Brake leaver going soft on track...

Brake leaver going soft on track...

Author
Discussion

Bizzle

Original Poster:

544 posts

200 months

Friday 4th April 2014
quotequote all
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


theshrew

6,008 posts

183 months

Friday 4th April 2014
quotequote all
Boiling your fluid by the sound of it. Especially if you changed it with the same stuff.

Dot 4 is road use fluid. Get a proper racing spec fluid I imagine your will solve your problem. Loads on here race / track will be able to advise what to go for.

Racing pads will cope with higher temp better and probably give you more stopping power in turn will create a bigger issue. Not a bad idea to get some though.



Edited by theshrew on Friday 4th April 20:07


Edited by theshrew on Friday 4th April 20:08

Biker's Nemesis

38,534 posts

207 months

Friday 4th April 2014
quotequote all
Were K1's known for having a piss poor M/C?

Bizzle

Original Poster:

544 posts

200 months

Friday 4th April 2014
quotequote all
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.




muffinmenace

1,029 posts

187 months

Friday 4th April 2014
quotequote all
Bizzle said:
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.
I'm a newbie with bikes but with cars I think the top spec fluid is still Castrol SRF which has the highest dry and more importantly wet boiling point of any other fluid on the market. It like all high temp stuff is DOT 4 so should be reet. If it's still boiling with that I'd say you're binding somewhere.

StuB

6,695 posts

238 months

Friday 4th April 2014
quotequote all
Sounds odd based on what you've said, but would suggest you make sure all pistons move freely & then I'd be inclined to change pads. Guessing you have standard Tockico 4 pots? They & the SRAD 6 pots are prone to getting sticky, which is worse with heat.

Beware of ex-him/her/whomever race bikes as unless for example Guy Martin marks the engines he works on so you can actually see & check with your own eyes, it could easy be a stock-ish road bike with race fairings & a great sellers story of BSB glories past. Could just be me being a sceptical old barsteward though.

I raced with SBS Dual Carbon, with Motul RF600 fluid. Millie stopped on a fookin sixpence.

WaferThinHam

1,680 posts

129 months

Friday 4th April 2014
quotequote all
SBS dual carbon are awesome pads.

Lincsblokey

3,175 posts

154 months

Friday 4th April 2014
quotequote all
Brake fluid and an old M/C. It'll be in need of a service at that age too.

WRT brake fluid, i don't know a single lad that races on anything less than five. Service the MC, flush through with 5....job done

Mike600F

1,049 posts

155 months

Friday 4th April 2014
quotequote all
I get a similar thing, loon said it was more likely ba braking technique; trailing the brakes too much into the bends putting more heat into the fluid than braking really hard for a shorter time.

I plan to apply bravery at the next trackday and see if it sorts the problem...

theshrew

6,008 posts

183 months

Friday 4th April 2014
quotequote all
Tbh I always thought the Dot part determined the boiling point ya learn something everyday. If you have real high spec temp spec stuff then that should be fine. Was it a new bottle ? If it was old then that could cause a issue.

Seems like a strange problem especially as it's only doing it when it gets hot.

Have you bled it while it's hot just to see if any air comes out ?
Check brake lines sometimes they can bulge giving a spongy feel however you have braided and it's only when hot so that's unlikely but you never know.
Check everything if free.

Craig Jones went to the same school as me :-)



Bizzle

Original Poster:

544 posts

200 months

Friday 4th April 2014
quotequote all
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

StuB

6,695 posts

238 months

Friday 4th April 2014
quotequote all
Oops, sorry, forgot your name.

Brakes need to deal with heat, they convert energy from rotation to heat, so fix the issue, don't ride around it by riding different.

MC service also worth doing.

Fleegle

16,688 posts

175 months

Friday 4th April 2014
quotequote all
I've never needed to use 5.1 and I'm not shy with the brakes. Never had a problem with 4.
Had problems with shyte m/c's and knackered brake hoses though which give brake fade of a sort.
Worst bike I experienced this on was a CBR which made me commit like I'd never before approaching Gerrards.

Bizzle

Original Poster:

544 posts

200 months

Saturday 5th April 2014
quotequote all
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.


Chipchap

2,580 posts

196 months

Saturday 5th April 2014
quotequote all
OP Does the fluid level drop during the day ? Sounds as though you may have a slight leak that is pulling a bit off air back in.

PLuKE

283 posts

189 months

Saturday 5th April 2014
quotequote all
Brake fluid draws in moisture over time.

Soft brake lever when on track is the fluid can't cope with the heat.

Buy some Castrol SRF, and bleed the brakes and take your time. Try this first, it won't be the pads that are causing a soft lever.

If you are interested in better/new brake pads, SBS dual carbon are very good, just give them a lap to warm up. Or SBS race sintered are treat to! and work from the word go.

Luke

Bizzle

Original Poster:

544 posts

200 months

Saturday 5th April 2014
quotequote all
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.

Biker's Nemesis

38,534 posts

207 months

Saturday 5th April 2014
quotequote all
Ok it's your 14 year old M/C or brake lines pistons or all 3

Hooli

32,278 posts

199 months

Saturday 5th April 2014
quotequote all
I'd start with the pads. I've known several sets go off with age, they just seem to go hard & give no braking.

Mike600F

1,049 posts

155 months

Saturday 5th April 2014
quotequote all
Hooli said:
I'd start with the pads. I've known several sets go off with age, they just seem to go hard & give no braking.
Spoke with the mechanic at my local bike place today on this topic whilst having a new rear fitted (mmmmmm new rubber...).
He reckons it's the pads; to function well brakes need heat, but too much heat causes fade; he advised getting track only pads for track use that are heavily sintered as they perform better at high temps so you won't get the fade we're feeling. He mentioned a brand called "frodo" (he has a thick welsh accent, and I have watch lord of the rings recently so it could be something that sounds like frodo.).

Anyway, he was adamant to that there was now way I was boiling the fluid and that it must be the pads. So, as Hooli said, I'd start there. Let me know if you find some good ones that I should try.