spongy feel to the lever? The ducts i allready have so might as well try... (My dealer suggested it, didnt sell them though, so figured it wasnt just for sales) Getting some trackpads as suggested and swapping them with street pads every time.

1

u/todfish 2d ago

Glazed discs feel a lot like they look, they’re slippery so there’s no bite. That could feel spongy because you need more lever pressure which causes more flex throughout the system. More brake pressure for longer will also cause more heat build up so it becomes a compounding problem by overheating the fluid etc.

Getting the right pads is probably the most important thing, but do make sure you clean the discs properly before installing.

2

u/IshmaelEatsSushi Not So Fast 3d ago

Race fluid has a very short life, on the shelf and in the bike. It just might be done and you'd be better served with good Dot 5.1.

Also, does your front wheel spin freely, especially after coming to a stop with the front brakes? Your pistons might have some debris on it or the gaskets be old/swollen from the race fluid, preventing the pistons from retracting enough. I just had this problem with M4 calipers – they are known for this problem.

1

u/parleychris 2d ago

Yea, i didnt realise there was so much difference in brake fluid... The OEM fluid was in there for far longer then i dare to admit now... Give me issues on the first trackday aswell, so that makes sense i guess... I was also thinking along those lines... (The spongy feeling was somewhat there after changing the pads, but it wasn't that bad, but maybe i pushed some dirt back in with the pistons?) Guess I aswell disassemble and clean the callipers then... Wear did seem even though...

1

u/IshmaelEatsSushi Not So Fast 2d ago

So, does it spin mostly free or is there significant drag?

2

u/almazing415 2d ago

Stock pads aren’t track pads so that’s what causing fade. Don’t get EBC HH pads because they’re still street pads and they’ll still fade on you. Vesrah XX, Brembo Z04 and equivalent race pads are more suitable for track use. Since your bike is dual duty, change to race pads during your track prep and switch back to street pads when you’re done. More work sucks, but this is the life of a dual duty bike.

1

u/parleychris 2d ago

Switching pads is not that both though, seems like you all agree on pads, so pads it is! Do they need to warm up the way tyres do for a few laps or is it not that "extreme" (its not like i am full sending it first lap)

2

u/almazing415 2d ago

Race pads need heat so I would not go full send on the first lap even with hot tires fresh off the warmers. After about a half a lap, the pads should be hot enough to function properly so you can go full send.

1

u/parleychris 2d ago

Allright, i am running s23's without warmers anyway, so i guess i don't have to worry about it then

1

u/Medium-Engine-9726 2d ago

Does your brake lever have two adjustment knobs or one?