Juddering front

Just came back from my first trackday at Magny Cours which was awesome. Bug has definitely bitten!

My 06 blade performed amazingly, and shod in Racetec RRs didn't move an inch on the power/cornering, although I was rough enough in my braking for the rear to frequently end up bouncing/snaking around. That isn't a problem that a slipper clutch or just more sensible braking wouldn't solve, but I was also experiencing some front juddering when hard on the brakes (back straight goes from 170mph down into 45mph hairpin). I presume that's more preload needed on the front - am I right?

 

Whilst I'm not qualified to comment on your front brakes I did have the same problem at the rear on my first track day last week. I found that when downshifting i would let the clutch lever out but pause at the biting point for a split second before releasing fully and it seemed to stop me from juddering along the black stuff for the rest of the day unless i went in too hard then its all on just to stop in time never mind downshifting lol.

There may be better ways as I've only done one track day but this seemed to work for me.

 

Front wheel judder under hard breaking is usually a slightly warped disc or it could be the wheel locking up

 

Wheel bearing is also a very high possibility. I had the same symptoms.

 

Thanks guys.

Wheel bearing is a good call - I previously had front judder which was recently fixed with new front bearings, so it's definitely not that this time. In any event, it is now only when really hard on the brakes, on track, with a sticky tyre. I'm also quite a big bloke which leads me to think the forks are bottoming out and the wheel then skipping along the tarmac fighting for grip - as suggested above.

 

Also check the head bearings if you haven't already.

 

The forks should be easy to identify if they are bottoming out with the simple use of a tie wrap fixed round the fork tube.

Fix tie wrap n push it up towards the fork seal and run the bike and see where the tie wrap ends up,
Oem forks bottom out with about 20mm of tube still showing at very bottom.

 

Thanks all.

Shiny, I have a cable tie around my stanchion but wasn't sure where 'bottom out' was. I reckon I am about 20mm off bottom however so sounds like I was right about what was happening with my forks. It makes sense - most Japanese riders are not 6 foot tall and around 15 stone!

I will wind more preload on. If I do that, will that effectively lift the front of the bike, in which case I should slightly drop the forks through the yokes to compensate?

I appreciate that I do need to get round to setting up my static sag properly...

 

If your forks are bottoming out your sag figures will most likely be too far off and your bike will be sitting nose down anyway so forget about moving forks around in the yokes, try increasing your preload and get your sag figures more into the correct range.
If your close to the far reaches of adjustment in the preload settings you will probably require a higher spring rate in the forks so worth keeping in mind.

One other thing to note how many miles have the forks done?
You should be looking at getting the oil changed around 7500miles mark for road use.