Brake leaver going soft on track...

[Bizzle]

Howdy,
An interesting one to run past you.
GSXR600 K1 track bike with unknown pads, braided lined and a stock master cylinder running brand new AP Dot 4 race fluid.

When starting off in the morning or at the beginning of the sessions the lever is rock solid. Towards the end of a session the lever pull gets closer and closer to the bar until it's a bit comical. It happens sooner and with more severity as the day goes on.

Immediately i thought it's boiling the fluid - so i swapped it out for the new fresh AP stuff which improved a little bit - but the problem still persists. I know how to bleed brakes properly so there is no air in the system 100%. Usually when you boil the fluid the sponginess in the leaver persists but by the time 40mins passes and i'm out for the next session it's solid again.

I was talking with my friend Si (MrKippling on here) who suggested that i should swap out the pads for something that doesn't get quite as hot. I was reading good things about the performance friction ones (£100 a set!!)

Anybody got any thoughts?

Cheers

[Bizzle]

The DOT rating of the fluid has little to nothing to do with it's quality. Most higher spec race fluid is actually dot four rather than 5.1. The fluid I swapped it to was AP600 with a 312deg dry boiling point - i'd be surprised if there was something wrong with the fluid.

BikersNemesis:
Not that i know of - however, the bike is Craig Jones's old Roundstone Racing Superstock bike that he won the 2004 championship on. So if it was good enough for him, it'll be good enough for me - unless it's degraded over the years but that doesn't seem to marry.

[Bizzle]

I was actually properly sceptical about the bike - you have seen it Stu. We met briefly at Cadwell a few weeks ago. However, i have done a fair bit of research and everything indicates that it genuinely is 'the' bike. There is some footage of it on what's left of the roundstone website. I'm 99.9% sure it's the real deal. It's even signed by Craig.

I'll give swapping out the pads a go + try to change my braking habits. It'll be interesting to see what pads are actually in it.

Cheers

Chris

[Bizzle]

So it's weird.
The brake 'effort' (so to speak) doesn't actually drop off. It still seems to stop well, it's just that the lever get's progressively closer and closer to the bar until i say 'whoa - that's enough' which usually happens at towards the end of one of the afternoon sessions.

[Bizzle]

Chipchap,
No - fluid doesn't drop at all. It's not loosing fluid (but good thought!)

Pluke: I don't mean to push back - but i have trouble believing that this is fluid related.

AP Racing 600 Brake Fluid (what i run)

- ‘Typical’ New Dry Boiling Point in excess of - 312°C
- ‘Wet’ E.R. (Equilibrium Reflux) Boiling Point - 204°C

Castrol SRF

- New Dry Boiling Point - 320°C
- ‘Wet’ E.R. (Equilibrium Reflux) Boiling Point - 270°C

As this brake fluid is literally brand spanking new, from a sealed container, poured and bled into the brake system it's not had the chance to absorb much (if any) water from the air. Subsequently the brake fluid should be near identical in spec.

[Bizzle]

Okaydokey,
Thanks all. I can't say i'm a huge fan of the idea of putting standard Suzuki pads in it. I'm told the more recent Yamaha pads are actually pretty damn good though.

I have ordered up a set of those SBK Duel Carbon's and they are getting here this week. There is some talk of us doing Rockingham next weekend so i'll let you know if it makes a difference.

Cheers

Chris

[Bizzle]

Suzuki, most definitely. Developing a pad that has to perform as an exceptional compromise for all types of riders, in all types of conditions. I'm not saying they are bad - i'm saying that knowing that, i personally would rather put in a different pad. :-)

[Bizzle]

Hello Again, so an update on this:
I pulled the pads out of the bike to find that there was a very old set of Brembo pads in there.




Surprisingly the callipers were in excellent condition, clean and mechanically perfect with everything moving freely. So i dropped in a set of SBC Duel Carbon pads and slotted them back on the bike. A few days later we took the bike to Rockingham. SBC say you need to take a few laps to bed them in properly and you need to warm them up on your out lap so after a few laps bedding in I started to give it some beans.

What a difference.

100% more feel, significantly more braking power and after an entire day of thrashing it round Rockingham not a single bit of sponginess in the lever.

Great success.