AMCC ART Day, Saturday 9 November 2013

[nzspokes]

Chucking my bike on the trailer tonight. What tyre pressures should I start out with?

[p.dath]

Chucking my bike on the trailer tonight. What tyre pressures should I start out with?

You usually take 10% to 20% off your "road" pressure when everything is measured cold. Why don't you start by lowering them by 10%.

You need to see how hot the tyres get, and how much the pressure increases by on the track to find out for sure ...

[vinducati]

30 front 30 rear.

[Gremlin]

On the other hand, bearing in mind it's your first track day, you're in Group 1 etc. I'd probably stay with normal road pressures so the bike feels familiar while you learn everything else.

[nzspokes]

Well as the parts supplierd forgot to send my brake pads untill this morning i may be running around auckland tonight looking for pads.

[p.dath]

Well as the parts supplierd forgot to send my brake pads untill this morning i may be running around auckland tonight looking for pads.

Go pick them up from the courier depo ...

[Gremlin]

Well as the parts supplierd forgot to send my brake pads untill this morning i may be running around auckland tonight looking for pads.

I have the Premier pads from the Hamilton stuff we bought...

[nzspokes]

I have the Premier pads from the Hamilton stuff we bought...

Cheers but they have turned up at the shop and the owner is dropping them off for me at 4.30.

Only just heard.

[p.dath]

I have something playing on my mind, and nothing like the wild speculation you get on Kiwibiker.


For the first time at any track day I had an accident. I'm fine, and thanks to frame sliders the bike doesn't look to bad either. It was on the corner officially known by Hampton Downs as T9. It is the left hand hair pin that has a big descent, and the corner before the big sweeper.

I was maybe within 5m of the apex down the bottom of the descent. I had long finished braking (specifically, I was not on the brakes at all), I was sitting in 2nd, and had gentle throttle on. I would estimate I was travelling at 60km/h, certainly not fast for the corner. I had done maybe 3 laps of the session (it was up to about session 3), and both tyres should have been well warm. I use standard street sport touring tyres (Bridgestones BT023's) (as I normally ride on the street, not the track). The tyres were about 12 months old, and had a lot of tread left on them. The tyres were cold inflated to 30/30. I could not see any contamination on the track surface.

And then I lost the front end, and low sided.

I keep replaying it in my mind, as I think it is 90% likely to be rider error. I think I may have just overestimated the grip I had available at the time.


But one thing keeps playing on my mind. When the bike was at rest (in the kitty litter) the marshal and I tried to move the bike further away from the track. We couldn't. The front brake lever was locked on and "tight". We ended up leaving it there till the recovery vehicle came, which was maybe 5 minutes later. When we returned to the motorcycle the front brake lever had play in it again, and seemed to be working fine, and we were able to push it out of the kitty litter ourselves.

The brakes should have been fine. Just two weeks prior I had the bike serviced (no, I am not to going to name anyone, but it was by a well known responsible trustworthy workshop). The bike wasn't due for a service, but because it was the first time it was going to going on the track I decided to have a special one off service done, and included in the service was a full brake fluid flush and replacement, mostly because it was the first session of the season going back on track.

Since the service I had done some street riding, but compared to the track, the usage was very light.

The bit that keeps playing on my mind was how the front brake was locked on when I first checked it in the kitty litter, and appeared to be okay 5 minutes later, and that I had recently had work done on my brakes. The issue with the brake could have been because the bike ended up in the kitty litter and particles got forced where they shouldn't have been. But I keep running through my mind what if the braking system had been accidentally contaminated or compromised. And I find that idea pretty scary.

Prior to this the brakes felt great. They did not feel spongy.

I think before any repair work is done I'm going to ask to have the brake fluid drained and inspected for contamination, just to try and put my mind at rest. I am also going to ask to have the front brakes inspected in general (like the front calipers).


So now I am open to the wild speculation. What do you guys think?

[nzspokes]

Bugger.

I would be checking the fluid level first as it sounds by what your saying the brakes hydro locked. So if over filled the fluid would have had no where to go. If it should have a bladder make sure that there also. If the fluid was contaminated you would have lost lever not gained it.

Much damage?

[nzspokes]

Did you work out if it was the brakes?

[p.dath]

Did you work out if it was the brakes?

Not yet. It is hopefully being looked at today/tomorrow.

[manxkiwi]

Yep sounds suspiciously like an over filled reservoir to me too.

Let us know what the 'official verdict' is.

[Timmeh:P]

I second the overfilled reservoir.

[MarkW]

My thoughts on Phil's crash:

There are only 2 left hand corners at Hampton and the downhill left hander is a proper corner. The first left hander is just a kink. So tyre temperature (lack thereof) may have been a factor still. The corner is a downhill one with a decreasing radius as you come to the end and this does really test front end grip so there may have been a combination coming into effect - a rearwards shift in body position, a counter steer load increase as the corner tightens, an increasing throttle opening and a cooler tyre all combining to give a front end washout.

I do not agree with an over filled reservoir as being the likely cause because if the reservoir was overfilled the problem would have been very apparent on the ride to the track itself or in one of the earlier sessions. Overfilled reservoirs mean that the pads are kept in contact with the disc and so as things get hotter and hotter the problem compounds very quickly - the ride to the circuit is far longer than any of the sessions at the circuit and so the front brakes would have locked on before Phil arrived. Even if they hadn't done so on the ride there unless Phil was barely using his brakes in sessions 1 and 2 and then was hitting them really hard early in session 3 the problem would have been evident in an earlier session. And with Phil in the kitty litter the front brakes would have been glowing with heat.

It is also possible that the jar of the crash caused a calliper piston to stick briefly or a bit of the litter wedged briefly in the front brake lever housing and jammed the lever. This litter was dislodged when the fiddling with the lever occurred.

Contamination is also unlikely in my opinion - again the problem would be very unlikely to manifest itself by making a brake suddenly come on - it is rather more likely to make the brakes fail rather than work excessively well.

So, sorry Phil,

Pilot error.