brake lever travels more under track work

[BLOFLY 636]

has anybody noticed when at a track that the brake lever travels more after 3 or 4 really fast laps? would it be because of the heat generated by extreme braking pressure within the calipers? and would fitting stainless steel braided brake lines help to make this less noticeable?
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[california_rookie]

That's what they call 'fade', right? Might it have something to do with the temperature of the brake fluid?
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[G]

[stryker]

I would of theought the brake disks would expand when hot thus restricting brake lever travel...... interesting that.
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Now what?

[Full Bananas]

[G]

The width of the brake disc shouldn't effect it... otherwise it would be much more effected when the pads wore down.

[bath of kylies]

Most likely due to "old" or "contaminated" brake fluid. Best first option would be to change brake fluid as mentioned in previous replies.

When the discs and pads get hot (made more extreme on the track) the brake fluid in the lines gets hot too. Get the fluid hot enough and any water absorbed in it will boil and you end up with small steam bubbles in the lines. These then compress under braking and lead to the brake fade you are experiencing.

As the fluid cools after you have come off the track the small bubbles are either re-absorbed, or I think rise up the lines and "bubble" out at the top into your brake fluid reservoir (someone will no doubt correct me on the last point if it's cr@p ). This is why the fade "goes away" with time.

Fitting braided hoses is a good idea anyway if you are doing track days, as (at least in my experience) they give a much better "feel" when braking.

[mchaggis]

Hrm, this is brake lever travel rather than just crap brakes then?

Further brake lever travel is probably the fluid boiling. You might notice it more due to the discs getting too hot as well.
Your brakes will be crap when they get hot as the coefficient of friction between the pads and disc drops. You will have to put greater pressure on the lever to get the same braking. Cook them too much and you'll cure the pads, whereupon you'll get excessive pad wear and they'll fall away into dust.

(The resin in the pads melts and vapourises, which along with the rest of the dust and debris acts as a lubricant.)

You get geometric changes too, but I'm not sure if they're so much of an issue with bike brakes.

As an aside, why are there so many people who are too blind to notice that they've typed break rather than brake?!
If my bike breaks when I'm expecting it to brake, I would not be impressed. If I break rather than braking, then I expect the bike to get broken too.

Edit: and whilst we're on the subject... Why do so many people seem to be incapable of understanding the difference between brought and bought?
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[RealNinja]

Something that nobody has yet mentioned is that you get less brake fade if you have ceramic backed brake pads.

The ceramic reduces some of the heat created by the friction of the brakes getting to the fluid, and therefore reducing brake fade, or at least postponing it

I discovered that after the first couple of sessions on track days it's worth pumping your brakes when sitting in the pit lane. Something I tend to do anyway now, after a memory lapse following a pad change!
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[mchaggis]

[aqualung1]

agree with the others about brake fluid gets hot, hence the fade,
it could just require a service as said above

stick to good quality replacements when servicing bike if only for occassional track day use.. if on track reguallay then you can go fancy, as on road, most of track stuff brake pads etc do not heat up enough

happy riding
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[jonboy]

[BLOFLY 636]

thanks for all the feedback guys , but I am not sure if I have mentioned that the bike is only 8 months old and has only done 7000km or about 4360 miles, would it still be possible for the bike to have moisture in the lines? I should also note that the lever only travelled excessively after some repeated hard braking that I felt was a little too hard because I swear I could feel the back wheel lifting a little and chattering into some hard right handers , but I shall go and see my local dealer and ask him to check my brake fluid for moisture and see what he can do for me
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[Kickstart]

Hi

At that age it should be OK, but it is well worth bleeding the brakes through.

Fitting braided steel lines might help, but that might well mainly be from having to bleed the brakes properly when fitting them.

Braided lines do expand less than the standard rubber ones, but decent condition rubber ones should be fine.

You can use a higher rated fluid such as DOT 5.1 (not DOT 5 which is silicone based and has a lower boiling point, as well as absorbing air bubbles very easily). When changing brake fluid do not shake the can of fresh fluid as you will get loads of air bubbles.

All the best

Keith
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[california_rookie]

Yeah? Well my brake lever travels wherever it likes at the moment as my front brakes are out. Beat that.
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