Braking chatter: dampening or fork flex?

Just completed front brake mod (13mm master, braided line, Grimeca caliper, floating disk, Hyde fork brace). Much more better! However, on hard almost-lockup braking, if the wheel hits a bump, I get a "chirt-chirt-chirt-chirt" tire squeal. Is this fork flex? Bad dampening? it doesn't feel like the front end is bouncing.

I have progressive springs and 10w fork oil.

Manxman

that chatter is because the stock suspension is too stiff and so the wheel hops

I second the Lansdowne cartridge upgrade, very easy drop in installation giving full rebound and compression adjustability

+1 on the Lansdowne kit, mine works great!

Remember that there are lots of racers using these forks who brake very hard from very high speed. I do not believe they flex as much as some may think. And flex is definitely not the cause of your problems IMHO.

"that chatter is because the stock suspension is too stiff and so the wheel hops "
and that could be very well caused by the Hyde fork brace

madass140 said:

"that chatter is because the stock suspension is too stiff and so the wheel hops "
and that could be very well caused by the Hyde fork brace

Click to expand...

"too stiff". Do you mean the spring rate is too high? The compression dampening too high?
How does the fork brace affect suspension parameters other than increasing unsprung weight? I thought it just kept the sliders paired up and prevented axle malalignment.

Manxman

"that chatter is because the stock suspension is too stiff and so the wheel hops"
actually 1up3down said that , that wasnt my reply and I dont know how it came as my reply, but I tend to agree.
suspension could be to stiff caused by the Hyde brace if its not set up correctly and it causes the forks to bind , doing the opposite of what its supposed to do, the same result if the head of the axle is to tight in the bottom of the left slider and not allowing the forks to centralize themselves before nipping up the pinch bolt.

Loose and/or worn steering head bearing(s).

This was discussed in a previous thread,maybe someone will find & link it. I contend it's the spindly stanchion tubes flexing and then unloading causing the chatter. JMWO

I know its a bit late responding ,but i have just return from a short stay with the hospital ..anyway i have been reading the old posts .
What i have seen is the amount of wear in these sliders. have bored out one over 1mm and that did not clean up the bore! But that was a old short roadholder .
Only after reaming and over size bush's did a pair of commando forks stop knocking and sticking .
Fitting a huge disc only compounds the problems , when the lower bush is forced under brake pressure into the "hollows" it gets stuck until the shaking releases it free. this force causes over compression for a split second.
By modern standards the original forks are a bit weak, Stand in front of the bike ,grip the wheel between your knees and twist the handle bars ..you will see the fork flex side to side .
At Donnington Stew Tonge showed how the wheel could twist and touch the guard. But in use this is all " the norm" thats what a 50 year old design does.